EV Digest 5998
Topics covered in this issue include:
1) RE: Bad aux battery affects Voltage Sag?
by Patrick Clarke <[EMAIL PROTECTED]>
2) RE: GoWheel.com and Lithium
by "Mark Fowler" <[EMAIL PROTECTED]>
3) Re: Lighter Porsche 914
by GWMobile <[EMAIL PROTECTED]>
4) RE: Bad aux battery affects Voltage Sag?
by "Roger Stockton" <[EMAIL PROTECTED]>
5) Re: What is the future of Li BMS?
by Jack Murray <[EMAIL PROTECTED]>
6) RE: Bad aux battery affects Voltage Sag?
by Patrick Clarke <[EMAIL PROTECTED]>
7) Re: Cruise control?
by Mark Ward <[EMAIL PROTECTED]>
8) RE: lee's emeter companion?
by Cor van de Water <[EMAIL PROTECTED]>
9) RE: Bad aux battery affects Voltage Sag?
by Cor van de Water <[EMAIL PROTECTED]>
10) RE: Bad aux battery affects Voltage Sag?
by "Roger Stockton" <[EMAIL PROTECTED]>
11) Re: Comparator circuit 1.0 for nicad pack monitoring
by "Mike Phillips" <[EMAIL PROTECTED]>
12) Re: Bad aux battery affects Voltage Sag?
by "Phil Marino" <[EMAIL PROTECTED]>
13) RE: Bad aux battery affects Voltage Sag?
by Cor van de Water <[EMAIL PROTECTED]>
--- Begin Message ---Roger Stockton responded:The main pack was sitting at 128.2.This is low for a fully charged 120V pack of AGMs; mine will still be sitting at 130V or better after *months* of inactivity.----I have the impression that our pack may be losing a small amount sitting still - say a tenth of a volt a day or so. Is this indicative of a bad battery?With the DC/DC on, but the car otherwise off (no load on the traction pack other than the DC/DC), check what the E-Meter indicates the load current to be.-----With the aux being dead, when the DC/DC come's on the E-meter's reading jumps around in the 0-.6 amp range. I've been wondering how accurate the meter is if it isn't reporting a steady draw - it seems to even momentarily leap into the positive range when the car is sitting still, sometimes. Is it possible for this to actually happen?I think you've got something far more serious wrong than your DC/DC working overtime ;^> Your pack is over 2x the capacity of mine, and with about the same Ah removed from my pack, the lowest I've ever seen it sag is to about 90V @ 400-450A. Either you have one or more batteries 'bad', or there may be something lacking about the way you are charging your batteries. Can you provide details of how you are charging them?------Well, crapola. I really wanted to buck the trend of the newby murdering the batteries, but oh well. :-(I've been at pains to carefully follow the charging instructions of the converter, or rather the upgrader of the previous conversion. There's an on-board charger with a "high" and "low" setting. I start it on low, wait a few minutes and then observe both the amps going in (usually around 9-10 to start) and the amphrs used. I divide the latter by the former and set the timer for the result, adding two hours. I then check the amps on the emeter, and assuming it's <4, I flick the charger to high for a half hour or so until the pack is at 150 or so. I was told not to leave it on high for more than a half hour or so - and I haven't.As to the closeness of the voltages, the closer the better, but go ahead and measure them (ideally at the end of discharge after letting them sit no-load for 30min or so to endure the voltages have stabilised), and post the values here for comment. Probably worth including notes indicating which batteries are in which box, and if that box is enclosed or open, etc., since temperature differences between batteries in open racks under the hood and those in closed boxes under the rear seat, etc. can affect the voltage spread-------At the end of a particular discharge or just after having been driven a bit? Just sitting or under load as Cor suggested? I can do this, and will post the data when I have it.A thought - before I go buy a hundred feet of wire, is there some kind of affordable battery tester that I could purchase that would be of particular use with EVs and make diagnostics simpler & surer (my intention - despite current frustrations - is for the long haul.. and this won't be our last EV!) - or will a roll of wire really be all I need? Noting of course, that whatever piece of equipment beyond that could be too expensive to be feasible for me..Thanks again! - Patrick
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--- Begin Message ---Look what I found... http://www.gowheel.com/Batteries/PricesDoc.html - (expected ship date Nov. 14, 2006) Contact us at 949-497-3600 or [EMAIL PROTECTED] or [HERE] We will soon be offering Electric Vehicle Battery Packs: GoWheel-9192: 1.475kwh @79.2 volts @ 560 amps, with BMS, Battery Box and Cooling System Swap-out Battery Pack Modules for Electric Vehicles available with any type connector or placement List: $7,500.00 Sale: $6,750.00 Dealer: $5,625.00 All prices + Shipping & Handling (approx. $29 FEDX Ground USA) Weight approx. 37.21 pounds Configured Form Factors: Weight approx. 33.1 pounds + packing materials 10.5 x 8.3 x 6.2 inches with standard posts, or marine posts, or Anderson Connectors. Battery Packs are intended to be "Quick-Switch" ready for slide-in/out of the battery/BMS (in/out of the included Battery Box installed in vehicle). Packs can be grouped in series or parallel, but are individually complete. Boxes are watertight up to top edge after closing side (slide-out) door. Top contains low voltage cooling fans and are water sealed to upward facing tubes (like 2 radiator hoses) attachable to ram or outside air in/out ducts. Two fans included, one forcing high flow in, and one fan forcing air out, temperature activated. ----------------------------------------------- OK, so they are selling a 80v 18Ah pack that will deliver 560A (30C) weighing 33lbs (14kg) for between $5,625 and $6,750 depending on whether you can convince them you are a dealer or not. So for a 160v 90Ah (similar to what's in my car) I'd be looking at 10 packs for US$56K (I'd become the Aus dealer :-) weighing 140kg. So it would be capable of maxing out a LV-Z2K (say 150v x 2000A) giving 300KW to the motor. Ooh baby... I SO hope this is real... Mark > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Rich Rudman > Sent: Wednesday, 11 October 2006 2:58 AM > To: [email protected] > Subject: Re: GoWheel.com and Lithium > > > Umm I have answers.. > but can not say. > > Lets see how well they do thier job. > > Madman > > ----- Original Message ----- > From: "Don Cameron" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Tuesday, October 10, 2006 4:52 AM > Subject: GoWheel.com and Lithium > > > > I just got spammed by GoWheel.com who claim that they will > be selling EV > > sized batteries from A123 with BMS within a couple of weeks. > > > > They gave no capacity specs or prices in their email nor on > their web > site. > > > > > > So A123 is really available? At what cost? Maybe someone > in more of an > OEM > > position can get quantities (Victor?) I wonder what kind of BMS? > > > > > > > > > > > > Don Cameron, Victoria, BC, Canada > > > > see the New Beetle EV project www.cameronsoftware.com/ev > > > > > >
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--- Begin Message --- A mazda miata is a very light convertible that has bolt on wheel fenders.It handles better than the 914. I have had both although both are good handling cars.Miatas can be purchased very cheaply used.(Although you won't need it their motors last for ever because they have so large cooling fluid pathways and sprayed oil cooling as well.)Front engine mounting for the miata might be easier than mid engine mounting for 914 but the 914 might have more room for matteries since it has both a front and rear trunk because of the mid engine design.Probalby can find a rust free miata much easier than a 914 since the original coating on a miata were much advanced over the 1970's 914's.Miata is a more modern car too 1990 and later with a large aftermarket and airconditioning installed. Few 914s had ac.Both have four wheel disc brakes. On Tue, 10 Oct 2006 11:41 am, Steve Lacy wrote:The 914 is a unibody design, so its much more difficult to get fiberglass"panels" that bolt-on. As I'm sure you know, fiber/carbon front & reartrunk lids are the easiest thing to find, but they're expensive and aren'tgoing to save you the 200 lbs that you're looking for. Front and rear fenders will save a few pounds as well. Visit 914club.com and see what the "race" guys are doing, since they have the same weight problems. The Ghia (I believe) is a pan and bolt on body design (like the beetle)and if so, you should be able to find bolt-on fiberglass versions of mostof the panels, just like you can on the beetle, and have a significant weight savings if you're willing to spend the $$$. BTW, even if you could save 200 lbs, thats going to be less than 10% of the total weight of the car... Lightweight and EV's don't really mix. Steve On Tue, October 10, 2006 5:28 am, Mark E. Hanson wrote:Hi, I was curious from the Porsche conversion guru's how to lighten up a Porsche 914. I'm looking at buying one and it has the usual belly panrust so I'll need to replace that probably from auto atlanitc.com. Does anyone have recommendations on fiberglas etc body parts replacements thatwould make it lighter. It weighs 2100lbs start weight and the Ghia is 1900 lbs but the Porsche looks like a more fun car with the removeable roof so I'll probably buy that tomorrow. Thanks, Mark ---------------------------------How low will we go? Check out Yahoo! Messenger’s low PC-to-Phone callrates.www.GlobalBoiling.com for daily updated facts about hurricanes, globalwarming and the melting poles.www.ElectricQuakes.com daily solar and earthquake data.
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--- Begin Message ---Patrick Clarke wrote: > Cor van de Water kindly wrote: > > > This means about 250A for 15 min or 62Ah at about 2C rate. 250A * 0.25hr = 62.5Ah, but this is the 4C rate. > > Now that shold give you more than 11 miles / 27 Ah. > > How much more should it give us, given that we've been using about > 250WattHrs/mile? >From the specs you posted, it sounds like your batteries are quite similar to (or are) the MR12-490s: <http://www.cdstandbypower.com/products/batteries/vrla/pdf/mr12_490.pdf> These are spec'd to have a capacity of 90.3Ah at the 1hr rate, and 106.4Ah at the 2hr rate. At a constant power discharge, they are spec'd at 188W/cell for a 1hr discharge; you have 60 cells in your pack, so this is an available capacity of 11.28kWh if you discharge the pack fully in 1hr. If you consume 250Wh/mi, this implies a drop dead range of about 45mi, driving for 1hr continuously. > Also, how much degradation should we expect from cooler > temps, dipping into the 40s/50s at night for an ungaraged car? I think the Hawker literature I quoted in an earlier response suggested about 15% loss with a drop down to around 32F. > It was after charging. During charging, I usually go to 150 and then > another 15-30 minutes. I suspect you are chronically undercharging the batteries. 150V (15V/battery) is a bit higher than C&D's 14.4-14.8V recommnedation, however their voltage is quoted for 77F and if your batteries are sitting near 32F it would be about right. The question is whether or not you are putting enough energy back into the pack when you terminate the charge 15-30min after hitting 150V. Typically, you would charge to your set votlage (e.g. 150V), then hold this voltage until the current tapers to 1-2% of the battery's Ah capacity (e.g. 1-3A for your batteries). At this point, you should have returned roughly 100% of the energy that was removed from the batteries, but have not put any additional energy in to ensure that all batteries in the string are fully charged and kept in balance with the others. Typically you need to put in an additional 5-10%. If you terminate the charge early, your batteries will drift out of balance over time, until one or more of them is at a significantly lower state of charge (capacity) than the others. This/these battery(ies) are being left only partially charged, and will sulphate, which increases their internal resistance and will show up as greater voltage sag even when the pack is fully charged. What sort of current do you see on the E-Meter just before you terminate the charge? What charge efficiency factor (CEF) is the E-Meter using, and what does its Ah display indicate when you finish charging? > > The easiest way is to take a wire of several tens of feet, > > preferably 100 and connect that across the 12V battery you > > are measuring and see the voltage drop. This may be easy, but it may also be dangerous. The C&D MR12-490s have a short circuit current rating of 5000A; connecting a few milli-ohms of wire directly across one might not be the safest idea. The no-load voltages at the end of discharge should give some idea of the SOC (and therefore capacity) spread, and simply turning on the heater to apply perhaps a 10A load will make the spread even more obvious. A high-current load test like this will help identify batteries with excessive internal resistance, but I would suggest picking up an inexpensive carbon-pile type load tester as is commonly used for testing the cranking ability of an SLI battery as a less exciting way of testing should you want to do such a test. ;^> > I don't suppose the fall temps could account > for any of this sagging behavior (he asked hopefully)? Sure it could, and probably does, but only for some of it. It is pretty certain that the cooler temps are not the only factor at play here. Cheers, Roger.
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--- Begin Message --- I'm very familiar with NiMH, not so much with Lithium, and in particular I'm looking at $6 cells, so the cost to manage them can't be too much or its not a good strategy. I agree if you can increase life significantly the added cost would be worth it, I'd want to see some real data to back it up, double the life seems like a big stretch, maybe if the bad cells don't get replaced a double might be possible, but that is somewhat trickery by comparing to a worst case.In any case, ICE's have to change their oil every few months, maybe we can get Jiffy Lube to change their name to Jiffy Cell ? (oh maybe you don't get joke, Jiffy Lube in USA is a drive-through oil change service :)Jack Jukka Järvinen wrote:You are partilly right here.But the main point is that doubling the weakest cell lifetime with less cost than buying a new set of "weak cells" you are getting noticeable benefits. (since you after all will have more and more failing cells after cell replacements by straining the next "weakest link" more).For hobbyist it's perhaps ok to tinker with the pack but for average Jane it's just too much to pop up the hood once a month to replace bad cell.Since most of the other parts of the EV will have long lifetime and service free life why should battery be any different ?Small EV manufacturers will not be able to enable extencive service network as great unwilling car OEMs can. So we should have as service free system as possible.In theory Lithium cells will work very long time without any service. In real life we need to babysit these puppies well so they push their best for us for much longer.And as I said earlier.. It will not be that expencive to make "BMS" or BMS in quantities. It can be less than $10 per 200 Ah cell. So is $210 for 200 ah 3,6 V cell too much ?-Jukka Jack Murray kirjoitti:Jukka, interesting comments. But why not just let the bad cell fail, and then replace it? It does need to be identified, that is critical, but might be a lot more effective to do that than go to a lot of trouble and expense to keep all the batteries equal. just a thought.Jack Jukka Järvinen wrote:The most wrong way to manage Lion cells is to cure symptoms. The cells behaviour can be predicted easily as long you know the surroindings and enviromental conditions.Rarely cells fail just by using them. You can easliy see the potentially failing cell by measuring it before putting it evne in the pack. I could say that 98% of all failed cells I have had have resigned from their post due misuse. At the moment my experience is limited to a bit over 1 000 000 Ahs in total of used and tested lithium cells. (Co,Mn,Fe)Most wrong way is to find the balance with voltage only. At least with the cells I have used. Pack is badly out of balance if you charge all cells to 100% SOC and start using them from there. Weakest link will fail first and much sooner thant you expect. If you start bypassing the current over the cells you will need heavy and perhaps even expencive way to do it.Voltage is a good reference but not only source of SOH information. Track current, temperature and history data and it will work.And now someone thinks it will be expencive. It can if not done correctly.Lets say you get the double mileage with same pack of cells with BMS. Why ?Without it the weakest link will use most highest individual DOD in the pack. So it has lowest cycllic life too. Best cells have less and less DOD in every cycle since their rate of death is much lower. There will be 200 to 300 % difference in the lifetimes. With certain conditions even more.By adjusting the operational capacity window parameters you can choose the rate of death. Higher cell voltages in end of charge fastens the electrolyte dissolving. Also using heat to lower the impedance during charging you can adjust the lifetime of the cells.This is where I have the border between "BMS" (voltage limitations with tempsensors) and BMS (historical database to define lifetime trends and capacity based balancing to match the cyclic and electrolyte lifetime)Now the 10-20% added price on the plain Lithium cells has nicely been justified by the doubled lifetime. That's the cost of BMS today.If we would live in perfect world and all cells would be identical and electrolyte would not be damaged by overcharging, all extra energy put to cell would just transform to cold air or light or cosmic radiation.. We would be able to make briefcases with 300 kWh energy...There are pending patents on the issues mentioned up here earlier and when they are all public anyone with non-commercial activities can find their ways to implement it.I can see 30 kWh Lion packs with all necesary auxiliary devices (3200W Chargers, computers, touch screens, controller boards for pedals and contactors, cell electronics) with less than 15000 USD in near future. VERY doable. When all gets to it's place you can even half that price.So what I do think about BMS over all (OEM world)... In future there will not be a BMS sold separately.It integrates to cell structures. OEM type manufacturing of the technology is already existing. The "BMS" makers will still be there and doing their thing. From there they do the very important work to test the theories and existing technology. They do not eat anything without chewing it throughly.There are still at least 500 Lithium battery manufacturers world wide. They sell to anyone they can. Small players will vanish or stay in small markets. Big players buy all potential technology they see and it evolves from there as any other industry.Just my personal opinion... -Jukka Mark Fowler kirjoitti:Hi all, John's and Victor's Li-BMS systems monitor the voltage and bleed off excess charge current. They attach (in parallel) to an already connected battery string. The circuit boards in these links actually connect the batteries into a series string. All current runs through the circuit itself, allowing the circuit to monitor the current as well as voltage, and to disconnect the batteries in fault situations.This is fine for relatively low currents (like in R/C models or bikes orscooters) but doesn't scale up too easily without redesigning how the whole thing works (i.e. where the current flows). These systems are cheap because of mass production. (I wonder how big the R/C market is in terms of total KWh of batteries compared to the EV market...) There are chips like http://www.maxim-ic.com/quick_view2.cfm/qv_pk/2931 that do the bulk of the work for you - just wrap a circuit around them to plug everything in to. Once again - the problem is that these chips expect the current to be flowing through them to do their job, so they only handle low currents. I'm sure there's a way of building a circuit based on such a chip that used a current divider so that the chip only saw a tiny fraction of the real current, enabling it to handle EV currents and still give useful voltage info and some overcharge regulation (through another heat-sunk part of the circuit). (I'm an electronics noob, so don't ask me how to do it :-) Mark-----Original Message-----From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Don CameronSent: Tuesday, 10 October 2006 1:43 PM To: [email protected] Subject: RE: What is the future of Li BMS? We already have people on this list developing lithium BMS for higheramperage EV needs today. Victor should have something out soon. Also, Ithink John L has or is developing something.I sure like these little modules, at $45 for the 10 cell unit, needing 9 units for 312V, approx $500 for BMS is pretty good. Too bad the max currentdraw is only 27A.I wonder, it the circuit can be modified easily to handle 300A or even1000A max draw? Don Cameron, Victoria, BC, Canadasee the New Beetle EV project www.cameronsoftware.com/ev-----Original Message-----From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] OnBehalf Of Ryan Stotts Sent: October 9, 2006 7:49 PM To: EVDL Subject: What is the future of Li BMS?Look at these products and based on what you see, what do you foresee on the future price for items such as this and also, the reality and likelihood ofus owning products like this? Is THIS the beginnings of an off the shelf universal BMS system? http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=911 http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=908 http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=912 http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=910 http://www.all-battery.com/index.asp?PageAction=VIEWPROD&ProdID=909Where do we go from here? What is to be done next? Do items like this doanything for us; or are we no further along now then we were?If this item is nothing; then what will be something and when will that beand what will it be?I see a little PCB and silicon in those pics. How is the imagined BMS inyour head different then these? How is it better? What does it dodifferent? How much does it cost and is it cheaper? How will a BMS ever be cheaper? What components are currently not available now that need to be? How will any prices go down? You know what component prices are. Haveprices for any components ever gone down? When and how much?Is BMS a reality or a farce? Will or will not happen in our lifetimes?
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--- Begin Message ---Roger Stockton imparted all sorts of groovy information, including:I suspect you are chronically undercharging the batteries. 150V (15V/battery) is a bit higher than C&D's 14.4-14.8V recommnedation, however their voltage is quoted for 77F and if your batteries are sitting near 32F it would be about right.------- We're in Seattle, so the batteries aren't getting anywhere near freezing - at least yet. It's been in the 60's during the days dropping into the 40's at night (just in case it matters).The question is whether or not you are putting enough energy back into the pack when you terminate the charge 15-30min after hitting 150V. Typically, you would charge to your set votlage (e.g. 150V), then hold this voltage until the current tapers to 1-2% of the battery's Ah capacity (e.g. 1-3A for your batteries). At this point, you should have returned roughly 100% of the energy that was removed from the batteries, but have not put any additional energy in to ensure that all batteries in the string are fully charged and kept in balance with the others. Typically you need to put in an additional 5-10%.-------Thank you for the great info - between you, Cor & Roland, I feel like I'm getting somewhere! Slowly - but that's MY fault, and I appreciate your patience.Anyway, I think that by the time the timer cuts off, the current is down to 1-3 amps, more likely on the low end, say 1-2 amps. How do I put in an additional 5-10%, though? Just leave it on longer - if so, how long? Won't the pack voltage be raised too high, though?How should I adjust my charging regime - in general, and accounting for temperature variations?What sort of current do you see on the E-Meter just before you terminate the charge? What charge efficiency factor (CEF) is the E-Meter using, and what does its Ah display indicate when you finish charging?------My memory is it's down to a couple of amps or so. I don't know what a CEF is, but the Ah display is usually zero or slightly positive.Thank you very much for the info, as well as the warning regarding shorting currents. I think I may prefer to leave the more "exciting" testing to folks like the esteemed Mr Wayland & Co. I am endeavouring NOT to let the Magic Smoke out of any of my EV components, currently. Ar-ar.Thanks again, Patrick (who hopes that some of this process may prove beneficial to other newbies, and apologizes for the boredom if not)
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--- Begin Message ---On most cars the speed is sensed of the transmission. In my case I am using the original throttle body with the electric cruise control cable,throttle position sensor, etc., so in theory it should work the same. My transmission is automatic, but the same should apply to any newer transmissons that have speed sensing on them. If your car uses a computer to run the cruise system, you will have to retain that, of course. Mark Ward St. Charles, MO 95 Saab 900SE "Saabrina" www.saabrina.blogspot.com ---- Bill Dennis <[EMAIL PROTECTED]> wrote: > > What about a cars original cruise control? > > I haven't thought this through deeply, but wouldn't the car's original > cruise control have trouble slowing down the car when it needed to? > When the pedal is let up on an ICE car, engine breaking decreases the > vehicle's speed. But with an electric motor, the car wouldn't slow down > much at all. So when the car was on a slight downhill slope, for > example, I'd think it would pick up velocity and increase beyond the > desired speed. Seems like you'd need some type of mind regen to slow > down the car, like kicking in the original alternator and charging the > 12V battery with it. > > Bill Dennis
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--- Begin Message ---I am hesitating between using a dedicated E-meter (or Lee's replacement) or displaying and integrating the digital (serial) output from my controller in a palmtop that I stick on the dash. My motor controller can be programmed to spit out - volts - amps - temp - RPM in one line of serial data, every second. Integrating this over time will yield Ah and kWh with very little calculations, besides being able to display controller temp and speed (So I essentially do not need the analog speedometer and I can put the palmtop in this place on the dash, I can even display miles driven by using RPM and converting to distance. The display of my S10 is essentially unused besides the speedo, ODO and the trip meter, as the the only other meters are a temp indication with is stuck at zero and two voltmeters, one attempts to indicate pack SOC but is very unreliable at that and the other is aux battery voltage. By placing a palmtop non-permanently over the position of the Speedo and displaying the calculated speed on the palmtop screen (RPM / 125), plus: - actual controller temp - actual pack voltage and current - actual motor RPMs - calculated Ah out of the pack since charge - calculated kWh out of the pack since charge - calculated miles driven since charge Reason I know speed = RPM / 125 is that the motor is electronically limited at 9000 RPM / 72 MPH HOWEVER, all this requires some programming and debug time and if something is scarce right now, it's my time. So - if Lee has a Beta-test to run, I'm available to help provide feedback! In the mean time I will continue logging the serial data on my laptop, so I have a database of trips that I made to compare against, just need to make a parser to provide the data to Excel and make it visible, easily comparable and so on. Cor van de Water Systems Architect Email: [EMAIL PROTECTED] Private: http://www.cvandewater.com Skype: cor_van_de_water IM: [EMAIL PROTECTED] Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925 Fax: +1 408 731 3675 eFAX: +31-87-784-1130 Proxim Wireless Networks eFAX: +1-610-423-5743 Take your network further http://www.proxim.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Mike Phillips Sent: Tuesday, October 10, 2006 11:50 AM To: Lee Hart Subject: Re: lee's emeter companion? So it can replace the Emeter entirely. That's great. Sign me up for Beta testing. Mike --- In [EMAIL PROTECTED], Lee Hart <[EMAIL PROTECTED]> wrote: > > Mike Phillips wrote: > > Do we have to have the rs232 option to use your companion? > > Yes. However, the point of this project (companion, micro, and display > boards), is to replace the companion with an A/D converter board. The > micro board would be programmed to do the same thing as the E-meter, so > you get the same functionality, but at a lower cost and more > versatility. I suspec the E-meter is just going to "go away" sometime > soon, because it doesn't fit in with Xantrex's marketing plans. > -- > Ring the bells that still can ring > Forget the perfect offering > There is a crack in everything > That's how the light gets in -- Leonard Cohen > -- > Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net >
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--- Begin Message ---Patrick, How did you measure 250Wh/mi? AC power in at the wall outlet or DC power into the pack or DC power out of the pack? Anyway: 250Wh/mi is a little over 2 Ah/mi at 120V With my quick guesstimate of 62 Ah this should give you about 30 mi max range until 1.67 V per cell, so near dead. When temps go below freezing you should try to use not more than 1/2 summer range unless you can monitor your batteries closely OR you build battery heaters (and an insulated box) to keep them warm as long as they are plugged in, then during driving they should still be at summer temps without range impact. Since you never took it more than 20 mi / 45 Ah (was this during warmer weather?) this should be no problem, your charging seems to be OK as well and the only other moment you could have affected the quality from your pack is when you describe that you drew the pack low with the DC/DC. How low was that? You must have a problem with one or more batteries in your pack, as even the specified 475W per cell draw would end the 62Ah discharge when the pack reaches 1.67 Vpc x 6 x 10 = 100V for your 120V pack. 60V means there is something really out of whack. When you measure after driving, you will find stinkers easier than when freshly charged up. I have 3 batteries that when I connect a 15V charger, they initially draw 0 Amps, slowly ramping up until they take max current. I have replacement batteries sitting next to the truck, I only need to make regulators before I put 3 fresh batteries in the string with 23 almost 1 year old ones that have seen 4500 miles. The 100 ft wire can be an extension cord - that should give you around the 20 to 30 A discharge current, more if you parallel the wires in the cord, less if you put wires in series (connect the two prongs together and connect the two socket holes to your battery terminals) Watch out for too long loading or you get a 'stench' cord. Cor van de Water Systems Architect Email: [EMAIL PROTECTED] Private: http://www.cvandewater.com Skype: cor_van_de_water IM: [EMAIL PROTECTED] Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925 Fax: +1 408 731 3675 eFAX: +31-87-784-1130 Proxim Wireless Networks eFAX: +1-610-423-5743 Take your network further http://www.proxim.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Patrick Clarke Sent: Tuesday, October 10, 2006 11:34 AM To: EV List Subject: RE: Bad aux battery affects Voltage Sag? Cor van de Water kindly wrote: > If I read your post about the specs right: this battery > has 475 Watts per Cell for 15 min until at 1.67V per cell > at room temp. > This means about 250A for 15 min or 62Ah at about 2C rate. > Now that shold give you more than 11 miles / 27 Ah. How much more should it give us, given that we've been using about 250WattHrs/mile? Also, how much degradation should we expect from cooler temps, dipping into the 40s/50s at night for an ungaraged car? > You mentioned 133V without qualifying if this was DURING > charge (end voltage) or after charging. > If it was after charging, your charged battery voltage is OK. > If this was during charging, you are not fully charging them. ----- It was after charging. During charging, I usually go to 150 and then another 15-30 minutes. > Can you measure all 10 battery voltages while they are > under a constant load? > The easiest way is to take a wire of several tens of feet, > preferably 100 and connect that across the 12V battery you > are measuring and see the voltage drop. Take a reading after > a defined time, for example 15 sec and write that down for > each battery. > You may find that one or more are 1 or 2 volts lower than > the others. > Preferably do this measurement after you have driven, so > the bad batteries will show up worse. ------ 100 ft of wire connected from positive to negative? Sounds simple enough for even me (thank you!). ;-) What gauge wire? 70% of the batteries are harder to get to (under the back seat). Would it suffice to test the three under the hood? I'm guessing not as I'm testing individual batteries, but thought I'd ask before waiting till the weekend when I have time to pull out the seat and batt cover. FWIW, of the three easily accessible batteries, without a load, two sit within a hundredth of a volt of each other, and the third a tenth off from them. How close should they be? Would it be important to do this both before and after driving, or just after? > But in your case the DC/DC > seems fine, your aux battery may need a bit more juice > but seems OK otherwise, I guess the marine batteries > have been abused too badly. Your measurements should > provide more data. ------ That's what I'm afraid of, although the farthest we've ever gone is about 20 miles/45 Amphrs or so. Are what I have actually marine batteries? FWIW, I am aware of only one battery-related "event" when the DC/DC did (eventually) drain the pack down very low unbeknownst to me, back in February, and I had to charge each individual battery separately with an auto bat charger. I don't suppose the fall temps could account for any of this sagging behavior (he asked hopefully)? Thanks very much, and sorry for the newby questions!
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--- Begin Message ---Patrick Clarke wrote: > I have the impression that our pack may be losing a small > amount sitting still - say a tenth of a volt a day or so. > Is this indicative of a bad battery? Or of a paranoid user? ;^> If the pack really is losing 0.1V/day, this is 0.01V/battery/day. It might indicate a bit of self-discharge (normal or excessive), or it could (also) indicate that the batteries are cooling off as you leave them sit (the open-circuit voltage does have a (small) temperature dependence, though I don't recall if it is +ve or -ve at the moment). The real test is if each battery is dropping 0.01V/day, or if most are dropping little at all while a few drop much more. If all are behaving similarly, it is probably normal rather than indicative of a problem. > With the aux being dead, when the DC/DC come's on the > E-meter's reading jumps around in the 0-.6 amp range. > I've been wondering how accurate the meter is if it > isn't reporting a steady draw - it seems to even > momentarily leap into the positive range when the car > is sitting still, sometimes. Is it possible for this > to actually happen? The E-Meter's great strength is its ability to accurately measure currents that jump around a lot (this is exactly what happens when you are driving). I wouldn't trust the E-Meter right down to +/-0.1A, but it does generally do a very good job of measuring current. As for the current reading jumping around, especially at no load, this can indicate a poor or loose connection between the E-Meter and one of the wires from the shunt. The first thing to check is the tightness of the little screws in the terminal block on the back of the E-Meter. If this doesn't fix it, check the sense connections at the shunt. > There's an on-board charger with a "high" and "low" > setting. I start it on low, wait a few minutes and > then observe both the amps going in (usually around > 9-10 to start) and the amphrs used. I divide the > latter by the former and set the timer for the result, > adding two hours. I then check the amps on the emeter, > and assuming it's <4, I flick the charger to high for > a half hour or so until the pack is at 150 or so. I was > told not to leave it on high for more than a half hour > or so - and I haven't. So, a couple of questions: - what do you do if the current is >4A when you check? - what is the voltage before you flick the charger to 'high'? - what is the current during the time that the charger is on 'high'? The last thing you want to do is to hit the batteries with high current when they are nearly full as you may be venting a battery by doing so. Venting a battery will permanently reduce its capacity, and repeatedly venting it will reduce its capacity more and more. It would probably be better to leave the charger run longer on the 'low' setting and let the current taper to a lower value, such as 1-2A (or less, if the batteries will get there). If your pack is well-balanced, the current should drop to a low level like this fairly quickly after hitting the voltage setpoint your charger is set for (unless it is way off for the battery temperature). > At the end of a particular discharge or just after having > been driven a bit? You don't have to drive any particular route ;^> Just do some running around; go for coffee, etc. and burn up a reasonable amount of Ah, perhaps 15Ah or so (don't want to abuse the pack, and we know that by the time you've pulled 25Ah or so it is hurting). > Just sitting or under load as Cor suggested? Either one, or both. The no-load test will provide different information than the load test. If you were to leave the car sit overnight after draining 10-15Ah, then the no-load voltages you measure will be a fairly accurate indicator of the state of charge of each battery. As soon as you put a load on the battery you obscure the SOC information, but are able to identify batteries that may be at a high SOC (lots of capacity available), but have such high internal resistance that you can't get at the capacity due to the voltage sagging excessively at the sorts of currents you need to draw to move the car. > A thought - before I go buy a hundred feet of wire, > is there some kind of affordable battery tester that > I could purchase Our emails crossed paths; my prior reply included such a suggestion. With respect to Cor's 100ft or so of wire, probably the easiest way to do this would be a 50-75ft extension cord; short two wires at one end of the cord, and connect their other ends to the battery under test. If you already have such a cord, the cash outlay is nil, and if the cord survives the test, you aren't left with 100ft of wire with no particular purpose in life. ;^> Cheers, Roger.
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--- Begin Message ---Lee, Some time ago you mentioned using 1/8 or 1/4 watt metal film resistors for fuses at each battery. Does it matter if it's metal film or could it be carbon? Is it more of a size issue that determines the "fuseability" of a resistor? Mike
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--- Begin Message ---PatrickThat's the same Sevcon converter that I have. The manufacture claims it's good for 25 amps, but testing mine showed that it could only make about 22 amps.And, without any additional heatsink ( but with the mounting surface exposed to free air) it could only produce about 15 amps without going into thermal cutback. I now have mine mounted on a 1/8 inch aluminum plate ( about 1 square foot) that's in the airflow when the car is moving. Stationary tests showed that that much heatsink allowed it to work at it's 22 amp maximum continuously, so there should be an extra margin of cooling due to the moving air.So, your car may be drawing more amps than this DC-DC can supply ( especially if you have no additional heatsink). If your aux battery is failing ( or chronically undercharged) that may be the problem.PhilFrom: Patrick Clarke <[EMAIL PROTECTED]> Reply-To: [email protected] To: EV List <[email protected]> Subject: Re: Bad aux battery affects Voltage Sag? Date: Tue, 10 Oct 2006 09:59:56 -0700 Patrick wrote:I'm thinking our auxiliary battery is bad. If it were, would it be possible that the DC/DC continuously trying to charge it could be enough of a drain cause our traction pack to go down so fast?Death to All Spammers (gotta agree with that sentiment!) wrote:One question: What is your dc/dc converter's power output? 300watts is 20-25A, twice that if it's a 600watt version. -- Sorry for extra post, but I left off part: Even a 600watt converter should only be drawing ~6A from a 120V pack.I couldn't find it last night with a flashlight, but this morning I saw what appeared to be a spec's sticker on the side of the unit about a half inch from the side of the controller.If it helps, there's a 30amp fuse on the output, and it's a Sevcon Generation II. Says Isolated/Regulated 128/12V. Is this enough to go on, or should I pull the unit so as to read what's on the side?Also, Roland kindly shared his experiences with similar problems caused by many short trips. I don't know for sure that our aux. battery is bad (although I THINK it is), but if it is, I wouldn't think it was for the same reasons - although I could be wrong of course. When we drive it, it's usually for 20-30 minutes at a time. This should be long enough to keep a healthy aux. battery charged, shouldn't it?2nd question - Anyone have a recommendation for what to replace the aux battery with? I neglected to check it this AM for what make/model.. *blush*, but visually, it looks like a smallish motorcycle battery sized thing. After I replace it, I suppose I'll have a better idea of whether I have another problem as well, right?Thanks again - the assist is appreciated!_________________________________________________________________Express yourself - download free Windows Live Messenger themes! http://clk.atdmt.com/MSN/go/msnnkwme0020000001msn/direct/01/?href=http://imagine-msn.com/themes/vibe/default.aspx?locale=en-us&source=hmtagline
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--- Begin Message ---Roger wrote: > > The easiest way is to take a wire of several tens of feet, > > preferably 100 and connect that across the 12V battery you > > are measuring and see the voltage drop. >This may be easy, but it may also be dangerous. The C&D MR12-490s have >a short circuit current rating of 5000A; connecting a few milli-ohms of >wire directly across one might not be the safest idea. The key is in the length (and size) of the wire. Batteries will only develop hundreds or thousands of amps when shorted by a very low resistance (wrench, copper buss bar, welding wire, you get the idea) but when you take 100 ft of 14 gauge wire as in a cheap extension cord, you have around 1/2 Ohm of resistance. 12V divided by 1/2 Ohm gives you around 24 Amp of current, perfect for a load test. If you have a shorter cord (50 ft) you can use the two wires in series, for a longer cord or a higher Amp load test you can parallel the wires in the cord to get lower resistance and increase the amperage. I have used approx 12 gauge single copper wire, 100 ft doubled into two parallel sections of 50 ft to get close to the 1C discharge rate (80A) of my batteries to load-test them for 1 hour and check if they really delivered 80 Ah. The wire got warm, but not hot, because I strung it around my garage for cooling. I used a 250A DC breaker just for ease of connecting/disconnecting the load and for safety in case something would get shorted and because I happened to have this breaker lying around. Cor van de Water Systems Architect Email: [EMAIL PROTECTED] Private: http://www.cvandewater.com Skype: cor_van_de_water IM: [EMAIL PROTECTED] Tel: +1 408 542 5225 VoIP: +31 20 3987567 FWD# 25925 Fax: +1 408 731 3675 eFAX: +31-87-784-1130 Proxim Wireless Networks eFAX: +1-610-423-5743 Take your network further http://www.proxim.com
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