Most of them that I've looked at say they support up to 4 in series, whether they work well or not, I don't know. I imagine they could end up with balance issues over time, but other than that, I don't know what problems there would be.
I said 125 because the nominal voltage for lifepo4 cells is 3.2v. Full charge is 3.65v, but if I remember correctly, they'll drop down to around 3.4v pretty quickly and then level off. If you need to keep above 400v, you'd want 125. On Thu, Aug 17, 2023 at 5:09 PM TJ Trout <[email protected]> wrote: > Which did you see that supports beyond 4 in series? I would be interested > to check those out. > > 125*3.65vpc= 456v > > I guess you need 125 if your running at nominal voltage (partial state of > charge) > > On Thu, Aug 17, 2023, 2:35 PM Mathew Howard <[email protected]> wrote: > >> I put four of the sealed 12v lifepo4 batteries in an electric lawn mower >> (it originally had lead acid), and it works well enough, but yeah, a single >> BMS is preferable, and I haven't seen any that say they can do more than 4 >> in series anyway. >> >> With lifepo4 you'll need 125 cells to get 400v... I'm not sure where >> you'd find a BMS that will handle that though. I assume there must be >> something out there. >> >> On Thu, Aug 17, 2023 at 4:06 PM TJ Trout <[email protected]> wrote: >> >>> Many of them have integrated heaters. >>> >>> Sealed lifepo4 batteries should only be used at the nameplate voltage >>> 12v for example, some will support up to four in series for a 48 volt >>> configuration but it's a hack job to do it that way. >>> >>> If you need 400v at 100ah you will need 110 qty of 100ah cells and a >>> compatible BMS. >>> >>> On Thu, Aug 17, 2023, 1:51 PM Chuck McCown via AF <[email protected]> >>> wrote: >>> >>>> My electric car loses significant range at temps below 35F and as a >>>> double whammy, will not accept a full charge at low temps either. >>>> >>>> Lead acid work at low temps but if they get too far discharged they >>>> will freeze. Gates Cyclons were advertised to be able to be fully charged >>>> and discharged when frozen. >>>> >>>> *From:* Mathew Howard >>>> *Sent:* Thursday, August 17, 2023 2:13 PM >>>> *To:* AnimalFarm Microwave Users Group >>>> *Subject:* Re: [AFMUG] battery nerd question >>>> >>>> Yeah, temperature is the main problem I'm seeing with going to >>>> lithiums. I can throw an SLA battery in an unheated box at our towers and >>>> it's going to work good enough, even in the middle of winter, but the >>>> minimum charging temperature for LFP batteries is 32F, which we're going to >>>> be below for a good part of the year. >>>> >>>> On Thu, Aug 17, 2023 at 3:08 PM Bill Prince <[email protected]> >>>> wrote: >>>> >>>>> Things have evolved. You can get LFP batteries for "almost" the same >>>>> price as lead acid. Sometimes less even. They occupy less than half the >>>>> space as lead acid, and will last at least twice as long. There is the >>>>> issue of temperature sensitivity and they will need help for extremely >>>>> cold >>>>> environments. >>>>> >>>>> >>>>> >>>>> bp >>>>> <part15sbs{at}gmail{dot}com> >>>>> >>>>> On 8/17/2023 12:36 PM, [email protected] wrote: >>>>> >>>>> Ooh What lithium batteries are we talking about? >>>>> >>>>> Last time I checked (a number of years ago), it was around 5x the $/Wh >>>>> to buy Lithium. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> *From:* AF mailto:[email protected] *On Behalf Of *Mathew Howard >>>>> *Sent:* Thursday, August 17, 2023 10:51 AM >>>>> *To:* AnimalFarm Microwave Users Group mailto:[email protected] >>>>> *Subject:* Re: [AFMUG] battery nerd question >>>>> >>>>> >>>>> >>>>> Well, right. It doesn't scale well, because battery costs and space >>>>> requirements will quickly become a problem. Batteries don't last forever, >>>>> so you have to factor in replacement costs too, which will be a >>>>> significant >>>>> ongoing cost for a larger system. I'm pretty sure that lithium batteries >>>>> would be cheaper long term now, since they should have a lot longer life >>>>> span and the initial cost isn't a lot higher, but then heating is >>>>> required, >>>>> which means you need more power. >>>>> >>>>> >>>>> >>>>> On Wed, Aug 16, 2023 at 7:02 PM <[email protected]> wrote: >>>>> >>>>> That’s building strictly for a 20W load though. Building for a tiny >>>>> load does make the costs easier. But if you wanted a second AP, bigger >>>>> backhaul, or anything else you can’t do it without growing the whole power >>>>> system proportionally. >>>>> >>>>> >>>>> >>>>> Steve was talking a 50W load today. The real high end hardware now is >>>>> using a lot of signal processing either to reassemble useful data out of >>>>> garbage or for beam steering, or both. So you end up needing 100-150W for >>>>> an AP. You’d be hard pressed to find a licensed backhaul under 35W, and >>>>> most of them are 50W+. We could say we won’t deploy that equipment….but >>>>> building for a 20W load takes the choice away. >>>>> >>>>> >>>>> >>>>> A 20A 240v circuit is 4800W. Or a 20A 120V circuit is 2400W. Even >>>>> 2400W would power almost any WISP deployment. Building solar to handle >>>>> any >>>>> load you might have is expensive, and building for only low power >>>>> handcuffs >>>>> you. >>>>> >>>>> You do your thing your way, no judgement. If it’s working for you >>>>> then it’s good, but I can’t see myself going that direction. >>>>> >>>>> >>>>> >>>>> -Adam >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> *From:* AF <[email protected]> *On Behalf Of *Mathew Howard >>>>> *Sent:* Wednesday, August 16, 2023 5:01 PM >>>>> *To:* AnimalFarm Microwave Users Group <[email protected]> >>>>> *Subject:* Re: [AFMUG] battery nerd question >>>>> >>>>> >>>>> >>>>> I'm at about the same latitude as you. My experience is that having >>>>> extra battery capacity is more helpful than oversizing the solar panels, >>>>> so >>>>> I'd probably go with Chuck's numbers for batteries if I was putting >>>>> something together now, and solar panels are cheap now anyway, so figure >>>>> 400 watts (if mounting space allows for it, which could be an issue if >>>>> we're trying to fit it on a pole). >>>>> >>>>> >>>>> >>>>> A quick check on Amazon shows 100ah SLA batteries for $160, so 6 of >>>>> those would give me 7200 watt hours, for just under $1k. At $1500 (which >>>>> is >>>>> mostly just adjusting battery and panel sizes from where I started at >>>>> $1k), >>>>> I'm right in line with Chuck's estimate, aside from the battery costs. >>>>> >>>>> >>>>> >>>>> On Wed, Aug 16, 2023 at 3:33 PM <[email protected]> wrote: >>>>> >>>>> I end up closer to Chuck’s estimate. In Southern or Central NY State >>>>> I’m 2 degrees north of Salt Lake City. 42N >>>>> >>>>> What’s your latitude? >>>>> >>>>> >>>>> >>>>> *From:* AF <[email protected]> *On Behalf Of *Mathew Howard >>>>> *Sent:* Wednesday, August 16, 2023 4:11 PM >>>>> *To:* AnimalFarm Microwave Users Group <[email protected]> >>>>> *Subject:* Re: [AFMUG] battery nerd question >>>>> >>>>> >>>>> >>>>> Yeah, that's what I'd do in a difficult to access location. I did a >>>>> site like that here (Wisconsin) with 200 watts of panel (I think the >>>>> actual >>>>> load is around 15 watts, so a bit more than 10x), and ~4kwh of battery. It >>>>> had some issues in January a couple years, but I attributed that more to >>>>> using cheap flooded deep cycles, rather than not enough capacity. With >>>>> AGMs, it's gotten through the last couple of winters without issues. 4kwh >>>>> of AGMs can be had for around $800, last I checked. Probably looking at >>>>> closer to $1500 when you add in enclosures and mounts, but some of that is >>>>> replacing parts that are needed with AC power anyway (smaller enclosure, >>>>> backup batteries, power supply), so that offsets it a bit. >>>>> >>>>> >>>>> >>>>> On Wed, Aug 16, 2023 at 2:50 PM Chuck McCown via AF <[email protected]> >>>>> wrote: >>>>> >>>>> Using my historical rules of thumb for off grid, snowed in mountain >>>>> top location for a 20 watt load I would do the following that has never >>>>> failed me: >>>>> >>>>> >>>>> >>>>> Load X 20 so 400 watts of panel. So less than $200 these days. >>>>> >>>>> 2 weeks of battery autonomy. >>>>> >>>>> 20 x 24 x 14= 6720 watt hours. $2K of batts >>>>> >>>>> Plus enclosures, mounts, charge controllers. >>>>> >>>>> >>>>> >>>>> $2500 and it will never go down in the winter. At my Utah latitude on >>>>> top of Utah mountains. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> *From:* Mathew Howard >>>>> >>>>> *Sent:* Wednesday, August 16, 2023 1:07 PM >>>>> >>>>> *To:* AnimalFarm Microwave Users Group >>>>> >>>>> *Subject:* Re: [AFMUG] battery nerd question >>>>> >>>>> >>>>> >>>>> It depends on how much stuff you're trying to run. A minimal micropop >>>>> can be done with less than 20 watts of load (single AP and backhaul). I >>>>> can >>>>> put together a solar setup for around $1000 that will power that. >>>>> >>>>> >>>>> >>>>> On Tue, Aug 15, 2023 at 12:50 PM <[email protected]> wrote: >>>>> >>>>> I can save you the suspense. If you have access to electric that’ll >>>>> be cheaper than solar. The problem is the need to run 24/7. You have to >>>>> design around the December-January months. I’m in NY State, and at our >>>>> latitude we only get a few hours of average production per day during >>>>> those >>>>> months. And obviously if it’s snowing for a week you need to be able to >>>>> ride through that on mostly battery power. Even with a modest load it >>>>> takes a silly amount of panels and batteries to stay up 24/7 in the >>>>> winter. More than you’d ever be allowed to put on a utility pole. >>>>> >>>>> >>>>> >>>>> Talk to your electric co about the smallest service you can get. >>>>> Explain what you’re trying to do and that your max load is very low. >>>>> >>>>> NYSEG normally doesn’t do less than 100A, but they made an exception >>>>> and let us do 60A. You need a meter can, a service rated panel, a conduit >>>>> up the pole and a weatherhead. Then you either have an outdoor outlet, or >>>>> have an outlet inside your enclosure. You’ll want the smallest service >>>>> they’ll let you do because of the wire size on the service cable. A 20A >>>>> (if they’d allow it) would only need a 12/3 with ground, and that’s up to >>>>> 4800 Watts (240x20) so it’s still more than you’d ever need. A 12/3 is >>>>> way cheaper than a 100A service entrance cable. >>>>> >>>>> >>>>> >>>>> My figure is 8 years old, and obviously there’s been inflation since >>>>> then, but I went to the same contractor who does electric installs for the >>>>> cable company and they quoted me about $1000. Even if it’s 3x that for >>>>> you >>>>> today you’d still never beat that with a solar installation even if they’d >>>>> let you do it. And I’m not some knee-jerk anti-solar lunatic, I’m just >>>>> saying I’ve run the numbers and it doesn’t add up. People do it when >>>>> they’re off grid, or when the electric service is unreliable in the area, >>>>> or sometimes just for the PR/marketing power of being “solar powered”. >>>>> Those are all fine reasons, but doing it for cost savings isn’t going to >>>>> work out. >>>>> >>>>> >>>>> >>>>> -Adam >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> *From:* AF <[email protected]> *On Behalf Of *Steve Jones >>>>> *Sent:* Tuesday, August 15, 2023 10:27 AM >>>>> *To:* AnimalFarm Microwave Users Group <[email protected]> >>>>> *Subject:* Re: [AFMUG] battery nerd question >>>>> >>>>> >>>>> >>>>> we have a dozen or so, but are looking at pole mount micropops (our >>>>> own poles). We are losing a grain elevator site because they >>>>> decommissioned >>>>> the elevator and theres no real options for the customers in some of the >>>>> areas. Im just trying to get to something we can get solar power with >>>>> enough battery to last through overcast. So Im calculating per battery >>>>> runtimes, then will look at number of batteries we would need to survive >>>>> vs >>>>> paying for a ROW meter vs losing the customers. Just have to get to the >>>>> cost per customer to retain them and the benefit gained per pole >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> On Tue, Aug 15, 2023 at 8:53 AM Brian Webster < >>>>> [email protected]> wrote: >>>>> >>>>> How many of the batteries do you have? Do you need any voltages other >>>>> than the 48 volts? If you have 4 batteries and only need 48 volts then >>>>> wire >>>>> them in series and not have to deal with the converter. >>>>> >>>>> >>>>> >>>>> Thank you, >>>>> >>>>> Brian Webster >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> *From:* AF [mailto:[email protected]] *On Behalf Of * >>>>> [email protected] >>>>> *Sent:* Tuesday, August 15, 2023 6:59 AM >>>>> *To:* 'AnimalFarm Microwave Users Group' >>>>> *Subject:* Re: [AFMUG] battery nerd question >>>>> >>>>> >>>>> >>>>> *You’re around C/30 which should be on the high end *of capacity*. >>>>> >>>>> Lower load usually means a little extra capacity out of the battery. >>>>> I realized that sentence might have been ambiguous. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> *From:* [email protected] <[email protected]> >>>>> *Sent:* Tuesday, August 15, 2023 6:56 AM >>>>> *To:* 'AnimalFarm Microwave Users Group' <[email protected]> >>>>> *Subject:* RE: [AFMUG] battery nerd question >>>>> >>>>> >>>>> >>>>> You can do the whole thing in Watts. >>>>> >>>>> >>>>> >>>>> 12V * 150ah = 1800 Watt-hours >>>>> >>>>> 1800Wh / 50W = 36 hours >>>>> >>>>> >>>>> >>>>> If they’re telling me 95% efficiency, I’d assume 50W out needs 53W in >>>>> (50 / 0.95). >>>>> >>>>> There’s usually an efficiency curve for the device based on load and >>>>> temperature so it wouldn’t be 95% in all circumstances. Your system >>>>> should >>>>> be drawing less than 5A off the battery, and if your multimeter has a 10A >>>>> fuse like most do, then you could put the meter in line and actually >>>>> measure the amperage before and after the converter. Then you’d know for >>>>> sure. >>>>> >>>>> >>>>> >>>>> And the battery’s total capacity will have a curve based on C-rate so >>>>> there’s some variability there too. Usually it lasts longer when you’re >>>>> drawing lower amperage. You’re around C/30 which should be on the high >>>>> end. >>>>> >>>>> >>>>> >>>>> Age and maintenance of the battery affect runtime as well. If I want >>>>> 6 hours of runtime then I plan Ah for 12 hours runtime. When my batteries >>>>> are halfway toasted I’m still getting useful life out of them. >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> *From:* AF <[email protected]> *On Behalf Of *Steve Jones >>>>> *Sent:* Monday, August 14, 2023 9:57 PM >>>>> *To:* AnimalFarm Microwave Users Group <[email protected]> >>>>> *Subject:* [AFMUG] battery nerd question >>>>> >>>>> >>>>> >>>>> Just trying to cipher runtimes >>>>> >>>>> I have on hand 150ah 12 volt batteries, so thats what id be looking to >>>>> use. >>>>> >>>>> Excluding the conversion loss of a 12v to 48v step up converter is the >>>>> math correct here? >>>>> >>>>> 12v 150ah=1800 watt hours >>>>> 1800 watt hours at 48v = 37.5ah >>>>> 50 watts of radio running 48v = 1.04 amps >>>>> 37.5ah @ 1.04 amps = 32.77 hours runtime >>>>> >>>>> >>>>> >>>>> does a step up that claims 95% efficiency mean 95% of the watt hours? >>>>> >>>>> -- >>>>> AF mailing list >>>>> [email protected] >>>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>>> >>>>> -- >>>>> AF mailing list >>>>> [email protected] >>>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>>> >>>>> ------------------------------ >>>>> >>>>> -- >>>>> AF mailing list >>>>> [email protected] >>>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>>> >>>>> -- >>>>> AF mailing list >>>>> [email protected] >>>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>>> >>>>> -- >>>>> AF mailing list >>>>> [email protected] >>>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>>> >>>>> -- >>>>> AF mailing list >>>>> [email protected] >>>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>>> >>>>> >>>>> -- >>>>> AF mailing list >>>>> [email protected] >>>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>>> >>>> ------------------------------ >>>> -- >>>> AF mailing list >>>> [email protected] >>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>> >>>> -- >>>> AF mailing list >>>> [email protected] >>>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>>> >>> -- >>> AF mailing list >>> [email protected] >>> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >>> >> -- >> AF mailing list >> [email protected] >> http://af.afmug.com/mailman/listinfo/af_af.afmug.com >> > -- > AF mailing list > [email protected] > http://af.afmug.com/mailman/listinfo/af_af.afmug.com >
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