That's interesting. There's some high-powered chargers here: http://www.powerstream.com/charger-low-noise-high-power.htm
They drop the voltage to 14.16 during the absorption phase. I think what you mean is once the current tapers to a predefined level at 2.45vpc charging, than that indicates 80% of charge, and the voltage is then dropped to lower the charge current? Essentially than, if vanilla CC/CV charging was used, this would destroy the battereis at a very high rate like this? Anyway, I tried charging some 2.3ah 12v batteries at 6 amps, and they took between 2.5 and 6 amps for most of the charging cycle without much heating. But once the started to drop less than 2.5 amps than they started to heat up fast. I think I'll take a cautious approach and stick to Jeff's rule of thumb or even less, unless I really need to use the bike NOW. Then I'll probably stick another charger or two in parallel (I've accumulated 10 Vector 10/6/2 amp chargers!). This shouldn't be difficult, as I commute only slightly over 4 miles to work. That should be about 7-8 ah, and charging all of the batteries in parallel on one 10 amp charger should take about 5 hours. If I need a full charge for lunch, than I can always stick another charger in parallel, and that won't even exceed the 10% rule of thumb. I guess it doesn't hurt to be cautious with over $700 worth of batteries. Regards, Andrew On Sat, Mar 22, 2008 at 8:27 AM, Tim Humphrey <[EMAIL PROTECTED]> wrote: > > Odyssey batteries demand an inrush current of at least 1C. Generally > speaking a battery can be fast charged at the same rate as discharge as long > as it is voltage limited to max 2.45v per cell up to about 80% full, then > the charge rate must be greatly reduced for the absorption phase (final > 20%). I wouldn't try this with gel cells, but flooded and pure lead AGM's > will be fine. > > If you accidentally outgas an AGM in most cases water can be added back to > the cells. But the process is not as easy as with flooded batteries. > > see http://www.odysseybattery.com/odycharg_a.htm > > Stay Charged! > > Hump > > Ignorance is treatable, with a good prognosis. However, if left untreated, > it develops into Arrogance, which is often fatal. :-) -- Lee Hart > > > --- On Sat 03/22, Jeffrey Blamey < [EMAIL PROTECTED] > wrote: > > *From: *Jeffrey Blamey [mailto: [EMAIL PROTECTED] > *To: [EMAIL PROTECTED] > *Date: *Sat, 22 Mar 2008 07:58:50 -0600 > *Subject: *Re: [ElectricMotorcycles] Fast charging---dumb idea? > > I can only comment on SLA: Sealed lead acid aka AGM has limitations as > to the voltage used. I you use too hign a voltage the battery can be > pushed to outgas and you can create a condition where a cell can fail, > then throw away the battery. Battery balance is critical as well. > Batteries in packs should be replaced at one time, putting one fresh > battery into a pack of 6 old batteries is bad practice. I can > understand if you had a battery fail in the first 6 months replacing > just the one battery, but after 3 years no. > > Rule of thumb for long battery life with lead-acid technologies the > rate should not exceed 10% of the Ah rating of the battery pack (or > single battery when charging with multiple chargers). So I am using 6 > - 6 Amp Pulse chargers for 55 Ah Universal 12250 battery. Being just > over 10% not a big issue, I would avoid let's say 10 or more amps to > get the most life. > > I expect if I limit my discharge to 50% depletion or less I can get > the rated number of recharge cycles. My charger is rated for 14.2V. I > have talked to people who live off grid with large battery banks and > have consistently kept the discharge to 50% and often less resulting > in battery life of 30% longer than mfg. stated. I have also heard of > battery lives of far less than rated (gel cells), I think the later > are not too popular in EVs. Anyone out there using Gels? > > Jeff 84 Franken'ceptor, Denver snow is gone, temps in 50s, the EMC > is ridden weekly (over 1100 miles) > > On Sat, Mar 22, 2008 at 5:49 AM, lyle sloan wrote: > > Sorry I dont have a clear cut answer, but here is my > > view on charging and batts and maybe it will help: > > > > All batteries are just trying to contain a chemical > > reaction inwhich both sides, the anode and the > > cathode, want to reach neutral. This chemical > > reaction is controlled by the rate of electrical > > discharge and the batteries' internal resistance. > > > > When we charge, we are using electrolysis to reverse > > the neutral state which is why the charge voltage must > > be higher than the original 12V. With electrolysis > > there will be loss of material because not everything > > transfers back over to exactly as it was before > > discharge. Some of the material will remain on the > > one side unable to transfer back over due to higher > > resistance, or lost during gassing. In addition, any > > material that transfers back to the original side will > > layer ontop of the highest conductive point. This > > means the original structure of the anode or cathode > > has become pitted or brittle, as well as brittle from > > heat. This brittleness can also be seen when fast > > charging (hi amps) because only the most conductive > > and highest point are going to get the material. If > > charging slowly (low amps), more material is able to > > transfer back to the other side evenly, filling all > > the gaps or holes. > > > > The life of the batteries is dependant on how well the > > structure of the anode and the cathode (both > > chemically and physically) remain as close to original > > as possible. High discharge and fast charging dont > > help in this respect. Moderate discharge and slow > > charging will preserve batteries. > > > > But the reality is, who wants to drive slow or wait > > forever on a slow chrage? That's why when charging, a > > combination of the two (fast and slow) is used which > > affects the life of the battery. So it will be up to > > each guy to figure out how long to charge for fast and > > then slow for the type of batteries he is using Which > > means battery life will vary from person to person. > > > > > > > > > > > > --- Andrew Wowk wrote: > > > > > Does anyone know exactly how battery life may be > > > shorted with fast charging, > > > provided the charge voltage is tempreature > > > compensated? My B&B batteries > > > have a max charging rate spec of .3CA whichseems to > > > be pretty universal for > > > most Chinese AGMs. I would like to charge them > > > faster on an as-needed bases, > > > but I'm wondering if this is a bad idea. It seems > > > like I could charge faster > > > in the bulk phase without too much damage to them. > > > > > > > > > > > > > > ____________________________________________________________________________________ > > Be a better friend, newshound, and > > know-it-all with Yahoo! Mobile. Try it now. > http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ > > > > > > ------------------------------ > *Join Excite! - http://www.excite.com* > The most personalized portal on the Web!
