Hey Everyone,
First of all, I really appreciate all the ideas and feedback. I'll take a stab at responding to some of the various comments/remarks/questions. First, temperature. Yes, the temperature in Austin has cooled off, but my Jeep doesn't have a top and I typically don't drive it unless it's 65 degrees F or higher. SO the temperature has come down from the 80's and 80's to high 60's and 70's. I think that's had an affect. Perhaps my cells are a bit undersized and this little bit of temperature change is just a bit too much. Charging. My charger charges the pack until it either hits close to 180V or until my mini bms turns it off. When the charger shuts off, almost every mini bms is red (shunting current.) Occasionally I go ahead and do a top balance and I find that the cells that weren't charged all the way were very close. So I don't believe I have a problem with cells not being all the way charged. I said that things start at 160V, but it's really more like 165-170V. Connections. I did not use any grease for my connections. I did use all stainless steal. I haven't noticed a high temp connection, but maybe my sag is a combination of bad connections. Undersized batteries. I think I should have gone with Calb 180 Ah cells. I do think I'm pushing the one I have too much. This was my first EV and I figured that 20 Ah and 160V was a good goal, this led me to Calb 130 AH. I read the "datasheet" and saw the max was 1000 Amps. I set my max to 400 amps and figured if I generally stayed under 3C (keep between 1C and 2C) I'd be ok. Temperature again. I did charge outside on hot days without active cooling. I monitored the ambient temperature around the pack and found it go around 114F which is near the limit of what Calb recommends. I may have done damage to my cells by charging to hot and doing to much discharge. I really like the idea of hooking up a dummy load to the pack so I can measure the voltage everywhere and look for things that are out of whack. A good dummy load system seems like a good investment for an EV guy (or gal.) Another thing. I've been complicating an AC75. Doing this would cause me to change the whole pack, charger, dc-dc, etc. Not sure I'm willing to spend so much (not sure how much I could get for my current pack), but if go this route, I can more carefully pick battery sizes. I would probably want around 105V and 300Ah cells. This would be a pricey and expensive pack! I've been considering a leaf... -ben www.evalbum.com/4001 On Jan 25, 2013, at 12:30 PM, David Ladd <[email protected]> wrote: > > I see similar sag and low voltage alarm issues, though not quite as extreme, > with those same cells in my car when it is cold out. all the cells are in my > trunk so I have no way of seeing the mini BMS while driving, so I bought a > cellog 8. it records voltage data on 8 cells at a time, and I can move it > around until all the Cells have been tested. in my case it showed me that I > have a couple of cells that sag to 2.3 volts while the rest stay up around > 2.7v. It's a cheap way to get some good data. > > David. > > Sent from Yahoo! Mail on Android > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130126/0ed945e9/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
