I guess one possibility is to see if I can reprogram the Altrax for a lower cutout voltage to let it operate longer on 6 good batteries... however, am I just murdering the batteries if I do that? It seems like it's staying on till about 1.7vpc, and that's probably not good for the batteries to drop below that, right? If this were a PV system, I'd cut it off at 1.95 volts per cell, but I'd also be looking more at C/20 to C/50 rates instead of C2 to 3.
Z On Thu, Aug 29, 2013 at 11:35 AM, Zeke Yewdall <[email protected]> wrote: > Okay.... results are in. And, it's voltage sag that's killing it, not > thermal issues. With a 7th battery in series, it is a whole different car. > Easily pulls 300 battery amps when fully charged, and even towards the end > of the run, when it was sagging to 61 volts even with 7 batteries, it was > pulling over 100 amps. The controller is getting warm to the touch with > the heat sink and cooling fan, but not hot. The motor is too hot to touch > after the last run (I was doing quite a few hills, up to 16% grade). I > finally saw typical series motor behavior, having to shift to a higher gear > to accelerate, as the amperage dropped as motor rpm went up. > > I measured all of the 12 volt batteries a few minutes after coming back -- > all were sitting around 12.1 to 12.3, except one, which was 6.7. That's > not helping.... But, it was sagging to 61 volts with 7 in series, > including the one bad on, so I can assume that even with 6 good ones, it > will still run into this. I was 33AH down from full at the end -- for > batteries that claim to be 100AH (at much slower rate, yes.... and the 7th > one was only a 70AH rated one, it was sitting at 11.4 at the end). > > The controller will not turn on if it sees over 90 volts (I had to take a > short spin with the 6 original batteries in order to get it below 90 with > the 7th). So, I can't just change it to be an 84 volt system. Plus the > charger is for 72 volts, though it could be reprogrammed. Am I just > seeing the limitations of running a full size EV on 100AH 12 volt AGM > batteries? If so.... what's the other alternative? This car can't > really handle the weight of a 72 volt T105 set.... it handles bad enough > with what it's got (speaking of which... didn't '73 bugs come with sway > bars ? :) > > Z > > > On Thu, Aug 29, 2013 at 8:19 AM, Zeke Yewdall <[email protected]> wrote: > >> I happen to have an extra AGM battery available, that I can put in line >> and see if a higher voltage affects it. according to the spec sheet for >> the AXE 7245 its max voltage is 90 volts, so 7 batteries in series should >> be just under that if I let them rest a little after charging before >> connecting it up. I am also going to try to wire up a motor ammeter and >> voltmeter and see what that that side of the circuit is doing... >> >> Z >> >> >> On Wed, Aug 28, 2013 at 4:33 PM, EVDL Administrator <[email protected]>wrote: >> >>> On 28 Aug 2013 at 16:05, Zeke Yewdall wrote: >>> >>> > Batteries are staying around 61 volts under load. ...Is it possible >>> > that [the controller is] reducing current because of battery sag and >>> > not just controller temp? Does the alltrax have a cutback for >>> > battery voltage that you can program? >>> >>> I have old AXE and DCX manuals here. As part of their description of the >>> diagnostic LED. they both refer to a battery undervoltage shutdown. Both >>> say >>> the error LED will give you 6 red blinks in that condition. >>> >>> It's not clear from the manuals whether battery voltage is checked only >>> at >>> startup, or whether the controller monitors battery voltage and shuts >>> down >>> or cuts back on sag during operation. >>> >>> That said, I think it would be likely. Even the old PMC and Curtis >>> controllers did that 25-30 years ago. They would back down the battery >>> current limit to 50 amps if the battery voltage sagged to around 1.75vpc >>> at >>> their minimum nominal voltage. That is, if you had a 72-96v Curtis, it >>> would cut back at a battery load voltage of around 63 volts. >>> >>> You might contact the folks at Alltrax - or your dealer - and ask. Or >>> maybe >>> you could try adding an extra battery as an experiment. >>> >>> David Roden - Akron, Ohio, USA >>> EVDL Administrator >>> >>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >>> EVDL Information: http://www.evdl.org/help/ >>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >>> Note: mail sent to "evpost" and "etpost" addresses will not >>> reach me. To send a private message, please obtain my >>> email address from the webpage http://www.evdl.org/help/ . >>> = = = = = = = = = = = = = = = = = = = = = = = = = = = = = >>> >>> >>> _______________________________________________ >>> 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) >>> >>> >> > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20130829/fa61367c/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)
