Battery problem

[ducatikid]

Hi guys, i'm running a B44 with a Mamba Max 7700kV system. Its been running fine until recently, after i have charged the Intellect 3600 cells the car runs slow then starts to pick up speed during a run. I'm only using a Ripmax Pro-peak charger with a 3.5A charge rate, the charger doesn't have an inbuilt discharge facility so i run the car down until the wheels stop. Can anyone shed any light, is it a dodgy cell?

Thanks in advance

Lee

[Mike Hudson]

you've probably killed your cells off abit, you shouldn't run your car till the wheels stop turning as this flattens the cells and shortens their significantly, also not equalising the cells on an equaliser will shorten the cells life too as you could be overcharging some off the cells and other cells could be discharged too much, as soon as your car starts to become slow while running you should stop and not run the car any longer.

[ducatikid]

Thanks for the reply Mike, i was a bit hasty the wheels don't stop as such, i turn the car upside down and push the thottle trim forward for about 2-3 minutes. Can you recommend a better charger for MIMH cells?

Regards

Lee

[Mike Hudson]

the lrp/nosram chargers are very good and have discharge functions too etc, would be good to get a novak or lrp equaliser tray too for your cells too :thumbsup:
these items sometimes come across at really good cheerful prices on here may be an idea to put up a wanted thread :thumbsup:

[Chequered Flag Racing]

i turn the car upside down and push the thottle trim forward for about 2-3 minutes.


similar to the light bulb explanation in this pic,
some cells will discharge more than others.

http://www.pro-trak.pwp.blueyonder.co.uk/im47res.jpg

then the following happens,
the over discharged cells charge don't charge fully, there the 2 lines that haven't reached there peak voltage (2nd part of pic). The other 4 cells have peaked and there voltage tails off. These 4 cells will be a lot warmer than the other 2 that haven't reached their peak voltage. Your battery pack will be the same.
http://www.pro-trak.pwp.blueyonder.co.uk/im50res.jpg
top part of pic shows cells that have been balanced on discharge

NiMh cells
1. should be charged @ 1c, yours are 3600mah so that's 3.6amps. if they were 4200mah then it would be 4.2amps and so on

2. Use for race or bashing until you feel the car just starting to slow then stop.

3. Discharge pack to 6v then use an eqauliser to discharge each cell to 0.9v

4. If not using them for a while NiMh like to be left part charged as they tend to self discharge over time.

To balance cells these items are used
link to Novak SE (http://www.teamnovak.com/products/dischargers/smart_tray/index.html)
link to Nosram (http://www.mirageracing.com/piw.php?partNo=NR91370)

[Chequered Flag Racing]

Best Practice for use of NiMH cells from the BRCA EB

see here (http://brca.org/BRCA/elecboard/news/2007%20NiMH%20cells%20%20Best%20Practice.htm)

the above was issued as guidance by the BRCA following a spate of Intellect 4200 batteries exploding for no apparent reason

[ducatikid]

Thanks very much for your help, wish i'd learnt this doing my HNC instead of power factor correction, would have been handier!

I'm taking the cells back to Paul at Cleveland Elite, he said he'd check them over for me.

I'm hoping to start racing again this year too so hopefully i'll meet some of you and get some tips.

Thanks again

Lee