charging prius cells

icepuck

I recently checked the voltage of my spare Prius HV battery pack and now it looks like I need to figure out how to charge it.

NiMH 201.6 OCV(when fully charged) 6.5 ah there are 28 cells, each one is 7.2v.

After looking at various prii forums on DIY high voltage charging and some of the dangers involved I've decided to find a lower voltage and safer way of charging. I figure charging individual cells(7.2v) or in pairs(14.4v) would be safer.

Now for the real question-would an off the shelf NiMH charger work? At 6.5 amp hour I don't think it would take much, but at this point I'm not sure were to start looking.
-dan

kwinn

This sounds like the generation III or IV battery that consists of 28 modules of 6 cells. Not sure of the charge specs Toyota uses but the most common recommended charging rate for NiMh cells is a maximum of 0.5C (3.25A for this battery) and monitoring the temperature. Best to use a smart charger for this.
You can also charge each module at 0.1C (0.65A) for about 14 hours. This rate will not usually cause overheating.

Peter KG6LSE

what is your intended use for the pack ?..

Its not that hard to make a HV charger ..

If it was ME I would use a 1:2 Transformer to get that V up nice and high .. then use a micon ( pick your poison ) and PWM with a FET to limit the chargeing V thus the current in to the pack ..with TEMP and voltage and time feedback .


EG

if its like 20 H and its not charged fully ... KILL charge and light up a ERROR LED
OR of the temp is too hot . KILL and light ..

In a pinch a front end to a computer PSU would work
It has the V dubbler and the MOSFET on the board . and has wired a OPTO-ISOLATOR .


Peter

Lawson

Best info I've run across on Prius cells is this forum thread http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=6726&start=0

In short, Toyota appears to be using a different NiMH chemistry that what is typically found in cylindrical cells. Charging is best done with a CC/CV charger and a timer (like is used with lithium ion), or with a thermal charger. (looking for a fast temperature rise)

Lawson

icepuck

Peter KG6LSE wrote: »

what is your intended use for the pack ?.. Peter

it was left over from the donor parts car that I used to fix my brothers prius he bought wrecked.
We recently found another wrecked prius that had sat long enough for the 12v battery to go dead and HV battery to go to low to
start the engine.I had to use a jumper pack to power the computers to find out the state of charge for the HV battery.

Lawson wrote:

Best info I've run across on Prius cells is this forum thread http://www.endless-sphere.com/forums...t=6726&start=0

I'm still reading through that one.
-dan