Charge Prius Batteries

[Ben90]

Hello everyone,

Im recently got hands on a full pack of Gen1 Prius batteries from 2001. They have been lying around for some time now, but half of them seem okay, holding a voltage of over 7.2V when charged with 8V CV.

I dont have some kind of battery charger, but through the university some fancy lab stuff. So far I charged the packs with a laboratory power supply at 8.3V, limited to 1Amp. Anyone have advice not only on how far I can go with Voltage and Amps (as i figured by the other prius thread is 8.4V and 1C (6A)), but how charge them best with such kind of power supply?
Currently my charging looks like this:
1: Batt at Vbatt < 7V, the Charger runs in current limitation for some minutes
2: I reach selected voltage of 8.3V and drop Current from 1A to 0.1A over the course of one hour then almost constant at 100mA

Am I doing it right?

 

[Ykick]

It's gonna be hard with a PS because NiMh termination is supposed to happen when a enough voltage drop occurs as the battery nears full. A temperature sensor is also helpful for judging charge cutoff.

I don't know your cells and I understand they're a little different from the standard NiMh I'm accustomed to but perhaps you should dig around the forum for the Prius battery thread?

 

[Monstarr]

These chargers do the trick ok. http://www.all-battery.com/chargersfornimhandnicdbatterypacks24vto60v.aspx
I use a 40cell nimh tenergy charger on a 42 cell / 7 module Prius gen 3 battery and it cuts off at @ 59V and drops to 55V after a resting period...
Dont believe its fully charged at that point because the battery is not even warm, but i dont care...it is a relatively safe 'charge and forget' method and its gives me some miles of range...

When you want to use their full potential im guessing you have to use same sort of constant current charge and estimate the charging time.


Con: theyre awfully heavy and bulky
Con: their energy storage capacity is pretty low compared to lifepo4/lipo siblings

Pro: cheap
Pro: they put out amps like a mf.

Good luck
indeed search for the prius battery thread...it contains a lot of information

 

[Ben90]

I've already read the whole prius thread at least twice while waiting for my batts to charge at the power supply, but was wondering if I missed something. I don't want to max out the charge, but instead be sure I don't wreck them with my charging.
Charging with constant current would require a much higher charge current, like say 15V per cell to get the amps?
I'm not very familiar with battery charger technology, would that damage the cells? Or are my cells that damaged/old, so they dont draw more than 100mA after an hour of charging with 8.3V per (6 cell - 7.2V) pack? I was wondering if I'm doing something wrong, not archieving higher current.

I got the whole pack pretty cheap, about 40€ (50$), they have been used in a car test facility and layed around over a year, with a voltage of 10mV per cell when i got them, so I had almost no hope at the beginning of my tests, but they seem to be recoverable.

Attached a pait diagram of my charging curve.