HV battery balancing

ok need everyones expert advice. Heres whats going on. Battery goes from full charge to dead and back very fast. Assuming its a battery issue I removed the battery and volt metered every cell

1 8.14
2 8.14
3 8.14
4 8.13
5 8.13
6 8.13
7 8.13
8 8.13
9 8.13
10 8.12
11 8.13
12 8.13
13 8.13
14 8.12
15 8.13
16 8.13
17 8.13
18 8.13
19 8.12
20 8.13
21 8.13
22 8.12
23 8.12
24 8.14
25 8.13
26 8.13
27 8.14
28 8.15

So Im at a loss. now what? Please help.

 

ok need everyones expert advice. Heres whats going on. Battery goes from full charge to dead and back very fast. Assuming its a battery issue I removed the battery and volt metered every cell

1 8.14
2 8.14
3 8.14
4 8.13
5 8.13
6 8.13
7 8.13
8 8.13
9 8.13
10 8.12
11 8.13
12 8.13
13 8.13
14 8.12
15 8.13
16 8.13
17 8.13
18 8.13
19 8.12
20 8.13
21 8.13
22 8.12
23 8.12
24 8.14
25 8.13
26 8.13
27 8.14
28 8.15

So Im at a loss. now what? Please help.

 

Unfortunately, none of your cells has completely died yet. The only real way I can think of to determine which cell is bad is to measure voltage under load for a period of time. The bad module will show a rapid decrease in voltage pretty much as soon as its put under load. I would start from the middle and go to the left and to the right and then left right left right so on and so on. Its going to be a very time consuming thing unless you get lucky and find the bad module at the beginning. There's probably somebody else on here with better advice I recommend p mailing jdennenberg or Bob Wilson. that's the only way I can think of to isolate the bad module

 

The only way to test the pack is to fully charge it and then to check individual capacity of every battery in the pack while discharging it in controlled manner.

 

If you have a Prius-aware scanner that can read the 19 module pairs, you can monitor the voltages and do the following:

1. force-charge - hold the brake and floor the accelerator, monitor or record the 19 voltages.
2. reverse-discharge - with the rear wheels against a curb, put the car in "R", and monitor the 19 voltages.

Look for the pair that swings farther on each end.

Bob Wilson

 

I used RC model charger (imax b6 particularly) to test capacity of every module on my spare battery, this took few days. When giving voltage reading this is good idea to say what is SoC, when it is low you should worry about lowest , when high about highest voltage pack.

 

hello guys I'm from Mongolia, and my Gen1 prius battery has problem. 8 modules voltage is 6.9v and others 8.3v. And i'm going to rebalance these 8 modules. but i have only DC power supply and bulb. how many voltage should be set when recharging ?

 

en . wikipedia . org / wiki / Nickel%E2%80%93metal_hydride_battery#Charging
Remove spaces
Remember there is no access to single cell so don't charge in full, just all to the same voltage.

 

Each module consists of six, 1.2V, NiMH cells. If a module voltage falls below 1.2V from the others, it is usually an unrecoverable error. The "8 modules" are probably beyond recovery. IMHO, you are unlikely to have any 'balancing' success without replacing the failed modules. But the problem is the other modules have likely been stressed to the point of failing soon. Now to answer your technical question.

With what you've described:

• maximum charge to 8V
  • check temperature as a failing module will get hot
• minimum discharge to 6V

Use Zener diodes to clamp the limits as failing modules reach these voltages very fast. Humans watching meters does not work.


Bob Wilson

 

thanks for advice!
I charged them to 8.3 volts but after rechage, voltages go down to 6.9v after 30min. when I recharging modules, they became little warm not so hot! So i think 1 cell has failed inside the module. So i'll replace them.

But the problem is the other modules have likely been stressed to the point of failing soon.

how do you know these modules will fail soon?

 

• heat is the enemy - so the failing modules run hot and they heat the adjacent ones
• over charging is the enemy - with failing modules, the car will try to maintain operational voltages and this will stress the remaining modules

But "soon" is a relative term. I'll never try to discourage anyone from running the experiment. We're just trying to help manage expectations.

Bob Wilson

 

Hello,
i've replaced bad modules, and I'll see how long it will hold. And i've oppened 1 bad module that has 5.5volt, 2 cells has dried no liquid. I think the reason was that.

Thank you Bob Wilson,

 

oh god can't upload pic sorry

 

Hi I am new in this forum, but I have been doing the tedious process. I have found that all modules will show a similar voltage but big different in capacity that we do not know until balancing modules. One battery gave me code p3019 block #9 was week, I check every voltage n exactly, just one module in that block read 6.45v . So I replace that bad module, reassembly battery pack, but them I decided to do the balancing using two chargers x4, and after four days I found two more modules that did not recovered. Advance: you need to charge and discharge all modules to know the real capacity. Tech stream showed just block 9 going bad, and rest of modules were strong according to data.

 

Do the discharging / charging process to find out which or how many modules are going week. Modules that are about to died shows for example d/c: 900/1800.
Good modules will stay over 7.2 v after this process.

 

what exactly is the inch pound # for battery buss bar torque?

 

A one pound weight on the end of a wrench one inch long, or half a pound on a wrench two inches long.

John (Britprius)

 

... a spot-on definition of what an inch-pound is, but I thought the poster was asking how many inch-pounds are specified for the battery terminals (a very smart question to ask, because breaking terminals off makes an unsatisfying end to a project).

I would urge the poster to google for SSC 40G pdf (be sure it's the 40-some page "technical instructions", not the shorter "dealer letter"), which will contain not only those torque specs but the rest of them. and a lot of other information that anybody working on the battery should really have, and the poster probably doesn't, if having to ask about the torque specs.

-Chap

 

^^^ My slight misinterpretation of the question that perhaps should have been "what is the torque setting for the battery bus bar nuts?"

John (Britprius)