I've been lurking here for some time and used the directions on this forum to repair my traction battery. I've replaced 3 modules, fully cycled every module, and connected them all with gator leads to balance the modules. After putting the traction battery back in, I was getting three codes to replace modules and one telling me to replace the whole battery. After sitting for a week I rebooted the system and tried again, now two codes for bad modules and nothing else after driving a mile or so. Another week passes and I do the same, now the only code I get is for module 12. It'll drive/run for a few minutes fine before the cooling fan kicks on, the warning lights come up, and if driving there is a loss of power. The 12v is new and I've checked for turbulence for the inverter pump. After pulling the battery again, all of the voltages look fine, though a couple on the end dropped slightly. What am I missing?
A standard dual filament headlight using both filaments in parallel is a good load. Your weaker modules will show a higher voltage drop under load. Another good indicator is a low rate of self discharge (after an initial drop as the surface charge dissipates). JeffD
X2 Most people skip this critical step and it's key to doing a proper job rebuilding your battery pack.
Same thing here. Just balanced all the modules got them all within .05 of one another. Got in it drove a couple of miles, battery charged all the way up, I was thinking yeah. Drive another couple of miles and the triangle reappears. Bring it back home, check connections, unplug and replug to reset and take it for another drive. Same thing, charging good but this time the red triangle shows up faster. By the third or fourth time, I was getting voltage surges and the battery cooling fan was really roaring. What is the proper load test procedure? I searched the forum, went several pages deep but didn't find anything. Has load testing been covered? Also if there is anyone near East TN that could analyze and fix I would be willing to pay. Just not willing to pay a dealer a huge amount for a new battery. The car is not worth what they are wanting for a new battery. Also, could something else be wrong with the battery besides the modules that would cause this type of behaviour or is it 95% of the time module failure? Excellent resource here and I don't want to hijack your post Arithian but your Prius is doing the exact same thing as the one I am working on for my daughter but it looks like you are able to drive yours for longer periods of time.
There are two tests to do to qualify a module that has sufficient capacity (amp-hours) and good open circuit voltage after charging (about 8v): Let the module sit for a few hours to dissipate the surface charge. It will drop from over 8v just after charging to about 7.8v. Then check again after about a week and the self discharge rate should be very low. Put a reasonable load on the module (a halogen head lamp with both filaments in parallel works) for 1 minute and measure the voltage drop. All of the good modules will have about the same drop under load and recover to the previous voltage when unloaded. JeffD
I used a halogen bulb to balance them out and had tested them over a 24 hour period and while I did have one that after sitting more than 24 hours had dropped faster than the others I thought it was in still good enough range. I mean the module was one that was not replaced because it had a 7.7 reading. The four I replaced had 6 something. The majority were 7.88. So the four 6.something modules were replaced, the 7.7 was left in, the four replacements checked out fine, the 7.7 then drops to 7.6, worse than previously... I guess I will try it again and if no luck try to find one already rebuilt by someone that knows what they are doing. Thanks Jeff for the help.
When you say you "balanced them out", do you mean you used a bulb to get them to the same voltage level? Did you do any reconditioning to the pack, or just replace the ones with 6.xx volts? You really need to load test them individually to see which ones are good. I can tell you from experience they can show good voltage, but drop out under a load. It does sound like the culprit is the one that drops to 7.6 by itself. They should all be around 7.85 or so. I would recommend changing that module. I would also suggest to recondition the pack while you have it out if you want it to last a while. Otherwise you may have to pull it out again to do the same thing in the near future. I know a Prius man in Corinth, MS who might can check the codes for you, but he doesn't recondition the batteries. The last time I talked to him he didn't have any 2nd gen packs to sell. I'd have to contact him first before I'd give his number to anyone. Or I'd be glad to repair your pack if you'd like and you're up for a little drive. Let me know if I can help.
You can do all of this yourself quite easily as long as you have a decent charger setup and mini VCI. First step should be to hook up mini VCI and see what your voltages (under load) and battery resistances look like: XP Home or XP Professional with Mini VCI? | PriusChat Second step is to load test them:......replace any that are out of spec (look at my numbers to see what I mean) Gen II Prius Individual Battery Module Replacement | Page 13 | PriusChat Third you should check capacity......again replace any that are not closely matched Gen II Prius Individual Battery Module Replacement | Page 11 | PriusChat Gen II Prius Individual Battery Module Replacement | Page 12 | PriusChat Last you need to balance them before they go back into the car (resting voltages must be close to do this): Gen II Prius Individual Battery Module Replacement | Page 12 | PriusChat Finally use your mini VCI again to check that voltages and resistances are where they should be again. If you do these steps properly you should have a battery that lasts quite a while after.
Balancing is to equalize the cell state of charge for the 6 cells (MTL has 8) in series in each module which recovers some module capacity. Then equalize the modules (get all of their resting voltages to the same value) by first getting them close with your "load" and then putting all 28 of them in parallel. JeffD
