Hi guys , Sorry for posting another damn problem/question but here it is ... What exactly does battery block XX becomes weak mean and what can the causes be? Does weak just mean the voltage drops too far? Originally I had the issue on block 4, i measured a low voltage on module 8 and ordered a replacement from ebay... I then thought module 1 was a bit be suspect so ordered another. One of these two replacements was faulty so module 1 which i seemed to revive went into position 8 and the replacement module went into position 1. I cycled all the cells down to 6v and up to peak charge at least 3 times. Their discharge outputs all ranged from about 5500 to 7000mah. After charging them all i left them connected in parallel for 24 hours. I then measured the voltages they were all 7.56 (i think) apart from module 5 which was 0.02 volts less. After putting the battery back in the car and going for a quick drive the lights came back on. Originally I got battery block 3 and 11 becomes weak, i reset these and got block 13 becomes weak, reset this and then got 13 again. The warning comes up after about 2 minutes of driving. Now none of these blocks seem to be the ones i thought had an issue with so my question is what is the likely cause and are there any ways to easily diagnose this...? My thoughts are either: 1) my charger damaged the modules 2) I didn't clean the nuts, bolts or metal contacts 3) damaged wiring 4) I cycled them over about 4 weeks, maybe they discharged Does any one have any suggestions what to check and what's the most likely cause? Cheers Dan
Batteries are quite inexpensive in England, I think your best and most reliable option would be to buy a new one.
Yea, I'm starting to think you might be right, i think the local dealer does them for about £1400 but I'm so far through with this now I think I'll give it one more try before booking it in with toyota... I assume that toyota fit refurbished batteries rather than new ones, is that wrong?
I think the problem stems from you not cycling all the other modules with the replacement ones you got, to match up with individual capacities. Cycle akk the modules again, and match them capacity by capacity, voltage to voltage, and see what happens. Did you also load test them? That's the most important part of the job. You did a little bit of whaxk a mole approach though. Dxta
Thanks Dxta I did cycle and balance the replacement module if that's what you mean? What i didn't do was mix and match the capacity of modules... So apart from module 1 and 8, they are in the same order they were originally in... How would you advise doing this? Should i pair the lowest capacity module with the highest capacity module? I did load test them... They were all between 7.55 and 7.59 apart from module 1 which was 7.51 and 8 which was 6.37. I did this with one of the headlight bulbs attached. Cheers Dan
Thanks for confirming jerry. I assumed they were refurbished due to the surcharge they place on the parts.
Module 1 is ok, just needed to be cycled and put back. Module 8 was your problem. The difficulty is get a replacement that closely matches the other 27. Try and get one that is similar in voltage and capacity as the remaining 27. No, that’s not what he meant. He meant that you should do a 3 cycle charge/discharge with a final charge on all your modules. The connecting all modules in parallel for 24 hours thing (aka equalisation) is a waste of time. You don’t need to do that. Just make sure your final charge is to the same voltage. I’d aim for 7.9 V (60% SoC) per module. I wouldn’t mess with trying to “mix and match” or swapping modules around. Finally, get an in/lb torque wrench to ensure you torque each module down to the correct torque (sorry, can’t remember the correct torque off the top of my head, but search posts by ericbecky for that). Also, make sure all connections are clean from any corrosion, including the connector for HV battery ECU. If you have corrosion there, open up the ECU and repair that, if you are capable, or replace the ECU with a good one. Second-hand from a breaker should be cheap, but obviously you want one with no corrosion. If you don’t get success this go around, save yourself any further aggravation and get an OEM new. UK has one of the best prices in the world on a new OEM. Hope that helps.
Thanks Dolj! Maybe i wasn't clear. My apologies to all. Fortunately, i did discharge / charge them all 3 times. I thought the outputs were fairly reasonable varying from 5500 to 7000. Unfortunately i can't charge them to a set voltage only a set mah. Would draining them all to 6v and then charging them all 6000mah work? Or would it be best to just charge them all to full (delta peak) again? One thing I didn't do was tighten the bolts much or clean the nuts and plates, so that could well be the problem. I've got a few torque wrenches so will find the recommend torque as you suggested. Is there a recommended way to clean the plates and nuts? Oh additionally, I've got a screen shot of torque from a drive when a warning was flagged up... Cheers for your help!
Charging them to a lower mAh rating would get the job done. Not sure what value you should use to arrive at 7.9 V, though. If you get too much variance in end voltage, you can always use your load tester to discharge them down.
Cool! So maybe I'll charge them all to 6000mah then use the load tester (a volt meter and light bulb) to bring them all down to the same final voltage. I just realised you mention 7.9v, if fully charged would you expect them to still have such a high voltage after a few days storage? I could have sworn my batteries were all about 7.55v after i left them connected in parallel, maybe one of the batteries was leaking the energy or something?
Like I said previously, equalising is a waste of time and in reality would not have done anything of value, reconditioning-wise. Fully charged (as in true 100%SoC) each module would be in the region of 8.4 V per module (1.4 V per cell). 7.55 V is fine if you are more comfortable with it. You will have about 45% SoC once your battery is back together and recalibrated. So all good
So this won't answer the question directly, however, this should give you more information. Each module has 6 cells. The Prius has 28 modules. You are charging them to the full capacity, putting them in parallel will not do anything to them. However of you rest the modules after the testing any modules that cannot hold a charge will show it. This will help elimate them. Posted via the PriusChat mobile app.
Thanks mate... should I voltage test them with a load or without? What I've done so far is a quick discharge (1.4a) down to 6.5v and measured what the output was of each module. The ones causing the problem, loosely matched with the errors reported by the car. They outputted approximately 4400mah against an average of about 5100mah. I dropped this 4 modules down to 6v at 0.7a (this outputted another 300mah) and then charged them at 5a up to 5600mah. I then charged the remaining modules at 5a up to 5000mah. I'm hoping this will get them all roughly balanced but. Fingers crossed. Also, I read that the torque on the bolts should be approximately 5.4nm. I wasn't even remotely close to this... possibly 0.5nm, so this may have added to the issue. Oh and my copper bus bar plates weren't too dirty but here's a video of me cleaning them that you might all find therapeutic. Fingers crossed it works when it goes back together this time Edit: Any recommendations on cleaning the little silver metal contacts plates that go on every other bus bar would be appreciated.
You should test them with the loader just make sure they are working correctly. I personally wouldn't use anything that is 6.0 or lower. It's on its way out. Might as well change them out. I have not seen a difference about the tourqining of the 8mm nuts. If you feel safer then do it. The small plates I wouldn't mess with them too much. If you snap one it will delay the process. I replaced my plates with nickel coted ones. Posted via the PriusChat mobile app.
Thanks HybridGuy. I won't bother trying to clean them then. When you say you wouldn't use anything that is 6.0 or lower, do you mean 6000mah output from a full charge down to 6v? Cheers, Dan
