Battery block becomes weak

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

 

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?

 

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.

 

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!

 

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?

 

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.

 

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