Renogy 50Ah Lifepo4 tear-down

[OzyAdz]

I'm not going to stand on Anyone's toes. But here is my Renogy 50Ah Lifepo4. Thought it may interest the forum to see how this one is constructed inside.

100Amp BMS By the markings anyway. Looks cheap as
Construction looks very tidy.
couple temp sensors just floating up top.

Sadly after only about 20 cycles the battery wont accept any more amps after it hits around 13.68V it just drops out completely. after fully charging it and full draining it multiple times it will not provide more then around 25Amps now. Thinking the BMS is triggering some sort of "High Voltage" cut off far lower than 14.6v

Was thinking of just buying a Daly BMS and trying to see if the BMS was the problem. Renogy Didn't ask for it back and just refunded me back the purchase. After many emails and test photos etc. and a small reminder of my legal rights. Was interesting to see they didn't want it back to test what went wrong. Perhaps they are aware of some defects in this particular model or batch. Any how, I'm not complaining as in the end they did right by me so i thought it might as well throw it up on here for others to have a look at the quality and configuration. Especially seeing as how I've watched So many of Will's tear-down videos.

 

[Risky Rob]

So it's built from a large number of small cells?

 

[OzyAdz]

Yes, and i was aware of this as it's on the documentation on their website. Cell Model: IFR26650-3.4Ah

 

[fratermus]

Thanks for the teardown pics.

after it hits around 13.68V it just drops out completely. after fully charging it and full draining it multiple times it will not provide more then around 25Amps now. Thinking the BMS is triggering some sort of "High Voltage" cut off far lower than 14.6v

A runaway cell would cause these symptoms and charging at a lower voltage/current might fix the issue without any other changes.

Before changing to a different BMS I'd try dropping charging voltage back to 13.5v, then 13.6v, etc, until we get up to 14.0v or whatever. I charge mine to 13.8v and the cells are typically a few mV from lowest to highest. About a third of the balancing threshhold.

 

[OzyAdz]

Thanks for the teardown pics.



A runaway cell would cause these symptoms and charging at a lower voltage/current might fix the issue without any other changes.

Before changing to a different BMS I'd try dropping charging voltage back to 13.5v, then 13.6v, etc, until we get up to 14.0v or whatever. I charge mine to 13.8v and the cells are typically a few mV from lowest to highest. About a third of the balancing threshhold.

Thanks mate? i had a crack at that, No luck. on one side of the BMS (before the bms) the voltage reads 13.52v. On the other side (after the bms) 13.09V its like the BMS has some weird internal resistance caused by something that's malfunctioned

 

[obd.tech]

Have you checked the cell balance?
Maybe balance charge it with a hobby charger?

 

[Maccaman]

Hi all
I just had a similar issue with Renogy 50AH; they refused warranty claim, but I posted a review on Trustpilot and now they will refund. Battery is 10 months old in son's Triton, one of 2 installed in parallel and charged by DCDC charger. He left the 12V fridge on too long, overdischarged them, and then both batteries went open circuit. One reset with a Renogy 240V/12V lithium charger, the other did not.
Pulled it down as you did. First voltage measurement across the whiole cell bank was 5.7V. Very low. Because BMS would not reset, I trickle charged the cells at about 4A by connecting positive to positive terminal, and negative direct to the cell bank negative ie bypassed BMS. Discovered a big mismatch in cell bank voltages. Bank 2, 3 and 4 (from positive to negative order) are charging to 3.3V, bank 1 nearest positive terminal goes to over 4V, higher with higher charge voltages.
ie Pos terminal (Bank 1) 13.8V, end Bank1/start bank2 9.9V(3.9V drop) . Then an even 3.3V per cell bank till zero at the negative terminal.
BMS trips when the voltage gets uneven by more than about 0.3V.
I loaded the uneven bank 1 with a few 12V light globes pulling 1.7A while charging, and that equalised the bank voltages to keep the BMS in, but it will not charge the battery. I suspect all or most cells in bank 1 have a high internal resistance, and are cactus. No matter what I try, the BMS trips as soon as bank 1 gets to 3.5V, and the others will not come up above 3.3V.
Any comments?
thanks

 

[Jamie Marshall]

I'm not going to stand on Anyone's toes. But here is my Renogy 50Ah Lifepo4. Thought it may interest the forum to see how this one is constructed inside.

100Amp BMS By the markings anyway. Looks cheap as
Construction looks very tidy.
couple temp sensors just floating up top.

Sadly after only about 20 cycles the battery wont accept any more amps after it hits around 13.68V it just drops out completely. after fully charging it and full draining it multiple times it will not provide more then around 25Amps now. Thinking the BMS is triggering some sort of "High Voltage" cut off far lower than 14.6v

Was thinking of just buying a Daly BMS and trying to see if the BMS was the problem. Renogy Didn't ask for it back and just refunded me back the purchase. After many emails and test photos etc. and a small reminder of my legal rights. Was interesting to see they didn't want it back to test what went wrong. Perhaps they are aware of some defects in this particular model or batch. Any how, I'm not complaining as in the end they did right by me so i thought it might as well throw it up on here for others to have a look at the quality and configuration. Especially seeing as how I've watched So many of Will's tear-down videos.

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Did you find a solution, or try a new BMS?
I'm in a similar but different situation.

 

[Alkaline]

don't these things have like a 5 year warranty?

 

[Jamie Marshall]

don't these things have like a 5 year warranty?

Yeah, this is to try and re use the scrapped battery that they didn't want returned.