I found a battery on ebay, free shipping, 100Ah $299... im going to do a load test on it... should i post a video here?

[papab]

Thanks @wild1 .
It's surprising that everyone has a balance problem, but no one has low capacity. The supplier is great, I got my 70ah battery replace within days. I got the new one setup. BMS cuts out even worse, 13.66V. I charged it up really slow, 4.5 amps, then 0.7. I got +15.9 ah into it. Then a 20 amp discharge test resulted in 82 ah before it cutoff at around 11.5.

 

[papab]

I opened mine up after the discharge. Cell V = 2.834 3.211 3.224 3.222
Any idea what size wire fits best in the connector sockets? I used a sewing pin, but I'd like to find something better if I'm going to try to balance this. My shop has a better selection of nuts, bolts, & bike parts than electrical

 

[wild01]

Do you have a heltec active balancer?

 

[Supervstech]

I opened mine up after the discharge. Cell V = 2.834 3.211 3.224 3.222
Any idea what size wire fits best in the connector sockets? I used a sewing pin, but I'd like to find something better if I'm going to try to balance this. My shop has a better selection of nuts, bolts, & bike parts than electrical

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[papab]

Do you have a heltec active balancer?

No, i was going to buy a pwr supply & do them 1 at a time. I only have 1 battery

 

[papab]

It started cycling the BMS at 13.8, opened it up.
3.369 3.372 3.560 3.372

 

[papab]

Do you think if I set the charge controller to 13.6 or 13.7 and let it absorb for a while it will balance?

 

[wild01]

no it'll just keep tripping. cell 3 is pretty much full. if you are going to manual balance charge 1,2&4 one at a time, set your power supply to 3.65 @ 3A max put 2 stick pins in the connector to access cell 1 clip your ps leads to it and wait until it hits 3.65v@<.01a, then repeat on cell 2&4

 

[wild01]

just saw you still have to buy a ps. might as well buy a balancer https://www.ebay.com/itm/284517381958?hash=item423e8eb746:g:QS0AAOSwTHhhhPjS here's a fair priced one

 

[papab]

I don't know what to make of this, but note the large voltage spread for 1 & 3, & the small spread for 2 & 4

Discharged	2.834	3.211	3.224	3.222
Charged	3.369	3.372	3.560	3.372

 

[papab]

@will01, have you tested anymore of these? It seems odd that I'm the only one with low capacity (2 out of 2).

 

[ericfx1984]

Okay so what is a acceptable continuous load on this? That's the part I'm not quite finding and I probably just missed it cuz it is seven pages long

 

[ericfx1984]

I guess what I'm actually asking is what was the actual tested disconnect amperage on the bms?

 

[papab]

It says 100 amp on the side of the battery & I think one of the youtubers tested it

 

[wild01]

@will01, have you tested anymore of these? It seems odd that I'm the only one with low capacity (2 out of 2).

Having trouble getting an accurate test. Capacity meter was doa. My bogart meter is wildly inaccurate... Working on a solution.

 

[wild01]

Here's what I Have noticed so far. These batteries don't seem to mind heavy discharge loads, but there voltage sag is more than I like to see. Recharge amps is where they fall down. Recharging @ 40 or more amps causes the bms to disconnect early and the battery gets pretty toasty. It seems fine until the voltage goes over 13.8 then it kicks. If I then reconnect with my 10a ps I can charge for quite a bit longer. Papab this may explain your capacity problems- if you are charging at a higher rate. Thus far i haven't seen a huge capacity difference between balanced and unbalanced.

These numbers are not accurate, but they are both from the same inaccurate meter_97ah balanced battery 94ah unbalanced battery_

My suggestion for a charge setup would be bulk charge to 13.75 absorb at 20a max to 14.2 float @14

 

[papab]

I was topping off with 350W solar, which this time of year isn't much. Also, for the 2nd battery I topped off with a 4.5 amp Battery Tender. I'm using a Bogart Trimetric meter too (what's up with yours?) , but the load was also measured with a Kilawatt meter. I'll look at my notes tomorrow and post some data. Maybe I'll run another test.
In their 2 page manual it says 'after the battery has been fully charged & discharged 5 times, the battery can reach its maximum capacity' . I don't think I've read of this for LFP before?

 

[wild01]

Idk what is wrong with my bogart, but i know I cannot pull 95ah out of a battery only put 80ah back in and pull 95 ah out again. It's also about 15% off my clamp meter, but again idk what is and what isn't accurate.

Remember a kill-a-watt is measuring the ac side of things, so you lose about 20% to the inverter inefficiency.

 

[wild01]

Another good indicator that my bogart sucks.

 

[papab]

I topped off Batt#1 with the 4.5 amp charger. It started cutting out at 13.8V. Then I ran another discharge test. Results similar to the other tests, 67 Ah (Trimetric), 760 Wh (Kilawatt). The voltage dropped to 12.1 before it fell of the cliff. Assuming 12.7 average V, and 10% losses in the cables & inverter, the numbers match. 12.7*67*0.9=766 Wh . This was at a 20 amp load. I could probably squeeze a little more out of it with a lower load.
I'm charging it up right now with a Xantrex charger. The last I checked it was at 14.1V, 34.2 amps, +14.8 ah. I'll charge it up with this to about +50 ah & finish off with the solar which I can control better. Maybe I'll step it up gradually from 13.5.