LIFEPO4 Battery discussion thread

denmendez65 said:
View attachment 1908769

Like this one. Was only on Temu. Now it’s not on Temu but sold locally. People that would buy these would say the battery never looked like the picture even though the capacity was as stated.

Suspect local are just buying in bulk and get cheaper rate and resell with different branding.
Click to expand...

Its R9000 now on temu from the same seller as before.

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share.temu.com
 
wingnut771 said:
Hurry hurry, only R23k for their 5kWh.
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Missed the kWH sizing. That is pricey but then again it’s BYD. Probably has an EV style BMS so will have all the fancy protection etc and outlast typical residential batteries.

Tesla uses their tech I believe
 
denmendez65 said:
Missed the kWH sizing. That is pricey but then again it’s BYD. Probably has an EV style BMS so will have all the fancy protection etc and outlast typical residential batteries.

Tesla uses their tech I believe
Click to expand...
Tesla also uses CATL and Panasonic and LG and SK.
 
wingnut771 said:
These pics are confusing all with different voltages.

You want to have at least 3.45V per cell (55.2V pack voltage) to be 99.9% SOC and not going into the steep part of the voltage curve where it just ages the chemistry faster without anymore capacity.

I see battery 1 looks pretty balanced now (I remember this being a problem in the beginning and why you dropped charge voltage to stop the errors).
View attachment 1907597

Battery 2 has some way to go to balance:
View attachment 1907598

So not sure why we see 54V (maybe its floating?), but can only really check cell balance at 55.2+V.

Anyway, I would use:
BULK 55.2V
FLOAT 53.6V
LOW 44V

Above values are on battery side so factor in voltage drop on inverter side.
Click to expand...

One of the reasons why I previously set my voltage a bit higher if you can remember is that I was struggling with the inverter going into float mode earlier than expected and then the battery sits like at 80%. Didn't balance. Changing it to AGM mode cause the OVP warnings.

Google AI says its a known issue with axpert clone inverters in the USE settings mode as float is triggered early once the pack gets closer to full due to the flat curve.

It suggests using the equalizer feature to trick the inverter into staying at the bulk voltage so I can reach 100% soc and top balance.

Do you agree?
 
cavedog said:
One of the reasons why I previously set my voltage a bit higher if you can remember is that I was struggling with the inverter going into float mode earlier than expected and then the battery sits like at 80%. Didn't balance. Changing it to AGM mode cause the OVP warnings.

Google AI says its a known issue with axpert clone inverters in the USE settings mode as float is triggered early once the pack gets closer to full due to the flat curve.

It suggests using the equalizer feature to trick the inverter into staying at the bulk voltage so I can reach 100% soc and top balance.

Do you agree?
Click to expand...
I remember AGM mode causing OVP as that was using 58.4V. I remember you setting USE to 56V to factor in voltage drop and to stop OVP warnings. First I'm hearing about a FLOAT issue. Does it not get to 56V?

Not sure if equalizer uses pulses which is bad for LFP, also not sure what voltage that uses either or can you set it? Anyway, we shouldnt need this if we can absorb at 56V and float at 53V not that you float for very long as you start using the battery as soon as the sun goes down.

This is why I asked what the cell balance looks like on bat 2 at 56V. We still dont know how the balancer works. If its good, we can try increase voltage a bit to 56.5V. Then again to 57V. This will top balance the cells properly and shorten absorption time (if that's what this float issue is?).
 
wingnut771 said:
I remember AGM mode causing OVP as that was using 58.4V. I remember you setting USE to 56V to factor in voltage drop and to stop OVP warnings. First I'm hearing about a FLOAT issue. Does it not get to 56V?

Not sure if equalizer uses pulses which is bad for LFP, also not sure what voltage that uses either or can you set it? Anyway, we shouldnt need this if we can absorb at 56V and float at 53V not that you float for very long as you start using the battery as soon as the sun goes down.

This is why I asked what the cell balance looks like on bat 2 at 56V. We still dont know how the balancer works. If its good, we can try increase voltage a bit to 56.5V. Then again to 57V. This will top balance the cells properly and shorten absorption time (if that's what this float issue is?).
Click to expand...

So yes AGM caused ovp warnings. Then use setting at 56v got battery 1 to 96% usually and my float was also higher and it would sit at 96%. I think it over time the few time it did reach it it balanced.

The float bug would come in sometimes even when draining the battery yo like 88% the inverter will still be in float.

It wasn't so prevalent with just 1 battery because I could hit max on it at least 2 times a day. Now with 2 battery I'm seeing the float bug creep in again.
 
cavedog said:
So yes AGM caused ovp warnings. Then use setting at 56v got battery 1 to 96% usually and my float was also higher and it would sit at 96%. I think it over time the few time it did reach it it balanced.

The float bug would come in sometimes even when draining the battery yo like 88% the inverter will still be in float.

It wasn't so prevalent with just 1 battery because I could hit max on it at least 2 times a day. Now with 2 battery I'm seeing the float bug creep in again.
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Ok, I would make float same as bulk/absorb then, 56V. Then slowly increase voltage when cell balance is good with no OVP cell warnings up to 58V so its top balanced properly. Then once cell deviation is small at 58V then you can reduce back to 56V.
 
denmendez65 said:
I believe panels and wiring cause the most fires
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No, the gas composition (hydrogen/oxygen ratio) needs to be absolutely perfect and then also a spark from somewhere for an explosion to happen which is rare. So the 3 explosions were the house in germany (basement I think but blew off a corner of the house), houseboat (caught on video windows and doors blowing off) and this latest one from california of the outhouse built like a tank with aircon and everything. The 4th one isnt even a battery explosion, but something else at BYD factory or something.

Maybe you should watch the video.
 
wingnut771 said:
No, the gas composition (hydrogen/oxygen ratio) needs to be absolutely perfect and then also a spark from somewhere for an explosion to happen which is rare. So the 3 explosions were the house in germany (basement I think but blew off a corner of the house), houseboat (caught on video windows and doors blowing off) and this latest one from california of the outhouse built like a tank with aircon and everything. The 4th one isnt even a battery explosion, but something else at BYD factory or something.

Maybe you should watch the video.
Click to expand...
I’m not talking batteries. Talking solar homes and installations. The most common causes of fires etc is panels and wiring. Not batteries
 
So AI and general recommendations are do not parallel different capacities and batteries of different ages as they won't work well together.

What if I buy a 15kW omnivolt and parallel it with my 2 x 5.12kW batteries? Doesn't look like BMS does anything even if they communicate so if you mix battery brands up and just keep and eye on the cut off and full charge voltages you will be okay.

 
cavedog said:
So AI and general recommendations are do not parallel different capacities and batteries of different ages as they won't work well together.

What if I buy a 15kW omnivolt and parallel it with my 2 x 5.12kW batteries? Doesn't look like BMS does anything even if they communicate so if you mix battery brands up and just keep and eye on the cut off and full charge voltages you will be okay.

Click to expand...
Its fine, the bigger battery does the heavy lifting. Andy has 100kWh parallelled together, all different Ah.

Here's an extreme example:
 
cavedog said:
So AI and general recommendations are do not parallel different capacities and batteries of different ages as they won't work well together.

What if I buy a 15kW omnivolt and parallel it with my 2 x 5.12kW batteries? Doesn't look like BMS does anything even if they communicate so if you mix battery brands up and just keep and eye on the cut off and full charge voltages you will be okay.

Click to expand...
All that happens is the higher capacity one does more of the work in proportion to its ratio of its size in the overall bank. 100ah and 50ah, the 100ah will discharge twice the energy the 50ah. Nothing wrong with that. AI is not entirely accurate there.
 
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