LIFEPO4 Battery discussion thread

denmendez65 said:
The power of chemical corrosion.

View attachment 1910660

The clean copper busbar is the old positive leg. The other, which was a little bit better than what it is now, was the negative. I had them in there as a temporary measure but damn, I didnt expect the negative side to corrode that badly and that quickly (1 year).

Explanation is found is that the batteries gas a little when getting charged. Its mostly positive ions. They get attracted to the negative busbar where electrolysis happens, breaks down the water and hydrogen is formed which escapes but leaves the busbar in an alkaline state.

It starts to eat away at the copper. The high humidity in the last 2/3 months accelerated this process very quickly also. The unfortunate part is my fan was actually sucking highly humid air from the inlet which accelerated the process also. That's why in the first 8 months there was little to no corrosion until the last 3 months where it rained non-stop.

Another issue that was there, was the brass screws used to mount the positive busbar were completely eaten away. They acted as a sacrificial anode for the positive busbar. They potentially also helped keep the positve one healthy. Screws on the negative were perfectly fine.

Victron busbars are coated with tin and are used for marine applications which will make them last much longer. I also got myself Battery terminal protector spray. I will cover all the connections with the spray. It basically creates an additional barrier between the copper and tin with the atmosphere. Reviews say it should be good for up to 6 years and longer. Heat reduces the time like in an engine bay but my busbars run cold.

I touched my busbars while pulling 100A for a couple of minutes and they were cold, like grabbing a metal key in this cold weather. All the cables were cold also since they are overrated.

There was no corrossion on the lugs by the way, even on the ones connected to the negative busbar. I had used tinned ones there also. So the tinning definitely helps.
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Why not just give them a good covering of this...

 
wingnut771 said:
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I think this is relative. When I had only 1 x 5.12kw battery I would hit 100% often and quickly and multiple times a day. Once you have more battery capacity if you can't maintain a regular 100% SOC for a few hours passive balancers struggle. Active balancers become a good option then because they can achieve more for those short 100% soc times.
 
cavedog said:
I think this is relative. When I had only 1 x 5.12kw battery I would hit 100% often and quickly and multiple times a day. Once you have more battery capacity if you can't maintain a regular 100% SOC for a few hours passive balancers struggle. Active balancers become a good option then because they can achieve more for those short 100% soc times.
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Once a battery is top balanced then you don’t need constant balancing so a short daily 100% is enough.

These boards never turn off so if you fit one to do “maintenance” then you need to unplug it when it’s done or else it will carry on balancing all the way to 2.7V. Also if you store your battery, it will drain it dead. Andy found out the hard way with cells in the 1V range.
 
The lowest he was willing to go for the CFE battery was R4800 so I bought one. Went through them and all of them had like a pack voltage of 45 - 46v so empty.

I took the lid off and see tested the cells. Lowest cell was 2.72v

There is some expansion on the side cells as you can see but I'm not so concerned about that. This battery does not have a screen so it was difficult to see cycle count and age but it shows 2023 models so it has aged calendar at least.

Will see how it performs. It will be difficult because no screen so I need to figure out how to connect to it and how to read the bms data. Looks well build so the research I did showed the biggest issue was the bms.
 

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cavedog said:
The lowest he was willing to go for the CFE battery was R4800 so I bought one. Went through them and all of them had like a pack voltage of 45 - 46v so empty.

I took the lid off and see tested the cells. Lowest cell was 2.72v

There is some expansion on the side cells as you can see but I'm not so concerned about that. This battery does not have a screen so it was difficult to see cycle count and age but it shows 2023 models so it has aged calendar at least.

Will see how it performs. It will be difficult because no screen so I need to figure out how to connect to it and how to read the bms data. Looks well build so the research I did showed the biggest issue was the bms.
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Its got a shunt and t-class fuse and everything. Nice. Lets hope it has capacity.
 
cavedog said:
The lowest he was willing to go for the CFE battery was R4800 so I bought one. Went through them and all of them had like a pack voltage of 45 - 46v so empty.

I took the lid off and see tested the cells. Lowest cell was 2.72v

There is some expansion on the side cells as you can see but I'm not so concerned about that. This battery does not have a screen so it was difficult to see cycle count and age but it shows 2023 models so it has aged calendar at least.

Will see how it performs. It will be difficult because no screen so I need to figure out how to connect to it and how to read the bms data. Looks well build so the research I did showed the biggest issue was the bms.
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You have gone down quite the rabbit hole.

From needing backup to opening batteries and having 3 batteries etc. Welcome to the solar life...
 
wingnut771 said:
Its got a shunt and t-class fuse and everything. Nice. Lets hope it has capacity.
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Can't seem to get comms working for this stupid bms. Been trying all afternoon. I'm actually thinking of just replacing the bms.
 
cavedog said:
Can't seem to get comms working for this stupid bms. Been trying all afternoon. I'm actually thinking of just replacing the bms.
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Got the wifi working with them and their app?
 
cavedog said:
So no screen, no soc indicator lights and no voltage readings at all so I don't know what the battery and cells are doing at all.
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Well, you don't need to know voltage and soc as all the batteries are the same, its just the cells voltages we dont know but they "should" be ok at 44V-56V. Just wing it:
ignorance-is-bliss-cypher.gif
 
wingnut771 said:
Well, you don't need to know voltage and soc as all the batteries are the same, its just the cells voltages we dont know but they "should" be ok at 44V-56V. Just wing it:
View attachment 1911123
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Well I have it on charge now. 55.4v lets see what it does when it reaches "100%" and when I add a load on it how long it lasts.
 
cavedog said:
Well I have it on charge now. 55.4v lets see what it does when it reaches "100%" and when I add a load on it how long it lasts.
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What are you charging to? How will you know when its 100%? Are you only putting a load on bat 4? How do you measure the Ah?
 
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