diy solar

diy solar

Is this the Biggest LiFePO4 Battery Bank you've seen?

fafrd said:
Oh, he has a pair of straight-as-an-arrow busbars on the rightmost-terminals, 3 segments each.

Then the next row over uses a ‘snake’ design where a total of 7 busbars are snaked between two columns of cells (twice, each for 1/2 of the rows).

Instead of that, he could have again used 3 busbars to ‘straight as an arrow’ tie the first column of terminals together with 4x1 busbars used to jump between column 1 and column 2 terminals (forming a ‘comb’).

I’s still 7 busbars total but the worst-case resistance to the farthest cell is only 25% worse (5 busbars in series versus 4 busbars in series) instead of 75% worse (7 busbars in series versus 4 busbars in series).

If the maximum number of busbars that can be stacked on a single terminal is limited to 2, the snaked design is the only option. But if a stack of three busbars on a single terminal is easy, the comb design provides less variation in cell-to-cell resistance...
Click to expand...

Retreading my post I see that my coffee has not yet kicked in.

Should have been 67% worse (5 versus 3) and 133% worse (7 versus 3)...
 
fafrd said:
Oh, he has a pair of straight-as-an-arrow busbars on the rightmost-terminals, 3 segments each.

Then the next row over uses a ‘snake’ design where a total of 7 busbars are snaked between two columns of cells (twice, each for 1/2 of the rows).

Instead of that, he could have again used 3 busbars to ‘straight as an arrow’ tie the first column of terminals together with 4x1 busbars used to jump between column 1 and column 2 terminals (forming a ‘comb’).

I’s still 7 busbars total but the worst-case resistance to the farthest cell is only 25% worse (5 busbars in series versus 4 busbars in series) instead of 75% worse (7 busbars in series versus 4 busbars in series).

If the maximum number of busbars that can be stacked on a single terminal is limited to 2, the snaked design is the only option. But if a stack of three busbars on a single terminal is easy, the comb design provides less variation in cell-to-cell resistance...
Click to expand...

I'm new to battery design and a visual learner. So like this?
1597780095464.png
 
YellowBuddy said:
I'm new to battery design and a visual learner. So like this?
View attachment 20213
Click to expand...

Precisely, thanks.

A single wide busbar connected to all 8 terminals would probably be better, but if you are limited to using only the small 2-hole busbars, minimizing the number in series and maximizing the number in parallel will be better (perhaps marginally and if no consequence).
 
fafrd said:
Very nice build but I’m surprised to see you elected to ‘snake’ the central bus bars rather than go with a ‘comb’ design (straight central run up one set off cells with parallel fingers jumping over to the cells in the adjoining column).

The ‘snaked’ design has twice the length and twice the end-to-end resistance of the ‘comb’ design.

Perhaps the difference in resistance is immaterial, but was there some advantage to the snaked design that led you to prefer it?

Only two busbars stacked max compared to a max of 3 stacked with the ‘comb’ design?
Click to expand...
Looks like you nailed it - The screws weren't long enough to do a triple stack as required by a comb design. Additionally, the resistance isn't along the whole snake, it's only from left-right as the parallel connections aren't typically carrying much power rather just the balance current.
 
HighTechLab said:
Looks like you nailed it - The screws weren't long enough to do a triple stack as required by a comb design. Additionally, the resistance isn't along the whole snake, it's only from left-right as [B{the parallel connections aren't typically carrying much power rather just the balance current.[/b]
Click to expand...

Good point - probably inconsequential.

(And overall, a gorgeous build)
 
HighTechLab said:
Looks like you nailed it - The screws weren't long enough to do a triple stack as required by a comb design. Additionally, the resistance isn't along the whole snake, it's only from left-right as the parallel connections aren't typically carrying much power rather just the balance current.
Click to expand...

You know, I sat here thinking. I don't get why they call it a comb. Why didn't they just call it an E or IEEI design? Then it hit me.....hair comb. I was thinking honeycomb.
 
As of yet, the most my system has logged me drawing from these batteries is 39 KWH. The pack was still at 50.9 volts, so I know I still had room to go. Very satisfied with the results!! Now time to setup another 48 solar panels... Fun stuff
 
Since watching some of these battery banks being built on youtube, I've been thinking of building one for my main solar system. Only thing is I need about 50kwh to run it overnight, our night usage is lower than daytime at about 3kw per hour. We have a 10kw inverter with 12.9kw of panels using 4, 48 volt 60 amp charge controllers. Is there something on here that gives more info on how to do it? Thanks....the dog
 
the_uglydog said:
Since watching some of these battery banks being built on youtube, I've been thinking of building one for my main solar system. Only thing is I need about 50kwh to run it overnight, our night usage is lower than daytime at about 3kw per hour. We have a 10kw inverter with 12.9kw of panels using 4, 48 volt 60 amp charge controllers. Is there something on here that gives more info on how to do it? Thanks....the dog
Click to expand...
48 280 AH eve cels probably set you back about $5500-$6000 for the whole set up with BMS and bus bars
 
I think @Darkstar has the biggest bank(s) I've heard about. He's assembling a 64 cell bank from the 280AH EVE cells and already has a 14 (16?) BYD module bank going. He lives in my neck of the woods so I'm hoping to see his setup one day.
 
I have 32 of the 280's going into an RV over the coming months ... coupled with an 8 or 10 kW Victron. I can't wait!
 
Thanks for the suggestions. I followed a link for 200ah cells and found the company also makes 500ah cells. They have a very high rating on Alibaba and I've bought lots of stuff there with no problems, as long as the company has a good rating and is easy to talk to. I'm assuming the 500s would be better? Would I be better off building one giant battery or two or more smaller ones? Thanks the dog..
 
the_uglydog said:
Thanks for the suggestions. I followed a link for 200ah cells and found the company also makes 500ah cells. They have a very high rating on Alibaba and I've bought lots of stuff there with no problems, as long as the company has a good rating and is easy to talk to. I'm assuming the 500s would be better? Would I be better off building one giant battery or two or more smaller ones? Thanks the dog..
Click to expand...
Bigger Cells can be a good idea but only IF you are aware of the caveats of Large Cells. When playing above 200AH getting factory matched & batched certified cells makes more sense. There will be cell deviation (figure on 1mv per AH capacity) and drift as well. Even the high end Winstons, Calbs, Sinopoly, Thunderskies cells will do so. Also keep in mind that it takes a LOT of juice to charge big batteries (why that is an after-thought for many I don't know) and you have to figure on the Lowest Sun-Hour days if your charging via solar.
IE: CALB 500AH cells are $240.00 USD + S&H&Duties Each ! $4,500.00 USD for 16 Cells Delivered DPP

* Passive Balancing is fairly useless with large cells unless they are extremely well matched to start with.
* Active Balancing requires thought and consideration as well, it also presents some caveats. (also not all Active Balancers are good).
 
Thanks for the suggestions. It seems maybe it would be better to get more of the smaller cells than the larger ones since I spend a lot of time away and aren't always there to monitor things. We do have plenty of power to charge. On this system we have 12.9kw of panels in 4 arrays, with the ability to add another array which would boost the power to 16.2kw if we need to, the inverter is 10kw and our peak use is about 7kw for short times with about 5kw per hour average during the day and about 3kw per hour at night. We're at about 14.25*N latitude so we average full power from about 9AM till 3:30PM from April to September dropping to about 10AM to 2PM December and January, but since we set the system up to clip about 30% at full power there's lots of power left over and we are able to operate totally on solar from about 7:30AM till about 4:30PM at most times other than the last week of December or during the worst of monsoon season. We're in The Philippines so shipping is a bit less here than to the US and depending on the carrier import taxes can be a lot less as well. the dog
 
Im going somewhat the other side of the spectrum with 128s1p 50ah format of these cells. I like big gloves.....
 
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