diy solar

diy solar

Does anyone have a drawing?? 24V 32cell

ghostwriter66

"Here - Hold my Beer"
Joined
Nov 13, 2019
Messages
1,868
Location
EE from LAX CA -work in SouthTX for giant evil Oil
Hi.... totally away from my desktop and working off a small tablet out here for the next two days ...

One of the Security Officer contractors out here in his RV just received 16 (3.2) 200aH and 16 (3.2) 280aH LiFePO4 batteries from China. He did not order 280's but they messed up and sent him 16 of them anyway.

His intent is to hook them all together and run a 24V system. He will keep the 200 and 280aH in Parallel with each other and not put them in series ...

He is about 50 miles from me and i tried to draw it out for him on paper a few minutes ago and take a picture but between my awful drawing and this crappy camera on the phone - its kind of hard for him to make out and he has to get it right perfectly ...

If at all possible can someone do a quick sketch of what the 32 batteries will need to look like all connected so i can send him a pic or pdf. It doesn't have to be pretty ... NO RUSH - Unlike me he has SAT and SUN off and he said he would check his email in the morning since he wants to try to get his system set up this weekend and I am stuck on Duty tonight from 1900-0700 out in the middle of nowhere.

Normally i can help these guys over the phone but this guy seems to be 100% visual (has to see the solution not hear it) ...

Cellular service is spotty out here and SATCOM is slow - so if I don't answer right away Thnks in advance ...

@Craig @tictag @Steve_S (just throwing this over the fence to see if you are awake and have a quick diagram ... thx)
 
I have this saved on my PC. I think it was one that Steve posted a while ago. Hope that helps.

multi-parallel-packs.jpg
 
Here's a quicky @ghostwriter66 if this is what you are looking for.
Paralleling cells is not a brilliant idea but it works, just advise your friend that this negates individual cell monitoring & balancing as one cell is technically ghosted by the other(s). The ideal configuration is to use 8 Cells for 24V and having each cell monitored & managed by the BMS.

Note NEVER mix cells of different capacities into a pack. In your friend's case, he will have to build 200AH & 280AH packs. They can go into a Bank together without issue provided the BMS Settings are correctly set & matched AND the bank is properly wired to be balanced as much as possible. Also, I cannot understate the importance of Calibrating the Voltages to ensure everything is reading properly to prevent over/under charging or having erroneous disconnects that can potentially cause problems.

24-Volt-Pack Design.jpg

Good Luck.
Steve
 
THANKS GUYS .... you're my heroes ... I will get this to him right away -- my 12 hour shift stretched into 15 and virtually the entire time NO Cell service and good god trying to do anything off of Iridium is painful so just got back into cell range ... THANKS AGAIN
 
Don't forget to tell your friend that he will be seeing dissimilar current flow from each pack, though I would expect them all to discharge equally. Also, if he does actually use them he might find it more difficult to have them replaced with the ones he actually ordered.
 
Don't forget to tell your friend that he will be seeing dissimilar current flow from each pack, though I would expect them all to discharge equally. Also, if he does actually use them he might find it more difficult to have them replaced with the ones he actually ordered.

I talked him OUT of replacing the wrong 280aH with the right 200aH since it would be 45 days shipping back -- 45 days shipping here .... and him losing about 40% capacity ...
 
Last edited:
I'd flip it the other way.
He ordered 32x 200AH cells. Got 16x 200AH & 16x 280AH, the 280's ar a Bonus of extra AH's and especially if they did not charge him the extra for 280 over 200.

2 Packs of 24V/200AH + 2 Packs of 24V/280AH for 24V/960AH versus the original idea of 800AH.
If he properly parallels his packs and matches up the BMS setting, it is unlikely that issues would occur. There is, of course, a Catch though, The ability to charge the bank within the Hi & Lo Sun Hour days (ok easier in Texas due to location but still a consideration). Will he have enough Panels & SCC Amperage to charge the entire bank ?

Taking the Lowest Common Denominator here which is the 200AH packs. I'll assume they are standard LFP used for storage, so most likely 1C Max Charge Rate and probably 1C Max Discharge rate. That's a lot of required solar juice.
 
I'd flip it the other way.
He ordered 32x 200AH cells. Got 16x 200AH & 16x 280AH, the 280's ar a Bonus of extra AH's and especially if they did not charge him the extra for 280 over 200.

2 Packs of 24V/200AH + 2 Packs of 24V/280AH for 24V/960AH versus the original idea of 800AH.
If he properly parallels his packs and matches up the BMS setting, it is unlikely that issues would occur. There is, of course, a Catch though, The ability to charge the bank within the Hi & Lo Sun Hour days (ok easier in Texas due to location but still a consideration). Will he have enough Panels & SCC Amperage to charge the entire bank ?

Taking the Lowest Common Denominator here which is the 200AH packs. I'll assume they are standard LFP used for storage, so most likely 1C Max Charge Rate and probably 1C Max Discharge rate. That's a lot of required solar juice.

Yep I agree - I talked him OUT of sending the 280's back for 200 .... no reason at all he can parallel them and be fine ... YEP on the additionakl solar panels required and another SCC ... he can get used 355 panels for $90 and easily add another EPsolar 40A - and then run his RV for probably a week with no sunshine -- actually probably much longer .. LOL ...

YES to the sunshine in Texas -- although heat kills us (and solar) ... yesterday it was 108 ... Heat Index of 116 ....I did most of my "tech" over the phone giving ppl good advice (or poor excuses on why I am not coming out in that heat)
 
Back
Top