diy solar

diy solar

Parallel Overkill BMS Success

Hey Everyone
Sorry for the late update, early June I suffered a heart attack just after my second set of cells arrived, requiring triple bypass. All is good now, built the second pack, removed second BMS from first pack, so I have now just one BMS per pack, and the two pack in parallel and finished the cabinet reno's. We camped since and the system is working great, using 11% of the 560 ah capacity per day and my current 185 watts of solar nearly fully recovered. I'm very pleased with the performance, and I'm now coaching 2 of my camping friends on their builds. I have the trailer in storage now, turned the system off, and removed the batteries for the winter. Here is a picture of the finished cabinet.
 

Attachments

  • BF9A9D14-765B-4DFC-B47E-FC89BC1474C1_1_105_c.jpeg
    BF9A9D14-765B-4DFC-B47E-FC89BC1474C1_1_105_c.jpeg
    199.2 KB · Views: 12
Last edited:
Hey Everyone
Sorry for the late update, early June I suffered a heart attack just after my second set of cells arrived, requiring triple bypass. All is good now, built the second pack, move, so I have now just one BMS per pack, and the two pack in parallel and finished the cabinet reno's. We camped since and the system is working great, using 11% of the 560 ah capacity per day and my current 185 watts of solar nearly fully recovered. I'm very pleased with the performance, and I'm now coaching 2 of my camping friends on their builds. I have the trailer in storage now, turned the system off, and removed the batteries for the winter. Here is a picture of the finished cabinet.

Looks good. Glad to hear you're still alive and kicking.
 
Hey Legends.....I've started building a very modular battery. I've looked high and low for info regarding the use of two Overkill BMS modules. The inputs/outputs on the left are a keyed 120A Anderson connector (Top Left), then 2 x 50a input/output on each case. Each case is a 12v (4 cell) 100a bty. I'd love to have the ability to use two enclosures when/if I need them. Basically stack em' up.

Is this achievable?


1652076937289.png
 
It looks like you have them in series? I don't believe they can be used this way (I think I read parallel only?). Hoping others will chime in.
 
It looks like you have them in series? I don't believe they can be used this way (I think I read parallel only?). Hoping others will chime in.

Lol, would you accept being tired as an excuse? Either way......I wander what the outcomes of the cable being incorrect. I guess the BMS would detect an over voltage situation and cut out? or something gets a bit Smokey. Someone also suggested I put a large Diode in on the 120A connector pos input. But I am not as smart as some of you guys so happy to take advice....

1652154528379.png
 
No, the BMS wouldn't do anything. You would end up with a 24 volt battery bank. It can be done, but there are issues with putting BMS in series. The batteries would likely stray away from each other in both voltage and state of charge.

If you need a 24 volt battery then build a 24 volt battery with a single dedicated BMS. (I know you're not building a 24 volt battery)
 
@Steve_S, @DerpsyDoodler , and @Dzl
As to the reasoning, it was not specified... He just said not recommended. I posted here about it as there seemed to be no information about doing this, besides the one video from Will P. about the two Dalys in parallel. Everything I'm seeing in bench testing is coming out fine.
I'll have the whole system up and running this week.

Let me translate this into plain English Layman version...

'...it is not recommended'

Definition:
'I don't really want to support it if it has a problem or doesn't work right if you do decide to do it'


BTW, I now have 6 of the OverKill 120a 4s BMSs in parallel (4s6p, 1680Ah, 24-cells) and it's working fine for me so far. The SoC seen on each BMS are always within 1% of each other, and it agrees with the SoC percentage I see on the BMV-712 so far.
 
Nothing wrong with paralleling batteries.
It's actually the recommended way to increase capacity.
 
I built two 280 ah battery packs, each now have their own BMS, connection is thru 175 amp Anderson plugs then the positive to switch then fuse and + buss Bar and the negative is to the shunt then to - buss bar.
All cables are equal length, allowing both to draw down and charge close to equal. I have been using it this way with no issues.
 

Attachments

  • IMG_1360.PNG
    IMG_1360.PNG
    1.3 MB · Views: 10
  • tempImageTVLzne.png
    tempImageTVLzne.png
    2 MB · Views: 11
  • tempImagetFiaRN.png
    tempImagetFiaRN.png
    1.7 MB · Views: 9
  • tempImage77BnOC.png
    tempImage77BnOC.png
    1.9 MB · Views: 10
  • tempImageMWvzas.png
    tempImageMWvzas.png
    2.1 MB · Views: 11
I built two 280 ah battery packs, each now have their own BMS, connection is thru 175 amp Anderson plugs then the positive to switch then fuse and + buss Bar and the negative is to the shunt then to - buss bar.
All cables are equal length, allowing both to draw down and charge close to equal. I have been using it this way with no issues.
Nice work.
 
Nice work.
On the weekend I added 600 watts of solar to the 185 watts I had. Now running two solar controllers, looking for easy boon docking this summer.
I still have the wires on the roof to clean up, as soon as it stops raining. Batteries are full so currently little demand on the solar.

Sorry some pics are sideways.
 

Attachments

  • tempImage0UGG2d.png
    tempImage0UGG2d.png
    2.4 MB · Views: 9
  • IMG_1379.PNG
    IMG_1379.PNG
    1.1 MB · Views: 9
  • IMG_1380.PNG
    IMG_1380.PNG
    524.3 KB · Views: 6
  • IMG_1381.PNG
    IMG_1381.PNG
    529.4 KB · Views: 9
Back
Top