Building a battery box. My first battery project.

Torben J

New Member
Joined
Feb 21, 2021
Messages
29
I purchased 24 Pack 3.2v 25ah Lifepo4 Topband Prismatic and want to build a 2000W battery box. See attached picture. the 3P bus bars are not installed. What Gauge should I use? I'm using the following bus bars.
I'm planning an 8S 3P setup. 24V. Added a DC Stepdown transformer to 12V for 12V Accessories.
2000 W Inverter, Using this battery box, I really like the way it's set up.
My Charger is AIMS Power 12/24V
I have one 300W portable solar panel, that comes with a charge controller.

I have a few questions. I thought 24V would be better than 12V due to the lower Amps, however, I'm concerned about the BMS only monitoring 3 sets of 8 cells. What gauge cables should I use for the 3P connections and do I use a combiner bus bar?
For BMS I'm considering Overkill Solar 8s BMS 100a LifePo4. I have not found a 4s BMS.
I could go 12V and 4S 6P. Then I would need a 200a Daily BMS like this one not as good ad Overkill Solar, but Overkill Solar does not have a 200a BMS. I can switch out the Inverter with Amazon.

When I topped 8 cells with my charger they did drift some. I need to top balance the batteries first 24P. All cells arrived with a 3.29V charge.

Potential usage portable power, and emergency power. Might add solar panels and a charge controller at some point in the future.
Want to build a whole-house battery bank in the future.

The current project is below.
Lifepo4 Topband Prismatic..jpg Battery Box.jpg
 
Last edited:

ThomasSun

New Member
Joined
May 25, 2022
Messages
11
I purchased 24 Pack 3.2v 25ah Lifepo4 Topband Prismatic and want to build a 2000W battery box. See attached picture. the 3P bus bars are not installed. What Gauge should I use? I'm using the following bus bars.
I'm planning an 8S 3P setup. 24V. Added a DC Stepdown transformer to 12V for 12V Accessories.
2000 W Inverter, Using this battery box, I really like the way it's set up.
My Charger is AIMS Power 12/24V
I have one 300W portable solar panel, that comes with a charge controller.

I have a few questions. I thought 24V would be better than 12V due to the lower Amps, however, I'm concerned about the BMS only monitoring 3 sets of 8 cells. What gauge cables should I use for the 3P connections and do I use a combiner bus bar?
For BMS I'm considering Overkill Solar 8s BMS 100a LifePo4. I have not found a 4s BMS.
I could go 12V and 4S 6P. Then I would need a 200a Daily BMS like this one not as good ad Overkill Solar, but Overkill Solar does not have a 200a BMS. I can switch out the Inverter with Amazon.

When I topped 8 cells with my charger they did drift some. I need to top balance the batteries first 24P. All cells arrived with a 3.29V charge.

Potential usage portable power, and emergency power. Might add solar panels and a charge controller at some point in the future.
Want to build a whole-house battery bank in the future.

The current project is below.
View attachment 96861 View attachment 96862
Usually we recommend you connect the battery cell in parallel first and then in series. So just 1pcs BMS is enough and higher safety design.
 

740GLE

Solar Addict
Joined
Apr 30, 2021
Messages
1,138
Agreed, 4S3P with one BMS is bad mojo.

Downside is going to find an easy way to parallel 3 cells cleanly, custom bus bars maybe needed.
 

vtx1029

Solar Enthusiast
Joined
Mar 30, 2020
Messages
145
IMO the best way to do this is to capacity test each cell on its own then pair up the 3 cells in parallel so you have 4 packs of equal capacity. Then connect in series.
 

willc99

New Member
Joined
Jun 10, 2022
Messages
17
I am considering a DIY battery box and wanted to get feedback. I was thinking fire retardant boxes maybe out of cement backer board or similar cement material. I want the fire to have time to set off the fire alarm before it burns the house down, if you know what I mean! ;-)
 
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