DIY Battery Box

[ConcordCarlos1]

Why ? Power my ARB fridge in the back seat of my truck when not toting the FWcamper . Fishing trips a good distance from home, and like to get my catch frozen in their vacuum seal bags on the way home.

What ? Milwaukee PackOut top box , two Chins 20ah LifePo4 batteries in parallel , Victron DC to DC (12-12 30) .

Power in, Anderson two position flush mount into the Victron. Ran a dedicated run from my switchpros to the back seat of the truck . I also carry a 12v socket set up Incase I need to charge from someone else’s vehicle. Not ideal since that’s small wire gauge.

Power out , 12v socket for the ARB fridge. Will be wiring the second Anderson position to a fuse , then to the battery and changing ARB connector to an Anderson. This second position will also support solar in, MPPT will have to be attached/inline with the panel since there is no room left in the box for the MPPT.
USB and USB-C to charge phones and tablets .

Overnight test of the fridge set to 10 degrees. When the compressor is running , voltage is showing 12.9 . When it cycles off, volts bounce back to 13 to 13.3 range. May add a Victron Shunt for SOC monitoring. Too cold in my garage to do a realistic test right now .

 

[jonyjoe101]

I would get a tk15 instead of the victron coulombcounter. Its about 40 dollars on ebay for the 50amp model. I been using them for years on my 220ah lifepo4 very accurate for the price. You will need it especially on a 40ah lifepo4.
On my 12 volt fridge when the battery starts getting low the fridge starts cycling back and forth due to the input voltage drops too much. I had too install a boost buck converter set to 13.4 volts to power the fridge even when the battery starts running low, it stabilizes the voltage going into the fridge. Also if you have similar problems you can run the fridge through an AC inverter.
For mppt controllers I recommend the makeskyblue 60A(about 130 dollars), its what I been using for the past 3 years to charge my 220ah lifepo4. It has voltage calibration this will make sure the controller reads the same voltage as the battery terminals. And its also suppose to prevent voltage surges if the battery BMS activates. With 40ah lifepo4, they will charge quickly and if the BMS activates any voltage surges (up to 20 volts) will destroy any 12 volt devices connected to battery. Most pwm / mppt controllers don't have protections to prevent voltage surges. The makeskyblue 50/60 amp mppt are the only ones that advertise they have that kind of protection.

TK15 coulombcounter

 

[ConcordCarlos1]

I would get a tk15 instead of the victron coulombcounter. Its about 40 dollars on ebay for the 50amp model. I been using them for years on my 220ah lifepo4 very accurate for the price. You will need it especially on a 40ah lifepo4.
On my 12 volt fridge when the battery starts getting low the fridge starts cycling back and forth due to the input voltage drops too much. I had too install a boost buck converter set to 13.4 volts to power the fridge even when the battery starts running low, it stabilizes the voltage going into the fridge. Also if you have similar problems you can run the fridge through an AC inverter.
For mppt controllers I recommend the makeskyblue 60A(about 130 dollars), its what I been using for the past 3 years to charge my 220ah lifepo4. It has voltage calibration this will make sure the controller reads the same voltage as the battery terminals. And its also suppose to prevent voltage surges if the battery BMS activates. With 40ah lifepo4, they will charge quickly and if the BMS activates any voltage surges (up to 20 volts) will destroy any 12 volt devices connected to battery. Most pwm / mppt controllers don't have protections to prevent voltage surges. The makeskyblue 50/60 amp mppt are the only ones that advertise they have that kind of protection.

TK15 coulombcounter
View attachment 810997

I have a Victron Shunt that I took off another project, so I’ll be using that one if I decide to add that. I did look at the one you suggested above, and would take up less space in the box which in already limited. The fridge is set to the lowest voltage level possible. For the most part, the battery box will be keeping the fridge running during extended stops and an overnight or two. I previously used a Yeti 400 in similar fashion (32ah SLA) and it kept the fridge running under very hot conditions and frequent fridge openings for adult beverages.

 

[mep1811]

Nice. DIY so much cheaper and better than most battery packs. Just without the fancy gauges.

 

[ConcordCarlos1]

Nice. DIY so much cheaper and better than most battery packs. Just without the fancy gauges.

Speaking of fancy gauges….thinking about replacing the volt meter with the Bluesea OLED one. The cheap one I used is pretty dim and hard to see.