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Portable Camp Battery Box
Firstly I'd like to thank all the people that have contributed to the site, without the shared knowledge and the openness of others I would not have been able to have a crack at this project.  It was my first and I consider myself still very very green.  A special shout out to Geek for putting up my private messages and his support.

A bit about the box;

42 cells (LG MJ1 3500mAh) in 7s6p w/ BMS for 24volts 21AH 
10-30v MPPT Solar / DC charge controller
600w 24v pure sine wave inverter
24v intelligent shunt
24v to 12v buck converter
12v gauge
dual 5v 2.1amp USB
12v Engel and Cigerette sockets
240v outlet

All individually switched and fused.

I spend what little free time I have camping, so our main offroad power comes from the dual battery 220AH AGM setup in our 4wd and camp trailer with a 200w panel.  However this isn't portable and often we have people with us that need some power so I wanted something that I could move around the camp and also use to power the hot water shower pump as well as charge my sons laptop so he might actually come with us.

I took a few months to build it as I had a lot to learn, parts to source and I built and tested my spot welder on some dead cells.

This is an old 330 cracking amps car battery, using a high amp motorcycle solenoid, momentary switch and pure copper nails.  I found this worked very well, the cells in the picture were my dead testing cells.  It took me a while to dial it in and find actual pure copper nails but the end result now is perfect with the nickel I got from the UK.

I needed a way to charge / test the boxes step up solar / dc charge controller so I stole an old xbox 360 power supply we had in the cupboard and modified it for my purpose so at home this is what I am using to charge the battery.

I now have 600 old laptop batteries in my shed so I am planning on a v2 in a bigger box to accommodate the lower capacity cells, and will start plans for a power all setup too.  This was a nice introduction to the theories and a solid learning exercise.  Thanks again everyone.
lordxenu, Korishan, jdeadman And 1 others like this post
that look pretty nice,

I am about to build something similar still banging my head if I should go 12 or 24v.

Do you have the 18650 inside those cylinders?
so that solar controller take 12v and convert it to 24v.
Can it also charge a 12v battery or only 24?

Does the 24v intelligent shunt read current going into the battery or only out?
Do you have the 18650 inside those cylinders?

The cells are in the standard cell holders like in the pic from my test weld pack, and then I have wrapped the battery and bms in a heat shrink sock leaving 2 ends open so it can breath. I have also got the shunts temp sensor on the battery so I can monitor it.

so that solar controller take 12v and convert it to 24v.

yes the charge controller will step up the voltage to 72v on that model, you can set what you want it to output.  I have mine set to 28.7v

Can it also charge a 12v battery or only 24?

It's range is 24v to 72v from memory.  So I wouldn't use it with a 12v battery pack, that said 18650's don't lend themselves well to 12v from my understanding.

Does the 24v intelligent shunt read current going into the battery or only out?

The shunt reads the draw coming out of the battery, however the charge controller tells me the current going into the battery.
I was looking from my phone and for some reason they looked huge so I thought you have them inside some type of big cylinders.
as there only 8 visible cells.

I have read that power supply are not recommended for solar controllers have you notice any issues heat specially on the power supply.

All this time I been confused with the lipo fire and all lipo chemistry it seem that the good brand Li-ion wont turn into flame so easily that why I ordered Lifepo4.
I might give Li-Ion a try.

That charge controller seem pretty nice. pretty much as advance as some hobby charger the only think missing is build in balance connector to tell each cell voltage.

Thank for the details.
The BMS handles the cell balancing, and if I divide the voltage the shunt it showing by 7 it will tell me the voltage of each cell, ie if it's 28.5 I know each cell is 4.07v for example.

lol yeah no big cylinders, those cells in the picture are just the dead test cells I used to test the spot welder. The real pack is much bigger.

I don't think I would use a psu with any of my Victron MPPT solar controllers as they are not made for it, but this particular step up controller is and it stays nice and cool as does the PSU I use with it.
I just lost faith in analog BMS I much prefer a display LCD to show each cell voltage live.
Last BMS I had to yank out as the battery was only providing 1Ah out of 20Ah it was super out of balance.

I found this but it seem to expensive to have on each battery pack, but it should work for just a portable power box.

good to know that particular MPPT with a regular power supply is working great, I like that
Such tiny pictures.... I can hardly see anything.

I'd love to see a schematic of this at some point. Building a portable battery box is on my list.
Arrow  See My DIY PowerWall Build here Arrow
Thanks for sharing. I plan to build something like this over the weekend.

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