DIY Lithium 18650 Portable Camp Battery Box

#1
We run AGM dual batteries permanently mounted in the Ranger and Camper Trailer but there are times when we need portable power, and by portable I mean something people other than myself can lift and use.

The goal was to build something small and light with enough usable AH to be practical that could recharge devices, run laptops, power lights, air pumps etc and run the water pump on the shower and maybe a fridge for a few hours down the park.

What I have ended up with is a very light (around 3kgs) 21Ah useable box with 2x 5v / 2.4 Amp USB, 1x Engel, 1x Cig, 1x 240 Outlet using a 24v 600w Pure Sine Wave inverter. The battery I built using 18650 cells and is 24v so I have a BMS on it, a DC / Solar Charge controller feeding it that can step up and step down the power as required for the battery, a 24v to 12v buck converter and a shunt to measure whats coming out of the battery.





It got it's first trial by fire over the Chrissy break and didn't miss a beat, will start working on another one soon.
 

typhoeus

Well-Known Member
#2
We run AGM dual batteries permanently mounted in the Ranger and Camper Trailer but there are times when we need portable power, and by portable I mean something people other than myself can lift and use.

The goal was to build something small and light with enough usable AH to be practical that could recharge devices, run laptops, power lights, air pumps etc and run the water pump on the shower and maybe a fridge for a few hours down the park.

What I have ended up with is a very light (around 3kgs) 21Ah useable box with 2x 5v / 2.4 Amp USB, 1x Engel, 1x Cig, 1x 240 Outlet using a 24v 600w Pure Sine Wave inverter. The battery I built using 18650 cells and is 24v so I have a BMS on it, a DC / Solar Charge controller feeding it that can step up and step down the power as required for the battery, a 24v to 12v buck converter and a shunt to measure whats coming out of the battery.





It got it's first trial by fire over the Chrissy break and didn't miss a beat, will start working on another one soon.
>. . . Your obviously a sparky, . . with way more skills than most of us,o_O . . when are you going into mass production?
 

G_ute

Active Member
#3
Very cool.
How many cells and are they balance charged? Reclaimed batteries or new? Also why 24V (aside from the inverter) ?
(FYI, Tesla Model S contains 7104 of these cells o_O )
 
#4
Would you believe I am actually an IT Exec :) but if I was ever going to be a trade it would have been a sparky for sure :) I will take that as a compliment thanks.
 

Les PK Ranger

4x4 Earth Contributer
#5
Nice.
What did it cost all up to make, if you don’t mind sharing.

Made the battery ?
Very handy.
You say 21amp/hr useable, what is total amp/hr to achieve that ?
Or the % SOC you can run that down to ?

I was at Enirgi a couple of days ago and saw their L3000+ lifepo4 130amp/hr.
Very nice, was at shoulder height on the shelf and could pick it up with one arm :)
Still, a tad over $1500 trade price, maybe one day when a camper is brought into our camping needs.
Retailers seem to be around the $1950 mark for that bsttery.
 
#6
Very cool.
How many cells and are they balance charged? Reclaimed batteries or new? Also why 24V (aside from the inverter) ?
(FYI, Tesla Model S contains 7104 of these cells o_O )
56 Cells, in 7s8p config. I went with 24v as 18650 cells don't do 12v very well. 3.635v nominal * 7 = 25.44v where as if you try for 12v system you at 3s you only get 10.90v or at 4s you get 14.54v so a 24v 7s battery worked out best.

For this build I am using brand new LG MJ1 18650 cells that are 3500mAh. My next build is using reclaimed Cells that are coming in at an average of 3500mAh's after testing.



I have reclaimed something like 900 cells so far and they are working out pretty good. The BMS makes sure the cells are balanced and can't be over or undercharged with cutouts.
 
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#7
Nice.
What did it cost all up to make, if you don’t mind sharing.

Made the battery ?
Very handy.
You say 21amp/hr useable, what is total amp/hr to achieve that ?
Or the % SOC you can run that down to ?
I will have to do some quick math but my gut feel is it would owe me about $350-400 in parts and more than 1 bottle of scotch. The 3500mAh cells in 8p give me 28AH total, being lithium you can safely discharge them to 80%. So I have the cutoff set to 21AH as that's 75% leaving 5% margin of error. It never got to anything like that.

I used Pure Nickel strip with a home made spot welder to build the pack and then soldered the BMS up to it. Here are some pics of the test pack I did to test the welder on some dead cells.



 

Les PK Ranger

4x4 Earth Contributer
#8
@idiomatically i think you’d get on well with my IT son in Melbourne.
He does this sort of stuff a lot :)

(FYI, Tesla Model S contains 7104 of these cells o_O )
Ah but which one ?
Son has model x, had loan S, P85D the other day while his was getting a little job done at Tesla Richmond.
Wow, I had to tell him before accelerating even 3/4 pedal so he could put his head back on the headrest voluntarily :D
 

G_ute

Active Member
#9
My brother (in USA) has an old Tesla Roadster and his son has converted a Chevy ute to electric and is currently electrifying a VW Kombi (also a ute or 'doka')
Smart nephew!
Seems they dont have so many regulations to jump through in USA and have ready access to old electric car batteries.
 
#10
I wish I could justify a Tesla I really really do however my wife and I both have company cars supplied and when we aren't in them we like to be in the Ranger off on a beach or in the bush some where.

I get to drive them occasionally in the US when I am there for work, and a bunch of mates have them. They are weapons. I am trying to convince the boss I should get a Model 3 as my next company car :)
 

mauriceb

Well-Known Member
#12
12v 18Ah and 8.6 Ah Simple battery pack with cig sockets I use around home and always one on trips. Easy to charge from vehicle . I have many torchs that use the Lithium 18650 bats. Many of the ebay one's a false rated so I only buy the Panasonic's. Three of these 18650 cost as much one 18Ah Agm in photo
IMG_20190108_171829.jpg
 

Triton14

Well-Known Member
#14
Don't those thing need circuit protection otherwise they can be pretty explosive!
I have a few things that use 18650's & I pulled a laptop battery apart to use them but then discovered the weren't individual protected so didn't use them.
What do you use on the bank for overcharge protection?
 
#15
What do you use on the bank for overcharge protection?
There is a battery management system connected to the battery that prevents the battery being over charged and over discharged and keeps the battery balanced. On reclaimed cells where I don't know the origin I fuse each individual cell as well however with brand new cells like in this box there is no real need.

Yes without a BMS to control things these can be akin to a bomb. The dc / solar charge controller I have charging it is also matched to the BMS ie it won't output more then 4 amps @ 24v as another layer of protection. On the load side I have the shunt set to shut down at over voltage and under voltage as well which is another layer of protection and finally the entire thing is fused with narva manual reset fuses.
 

Triton14

Well-Known Member
#16
There is a battery management system connected to the battery that prevents the battery being over charged and over discharged and keeps the battery balanced. On reclaimed cells where I don't know the origin I fuse each individual cell as well however with brand new cells like in this box there is no real need.

Yes without a BMS to control things these can be akin to a bomb. The dc / solar charge controller I have charging it is also matched to the BMS ie it won't output more then 4 amps @ 24v as another layer of protection. On the load side I have the shunt set to shut down at over voltage and under voltage as well which is another layer of protection and finally the entire thing is fused with narva manual reset fuses.
You sound like you well versed/trained or even this is what you do for a crust??

Looks fantastic & not to put a downer on this thread but I don't thing you should try this at home unless you have a degree in electronics or are an electrical engineer!
 
#17
Let's go with well versed, have just done a lot of reading and understanding over the last 12 months doing the exercise and I had a pretty good understanding to begin with doing 12v systems for my rigs.

It's certainly not something you want to jump into if you don't understand the theory and how bad it can end up if you do something stupid or don't use the correct safety measures.
 
#18
I'm looking at doing something similar with reclaimed 18650 cells.
Just wondering where you sourced the box/plugs/fittings etc? Because it looks really good! better than a lot of the hack jobs I've seen around.

Cheers,
 

G_ute

Active Member
#19
Found this video of a very cool battery pack (ex-Chevy Volt - Holden Volt?) in an ammo box.
Plastic may be better though...

 
#20
I'm looking at doing something similar with reclaimed 18650 cells.
Just wondering where you sourced the box/plugs/fittings etc? Because it looks really good! better than a lot of the hack jobs I've seen around.

Cheers,
The box I got locally from Evolution Gear, it's not perfect but pretty close. Tractor Supplies version in the US is very similar but a bit better however the price to get it here was a hard call so I went local. The switch panels are Cllena versions and I got them from Amazon and the other stuff came from AliExpress.
 
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