Make your own 400Wh portable power battery for less than $100

I made this 12v 35Ah (420Wh) portable power battery with left over parts, but you can do it for $100 to $150 (or more) depending on options you want, such as solar charging, vehicle charging vs. 120v charging, adding a 120v power inverter, etc.




The battery is based on a low cost 12v 35Ah deep cycle gel cell made for mobility scooters and trolling motors like these:

Mighty Max Battery ML35-12 - 12V 35AH U1 Deep Cycle AGM Solar Battery Replaces 33Ah, 34Ah, 36Ah Brand Product

$75 Mighty Max Battery ML35-12 - 12V 35AH U1 Deep Cycle AGM Solar Battery Replaces 33Ah, 34Ah, 36Ah

https://www.amazon.com/dp/B00K8E0WAG/ref=cm_sw_r_cp_api_i_0h5JDbNJ4P8G9

The case is a $9 HF plastic ammo box with a built-in handy cover storage area for cables, connectors, etc. I cut about 1/3 off the side of the tray and used it to mount the switch panel and 12v and USB charging plugs to: And I added a switch, voltage meter, USB power plugs and a cigarette lighter plug port like this to it:

Linkstyle 4 in 1 Charger Socket...

$18 Linkstyle 4 in 1 Charger Socket Panel, 12V 4.2A Dual USB Charger Socket Power Outlet & LED Voltmeter & Cigarette Lighter Socket & LED Lighted ON Off Rocker Toggle Switch for Car Marine Boat RV Truck

https://www.amazon.com/dp/B07JHH5YP4?ref=ppx_pop_mob_ap_share

Also adding a 13.8v step up transformer to run my refrigerator and drone charger as they are designed for slightly higher voltage than the 12v a automotive battery provides after the engine turns off: DC-DC Boost Module 9-14V to 13.8V...

$21 DC-DC Boost Module 9-14V to 13.8V 10A 138Wmax Power Supply Converter

https://www.amazon.com/dp/B01AW1JKO8?ref=ppx_pop_mob_ap_share


This project is in progress still (adding fuses and additional plugs) so I will add more info to the build, including how to make just the basic version with the parts listed above and just a few more.

 

Good info and thanks for the links.

How are you charging it while on the road? Did you make a pigtail for the back of the alt that goes to your DC-DC charger?

 

The plug on the lower left front of the case near the DC to DC charger is the input for powering the charger when I’m on the road. It automatically switches off if the main battery runs low or the auxiliary battery is fully charged. There’s another plug inside the box for when I’m solar charging it too. I am using temporary wires from the batteries, will be running permanent ones soon.

I can unplug either of the charging power input wires if I want to move the battery somewhere else.

 

Just ran a pair of 4ga wires from the auxiliary battery in the engine bay back along and inside the passenger side frame to the rear passenger cubby where I will use a Blue Seas fuse block as a junction for accessories including the portable battery. Pics soon...

 

Following. Need something like this for my little Scamp travel trailer. Would be great to put in front right behind the propane tank.