DIY battery backup system

[Joe Rice]

I was thinking of getting this Ecoflow battery backup for my system but, seeing the price ($2300), I started wondering if I could save some money by DIY'ing it.

I wound up putting together a system that cost about $1200 and has 25% more capacity (5120 Wh vs 4096 Wh) than the Ecoflow.



Battery and charger: $750


Inverter: $230



Transfer switch: $82

Extension cord (optional): $22

Surge suppressor power strip: $97



There isn't much to assembling it. Just connect the charger and the inverter to the battery, plug the "inverter" input of the transfer switch into the inverter and the "shore power" input into a wall outlet, and plug the power strip into the "output" cord of the transfer switch. Now anything plugged into the power strip is battery-backed up.

Well, there is one small complication. When the inverter is used in this manner it's important to connect the neutral to the ground in the inverter. To do this you will need a 2" length of 12 or 14 gauge wire, stripped on both ends. You'll need to bend it into a horseshoe shape and connect the N and PE terminals in the orange AC Output terminal block.

I used a 51.2 volt (nominal 48 volt) battery but the system would work just as well with a 12 volt or 24 volt battery. You would just need to get an inverter that matches the voltage of the battery.

 

[afboundguy]

I've been looking into stuff like this as well and found a bunch of great generator YouTube channels and would love to make something similar as wife doesn't seem thrilled with the idea of running the generator when we are sleeping or if I have to head to work.

 

[salty_dog]

I too have been thinking about this since the billzard of '26.
My experience with battery back up is basic but having redundancy is probably the best bet. I have a Predator generator and electrician wired a plug to power the house. Used ~1x a year for past 11 years. No issues, starts in 2-3 pulls. I have a few LiFePo4 batteries of various sizes, that are usually being used in something else like a powerwheels or something. Or run a scanner/weather radio. So I know for sure if they're working or not. Then connect to an inverter when I need it. With the tank back up I would definitely go with a commercial UPS.

I do have the small ecoflow river. But it does not do well as a UPS. After a day it shuts off, even when connected to the mains. After research, that model needs to be discharged to 80% to function as a UPS. I have no idea why. Needs to be connected via wifi to do this setting change.
I've not heard about this issue on larger models.

One cool thing is that the ecoflow is easily charged by any 12-24v source, battery, car, solar panel.
Comes with a cigarette lighter cable. And you can buy their solar cable which handles a range of voltage and higher amperage. The ecoflow has a 3rd wire on the adapter which allows communication with their batteries, so it won't charge a generic one. Maybe this could be hacked?
My plan is to get a medium sized ecoflow and 2 LiFePO4s. Then the generator can be run intermittently.