Two years ago I was listening to Steven Harris on the Survival Podcast talking about how to build a home battery backup.
- Episode-1039- Steven Harris on Battery Back Up Systems Part 1 of 2
- Episode-1040- Steven Harris on Battery Back Up Systems Part 2 of 2
These episodes (and others interviewing Mr. Harris) go into great detail and are worth listening to. Subsequently, I went to Battery1234.com and bought the video series. While it covers the same material in the podcasts, it has useful photos and diagrams if you aren't familiar with working with electricity.
After bringing in our motorcycle batteries for the winter I decided to finally put my own together. The fundamental construction is identical to what it outlined in the podcast/DVD's with the small exception that I use more screwed down ring terminals than clamps.
I sized this system to charge primarily low-power devices for use in an extended blackout. My primary concerns are around having our cell phones, handheld radios (for weather and emergency services monitoring), LED lighting and tablets operational. If the coaxial lines are still operational, I'd also like to be able to power my modem and be able to work remotely.
- P3 P4400 Kill A Watt Electricity Usage Monitor
I wanted to monitor the entire system usage while on-grid and usage off-grid. Also useful around the house to measure actual current draw.
- Peak PKC0CU Intelligent Battery Charger
I believe this model is no longer made. I already owned this charger but if you don't own one use one of the Schumachers listed on Battery1234.com.
- EverStart Group Size 29DC Marine Battery (101 Ah @ 1 amp)
- Moeller battery box
- 12v Outlet
This is a cheap and incredibly useful piece of the kit. Clamp 12v outlets can be used to pull small charges off of car/marine batteries without needing to idle the vehicle, which is significantly more efficient. You could charge your phone several times without impacting the ability of your vehicle to turn over. Even if you don't build a backup system, buy one of these to use on your car and keep a 5 gallon can of gas sitting around to keep your phone powered for weeks.
- 12v four port replicator
- Battery charge monitor
- 2.4 amp USB charger
Pretty much any 12v car charger will do, really. The Cobra Inverter also has a USB plug for charging.
- Cobra 800 Watt Inverter
This inverter is over-sized for my needs but could be "borrowed" to temporary run my refrigerator in a summer blackout if wired directly to a running vehicle. The price difference from the 400 watt was small enough it was worth the extra utility.
- Battery hydrometer
Also pictured on this cart are the two AGM motorcycle batteries on Schumacher 1.5 amp trickle chargers. These are unconnected to the system, though hypothetically I could use the same gear to stretch another 20 backup amp hours out of them.
The battery came from Walmart slightly discharged and needed to sit on the 12 amp charge mode for a few minutes. In maintenance mode it floated on and off before it "settled" into a quiet state. It's sitting in my office, but so far the fan hasn't run excessively. If it becomes annoying, I may move it to the basement or swap it for a silent charger that uses a heat sink instead of a fan. Alternatively, I could swap the charger with a silent float charger when it's full and keep the 3-stage on-hand to bring it back.
This project is very simple. Steven Harris has done the hard part of testing all the products and assembly is very straight forward. If you aren't familiar with checking levels of FLA batteries, you should brush up on that (included in the videos) or opt for the AGM's.
In the future I may expand this to a second battery as the overhead cost of a second is minimal. I may expand the life of this battery by keeping more gasoline on hand and using the vehicles as a generator, but that's beyond the scope of this article.