Why Grid charge 12v backup systems and how much it cost?

Our house is on the edge of a remote hamlet, and we do not want to draw any attention to the technical capabilities that we are building into it.

Just over 4 weeks ago we installed the first stage of our 12v back-up power system.

We’ve opted to maintain charge in the 2 x 125ah deep cycle accumulators using a vehicle smart charger. We also have a solar charge regulator pre-wired in, so that our solar panels can be connected up in a grid down situation.

We have opted for this system as it is very discreet and does not announce our PV charging capability by the presence of a large array of panels on the roof.

To control the charging arrangements I have constructed a small control panel, which incorporates a power consumed watt meter. This is there mainly to gauge the amount of energy we are harvesting from the PV array, when its deployed. But as currently configured, it tells me how much power is being used to keep the batteries float charged.

The answer is that since installation, this arrangement’s running cost is equivalent to running a 60watt light bulb for a around 15 minutes per day. This includes the power drawn by our alarm system, which is now hard wired in.

So we now have the best of both worlds. Currently the system is supported by grid services, but is easily switched to off grid PV array charging.

For anyone with a grid tied PV array on the roof this system can be charged free of charge at the present time, providing backup for grid down. With an appropriate charge controller, power generated from individual PV cells on the roof could be drawn down and regulated to keep the accumulators charged in a post SHTF scenario.

Best cost grid powered smart charge controllers were found at Lidl and Aldi. (£15.00) These are very well made auto smart chargers that have various modes for use with both 6v and 12v batteries, of large and small capacity. They provide rapid charging of depleted batteries, pulse charging of excessively discharged batteries, as well as maintenance float charging of fully charged cells.