France in Focus

My OH when he was working as a mechanic had a work mate who had installed a system in his house where all the lighting was run off of car batteries.

I was thinking that with the cheep small solar panels you can buy for running water pumps and similar, that if one charges a battery with solar power and uses those batteries to run lighting, you'd have free light.

Does anyone have any idea whether or not this is feasible? It sounds too good to be true so I'm sure there's probably something I haven't thought of, obviously I realise we'd have to run it as an additional/separate system.

I thought they generally ran them at 48V - so put four in parallel.

Also, I think car batteries are the wrong type - I think you need leisure batteries.

You can also get 48v fridges and freezers, water heaters and other items as well as lights - but not cheap.

So that hot plastic box in the hallway looks bad?

Char, in the early days of solar panels I installed in so called "sites isolés"(jardins familiaux) without acces to the grid old car batteries (left overs from heavy diesel cars), voltage/charge regulators and one or more solar panels. Standard car bulbs and just enough power with one 90 amp battery to feed an old black/white tv (CRT type) for one football match. With the leds of today the power consumption goes down, at least 75% less energy than incandescent lighting. Without the need to feed a cathode ray tube a modern tv is not very power hungry anymore. Feeding a laptop from a 12 V DC circuit with a simple low-cost converter is not any problem as explained here.

In the late 80s there was a guy who had installed several large car batteries in parallel, four solar panels and an expensive heavy duty marine type converter (12V DC --->230 V AC) to run a lave linge. It was already doable (separate wiring) and today (tiny houses etc.) it is much easier.

If you want 48V from four 12V car batteries, they would need to be wired in series not parallel.
Michael

michael86 wrote: ↑Sat Nov 27, 2021 5:12 pmIf you want 48V from four 12V car batteries, they would need to be wired in series not parallel.
Michael

Thanks. Yes. Not got my physics head on today!

It's a very interesting idea. Blonde question....how long would the batteries last before needing replacement? Car batteries here in France don't seem to last particularly well. The same goes for solar panels. Have they reached a stage of development that makes the outlay viable?

@ Quicksilver, giving an old car battery a second life is a low-cost solution. Even when a car battery loses some of its capacity, problems to give the starter motor enough power on a cold winter morning (CCA - Cold Cranking Amps) it doesn't render it totally useless. A car battery is of course not the perfect solution for the more moderate use in a solar power installation, you would like to see deep cycle batteries there.

Longivety: I once had a VARTA car battery doing its best for almost ten years, also one useless after three years (no, not Lucas). Outside temperatures, most batteries prefer a moderate climate, how many start/stop cycles and the design of the battery etc., the outcome will be different. The special solar batteries should last about ten years.

During the power cuts in the 70s I ran our house lighting off car batteries - brings back the memories.

I have a couple of car batteries that must be going on for 8 or 9 years old that I use for various "portable" sources, jump starting mowers, emergency lighting, water pumps, etc. They were becoming too weak to start a car in winter so were replaced. They are still very useful and get a quick charge from the mains every few months. The amount of power available from the smaller cheaper solar panels is not terribly useful in the grand scheme of things, and if you up the expenditure to get larger panels you then have the additional cost of charge regulators, etc.

Leisure batteries are better than ordinary starting batteries for this purpose but ideally need to be "Deep Cycle" ones to survive erratic charge currents and occasional extreme discharge abuse. These add even more to the so-called cheap power alternative.

Look on this website "Bardens UK" been providing off grid solutions for many years.