Thread: Solar panels not keeping batteries charged up. Need assistance to diagnose.

Originally Posted by Blknight.aus

...To test that properly you need to have either flat batteries or a dummy load that can draw the full output of the regulator.

What can I use for a dummy load? All of the batteries I have around here are charged up!

So, I have made a quick and dirty testing rig to draw more current. A couple of 50W halogen globes hooked up in parallel. In theory they should draw 8.2A.



And in practice they actually draw 8A!



The 7.2A going in is from my little CTek 7A charger.

Hey Dave,

You sure it's OK to run 10% of the capacity for a long term test? At 75AH a load of around 8A is close enough to 10%.

But I was doing some reading and found a company saying you shouldn't load up more than 5% of the capacity of the battery, which would make 4A a better test maybe?

Will I do any damage if I hit it with 8A for 20 hours? Or do I just stop testing when the voltage reaches a certain level, like 11.5V or something?

This may or may not be relevant but is a 30a controller adequate for 600W of solar panel, obviously 600W is max and probably not realistic ?

What have you got in your camper that you need 3 batteries for? The best set up is to have the least amount of batteries that you need with the most amount of charge you can get going into them. Work out what you draw in a 24 hour period, then what you need to replace that in an 8 hour period. I have a 100a/h deep cycle with only a fridge and LED lights running. Occasionally I'll have the tap on for 10-15 second bursts. I have worked out I need a 120w solar set up but I'm getting a 200w one. At the moment I have a generator with a 4amp charger running during the day and that is adequate.

If you have a dead cell a or a couple of lazy ones, then that battery will suck the life out of the other two. I wouldn't run 3 together anyway, takes way too long to charge them. I'd run each separately and switch between them so that when one needs charging, it won't take as long and you have 2 fully charged ones on stand by all the time.

OK - I haven't thought about having separate batteries and rotating them!

We have 3 batteries because I wanted about 200AH, so 75Ah x 3 = about the right amount. I can't remember how I got to the 200AH figure - it was 3 years ago!

We have a bit more than a fridge and lights; with a stereo and DVD player/TV, a 140L fridge, an 80L chest freezer and a lot of USB sockets to charge cameras and phones and laptops.

With 400W, I had hoped that things would be fully charged by lunch time! I don't reckon I am getting anywhere near 400W fed in though. The other 200W goes to the 24V truck batteries to keep them topped up.

Originally Posted by loanrangie

This may or may not be relevant but is a 30a controller adequate for 600W of solar panel, obviously 600W is max and probably not realistic ?

Normally it is set to 400W on the 12V side, and 200W on the 24V side, but when it is very cloudy I can push all panels through the 12V side (as that is where the majority of the heavy use is - the 24V stuff recharges when we drive from the alternator, but not the 12V)

You need to work out your total draw over a 24h period to make sure you have enough recharge capacity.

I have a TV/DVD as well but it's 240v and only runs with the generator. I have an inverter but don't use it. I'd rather use the generator for the 240v stuff and leave the battery for the 12v.