Billy the Bus's Blog

Sunday, January 11, 2009

Camper electrics

I've finally finished a job I've been wanting to do for ages. Basically, I've sorted the camper electrics. I know a) understand the behaviour of the leisure battery, b) have good meters in place, and c) have a well arranged 240v system.

While I was on the big trip, the leisure battery didn't perform very well. I posted about it here. I wasn't getting more than 30 minutes of juice really. So when I was at home for Christmas, me and Dad did some experiments trying to find out what was going wrong. They proved pretty inconclusive - apart from a slight voltage drop off between the two batteries (maybe 0.2v) it seemed to be getting plenty of juice while charging (14V), allbeit at a fairly gentle current (1.5A).

So we did some more reading and discussed it on the forums, and found out more about the chemistry and construction of deep cycle batteries. I think the mistake I made before the big drip was not conditioning the battery with a really good mains charge. I did charge it on the mains before mine and Dad's experiments, hence the low current. Since then, the battery has been running fine. So, feel a bit stupid about that.

One thing that came out of the experiments with Dad, is he made a really good ammeter. He made his own shunt, and measured the voltage drop and all that stuff and ... basically, he's a very clever chap and I now have a 20A meter on my panel, switchable to show charge or discharge.

And finally, I have put a couple of switches in place to help me manage the 240v invertor better. On the trip, I used the switch on the invertor to turn it on and off, which involved putting my hand deep into the bowels of the cupboard and finding it blind - it was a bit annoying. Also, I ran everything off this one 4-gang which meant even if I was just charging the laptop, the whole TV and everything had to be on. I've now put a separate switch in now for the TV stuff, so you can turn it on separately.

Finally, here's a wiring diagram I drew. Nerdingly brilliant.