6th Aug 2022
A couple of months ago I took a trip to Le Mans in the camper, and it was great fun. It was also extremely warm, and so the fridge was running 100% of the time we were there. It shouldn't have been a problem – we've got a couple of hundred watts of solar panels on the top to keep the batteries topped up. But there was a moment where the battery voltage indicator showed less than 10v – and that's not good™.
With a trip to Scotland with Wife and Kid creeping up on us before the summer holidays are over, that moment of battery oddness was playing on my mind. I don't mind roughing it if I'm on my own, but running out of power with the family in the middle of some mountains is something I'd rather avoid, so it was time to work out what was potentially up and make sure we were ready for the trip.
First up was some testing to find out whether the battery was a dud. For that I just gave the battery a good charge with a decent charger and then put a test load on the battery for a while. In this case it was the campers LED lights, which draw around 1amp.
I left that for about a day, and crunched some numbers, and it seemed that the battery wasn't in bad shape. That seemed like good news, but I don't really trust myself and my numbers around those electrical magic pixies. I don't know enough to be confident that that test alone was good, so I wanted a way to constantly monitor what was on with our power situation. It turns out that you can get something called a SmartShunt to measure all sorts of stuff battery wise, so obviously I was going to do exactly that.
With those bits ordered, I had a few new problems:
So with no jack available to me, and the knowledge that this wasn't going to be my last time getting at the battery, I needed a new plan. The battery was just under here...
Before I could finish thinking "I'm going to regret this in an hour or so", I had the knife out...
Once the flooring was cut I got the angrier, noisier, knife out and made a hole above the battery. This made getting the SmartShunt in fairly simple. While I was in there I moved around some other wiring and just gave everything a good check over. Things like moving the on board charger to be connected directly to the leisure battery rather than the starter. It all looks a bit terrible under there at the moment – soon I'll make a new battery box for it and weld it in to replace the ridiculous bolt "solution" that the original builder did. Either way here's how it looked once those things were done:
With that in place I parked the van up in the sunniest spot on the drive, and left it for a day to get some proper stats. It was very handy to have the stats, but what I noticed was that there was nowhere near as many amps going into the battery from the solar panels on top as I expected. Now, I've always expected the solar panels to perform more poorly than they should, because I mounted them underneath some roof bars. I did that so that I could still use the van to transport bits of timber when I'm doing other projects, but it means that there's always some shade on the panels. Here's a pic from when they were first installed to show what I mean:
Regardless of that setup, I was still surprised to be getting only around 0.6amp from the solar panels in midday sun. If this was the case in Le Mans it would definitely explain why we had the battery dip so low. Time for some more multimeter time for me, this time up on the roof of the van. Taking a load of measurements up on the roof, it seemed that one of the panels was suffering a lot from the shade of the roof bars, and the other was having a bad time in general. I removed them from the roof, placed them on top of the bars and got better results – still not great, but somewhere around the 2.5amp mark.
With that test done I knew that I had to mount them above the roof bars, but these are flexible panels so I'd need to make something rigid for them to mount to. They clearly weren't great panels anyway, so instead I made the choice to just grab a new rigid panel from Bimble Solar who happened to be round the corner in Lewes. I replaced the two 100W panels with a single 175W panel, mounted nice and firmly on top of the roof bars:
I lose the ability to carry timber on the top now, but it didn't happen that often so I'll just deal with that!
Firing up the app again after installing that, we got much better results – this pic shows around 7amps coming in from the panel straight away.
That was all great, and I monitored things for a while with the fridge on to see how it got on. All was well, except that I needed to be stood right next to the van to connect the app and get the stats. That's no good for someone who's efficiently lazy and wants to check from the sofa instead! The easy way to be able to check Victron kit from further away is to buy their Cerbo GX but I'd spent enough by now, so I wanted a cheaper way. Sure enough you can chuck their software on a Raspberry Pi and get much the same functionality, and guess who just so happens to have a couple of those lying around?
A little while and some soldering later, we have a Raspberry Pi on board Colin which can transmit the data from the battery any time it's within range of a known WiFi network (like when it's parked next to the house, for instance...) so I can check on the stats from all the way over on the sofa. Bliss.
There will be no battery anxiety on our trip to Scotland now, and that's well worth the tinkering time. Although some money was spent, it's far less than I originally feared in needing a new battery – at that point it would have been worth a proper upgrade and they can get to silly amounts of £££s.
Oh, the hole in the floor? You can hardly tell it's there, honest...