Reinforcing thin wires for MPPT install

DIY
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1

Hello guys, my first post here. This is actually a general electronics DIY question rather than something specifically related to Victron products. I figured this was the place it would most likely get a sympathetic hearing. Please bear with me.

We have an older Autosleepers conversion – basically, a nice caravan build crammed into a medium-sized cargo van. It’s mostly as it left the showroom, except that the previous owners rewired the water heater and I replaced the old Clipsal 12v sockets with modern USB converters.

Last year I took it to a local mobile home specialist and asked them to fit a Victron MPPT unit and a freestanding solar panel with removable connectors so that, if we’re offgrid for a night or two, we can send a small amount of extra power into the leisure battery and gain a few more hours of fan, lights etc. The Victron has worked really well, and being able to monitor its performance on my phone is a plus.

I sent the job out because I don’t fully understand how the leisure battery works with the main battery and I didn’t want to risk a non-startable van. The guy who did the install certainly knew his way around the electrics, but I don’t much like the quality of his work. He failed to tighten various bolts, fitted the Victron with self-tapping screws that have fallen out of the panel, left a crucial fuse in a state where jiggling it causes the lights to cut out etc etc.

After a recent late-night panic when we lost power due to a loose connection I’ve begun redoing all his work. One of the tasks has been to replace the loose fuse holder between the Victron and the battery. I chose a motorcycle fuse holder because it fits neatly into the space. It works fine, but has rather thin connectors. I was happy enough with the battery end, because the crimp-on terminal I fitted strengthens the wire where it’s vulnerable. But I’m worried about breaking the wire where it enters the Victron.

Is there some accepted way of reinforing thin wires in this kind of situation? Maybe you can buy a crimp-on sleeve or something?

2

Hello guys, this is one of those situations where using the right terminology makes all the difference. Turns out I needed some crimp-on ferrules. Cheap and readily available in beginner-friendly sets, so I can be sure of getting something that works even if I’m a bit shaky on cable sizing. Result!

3

It is best to oversize MPPT to battery wires to avoid voltage drop, usually using a higher cable rating. There are online voltage drop calculators one linked below. For the fuse, this really should be close to the battery positive terminal because it is there to protect the wire from short circuit and the battery can supply much more current in a short than the MPPT.

4

@niftyprose, it sounds like you’re doing your due diligence. Loose connections cause inefficiency in the system and even more importantly they can be the source of a fire. I have an annual reminder on my computer to go through my entire system and make sure all the fasteners are still tight.

I do use ferrules on cables where they go into a screw down terminal. I also add strain relief to ensure that the wires can’t wiggle around in the terminal. In the picture below from the system in my RV, you can see a blue “bracket” that the four wires are attached to using cable ties. The bracket is 1”x2” aluminum tubing.

Victron makes an add-on bracket, called the MPPT WireBox, for some of their solar charge controllers that does the same thing as my DIY bracket.

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Hiya Jim, thanks for your friendly note. The ferrules arrived from Amazon this morning, and I decided that I still wasn’t happy with the MPPT wiring. Your homebuilt bracket is would be the thing. I need to figure out how to make a UK equivalent. Great stuff. NP