A new power project

If you're after a piece of gear that is reasonably expensive, and you see a lightly fire damaged one on Ebay, keep searching. Or allow plenty of time.

We want to be more grid independent, so was looking at power wall solutions. The biggest players such as SMA and Studer not only want stupid money, but if you want to see a some pretty graphs you have to use their gear $$$$$. Enter Victron and the Multiplus II

A good range of voltages and powers. In 2022 a 3kVA/48V or 24V version can be found for 1200€. Having spent 260€, I got this

Yep, I saved ~1000€ and gained a claimed working inverter. And a fair amount of work, but that's part of the fun, right?

Before 

After

See the melted wires and connectors?

There is also a fan (blades melted) , a support PCB and trafo. The trafo just wiped clean.

Cleaning was pretty basic. A tap water rinse with plenty of directed jets. Then to displace the water 99% ethanol in a sprayer and a child's toothbrush, plus other small brushes. 

You'll read plenty on line saying soot is magnetic, but none of this soot was. The nylon bristles on the a toothbrush are ethanol safe, but the handle may melt. ESD precautions were followed; no vacuuming, and no compressed air. A wet nylon brush is OK.

 A (lithium) battery fire that caught the OSB on fire. Note the power available light.  The owner confirmed it was still working after the fire. I suspect that the wiring was too small as the 10mm battery tails were still connected. 50mm recommended.

 A load of stuff to replace, the worst of which is the main power terminals. These terminal are designed to take 70A at 230V. Imagine the size of pcb track and the amount of heat to melt the solder.

This product is repairable with large soldering irons and experience. There are 5 PCBs; a SMPS; a logic board; logic board daughter module; 2 mosfet gate drivers.

The day after cleaning, with the PCB stored at room temperature, I powered it up. It worked fine with all of the suppression caps missing and a melted fuse left it. And not earthed. 

28/2/23 Finally ordered the spares from Mouser and replaced anything dodgy. The hardest part was removing and soldering back the parts. The PCB is likely 4oz copper and whilst it has lands, it took a large soldering iron bit and a 50W iron.

The new cap at the front was slightly taller. You can't really see, but the 3 at the rear were slightly bulging. The worst had gained 1.6ohms of ESR and lost 10% capacitance. The others seemed ok. All replaced along with the 3 red ones on the PCB. 3 X caps were changed. 2 charred relays work fine. The terminals are fine, just ugly. They are around 40€ to replace with Wurth, but still 10€ from no-name. I decided that there was little point as they were not going to get out the PCB easily, and I didn't want to grind/cut them out.

The fan was replaced with a similar flow unit (Noctua NF-F12 iPPC-24V-3000 Q100 IP67 PWM), but controlled with a pic using Intel PWM commands to the fan. There are a lot of posts in the Victron community with one dealer swapping out the fan before delivery with a quieter one with half the flow. The MP commands the fan to 40% on with only 1kW load in a room at 20C. It doesn't stay on long, but I think half flow is too marginal. It's a 20mm unit vs the original 30mm. It's held on with special anti vibration mounts at the bottom and a bit of wire at the top. Moving air makes noise; there is little vibration from this fan.

21/8/2024 When I installed this hard-wired into the house wiring, I decided to limit the scope of the inverter output. The AC input, which is what ESS drives ie charge from solar, and back-feed battery to grid is connected to 1 of 4 RCDs in the main board. I jiggled a few circuits around on another RCD and this has lighting, electric gates, some kitchen sockets, some lounge sockets and some bedroom sockets. Downstream of this RCD I fitted a manual change-over between grid and the multiplus AV output. The multiplus has a built-in bypass, so during normal operation you can tell it to disconnect from the grid. However, if it fails, or you switch it off, you have no power to parts of the house. Sure you can flick the manual bypass, but you have to be there for that. So I swapped it out for an automatic transfer switch. I bought this one

Not the fastest (50ms) and an electrical life of 1500 ops. It has a warning not to connect it onto a dead short, so you need to be careful! But at 25€ it will keep the fridge running if the multiplus dies and we're away. I've got it set with the multiplus as the priority supply - no point having grid as main, then waiting 50ms for the inverter to connect when it fails!

Look carefully at the size. I got it in my board, but it's tight. 10mm2 fine strand wire helped a lot

I'm pretty sure they make these for other brands, but the CE certificate has the Geya name on.