48V Charger

[openspaceman]

This is what I am aiming for, to achieve grid independence. Won't there be less losses if a permanent magnet alternator just outputs DC via a rectifier and feeds a charger for the existing battery rather than have an extra conversion to AC? Then it can run asynchronously with no need to modulate power.

Are you building one yourself?

I have the concept for a micro CHP unit in my head but not much further.

Once I get a second hybrid inverter fitted with about 10kWh of battery I will be able to free up my current battery charger and try the concept as I have a small PM brushless motor which I can add 6 diodes to, as long as that produces more than 65V when spun at 3400rpm, I have some lawnmower engines for that.

I had a shortfall of 450kWh last year, I expect less this year as the extra 1800W PV and direct battery charging have made a big dent, so the generator only needs to run a couple of hundred hours a year IF I can operate islanded.

At my age it is hard to see a return in a sensible time, I do things much slower than before, and I have been repeatedly let down by suitably qualified installer/electricians. Even the supplier I have bought recent kit from has not been able to recommend any.

[AGT]

What ever you can afford, probably allow £20 a metre for 25x3 mm bare copper tape

https://www.electrical-installation.org ... electrodes

What is wrong with cleaning and flattening some old copper pipe and soldering an earth wire to it then burying it?

The termination needs to be accessible for inspection and testing, so maybe worth bending the pipe up and use an earth clamp inside a earth pit..

[Andy]

So another question regarding the chargers. A lot of them are specced to a higher voltage than the pylon tech. The BMS is showing a max charge of 53.2V. Most chargers on aliexpress are much higher voltage. The one on eBay linked to at the start is only 15A but limited to 53V. I'd really want 20-25A. I would only intend to recover the stack (38kWh) at very low SOC. A tank of gas in the generator would get 8-10% SOC at best. I presume with the limited current that the voltage would be dragged down by the batteries? Or would they get damaged? The batteries can take 640A according to the BMS. I don't think many of them are that 'intelligent' so would they just output 56V at the terminals?

[Tinbum]

You really need to plan for the worst eventuality.

You want a charger that can limit its voltage output to bellow the max the battery can take. (Assume some of the battery packs failed and you were just left with one connected and you were unaware. Unlikely but possible).

[Andy]

I've spent far too long looking around and there isn't a huge choice of adjustable voltage chargers. There is this one SolarLock on eBay preset for 53V, a load on aliexpress for about £100 that can be ordered with a custom voltage. They appear similar to the first option and scare me a little . Finally,the Mean Well NPB-1200-48 which is more but from what little I could find seem to be a little more robust. It is reprogrammable via the can bus. Has anyone had an experience with the various options particularly the Mean Well? I worry a little about connecting a cheap Chinese charger to my expensive equipment. Is that an unfounded fear?

[Joeboy]

I've spent far too long looking around and there isn't a huge choice of adjustable voltage chargers. There is this one SolarLock on eBay preset for 53V, a load on aliexpress for about £100 that can be ordered with a custom voltage. They appear similar to the first option and scare me a little . Finally,the Mean Well NPB-1200-48 which is more but from what little I could find seem to be a little more robust. It is reprogrammable via the can bus. Has anyone had an experience with the various options particularly the Mean Well? I worry a little about connecting a cheap Chinese charger to my expensive equipment. Is that an unfounded fear?

No. There really is some crap out there. Hunting down decent rated well built gear is worth the time.

[openspaceman]

Joeboy recommended the victron mppt 150 60 so I bought it a year ago. It has worked since January and connects by Bluetooth with no other gadgets necessary. It also has programmable contacts which I use to indicate when the immersion can take excess. The relay to control the immersion should arrive next week. It was double the price your linked one.

[Fintray]

Andy, Have you considered Eltek Flatpacks (Tinbum has some in operation), they can be up to 3000W output with the voltage variable from 43.2 - 57.6 VDC?

[MrPablo]

I believe the flatpacks can do CANbus Comms as well, if you wanted to get fancy with remote readings and control.

[Andy]

Thanks guys I hadn't considered them. So can I turn them down to output 25A for instance? What happens at the output end if it is trying to supply say 52V but the battery is much lower. If I have 25A set is the voltage just dragged down to support the current flowing into the battery? Does the eltek throw a wobbly because it isn't a charger and can't meet the 52V?