Best way to charge 48v battery bank from generator?

[ThisTime]

I'm putting together a 10kw lithium ion 48v (14s) battery bank that will be used for backup power. Eventually I will grow this battery and add solar panels, but for now it's just backup. I want to be able to charge it using a small gas engine (propane) most likely the common Honda clone 6.5hp because parts are so cheap. I only want to generate about 2-3kw so this engine should be just right.

Question is what is the most efficient way to charge this battery pack from the engine? Should I just use a regular 120v AC generator and plug in a large 48v battery charger? Would it work well to use one of the permanent magnet converted 48v alternators on ebay? They claim to be for engine use but I suspect voltage isn't regulated very well. Is there a charge controller I can buy that will take variable DC input and charge the battery correctly? Is there any type of MPPT charger that I could use for this? Hoping for close to 50 amps for charging.

[SunEagle]

I'm putting together a 10kw lithium ion 48v (14s) battery bank that will be used for backup power. Eventually I will grow this battery and add solar panels, but for now it's just backup. I want to be able to charge it using a small gas engine (propane) most likely the common Honda clone 6.5hp because parts are so cheap. I only want to generate about 2-3kw so this engine should be just right.

Question is what is the most efficient way to charge this battery pack from the engine? Should I just use a regular 120v AC generator and plug in a large 48v battery charger? Would it work well to use one of the permanent magnet converted 48v alternators on ebay? They claim to be for engine use but I suspect voltage isn't regulated very well. Is there a charge controller I can buy that will take variable DC input and charge the battery correctly? Is there any type of MPPT charger that I could use for this? Hoping for close to 50 amps for charging.

IMO using a gen set and a stand alone battery charger rated for both the voltage and amperage needed is the easiest way.

You can then add the solar panels and MPPT CC later.

[chrisski]

I'd like to hear specifically what you decide on and how it works.

I am not a 48 volt user, but for my 12 volt and 24 volt system, I have an Aims converter that does 75 amps at 12 votls and 35 amps at 24 volts.

That is the most powerful 120 VAC 15 amp charger I found that has adjustments. There were many other that did not have a settable voltage or amperage for different battery packs.

Aims makes a 120 volt to 48 volt converter version that will charge at 17 amps.

Both converters I mentioned could pull up to 1000 watts from AC and have a 15 amp plug.

I think your battery pack is between 250 ah and 280 ah, so this converter could need to run a very long time, but could be powered by a 2 kw generator.

There's other available, I just don't know how they work. On another board, someone ordered one from Alibaba. This is something I've seen mentioned that is gasoline powered, but can push 70 amps, which is more what you need to recharge those batteries at any given time: "V5 AutoGen 48v DC Generator Charger 70 amps" at DC Generators,.

[ThisTime]

I've seen the chinese 48v DC generators - and I would LOVE to have one, but I'm left with a lot of questions and little information in english. They are like $600 after shipping, it appears that nobody imports these into the US (yet) by the container load, so shipping is expensive. My concern is the no name chinese electronic controller...if it smokes out one day is my whole investment gone? I would be willing to pay more for something similar from a known brand. It really is cool how they use the recoil side of the engine to mount the stator and it's also used as the electric start, it just has a plug on the other side of the engine where the crankshaft normally would come out. Super compact.

This again makes me wonder...are there any commercially available DC-DC converters/chargers that will take higher voltage DC and regulate it properly for the battery? Could be a replacement in the future if the chinese electronics stop working.

Short of that I am leaning more and more towards just using a 120v generator and charger. I'd like to find a 120v > 48v charger in the 20-25 amp range that would work in parallel with another. Then I can use two independent 120v/15A circuits to their fullest or charge at half speed. I could use two different generators if need be. I actually plan on having two identical generators anyway, as a backup.

[chrisski]

Some all in ones have a generator option.

Have you purchased components yet?

[Mike90250]

How do you use the 48V from the batteries ? Will you be using an inverter ? Many better inverters have an integral battery charger built in, they simply run the inverter H-Bridge in reverse and convert 120VAC to 48VDc to charge the battery bank.

https://en.wikipedia.org/wiki/Power_inverter#Advanced_designs

[ThisTime]

For now I'll be using the battery with a couple cheap 2kw inverters I already have for backup power (my power is not very reliable) and is a bit of an experiment before I buy more batteries and solar panels. Eventually I want to be off grid entirely, with a nice big 10-15kw inverter, but I don't want to invest in that part quite yet. The inverters I have don't do any charging. I need a good backup power system anyway so I'm putting this together before I try to go solar. I like to have backups for my backups, if you know what I mean...

I have the battery and inverters already but nothing else. Currently an expensive paperweight because I have no charger at all.