12v to 48v charging

[Captain Cyrus]

Hello fellow Skoolie enthusiasts. I am mid build and installing my electrical suite. I have a 48v LiFePO4 100ah as my house bank and am integrating with a Powmr all-in one inverter. My question relates to charging the 48v bank with the 12v alternator from the main engine. Buying a 48v alternator at the incredibly ridiculous price of 3k is out of my price range. I was considering adding a smart regulator that reallocated the 12v from the engine alternator after the start bank has been fully charged, to a 12v-120v converter, which would then lead into the AC inlet of the all-in-one inverter though a selector switch. I understand that this would be quite inefficient, energy wise, but it may allow me to at least charge the 48v bank from the 12v engine alternator safely. The 48v battery bank would receive the charge as a low amp shore power input through the inverter.

Any thoughts on this idea? Or better ideas? Thanks for your help 🙂

[joeblack5]

Not sure what a smart regulator would do for you but I agree that a 12v to 120 v inverter would be easiest ,cheapest and likely safest. The extra losses are not important since you run the engine anyhow.
You do not mention with what current your lithium charges from your all in one inverter. Just recalculate that to watts and take a cheap inverter twice the size.

I'd you want to get real fancy then get an inverter with a remote control switch wire/ contact that connects to your ignition / contact switch so that the inverter turns on / of if you start / stop your bus.

Besides all this you have then a redundant 120 volt inverter for emergencies.

Good luck

Johan

[TJones]

You need a 12v to 48v battery to battery charger like this:

https://www.sterling-power-usa.com/b...ychargers.aspx

This is what I am planning on using.

Ted

[rossvtaylor]

Originally Posted by TJones

You need a 12v to 48v battery to battery charger like this:

https://www.sterling-power-usa.com/b...ychargers.aspx

This is what I am planning on using.

Ted

Not the cheapest stuff...but I've been really impressed with the Sterling products and I think they're worth the money.

[Captain Cyrus]

Thanks everyone. The Sterling battery to battery charger is an elegant solution that I wasn’t aware was an available product. Thank you for the link. Presumably it has an internal regulator that is sophisticated enough to work with the sensitive LiFePO4 bank and not be in conflict with the all-in-one inverter. I will have to contract Sterling and research this further, but if not, then the price wouldn’t be much more then the other set up I was considering and worth the convenience of a simpler system.

[rossvtaylor]

Hi Captain, the Sterling will do true 4-stage charging and you can program the parameters...so you shouldn't have any issues. I haven't used the 12>48 version but I did use a 12>24V model and it worked well.

[Captain Cyrus]

That sounds very promising, thank you! Do you think it will confuse the all-in-one inverter to have another source charging the bank and changing the voltage? Or will the inverter just see the high voltage and assume a full bank has been achieved and stop sending the bank power from the panels? Have you seen anyone else pose this question? The all-in-one inverter is designed more for home use, so it doesn’t have an option for sensing engine charging input. Only for Panel or AC input, I believe.

[rossvtaylor]

They will play nicely with each other. The worst thing which might happen is one charge source will shut off before the other, as battery voltage gets bumped up during the charge...but that's not really a problem at all, since the remaining charge source will keep going until full charge.

[Captain Cyrus]

Thanks again for the insights on this, much appreciated!

[HamSkoolie]

We're looking at the same issue and are considering tapping our 160amp alternator for some 12 volt power to run an inverter then using the inverter to run a normal 110VDC charger for our 48V lithium battery bank.
This gives us the capability of charging while driving but also to unplug the charger from the inverter and connect it to any power source. Grid, genset, another skoolies 110, etc.

This would provide an emergency backup system should our main inverter/charger go out. A cheap (true sine wave) inverter could bybass the main inverter and provide power to run the fridge and minimal 110 necessities (phones/tablets for instance) while awaiting repair.



Just another way to skin the cat