Best way to charge EB55 via solar/leisure LiFePO4 batteries?

Formerly, I was charging an EB55 via solar panels, but now those panels are being used on my campervan. I can still charge the EB55 via the van’s utility port or home outlets, but that only works when the engine is running or I’m at home. I’d like to have another way to charge it in the van. Charging via inverted AC in the van seems a waste (DC-AC-DC).

My question is: What’s the best way to charge an EB55 via solar and/or the leisure LiFePO4 batteries?

By the way, my leisure LiFePO4 batteries consist of two 400Ah batteries, and they are charged via 900W of solar panels (4x375W in series + 4x50W in series which are placed in parallel) whose max 72V/12.4A is comes through a Victron MPPT 100/20.

I’d connect the batteries to a 12->24V DC boost converter (recommend 400W for safety like this one: and then connect that output to the DC MPPT input port (which is an XT60 port) on your EB55. The Youtube channel Jasonoid has a video on how to do this although he uses 12->36V boost converters whereas you’ll want to use a single 12->24V converter: Make Your Power Station Last Longer! Power Queen 200AH LiFePO4 - DIY Expansion Battery! - YouTube. Wiring two of those converters in parallel (like Jasonoid does) won’t make any difference for your EB55 because it only accepts 8A which one converter can supply so I’d stick with just one.

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Thanks for the great suggestion. It turns out I posted a question about this same type of 12->24V DC converter on this forum earlier when I was wondering how to do quicker alternator charging of the EB55.
wiring diagram

So now I have 2 reasons to get this type of converter. I think I could set up a switch right before the 12–>24V converter as shown in the diagram above so that I could use the 12–>24V converter with either the leisure battery or van starter battery (ie, alternator/utility port). Right?

Yes, but you’ll need an appropriate switch. The switch will need to pass-through 200W @ 12V = 16.6A but it’s always a good idea to have some overhead for safety, and, if you want, for future-proofing. I’m no electrician but this 40A Rotary Changeover Switch might do the trick (one of the reviews includes a wiring diagram):

Is that OK? Two sets of panels in parallel would need to have very well matched voltage or it would be really inefficient. Is the Voc/Vmp between the 375w and 50w panels very similar?

Yes, you’re right that they must have well-matched voltages – and mine do, 18V and 18.6V resulting in 99% of the 902W possible if all panels had the same voltage

Good point. When I compare the cost of the switch/connections it makes me wonder if maybe getting two 12–>24V converters might be better.
Once again, thanks for helping me think through all this.