Ideas for using a 36 volt lithium battery to boost a 12 volt lead acid battery?

I was recently given two 36 volt lithium ion batteries that were previously powering electric bicycles, and I'm wondering if there's some clever way to use them to boost the batteries in my RV? My RV has 4 Trojan T-105 6 volt batteries wired for 12 volts.

Currently I'm stepping the 36 volts down to 12 volts with a golf cart power adaptor that I'm clipping onto my batteries with allegator clips:


That works, but I don't think it's very efficient. I haven't connected an amp meter yet to see how much power is going into the battery, but I ordered one of these to monitor it:


The lithium batteries are rated 850 watt hours, but probably have much less capacity than that now. But still, very nice batteries.

My RV has a Morningstar MPPT-60 charge controller connected to three 300-watt solar panels. don't imagine it's possible to connect the battery directly to the charge controller (after disconnecting the panels)? My panels are the same voltage as the battery.

Or any other clever ideas?

How do you charge the 36 volters?
Do you know how many amps they output?
The problem with using the MPPT to buck the voltage is is that it can possibly output more amps than MPPT can handle. Possibly damaging the controller.

I'm using one of these cheapie chargers, which so far works great:


Not exactly that one but same specs. I switched everything (the battery and the charger) over to XT60 jacks, which I love working with. I had an old tackle box lying around so I installed the battery and and a cheap crappy car style inverter I had lying around into it for a "portable power pack", ha, pics attached.



It's very low in those pics, charged voltage is 42 volts. It has a BMS which should disconnect it when it gets super low but so far that's untested. Once I have the inline amp meter linked in my first post I can measure voltage and wattage without disconnecting the volt meter and get a running tally of watt hours.

Very good point about being potentially too much current for the Morningstar mppt-60. I wonder if there's some clever way to limit the current? I guess I could just put a 30 or 40 amp fuse inline, which would at least save the controller in case it tries to blast it...