The Lithium drop in conundrum

[Sailfast]

We are looking at an early 2014 Airstream Interstate with two Lifeline AGM 12V/220AH 6V batteries squeezed into the steel case battery compartment since almost new (dealer let it sit on the lot with the original AGM’s which naturally were toast). The charging system was upgraded to 300W solar with Bogart Engineering TM2030 and SC2030 solar controller. Works great, never go below 65% still chargeable to 100%.

I am sure many of you are having the same itch towards Lithium upgrade, sounds just like a the ideal for our RV’s and Lithium drop in replacements are aggrandized all over, “just drop it in” no problems.

There is indeed excellent product available, some with a 10 year warranty and low temperature protection, a must have for an RV in a colder climate or traveling in cold climates.

The problem is charge compatibility. Likely original solar chargers are not lithium compatible. Almost for certain most installed Magnum Inverter Chargers of the MMS1012 type are not compatible. The newer Magnum remotes like the ME-RV may be somewhat compatible or the ME-ARC is fully compatible. However, the MMS1012 Magnum inverter chargers are pretty dumb and won’t be able to follow the instructions from the remote. Now the MS2012 will work.

For a simple replacement, Magnum is just coming out with a MMS1012-L-U and L-F (L for Lithium) compatible with the newer controllers and fully CC/CV capable of charging Lithium batteries. Constant Voltage / Constant Current is really the proper way to charge lithium. Improper float charging stresses the cells and shortens the life.

In my case, I am planning to have 12V/200AH inside the existing battery steel case. So 2 x 100AH commercial drop in batteries won’t work. 8 LiFePo4 cells together with a 120A BMS w low temp protection will work just fine with room to spare for a 110V/60W heating pad withg thermostat that will turn on at 10 degrees Fahrenheit and go off at 30. Plus room to spare for a fused disconnect, Shunt, misc. cabling etc. All this can be done for around 1.4 boat dollars.

But now according to expert opinions I am going to need this and that, like a solid state BIM, a new inverter charger, a $225 Magnum Remote and probably about $900 for the inverter charge. There is another 1.2 or so boat dollars.

Lithium just drop it in! Not quite, so I am thinking is it all worth it?

As a side note: looking at the 2021 Airstream Interstate product, still lagging with technology. A built in generator is no longer needed with a proper lithium design.

Well just my humble opinion, but your thoughts will broaden my horizon.

[Halford1]

Certain lithium brands are expensive some are couple hundred dollars cheaper... I would change to lithium once my interstate batteries are dead.


And of course have to switch the controllers.