"Rescue Charging" my house batteries

[The Game is Afoot]

I searched the forums and didn't find others talking about this particular scenario. I would love some wisdom! I need a way to safely recharge my house batteries using shore power, as a stop gap measure, during this cold snap.

I bought a Victron smart charger (12v, 20A, link), but I am uncertain on how to use it safely with my setup (pic of my setup below):
- My best plan currently is to throw the big red battery switch then hook the charger to the batteries and let it do its thing. Positive clamp to + pole battery A in the bank, negative clamp to - pole of battery D.
I am all ears if there's a better way! I am not adept in electrical work, but eager to learn from the many on here more experienced than me!

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Context: My Victron inverter (Multiplus II) is crapped out and pending a probable replacement under warranty. At this point it only allows passthrough AC current on shore power to the bus (this allows my 2 mini splits to run just fine). It no longer inverts anything (no DC to AC) and does not charge the house batteries (SOK LiPO4 12v 100Ah 4x in parallel). But, practically speaking, the DC and AC don't communicate even though everything is wired for that (fyi, had this all professionally installed by Cis Solar Designs; everything worked great before the inverter went on strike).
My solar still charges the batteries fine, but winter sun + this cold snap has me running a battery deficit every day - watching my batteries slowly tick downwards.

The eventual plan is to get the inverter repaired/replaced. Once my shore power and ginny are tied into the system again all my problems in life should be solved.

[Rucker]

A walmart battery charger should work just fine in your scenario. Just be sure to check charge regularly in case the stupid charger doesn't know how to handle LiFePo.

Connect red to positive and black to negative bus bars (so the charging is captured by your shunt, assuming you have one).

[cadillackid]

I have a couple of the 30 amp version of this charger.. you can look up the proper charging voltage for your batteries and use the victron connect app to program the charger to match the batteries.. it works great... from the factory i tyink it comes set up for AGM and not Lithium... theres also a custom option where you can get the charging datasheet from your battery manufacturer and set it up..