Victron is a pretty solid company for auxiliary battery components as well.
This little guy is what I’m using. With their solar mppt.
https://www.amazon.com/Victron-Intelligent-Battery-Combiner-Cyrix-ct/dp/B071Y7C9MM/ref=mp_s_a_1_16?dchild=1&keywords=victron&qid=1587912842&sr=8-16

On Sun, Apr 26, 2020 at 10:48 AM Dennis Haynes <d23haynes57@hotmail.com>
wrote:

> So for all these years Fun Bus has only had a group 41 house battery under
> the drivers seat with a simple relay for charging while driving and no
> means to charge while in storage. Since last April I have been primarily
> using the 91 van for daily use and the Florida trips. The house battery
> drained during winter last year and went bad. Did the same this year during
> the virus thing. So looking for an inexpensive charging solution I also
> considered a small inverter. I came across this.
>
> https://www.amazon.com/soyond-Inverter-Modified-Converter-Off-Grid/dp/B07W5YTTTF/ref=sr_1_18?crid=OFTR4XABIM5P&dchild=1&keywords=inverter+charger&qid=1587910620&sprefix=inverter%2Caps%2C158&sr=8-18
>
> So I have one here and have set it up in the garage for some testing. So I
> don't always trust ratings but with 100 A/H battery this thig will support
> a 1,500 watt heater. For the price, cool. It has a transfer switch for the
> outlets. Plug it in and the outlets go to the inlet power. Pull the plug
> and it quickly transfers back and the inverter picks up the load. I need to
> do more testing but it looks like the transfer switch also connects the
> outlet neutral to ground in inverter mode. Wow.
> For the charger section it does deliver just over 15 A/H and charges to an
> indicated 14.2 volts. Manual says it should go to a float mode. 2 days and
> still at 14.2.
>
> This unit does not have UL ETL, CSA listings on it and for RV use it
> should probably also have a GFCI. I plan to only use for direct plug in of
> double insulated appliances. It does not seem to be designed for hardwire
> installation on the 110 volt side. It has an LCD display that offers little
> information. No load or current information. Just volts in, out, status.
> There is a port for a remote display but I haven't found one yet. Product
> is probably very poorly supported.
>
> So my plant is to install this and replace the charge relay with an ACR.
>
> Dennis
>