RV and vandwellers wiki

Some combo DC-DC chargers contain logic to maintain the starter battery when solar power is present.

Some standalone solar charge controllers like the Morningstar SunSaver Duo can, for example, charge the start battery with 10% of solar harvest and the house battery with 90% using different charging profiles. As with DC-DC above, it's not self-jumpstarting but can help prevent the dead starter battery.

dVSR isolators (including the Li-BIM) automatically connect the banks when the voltage on either side reaches defined setpoints.

Some Victron Multiplus models have a 4A starter battery maintenance feature.

There are dedicated maintainers:

• Some RVs were equipped with original Trik-L-Start or lithium-compatible Amp-L-Start modules by LSL Products, which is apparently out of business.
• The Xantrex echo charge maintains the chassis battery at up to 15A.

Experimental: RV With Tito has uses a PWM solar charge controller to maintain starter battery from the house bank.

Also see the subarticle on combiner gotchas.

If a DC-DC is present and relatively weak shore power charging is applied to the starter battery there are circumstances where the DC-DC can cycle on-off constantly. Let's consider a 20A DC-DC and a 10A starter battery maintainer.

1. starter battery at 12.7v before charging applied
2. starter battery voltage rises from 10A charging
3. DC-DC sees >13.4v and starts pulling ~22A to charge house battery at 20A
4. starter battery drops to 12.6v and DC-DC charger stops
5. repeat forever

To avoid this scenario either:

• ensure the DC-DC rating is smaller than the starter battery rating; or
• apply the shore power charging to the house bank side instead¹⁾