Self-jumpstarting means jumpstarting one's own vehicle without the use of another vehicle. It's done by combining house and chassis batteries by one of several methods discussed below.

Note: regardless of specific method used, it will be gentlest on the system to combine the batteries and wait a few minutes for the starter battery to come up instead of immediately attempting to start. This will minimize¹⁾ the amount of current flowing from house bank to vehicle chassis. This may be especially important with Li chemistries that have BMS protections.

This will be easiest if one already has some kind of isolator/combiner setup. If not, one can run jumper cables from the house bank, or physically remove the house bank and carry it to the starter battery area.

Switches used as manual isolators will self-jumpstart when in the ON position.

Solenoids/relays always self-jumpstart assuming there is enough voltage in the starter battery to energize the solenoid.²⁾ It is a mechanical connection and power will flow both ways.

Some VSRs have a provision to combine the batteries for self-jumpstarting.

Examples:

• Battery Doctor - integrated button
• Sure Power 1314 - user-added wiring³⁾
• Victron CT - user-added wiring to “start assist” terminal
• Precision Circuits BIM and Li-BIM - user added wiring to “sig” terminal⁴⁾ - see this article
• Blue Sea ML-ACR can combine banks manually or with the included remote switch

Solid state isolators are diode based and will not allow power to flow from the house battery to the starter battery. Therefore they cannot be used to self-jumpstart on their own (see below, including the Ctek exception).

As with diode-based isolators, DC-DC chargers typically cannot pass power back from the battery bank to the vehicle; there are exceptions. Read below for workarounds and different approaches.

It adds a layer of complexity, but a relay with a switch can be used to bridge the batteries manually.

Note the Smartpass does this when added to the CTEK D250-series chargers.

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 instead⁵⁾

Lithium banks can go dormant at low voltages in order to protect themselves:

1. the BMS turns off the DISCHARGE channel to keep cell voltage from going any lower
2. so the battery internally has ~11.0v or whatever but does not pass that voltage to the terminals on the outside of the battery case
3. which means smart chargers don't see battery voltage
4. and think there's a problem so they won't start⁶⁾

What we need is a dumb voltage source to get the party restarted. The starter battery will do nicely.

• Rigs with IGN-triggered relays can briefly turn the key to ACC then back off.⁷⁾
• Rigs with voltage-sensing relays will have to actually start the engine or press a manual override switch to activate the VSR and wake the lithium bank.
• Rigs with diode- or FET-based isolators would start the engine to spin the alternator and get power flowing through the isolator to the sleeping lithium

Lithium "jump packs" have become more popular. Lithium-chemistry batteries can discharge quickly, so even relative small packs can jumpstart a car.

'Dwellers may want to pick a jump pack that has 12v or USB outlets so it can have other uses.