Self-jumpstarting means jump starting 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. Regardless of 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 minimize the amount of current flowing from house bank to vehicle chassis. This may be especially important with Li chemistries that have BMS protections.
Jumping from the house batteries
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.
Manual switches
Switches used as manual isolators will self-jumpstart when in the ON position.
Solenoids
Solenoids/relays always self-jumpstart assuming there is enough voltage in the starter battery to energize the solenoid.((If starter batt voltage is too low you can use a jumper wire to energize the solenoid from the battery bank. It's not passing charging current, just powering the electromagnet in the solenoid.)) It is a mechanical connection and power will flow both ways.
Voltage sensing relays
Some VSRs have a provision to combine the batteries for self-jumpstarting. Examples:
- Battery Doctor - integrated button
- Sure Power 1314 - user-added wiring(("Connect a #14 gauge wire from the start position of the ignition switch to the Start terminal of the Battery Separator. Make this connection at the ignition switch. This wire should only have voltage when the ignition switch is in the start position. Note: The start signal must be able to produce at least 3V* in order to provide automatic boost, see connection diagram above for manual operation option." - https://www.ase-supply.com/Sure_Power_1314_200_Battery_Separator_p/sp-1314-200.htm))
- Victron CT - user-added wiring to "start assist" terminal
- Precision Circuits BIM and Li-BIM - user added wiring to "sig" terminal[1] - see this article
- Blue Sea ML-ACR can combine banks manually or with the included remote switch
Diode isolators
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).
DC-DC chargers
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.
Adding self-jumpstart to diode isolators and DC-DC chargers
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.
Maintaining starter batteries
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 automatically connect the banks when either battery is sufficiently charged.
RV With Tito has experimented with a solar charge controller to maintain starter battery from the house bank.
Jump packs
Jump packs have become more popular. Lithium-chemistry batteries can discharge quickly, so even relative small packs can jumpstart a car. Nomads may want to choose a jump pack that has 12v or USB outlets so it can have other uses.