====== Self-jumpstarting ======

Self-jumpstarting means jumpstarting one's own vehicle without the use of another vehicle.  It's done by [[electrical:12v:alternator|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 minimize((or eliminate, if the connection is broken prior to starting)) 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 bank =====


This will be easiest if one already has some kind of [[electrical:12v:alternator#isolators|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:  

  * [[https://amzn.to/2Ri2jQV|Battery Doctor]] - integrated button
  * [[http://amzn.to/2h2tDxp|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))
  * [[https://amzn.to/3h5iMUd|Victron CT]] - user-added wiring to "start assist" terminal
  * Precision Circuits [[http://precisioncircuitsinc.com/product/battery-isolation-manager-2/|BIM]] and [[https://amzn.to/3c6XwMv|Li-BIM]] - user added wiring to "sig" terminal((http://www.precisioncircuitsinc.com/wp-content/uploads/2017/06/00-10041-2xx-Battery-Isolation-Manager-Rev7-1.pdf)) - see [[https://www.explorist.life/how-to-wire-a-li-bim-battery-isolator/|this article]]
  * [[https://amzn.to/3CHoTt4|Blue Sea ML-ACR]] can combine banks manually or with the included remote switch


==== diode isolators ====

[[electrical:12v:alternator#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 [[electrical:12v:self-jumpstarting#adding_self-jumpstart_to_diode_isolators_and_dc-dc_chargers|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.  Read below for workarounds and different approaches. 

Exceptions:  

  * the [[https://battlebornbatteries.com/product/wakespeed-48v-12v-bi-directional-dc-dc-converter/|BattleBorn/Wakespeed 48v/12v Bi-Directional DC-DC  charger]] can send 50% of it's rated power to the starter battery.
  * the [[https://amzn.to/40WMp2L|Bluetti 800w alternator charger]] (DC-DC) has a starter battery maintenance function.




==== 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 [[https://www.redarc.com.au/bcdc-dual-with-jump-start-feature-the-ultimate-battery-setup|bridge the batteries manually]].

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



===== jump packs =====
[[https://amzn.to/2ITeBba|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. 

===== maintaining starter batteries =====

[this section [[electrical:12v:maintaining_starter_battery|has been moved]]]