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--- electrical:12v:self-jumpstarting [2024/03/22 08:19]
frater_secessus [Self-jumpstarting]
+++ electrical:12v:self-jumpstarting [2025/04/20 12:47] (current)
frater_secessus [DC-DC chargers]
@@ Line 34: / Line 34: @@
 ==== 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.
+As with diode-based isolators, DC-DC chargers typically cannot jumppstart from the aux battery bank
+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.
-==== adding self-jumpstart to diode isolators and DC-DC chargers ====
+Some [[electrical:12v:b2b#examples_-_combo_with_solar_charge_controller|combo MPPT/DC-DC]] have [[electrical:12v:maintaining_starter_battery|starter battery maintenance]].
-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.
-===== maintaining starter batteries =====
-Some [[electrical:12v:b2b#examples_-_combo_with_solar_charge_controller|combo DC-DC chargers]] contain logic to maintain the starter battery when solar power is present.
-Some standalone solar charge controllers like the [[https://amzn.to/2PPTD2L|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.
-[[electrical:12v:alternator#voltage-sensing_relays|dVSR isolators]] (including [[electrical:12v:alternator#lithium-specific_vsr|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 [[http://www.lslproducts.net/|apparently out of business]].
-  * The [[https://amzn.to/47HMMyn|Xantrex echo charge]] maintains the chassis battery at up to 15A.
-Experimental:  RV With Tito has [[https://www.youtube.com/watch?v=exQSsTiclOo|uses a PWM solar charge controller to maintain starter battery from the house bank]].
-Also see [[electrical:12v:alternator#gotchas|the subarticle on combiner gotchas]].
-==== starter battery chargers alongside DC-DC chargers ====
-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.
-  - starter battery at 12.7v before charging applied
-  - starter battery voltage rises from 10A charging
-  - DC-DC sees >13.4v and [[electrical:12v:b2b#sizing|starts pulling ~22A]] to charge house battery at 20A
-  - starter battery drops to 12.6v and DC-DC charger stops
-   - 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 instead((for DC-DC models with starter battery maintenance, see above))
-===== waking lithium batteries =====
-Lithium banks can go dormant at low voltages in order to protect themselves:
-  - the BMS turns off the DISCHARGE channel to keep cell voltage from going any lower
-  - 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
-  - which means smart chargers don't see battery voltage
-  - and think there's a problem so they won't start(("too smart for their own good"))
-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.((don't leave it on ACC long or the dead Li will suck power from the starter battery.  Either turn ACC off again or actually start the vehicle.))
-  * 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
+==== 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.
@@ Line 110: / Line 58: @@
 '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]]]

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