There is only a couple of ways to charge deep cycle batteries. The big thing for us is how long does it take.
This brochure report from Progressive Dynamics is good to follow for how long does it take to re-charge a deep cycle battery.
"Progressive Dynamics ran this test on the amount of time it took a PD9155 (55-amp) converter/charger set to three different output voltages to recharge a 125 AH (Amp Hour) battery after it was fully discharged to 10.5-volts.
14.4-VOLTS (Boost Mode) – Returned the battery to 90% of full charge in approximately 3-hours. The battery reached full charge in approximately 11 hours.
13.6-VOLTS (Normal Mode) – Required 40-hours to return the battery to 90% of full charge and 78-hours to reach full charge.
13.2-VOLTS (Storage Mode) – Required 60-hours to return the battery to 90% of full charge and 100-hours to reach full charge."
It doesn't matter where you get the charging power from but it looks like you need to have these DC voltages available shown in the brochure report and will also need about 20AMPS of charging power available for each 12VDC battery you are wanting to charge. This is especially required if you want to recharge your batteries in the short three hour time frame.
One downside for taping into your truck alternator system is you have to use a SMART RELAY to isolate the systems and cannot use the old time high current DIODE battery isolator as their internal DC VOLTAGE drop is around 0.7 VDC which will result in not getting the required DC voltages listed in the report to recharge your deep battery in the short time frame they list...
I suspect the 12VDC power you have available at the 7-way connector is not going to be 20AMPs. This will relate drastically on how long it will take to recharge any deep cycle battery connected to it.
We camp alot off the power grid and would never think of using anything associated with the truck alternator system without alot of planning as this is the way you get back home. Once it is dead you may be in alot of trouble. Not a good PLAN B source for me to be successful...
just my take on the subj...
Roy Ken
