Electrical backup hookup

[mobydick 11]

Hi all ,so i have a question for the electrical smart people on here . I have a 2008 Sprinter van ,it was a former fire command and investigation unit . The unit is already wired with led lights and plugins . Everything is powered up through a solenoid when you turn the key on .The unit has the main battery under the floor and an auxiliary battery under the hood . My question is ,I will be adding my 2 Trojan T105 in series to run my ARB fridge . if I hook these to the dead side of the the solenoid this should keep the light system live with the key off Correct ? Is there a danger or downfall to doing this ? And will it charge or over charge the TroJan battery when I am driving ? Thanks for the help as always .

 

[1stDeuce]

It will not overcharge the house batteries while driving. If anything, you'll find that they don't charge as well, as there will be a decent amount of voltage drop through the wiring, especially if they are low and drawing more current.

Aside from keeping the lights active at all times, you idea to connect to the existing disconnected side of the relay is fine. If you use the lights for camping, it's perfect. I would be sure that the supply wiring is of a decent size though, or you'll find that with the engine running, your charge voltage is fairly low, and it will take much longer to charge the house batteries if they're charging at low voltage. If you find this to be an issue, using a DC to DC charger will charge them better, as it will charge them at ideal voltage, rather than the lower voltage available though a long wire.

 

[mobydick 11]

It will not overcharge the house batteries while driving. If anything, you'll find that they don't charge as well, as there will be a decent amount of voltage drop through the wiring, especially if they are low and drawing more current.

Aside from keeping the lights active at all times, you idea to connect to the existing disconnected side of the relay is fine. If you use the lights for camping, it's perfect. I would be sure that the supply wiring is of a decent size though, or you'll find that with the engine running, your charge voltage is fairly low, and it will take much longer to charge the house batteries if they're charging at low voltage. If you find this to be an issue, using a DC to DC charger will charge them better, as it will charge them at ideal voltage, rather than the lower voltage available though a long wire.

Thank you for your help ,I will check out the wires and make sure they are ok . And yes the Trojan have taken a charge to over 14 volts ,so a DC to DC is a great idea . Thanks