I have a 12v 4x100a LFP battery being charged with a new Renogy 12v DC/DC charger from vehicle alternator. The vehicle is 2018 Toyota Sienna with standard 270a alternator putting out about 13.7 Volts. Connected directly to the alternator with a 20foot run of 8ga the DC/DC charger will drop the alternator input line voltage measured at the alt+ port on the DC/DC charger from 13.7v to 11.7V while pulling 15-20a. It will only charge for about 2 seconds before shutting down and pausing for about 30 seconds before restarting the 2 second charging cycle.
Renogy mentions that if you have a smart alternator, you need to connect the smart alternator signal wire D+ directly to the alternator signal port. It seems to indicate that newer vehicles likely have a smart alternator that doesn't put out the std 14V that older alternators did.
The supplied signal wire is way too short to run all the way up to the alternator so I just jumper connected the signal wire to the alt+ pin feed line to the Renogy 2 inches away. This makes the Renogy seem to work fine and it will charge the LFP for an hour or 2 before suddenly shutting down like it had died. However the next day, the Renogy will start charging again for about an hour before shutting down again.
Is my input line voltage drop from the alternator causing this problem?
I see from the wiring diagram my LFP house battery should have a connection to the Veh ground which it presently doesn't have. I will add this.
Renogy mentions that if you have a smart alternator, you need to connect the smart alternator signal wire D+ directly to the alternator signal port. It seems to indicate that newer vehicles likely have a smart alternator that doesn't put out the std 14V that older alternators did.
The supplied signal wire is way too short to run all the way up to the alternator so I just jumper connected the signal wire to the alt+ pin feed line to the Renogy 2 inches away. This makes the Renogy seem to work fine and it will charge the LFP for an hour or 2 before suddenly shutting down like it had died. However the next day, the Renogy will start charging again for about an hour before shutting down again.
Is my input line voltage drop from the alternator causing this problem?
I see from the wiring diagram my LFP house battery should have a connection to the Veh ground which it presently doesn't have. I will add this.
