Charging Strategy, 1994 RoadTrek
Hi all, I've been diving back into how to upgrade my battery system in my class B and was hoping someone here could sanity check me. I have a small 100AH 12V coach battery and I'm upgrading to a pai...
Forum Discussion
I agree with Piano,
Its possible for the alternator to put out 120A but you must consider what the vehicle draws will be as well. Dodge charging systems of that era are lazy and indeed will likely shoot for only around 13.8 volts unless it is very cold outside. Also, I could probably guarantee that the existing charging wire is not adequate. Use #2 awg wire for your charge line. Connect it directly to the alternator positive post so that the original alternator wire lug is stacked on the lug with your new one. Attach a Fuse it as close as possible to alternator where you can access it. Fuse it at 100 amps. Do not connect the new wire on the engine battery, then you would be at the mercy of probably #6 awg OEM charging wire to the battery, which is far too small. Don't forget to add a nice big #2 wire for the L16 negative terminal to a shiny, thick spot on your frame somewhere.
I said to fuse it at 100 amps because you will likely use 105 degree C rated wire, but under the hood you will easily add even more heat. I doubt the alt will be able to blow that fuse even charging thirsty batteries with all other accessories running that are taking away some amps on the chassis side. Realistically, max charge current will probably be close to 90 amps with highway rpm and low coach batteries with the vehicle lights and fan off. Expect that figure to drop to about 40 amps or less at warm idle. With that alternator you WILL NEVER overcharge your batteries.
You would only have to worry about overcharging if you had a vehicle with a custom, high output alternator which could provide 14.5 volts at up to 150 amps or more, and you decided to go for an 8 hour drive after you had the batts fully charged with shore power over the last 2 nights.
DO NOT use a crappy diode isolator! It will drop the voltage badly in all circumstances. There would be almost zero charging at idle, and probably 50% less charging current at higher rpm. Use either a smart solenoid (BIRD) or a continuous duty RV solenoid for your positive Connection. Grease everything with a bolted connection with spark plug grease or similar dielectric after the bolts are torqued to avoid corrosion.
Use glued heat shrink on all connections, and closed ended lugs if possible. Otherwise they will corrode. It goes without saying to Disconnect negative or both negative and positive cables of your chassis and L16 batteries when wiring to avoid nasty accidental welding and burning.
Its possible for the alternator to put out 120A but you must consider what the vehicle draws will be as well. Dodge charging systems of that era are lazy and indeed will likely shoot for only around 13.8 volts unless it is very cold outside. Also, I could probably guarantee that the existing charging wire is not adequate. Use #2 awg wire for your charge line. Connect it directly to the alternator positive post so that the original alternator wire lug is stacked on the lug with your new one. Attach a Fuse it as close as possible to alternator where you can access it. Fuse it at 100 amps. Do not connect the new wire on the engine battery, then you would be at the mercy of probably #6 awg OEM charging wire to the battery, which is far too small. Don't forget to add a nice big #2 wire for the L16 negative terminal to a shiny, thick spot on your frame somewhere.
I said to fuse it at 100 amps because you will likely use 105 degree C rated wire, but under the hood you will easily add even more heat. I doubt the alt will be able to blow that fuse even charging thirsty batteries with all other accessories running that are taking away some amps on the chassis side. Realistically, max charge current will probably be close to 90 amps with highway rpm and low coach batteries with the vehicle lights and fan off. Expect that figure to drop to about 40 amps or less at warm idle. With that alternator you WILL NEVER overcharge your batteries.
You would only have to worry about overcharging if you had a vehicle with a custom, high output alternator which could provide 14.5 volts at up to 150 amps or more, and you decided to go for an 8 hour drive after you had the batts fully charged with shore power over the last 2 nights.
DO NOT use a crappy diode isolator! It will drop the voltage badly in all circumstances. There would be almost zero charging at idle, and probably 50% less charging current at higher rpm. Use either a smart solenoid (BIRD) or a continuous duty RV solenoid for your positive Connection. Grease everything with a bolted connection with spark plug grease or similar dielectric after the bolts are torqued to avoid corrosion.
Use glued heat shrink on all connections, and closed ended lugs if possible. Otherwise they will corrode. It goes without saying to Disconnect negative or both negative and positive cables of your chassis and L16 batteries when wiring to avoid nasty accidental welding and burning.
