This goes back to an ongoing post, not a problem. adding dual batteries to an E350.

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#16
The indicator is "on steady" with key on, engine off. I agree that if wire the gauge into the circuit BEFORE the resistor, I could have both guage and indicator,
It may be a few weeks (ok more) before I get a second gauge installed, but I will post back!
 
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#17
Hello Mobile Dan and the BAT crew and all those looking for help, you have come to the best place.
I have completed my duel battery project (it actually has been operational for over a year)
The latest update is a second volt meter. The first volt meter pulls off the ignition, basic.
The second volt meter is in the frame mount battery circuit
I have attached a few pictures and illustration
 

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billj

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#18
Just an update. A couple weeks after the second volt gauge install that gauge would fail to show voltage until several minutes after starting the engine. After couple more weeks went by the time increased until, finally the second battery circuit did not activate at all. After looking for a bad isolator, relay, connection, etc. I discovered that the secondary battery disconnect switch had gone bad. I replaced it with a heavy duty switch rated up to 60V.
I was thinking that maybe the second volt gauge was overkill, but it was well worth the effort.
 

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#20
Had three batteries in my motorhome, two in parallel for the cabin third for the engine, but that had a high current switch to also be in parallel with the other two. Kept that switch closed and modified the AC power supply to output 13.5 volts when it was parked to keep the batteries fully charged. First three lasted ten years this way.

When driving the alternator kept all three batteries fully charged, but when on battery only operation in places where no AC was available, disconnected the engine battery from the two that powered all the 12V stuff in the motorhome. That way enough energy to start that 454.

Indicator was a voltmeter, expanded scale type between 10-16 volts. When the voltage dropped to 11V time to quit. But could start the generator to recharge the batteries. That provided 120VAC to the battery power supply.

Voltmeter is the best bit to learn your state of charge.

Back in the not so good old days on all vehicles and ammeter was used and connected between the generator and the battery. Was a zero center type, when the needle went to the right of center, generator was charging the battery. But when the battery was fully charged, wouldn't take a charge anymore, so the needle would go to dead center or zero.

Whenever the engine slowed down, generator could not keep up with it, so the ammeter would show negative or battery discharge. Really never showed the state of charge of the battery. But you would know this when the starter would barely turn over and the headlamps were dim.

Deep cycle batteries were used in the motorhome, regular vehicle batteries can only take about three maximum full discharges than lose there ampere hour capacity. I just try to find the largest battery that will fit in the battery holder.
 

billj

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#21
I have been using regular vehicle batteries. My set up uses the under hood battery to power cargo and cab lights ( 8 led bulbs ), and anything else that pulls power while engine is off. Then as soon as the key is turned on power is supplied for starting and both are charged by the alternator. Alternator will put out 14.3 volts charging. 12.6 volts is normal starting.
 

nickb2

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#22
I have been using regular vehicle batteries. My set up uses the under hood battery to power cargo and cab lights ( 8 led bulbs ), and anything else that pulls power while engine is off. Then as soon as the key is turned on power is supplied for starting and both are charged by the alternator. Alternator will put out 14.3 volts charging. 12.6 volts is normal starting.
and this need to talk to each other.
If your indicator is "on steady" with key on, engine off, then a volt guage should act the same way (with resistor removed or bypassed).

If you wired the guage into the circuit BEFORE the resistor, you could have both guage and indicator, I think.
 

nickb2

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#23
I think the other nick said marine/deep cycle etc/ your at home son bat are better for this sort of dual application

Just for the other Nick. I appreciate you so much, it makes me want to be old like you. Tune for nickd