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Discussion Starter #1
Does anyone know how much current a 2019 3.7 starter motor will draw when cranked? I guess I can throw a clamp meter on it, but I'm not sure it would capture the peak current fast enough.
 

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Discussion Starter #2
Just tried to measure it. Clamp meter said 195A on first start and 156A on second start. Not sure how accurate my meter is on getting the peak.
 

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Looks about right.

High currents, short time periods.

That is why there are starter batteries, marine batteries and deep discharge batteries.

The box looks the same but the guts are somewhat different.

Similar for the starter motor wiring. For 10 - 30 seconds the small wires can get quite warm but since it isn't continuous use, they don't melt.
 

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I'd suspect it is a little higher. On a frosty morning higher still. I'll throw my clamp meter on mine and see what I get. Just curious, why do you want to know?
 

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I'd suspect it is a little higher. On a frosty morning higher still. I'll throw my clamp meter on mine and see what I get. Just curious, why do you want to know?
I might try to set up my camper's electrical system so that the house battery can be used to start the engine if the starter battery dies.
 

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I might try to set up my camper's electrical system so that the house battery can be used to start the engine if the starter battery dies.
Gotcha. I have wondered about using my house bank for the same. As it has a 100 amp BMS I guess I would connect the two and wait for a few minutes and then give it a shot starting.
 

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It took very little external boost the 2x the starter battery was dead enough to reset the clock to 12 AM and reset the trip odometer to zero.

There's a 20 amp manual toggle switch configured to allow the house battery to charge from the alternator through a CCP. It also allows the house battery to equalize with the starter battery. Its saved me from having to jump start. Have to be sure to move the switch to Off when attempting to start after allowing it to equalize or risk blowing the 60 A CCP fused link. An inline 50 A fuse might be wise between CCP & the house battery.
 

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How to use a battery switch to use the house battery bank for jump starting.

 

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The Orion-Tr Smart DC-DC charger comes in both "Isolated" and "non-isolated" versions. Does this mean that the isolated version stops any drain from the starter battery to the house battery. Would the non-isolated version be a way of balancing both systems? What is the advantage of one over the other?

One other benefit of the Orion-Tr Smart DC-DC charger "I think" is that one can see charged state of the house battery. Maybe an extra smart shunt in the system would be a good idea so that the starter battery could be monitored with the rest of the Victron system.
 

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I just use a 120 vac to 12 vdc charger to move power.

Used it a few months ago to start my wife's car from my van's auxiliary electrical system.

The one I have is a 75 amp @12 volt IOTA and takes a 20 amp plug but they make smaller ones.
 

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Discussion Starter #12
It took very little external boost the 2x the starter battery was dead enough to reset the clock to 12 AM and reset the trip odometer to zero.

There's a 20 amp manual toggle switch configured to allow the house battery to charge from the alternator through a CCP. It also allows the house battery to equalize with the starter battery. Its saved me from having to jump start. Have to be sure to move the switch to Off when attempting to start after allowing it to equalize or risk blowing the 60 A CCP fused link. An inline 50 A fuse might be wise between CCP & the house battery.
Not sure I follow you logic on this. Did you add a 20A manual toggle between the house battery and CCP?
 

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I just use a 120 vac to 12 vdc charger to move power.

Used it a few months ago to start my wife's car from my van's auxiliary electrical system.

The one I have is a 75 amp @12 volt IOTA and takes a 20 amp plug but they make smaller ones.
So your just using a basic 12V FLA charger to give the starter battery a boost? Would a 25A charger work?
 

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Not sure I follow you logic on this. Did you add a 20A manual toggle between the house battery and CCP?
Yes, it's next to my seat belt buckle. Fasten the seat belt, flip the switch On. Unbuckle the seat belt, flip the switch Off. Need some juice in a dead starter battery, flip the switch On, wait a couple minutes, flip it back Off and turn the key.
 

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I just use a 120 vac to 12 vdc charger to move power.

Used it a few months ago to start my wife's car from my van's auxiliary electrical system.

The one I have is a 75 amp @12 volt IOTA and takes a 20 amp plug but they make smaller ones.
I too use a 120 vac to 12 vac charger , I power mine from my generator , I take it that your powering yours from a invertor ?
 

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I too use a 120 vac to 12 vac charger , I power mine from my generator , I take it that your powering yours from a invertor ?
Yes.

I have one of these in my van.
  • 20 amp @ 120 vac inverter
  • 4 each Lifeline GPL-27Ts wired in series
  • solar, etc

 

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So your just using a basic 12V FLA charger to give the starter battery a boost? Would a 25A charger work?
I have done this exactly 1 time so far.

The reason is that my wife's car would not start, she was stranded late at night and I could not find my jumper cables.

I had the 75 amp charger already wired with heavy duty jumper cables for one of the test stands I use for van work, so I used it.

Jump starting a car from an operating car means that you are really using its (alternator) + (starter battery) to power the starter of the inoperable vehicle.

What I did was partially recharge the inoperable vehicle starter battery using the 12 volt charger. Essentially charging it enough to run the starter, as the charger cannot by itself provide this amount of power. This takes time, the smaller the charger amps, the longer it takes.

A quick estimate of what is needed, using the OP's measurements:

(200 amps) x ( ~ 5 seconds) ~ 1000 amp-seconds @12 volts

(1000 amp-seconds @ 12 volts) / (25 amp charger) ~ 400 seconds ~ 7 minutes minimum to move enough power.

Maybe double that estimate to be safe ????
 

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Discussion Starter #18
I have done this exactly 1 time so far.

The reason is that my wife's car would not start, she was stranded late at night and I could not find my jumper cables.

I had the 75 amp charger already wired with heavy duty jumper cables for one of the test stands I use for van work, so I used it.

Jump starting a car from an operating car means that you are really using its (alternator) + (starter battery) to power the starter of the inoperable vehicle.

What I did was partially recharge the inoperable vehicle starter battery using the 12 volt charger. Essentially charging it enough to run the starter, as the charger cannot by itself provide this amount of power. This takes time, the smaller the charger amps, the longer it takes.

A quick estimate of what is needed, using the OP's measurements:

(200 amps) x ( ~ 5 seconds) ~ 1000 amp-seconds @12 volts

(1000 amp-seconds @ 12 volts) / (25 amp charger) ~ 400 seconds ~ 7 minutes minimum to move enough power.

Maybe double that estimate to be safe ????
Thanks for explaining! My case would be similar, just for emergency use. If it took 10, 30, or even 60 min to transfer enough power, it's better than nothing!
 
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