Jumping starter battery from battery bank

By varying ways we've managed to drain our starter battery a couple of times. Yes, I know it's really bad for the battery.... The last time it happened we were at a Santana concert, so lots of folks around and got a jump from a sheriff. It got me thinking of an emergency plan....

My house system is 4 100 Ah AGM batteries completely isolated from the vehicle electronics. I was thinking of making some custom jumper cables to span the distance. Then turn off the solar controller and inverter/charger, and jump from the most + positive pole and most - negative pool. Hooking directly to the batteries would by pass all fuses and switches.

Will this work? Am I putting any components at risk? Emergency use only - think way out of cell range and no other vehicles around. TIA
 

OrioN

2008 2500 170" EXT
I use an automatic charge relay (ACR) between house & chassis banks. I can manually open or close it, and this allows me to start the vehicle from the house bank. I believe starting the van requires ~100-150A weather dependent, and this is not enough to damage your house bank.
 

autostaretx

Erratic Member
A trick to remember in cases like this is to join the batteries ... and then wait a few minutes .... this allows a partial re-charge of the Starter battery *before* trying to start the van... that will be that much less current that will be asked to flow through the "jumper" during the starting process.

Many people have such an "over-rideable" isolation relay/gadget for just this situation.
There should be no need to disconnect your solar (etc), it'll just think your house battery is (momentarily) at a very low state of charge.

--dick (who'll get around to installing such an isolator ... some day)
(at the moment i carry jumper cables)(and a shore-powered "can supply short burst of 125 amp starting current" battery charger)
 

marklg

Well-known member
A trick to remember in cases like this is to join the batteries ... and then wait a few minutes .... this allows a partial re-charge of the Starter battery *before* trying to start the van... that will be that much less current that will be asked to flow through the "jumper" during the starting process.

Many people have such an "over-rideable" isolation relay/gadget for just this situation.
There should be no need to disconnect your solar (etc), it'll just think your house battery is (momentarily) at a very low state of charge.

--dick (who'll get around to installing such an isolator ... some day)
(at the moment i carry jumper cables)(and a shore-powered "can supply short burst of 125 amp starting current" battery charger)
I did exactly that, using the original battery isolation relay, controlled manually by a big red guarded switch, just for effect. The normal charging from the starter battery to the house batteries is via a Sterling BB1260, round control panel on the right. Solar is the control panel on top. Inverter / Charger is the control panel in the middle. Big red scary looking switch on the left is to charge the starter battery from the house batteries. Takes maybe 10 min or less to provide a charge enough to start the vehicle.

Control_Panels.jpg

Regards,

Mark
 

john61ct

New member
Just know if the problem is a dead short rather than just a depleted Starter, you may create more problems.

An alternative is those pocket sized lithium jumpstarter packs.
 

marklg

Well-known member
Just know if the problem is a dead short rather than just a depleted Starter, you may create more problems.

An alternative is those pocket sized lithium jumpstarter packs.
I have a resettable breaker in the line, I think 30A, for that case, and the wiring is not that large.

Regards,

Mark
 

john61ct

New member
Cranking an engine can easily be 500+ amps, but for a short time.

The infrastructure between House, ACR, from there to Starter needs to handle that safely.
 

john61ct

New member
Define short time..... :popcorn:
Well for a healthy rig the overall event shouldn't be much over a second.

But the really crazy high current levels are only for the first 50ms or so, then dropping by half in each of the next 50ms units, as inertial resistance / friction is overcome and the crankshaft starts actually rotating.
 

billintomahawk

'02 2.7 T!N Freightliner
I have 4 GA cable running between my house battery and the starter. There is a manual connect/disconnect marine switch in the line. I can start the vehicle or charge the house battery when the vehicle is running. Or disconnect it.

This system works very well.



Here's a CRUDE but simple and effective wiring diagram for lights, solar and vehicle charging.







House battery under the passengers seat.



bill in tomahawk
 
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OrioN

2008 2500 170" EXT
Oh god... For those that don't know, unfused wires shorting to ground, general produces fire, plasma, and general mayhem... Worst case the wire will become vapor...
Speaking of vapour.... those sparks could ignite the open bottle of gin that is squeezed between the handbrake lever and the seat-base. :smilewink:
 

BrennWagon

He’s just this guy, you know?
Bill, in all seriousness, you need to modify your electrical system to include a fuse near the positive battery terminal and grommets for every penetration. It doesn’t look like the holes were even deburred. If one of those positive cables gets a nic in it the best case scenario is that it will weld itself to the seat base. The worst case scenarios were listed above. At least put a few layers of electrical tape on the inside edges of the penetrations until you have the time and materials to do it right. You seem like a good guy, it would be a real shame if you were injured or worse.
 

billintomahawk

'02 2.7 T!N Freightliner
Guys, yes, all solid points, I ran into a time crunch on the gromets and actually the wiring is mostly wrapped with 3M electrical tape at critical junctures but the observation that the wiring between the starter terminal and the house battery not being fused is correct and the weak point in the system.

Of course the manual disconnect provides some relief but not enough for true safety.

I am in Aspen Colorado having made the jump out of Wisconsin and ran over Independence Pass yesterday all in an effort to test the mechanics of the van. It passed the rough and rugged and all stayed intact so I'll go after some more protection with haste as best I can on the road. Love the Green Diesel tune. Power at 10K elevation to burn.

Something will happen but fusing the main vehicle-house connection will have to wait a few weeks to source a decent breaker.

Saw Jenny Lewis perform last night at a local music venue called Belly Up.

https://bellyupaspen.com/

What a show!!

https://www.youtube.com/watch?v=xhjoRvn3xxM

We camped at the bus terminal last night for free.

Van life.

Thanks for the advice.

Jenny will be performing in a street concert August 9 in Eau Claire Wisconsin in case you are looking for a road trip.

Free camping at my place in Tomahawk and we can find a place the night of the concert.
Stay a month, see Lake Superior and the UP.

Just saying.

https://www.theoxbowhotel.com/signature/oxbeaux/

bill
 
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vanski

'05 Box Snow Camper
Not fused and only 4awg when there’s a possibility of 500+amps passing for a few milliseconds and 125amps sustained for a few seconds? How long is that wire run? Not trying to join the bash wagon, genuinely concerned....
 

danpaul000

A man, a van, no plan
By varying ways we've managed to drain our starter battery a couple of times. Yes, I know it's really bad for the battery.... The last time it happened we were at a Santana concert, so lots of folks around and got a jump from a sheriff. It got me thinking of an emergency plan....

My house system is 4 100 Ah AGM batteries completely isolated from the vehicle electronics. I was thinking of making some custom jumper cables to span the distance. Then turn off the solar controller and inverter/charger, and jump from the most + positive pole and most - negative pool. Hooking directly to the batteries would by pass all fuses and switches.

Will this work? Am I putting any components at risk? Emergency use only - think way out of cell range and no other vehicles around. TIA
I've jumped my engine from my house battery once after leaving the headlights on in a long term parking lot. The house battery is a single 260AH AGM near the rear axle. I have a 24' length of 2/0 AWG wire running from my house battery positive to my starter battery positive, with a cutoff switch (normally open/disconnected) near the house battery. There is a 300A slow blow terminal fuse from BlueSea systems at each end of the wire. The return path for the current is the vehicle frame. I have a short wire from my house battery negative bus bar to a polished section of the frame a foot or so away. I connected my cutoff switch to join the batteries, waited about 30 seconds, then started the engine. Fired right up. Hope this helps.

Cheerio,
Dan
 

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