Dual battery / solenoid setup fell short on the convenience scale, time for an ACR?

rayra

Expedition Leader
So I was running around Santa Clarita the last few days during our flurry of regional fires, trying to get a first-hand appreciation of our danger (Rye fire was only a couple miles away, if the wind was different our neighborhood may well have been another Ventura).
I had a small peltier cooler plugged in, cold bottled water, helps get you thru a few roadblocks once in a while.
Anyway, got back home and left it plugged in. ~48hrs later I go to drive the vehicle and it's stone dead. Won't even respond to the alarm fobs. oops.
This is where the 200A combiner solenoid dual battery solution fell short. That solenoid is triggered by aux power from the factory wiring side of things, in my arrangement. The vehicle / starter battery only reading a paltry 3v+, the solenoid doesn't trip. My charged Aux / House battery sitting there doing me no good. So I had to crawl around and get to my cargo storage drawer platform top hatch to get to my jumper cables and self-jump. Which worked well enough. Ran my errands and put the starter battery on a battery charger when I got home.

So what do I replace the solenoid with so power flows automatically to the 'Starter battery' side of things. Doesn't an ACR do this? Or do I even want to do that? Had it been automatic, the cooler would have eventually drained both batteries. And as it was, the solenoid did what it ought, albeit in reverse, since the idea is run the Aux down and be able to start right up.

I don't really want to throw hundreds of dollars at the design solution. I am considering a couple other brute-simple solutions -

1) re-wire the vehicle interior 12v receptacles ('PowerPorts' in GM parlance) so they are powered from the Aux. I've yet to add a proper fuse block on that side of things, but will be shortly as part of adding a HAM radio / the next phase of electrical mods

2) only plug the small cooler into the vehicle's key-switched cig lighter port? But there are times when I WANT the cooler cooling when I'm away from the vehicle. And the 'PowerPorts' are always hot. And near term, I'm adding roof-mounted solar, which will feed the Aux. and the rear power systems I've added.

3) just add a dash-switched power circuit from the Aux to the solenoid energizer connection. From the comfort of the driver seat, flip a switch to energize the solenoid and connect the batteries. But IIRC the last time I did something like this with a small alligator-clip jumper lead from Aux to solenoid terminal, it backfed the factory aux power and popped its fuse. So maybe I need to put a diode on that line, at the solenoid terminal?


So is there a solution that will work as a charging combiner, a usage isolator, and a manual switched combiner when I stupidly repeat this failure? A solution that doesn't cost $400?
 
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Mgyver1

Observer
Easiest thing would be to install an override “self jump” switch powered from the aux battery side. This way you can activate the solenoid from the aux battery instead of the dead start battery.
 

dwh

Tail-End Charlie
Backfeeding doesn't blow fuses. Overcurrent blows fuses (unless you have special one-way fuses...but you don't).

But the situation you described was not a backfeed anyway.

Jumping the solenoid so power flows from the aux battery to the engine battery supplies power to the chassis electrical system via the engine battery wiring. That's not a backfeed, that's a normal power flow.

If doing so popped a fuse, then you have a different problem, such as an amperage increase due to a voltage decrease. A diode wouldn't help that - it would drop the voltage even more and exacerbate the problem. You may need to disconnect aux loads from the chassis wiring before supplying power from the house battery to the chassis battery.




I've self-jumped several times using a short wire with alligator clips to energize the dumb solenoid and never blown a fuse. I've also hooked a battery charger to the aux battery and used the short wire to energize the solenoid so the engine battery was tied in so it would charge along with the house battery. Again, never blown a fuse.


Your example 3 should be all you need. That's what the override switch on an ACR would do anyway.

If you still blow a fuse, then either disconnect loads from the chassis wiring before engaging the solenoid, or shift them over to the house battery (where they probably should be anyway) and avoid the problem altogether...which should also stop your engine battery from being drained and eliminate the need for a self-jump.
 

dwh

Tail-End Charlie
Hrmm. Thinking back on it. I do disconnect the ignition wire to the solenoid before using the jumper. Have to - mine has a 90 degree slip-on connection. Like the top connection in this random pic found on the net:

starter-relay-wiring.jpg%20alt=




So I suppose you could have backfed power to the ignition switch if you left it connected when you jumpered over from the aux battery terminal. (I'd have to think it over to figure out if that would be a problem or not, and I'm still on my first Sunday morning cup of coffee. Not thinking seems better right now.)

But that's easy to avoid if wiring a switch. Just use a double-throw switch. Solenoid to center, ignition hot to one side, aux battery to other side. Then it's either/or and...

"Oh, East is East, and West is West, and never the twain shall meet".
 

v_man

Explorer
I thought common practice when running accessories like a fridge was to power them with the the auxiliary battery...On my dual setup, my fridge runs through an aux. fuse box which is powered with the aux. battery. I also run 'option C', I have an in-dash switch that manually powers my $60 500 amp solenoid. The solenoid is powered through the starting battery. I would think you're first priority would be to move circuits that could drain your starting battery, off your starting battery...

9vPHTAL.jpg
 

rayra

Expedition Leader
I'm tapping power for the solenoid activation connection from a key-controlled optional accessory connection in an under-dash fuse panel (where the electric trailer brake controller and things like that are connected).

auxbatt057%20solenoid%20connector5.jpg



That's the circuit fuse that blew the last time I jumpered the positive terminal on the Aux battery to that terminal on the combiner solenoid.

auxbatt016.jpg



The irony is that I built all the added power connections in the rear of the vehicle to service these sorts of 'extra' power requirements, but in my haste and again convenience, I plugged the mini-cooler into the PowerPort on the rear face of my front center console, part of the factory wiring / drawing from the Starter battery

powermodule124.jpg



One of the later phases of my wiring projectwill be adding an under-hood aux fuse panel, powered by the Aux battery, for running my radios, LED lighting. At that time I'll divert all the factory 12v 'PowerPOrt' connections to the new Aux/Aux panel.
In the meantime I'll try to use the dash cig lighter / keyed port for the mini cooler.

I have a dash panel that fits 6 switches in a 3x2 array (where the defunct OnStar call button was, also a pull out cupholder location on some models). Intended for the aforementioned radios and lights, switches are there, none of the equipment is, yet. I have one switch not yet allocated. I guess that will become the (illuminated) solenoid activator from the Aux. And I'll put a diode on the 'normal' activation line, to prevent the backfeed situation.

And yes, a simple ON-OFF-ON toggle switch (A/B sort of thing) would be a simple / direct solution if I didn't already have the other wiring and switch plans in progress. And would obviate any backfeeding concerns. It would normally sit in one position, feeding the keyed power as it already is now. And in case of a similar failure occurrence just flip the toggle to feed power from the Aux battery to the solenoid activator.
 
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dar395

Adventurer
I thought common practice when running accessories like a fridge was to power them with the the auxiliary battery...On my dual setup, my fridge runs through an aux. fuse box which is powered with the aux. battery. I also run 'option C', I have an in-dash switch that manually powers my $60 500 amp solenoid. The solenoid is powered through the starting battery. I would think you're first priority would be to move circuits that could drain your starting battery, off your starting battery...

9vPHTAL.jpg

I agree with this understanding, after thousands of travel miles our system is flawless also.
 

lathamb

Observer
I have my second battery only there for an emergency (no accessories connected) with, hopefully, very little chance to drain both batteries. Personal preference. I have a completely manual system, and keep my jumper cables handy if i ever need to self jump.
 

Dan Grec

Expedition Leader
I'm confused how / why your "starter" battery was dead?

I have been running the "simple" dual setup with a solenoid for 18 months and 20,000 miles through West Africa and it's been absolutely bomb proof. I would never consider anything else in terms of simplicity and reliability.

-Dan
 

rayra

Expedition Leader
Simply left the vehicle sitting for a day+ with a small peltier cooler plugged into the factory-wired 12v power port, chilling six bottles of water to 34F. It's a very effective cooler / warmer, but it is not very efficient.

Multimeter on the dead starter battery showed just over 3v remaining. Insufficient power for the ignition key to energize the vehicle or the battery-connecting solenoid. So I had to contort and crawl into the rear of the vehicle to retrieve my jumper cables thru the top hatch of my storage drawer platform and self-jump.

I'll get a lit toggle switch installed to power the solenoid from the Aux battery, soon.

And the next vehicle project is to complete the rooftop solar panel integration and the re-sourcing of the vehicle's factory 'Power Ports' to run from the Aux. Need to find a local / regional source for the metal extrusions I need for the fabrication of the rooftop frame which will house my folding panel kit. And still have to decide if it will be aluminum or steel. WIll probably use aluminum and fasteners, but steel would give me the excuse to finally buy a wire-feed welding setup.
 

Dan Grec

Expedition Leader
Simply left the vehicle sitting for a day+ with a small peltier cooler plugged into the factory-wired 12v power port, chilling six bottles of water to 34F. It's a very effective cooler / warmer, but it is not very efficient.

Multimeter on the dead starter battery showed just over 3v remaining. Insufficient power for the ignition key to energize the vehicle or the battery-connecting solenoid. So I had to contort and crawl into the rear of the vehicle to retrieve my jumper cables thru the top hatch of my storage drawer platform and self-jump.

No matter what dual battery setup you have, and no matter what solar (or not) setup you have, don't power anything from the "starter" battery.

Power things like coolers from the "house battery". That's what it's for.

In short, don't use the factory-wired 12v outlet to run *anything* when the engine is off.

-Dan
 

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