the green line needs to go to a line that only runs either:
A) when the vehicle is not running (engine off)
B) when the vehicle is not charging (your recommendation)
No, the green line has to be on (+12V) when the vehicle is charging (ie, engine running).
The SPG32 is merely a relay. Using the common Bosch/Hella etc convention, the green is its #86 terminal & GND its #85 with #30 & #87 being its main/heavy (SPST) contacts.
But irrespective, you need a line that either says the engine is running (or not) or charging (or not).
So what are you intending to use?
If you don't think it's a mere relay, connect 12V across its small terminals. You should hear it click on.
If it were a voltage-sensing (or "smart") isolator, it would only have 3 terminals: the heavy in, heavy out, and GND.
That is really the essence of this thread. I am asking what is, based on the diagrams I have provided, the smartest fuse to tap into.
Originally Posted by OldSpark
It is not a smart isolator. As depicted in the diagram above it has 4 posts.
And my mistake, you are correct in saying the line must dictate that the engine is running (or not), or charging (or not). that is what i meant but I did a poor job of describing that
None of them provide that function.
They are merely battery +12V, IGN +12V, and ACC +12V.
Ok so what do you suggest then I do here? I admire your knowledge and suggestions but I feel we are kind of going in circles here and what should otherwise be (I think) a fairly obvious, short answer to a basic question has turned into a lot of reading and misunderstood information. I am not particularly knowledgeable on how to do this myself and going off of the basic instructions provided to me by Stinger (which can be found here: http://www.stingerelectronics.com/images/pdfs/SGP32-35%20Installation.pdf), I am to connect the 4th terminal to a "true ignition source". That is all I know.
Originally Posted by OldSpark
Perhaps I will phone Stinger for their perspective on this matter. Thank for your time in answering my questions in detail but I'm really just eager to get moving on this without advanced, verbose instructions that assume I'm well-informed on car electrical circuits which I am not. I really don't know how to interpret what you are saying and visualize how to actually go about doing what you suggest.
See my first & 2nd reply.
EG - see Smart Battery Isolator - Reply #7 though there is a newer version of that diagram (which is a re-draw that makes the "mere addition" clearer) as well as several other posts on the subject.
Stinger's "true ignition source" means "ignition +12V" means IGN +12V meaning that the batteries are paralleled whenever IGN is on.
Stinger will probably try to sell you some kind of "smart" isolator and convince you with the usual crap.
Or they'll say IGN etc is fine (as they do on their forum).
Stinger is a rebrander of OP's products. Their core business seems to be profit.
Hi, the possible answers to this question may also be dictated by the type of secondary battery you plan on using and the way you use the PC when the alternator is not running.
There are a number of fuse tap positions you could use. For a simple system, a fuse circuit that has +12v disconnected when the IGN switch engages the starter motor is required for a clean PC power installation, if that is what you are after.
The main and secondary batteries are connected whenever the vehicle ACC or IGN are on but not when it cranks. That would allow the PC system to run from the main and secondary battery most of the time but only from the secondary when the vehicle is off and the PC is in sleep or hibernate and with no chance of discharging the main battery under that condition. This also keeps engine cranking voltage dips and spikes out of the AUX battery / PC supply circuit.
I would use a test light to confirm 100% that a chosen circuit drops +12v in start position. The Radio, ACC and some other circuits should do that but I would always check.
If you want the secondary and main batteries to be connected only when charging then you need to do as OldSpark suggested.
If you don’t want to run extra cabling or connect into the charge indicator circuit then you need to get either a "charge sense relay" (smart isolator?) or a small voltage sense circuit to add to an existing relay. These work by energising the relay at a nominal voltage that would be present only when the alternator is charging the battery, IE +13v or greater.
I’m also answering this from the perspective of getting the cleanest voltage for the Car PC with isolated PC power source when the vehicle is off and NOT from a dual battery /cranking / high power AUX use, as with 4WD camping equipment, etc.
Thanks I will test a light to confirm radio fuse and others.
Ideally, as you have said, I want to have the batteries only paralleled when the IGN is on. If in ACC/off, I would like only the auxiliary battery to be the PC's power source.
Which is "almost" what you have with a relay powered from a true accessory circuit, however you wonít have the batteries in parallel when starting the vehicle. If you want batteries in parallel when starting and are not worried about isolating the PC 12volts from the Vehicle 12volts during engine cranking, you can use two Diodes to make that happen. The relay must be able to handle starting current in the 100ís of amperes though.
Originally Posted by doncarbone
Actually Iím wrong there, if you only want the batteries in parallel when the IGN is on and not in ACC then power it from the IGN line. Some vehicles have a line that drops on Cranking as well but is there only on IGN and not on ACC.
What about once the vehicle is running (after cranking) - they will again be in parallel?
Originally Posted by Mickz
The isolator is rated at 200amps