Noob Vehicle 12v electrical: best way to run a second battery?

[Thatg9659]

So put it together right and use glue type heat shrink.

Was Like that way when I got it, no crank no start maybe helped the price I got some fancy BMW X5 battery leads to someday put on it.

 

[87manche]

Was Like that way when I got it, no crank no start maybe helped the price I got some fancy BMW X5 battery leads to someday put on it.

careful bout that exploding battery terminal.

 

[AgitatedPancake]

What's the internal logic that average battery isolators use to connect and disconnect the circuits? I've always known about them, but not what makes them tick. I just read one description that essentially connects the batteries together between (appx) 12.5v-16v, then disconnects them if they go above or below that range.

Is it really that simple, or is that just a very simple version? I always figured there was more sensing going on for some reason

 

[87manche]

What's the internal logic that average battery isolators use to connect and disconnect the circuits? I've always known about them, but not what makes them tick. I just read one description that essentially connects the batteries together between (appx) 12.5v-16v, then disconnects them if they go above or below that range.

Is it really that simple, or is that just a very simple version? I always figured there was more sensing going on for some reason

most are just using diodes. That's why the voltage drop.

the super fancy ones use a voltage sensing switch controlled by electronics to connect/disconnect the batteries automagically. Sees above 13V on the supply? connects battery. Less than that, disconnects.

 

[AKnate]

I use one for these mounted in a plastic wall switch box.

https://www.amazon.com/HELLA-002843011-Rating-Battery-Master/dp/B0000AYAFE/ref=sr_1_3?crid=356P87OAKMFS1&keywords=hella+battery+master+switch&qid=1661985681&sprefix=Hella+battery+master+swi%2Caps%2C90&sr=8-3

that interrupts the power. I run a ground back to the battery. 4 gauge is plenty. Run the hot in plastic conduit/wire loom, pex scraps, etc.

recently I attached a small Prius agm battery to an Engel fridge and used a lighter plug to charge it when the truck was running. Worked great but not cost effective unless you have recently parted out a Prius.

I'd use a quality Cole-Hersee switch vs that thing. They aren't much more $$ and a good chunka chunka switch.

 

[DMG]

I'd use a quality Cole-Hersee switch vs that thing. They aren't much more $$ and a good chunka chunka switch.

Nothing wrong with those either. I think if it is pulling more than 100 amps he has a problem, though.

 

[AKnate]

Nothing wrong with those either. I think if it is pulling more than 100 amps he has a problem, though.

Had a truck nearly burn down from a crappy master switch. It melted down and grounded out. Don't remember the brand, but it was very similar to that plastic Hella version.

I started putting the switches on the ground vs power after that if at all possible too.

 

[ExWrench]

I started putting the switches on the ground vs power after that if at all possible too.

So every component and wire it hot? That sounds sparktacular.

I guess you'd need a shorter jumper wire to test anything, though

 

[larboc]

I'd use a quality Cole-Hersee switch vs that thing. They aren't much more $$ and a good chunka chunka switch.

Agreed, I've seen those hella style and they are chincy.
I've got one of the perko marine units on my boat, never any issues. They have some with charging diodes.

https://www.amazon.com/Perko-8501DP-Marine-Battery-Selector/dp/B00144B6AE/ref=mp_s_a_1_4?crid=2BMDEXWHRG5YV&keywords=marine+battery+switch&qid=1661997586&sprefix=marine+battery+mas+switch%2Caps%2C813&sr=8-4

 

[larboc]

Yup and couple that with using QUALITY wire makes it work. Stereo 4 gauge will flow better than automotive grade 0 gauge.

Unless you are talking about Cu clad Al, that statement is complete B.S.

Cu. vs. Cu. , the voltage drop is virtually the same for all AWG's. Insulation temperature rating is what changes the maximum current rating.

 

[DWT]

Unless you are talking about Cu clad Al, that statement is complete B.S.

Cu. vs. Cu. , the voltage drop is virtually the same for all AWG's. Insulation temperature rating is what changes the maximum current rating.

So 22 gauge solid core wire flows the same current as 00 1000 strand if the 22 gauge has higher temp insulation?


You know as well as I do that typical automotive wire has 10-12 strands and the wire quantity inside the insulation is half of what audio grade cable is.

 

[M92PV4U]

So every component and wire it hot? That sounds sparktacular.


I guess you'd need a shorter jumper wire to test anything, though

Nothing will be hot if you remove the ground, but the alternator will keep the engine running if the deadman switch is switching the ground...

 

[DWT]

Nothing will be hot if you remove the ground, but the alternator will keep the engine running if the deadman switch is switching the ground...

How can it charge without a circuit?

 

[M92PV4U]

How can it charge without a circuit?

I don't understand that, it's just how we have to wire racecars. If you unhook the negative battery cable of a carburetorated vehicle it will continue to run.

 

[M92PV4U]

How can it charge without a circuit?

I don't understand that, it's just how we have to wire racecars. If you unhook the negative battery cable of a carburetorated vehicle it will continue to run.

Fuck that doesn't make since to me anymore and I can't remember how I wired the deadman switch last.

 

[ExWrench]

Nothing will be hot if you remove the ground

Ahh, my brain fart - I read "putting the switches on the ground" and thought about circuit switches, not main disconnect

 

[PAE]

Sorry but I call BS on this statement.

Ive been in the auto electric industry for 20+ years and I've seen plenty of line loss on smaller size wire over a distance in a automotive application, and have measured it with electronic ohh instruments, the more wires the better and insulation does squat to increase or decrease line loss.

Unless you are talking about Cu clad Al, that statement is complete B.S.

Cu. vs. Cu. , the voltage drop is virtually the same for all AWG's. Insulation temperature rating is what changes the maximum current rating.

 

[larboc]

So 22 gauge solid core wire flows the same current as 00 1000 strand if the 22 gauge has higher temp insulation?


You know as well as I do that typical automotive wire has 10-12 strands and the wire quantity inside the insulation is half of what audio grade cable is.

?

22awg solid is rated for more current than 22awg stranded with the same insulation.

"Automotive grade wire" if you are talking about SXL has an even better rating of 125C.

What are you calling "audio cable"? I'd guess the insulation is not as good as SXL.

Cu purity for the wire we're talking about is virtualy irrelevant.

 

[Greg__]

most isolators have a slight voltage drop to the aux battery. You magnify that when you put the isolator at the long end of the battery cable that's already induced a voltage drop.

0.7 VDC is normal for a diode. Way worse than 'slight'

 

[mobil1syn]

just did this on my tahoe, i plan to upgrade the alternator because the tahoe sits quite a bit now that i have a company van, so the battery goes flat pretty quick when i want to run the fridge and dont have extended drive times in between.

2 awg would be the min id consider for the battery run between the isolator and second battery. also i prefer to keeps systems isolated so would avoid hooking to the isolator.

upgraded the factory wiring from alternator, 4 - 10awg

solid state isolator, i like technology. self sensing and will switch off when it senses below 13.5 volts. also has an option to back feed the aux battery to main for a flat recovery - InPower ABS3-200A Auxiliary Battery Switch, 200A, 12V, Dual Lug | Waytek

you can see the 0/2 guage from the isolator to the second battery (yellow top in this case), hung a fuse box off the side terminal

10awg all the way to the back for the fridge

 

[DWT]

?

22awg solid is rated for more current than 22awg stranded with the same insulation.

"Automotive grade wire" if you are talking about SXL has an even better rating of 125C.

What are you calling "audio cable"? I'd guess the insulation is not as good as SXL.

Cu purity for the wire we're talking about is virtualy irrelevant.

You're missing the point completely. Good quality audio cable will have easily double the amount of copper vs automotive grade in the same given gauge.

 

[[486]]

most isolators have a slight voltage drop to the aux battery. You magnify that when you put the isolator at the long end of the battery cable that's already induced a voltage drop.

that's why they run the alt wire to the isolator, then the volt sense wire to one of the two batteries
then you're still getting your 14.7 or whatever at the batteries, even if the isolator's seeing 15.5v or whatever at its input terminal

 

[[486]]

Yup and couple that with using QUALITY wire makes it work. Stereo 4 gauge will flow better than automotive grade 0 gauge.

fine strand wire only matters at high frequencies
at 60hz, skin depth is like 5/16" iirc
DC, it is infinite

also, lots of stereo wire is copper plated aluminum which is really good for corroding completely off even with good double wall heatshrink on it

 

[trampas]

fine strand wire only matters at high frequencies
at 60hz, skin depth is like 5/16" iirc
DC, it is infinite

correct, 65% depth with ac, infinite with dc.

which is why strand quantity isn't important with dc cabling.

stereo output is ac, fine strand is desirable in that instance

 

[DWT]

fine strand wire only matters at high frequencies
at 60hz, skin depth is like 5/16" iirc
DC, it is infinite

also, lots of stereo wire is copper plated aluminum which is really good for corroding completely off even with good double wall heatshrink on it

Correct but you're still missing my point that I apparently suck at explaining. Good quality 4 gauge audio cable will be easily 3/8" of copper wire (I use OFC wire not that copper clad shit) while automotive grade 4 gauge will be 3/16-1/4" of copper inside of it.


That's what I've been trying to convey and failing at doing. The difference between them is stupid. It harkens back to my first post about audio 4 gauge being better than automotive 0.

 

[arse_sidewards]

Add a breaker if you want. run 2AWG and you'll be fine for pretty much everything.

The cheapest source of decent quality 2AWG at present is HF jumper cables.

I just went through this when making extensions for my welding leads.

 

[FleshEater]

I use one for these mounted in a plastic wall switch box.

https://www.amazon.com/HELLA-002843011-Rating-Battery-Master/dp/B0000AYAFE/ref=sr_1_3?crid=356P87OAKMFS1&keywords=hella+battery+master+switch&qid=1661985681&sprefix=Hella+battery+master+swi%2Caps%2C90&sr=8-3

that interrupts the power. I run a ground back to the battery. 4 gauge is plenty. Run the hot in plastic conduit/wire loom, pex scraps, etc.

recently I attached a small Prius agm battery to an Engel fridge and used a lighter plug to charge it when the truck was running. Worked great but not cost effective unless you have recently parted out a Prius.

I also ended up just hooking my fridge to an AGM.

Although, I didn’t have a 2BB with free wire either.

So, I run the fridge off the starting/main battery while driving, and then when parked I plug into a fully charged AGM Intimidator battery. Tested the AGM in my house and it kept the fridge running fine for 7 days straight. So technically I don’t need the main battery, but it’s a good back up.

 

[Bebop]

I love that everybody is fighting in the comments on how to wire 2 simple batteries in parallel.

Harry Johnson : Look at the OEM wiring on a HD truck with dual batteries and copy that. If you want to make the batteries independent from each other, just add a battery switch in the middle. There is no breaker or fuse between your battery and the starter and this is arguably a much more stressed wire compared to the ones you're gonna put between the 2 batteries. So I don't see the point of fusing those ones.

 

[DMG]

I love that everybody is fighting in the comments on how to wire 2 simple batteries in parallel.

Harry Johnson : Look at the OEM wiring on a HD truck with dual batteries and copy that. If you want to make the batteries independent from each other, just add a battery switch in the middle. There is no breaker or fuse between your battery and the starter and this is arguably a much more stressed wire compared to the ones you're gonna put between the 2 batteries. So I don't see the point of fusing those ones.

The point of fusing them is to prevent fire when you have 20 feet of positive cable running all over the vehicle to a fridge etc in the rear. It can be pinched or abraded by a grounded chassis or body part and create a short. If the battery or load is a foot away, no big deal. there is t much to go wrong.

 

[87manche]

I love that everybody is fighting in the comments on how to wire 2 simple batteries in parallel.

Harry Johnson : Look at the OEM wiring on a HD truck with dual batteries and copy that. If you want to make the batteries independent from each other, just add a battery switch in the middle. There is no breaker or fuse between your battery and the starter and this is arguably a much more stressed wire compared to the ones you're gonna put between the 2 batteries. So I don't see the point of fusing those ones.

the OEM wires are also ran properly and with great care to make sure that they don't chafe or get damaged.

a fuse is cheap insurance against your added in wire chafing, shorting and burning down your shit.