How to make a cheap isolated dual-battery setup for $50

Ozarker

Explorer
No, in 40 years of being a gear head I've never heard of a single incident of a car battery exploding.

If you read the whole quote, I was saying that only a bad/over charge battery would went enough in the NON airtight space of a car to be an issue. MILLIONS of cars for DECADES have the batteries installed INSIDE the passenger compartment.

As a matter of fact, the highest production car on the planet, ever, has the batter under the rear seat behind the driver! Produced that way from the 1940s to the 1980s.

Is there always the 1 in a million exception? Sure! So its "Possible" but the "probability" of an issue, especially with modern batteries, is extremely low.
That being the VW Bug, but the entire VW line had batteries under the seat in those years, very handy spot too. :)
What was scary was where the aux gas heaters inside the bugs.

I have never seen a battery, any battery explode, saw one burn, but not explode. Did see an old lead acid that appeared to have blown up, the guy claimed it blew up, by blown up I mean the top busted open and side pushed out exposing plates, it was in a salvage yard and he nor I saw it blow, so something else may have caused that damage. I doubt it just blew up setting outside.
 

Cole

Expedition Leader
That being the VW Bug, but the entire VW line had batteries under the seat in those years, very handy spot too. :)
What was scary was where the aux gas heaters inside the bugs.

I have never seen a battery, any battery explode, saw one burn, but not explode. Did see an old lead acid that appeared to have blown up, the guy claimed it blew up, by blown up I mean the top busted open and side pushed out exposing plates, it was in a salvage yard and he nor I saw it blow, so something else may have caused that damage. I doubt it just blew up setting outside.
Yeah. I only mention the bug because of its history. Many modern cars have batteries inside but of course they are "sealed" these days. I have 3 German cars newer than 2002 that have the batteries inside the passenger cabin. Two of the are under the drivers seat.
 

hinocairnseclipse

New member
I have seen one of these batteries explode, it was an n70z, we use two of them on each work truck for 24V. The battery was fairly old, it was on the truck when we bought it, and the side of the battery was curved outwards a little.
One day the driver started the truck and an almighty POP!
Fortunately I was on the opposite side of the truck when it happened, because when I went around the truck: the entire side of the battery was missing, and acid sprayed 180 degrees for a few metres
 

daddyusmaximus

Explorer
It happens. I stalled my vehicle in a water crossing 20 years ago. Wouldn't re-start. I cranked and cranked... BOOM! Got lucky though, the hood was closed, so nobody got sprayed. Also, even though the case was ripped apart and the acid was gone, the plates were still all connected. After I got everything dry, she started my vehicle and I was able to make it to a Sears for a new Die Hard. Shop guys were freaked out that my exploded battery still had a charge and worked... They started my car several times for their co workers before putting in the new one.
 

pixelcodex

Observer
Portable second battery setup?

Ok, so I have wanted a fridge for a while and recently scored a used one off Craigslist. Cleaned it up, sanded and painted and looks pretty decent. Now I want to hook it up to my Grand Cherokee, making a wood slider in the process. What I want to incorporate a second battery (I have one laying around) inside a battery box, which would hook up to the cigarette lighter I have in the back to charge, and in turn hooking up to the fridge to provide juice for it. Now, I want to hopefully make this setup portable to take on and off the truck as needed. Is it advisable to have the second battery inside the cabin? Any downsides to this? Anything else I need to be concerned about? Thanks in advance for your expertise.
 

Mcstiggens

New member
Question about voltage readings @ isolator and house batts.

Howdy Gang,

I just used this most excellent thread to hook up the isolator system complete with solar.
My question is, shouldn't the voltage reading on the house battery read the same or similar to the starter battery when the truck is running?
For instance, when I have the truck idling, I get a reading of 14.44v at the truck battery as well as the input post of the isolator.
But on the the output post of iso as well as the house battery I get only 12.75v.
Is that right or should i be getting 14.44v all around?
Sorry if this has been addressed already, I don't have the time to scan the whole thread.

Thanks for the input.

Mcstiggs
 

dlichterman

Explorer
Howdy Gang,

I just used this most excellent thread to hook up the isolator system complete with solar.
My question is, shouldn't the voltage reading on the house battery read the same or similar to the starter battery when the truck is running?
For instance, when I have the truck idling, I get a reading of 14.44v at the truck battery as well as the input post of the isolator.
But on the the output post of iso as well as the house battery I get only 12.75v.
Is that right or should i be getting 14.44v all around?
Sorry if this has been addressed already, I don't have the time to scan the whole thread.

Thanks for the input.

Mcstiggs
What voltage are you getting when the truck is off and solar is disconnected. Sounds like something isn't connected right as long as you used a good size wire.
 

bronconite

Observer
Howdy Gang,

I just used this most excellent thread to hook up the isolator system complete with solar.
My question is, shouldn't the voltage reading on the house battery read the same or similar to the starter battery when the truck is running?
For instance, when I have the truck idling, I get a reading of 14.44v at the truck battery as well as the input post of the isolator.
But on the the output post of iso as well as the house battery I get only 12.75v.
Is that right or should i be getting 14.44v all around?
Sorry if this has been addressed already, I don't have the time to scan the whole thread.

Thanks for the input.

Mcstiggs
It's discussed a bit in this thread. Here is the post that somewhat explains it http://www.expeditionportal.com/for...al-battery-setup-for-50?p=1110205#post1110205 , although the voltage drop your experiencing seems to be more than what's normally expected.
 

Mcstiggens

New member
What voltage are you getting when the truck is off and solar is disconnected. Sounds like something isn't connected right as long as you used a good size wire.
With a fully charged battery, the truck turned off, the truck reads 12.79 and the house reads 12.80.
With the truck at idle after 10 minutes, the truck reads 14.78 and the house reads 12.85. So I guess if the isolator
(a 200amp isolator) is meant to only provide a slight trickle, I guess it's working. I just don't know if thats even
enough to call it a 'slight trickle'.

One thing to note,
The only difference is that on that schematic, he shows the neg. from the house battery going directly to the truck battery neg.
I just ran the neg from the house down to a good frame location. Seems like 6 one, half a dozen the other to me......or am I missing something?
Also, I used good quality 4ga wire for the iso connections. The only bummer is that i was short of wire by about 4 feet so I had to use an 8ga but connector
(all i could get) to make the connection which kinda negates the use of the 4 ga I guess. Could it have that much effect?

Thanks for the input fellas.
Stiggs

Thanks for the input guys,
Mcstiggs
 

dlichterman

Explorer
With a fully charged battery, the truck turned off, the truck reads 12.79 and the house reads 12.80.
With the truck at idle after 10 minutes, the truck reads 14.78 and the house reads 12.85. So I guess if the isolator
(a 200amp isolator) is meant to only provide a slight trickle, I guess it's working. I just don't know if thats even
enough to call it a 'slight trickle'.

One thing to note,
The only difference is that on that schematic, he shows the neg. from the house battery going directly to the truck battery neg.
I just ran the neg from the house down to a good frame location. Seems like 6 one, half a dozen the other to me......or am I missing something?
Also, I used good quality 4ga wire for the iso connections. The only bummer is that i was short of wire by about 4 feet so I had to use an 8ga but connector
(all i could get) to make the connection which kinda negates the use of the 4 ga I guess. Could it have that much effect?

Thanks for the input fellas.
Stiggs

Thanks for the input guys,
Mcstiggs
Ah, sounds like a bad ground. With my 4awg both ways I read 14.5 at the second even after 22ft. This is why I ran the full thing. Did you use something abrasive on the frame before grounding?
 

Mcstiggens

New member
Ah, sounds like a bad ground. With my 4awg both ways I read 14.5 at the second even after 22ft. This is why I ran the full thing. Did you use something abrasive on the frame before grounding?
That would make sense. Yea, i did grind the frame down to bare metal.
 

Mcstiggens

New member
Also check the battery side, maybe something is loose. I have a rather embarrassing tale of replacing my starter, when it was loose battery connectors.
Yea, all the connections are rock solid. I even double checked and re-grinded the ground spot on the frame. It's nothing but fresh, bare steel. I'm at a loss.
the only thing I can try now is take the ground wire up to the truck battery. that just means another trip to town for more wire though, dammit.
I still don't get why that would be an issue though. Last I checked, the frame, engine block, neg battery were ALL ground.
 
Top