I never ran across a passenger car with two 12 volt batteries.
Can anyone tell me more? why two instead of one large one? How are they interconnected, just in parallel?
Both my MGAs had two 6 volt batteries located behind the seats wired in parallel creating a 12 volt system. The only 24 volt vehicles I have encountered were military. I’m guessing this mystery vehicle’s batteries are switchable similar to dual fuel tanks.
If I remember correctly, it was an option for our 1999 Suburban 4WD. We opted for a heavy duty radiator in addition (CO mountains).
Sliverado is a truck, and we have at least 1 with 2 batteries, oem, not added on. My bud had his 2nd battery blow up, So it may be like a starting battery and a secondary battery for accessories so as not to kill the starting battery. I would tend to believe the side post bolts are standardized, but a good question for a parts guy.
Wouldn’t two 6v in parallel still be 6v but double the amps? Assuming both have the same amp rating. I think you meant two 6v in series to get 12v.
1 Like
The 1999 Burb was no where near that smart. The interior lights do not timeout and stay on until both batteries are drained. Our experience weekend before last and confirmed with auto parts.
I’m sure you are correct. I have very limited electrician skills. The system was 12v positive ground.
Trucks commonly have a factory option for 2 batteries
One will be the main battery
The other will be the auxiliary battery
here’s some common uses for the auxiliary battery . . .
light bar
liftgate
winch
snowplow
public address systems
1 Like
How does the one alternator charge both? two diodes, so the lowest one gets charged first?
There’s typically an auxiliary battery relay
Here’s a common one
So the answer is the guy didn’t have the correct bolt so used what he had on hand? On my diesel with two batteries, I’d service the connections about every year and replace the bolts to the post. Before I started I made sure I also had on hand the longer bolts needed where the two cables connect to the one battery. I’ve probably still got one left over some place. Personally though, I wouldn’t be very happy with having an allen wrench type bolt in there for fear of stripping it out trying to get it out again.
I have zero knowledge auto electronics.
I googled ‘install instructions auxiliary battery relay’. Frankly, it all looks like Greek to me.
~How much time would it take a competent mechanic to install the relay?
Do you think the time for this procedure is defined and listed in the billable time vs. procedure standards that mechanics now use?
How did we get from possibly having the wrong bolt holding a battery cable on to relays. Even I could take a bolt off and put one on.
I just showed a picture of the relay, because Bill asked how 1 alternator charges 2 batteries
It was not meant as a suggestion or a solution to your problems, and I never said as much, for that matter