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installing dual batteries

ciffer

ciffer

1/2 ton status
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i pulled a secondary battery tray out of a 6.2L 3/4ton suburban, along with the battery wires.

is there anything i need to do when installing a second battery? do i need to buy two new batteries, or can i just add 1 new battery and keep my current battery?
 
Are you going to use an isolator? If using an isolator you just need to buy a new battery for your 2nd battery and wire in an isolator. Surepower is the inventor of battery isolators back in 1959, here is their website. I run there isolator and haven't had any problems in the last 6 years it's been there. Make sure you buy an isolator of the proper size to prevent any fires. http://www.surepower.com/isolator.html
 
what is the advantage of an isolator? i was planning to wire the batteries in parallel like the factory install.
 
An isolator will prevent the older battery from draining the newer battery when it fails, and vice-versa. If you just wire them in series, there is a risk of one battery failing and draining the other. This can lead to real trouble trying to figure out which battery is bad. And when you wire in series, you should always use new batteries, not combine old and new.
 
lectric80 said:
An isolator will prevent the older battery from draining the newer battery when it fails, and vice-versa. If you just wire them in series, there is a risk of one battery failing and draining the other. This can lead to real trouble trying to figure out which battery is bad. And when you wire in series, you should always use new batteries, not combine old and new.
Click to expand...

you are confused on series versus parallel, but i understand what you mean. considering my current battery is in good shape and doesn't need to be replaced, it would be cheaper (and safer) for me to install one new battery and an isolator then it would be to install two new batteries.

which model of isolator would be best?

for a quick lesson on series versus parallel, read this. http://www.otherpower.com/otherpower_battery_wiring.html
 
Yeah, I typed that wrong, but it will still happen, ask me how I know.:wink1:

The Superpower isolators that 4x4high listed are some of the best that I have ever dealt with. I have used Napa versions as well, but I don't know who makes them, and I didn't have to deal with it once it left the shop.
 
i looked around on the surepower site. they list a lot of isolators, some are listed at like "1 alternator, 2 batteries, 160amps". i assume i'll need one for 1 alternator, 2 batteries, but what amperage do i need?
 
You would want one that is higher than the alternator output amperage. Assuming this is for the 88 burb, that would be at least 100 amps. I would say go with a 200 amp model, to allow for future power upgrades. If you have no plans to go with a higher output alternator, go with a 140 amp at a minimum.
 
yep, this is for my 88 suburban. as far as i know it has a stock output alternator, i don't plan to upgrade to higher output. i am installing a second battery mainly to help me start in the winter, it gets COLD here some nights.
 
Then it should have a 95 amp alternator, IIRC, which means you should probably go at least 140 amps. Remember that the manufacturer of the alternator only rates it at 80% of maximum output, so at 95 amps, it could put out as much as 128 amps.
 
do the batteries charge and discharge as normal with an isolator, with the only difference being that the batteries are not directly connected to each other?
 
Yes they charge and discharge as normal, however they are not linked so one is not going to boost the other for starting. If you needed to boost the primary battery for starting, you would have to use large jumper cables to connect them. Under normal use, the secondary battery will be maintained in a charged state, but will not discharge unless it is connected to the trucks electrical system somewhere. The problem with connecting it to the trucks electrical, is you can then have parasitic leaching of power around the isolator.

Usually an isolator is used to keep both batteries charged, while having a second battery that is used for things other than starting. For instance, my dual battery setup will have the primary running the starter, and most of the trucks electrical system, while the secondary battery runs the winch, and audio/video systems. This allows me to run my audio/video systems with the engine off, but never drain my starting battery. It also allows more amperage to go to the winch, while the trucks systems are maintained. I could theoretically run my A/C, while still winching, and have no power issues outside of the alternators ability to keep up with the charging requirements.

If you want to be able to connect the batteries for a boost type system, talk to Ryoken about the proper way to do it. His is setup so that he can run off of each battery, or combine them for heavy draw applications. (I may be wrong on this, but it can be done with a relay type system)
 
was the original purpose of dual batteries in the old chevys to boost starting/glowplugs? i pulled the original wires from the battery tray's donor vehicle and noticed that it is a direct parallel wiring. the donor wiring runs a heavy wire from positive on the primary battery (location of battery in single battery vehicles) to the positive of the second battery, with a heavy ground wire to the engine block.
 
Yes, they originally used that on diesel to boost the starting power, due to the increased drag of a diesel engine. As well as to boost the power for the glowplug preheat cycle. The downside was always the possibility of having a single battery failure that kills both batteries.

There are both relay and battery separators that will boost the battery, while still preventing one battery from killing the second. I haven't dealt with these types of systems enough to give advice on how to do them correctly.
 
i'll have to look at separators. i don't have a winch, aside from the stock am/fm radio, i have no audio video system. the only draw i am really worried about is getting my truck started in -30F air temp in the winter.
 
depends on what you want to do...

isolator...
what I currently use... however I only have a 63 amp alt... and a 90amp isolator....

2 duralast gold 1000 ca batts in parallel... (red to red and black to black)
on leg A of isolator
2 1300ca trucker batteries (each one is the size of 2 normal batteries) in parallel in the bed connected to leg B of isolator...

however I am going to go with the 140Amp alternator so need a new isolator...

instead I decided to go with the stinger relay...
when activated ALL batteries are together... so can be a plus or minus...
pro:
can use either set to start truck

con:
when one set dies they all die as they are ALL being used at the same time

so depends on what you want to do...

I personally went this way because my ramsey patriot 15k winch (with ignition key off) will only use the rear batteries... if they die and I need the extra batteries... I can use the duals under the hood..... but dont have to.....


also... isolators have a voltage drop and relays do not.....
 
Subscribed!

I ran dual batteries on my trip and only did posi to posi and ground to block. I do want to do it the right way next time.

The use I want is a second battery for protection in the out back in case I need a jump.
 
RootBreaker said:
depends on what you want to do...

isolator...
what I currently use... however I only have a 63 amp alt... and a 90amp isolator....

2 duralast gold 1000 ca batts in parallel... (red to red and black to black)
on leg A of isolator
2 1300ca trucker batteries (each one is the size of 2 normal batteries) in parallel in the bed connected to leg B of isolator...

however I am going to go with the 140Amp alternator so need a new isolator...

instead I decided to go with the stinger relay...
when activated ALL batteries are together... so can be a plus or minus...
pro:
can use either set to start truck

con:
when one set dies they all die as they are ALL being used at the same time

so depends on what you want to do...

I personally went this way because my ramsey patriot 15k winch (with ignition key off) will only use the rear batteries... if they die and I need the extra batteries... I can use the duals under the hood..... but dont have to.....


also... isolators have a voltage drop and relays do not.....
Click to expand...
Very good information here. I should point out that the separator is a relay system, and has solid state circuitry to absorb the voltage change and ensure that the batteries are charged by priority. Meaning the primary will be charged first.

I like the Stinger relay setup, it is just more than I need for my plans. And probably more than the OP wants to spend just to boost starting power through the winter months.
 
i looked at the information on the surepower separator site, that looks like what i want. i am a little confused about the start assist feature, it says
"an optional imput from the key switch or a manual switch will program the battery separater to parrallel the batteries during starting." what does that mean as far as the install goes?
 
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