Dual Batteries

[04crewvt]

I have looked at a number of threads out there with conflicting info on how to put together a dual battery system. I am looking for the simplest way to do the following.

1) Dual starting voltage when needed, can be all the time or switched depending on easy of set up.
2) Isolates accessory battery when vehicle is shut off - will be running 12v communications gear and safety lights/strobes.
3) Charges off factory alternator without causing boil-over of weaker battery.
4) Ability to remove accessory battery and still start vehicle if needed.

Any ideas from our resident electrical gurus?

P.S. this is not for the crew so no worries about finding places to mount spare equipment under the hood

[F9K9]

Check out Stu Olsen's thread. Feel free to email him if, you have any questions.

[HenryJ]

Hellroaring Technologies is a source of isolators and combiners.

They include a nice write up and wiring the system , with schematics

[04crewvt]

Thanks for the links guys still as clear as mud (electronic circuits are not my strong point). Brule would this set up work better for my needs?
It looks like with this set up I could remove the accessory battery and the loads associated with it without effecting the starter battery. IE the radio and battery come with me and the truck stays mobile with any accessories tied to the 2nd battery non functional or needing to have there power drawn from the alternate source of the starter battery instead.

[HenryJ]

The difference I see between that one and the one I linked is the load. Smaller loads and not linked as a starting boost. The diagram I linked is wired for larger loads.

You may or may not have considered another approach.

If you are wanting portable 12 volt power and a starting boost, why not KISS?

I too had looked at the possibility of a dual battery system. The only options for mounting are inconvenient or take up valuable load space. After some research I went simple. A nice fairly high amp hour booster pack. I can run accessories off of this or start the truck. In a pinch it is a size that could be used to run the truck in an emergency. Jump start battery pack
If charging is the concern, then how about a small generator? That can charge the truck battery, or the power pack. Lots of small generators are out there not for under $100.
If quick connects are needed look to the cable quick connects that I used for my winch. They make them all sizes. I have a case that I carry my adapters, booster cables, etc. for the winch and generators. My generator can be plugged into the front or rear of my truck to charge it. Those ports are also where I clip the air compressor.

Back to your question. Both will work. The first is for higher loads. The second is for accessory use.

[04crewvt]

The Tahoe has an aux battery tray under the hood already. I was thinking of saving the space in the cargo area and putting the dual battery setup in so I don't have to worry about remembering to charge the jump pack. I have had issues with those and also want the ability to run for at least 24 hours on the reserve battery for the radio rig. The simple method is to just wire in Parallel with no isolation at all, run a separate fuse box from the second battery to the accessories and be done with it but I can't see that as being safe and it won't prevent the main battery from discharging as well. The loads I foresee are as follows light bar/rotator, 12v radio rigs up to 3 possibly with uhf/vhf/800mhz to cover all local agencies, large inverter for 110v loads all will be intermittent use. This is part of the project of turning the Tahoe into a C.E.R.T trailer towing/ECOMM rig and P.O.V. for call outs. Our trailers currently run on 3 deep cell batteries with a 7 pole RV type plug setup. With the second option it looks like I could charge the trailer batteries as well if needed.

[HenryJ]

Schematic two looks like it would serve your low load accessories. It would be a small starting boost. I think you are right in that the trailer batteries could be charged in parallel.

Put a bigger alternator on the top of your list. Start some research on a high idle system. I have not found anything yet, but I have not been looking lately. A load manager may be what would be needed. this shuts down unessential functions as supply decreases.

[04crewvt]

Alternator is part of the research I am doing I have to see what's there now, there is a provision to run dual alternators as well in these trucks with a couple of mods it was an option with the factory towing package I think or at least I have photos of it done. This is all just in the planning stages right now some of this gear might come from the state funds if it's documented correctly and is approved. I would expect the trailer charging part to be at the bottom of the list so the alternator can wait for a while.

PM sent on some details

[HenryJ]

Move the alternator up on the list. It is the pump that feeds everything. Add loads to the system and you must increase the size of the pump. Overwork the little pumps and you look for trouble.

The CS130 on the Tahoe may be the problematic one. The bearings on some models have a plastic race. Bearing failures are starting to surface.

Go to the factory high amp alternator. AD244 would be my suggestion. I have been picking them up used for $50. A simple bolt in addition and a very good investment. I would do that before adding another battery.

[04crewvt]

I will have to see what's around, not a lot of junk yards anymore up this way, scrap metal is worth too much so most vehicles are heading to Canada to be recycled. There are a few so who knows what I may find. where do I look on them to figure out what they are and what are they most likely to be in?

[HenryJ]

Check the bigger alternator thread. The difference is obvious and easy to pick out. Any fullsize Chevrolet could have one. Look for newer being better, but anything from 1998-up could be a likely candidate. They may be inventoried as the High Output alternator. Tell them that and the price may go up though. Find one and just buy it as an alternator and the price may be less
130-160 amp versions are out there. All will bench over 200 amps cold. Idling they will put out 100 amps cold. That is more than the stock one will do under best conditions at full output.

[WileyHunter]

I just woke up so forgive me if I miss something here, but...

Sch. 1 looks like it covers your need to "boost" the start up as needed, but Sch. 2 doesn't look to help with that at all.

Biggest problem I see with BOTH of these options though, is charging. It looks to me as if you will only be able to charge the second battery IF the "aux" switch is activated... And yes, you'll need a higher capacity Alternator to achieve that as well.

Personally, I'd just hook it up in parallel, throw a High Cap Alternator at it and be done with it... With a switchable set-up, unless you completely isolate the battery from any/all loads it will trickle discharge on you and eventually won't be capable of fully recharging without going through a deep cycle several times (and then you are still losing a little of the total battery capacity).

WH

[HenryJ]

I believe that The Hellroaring Isolator / Combiner takes care of both the boost to the starting battery as well as charging both. The "smart circuitry" in in charge of that. You select to combine or isolate. It senses the charging needs internally.

[04crewvt]

Looked at the alternator thread and under the hood of the Tahoe this AM. It appears I already have the AD244 it looks like the photos at least and it does not look like the stock Crew alternator.

[HenryJ]

RPO codes will tell the tale. There is also an etched rating on the top. Should read 130A or something like that.

[04crewvt]

Numbers are not matching up but from looking at RPO codes it appears to be a cs144 140amp unit. 3.42 gear ratio, g80 locker,HD oil and trans cooler,z82 trailering package(hitch and tow hooks along with the hd cooling stuff and high capacity air cleaner). GM Trucks RPO Codes

[green02crew]

I too am looking at a dual battery setup. I want to keep it very simple and want the battery there in case of emergency and if needed for a jump start or cold start day. I like the booster pack that I have but don't desire to keep it with me all the time. I have the second battery tray built in and unused. I would like to either pick up a second booster pack and mount it there under the hood with a built in compressor for emergencies or a full second battery that I would pop the hood and charge every now and then. Thoughts on that? There is only so much storage under the rear seats.

[HenryJ]

BLT Offroad Avalanche

[green02crew]

What is the isolator you wired it to charge from?

[HenryJ]

What is the isolator you wired it to charge from?

Just a basic isolator. A series of diodes up to a given amp rating. I believe this one has three 50 amp diodes? (might have been four?)

Think of it as a tee in the line with check valves.

Looks like they run around $40 Battery isolator (Amazon) $36.38

[green02crew]

Without the shut off switch will the main battery die then go on to kill the reserve?
Also, if the main battery were to die, will it auto switch to the strong backup battery and get you started?

[HenryJ]

Without the shut off switch will the main battery die then go on to kill the reserve?

They will die together. Connected in parallel both act as one large battery. They need to be the same size, design and age to work well.

... if the main battery were to die, will it auto switch to the strong backup battery and get you started?

No. I manually turn the switch , combining the two batteries in parallel to "jump start" myself.

[green02crew]

Okay last couple of questions...
Is an in line fuse needed with this setup whether in the supply or output from the aux battery?
You're running two positives to the backup battery, correct? One to charge and one to jump start?
What gauge wire are you running for charging purposes?
My alt output is 145amp, so would you recommend going up to the 200amp version or is the 140amp sufficient?
Where did you tap in for the isolator activator?

[green02crew]

Little bit of update with this...
I found next to my open battery tray a positive terminal that goes to the main input blade for the fuse block. This is normally used for accessories such as the power for trailer battery charging through the 7 pin connector. If I wire it to this would that work or would it provide power to the truck all the time?

[HenryJ]

Is an in line fuse needed with this setup whether in the supply or output from the aux battery?

There may be a fusible link in the wire from the alternator. Mine has one. I did not add one to or from the isolator. The diodes will fail and act as fuses in the event of a short.

You're running two positives to the backup battery, correct? One to charge and one to jump start?

Correct. One 8ga wire from the isolator and a 4ga cable to the switch.

What gauge wire are you running for charging purposes?

Using this table you can see that 5' of 8 ga. is sufficient to deliver 140 amps from the alternator and that 7' of 4ga. cable to the main battery can deliver over 200 amps.

My alt output is 145amp, so would you recommend going up to the 200amp version or is the 140amp sufficient?

Over kill is never a bad thing, however in this case that may be way beyond what is needed. Do you ever see a need to draw more than 140 amperes from the auxiliary battery without it being combined? My highest draw accessory is connected to the main battery. The winch is capable of drawing beyond the output of my alternator. With both batteries combined the full output of the alternator has two paths for amperage to flow. If it takes the path of least resistance I hardly think it would overload the isolator. IMO, the 140 amp isolator is plenty for the auxiliary battery.

Where did you tap in for the isolator activator?

I did not. The one that you are describing must be different and use something other than simple diodes? Perhaps just an ignition activated safety? I would follow the directions included for installation. You can pick up an ignition wire in the electrical center I suspect. Wipers, maybe?
It looks like the higher amperage isolators do not include an ignition terminal? Perhaps mine is indeed a 200 amp isolator and did have four or five 50 amp diodes? It was one I had lying around so I really do not recall the make or details. No paperwork or purchase to look back upon.

[green02crew]

I finally found a GM installation of the dual battery setup and it is complicated:

http://chevyavalanchefanclub.com/cafcna ... 506.0.html

I had planned on running a more simple setup and attaching the second battery to the trailer power provisions stud on the fuse block. This is hot all the time though and would cause me to run the batteries in parallel which is not what I had in mind. I was thinking that it would allow me to run all my accessories off the second battery saving the main one for startup, not the case. I may still be able to use that pin to charge the aux battery though.

HJ, would it be any different hooking an under hood battery directly up to the trailer power lug as apposed to leaving a trailer with built in battery plugged in all the time?
That would allow me to use the main fuse block for charging (with an isolator) and then just run a manual shut off to the main battery for a jump start?

[green02crew]

This is what I had in mind.

Edit: I may be able to just put in another shut off instead of an electrical isolator and that would enable me to flip it every now and then to keep it charged while the truck is running and going on trips then shut if off again. It would just involve popping the hood more often.

[HenryJ]

...would it be any different hooking an under hood battery directly up to the trailer power lug as apposed to leaving a trailer with built in battery plugged in all the time?

Yes. The line loss would be a killer. It is best to have the pipes as short as possible to move the water. A pipe that long needs time to fill the lake. That is why the wire from the trailer connector is a charging wire instead of source.
Charging the aux battery is best taken from the source. Direct from the alternator is the most efficient. As short a run as possible.

[green02crew]

So although not efficient, it would work just to keep the aux battery charged?
It is only about a foot from the trailer power lug which is coming out of the distribution box.
I would most likely put a switch on it to just isolate it from the box so no back feed when not charging. If it can charge a trailer battery behind the truck, it should be able to a foot away although not ideal.

[HenryJ]

Things change. The BIG battery packs are getting smaller. Options for a jump pack in your hip pocket now exist. The Antigravity XP-1 really looks like an awesome little pack to keep in the pocket of my 100W solar panel case. Right size and offers all the adapters to power what ever I might want to. Small enough to stow under the back seat, or in a glove box. Reports say it will stay charged for up to a year.
I picked one up on Amazon for $144 shipped.
I will say that the video did help sell it:

I had seen another thread on the lithium battery booster pack, but lost track of it. The whole idea stuck with me and when a little mad money showed up, I bit the bullet. I had been wanting to experiment with a pack like this and see if the solar panels work well in conjunction. At the very least this will be much more convenient to carry as a back up plan. It also gives be the ability to carry it along on the motorcycles too. I like that idea

[green02crew]

Now that looks like a convenient product. Their warranty is listed as 3 years but the fine print has me worried. When my Duracell booster pack dies this is my next purchase if all goes well with you being the test subject! Thanks for sharing and keep us updated on this!

[HenryJ]

Solar panel works just fine to charge up the Antigravity XP-1



I had to add a power port to the panel for charging an accessory like this. That should also allow me to plug another panel into the equation. Just a big junction block for the batteries. Kind funny to see the old school fuse inline, but that was what was already there

Not a real world test as the battery was not down much. The panel is inside getting only partial sunlight from the window. Still , it topped off in a few minutes.

[ApproachMedium]

So the XP-1 is probably more like a super cap than a battery. Have you seen these youtube people starting up toyotas and running them off tiny banks of supercaps? Its pretty cool. We started using them in the model railroad hobby to keep the trains running over dirty track after the real railroads started using them to keep the lights on during power interruptions, and now they even have street cars that can run for short distances without the wires!

Where did you get the solar panel from? Would be nice to put one of these in to both of my cars so that I can have some extended radio play while I am out trackside for hours watching stuff go by.

[HenryJ]

Here is the panel. 100 Watt Foldable 12 Volt Solar Panel
A steal at that price.

From what I have read about the XP-1 , it is Lithium iron phosphate. It don't know enough about how it dumps the power, but you may be right that it acts more like a cap.

[ApproachMedium]

Not bad! I may have to get one of these before my next trip. Which wont be for a long time unfortunately.

[HenryJ]

I have been watching panels for a very long time now. That is the best price ever. Nice controller and good heavy cables with both clamps and a power port cable. Comes with a bag too.
I already had one that I paid 1/3 more, but had to get another one at that price.
I figure that I will keep one in the truck all the time now. Two in the trailer. This should have us covered for indefinite off grid use.