Dual Battery Questions

[colierar]

So I could just use another car battery with it?

Yes, you can. I use a deep cycle car/boat battery in my set up. Its a pretty sweet set up and you don't have to worry about anything. Its switches between charging the start to full and then it will start charging the house battery. Then when you turn the key to off it separates the batteries electrically.

 

[DiploStrat]

At least Two issues Here

The usual comment is: "I need a dual battery system so that I won't drain my starter battery." This is sort of confuses a cure with the disease.

The REAL question is "How much battery do I need to cover my "camping" needs while still leaving adequate reserve to start the engine." You don't worry about a second battery to run the radio while stopped for a while. The concept is the same - you just need enough battery to cover your needs. (In my case, my camper battery is five times the size of my starter battery. The only reason I still have a starter battery is that I cannot get inside the vehicle wiring to remove it without voiding the warranty and giving the computers fits.)

First, you have to have some reasonable guess of your needs, converted to ampere hours. Hint: With a refrigerator or cooler, you need between 3 and 5Ah, multiplied by the number of hours between engine runs.

So call it 3Ah, overnight, call it 5PM until 9AM or 16 hours = 48Ah. Using the 50% rule for the most cost effective battery life, that means you want a 100 Ah battery to cover your camping needs. (You could, of course, run down the battery more, trading a shorter life for less weight, but that is another discussion.) Use your own numbers to determine your needs.

Soooo, replace your starter battery with two 100Ah deep cycle batteries wired in parallel and you are done. No isolators or other complications.

So why might you want an isolation system?

-- You want to run two different types of batteries - starter and deep cycle.(We will ignore mixing lead acid and lithium for the moment.)
-- You want to run two different sizes of batteries - 100Ah of starter and 400Ah of camper battery.
-- You want to run two different ages of batteries - your starter battery is two years old and in good shape and you really don't want to throw it away.

And the classic: Your starter battery is good (and paid for), and you need more amps than you can fit batteries. So you want to stick in a cheap second battery and beat the stuffings out of it. In this case, you PLAN to actually run it down so low that you could not start the vehicle. I personally think that this is a terrible system design, but user dwh can make a good case for it. In this case, you really do need some form of isolation to protect the starter battery as the camper battery would, in fact, drag it down.

Remember, a battery isolation system is merely a means to an end - it does not necessarily solve your problem.

 

[Chips]

I'm all for keeping things simple and keeping the cost down where I can. This is also my daily driver and I'll be fitting it out so that everything can be removed to switch between daily driver and camping setup.

So I guess I need to grab my multimeter and determine what amps the various vehicle systems like internal lights and stereo are drawing, along with the 12v cooler and a small inverter for charging my laptop. I can't imagine needing any more than that while the engine is off.

 

[Chips]

I live in Quebec and it gets very cold here in winter. Will using deep cycle batteries affect starting performance in cold weather? I use a block heater but it still labors a bit below -20c.

 

[e60ral]

Is the dual battery system made redundant by this?

https://smile.amazon.com/Anker-Powe...chargeable/dp/B0196GQAKM/ref=cm_cd_al_qh_dp_t

You can charge through an inverter while moving, or with a panel while in the field. Light weight and portable.

it serves a different purpose than a dual battery setup

however if this is the direction you are leaning towards I recommend getting the GoalZero Yeti 400 instead, with the Yeti you can chain extra batteries to extend the capacity and the batteries are only $50 each. If you get the Yeti on sale and add a battery, it will have twice the capacity of the Anker for the same price.

I was looking at this option but ended up just replacing my starter battery with a deep cycle

 

[DiploStrat]

Lead acid batteries do not like cold. So, pour les quebecois congelés, there are two numbers needed:

-- Starting load mid winter; that is, how many amps does it take to start that thing, and,
-- Camping load mid-winter and yes, the output of a lead acid battery is lower when it is cold.

The only point is that you don't need an isolation switch if your two batteries are the same type/age AND together they are more than large enough to handle your worst load.

 

[Chips]

I had to look up 'congelés'. I'm Scottish, but I'm working on my French!

I won't be doing any camping mid-winter so that's of no concern. I just want to make sure I can start it in -30c.

 

[DiploStrat]

Sorry, no gaelic in my family!

The good news is that Chevrolets have a very good, temperature compensated charging system. For your use, going to the biggest, baddest, deep cycle batteries you can fit may be the easiest, most cost effective answer.

Now, tell me you want to stick 200Ah in the back, AND use it to self jump, and you will want some form of isolation, ideally automatic with manual override.

 

[e60ral]

I live in Quebec and it gets very cold here in winter. Will using deep cycle batteries affect starting performance in cold weather? I use a block heater but it still labors a bit below -20c.

i don't have any experience in that kind of climate, but lots of "dual purpose" deep cycle batteries have the same CCA as your regular lead acid starting batteries

 

[dwh]

Hmm...

Well, the problem here, is trying to switch the default chassis electrical system over to the secondary battery, which is an unusual way to do things.

The usual way is to add a secondary battery, rig an isolator so the secondary charges while driving, then rig the camping loads to the secondary battery.

Rigged like that, the camping loads don't run the primary battery down, the primary is always ready to start the truck, and the primary doesn't get worn out by getting frequently discharged. Also the primary battery can be a cranking design battery, while the secondary can be a deep cycle design (each is the right tool for the job).


Now, what the OP here wants, is to add a secondary battery to feed the existing chassis electrical system during camping, and have it charge while driving, while still having a battery in reserve to start the truck - without having to rewire the truck so all the loads run from the secondary battery.

Huh. Unusual, but not unreasonable. The essential problem to be solved is to separate the "start engine" function from the "run loads" function.

I see three ways to achieve this, however, two of the three do require some minor rewiring.



The first method...

* Add a second battery, deep cycle type to get the benefits of that while running camping loads.

* Find the wire that feeds the chassis electrical system, disconnect it from the primary (cranking type) battery and shift it over to the secondary battery. Leave the starter connected to the primary battery.

* Add a $50 split-charge relay setup to tie in the secondary battery while the engine is running so the secondary battery gets charged AND so the chassis electrical system gets power from the alternator while the engine is running.



Now for the second method...

* Buy a second battery, deep cycle type to get that benefit while supplying camping loads.

* Mount the deep cycle in the factory default position to feed the chassis electrical system without rewiring. This will also get it charged when the alternator is running.

* Add a mount for a second battery, and put the cranking battery there.

* Find the wire that feeds power to the starter, disconnect it from the deep cycle battery in the default battery position and shift it over to the cranking battery in the auxiliary position.

* Add a split-charge relay to charge the cranking battery while the engine is running.




With either of the first two methods the solenoid and the wiring for the the split-charge relay will have to be rated high enough to handle the full rated output of the alternator, but doesn't have to big enough to handle the draw of the starter - unless the ability to "self-jump" from the deep cycle battery is desired. (Self-jump is a nifty feature, but over-rated in my opinion.)



The third method however is pure and simple a self-jump setup...(and I'm pretty sure someone sells an ACR designed to do this, but can't remember who).

* Leave everything as is, except stick a deep cycle battery in the primary position to feed loads.

* Move the cranking battery to the secondary position.

* Rig a $50 split-charge relay, but use a solenoid and wire rated to handle the full starter draw.


When the key is turned to start, the cranking battery is tied in and supplies the power to start the engine. While the engine is running, both batteries get charged. When the key is off, the cranking battery is isolated and does nothing and the chassis loads all run from the deep cycle.



I would recommend the $50 split-charge relay instead of an ACR for any of these three methods, because I think in this situation, the timer delay and voltage sensing of the ACR would be a liability and could end up defeating the purpose.

 

[Chips]

Thanks dwh. I need to read your post a few more times to digest the information properly but you're correct in what I want to achieve. I'd like to avoid buying, and don't see the point in carrying a second set of lighting, a second music player and fitting secondary power outlets when it's already there and quite conveniently located. It would also be nice to use the ceiling mounted screen to watch a movie on nights that aren't nice enough for sitting outside without worrying about starting the truck the next morning.

 

[DiploStrat]

Methods two or three should work without too much pain or agony, but I still like the idea of simply using two, larger, deep cycle batteries.

This does have the possibility that you could kill both batteries if you really tried, but given the nature of the loads mentioned, I doubt it.

 

[rruff]

The REAL question is "How much battery do I need to cover my "camping" needs while still leaving adequate reserve to start the engine." .... Soooo, replace your starter battery with two 100Ah deep cycle batteries wired in parallel and you are done. No isolators or other complications.

This is what I recommended. Seems easier and more reliable. 2 deep cycle batteries will start the engine easier than a single starting battery. 2 deep cycle batteries will have 2x the camping load capacity of 1.

Downsides:
You need to buy two deep cycle batteries instead of one. But you have 2x the capacity too, and don't have to buy isolators.
If you are really stupid you could drain them both so low that you wouldn't be able to start. If you pay a *little" attention to your batteries though (hook up a voltmeter and check it occasionally) that odds of that are near zero. And you can carry a portable starting pack if it makes you feel better. I lived in a truck for 13 years straight (camping remotely) with no isolated battery and it never failed to start.

 

[mep1811]

I use a smart solenoid. It does not take up as much room as an isolator. I run this with a 220 amp alternator and two GP 27 batteries .

http://dlcparts.com/battery-separator-smart-solenoid-p-1266.html


http://www.hardworkingtrucks.com/gm-1500-dual-battery-install/


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

http://forum.expeditionportal.com/t...ke-a-cheap-isolated-dual-battery-setup-for-50

 

[Chips]

I like the 2 deep cycle batteries idea. Easier to set up and none of the complications of switching. They would be wired in parallel I assume?

Would there be any issue hooking up a 100w solar panel? There will be times when we are parked up for a couple of days and need to keep the cooler running. I'm thinking it's no more complicated than connecting the solar charge controller to the batteries?