Necessity of Dual Batteries

[atomicshawn]

A friend recently asked about setting up a dual battery system. It got me thinking about mine. I put it together over five years ago using the design outlined in the tech article on Slee's site. Over the years, other than replacing some crappy batteries with better quality ones, I have had zero problems. In fact I rarely ever think about it. Most of the time I forget the system is even there. Unless of course I need the winch, I let the music play a little too long, or someone left a dome light on...

About a month ago I took a small group of adolescent boys I work with camping in the desert for a few days. We were out there aways. 40 - 50 miles off road, and another 50 - 60 miles of highway to the nearest town. Pretty remote, and not a lot of traffic. In fact I'm pretty sure the only tracks we came across were mine from last fall.

On the last day I woke up and found the main was dead. I played it up a little, acted a little panicked to get the boys going. Then popped the hood, turned the switch, and we were on our way.

Other than experiencing some irritation due to the thought of the stupid expensive Odyssey battery, only a couple of years old, was junk and wouldn't hold a charge, there was very little suffering. The dual battery system saved me from catastrophe! (Anyone who has spent time with moody adolescents, and can imagine hiking out of a brutal place like we were in with nothing left to eat but granola, will know that catastrophe is NOT too strong a word.)

This little anecdote, combined with multiple times I've gone out in the morning and turned the key only to hear the "click, click, click..." but still got to work on time, has proven to me the utility of a dual set up. One of my favorite mods, and one I realize I have taken for granted. A necessity? Meh... no, not as long as you bring along extra granola I suppose. But I highly recommend it to all who venture off the tarmac... or have a job.

Shawn

 

[traveldud]

Can you list the setup again or share links? Thx

 

[BadReligion]

I would love to do a dual battery setup on my 80 but I have the big ARB twin compressor mounted where the washer fluid bottle would go. Moving the compressor looks like a PITA and since I probably am doing an engine swap in the next 1-2 years I don't know if its worth the effort....but I know the feeling of being stranded in the middle of nowhere. Last fall my wife and I were camping in eastern NV in some pretty remote terrain. The next morning I went to start the engine and nothing. It would have been a 1.5hr hike just to get cell phone reception, then someone would have had to come out in a 4 wheeler as we were in some terrain that required both lockers to get there. Luckily after popping the hood I realized it was just a loose connection but it still got me thinking. Besides running a dual battery setup, the only other options I can come up with are'

1. packing a fully charged second battery (or one of those battery jump starters)
2. small (1000w) portable generator

Having a small generator (like the Yamaha 1000is) would be nice on extended trips anyway, doesn't take up much space, and can charge a dead battery enough to get it started again. Only downside to this is it might take a few hours, but still better than being stranded for a day plus.

 

[rusty_tlc]

My first dual battery set up was in 1993. No fancy technology just a simple solenoid isolator, stupid simple, stupid reliable. Yeah I had to break out the jumper cables if I let the main go dead, but that wasn't a daily thing so NBD and I always carry jumper cables anyway. While I support the idea of dual battery set-ups I think the products they sell to the offroad community to accomplish the implementation are waaaaay over kill for something so simple. If you want to spend a buttload of money to get the same results you can get from a $30 continuous duty solenoid and a cheap set of jumper cables knock yourself out. I'd rather spend the extra cash on gas or gear or beer.

 

[atomicshawn]

Can you list the setup again or share links? Thx

Again I just used Slee's dual battery tech article. Link as requested: http://www.sleeoffroad.com/technical/tz_dual_batteries.htm
I know there's info in the 60 and 80 (and probably all the other series) section FAQs too, but haven't looked through them.

I do not claim in any way to be an aficionado on dual systems. I rigged another battery on my 80 awhile back. There are probably fancier and maybe more expensive ways of going about it now, high end kits, and maybe that's what you're referring to rusty? I haven't followed it. I want to say when I did mine I spent around $100 plus the battery.

And I'm sure there are simpler ways of having this kind of insurance as you're pointing out rusty, religion. Really, the minimum requirement it would seem is a battery and some jumper cables, presence of mind and patience with the work required to keep the battery maintained. Its the last two items I often lack which makes a more integrated automatic, albeit expensive, system work well for me and worth the added cost. And putting it all together was kind of fun as I recall. An added bonus.

...Besides running a dual battery setup, the only other options I can come up with are'

1. packing a fully charged second battery (or one of those battery jump starters)
2. small (1000w) portable generator

Having a small generator (like the Yamaha 1000is) would be nice on extended trips anyway, doesn't take up much space, and can charge a dead battery enough to get it started again. Only downside to this is it might take a few hours, but still better than being stranded for a day plus.

I personally think a jump box is a great idea. Their relatively cheap. In a pinch you can stick them in place of a battery. I think the down side is limited power, my experience is they get tired pretty quickly. And they don't live long and need to be replaced often. And it's just one more thing you have to find a place to stow.

The generator idea is good, multiple uses. The problem would be if your battery has failed catastrophically, which mine did recently, turned into a voltage sucking black hole, then the generator won't help.

Something else to consider when evaluating the utility of a dual system is it might not be you that needs it. Maybe you're like me and have friends not fortunate enough, or wise enough to drive a Toyota Years ago I was on the HITR trail, a long way from home, and the coil on my friends Defender melted down. He went through a couple of spare coils before we realized the problem was with the voltage regulator. So we had to disconnect his alternator, but he was able to get it out on its own power with no charging system by periodically swapping out batteries with me all the way home.

 

[george_tlc]

Given that batteries DO go flat and fail overnight and many of us DO travel far offroad and often with a fridge with no others nearby an Aux battery is essential.

In oz, I'm often hundreds of miles from the nearest town and often hundreds of miles from the nearest main road. I do take a little honda minibike bush, so I've typically got a 100+ mile range to get to 'something' (maybe). Of course I run an old school diesel back there, so as long as I can spin the starter motor (or roll start on a non-existent hill), that's the limit of what's needed from the electrical system

I have the same scheme in both my 80 and patrol. Continuous duty solenoid to 'combine' the batteries while the alternator is running and a marine switch to select none/1/2/both (for the winch) and it provides the self jump start. Couple of automotive relays to play some 'magic' with the solenoid so it does not activate if the 1/2/both position of the marine switch are in use. With more than 20 years use the system has never failed me, no need for $200+ 'expedition rated systems'...

A mate took a jumpstart unit with him on one trip and it was useful, but of course only as a helper to give an otherwise operational electrical system a boost to get the engine/charging system running.

cheers,
george.

 

[atomicshawn]

Stoked you've had such good luck with that system George. I thought I was jinxing myself by bragging about how reliable that setup is after 5 or 6. 20 years is a long time. Here's hoping I have the same quality stuff.

...and thanks for rubbing in the fact you've got a diesel

 

[Cruiserdrew]

Agree on dual batteries. I was running 2 refrigerators in Death Valley (one with Ice Cream) and it was warmer than I thought and the truck was nearly dead the following morning. Flipped the switch, waited a minute and started right up.

Just installed in my FJ60 a Blue Sea automatic charge relay ($80) and a marine switch also from Blue Sea and think this is a nice integrated solution for my needs. The switch is interesting-it isn't 1/2/both/off, like most, it's off/both on/combined. Makes a clean set up.

 

[canman]

I used my dual battery system quite a few times as well to start the truck after the the main battery was dead. Recently as a couple of weeks ago I had to do this. Very convenient I must say to start the vehicle with the flick of a switch. It does indeed bring peace of mind. I have an Odyessy battery for my aux, and so far after 5 yrs it still is going strong, but it is wired to my veh chassis electrical system, so it always gets used. My original/ starter battery is wired only to the starter.

 

[half k cruiser]

I would be interested in hearing more about your setups @george_tlc @rusty_tlc . I had thought about doing the solenoid as a cheap way to keep a spare lead acid battery charged up. I figured for $20 you can get a solenoid, $70 gets you a fancy OEM box, or cheaper used. My $100 gift card to sears should score me a battery. My thought was to run the winch off of the PS battery only, however, if there was a cost effective way to combine both batteries for a pull then that might be useful. I have no experience with dual setups but would very much like to learn.

 

[george_tlc]

I would be interested in hearing more about your setups @george_tlc ...

For my setup - check out my sig to my website...

cheers,
george.

 

[rusty_tlc]

I would be interested in hearing more about your setups @george_tlc @rusty_tlc . I had thought about doing the solenoid as a cheap way to keep a spare lead acid battery charged up. I figured for $20 you can get a solenoid, $70 gets you a fancy OEM box, or cheaper used. My $100 gift card to sears should score me a battery. My thought was to run the winch off of the PS battery only, however, if there was a cost effective way to combine both batteries for a pull then that might be useful. I have no experience with dual setups but would very much like to learn.

The key is a continuous duty solenoid, you can find them on line or at RV stores. Match the current rating of the solenoid to the output of your alternator and the capacity of the wire you are using. Wiring is simple, one wire from the battery (through a thermal breaker), one to the load , and one to something that is ignition switched, that is to say only hot when the ignition is on. Most RV places will have a schematic you can use to do the wiring.

I don't have dual batteries on anything right now but I do have a charging circuit for my trailer (a little more hassle to lug a battery from the trailer to the engine bay but doable in a pinch). I think I used the radio fuse on my FJ60 and (some accessory I don't have) fuse on the UZJ100. I don't bother with a marine switch since I always carry jumper cables to help other people out and its a pretty simple thing to jump the aux battery to the main. No switch means one less thing to wire and maintain and I'm pretty anal about battery maintenance so it's rarely an issue.

 

[george_tlc]

The nice thing about the marine switch is self jump start is easy (especially for my wife who has needed to do it while I've been away/out of the country) and the other is if you have a winch since it provides you a way to select which battery (or both) is used to power the winch or not when not in use (no paper clip shenanigans).

On one trip the battery in the vehicle that our friends were in died (no warning prior to that), so I removed our main battery (which is smaller than the aux and happened to fit their vehicle) and installed it in theirs and I just rotated the marine switch to the Both position on our 80 so that it would start/run as normal. Benefit of military clamps, you can leave the cables alone and just slip the clamps of the battery.

I've gone a little beyond just Ignition to turn on the solenoid, I use a signal (I call it alternator_good) that fires up ONCE the alternator is running and putting out charge to drive a relay that operates the solenoid. Since the aux does all the aux duties (e.g. fridge, camp lights, ham radio etc) I don't want its discharge state to parallel (via the solenoid) the main battery UNTIL the alternator is putting out charge (i.e. the engine has actually started and running).

Anyhow, lots of ways to skin the cat, mine is just one way.

cheers,
george.

 

[rusty_tlc]

George, where do you pick up the alternator_good signal, or is that a home brew signal?

 

[george_tlc]

George, where do you pick up the alternator_good signal, or is that a home brew signal?

Check out my signature and dual battery write up

Basically it's just the signal that activates the warning bulb on the dash if the alternator/regulator is not 'happy'. I splice into it at the fuse panel behind the main battery and feed that to a automotive relay (low current coil) to activate it.

I have a similar scheme on my patrol, but needed to 'invert' the polarity of the signal.

cheers,
george.

 

[LandCruiserPhil]

For years I went with dual batteries now I run dual batteries wire together in parallel with no controls or expensive dual battery systems and carry an antigravity jump bag. Twice the available capacity as your standard dual battery set up with the back up of a small jump bag. Now with drawing from both batteries at the same time I get much lower over nite discharges and my expensive batteries should last much longer.

 

[george_tlc]

Phil,
so if you have your 2 batteries permanently wired in parallel, how do you know when one has died?

cheers,
george.

 

[LandCruiserPhil]

Phil,
so if you have your 2 batteries permanently wired in parallel, how do you know when one has died?

cheers,
george.

Even prior to dieing your combined voltage will read low giving you a heads up

 

[rusty_tlc]

Even prior to dieing your combined voltage will read low giving you a heads up

One of the biggest advantages of a dual battery system is protecting the individual batteries so if one system has a drain that depletes the battery you have the second system to recover. EX: you leave the lights on, you can jump from the aux battery, or the fridge door is left open and runs down the aux you still have the main battery to use for starting. No experience with the jump bags but it seems like one more piece of gear to carry and maintain to me.

 

[sleeoffroad]

FWIW, we have started to test these little micro battery jumper systems like these.

http://shop.antigravitybatteries.com/micro-start-xp-3/ I honestly thought they are BS, but we tried one on our Limo that seems to always have a dead battery. Well it was so dead that you did not even hear a door chime or nothing. Hooked up that little sucker and sure as SH(*$t it started. Did not think it would do it, but it did. Well worth carrying is a battery backup for not a lot of money.