Dual Battery Questions

[rruff]

12v batteries in parallel obviously, or 6v in series. The solar charge controller should work fine. Have you thought about where the batteries will be located?

 

[Chips]

12v batteries in parallel obviously, or 6v in series. The solar charge controller should work fine. Have you thought about where the batteries will be located?

I've had a look under the hood and I may be able to fit a second battery in there on the passenger side, but it looks like there isn't enough depth without the hood hinge interfering. I'll need to take some measurements and have a better poke around, I only picked it up last weekend and got it through inspection on Friday. The only other alternative is in the cabin somewhere but I'd rather avoid that if I can. It may be a big SUV but it's a small camper!

 

[DiploStrat]

Two comments:

-- A key controlled relay, a smart/intelligent/voltage sensing relay, and a manual switch are all isolators. Each has advantages/disadvantages. (The one to rule out is any form of diode isolator. Anything like this is a terrible idea: http://www.littelfuse.com/products/battery-management/battery-isolators/diode-battery-isolators.aspx)

-- Solar is wonderful for any lead acid battery set up and can make all the difference in the world. But a solar panel requires a solar controller.

 

[dwh]

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?

For two 12s, yes parallel.

The main drawback to the two paralleled into a full-time bank(one big battery), is lifespan.

All lead-acid batteries have lifespans measured in charge/discharge cycles. Take it down like 20% and recharge and get maybe 3,000 cycles (depending on who made the battery). Take it down 50% and get maybe 1,000 cycles. Take it down 100% and get maybe 300 cycles. (That's for deep cycle type. Cranking type might be wasted after half a dozen deep drains.)

With two in parallel they'll both be going down and up together, and they'll both wear out around the same time. A dedicated starting battery only being drained 1/2% and then recharged will last a whole lot of cycles. The deep cycle, being drained more deeply won't last as long.

Another potential problem is chronic undercharging. Most people don't drive enough hours to fully recharge a battery that has been taken down a good ways (typically say 50%). Letting a lead-acid battery sit around less than fully charged also shortens life.

With a dedicated battery, the starting battery gets drained very little and recharges in a few minutes. The deep cycle might not get fully recharged, but that won't shorten the life of the starting battery.

But with a pair in a full-time bank, both batteries will experience the same usage, and whatever shortens the life of one shortens the life of both.

There's no right way or wrong way here - just different pros and cons.

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?

Yea, no big deal. Permanently tied together it's just one big battery. Doesn't matter which you connect the charge controller to.

 

[AZVern]

I run this set-up. I'm pretty sure the top pic with the Optima Yellow Tops is my truck. The quality of his stuff is outstanding.

https://off-grid-engineering.myshop...-toyota-tacoma-wiring-kit?variant=32470509702

Description of the Blue Sea 7622 ML-ACR 500 amp, dual voltage sensing relay. "Magnetic Latching - Automatic Charging Relay. The is the most robust smart relay available. It is completely automatic and does all the battery linking/ unlinking for you... but also has manual override features for jumpstarting, heavy electrical loads, etc."

I also run an untested Renogy 100 watt suitcase panel for charging the one battery w/a Renogy MPPT controller while I run a Dometic 95. It worked fine without solar last winter on a hunting trip with daily starts. But I'm in AZ and I wanted solar power for fridge along with my Yeti 150 for longer camping trips. We shall see. The math works out.

 

[e60ral]

I run this set-up. I'm pretty sure the top pic with the Optima Yellow Tops is my truck. The quality of his stuff is outstanding.

https://off-grid-engineering.myshop...-toyota-tacoma-wiring-kit?variant=32470509702

Description of the Blue Sea 7622 ML-ACR 500 amp, dual voltage sensing relay. "Magnetic Latching - Automatic Charging Relay. The is the most robust smart relay available. It is completely automatic and does all the battery linking/ unlinking for you... but also has manual override features for jumpstarting, heavy electrical loads, etc."

I also run an untested Renology 100 watt suitcase panel for charging the one battery w/a Renology MPPT controller while I run a Dometic 95. It worked fine without solar last winter on a hunting trip with daily starts. But I'm in AZ and I wanted solar power for fridge along with my Yeti 150 for longer camping trips. We shall see. The math works out.

Just fyi for others, Optima is made in Mexico now and not the same quality as it used to be

Also a yeti 150 isn't nearly enough Ah to run a fridge for any reasonable amount of time

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[AZVern]

Just fyi for others, Optima is made in Mexico now and not the same quality as it used to be

Also a yeti 150 isn't nearly enough Ah to run a fridge for any reasonable amount of time

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My apologies for being unclear. I do not run the fridge off the yeti 150. I run the fridge off of the second battery and the solar. I charge the Yeti off of the same system.

The Optima's have worked fine so far. They were purchased very reasonably priced through Experticity and I've been happy with them. They go well in the Toyota Tacoma built in Mexico too.

 

[Ducky's Dad]

The current Mexican Optimas seem to be fine. I have four of them in two different trucks. The first few years of Mexican manufacture were crap, but they seem to have worked out the kinks.

Couple of points:
1. Most references here to deep cycle batteries should actually be referring to dual purpose batteries (starting and deep cycle). A true deep cycle is not much good for regular duty as a starting battery.
2. Some of you guys have a tendency to overthink the responses to fairly simple and straightforward questions. You know who you are. Carry on.

 

[Chips]

Thanks for all the help, folks. I definitely understand things a lot better. Enough to piece together a system that will work for me, anyway!

 

[rruff]

A true deep cycle is not much good for regular duty as a starting battery.

Per Trojan (and people who have experience with this) deep cycle batteries will start just fine, but the CCA per weight will be a little less than a typical starting battery. So as long as your deep cycle batteries in total are larger than your starting battery, and you have a big cable going to your starter, you should be fine.

 

[Ducky's Dad]

Per Trojan (and people who have experience with this) deep cycle batteries will start just fine, but the CCA per weight will be a little less than a typical starting battery. So as long as your deep cycle batteries in total are larger than your starting battery, and you have a big cable going to your starter, you should be fine.

True deep cycles are fine as a backup to your starting battery, but some here are advocating deep cycles as the primary battery. CCAs are just not comparable to starting batteries. Can you do it? Sure. Is it optimal? Nope.

 

[rruff]

True deep cycles are fine as a backup to your starting battery, but some here are advocating deep cycles as the primary battery. CCAs are just not comparable to starting batteries. Can you do it? Sure. Is it optimal? Nope.

http://www.trojanbattery.com/Tech-Support/FAQ/BatterySelection.aspx

"Can I use my deep-cycle battery as a starting battery?
Deep-cycle batteries can be used for engine starting but starting batteries should not be used for deep-cycle applications. A deep-cycle battery may have less cranking amps per pound than a starting battery, but in most cases a deep-cycle battery is still more than adequate for the purpose of starting an engine."

In my case the deep cycle batteries will be >2x the size of my current starting battery and shouldn't have the slightest problem with cranking loads.

 

[dwh]

Cranking batteries actually do have amp*hour ratings, but because they aren't intended for that use, manufacturer specs don't list the amp*hour rating in the specs for a cranking battery.

Just as deep cycle batteries have cranking amps ratings which usually aren't listed in the specs.

Which is better, one cranking battery that can produce 900 cranking amps, or two deep cycles that can produce 600 cranking amps each (1200 combined)?


Lots of thin plates will dump a lot a of current in a short time, but less and thicker plates can still dump a lot of current in a short time - just not as much as fast as lots of thin plates.

 

[rayra]

Chips the simple answer is a cutoff switch at the main battery positive, a dual battery setup with the combining / charging solenoid, a la the '$50 dual battery' thread. And a simple manual switch to provide power from the Aux battery to the solenoid energizing terminal. You'll want the cutoff on the main battery to disconnect everything from the main battery, but leave the main positive cable and the feeder line to the batter-joining solenoid to remain connected when the cutoff is made.
So you camp, flip the hood and cut off the Starter battery, flip a switch to energize the solenoid and your Aux battery now powers everything in the vehicle.

It's a mod on a mod, but I'm contemplating the same issues in my own power mods, wanting to vehicle camp and use my car stereo / DVD player and rear seat display, without draining my main battery.

Skip over the 'you'll burn your **** down' snark from the resident 'experts' and read about some of the Aux and additional wiring I did for my '02 Sub
http://forum.expeditionportal.com/t...ucture-seeking-inputs-on-my-inputs-and-ouputs

 

[e60ral]

Cranking batteries actually do have amp*hour ratings, but because they aren't intended for that use, manufacturer specs don't list the amp*hour rating in the specs for a cranking battery.

Just as deep cycle batteries have cranking amps ratings which usually aren't listed in the specs.

Which is better, one cranking battery that can produce 900 cranking amps, or two deep cycles that can produce 600 cranking amps each (1200 combined)?


Lots of thin plates will dump a lot a of current in a short time, but less and thicker plates can still dump a lot of current in a short time - just not as much as fast as lots of thin plates.

There are deep cycle dual purpose batteries with more than 900 CCA, the Odyssey 31m deep cycle has 1150 CCA and also 100ah storage and it's not the only deep cycle battery with over 900 CCA

I replaced my factory group 24 battery with 65ah storage (very little of which was usable because it was basically 100% discharged at 12v) with a 105ah group 31 with 800 CCA (which is plenty for my vehicle) and it does fine.

There are plenty of quality dual purpose deep cycle batteries that are absolutely fine to use as your only battery

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