Dual Battery System Setup

[Guest]

Hi,

I might look into installing a second battery for my vehicle for the purpose of running
a small fridge.

I am looking at DBE140S Electronic Dual battery management and isolator which is
pretty straight forward to wire up.

Lets say the car fridge uses 2A/hr and the battery is 130AH is it safe to say
the battery should run the cat fridge for 50 hours?

The next question is could I use a solar system to charge the battery while its
been using by the fridge and what size solar panels/system would I need?

If the battery does not get used for a while is this ok?

Thanks for your help.

 

[300]

Hi ivejust been through all this my self this is what I came up with for every 100ah battery you need 250watts solar panel it's that simple this way the battery will substantially recharge on days of little or no sun and the battery will last years longer.I hope this helps it can get very confusing.

 

[Redfin]

Hi Wolf. I have a 47L Evakool running as fridge only with a dual battery system.[ 105 ah Fullriver]
I only run it for drinks, and I am a thirsty sorta bloke, and can open it up to 18 times a day.
I like to run it at 2C.
Most i have ever been stationary is two and a half days in Dunolly heat, and low battery alarm did not kick in.
I am not a gauge watcher or multi meter man.
a 20 or 30 minute run usually brings you back to scratch.

 

[kemjak57]

I like the reference to the amount of times it gets opened. If I did that I'd need a stick to open it from the ground cause that's where I'd be laying

 

[Redfin]

a few bottles of H2O in that lot my man, but only a few.

 

[casper]

Hi,

I might look into installing a second battery for my vehicle for the purpose of running
a small fridge.

I am looking at DBE140S Electronic Dual battery management and isolator which is
pretty straight forward to wire up.

Lets say the car fridge uses 2A/hr and the battery is 130AH is it safe to say
the battery should run the cat fridge for 50 hours?

The next question is could I use a solar system to charge the battery while its
been using by the fridge and what size solar panels/system would I need?

If the battery does not get used for a while is this ok?

Thanks for your help.

Hi Wolfau, A 130AH just might be okay because the duty cycle of a car fridge is not 100% (i.e. not always running) like lighting is for instance. It's important to understand what Depth of Discharge is and be careful not to discharge your battery more than 50%.

The following links may be of help....

http://www.batterystuff.com/kb/tools/calculator-sizing-a-battery-to-a-load.html
http://www.escapees.com/ClubNewsArchive/viewarchived.aspx?Club_News_Number=355

casper

 

[ProspectorPete]

I don't know much about the tech side of system set-ups but I used to run a 60 watt panel on the old troopy with duel batt and it would keep up during the day as long as it was in the sun for most of it but I'd need to start the troopy every second day for about an hour or so to top up the deep cycle, only running the 40ltr Waeco plus the music at night.
Now I run an 80 watt panel on the ute for the Engel (set @ 2 deg.) with no dramas at all, when the fridge kicks in the charge off the panel drops from 13.7 to around 12-12.5 volts.
In the morning the battery is between 11.9 - 12.2v and as soon as the sun hits the panel there's 13.7v going back in, simple as that.
I was told a few years back when researching an electric motor for my boat that when a battery gets to 10.5v or less it is considered flat and every 24 hours it's flat it loses 1 year on it's life, that's why I ended up buying a second panel so I can run the 60 watt in the boat if I'm using the electric motor, any charge back in is better than no charge.
A lot will depend on what sort of fridge you run, a compressor fridge like Engel, Waeco and some of the other 2 way's out there run quite efficiently but some small portable fridges or a 3 way run on 12v can suck the guts out quicker than a panel can put in.
A good fridge should have a 10.6v cut off to save your battery.

 

[Simmo]

Read Condors thread.... He explains heaps in there.......

(cant be bothered linking it!!!)

 

[Narrawa]

A good fridge should have a 10.6v cut off to save your battery

At this voltage the battery is passed being flat. When the battery hits this voltage, the fridge cuts out. The battery will surface charge fairly rapidly till the voltage stabilizes and the fridge will kick in again...this repeats till the battery cannot rise enough in voltage to kick the fridge back in...game over.
If your running a solar reg that allows you to alter the set voltages, you can avoid this happens by setting the LVD to a higher cut out voltage like 12-12.2v? You can also change the reconnect voltage where the fridge can kick back in after surface charge has reached a set point. However once the battery cannot reach this voltage, your battery will still be above 12v.
There are charts available on the net that will show you the DOD and SOC in relation to safe battery voltages.

I have the Engel 40L used 24/7 as a freezer when out bush for weeks at a time, and i have the Weaco 32L used in my van as a simple fridge. The Engel does not use a rotary compressor, and uses the same amount of Amps(2.5Amps) at start up as it does when running. The Weaco uses a variable speed rotatory pump which is NOT made by danfos in that model CDF35PAK, and the b@stard uses 7Amps at start up and falls back when in top gear to about 3-3.5Amps.

 

[Guest]

You guys are awesome.

Thanks heaps.

The next question is where is your 2nd battery located
In your vehicle.

 

[ProspectorPete]

The next question is where is your 2nd battery located
In your vehicle.

Side by side with the crank battery under the hood.
A mate of mine put a deep cycle in the boot of his Ford station wagon so he could run 12v to his caravan when camping, he had it professionally fitted and it would charge off the car when running, he had issues with flat battery and it was nothing but trouble.

So far the only issue I've had is when my brother didn't click the lid down properly on my old Waeco before bed and the 10.6v cut off didn't work waking to find I had 5v in my deep cycle. That fridge is no longer being used, replaced with an Engel with a much better lid latch.
The other issue I had in the old troopy was the fridge was running from a standard double cig socket at the back of the vehicle with standard wire to the fuse box, it would register a 1v drop from the battery to the socket so ran 10mm cable to a Merrick plug
which fixed the issue.

I've never had an issue running on an 80 watt solar panel in the bush with a fridge that's working properly, if it's overcast for a few days I simply give the car a run for bit.
This system suits my needs but I also use the vehicle to gather fire wood ever second day or so which is probably why I don't see any issues with my set-up.

 

[Narrawa]

My AUX batt is mounted right beside the fridge in the rear canopy of my truck.(big plastic tool box from bunnings with 12v plugs installed and 12v terminals for other uses.)..not your average canopy...home-brew tin pan. White in color and high roof. Sleep-able and we did for years before getting a van.
Charged from the alternator through an 8oAmp projector solenoid with idiot switch on the dash...meaning, you forget to turn it on, and no charge goes to the AUX batt when driving. However its an illuminated switch so forgetting about it is not a problem when its right in your face.
60W panel mounted on the front of the canopy, an 80-100W would have been a better choice, however it does the job keeping the 105Ahr Fullriver happy day in day out. I run anything from this battery thats required, detectors are charged from here when on the move. Lights, inverter, you name it, i plug it in here when the need arises. Connected to this battery is a projector 15Amp smart charger for when the generator is being used....permanently mounted. The caravan battery is the same battery and has its own projector 16Amp variable smart charger. 130W panel on the van roof. Both an old 1000W mounted inverter, and a 300W Pure sign wave portable.

I have a couple of floater solar panels for when and if the need arises to plug into either the van, or truck fridge via 50Amp Anderson plugs.
Seldom used simply because when out on long bush stays, we use a generator at night for charging of all things that need charging and the running of appliances like the bread maker, electric blankets, Vast satellite TV PCs ect ect.... Running the generator is far cheaper than the thousands of $$ for the extra weight of carrying bulk solar equipment where a geny is still employed and carried. Creature comforts don't have to be lost when you leave home. Your out there for weeks and months at a time, nothing like a few comforts. Prospecting takes it out of you when its day in day out.

One thing you learn from traveling with other people with their many varied set ups is this....no matter how much the van costs, or the computer controlled setups they have...they still use a generator most nights to top up.....Why is that you ask when they have so much solar gear?....simple...if you have the power to run all these things, you use it.

 

[ProspectorPete]

Sounds like a top set-up Narrawa, you've got everything covered with that lot and great to have the creature comforts with you while camping. I've been contemplating heading down the gen path soon so I can run a couple of lights in the camp when on long stays but the gas lantern will have to do for now. I think in the next 5 years the side-on camper plan will have to happen because my hips are starting to feel it in the swag on the ground, it's also getting harder to get up in the middle of the night off the ground when the full bladder is hurting, geez and I'm only 45, yep creature comforts are starting to look good instead of a quick simple set-up.

 

[Narrawa]

Lose the gas lantern and get yourself one of those big rechargeable LED work lights. The cost nothing to run and toss out far more light.

 

[ProspectorPete]

I've had my gas lantern for 28 years, it wouldn't feel right not tripping over things at night heading for the fridge.
I think you're right though, time to upgrade some gear.

 

[Narrawa]

I've had my gas lantern for 28 years, it wouldn't feel right not tripping over things at night heading for the fridge.

Im picking up what your putting down here....in that case, peg some dummy tent poles round the camp. :lol:

 

[Metamorphic]

My AUX batt is mounted right beside the fridge in the rear canopy of my truck.(big plastic tool box from bunnings with 12v plugs installed and 12v terminals for other uses.)..not your average canopy...home-brew tin pan. White in color and high roof. Sleep-able and we did for years before getting a van.
Charged from the alternator through an 8oAmp projector solenoid with idiot switch on the dash...meaning, you forget to turn it on, and no charge goes to the AUX batt when driving. However its an illuminated switch so forgetting about it is not a problem when its right in your face.
60W panel mounted on the front of the canopy, an 80-100W would have been a better choice, however it does the job keeping the 105Ahr Fullriver happy day in day out. I run anything from this battery thats required, detectors are charged from here when on the move. Lights, inverter, you name it, i plug it in here when the need arises. Connected to this battery is a projector 15Amp smart charger for when the generator is being used....permanently mounted. The caravan battery is the same battery and has its own projector 16Amp variable smart charger. 130W panel on the van roof. Both an old 1000W mounted inverter, and a 300W Pure sign wave portable.

I have a couple of floater solar panels for when and if the need arises to plug into either the van, or truck fridge via 50Amp Anderson plugs.
Seldom used simply because when out on long bush stays, we use a generator at night for charging of all things that need charging and the running of appliances like the bread maker, electric blankets, Vast satellite TV PCs ect ect.... Running the generator is far cheaper than the thousands of $$ for the extra weight of carrying bulk solar equipment where a geny is still employed and carried. Creature comforts don't have to be lost when you leave home. Your out there for weeks and months at a time, nothing like a few comforts. Prospecting takes it out of you when its day in day out.

One thing you learn from traveling with other people with their many varied set ups is this....no matter how much the van costs, or the computer controlled setups they have...they still use a generator most nights to top up.....Why is that you ask when they have so much solar gear?....simple...if you have the power to run all these things, you use it.

Way to go Narrawa.

Nice set up!

I got a couple of 80w panels in the portable fold out setup with controller and anderson connection which keeps the Thumper Extreme (120ah) humming in good weather during the day, but yes, also use a pure sine 2kva genny coupled with a 20amp charger as essential backup for charging at night.
I put it in one of those Redback housing boxes with ciggy plugs, merit and 2x andersons, voltage meter, usb etc
Attached my own 2000w inverter for the lappy etc

Usually stay away from the higher wattage appliances like hairdryers, microwaves etc, but I have the only 85' model van in the country with 5.1 surround sound and Sat set flat screen TV with X-box.

Its not much, but i love it...

Now electric blankets?

Your gettin soft mate.

 

[condor22]

Nothing wrong with electric blankets. My wife can't go detecting with me, so it's the hot water bottle or elec blanket and I can run that from a 150W inverter on high to start and then all night on low.

 

[Moneybox]

Wolfau, I've tried several of these electronic battery isolators over the years. Every time I end up going back to a simple 100A continuous relay/solenoid to connect the batteries. When the engine is off the start battery is isolated. As soon as you turn on the ignition all batteries are connected. It's simple and effective. I don't trust the fancy electronic devices.

 

[backcreek]

Wolfau, I've tried several of these electronic battery isolators over the years. Every time I end up going back to a simple 100A continuous relay/solenoid to connect the batteries. When the engine is off the start battery is isolated. As soon as you turn on the ignition all batteries are connected. It's simple and effective. I don't trust the fancy electronic devices.

I've been using an isolating relay on my batteries for over 10 years with no problems at all. When the relay is pulled in it is exactly the same as a truck running multiple batteries in parallel.

The main thing is to make sure both batteries are in good condition.