#141996 - 07/29/08 03:50 AM
Back up 12v battery system
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Addict
Registered: 06/10/08
Posts: 601
Loc: Southern Cal
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I seem to be on a roll so let me throw this out there.
As I've written in other posts, I work as a medic on film/tv sets mostly in and around SoCal. Some of these locations are rather remote with very little in the way of amenities other than what we bring to them. I tend to work very long hours, sometimes for up to a week at a time with little movement of my vehicle and sometimes with very limited access to refuel on any sort of a regular basis.
I've been toying with the idea of putting together an extra 12v battery system to power some 12v accessories, ie, cell phone, laptop, portable dvd player, AA/AAA battery charger, etc. What I'm envisioning is a small solar panel, portable to take into account the movement of the sun, possibly a charge controller and a smallish sized deep cycle AGM battery, eg, Optima or the new ones that are rebadged Optima's on sale at Sears. This could also be used conceivably to jump start a car.
I've thought about doing a dual battery setup with an isolater on the car system but I don't have a lot of room under the hood and I'm liking the idea of making the whole thing portable.
Anyone have an opinion on why this wouldn't work? Given that I'll have to know the limits of power available and the ability of the solar cell to recharge.
I welcome any suggestions or criticisms. Well maybe not the criticisms too much...;^)
John E
_________________________
JohnE
"and all the lousy little poets comin round tryin' to sound like Charlie Manson"
The Future/Leonard Cohen
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#141999 - 07/29/08 04:01 AM
Re: Back up 12v battery system
[Re: JohnE]
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Product Tester
Pooh-Bah
Registered: 11/14/04
Posts: 1928
Loc: Mountains of CA
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Portable will be pretty bulky / heavy... even one battery. If it were me I'd do two batteries and store one in the trunk if there is not room under the hood. They make other batteries that are 1/2 the size of the optima and you can fit two of them or more under the hood where you can fit them ![smile smile](/images/graemlins/default/smile.gif) The two battery idea doubles your storage capacity so for the money it's the best bet. Add a solar charger and you should set. -Todd
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#142000 - 07/29/08 04:09 AM
Re: Back up 12v battery system
[Re: Todd W]
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Addict
Registered: 06/10/08
Posts: 601
Loc: Southern Cal
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Thanks Todd, I should have been more concise, I wasn't thinking of making the battery itself portable, more that the system, mainly the solar panel, would be. Instead of being wired into the electrical system of the car. What I'm envisioning is putting the battery into some sort of container with a wiring hookup for the panel and then some sort of output system.
You bring up a good point about battery size. Maybe (2) smaller batteries would make more sense.
John E
Edited by JohnE (07/29/08 04:10 AM)
_________________________
JohnE
"and all the lousy little poets comin round tryin' to sound like Charlie Manson"
The Future/Leonard Cohen
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#142005 - 07/29/08 04:18 AM
Re: Back up 12v battery system
[Re: JohnE]
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Veteran
Registered: 07/08/07
Posts: 1268
Loc: Northeastern Ontario, Canada
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Hi John,
I will start this reply by saying that I am not very knowledgable when it comes to electricity, so consider this information as real basic.
I have an Eliminator Powerbox 600amp that I bought at Canadian Tire, it provides both 120 volt AC and 12 volt DC portable power, and has a built-in light, booster cables and air compressor. It can be recharged off, 120 volt household current, 12 volt vehicle plug-in and with a solar panel. I use it regularly to boost vehicles, power lights/tools and inflate tires, it is very handy.
Here is a link, I an sure retailers in the USA sell something similar, http://www.canadiantire.ca/browse/product_detail.jsp?PRODUCT%3C%3Eprd_id=845524443271701&FOLDER%3C%3Efolder_id=1408474396672502&bmUID=1217307644862
This link may not work, Google Canadian Tire Eliminator Power Box and you will find a selection of them.
There are also larger and smaller models available.
Mike
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#142017 - 07/29/08 11:42 AM
Re: Back up 12v battery system
[Re: KG2V]
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Rapscallion
Carpal Tunnel
Registered: 02/06/04
Posts: 4020
Loc: Anchorage AK
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You can monkey around with the circuits if you want, and eventually you will figure out all the design considerations, or you can go to a marine/rv center and see what they have, talk with their techs, and get exactly what you need. They may even build it for you.
Deep cycle batteries are not recommended for jumpstarting other vehicles, nor for starting your own vehicle. If you are going to use the car's existing chargins system to charge the secondary battery (highly recommended), then use a good quality automotive battery. Deep cycle batteries do not like a constant charge current either, so an auto battery is preferable for a solar panel charging system as well, unless you want to spend a lot of bucks for a regulating system.
If I were building a backup battery system for a vehicle, I would most likely wire the batteries in parallel using 12 or 10 gauge welding wire (properly fused), and have a cut-out switch so that I could go from one battery to the other but not both at the same time. This way I won't overload the alternator trying to charge two batteries at once, thus frying the alternator. I might build a little timer signalling device to remind me when one battery has charged and I can switch to charging the other. Then when I need to use battery power, I can go from one battery to the other as well. As far as the solar panel goes, just wire it with an accessory plug (cigarette lighter) and plug it into the jack on the dash to charge whichever battery needs it. The panel will never put out enough juice to have to worry about overloading the current. Even a big panel will only make about 15 to 20 watts peak.
I spent a good chunk of my life building and maintaining battery powered circuits, and the cheap way is to use car batteries and make as few changes to the existing circuitry as possible. Where I've had to use deep cycle systems, the cost has been significantly more.
_________________________
The ultimate result of shielding men from the effects of folly is to fill the world with fools. -- Herbert Spencer, English Philosopher (1820-1903)
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#142021 - 07/29/08 12:58 PM
Re: Back up 12v battery system
[Re: benjammin]
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Old Hand
Registered: 02/08/08
Posts: 924
Loc: Toledo Ohio
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Harbor Tools has a 45 Watt solar Panel and charge controller, they sell it for $249.00 on sale right now for $189.00. It may fit what you need.
_________________________
You can run, but you'll only die tired.
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#142025 - 07/29/08 01:12 PM
Re: Back up 12v battery system
[Re: benjammin]
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Old Hand
Registered: 02/08/08
Posts: 924
Loc: Toledo Ohio
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You can monkey around with the circuits if you want, and eventually you will figure out all the design considerations, or you can go to a marine/rv center and see what they have, talk with their techs, and get exactly what you need. They may even build it for you.
Deep cycle batteries are not recommended for jumpstarting other vehicles, nor for starting your own vehicle. If you are going to use the car's existing chargins system to charge the secondary battery (highly recommended), then use a good quality automotive battery. Deep cycle batteries do not like a constant charge current either, so an auto battery is preferable for a solar panel charging system as well, unless you want to spend a lot of bucks for a regulating system.
If I were building a backup battery system for a vehicle, I would most likely wire the batteries in parallel using 12 or 10 gauge welding wire (properly fused), and have a cut-out switch so that I could go from one battery to the other but not both at the same time. This way I won't overload the alternator trying to charge two batteries at once, thus frying the alternator. I might build a little timer signalling device to remind me when one battery has charged and I can switch to charging the other. Then when I need to use battery power, I can go from one battery to the other as well. As far as the solar panel goes, just wire it with an accessory plug (cigarette lighter) and plug it into the jack on the dash to charge whichever battery needs it. The panel will never put out enough juice to have to worry about overloading the current. Even a big panel will only make about 15 to 20 watts peak.
I spent a good chunk of my life building and maintaining battery powered circuits, and the cheap way is to use car batteries and make as few changes to the existing circuitry as possible. Where I've had to use deep cycle systems, the cost has been significantly more. You are right that gel-cell batteries don’t like a high amperage charge, they are not the best choice to have if you are going to use the alternator to charge them. In an alternator tied system I would use 2 6-volt golf batteries tied in together. Yea the golf batteries are heavy, but they have a lot of reserve power, can handle a good amount of charge current and also handle a lower discharge that a starting battery can’t take. Car starting batteries don’t like to be deep cycled and in fact will be destroyed if you discharge them a lot like what happens with house batteries in a camper (and this is what is going to happen when you use the house battery to run computers, DVD players, chargers, inverters and the like) they are a very poor choice for house batteries in a camper. AGM batteries will work well with the charge rate from a solar panel. Starting batteries (a normal car battery) have thin plates and are made to deliver a lot of amps for a very short time, they are not made to have a constant drain on them like golf, gel-cells, AGM or deep cycle batteries are.
Edited by BobS (07/29/08 01:37 PM)
_________________________
You can run, but you'll only die tired.
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#142116 - 07/29/08 09:57 PM
Re: Back up 12v battery system
[Re: JohnE]
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Enthusiast
Registered: 08/23/05
Posts: 289
Loc: WI, MA, and NYC
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The main question which determines just about everything else hasn't been asked yet. Namely, how many amp-hours do you want this battery to have? I have a PowerPort 73A, which is an SLA 12V, 8AH battery that weighs 6lbs. It comes in a carrying case with three built in DC outlets and a charger. It's excellent for ham radio use and a wide variety of other applications.
Edited by Fitzoid (07/29/08 11:12 PM) Edit Reason: corrected model number
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----- "When I read about the evils of drinking, I gave up reading." Henny Youngman
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#142117 - 07/29/08 10:10 PM
Re: Back up 12v battery system
[Re: Fitzoid]
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Addict
Registered: 06/10/08
Posts: 601
Loc: Southern Cal
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Thanks Fitzoid, I'm intrigued by the Powerport stuff. Wonder how hard it would be to recharge one of their battery systems with a solar cell?
I'll look into their system.
John E
_________________________
JohnE
"and all the lousy little poets comin round tryin' to sound like Charlie Manson"
The Future/Leonard Cohen
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