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dc/dc (car/battery) switch

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w1ley

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I have put together a small embedded Linux box to use in my truck. The last detail is power. I would LIKE to run off of a rechargeable batttery when there is no power (ie the truck is off or the unit is out of the truck),when there IS dc power then run off of the external power AND charge the batteries. To date the entire project has been "off the shelf" I have only assembeled and configured. So if possible I would like to continue this philosophy and use an off the shelf unit.
 
forgive the " off the shelf " reply :lol:
1> Geographic location ... it helps source suppliers
2> Truck supply specification 12 0r 24volts
3> project linux box power supply requirements volts and amps
4> how long has the stanby battery expected to run without power from the truck
 
Not only will I pardon your "off the shelf reply". I will thank you for making it so quick! :D

1) Boston area

2) 12 volt truck

3) Linux box requires 2 amps @ 12 volts

4) standby powe needs to be ~6 hours.
 
Following in th off the shelf theme of this thread..
Sure Power Industries makes a multi battery isolator..
what this does is lets you charge two batteries when the motor is running, and lets you discharge them seperatly..
i have model 9523A..
 
Sebi said:
For the expected runtime need min.15Ah battery! (about 8..10kg)
Yup, its true.

This is where we start, we define requirements and adjust as dictated by pesky reality. I dont have a weight requirement per se (I would like it to be "hand carryable" whatever that means. :D ) but I do I have a real runtime requirement. My hardware minus the battery weighs <5lbs. Is 6 hours of runtime worth 4 times the weight? *I* think so, but certainly my goal will be to minimize that weight as much as possible.

Willi, thanks for the "sure power" tip, I will check them out now.
 
This is an 18 Ahr battery origionally intended to jump start a vehicle..
it can be carried easily ...
try Pep Boys i think i paid less for their mity Mite which is 12 Ahr ..
also i believe ( dont see why not ) that this can be charged like any other battery, and it can also be charged by house current ( it has a built in charger) also it has a cigarette lighter/ adapter ..
Manufacturer: SCHUMACHER
Part # SCH-PS-400-3A
**broken link removed**
 
You would not use an isolator if I read the description correctly. Just hook the battery up to a charger. You then have 12v to run the stuff and anything leftover goes into the battery. The only catch is that some charging schemes like the dv/dt slope detect used for NiCd could be confused when it is not clear how much current is going into the battery due to the appliance consumption. Li-ion would have trouble. Lead acid (any type) would probably be fine since that's a constant voltage charge.
 
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