Battery-based recharger

JHZR2

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Hello, Is there such a thing as a battery-based car battery charger? I've seen the 100CCA duracell units at BJ's for $50, which can be used as a jumpstarter... What Im looking for is something that will just trickle or charge (2A, 5A, whatever, obviously a cigarette lighter is current limited). Smart is better - only feed what is really necessary to the battery. Is there such a thing? Given that the duracell jumpstarter has a 12V DC lighter port, I would think that hooking a dual-male cable could allow the notionally higher voltage charger battery to charge the lower voltage starting battery. I would think that a diode would be necessary inline. Obviously a self-contained smart item would be preferable... Any thoughts? Thanks!
 
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Not really, just the battery voltage alone wont really charge it. You would need to bump the voltage to 14-15 volts to get past the internal resistance of the 'dead' battery.
 

JHZR2

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assuming it isnt dead though... Essentially, the application is a boat, which has a radio and a starting battery for the motor. Run the battery too long, may have an issue. Owners don't want to be handy/technical, just don't want a dead battery. Obviously you can buy AC-powered battery trickle chargers that can do 1-10+A to charge a battery... Essentially I'd like to give them something that just feeds a few A back into the system to let them play the radio for a few hours when out in the bay. They have a 100mA solar cell battery charger, but that is really good for nothing, IMO.
 
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Why not install a small battery, wired to power the radio, connected with a switch to the big starting battery? When they are stopped, the switch is opened and the radio is run off the small battery. After the engine is started, the switch is closed to charge the small battery off the engine's stator/alternator. You could even replace the switch with a relay to make it automatic, if there's a 12V switched source that's live when the engine is running.
 
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Oh, yeah, if it is charged you could just plug it in and run it parallel, for extra capacity. I like brians idea. The alternator could be tapped for this feed. But it is technical.
 

JHZR2

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I think this is too technical for them... therein lies the problem... I'd prefer something that they can plug into a wall socket, which they understand, to recharge, and fit into a 12V cigarette socket inorder to charge, since they understand those two interfaces... Anything else, while excellent and smart, isn't inline with what they can understand or will do. Thanks!
 

JHZR2

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BTW, there was a mini coleman item, Coleman PMB8110, which offered a 12V outlet, a 12V male plug to charge a battery, and could be run either way. Something along that line would be what I'm thinking of...
 

JHZR2

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Purely peace of mind. Small starter battery for a 50hp outboard, potentially running a small sony headunit (no external amps, 4 speakers) for 6-8 hours.
 
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Might upgrading to a larger 'deep cycle' battery be better? Running a starter battery down repeatedly is a quick way to kill it. The plates are not thick enough to take this abuse.
 
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You can buy a automatic disconnect to which you attach the battery terminal to this device, and this device to the battery. When the battery falls to the safe starting level it cuts off the battery until you manually reset it to start the boat.
 

JHZR2

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 Originally Posted By: Onmo'Eegusee
Might upgrading to a larger 'deep cycle' battery be better? Running a starter battery down repeatedly is a quick way to kill it. The plates are not thick enough to take this abuse.
Even if it is a deep cycle... run it too far down and the engine won't start...
 

JHZR2

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 Originally Posted By: StevieC
You can buy a automatic disconnect to which you attach the battery terminal to this device, and this device to the battery. When the battery falls to the safe starting level it cuts off the battery until you manually reset it to start the boat.
Neat! Will have to look for one of these...
 
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Just wire the radio to a cigarette lighter cord and tell them to plug it into the Coleman portable power pack when they want to listen to it.
 
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Just wire in a cut off switch and have them turn the power off when they leave the boat. The other option is a bit more and what I have. Adding an extra battery and having a selector with battery 1, battery 2, both battery 1&2 and off.
 
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