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Author Topic: Battery Charger?  (Read 8138 times)

KG4IVT

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Battery Charger?
« on: January 23, 2002, 05:11:40 PM »

I have a two 12v rechargeable batteries around my shack that I would like to be able to use in case of an emergency or other situation.  However, I do not have a charger nor do I know where to get one or what kind to get.  One battery is 25 ah and the other is 1 ah.  Is there a charger that I can use to charge both of these?  Thanks!!  
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KC5JK

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Battery Charger?
« Reply #1 on: January 23, 2002, 08:34:14 PM »

I have loads of small portable electronic devices, from radios and recorders to cameras and two-way gear.  Typically, no two will use the same combinations of batteries and total operating voltages.  This means you will also have as many wall adapters and/or recharge units.
Not all rechargeable batteries are the same type.  There are Nickel Cadmiums, Metal Hydroxides, Gell Cells and others.  Each is designed for a specific recharge rate, and most of them can be recharged at two rates, one for normal or quick charge, the other for trickle or "topping off."  These might be 10% and 1%, respectively, of the battery's current (mAh/Ah) rating.
If you have as much battery-operated gear as I do, consider a variable (or switchable) current and variable/switchable voltage power supply and charger, with quick connects for every type of equipment and battery connector you might encounter.
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ASTEFFES

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Battery Charger?
« Reply #2 on: January 24, 2002, 01:54:56 AM »

If both batteries are of the sealed lead acid type, go down to your nearest Kragen or other auto parts store and buy a 1 amp trickle charger.  Leave it connected to either of the batteries, assuming they are totally drained, for 1 hour for every amp-hour of capacity of the battery, give or take an extra hour.  That will get you by until you learn more about how batteries and power supplies work.  Then you can build or buy a better solution.  :)
  -Adam
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KE4SKY

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Battery Charger?
« Reply #3 on: January 24, 2002, 11:02:40 AM »

Peter,

Go to Walmart and in the automotive section look for a 1.5 amp "On-Board, Automatic Battery Maintainer."  They used to carry the Schumacher brand which you can find on www.batterychargers.com, but you are more likely to find their "house" Everstart brand, which is also OK and sells for about $20.

www.sportsmanguide.com has on close-out the Vector brand of a very similar unit for $14.97!  

These units have two LEDs, a red one and a green one. The green LED is on when the unit is charging.  The red LED alone being on on the Schmacher unit means that you have reversed polarity, it has a built-in protection circuit.  On smaller batteries such as your Yuasa NP2-12 when the battery approaches full charge the green light will stay on, and the red light will "blink," which is cpmpletely normal and OK.  It will blink slowly at first, then the red light will stay on longer between short blinks until full charged is reached and both lights stay on, indicating that charging is completed.  When the battery is fully charged both the green and red LEDs will stay on.  On small batteries I would then disconnect the unit.  I recommend connecting them to you equipment, checking voltage drop under full transmitter load and recharging monthly.

Considering the low cost these are great devices.  Every amateur should have one for their "Go Kit."  They compare the battery voltage against a programmed reset point on the PCB and begin charging when battery voltage drops below 12.6 volts.  The charger shuts off automatically either when it gets warm, as it will when working hard to charge a larger discharged battery, and starts up again when it has cooled off, and will continue until it reaches about 13.8V and shuts off.  The units have built in reverse polarity, over temperature and over-voltge protection and most are suitable either for gel cell or flooded batteries.

I have these connected to all of my vehicle batteries so that I can keep the battery warm in cold weather and to prevent discharge in recreational vehicles which are only used occasionally.  These units will safely recharge a gel cell as small as 2ah if you monitor time and temperature and ensure that the battery doesn't get more than slightly warm to the touch.  On a battery larger than 10ah, such as for a garden tractor, motorcycle, boat or RV you can leave the maintainer connected all the time and not worry.

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