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  #1 (permalink)  
Old 03-22-2013, 3:39 PM
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Default Which 12 VDC Heavy Duty Battery To Buy?

I plan on purchasing a Kenwood TM-281 2 meter mobile rig. I would like to use this rig at home with a heavy duty battery. I was told to get a deep cycle marine battery. I just don't know what size battery in amps to get? Kenwood advises to use a power supply at 13.8 vdc at 14 amps if one is going to use the rig at the maximum output of 65 watts. I'm only going to use 25 watts at maximum. Any suggestions on the type or make of battery to purchase? Should i purchase a battery with maximum amps?
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Old 03-22-2013, 3:48 PM
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I dont have the specs with me, but I would use a GEL battery and not a deep cycle. You will of course need a charger to keep the battery maintained. I use surplus TELCO gel batteries.
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Old 03-22-2013, 3:55 PM
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Default Which 12 VDC Heavy Duty Battery To Buy?

What about using an AC to DC power converter?


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Old 03-22-2013, 4:36 PM
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Quote:
Originally Posted by KK4IFN View Post
What about using an AC to DC power converter?


Andrew L.
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I don't want to use AC! I want to use power directly from a battery!
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Old 03-22-2013, 4:38 PM
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Default Which 12 VDC Heavy Duty Battery To Buy?

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Originally Posted by N3ISME View Post
I don't want to use AC! I want to use power directly from a battery!
Well there is really no need to go get hateful.


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Old 03-22-2013, 6:18 PM
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You need 12 volts. The size of the battery (amp/hour rating) will determine how long you can run off just the battery.

I agree, gel-cell would be the ideal choice. Marine deep cycle would work, but I'd much rather use a gel-cell inside a house.

Depending on how long you want the radio to run off of the battery, and how much transmitting you will be doing, will dictate what size battery you need.

As KB2ZTX said, used Telecom batteries are idea. I'm a telecommunications engineer by trade, and work with radios and a very large PBX system. Our PBX is distributed over a wide geographical area, with some sites bigger than others. Our big sites have 1000AH and up battery plants, while some of the smaller ones might be 100AH. We usually retire our batteries before they fail, so they always have a few years of life left on them. We often donate them to local hams. Good places to check for used batteries would be any telecom installer that does small to mid sized systems. Since these systems usually run off 48 volts DC, it's pretty common to have a string of four 12 volt gel-cells providing battery backup. They should be replacing them -before- they fail. Another option is the batteries out of most home/office UPS systems. They usually use 12 volt gel cells.

A new battery is going to cost you some money. We use a lot of C&D Technologies model Tel 12-105's. These are 12 volt 100aH batteries that are designed to sit 4 across in a 23 inch equipment rack. They would be ideal for this application. Figure on paying somewhere between $230 to $250 each, new. Or, if you were local, I'd give you some for free.

While a gel-cell shouldn't outgas if charged correctly and not mistreated, they can vent hydrogen gas in certain instances. Do not put them in a sealed container. Make sure you vent them somewhere safe (outside). They can be installed indoors, without venting, but make sure you don't charge them with too much current or run a charger at more than 13.6 to 13.7 volts. Obviously, fuse everything.
As for chargers, you can full time charge them if you do it correctly. It referred to "float" charging in the telecom industry. You feed them with 13.5 to 13.6volt (or whatever the manufacturer recommends) and keep the current low. This will not overcharge the battery, and as long as the battery temperature stays stable (70's or so) you'll be OK. To do it right, you should have a charger that will do temperature compensation.

Sorry, probably way more info that you wanted....
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Old 03-22-2013, 7:03 PM
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Your radio is meant to run on 13.8 volts. The best you can hope a brand new fully charged battery will supply with no load is 12.8 volts. That means when you transmit the voltage will go lower. I have seen some radios get stuck in transmit when they don't get the 13.8 volts they need. To receive only, a battery will be fine, but if you intend to transmit, a battery just won't do.
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Old 03-22-2013, 7:20 PM
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This may be true on some, but a mobile radio that works in a car with the engine turned off is getting 12.8 volts. Most radios have a 10% to 15% leeway on supply voltage. Power output does drop.

Most repeaters out there will have a 12 volt battery backing them up, and the also do fine. The trick is to get a big enough battery (or batteries) that will support the current draw on transmit without the voltage dropping too much.
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Old 03-22-2013, 7:25 PM
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Agreed, but to get a battery [batteries] that big could buy 5 12 volt power supplies.
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Old 03-22-2013, 7:36 PM
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Quote:
Originally Posted by N3ISME View Post
I plan on purchasing a Kenwood TM-281 2 meter mobile rig. I would like to use this rig at home with a heavy duty battery. I was told to get a deep cycle marine battery. I just don't know what size battery in amps to get? Kenwood advises to use a power supply at 13.8 vdc at 14 amps if one is going to use the rig at the maximum output of 65 watts. I'm only going to use 25 watts at maximum. Any suggestions on the type or make of battery to purchase? Should i purchase a battery with maximum amps?
I would go with an Optima AGM Battery - probably a yellow top or 2 in parallel depending on how much
capacity you require, and for charging there is no better than an IOTA Engineering DLS line with the IQ4
smart charging option.

OPTIMAŽ AGM Batteries :: OPTIMAŽ Batteries

IOTA Engineering DLS-45 12VDC Battery Charger and Power Converter - 45 Amps

IQ Smart Charger for DLS Series Battery Chargers from IOTA Engineering

Yes, will be pricey but its the best combo, all during storm Sandy and Athena my
repeater stayed on the air and after about 12 days was still running. As soon as
power was restored the bulk power charge started immediately and both batteries
were back to full power in about 8 hours of charging.
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