Does anyone know the acceptable top and bottom voltage limits for a 12V automatic float type charger? I bought a Black and Decker 1 or 2 amp charger, and it seems to work fine: cuts in at about 12.3V and out at about 13.3V. Then I bought second charger, supposedly exactly the same, but it cuts out at about 14.6V. I'm concerned about overcharging.
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This kinda depends on your battery
As AGM's, Gels and Flooded types usually need different charge/float voltages. With that said, your low-amperage charger is designed to maintain the battery, not charge much so it's float voltage should be around 13.5. I've got AGM's and will bulk/absorption charge at 14.4 and float at 13.3. It does sound though that your second one is set too high since most batteries 100% charged and at rest run ~ 12.8VDC.
As AGM's, Gels and Flooded types usually need different charge/float voltages. With that said, your low-amperage charger is designed to maintain the battery, not charge much so it's float voltage should be around 13.5. I've got AGM's and will bulk/absorption charge at 14.4 and float at 13.3. It does sound though that your second one is set too high since most batteries 100% charged and at rest run ~ 12.8VDC.
Addendum . . .
Your 1st one may be too low as well. The voltage at which you said your 1st one 'kicks in' is too low. A battery at 12.3 volts is somewhere around 50% discharged. You might consider one of the smaller Guest or Pro Mariner chargers. They vary in capacity from ~6 Amps, are 3 stage and cost $70 or less.
Your 1st one may be too low as well. The voltage at which you said your 1st one 'kicks in' is too low. A battery at 12.3 volts is somewhere around 50% discharged. You might consider one of the smaller Guest or Pro Mariner chargers. They vary in capacity from ~6 Amps, are 3 stage and cost $70 or less.
Need to do some research
Try West Marine Advisor on battery charging, here: http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/smartbattery.htm And read the Ample Power Primer at www.amplepower.com
Try West Marine Advisor on battery charging, here: http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/smartbattery.htm And read the Ample Power Primer at www.amplepower.com
The one with the higher voltage cut-out...
isn't going to give you any problems - with a supply current of 2 amps max, it's never going to get anywhere near 14 volts on a full size battery. In simple terms, the amount of voltage you can rais a battery to is directly related to the amount of current you can supply. As long as you have a Group 27 or larger battery (something about the size of a standard car battery), you can pump 2 amps into it all day long and not do anything more than waste a little electricity. However, if your battery is smaller, you MIGHT overcharge it. Without knowing the details of your battery/electrical system, it's hard to give specific advice, but I second the idea of getting a dedicated, smart, marine charger... your batteries will last longer and you'll be much more confident that they will serve you when you really need it. Cheers, Bob s/v X SAIL R 8
isn't going to give you any problems - with a supply current of 2 amps max, it's never going to get anywhere near 14 volts on a full size battery. In simple terms, the amount of voltage you can rais a battery to is directly related to the amount of current you can supply. As long as you have a Group 27 or larger battery (something about the size of a standard car battery), you can pump 2 amps into it all day long and not do anything more than waste a little electricity. However, if your battery is smaller, you MIGHT overcharge it. Without knowing the details of your battery/electrical system, it's hard to give specific advice, but I second the idea of getting a dedicated, smart, marine charger... your batteries will last longer and you'll be much more confident that they will serve you when you really need it. Cheers, Bob s/v X SAIL R 8
BE VERY CAREFUL
I installed an automobile type 2-amp trickle charger on my boat. This unit somehow leaked current and generated a galvanic problem which destroyed my saildrive unit. About $1000 later and a little smarter, I know I'll never use any charger not specifically designed for boats. Good luck.
I installed an automobile type 2-amp trickle charger on my boat. This unit somehow leaked current and generated a galvanic problem which destroyed my saildrive unit. About $1000 later and a little smarter, I know I'll never use any charger not specifically designed for boats. Good luck.
Thanks
Thanks Jim, Stu, Bob, and Clark for the info. I have one of these $17 chargers hooked up to a small motorcycle battery to give me a permanent 12V for a $99 marine VHF in my house, in order to get weather info. Works great. Reception on those dedicated NOAA weather units is marginal at my location. The other unit I bought to keep the charge on my marine batteries over the winter -- which I am loath to force up to 14.5V. I will be careful though, if charging in the boat.
Thanks Jim, Stu, Bob, and Clark for the info. I have one of these $17 chargers hooked up to a small motorcycle battery to give me a permanent 12V for a $99 marine VHF in my house, in order to get weather info. Works great. Reception on those dedicated NOAA weather units is marginal at my location. The other unit I bought to keep the charge on my marine batteries over the winter -- which I am loath to force up to 14.5V. I will be careful though, if charging in the boat.
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