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Hey guys, in the HF float charger manual it says not to use with AGM batteries....

ANYBODY KNOW WHY ???????:?They don't explain why !!!!!!!!!!!
 

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Edit.. my deleted comments (if you read them) were for a "trickle charger", not a "float charger" so were deleted..
 

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This one I'd be guessing at... but typically "Float" type chargers designed for lead-acid batteries would be lower voltage output than a charger designed to float a AGM/VRLA or as a full charger...

A lead acid battery is essentially "fully charged" at 12.9 volts (and near dead at something like 11.5, IIRC). So a Foat charger that supports lead acid would charge to 12.9 max and call the battery "full" and then maintain the battery "topped-off" near that 12.9 volt area.

The AGM/VRLA batteries like to float-charge around 13.5 to 13.75 volts (which the lead acid float desin wouldn't do)

Now both batteries can support a rapid charge in the 15 volt range within some limitations. The lead-acid battery would really need to have some sort of monitoring (current, temperature, or battery voltage) to keep from boiling out... and the AGM/VRLA would ba a lot more tollerant, but should still be pulled off of a 15v charger before too long (heating may build pressure, the AGM would do better than the VRLA in this case).

So, my "guess" would be that the Harbor Freight float charger's output is somewhat less than 13-volts to support lead-acid. Charger output voltage below 13Volts for an AGM battery wouldn't provide a complete charge to the AGM battery.

Further (this is PURE supposition), the output design of the Harbor Freight float charger may not be protected against reverse current flow (common on some of the low-cost models) so having a AGM battery tht's topped-off at 13+ volts connect to a charger that's output is less than 13 volts could actually discharge the battery, which would use the float charger as the load in the circuit to dissipate the power being lost (and bad things maybe could happen, like an overheat of the charger's current limiting resistor on the charger's output)
 

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satan wrote:
This one I'd be guessing at... but typically "Float" type chargers designed for lead-acid batteries would be lower voltage output than a charger designed to float a AGM/VRLA ...
You're too humble.. More than a good guess...

Flooded: float voltage range 13.1 to 13.4 volts.

AGM: float voltage range 13.2 to 13.8 volts.

from HERE


Also, from the HF Float Charger Product Manualit states:

It maintains a battery charge ...by providing a 13.2 VDC maximum output.
 

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Not related to the question you asked, but FWIW -

I had two Harbor Freight units that I used on the bike and garden tractor. The first winter, all was good. The second season, the one on the bike quit working but the charge indicator remained lit giving the false impression that all was well even though the battery was completely dead. Same thing happened to the garden tractor the following year. Bottom line, if you use this brand you should check the battery voltage manually periodically to be sure it is working.
 

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I'm suffering senile confusion again. My 'float charger', from Sears states on the decal that it's output is 1.5 amps. It is not meant to charge a 'flat' battery. Those are not available now as Sears went to a different model and the one I bought quit immediately. I have now went to a Walmart marine maintainer for my gen and lawn tractor. Works the same with 1.5 amp output. The maintainer quits charging at a set voltage and only comes on as the sitting battery loses voltage.[A 2 amp charger will stay on and ovrcharge the battery.] I don't see why the charging voltage is important as long as the device quits above 13 volts and below 14.5. Am I wrong??
Bobbydsp
 

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Maintainers or something like that that will switch on and off would be quite different from a typical float charger

The cheap float design is just a current regulated voltage source. Something that's rated at 13.2V output with a max current of like 1.5 amp or whatever...

Hook 13.2 output to an AGM that's already at 13.5... and the float deal will just sit until the AGM drops below 13.2 or in a non-polarity, protected charger, the charger would be training the AGM down to the 13.2V output of the charger...

That scenario with a maintainer or "automatic" charger would have the charger sitting idle waiting for the battery to come below the set voltage. Then, after the battery dropped, the charger would 'switch' it's output on and allow the battery to come up to the rated voltage of the charger...

If you put a maintainer that shut-off at 13.5V on a flooded cell battery, the charger would stay in a near constant state of charge since the battery itself kinda flattens-out at about 12.9 volts (the charger would try to push a little more in there, some terribly low current, but still "on"...)... that same charger on an AGM would hit the 13.5 and shut off and wait for the lower hysteresis... then it'd be "on" again until the 13.5V "off" value was hit.

I'm not certain if "wrong" is a good word to use...(especially not on the InterWeb), but the charger design (float, automated, etc..) kinda needs to play nice with the battery being charged, since the different construction materials for the batteries offer slightly different "full voltage" values. In the automated stuff, with a hysteresis that turns it "off" at about 13.5, and on again at about 12.7 could be a pretty good 'catch-all' kinda box.

That said, the truth of most of the modern designed automatic chargers is that they monitor the output current to "top-off" the battery while providing a pulsating voltage that can run to 15V (intended to help reduce sulfating - and generally, will "level" nearer to about 13.5 more or less) By watching the output current the device can see when a battery isn't drawing anything, and allow the charger's output to drop out, until some percentage of that drop-out value is measured (or in some models until a timer expires when the charge cycle is attempted again) and when no current is drawn, no voltage output is offered. I'd suspect that your marine maintainer is a current monitoring device.



Maybe we can get the float charger, battery maintainer, quick charger, etc to reach the level of what oil/tires/air-filter to use ;) ? (you know, for all this discussion, around my place, if it works, I use it ... plain and simple...)



:gunhead:
 

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The "float charger" I purchased from Harbor Freight lasted one week then quit.
Purchased a "Battery Tender" . Last Battery Tender was five years old and went with the bike when I sold It.
 

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I must be lucky. I read about the AGM warning but thought anything would be better than nothing. My charger is 3 or 4 years old and my battery is at least that old also. I use it each year in Wisconsin winter and so far so good. It might not be optimal but I would rather have my battery at 13.4 or 13.5 during winter rather than less than that and certainly better than dead and freeze. I would say for those who can't afford the more expensive ones the Harbor is better than nothing and yes check it occasionally because the red LED lights when it is plugged in and when it is just hooked to the battery. Makes the LED kind of useless. Not sure what they were thinking with that. I bet someone who is on this board could come up with a LED to light only when above 13.4 volts or so. Then you would know if it was working. There's a challenge for the electronics guys. :?
 

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The main problem we have with these batteries is the electronics keep pulling power even after you turn off the ignition. You need something to replace that or you have a deadbattery within a couple of months.

I use the HF float charger on mine with no issues.
 

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I have the 2 Harbor Freight $10 maintainers...whatever you want to call it on 2 wings right now.
I am headed to the garage th chek the batteries right now....will post my findings.
 

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OK, checked the chargers and the batteries.
The chargers were at 13.7 and 13.9 and the batteries were at 13.6 and 13.8.
Don't know why each battery was .1 less than the charger...maybe the amp draw on the wing like clock.
I guess "It it ain't broke, don't fix it!"
 

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My neighbor had one of those Horrible Fright charger/maintainer’s on his newwhole house genset…two weeks later the battery was bone dry.



He “saved” what, $15 over buying a Battery Tender up front?…only to have to buy a another new battery and then a Battery Tender to replace the HF POS.


I buy some things from HF, but I don’t trust anything that is electric from them-especially stuff that stays plugged in all the time.
 
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