Float Chargers

Float chargers are attached to the 12v in the generator, and also to two 12v that provide back-up for the sump-pump. Neither of these units is used every day; in fact, the sump-pump batteries have never been used in seven yrs. So, presumably, the chargers main function in these applications is to keep the 12v from discharging due to lack of use.
But beyond that, do chargers, theoretically, keep batteries ready and able to run indefinitely? Or will the cells eventually die of old age despite the chargers, much like a well-preserved, fit old person: Bob Hope, Geo. Burns, Jack LaLanne?
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Andy comments:
Float chargers, such as the one from Harbor Freight, do a pretty good job of maintaining the charge, but that doesn't mean that it can keep things going for long periods of time without checking. Much like planting flowers --- they need to be weeded... When working with chemical reactions over a wide temperature range, there is no such thing as "hook it up and forget it "....
Every month, check the water level in each cell. Top them up with distilled water if is low. Depending on the temperature variations, the float charger can't compensate for every single variable, and occasionally will feed in a little bit too much and boil off a little water..... I'm not aware of ANY device which will compensate exactly for the changes that occur with the electrolyte which require minor changes in the float voltage.....
I've used the Harbor Freight float charger for years, and easily double the battery life in my lawn tractor.... but it won't give the battery immortality, and you have to check up on it......
Remember, it is a FLOAT charger, not a BATTERY CHARGER.... A real charger, with a hydrometer, should be used to charge the battery... Then the float charger is attached to compensate for internal leakage..... A FLOAT CHARGER will not "charge up" the battery by itself.... That is a mistake that many people make. If you use the Harbor Freight float charger, read the manual.....
Andy in Eureka, Texas , P.E.
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On Mon, 12 Sep 2011 18:13:30 -0700 (PDT), Andy

charger. A float charger is NOT an intelligent device. A "battery maintainer" is.
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On Sep 12, 9:39 pm, snipped-for-privacy@snyder.on.ca wrote:

OP, you need an accurate voltmeter. If the charger pushes and keeps a 12 Volt battery voltage above about 13.6 v then it is "overcharging" it and reducing it's life.
Too high or too low a voltage will both shorten the shelf life of a lead acid battery.
13.5 to 13.6 is about optimum for room temperature.
A good battery charger will regulate the voltage to that range.
Mark
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On 9/12/2011 9:16 PM, Mark wrote:

What about the vehicle itself then? They charge (if working properly) at 14.2v
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Steve Barker
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On Mon, 12 Sep 2011 21:32:59 -0500, Steve Barker

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Andy comments: I can't disagree , in principle. However, this month the temperature in my garage ranged from 70F in the morning to 110F at 7pm.... Battery chargers or maintainers simply don't compensate over that range..... and the battery chemistry over temp and the component tolerances in the "charger" both vary , and don't necessarily track over a wide temp range....
Under the hood of an automobile, the range is greater , probably from around 0F in the winter to 160F or higher in the summer.. The voltage "regulator" in the alternator has temp compensation, but not for that great a range.... I keep an accurate digital voltmeter plugged into my cigarette ligher outlet and see the "charging" voltage range from 13.5 to about 14.5 volts as the battery chemistry terminal voltage argues with the alternator regulator temp compensation from summertime to wintertime.... That's why car batteries only last a few years....
By the way, my voltmeter has headed off being stranded by a dead battery several times as it lets me know when an alternator diode has gone out, long before the charging stops altogether. Plenty of time to fix the problem before the alternator has failed and possibly the battery has sulfated.....Just a suggestion.
Andy in Eureka, Texas , P.E.
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He has a float charger, which is exactly what he needs, not a battery charger. With a battery charger, he'd need to monitor the charging himself, which isn't going to work for a battery that needs to be kept charged all the time.
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On Tue, 13 Sep 2011 17:11:28 -0700 (PDT), " snipped-for-privacy@optonline.net"

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On Sep 12, 9:39 pm, snipped-for-privacy@snyder.on.ca wrote:

Says who? In my world, the terms are interchangable. Now a trickly charger, that will continue to deliver a slow charge no matter if the battery is fully charged or not. A float charger or "battery maintainer" will not.
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On Tue, 13 Sep 2011 17:10:21 -0700 (PDT), " snipped-for-privacy@optonline.net"

A "battery maintainer" may be a trickle charger - but a trickle charger is not necessarily a "battery maintainer"
MOST "trickle chargers" are nothing more than a small center-tapped transformer with a half wave rectifier that will put out up to 16 volts (at 125 volts, input, for instance - less at lower line voltages) and is resistance limited to 2 amps output. Some of the better ones have a regulated output - and will put out a maximum of something like 14.6 volts (might be a little less) regardless of input voltage swings.
An intelligent battery maintainer usually runs in a pulsed mode - checking the voltage of the battery between pulses, and adjusting the voltage and duty cycle to keep the battery at full charge without the possibility of over-charging. There are other types of "intelligence" as well - some better than others.
The "battery tender" is one example of a smart battery maintainer.
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On Sep 13, 10:58 pm, snipped-for-privacy@snyder.on.ca wrote:

I never said a trickle charger is a battery maintainer. I said the terms float charger and battery maintainer are one and the same. A float charger senses when a battery reaches full charge, then backs off and allows the voltage to lower. It will start charging again when it senses that the battery voltage has dropped below a certain point.
Here's an example:
Black & Decker Bm2b Smart Battery Charger 2 Amp Automatic Float Mode $17 online
1 review The Black & Decker Smart 12-Volt Float Mode Maintainer Battery Charger is a hand-held engine starter that can be run on either alternating or direct current. It has reverse polarity protection.

It's also an example of what the rest of the world calls a float charger, just like the Black and Decker.
Here, from Wikipedia:
"Float charger A float charger differs from a trickle charger in having circuitry to prevent overcharging. It senses when the battery voltage is at the appropriate float level and temporarily ceases charging; it maintains the charge current at zero or a very minimal level until it senses that the battery output voltage has fallen, and then resumes charging. "
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I beg to differ. I think if you look at the output of the float chargers they do have sufficient capacity to charge the battery. In fact, it would be impossible for them not to. If they only could deliver exactly the amount of self-discharge that occurs, they would have to be perfectly matched to the battery. In reality, they have extra capacity so they will make up for the slow self-discharge and have current beyond that to slowly recharge the battery. It will however take a long time compared to a regular battery charger.
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On Tue, 13 Sep 2011 17:08:07 -0700 (PDT), " snipped-for-privacy@optonline.net"

mili-amp
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I harbored my datsun last winter. It started ok. That's all I know about that. I know from floating NASA equipment, you have to be well under 100 ma to keep bubbling down. 10 ma is good, if it enough to keep it above a certain minimum voltage. Batteries are best overcharged occasionally to above 14 volts, to extend life. They might also need balanced, by discharging.
Greg
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wrote:

battery just enough to mix the acid to prevent stratification. This generally also achieves the "balancing"
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