floating battery charger

Our touring bike, an 88 Voyager XII has a radio/clock that draws power when the bike is parked. We frequently don't start the bike for over a week at a time as the only time it is ridden is two-up riding. When the weather is poor, the bike may not be used but a couple times a month. The battery will often discharge due to the drain of the radio/clock.

I bought a Harbor Freight "floating" charger that the package touts as being able to keep the battery freshly charged over periods of disuse. It is made for a motorcycle battery. I installed some leads off my battery yesterday and installed the charger as well. The charger seems to put out about 12.8 VDC (packaging says 13.25 VDC) all the time.

What is the difference between a floating charger and regular low amp charger? Are you supposed to leave the floating maintenance charger connected all the time when the bike isn't being used?

I have a "Battery Tender" brand name charger. It of course charges the battery and when the battery is fully charged it goes into "storage mode". Which means it puts in just enough to maintain the charge. Mine is designed to stay plugged in 24/7 until I'm ready for a ride. Just be sure to keep an eye on the water level.

I don't know what floating means, but I also have a battery tender and I've done some current checks with it. The way it works from what I've gathered is it simply puts out a preset voltage of approx 13v and the condition of the battery determines the amount of current which is limited to about 1.25A by design. So if you have a very dead battery, when first hooked up the charger will be supplying the entire 1.25A then as the battery charges the current gradually drops until the charger is putting out much less that 1.25A, like 0.5A if memory serves. At some time between 1.25A and 0.5A the charger by monitoring the current will change the light from red to green. The charger never shuts off and the red/green light itself has nothing at all to do with the charge voltage or current other than being an indicator of the approx charge being supplied. They kind of over tout the "goes into storage mode" thing as the charger is not switched on/off in any way, it simply puts a preset voltage into a load. None of this really matters or answers any questions other than just simply stating how the tender works. I'd have to think the Harbor Freight would do basically the same thing.

From what I've read on the Floating Chargers, once the battery being charged has reached a fully charged status it actually shuts off, and will only turn on again if/when the battery drops below a pre-determined level.
The Battery Tenders simply lessen the amount of charge being applied as the battery reaches a fully charged status, but never truely shut off.

I think I can see where a Floating Charger charger might be better than a Battery Tender.
Someone please (kindly) correct me if I'm wrong in this thought:
While being charged, the battery fluid level will drop slightly due to being heated/evaporation quicker than a battery that is only (truely) being charged when it drops to a certain state of discharge.
So during a long (winter) storage, the fluid level won't have to be monitored as closely, or perhaps not even at all after the initial level check before storage.

If that's the case, then I'll be getting a floating charger, instead of a Battery Tender soon.. It's one of the top things on my list of 'new toys' for the next season.

I had a lot of trouble starting my bike this fall, and I'm nearly 100% sure it's just a battery issue. It was so low, that the fuel/oil lights rarely came on when I turned the ignition on. :pinch:

As soon as I gave it some juice from a charger, it'd work like a charm..or if I'd been out riding a bit (and therefore charging the battery), it'd start like a dream.

Floating or Tender ... Floating or Tender ??

---> I think I understand the floating charger a little better now. From what I can gather around the 'net, the battery charger has a constant current while actively charging the battery, and once full changes over to a constant voltage, but low current, so that the battery won't lose charge - but will maintain around 13V of charge indefinitely. Because there's low current, there is no risk of boiling the battery, since barely any energy is actually making it into the battery. The elevated/constant voltage acts as a dam almost - and blocks the energy from leaving the "resevoir" (battery) while plugged in.

It makes sense to me, anyways.

Am I way off?

Post edited by: pyxen, at: 2007/02/14 15:23

wiredgeorge wrote:

....I bought a Harbor Freight "floating" charger that the package touts as being able to keep the battery freshly charged over periods of disuse. It is made for a motorcycle battery....What is the difference between a floating charger and regular low amp charger? Are you supposed to leave the floating maintenance charger connected all the time when the bike isn't being used?

Welcome to the site, wiredgeorge.
I axed DR. Google 'bout floating chargers, and it is not a particularly common term. The link myweb.hinet.net/home10/garauto/battery%20charger.htm did not have a lot of useful stuff on it.
I consider myself sort of a electrical technician, so I will try to find out more.

I'm keen to find out more as well.

FYI - WG's been around a bit..he's one of the resident carb gurus.

pyxen wrote:

I'm keen to find out more as well.

FYI - WG's been around a bit..he's one of the resident carb gurus.

Hi pyxen
And welcome to the site.:whistle:
And if I can find my dern calculator, I am going to check your formula in your profile section.
Let's see; I had that dang, thang last year, where is it....
I don't care if it does use reverse polish logic, it has to be good for something, even if it did only cost $800.

Post edited by: JimatMilkyWay, at: 2007/02/14 19:42

The float charger is on sale right now at Harbor Freight for $7.49 so you won't have to save your pennies for too long!

www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=42292

I cut the battery clips off and soldered a DC two pin male/female connector in place. On the side where the clips had been, I put some loops on the cable ends and tinned them and put them under the battery leads. I ran wires off them to the new connector so that it will poke out from under the right hand sidecover. I mounted the part of the charger that the cord comes off on a post near where the bike is parked so it would be convenient to plug it in. I will stuff the connector under the sidecover when not in use.



Post edited by: wiredgeorge, at: 2007/02/14 21:44

wiredgeorge wrote:

....I cut the battery clips off and soldered a DC two pin male/female connector in place....

Sounds like a good, clean install. Will be a good test case.
I would like to think that charger technology has advanced such that they do not eat the batteries lunch in the long haul.
I don't think lead acid batteries were ever plagued with "memory" discharge issues as, allegedly were some other types. Any of you battery gurus know if it is a good/bad idea to occasionally exercise the battery by taking it down to a low charge state, then charge as usual?

On sale for $7.49. That should mean it's a microprocessor controlled space age piece of equipment that does everything but washes your dishes for you
Probably more likely "floating" means it "floated" over here from China and is basically a 12VDC power supply that you'd be lucky if it even actually does anything.

RonKZ650 wrote:

...
Probably more likely "floating" means it "floated" over here from China and is basically a 12VDC power supply that you'd be lucky if it even actually does anything.

Heh, Harbor Freight definitley helps China's GNP.

It doesn't take a lot of sophistication to charge a battery. If you take an old "dumb" charger from the 1970's or so, and put a voltmeter on the leads, without a battery, I'd be surprised if the voltage was much over 12 volts. It works on pulses of voltage, so the average voltage is low, but the pulses are probably close to 16 volts or higher. A volt meter measures average-voltage, so it's not a good device to see what is really happening on an unconnected charger. When you connect it to the battery, the battery smoothes out the pulses and holds the voltage above 12v. A meter on the battery will then show between 13 and 15v. The battery holds 13v and the pulses from the charger add a volt or 2. All of this is easily seen on an oscilloscope.

If you want to see the effects of the charger, you should use an in-line amp meter. It will measure the average current into the battery, which is really what you want to know.

As Jim mentioned, amp meters can be blown up if hooked up wrong, so be careful!

As the average voltage of the battery climbs, the pulses don't drive as much current into the battery. But, because the transformer in the charger is an inductor, the current never drops to zero, so you eventually have to turn the charger off or you will over-charge the battery. "Smart" tenders shut off automatically, probably based on the battery voltage or on the reduction of charging current.

If you want to make a trickle charger out of a normal charger, you can just put a 2 ohm, 10 watt resistor in line. It will drop a 2 amp float charger to about .1 amp or so. Use 10 ohms if you really want a tiny trickle. To measure the average current, just put a voltmeter on the resistor, and divide the voltage by the resistance. Then you'll know what the average current really is.

(I recommend the high wattage resistor in case it goes into a higher current mode.)

Post edited by: loudhvx, at: 2007/02/15 23:34