Batter Float Charger

Anyone got a good handle on the voltage/current curve for a battery float charger? This one is cheap enough, just not sure I trust a HF unit
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?ItemnumberB292
My Jeep in storage has a parasitic draw, I went to warm it up yesterday, battery was well down.
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How about a battery disconnect?
I use the Black & Decker 2/4/6 chargers.
http://www.blackanddecker.com/ProductGuide/Product-Details.aspx?ProductID 575
They seem to do a pretty good job, and they are very affordable.
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RoyJ wrote:

I have had one for years, and it seems to work. For the more critical batteries I usually use a Schumacher or a Solar brand.
If the Jeep is stored outdoors, I'd suggest a solar-powered charger you can leave on the dash. As of a few years ago, all VW cars shipped with one to ensure a new car had a hot battery. The parts dept used to sell them cheap.
Best to find one with charge-controller circuitry if possible, but I've used the $10 HF versions with success
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The Jeep gets to hibernate in a dark but very cold corner from about November 1 to April 1st. I try to get it started for a 30 minute warmup sometime in mid winter. The drain is either from the radio or the computer, I could pop the battery cable. A 'put it on and leave it on' would be good approach for something stored at 0F.
RB wrote:

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I've had 2 of them for years. I have 10 vehicle batteries in tractors, garden tractors, ATVs, etc. to maintain, so I have a log of the winter activity for same. These float chargers float a good battery at about 13.04 to about 13.07 volts. I don't worry about leaving them on for a week or two at a time. I doubt that they can put out much over an amp, but that's not what they are for. When a battery won't float to above about 12.8, I consider replacing it soon.
Pete Stanaitis -------------------
RoyJ wrote:

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http://www.batteryfaq.org / Download the state of charge tables.
Jim Wilkins
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Read the owner's manual! Tells the fuse to remove for long term storage.
Paul
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" snipped-for-privacy@coinet.com" wrote: Read the owner's manual! Tells the fuse to remove for long term storage. ^^^^^^^^^^^^^^^^^^^ Most cars have two connections to the positive battery terminal. One goes to the starter relay, and the other feeds everything else, and it probably has a hefty fuse. That would be the one to disconnect. Or you could install a battery clamp that tightens by a cam-lever, so you can pull the cable and reinstall it without tools. This has the added advantage that in an emergency you can kill the power quickly.
Even with nothing connected to the battery, there is a slow self drain, so a trickle charger ain't a bad idea. Or do what Winston suggests, and put a 20A charger on a timer. I've never heard that idea before, but it sounds very logical.
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RoyJ wrote:

You could rig up an irrigation timer to power a 20A battery charger via a relay. That way, every week you'll provide enough current to circulate the acid somewhat to limit sulfation. That's what I'd do anyway.
--Winston
--

I'm still waiting for another sublime, transcendent flash of adequacy.

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They work good. Jus don't short the output. Blows 'em up. JR Dweller in the cellar
RoyJ wrote:

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I'm not overfond of horrible fright, but one trick for any dumb charger is to put it on a lamp timer, and set the lamp timer to turn the charger on for only 1-4 hours per day, rather than leave it cooking 24/7.
Check the acid level occasionally and top off with distilled water.
--
Cats, coffee, chocolate...vices to live by

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I've got half a dozen of those HF units. Keep one on each of my seldom used batteries. Generator, lawn mower, tractor etc. They seem to work fine to keep a fully charged battery up. I don't know how they'd be in your situation with a small but steady leak. Paul

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wrote:

The final word is always the battery manufacturer's data sheet. As a general rule, long-time float charge should be at 13.8V, while dynamically used batteries should be charged to 14.4V. These numbers are valid for room temperatures, though. Lower temperatures require slightly higher voltages.

Float charging a lead-acid battery is technically a very simple task. A cheap charger should work just fine. A more expensive one might be able to measure temperature and adjust charge voltage accordingly.
The particular one you link to, specifies 13.2V output. That might be a little on the low side, especially with a cold battery.

A float charger is a good idea for this application. Lead-acid batteries decay faster the less charge they have, so keeping them fully charged is the best way to store them.
Taking the battery indoors is not a good idea. Low temperatures slow down the chemical reactions that destroy the battery.
--
RoRo

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wrote:

The correct answer is that the charger is supposed to be temperature compensated to match the charging thermal curve of a lead-acid battery. At 'room temperature' (let's say 68-F) you float to 13.8V. When the battery and outside is at 110-F you need closer to 14.4V. But if it's 45-F at the battery, 13.2V would be plenty.
You don't need to worry about the details, just that it is known. The important part is the designer has that thermal curve programmed right in the controller chip. And you mount the charger near the battery so it senses the environmental conditions around the battery - you don't put the charger in a heated enclosure with the battery outside.

But having a battery freeze is an instant Fail, and then the acid that gets all over is really hard on the car body, and you if you get it on you.
If you are in the Snow Belt pull the battery and store it inside, cold is OK but protect it from a hard freeze.
A partially discharged battery freezes very easily, IIRC around +25F - plus it sulfates sitting there discharged, and won't take a charge when you try it in the spring.
. And even a fully charged battery has it's limits before freezing, IIRC around -40 F - that's why people in climates where they/have/ to plug in their cars overnight (or it flat out isn't going to start in the morning) usually buy a wrap-around battery heater in addition to a block heater. If the battery is sitting in a car (even disconnected) it's slowly self discharging, and the freezing point could easily pass the outside temperature...
--<< Bruce >>--
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