Electrical: Float Charging Battery

[wittsend]

They're Back! The Harbor Freight float chargers at $4.99 are back on sale again. Quite often posts come up regarding dead batteries. I've found these to SIGNIFICANTLY extend the battery life in cars I don't drive often. Just remember to not put them on a switched outlet - and disconnect them before driving away. With batteries now costing around $100 this $5 is cheap insurance.

[StudeRich]

The thing is I am not all that sure that a "cheapie" Harbor Freight "Float Charger" actually shuts OFF like the real Deal "Battery Tender" that costs significantly more, maybe for a reason.

It takes a real built in Voltage Regulator to do that, rather than just boiling the Electrolyte away for years at a very slow 1 or 2 Amp. rate, but never stopping.

I have 2 of their under $6.00 Units, but I definitely do not let them run more than a week or so, off and on through the Winter until I can get a better one.

[TWChamp]

I also bought 2 of the H/F units about 5 years ago, but I never used them. I have the same concern Rich mentioned. I use my regular 6 amp charger and connect it for a few minutes each month if I happen to be in the garage during the winter. I never leave a battery on the charger (any charger) unattended. I had a battery explode in my garage overnight about 20 years ago, and I couldn't find any part of it large enough to carry in for recycling. And this was when using a 1 or 2 amp charger. A few years later I had the hood open on my Dakota pickup and left a 5 amp charger on the radiator overnight. Luckily the truck was in the driveway and the fire from the charger never spread further than the charger, but it was a burned up mess in the morning.

If I had to charge a battery and not be in attendance, I'd put the battery and charger outside far from anything that can be damaged by a fire or explosion.

[jclary]

Somewhere, I saw something about a fire caused by (or blamed on) a cheap float charger. I have some, but use them sparingly. On a cheap one I have, when clipping to the battery (unplugged), I noticed a small spark. That indicates that the circuitry allows current to flow when the charger is not plugged into the wall. My thinking is that such a cheap device can drain the battery's charge if connected to the battery and charge power not supplied to the charger.

So, I spent more money and bought more expensive units from a motorcycle shop. The ones I have, not only provide the float charge, but automatically sense the battery's voltage (six or twelve volts) and charges accordingly. Supposedly, it does not charge at all unless the power reserve drops to a set point. I have used these on my mower, tractor, boat, & Studebakers. I still don't trust these either, and never intentionally leave them hooked up more than a day or two.

[JoeW]

I have a number of the HF units and leave them hooked up to my tractor, standby generator, forklift, collector cars, and three extra batteries I have laying around. I have never had any problem with them. With an output of 500ma I think it would have to be connected to a fairly small 12v battery to do any damage.

[Bud]

I wouldn't trust a 5 buck battery charger from Harbor Freight. There is a reason that a genuine Battery tender is about $50. It has a voltage regulator and will not overcharge the battery causing the electrolyte to boil off and destroying the battery. I have a Battery Tender and Solar Pro Logix battery charger which works like a Battery Tender, but I don't leave either one of them connected to a battery for more than a day at a time as I don't trust anything that has electronics in it not to have something fail internally and cause me a big problem. Bud

[JoeW]

I forgot to mention in my previous post that I don't use the HF float chargers on the AGM or Gel Cell batteries in my boats. There I rely on more sophisticated on-board chargers with 100% shut off. I don't use them on the one Optima AGM battery in one of my cars that is a restomod since originality doesn't matter in it and the battery doesn't lose charge over a long period of time anyway.

[wittsend]

Nor have I mentioned that I have used these "cheap" chargers for at least 5 years - continuously (as in I NEVER unplug them), on three cars, some of which are driven only 3-5 times a year. What I have experienced are batteries that have lasted up to 14 years and cars that crank over readily after months of sitting. They really aren't even "chargers." They are "maintainers" where the current is so low they merely put back that which naturally is depleted. The function is similar to those drip lines that keep a water trap filled. The drip rate is equal to the evaporation rate.

While a lot of the Harbor Freight stuff is crap I have found these "float chargers" to be one of their better products and have had the personal experience to support my position. I'm not the type of person to suggest a product with wishful thinking and no experience just because I want to believe the advertised hype.

[showbizkid]

Yep - I put one on my garage queen Pontiac because I was sick of dead batteries every 18 months. So far it's been 5 years with the HF float charger and it cranks up every time.

[Jeffry Cassel]

I've used them for years. Keeps battery up all winter. How can you overcharge a 600 or 700 amp/hr battery with 1/2 amp????

[BobPalma]

From today's Hagerty Insurance newsletter:

https://www.hagerty.com/articles-videos/Articles/2017/03/28/burned-out-bikes?utm_source=MagnetMail&utm_medium=email&utm_term=bobcaripalma@hotmail.com&utm_content=17-Hagerty%20Weekly%20News%2003-29&utm_campaign=Automatic%20tranny%20rebuild%2C%20valuation%20top%2025%2C%20worst%20road%20trip%20cars%20and%20making%20your%20classic%20dependable

[wittsend]

From today's Hagerty Insurance newsletter:

https://www.hagerty.com/articles-vid...c%20dependable

Hummm..., while the image is an illustration I do believe it is depicting those more expensive, "smart" battery tenders that caused the fire. Also of note was that the battery being charged was a much smaller motorcycle battery and the load percentage of the battery was much smaller than a typical car battery. It was somewhat confusing when the article suggestions stated, "If you don’t have a smart tender, unplug it if it will be left unattended for an extended period." Kind of defeats the purpose of a battery "tender." And then this, "Periodically check the tender and make sure it isn’t overly hot to the touch" How frequently would that be? Every 15 minutes, every hour? I'd think every day would not be frequent enough avert a potential fire. Again it kind of defeats the "tending" aspect of the charger.

Regardless this has given me pause to consider a fuse in the circuit. For the electronic knowledgeable the device is driven with a Class 2 transformer that upon my looking up says it has an inherent resistance to fire and not required to be fused. The primary transistors in the HF float charger are CW7805 and TIP41C. There is also a 9013 transistor 9 resistors and a diode and an LED.

[sasquatch]

Can't say anything about the HF charger since I've never had one but I do use Battery Tenders on all my equipment that doesn't get used very often. Never had a problem with any of them. They are on 24/7/365. Plus the battery in my motorcycle was still going strong after nine years. Without the Battery Tender I couldn't get more than two years out of the m/c batteries.

[Dick LeRoux]

I have 3 here in the warehouse; one for the forklift, one for the shop truck, & one for my '63 Avanti. All are "Battery Tenders" and never have any of them felt "hot" and they are plugged in 24/7