Battery Tenders

Back in the day the only people that had battery chargers were mechanics and dealerships.
Most people took lead acid batteries to the “filling station” and left them overnight for a slow charge which was supposed to make it like new. Charges were about $2 or sometimes free.
I just read an article that says slow charging causes “sulphation” in the battery and charges should be set on high or around 15amps.
Most Battery Tenders are around 1.5amps or less and most people say they have good luck and batteries last longer keeping them charged using a battery tender.
Anyone have any experience using battery tenders 6v or 12v?
Thanks,
Dell

I use a battery tender for my motorcycle batteries. They usually give up after a year or two without it. With it they last about 5 years.

I have used the battery tender on bigger batteries, but always charge them with a 10A charger first. I think it would be fine on it's own for maintaining the charge, but is too little to bring the charge up much.

Greg

Agreeing.....the 'tender' is a relatively precision regulated voltage output device, designed with the idea that holding the already fully charged battery at a specific voltage, corresponding to fully charged state, will prevent the battery from discharging internally. Ideally, not really charging the battery as much as preventing self-discharge by off-setting the internal discharge current, typically a very small number.
The best tenders are temperature compensated such that their output voltage tracks the "fully charged battery voltage" with temperature, as that voltage is different depending on battery temperature.
I, too had good luck on seldom used motorcycle. Yes, I know, just ride more often!

A battery tender is NOT a charger, it's only meant to "float" an already charged battery. A fully charged battery won't sulfate.

It is VERY important to consider carefully what you buy for this purpose. If it's a Chinese or Horrid Freight type deal, you might want to pass. Many of these are poorly protected in the event of circuit failures, and could well burn down your shop

I bought a battery maintainer from Northern, the one that sells regular price for about $50.00. Checked the voltage with it hooked to the battery. Right on 14 volts. Perfect. I suggest hooking up your maintainer or float charger and check the voltage. If more than 14.3, it will damage your battery with long term used. If below 14, it will not keep the battery properly charged. Lots of these units have no output voltage until hooked up to a battery.

I"m interested in a 6v battery tender or float charger.
I checked the archives and the most recent discusssion I could find on site was 2007.
Most were saying that for 6v, Battery Tender, Harbor Freight, and WalMart all have one for $6 to $20 that work and don"t ruin battery.
I guess the secret is to start with a fully charged battery before hooking up the tender. Although one poster said he had a dead battery and the tender brought it up overnight and has lasted 5 years.
Anyone have a favorite 6v tender?
Dell

The tenders & "automatic" chargers that I've repaired have circuit boards that aren't made in the USofA. Silicon controlled rectifiers which control the charging cycle are usually of marginal capacity & are pop-riveted to a heatsink that was made from a sardine can. There is usually less than $5 worth of components in the control board. The transformer is also of marginal capacity.
I usually put a 3-5 amp charger on my "off season" batteries every 3-4 weeks for an hour's charge. Works well for my situation.

I've been using them for years. And yes, they do a great job of extending battery life on any equipment that spends a lot of time sitting.

I've got a place in Michigan, 1000 miles from my home with a diesel Ford truck and four tractors. That's 10 batteries that would be sitting around suphating if I did't have tenders on them.

At home, I've gove four cars, two diesel trucks, four diesel crawlers, five diesel tractors, and three diesel backhoes. That's a lot of batteries. I use tenders on all the ones that don't get used much.

Note I've got some high-price Schumacher, Iota and Vector units and some very cheap Harbor Freight. All have worked flawlessly.

The Harbor Freight cost only $14 each and come with steel brackets for on-vehicle mounting. They are a bargain and anyone that claims they can burn your shop down is being a bit silly. They are UL listed and safely wired. The worst that can happen is, that a $14 unit might actually stop working. Not exactly a big loss. So far, the only one that's gone bad on me is the most expensive Schumacher.

I'll add they use very little power to keep plugged in. They are INDEED battery chargers, but only capable of 1.5 to 2 amps max. They first overvolt the battery to 14.8 volts. Then turn off, and only come back one when voltage drops below 13.5 volts.

Only problem you have to watch for is hooking to too many batteries. One little 1.5 amp charger can be hooked to a large pair of batteries - but no more then that. Otherwise, it will never shut off because it cannot get them above 14.8 volts.

I have had a Black & Decker from Wally World on a Farmall A 6V for 2 years and it works great.