# battery maintainer



## SPS-1 (Oct 21, 2008)

I have used a battery maintainer to charge up a dead battery - many times actually. 
I would leave the battery tender on for a day, and then the car had enough juice to start up.
It's a Sears maintainer that I have , not Harbor Freight.
I used to have it hooked up full time to a car that I drove very little. However, that car's battery did swell up and crack the plastic case, which I understand is a sign of overcharging.


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## AllanJ (Nov 24, 2007)

Battery maintainers come in a variety of (electrical) sizes, I have seen some rated at three quarters of one ampere.

Also some are not "compatible" with some batteries (can't predict which combinations), where a battery could get overcharged. You can still use those maintainers but you would need to manually disconnect them before overcharging occures.


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## SARG (Dec 28, 2020)

I've accumulated at least a dozen of the Schumacher 1.5 trickle chargers over the years. Nine are currently hooked to machines for the winter & I usually click them on for a day or so every month to maintain the batteries.
Been a few years and it seems to work for me .......... although I do find at least one replacement battery is required yearly. I noted one dated 2011 when I hooked up the chargers for the first time this season that will be changed in the spring..... The newer maintainers have an indicator light denoting the battery has a fault and is not taking a charge.


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## Nut'n'Done (Nov 28, 2021)

If you have a few more $$ to spend then I would go with the maintainer below .
I have been using them for years and years with no issues.


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## Steve2444 (Sep 28, 2020)

Justwayne said:


> May i ask if one of the harbor freight battery maintainers will fully charge a dead battery given long enough time and whats the amp output? They charge a low or dead battery without overcharging? Automatic Battery Float Charger (harborfreight.com)
> 12v Deluxe Battery Maintainer and Float Charger (harborfreight.com)
> Im thinking the 9.99$ charger would work perfect for maintaining a low or dead lawnmower or car battery? Does anyone have one and are they reliable? I bought the 4$ alternator battery test light and used it a few times now it only reads 5 volts on a good battery. Some of their electronic stuff isn't good.


I have a bunch of these, been using them for years on my car and mower.
I have no idea if it will recharge a dead battery, I have a charger that I use once and a while when I forget to put the maintainer on the battery for a few weeks.
Then I put the maintainer on the battery to keep it topped off.
They usually go on sale for $4.95 or so. 9.99 is the usual full price.

Things I have noticed over the years with these maintainers, the weak link is where the uber thin wire attaches to the clamps, eventually it will break off from the clamp.
So you need to strip it and re-solder every one or two years. The rougher you are with it, fixing will be more often.


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## Old Thomas (Nov 28, 2019)

I have Schumacher maintainers from Amazon. HF should do the same job. Check to see if the HF units are tested by UL, ULC or some other testing lab that you are familiar with. I have checked HF and some things are labeled and some are not. I have also had HF things that went up in smoke. I wouldn’t leave their electrical devices energized and unattended but it is your choice.


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## turbo4 (Jan 30, 2021)

SARG said:


> I've accumulated at least a dozen of the Schumacher 1.5 trickle chargers over the years. Nine are currently hooked to machines for the winter & I usually click them on for a day or so every month to maintain the batteries.
> Been a few years and it seems to work for me .......... although I do find at least one replacement battery is required yearly. I


Im going to try one of these. The Battery tender chargers which i like are getting out of hand with the price. And i need several


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## FM3 (Aug 12, 2019)

Justwayne said:


> May i ask if one of the harbor freight battery maintainers will fully charge a dead battery given long enough time and whats the amp output? They charge a low or dead battery without overcharging?


That's what they're made for. They're the low-amp "tender" "maintainer" kind of charger that is intended to be kept plugged in for extended periods. The amps are listed in the detail section on those listings. They're less than one amp.

And if Harbor Freight censors their comment review section on products, they do a bad job of it, so I'd consider the review comments to be legit, and a whole lot of people like that HF charger. It was on sale for $6 last week by the way. I've seen numerous reviews for other chargers on amazon where people said this or that supposedly better charger sucked compared to their cheapo HF one. And this HF one is sold on there under other names for around twice the HF price.

Look at the amp output of such chargers. Most are 2 amps max, often less than 1 amp. That's fine and good for its intended use. Batteries like slow charging more than fast charging. Though probably anything 4 amps or less is basically the same in that regard.

A main thing to be aware of is lots of the "smart" chargers in recent years may not be smart if the battery is very low or completely dead. (If it's completely dead you'll probably need a new battery soon anyway since batteries don't like being completely dead.) If the battery is so low that the smart charger can't read it properly, then it may think it's already full, or not a battery at all, or a different voltage of battery, and then it may not charge it.

That's when an older, dumb kind of charger comes in handy that just puts out a constant power all the time and it doesn't care what it's attached to.

Some chargers have voltmeters built in instead of just LED lights, so if you walk by the battery every day you can see at a glance what's going on with it if you're concerned about over or undercharging over time. 

If you don't like leaving battery chargers plugged in 24/7 for long periods due to risk of whatever, the solar powered chargers work fine for slow charging too, and the small ones are basically incapable of overcharging/overheating a battery since they simply aren't capable of putting out much voltage.

Make sure whatever charger you get is intended for the battery voltage. 6v is different than 12v, and not all chargers can do both.


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## lenaitch (Feb 10, 2014)

I've had my motorcycle on a tender for 10 years. It's on its 2nd battery which is fairly typical. My LT sits on a tender and I think I'm into year six for that battery. Around here, tender time is typically mid/late October until late April/early May.


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## FirebirdHank (Jan 31, 2021)

A battery tender is designed to be hooked up and ignored for months at a time. They are more expensive than a trickle charger but are worth the money. I doubt one would work to charge a battery that is low or dead.


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## turbo4 (Jan 30, 2021)

When my car batteries are very low i use a 10 amp charger. Once the 10 amp starts slow charing at 1- 2 amps i put the battery tender on it. The 1 amp would charge it from very low eventually but at 1 amp
it will take many hours.


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## Steve2444 (Sep 28, 2020)

The HF maintainer is NOT for a dead battery, instructions state the battery must test at 12v prior to using.


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## Nut'n'Done (Nov 28, 2021)

FirebirdHank said:


> A battery tender is designed to be hooked up and ignored for months at a time. They are more expensive than a trickle charger but are worth the money. I doubt one would work to charge a battery that is low or dead.


This^^^^ 
If you want to charge a dead battery, you need a battery charger.

If you want to maintain a charged battery for sometime, you need a battery tender.


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## JustinRaney (Jun 1, 2018)

Theres a nice black and decker battery charger/maintainer which i think would work perfect. Amazon.com: BLACK+DECKER BM3B Fully Automatic 6V/12V Battery Charger/Maintainer with Cable Clamps and O-Ring Terminals : Automotive


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## raylo32 (Nov 25, 2006)

I have switched over from using separate battery chargers and those old school Battery Tenders to these. This one I have on my Vette and a smaller version for the motorcycle. They will do full charges or just maintain a battery as necessary. They have plenty of different cables to choose from and the connectors make it easy to swap them over.

Amazon.com: NOCO GENIUS10, 10-Amp Fully-Automatic Smart Charger, 6V and 12V Battery Charger, Battery Maintainer, Trickle Charger, and Battery Desulfator with Temperature Compensation , Black : Automotive


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## Nut'n'Done (Nov 28, 2021)

I hope you both have good luck with them.
I'm old school yes.
I still don't know how they get little workers inside the battery to desulphate without some expansion while minimizing heat cycles.
5 in 1 sounds like good odds for the price thou.


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## raylo32 (Nov 25, 2006)

The desuphation function is the least of my concerns since having these chargers means my batteries are never neglected. But, still, I bet they work for that, but probably within a narrow range of sulphation. But at some point of neglect and age nothing will bring a battery back to life. We have all probably had this happen at one time or other.


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## JustinRaney (Jun 1, 2018)

I like the amazon black and decker as its name brand and warrantied. Does have a graph of how long it takes to charge car batteries, lawnmower as well. I found it browsing a corvette marketplace that has the black and decker battery charger/maintainer for 49$ went and looked on amazon had the same one for 25$. Seems like it would be good for the lawnmower and automobiles if you hooked it up a day prior to using the lawnmower or automobile.


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