Batteries and battery tenders - not a good idea?

Any battery knowledge to share here?

Can battery tenders do more harm than good? Like, the cheap $5.99 ones from Harbor Freight?

I had all my batteries on these tenders (DieHard, Exide and NAPA, plus two 'vintage style' yellow-caps) this winter. They were inside my basement workshop, vented to the outside. Just for my own info, I checked voltage randomly over the months (typically 13.70 - 13.99V), and occasionally took them off the tenders for a week to see how the voltage would stabilize (typically 12.50 to 12.80v).

In middle of March, I noticed two of the 'no-maintenance' types wept some battery acid out of their top lids.

I cleaned it up, then:

- I took one of these off the tender and let it sit. It held 12.66v. I stuck it back in its car, fired up and it seems to work fine.

- I left the other one on the tender and used it in the 67 Satellite yesterday... It measured a healthy 12.56V when taken off the tender. I stuck it in the Satellite and it cranked poorly with no start. That's not usual for this battery.

So I shot some starter gas in the carb, then it fired. It ran well and the D/C gauge showed a good charge, so I took it for an hour drive. I stopped to enjoy the view. Went back to the car.. again it cranked poorly on start-up and then died. So I had to get a jump from a friendly passersby. Then it fired. I looked but didn't really notice any more acid weeping out of the top.

Again, the D/C gauge showed a good charge that stabilized and I drove it an hour back. I parked the car in my storage garage, took the offending Exide no-maintenance battery out and brought it home. Left it on my bench. This morning it measures a healthy 12.75V.

I'll take it to the Satellite and see how it cranks this morning, but in the meantime, -

- any advice as to what's going on with the no-maint batteries?

I didn't think they'd weep anything out the top, that seems like a bad thing.

Maybe this, or both batteries have reached its service life?
Did the constant low-amp 13.9 charge cook off some battery acid?

I just don't want to harm my batteries.

Thanks,
- Art

The cheap “trickle chargers” are junk, and are nothing more than a step down transformer and a diode...they will cook your battery.

You need to buy a “smart charger” that has electronics that know when to just maintain a charge by just floating at a very, very low current. Those will not “cook” your battery by overcharging it.

Battery Tender or a Marine Pro Charger are the ones I would buy. They start at about 30.00 and go up fo 200.00

Mark

I've had my green top resto battery on a tender in the garage(continuously) since the fall of 2015. I haven't taken the car out since then. A few weeks ago I noticed one of my outlets was dead. I traced it back to the GFI outlet the tender was plugged into. I reset the GFI and plugged the tender back in. It didn't light up like normal. Either the tender crapped out or the battery did. I haven't checked the battery to see if it has a charge any more.

Thanks Mark,



I hate that.

I'll head out to check the cranking power of this battery now..
- Art

I agree that the cheap ones are junk, but there is another thing to think about.Different types of batteries have what I was told by a battery manufacture guy, is that different batteries have different full charge voltages, and that some tenders don't charge that high, and they will never cut off. Say type A battery has a charge voltage of 14 volts, and the tender only goes to 13.5, it will never see a full charge, and never shut off.

Just because the battery shows say 12.6 volts dosent mean its good.had some at work that showed great but were junk.Oh yeah the one inmy 65 last year started it like a champ.went to local cruise went to start and nothing pretty much.Jumped and alt charging.Coming home had to keep revs up so MSD would fire right.Next day charged it checked it and over 13 volts.Turn lights on and went to 2 volts.We have tenders on the harleys.Mine is at least 20 years old.Always has battery charged as does my sons.Mine is a Harley one.Also charge the tractor batterys some in winter.Rocky

Do a load test on the battery.

Thanks for the insights guys, it's an evolving lesson. A battery's voltage can be fine, but if the amps aren't there - that's a problem. So yeah - just cuz it reads 12v+ won't automatically mean it's good.



Yeah, I was going to have this done at our local AutoZone if things went badly today - but it cranked over and fired just fine.. so not clear what happened yesterday - but I'll keep jumper cables close by, and discontinue the use of the crappy tenders, that's for sure.

Last year I had only two tenders, so I took the 5 batteries out of the cars , brought them inside, and rotated the tenders to different batteries every month roughly. At the end, I put them on a 2amp charger for an hour. They all worked normally.

Cheers,
- Art

my car batteries have lasted this long, not gonna start now, once every few months i go and charge up my batteries to freshen them up...heard stories of fires, burning out the wall sockets to drawing more electric per month for those on a fixed budget...just saying..

I have used multiple Battery Tenders for many years with good success..
Except last year I went out into the garage and was surprised to find 1 of the Battery Tenders was super hot... A closer examination showed that it had an internal short and its bottom case had actually come apart due to its extreme heat exposing all of its internal components and transformer.
I called Battery Tender to report the problem since it had a 5 year warranty and they asked me to send them some photos of the defective Battery Tender. I did and they responded they have never seen a unit having this type of defect???

Anyway they sent me a new replacement Battery Tender which I never used and gave to my son. After having the original Battery Tender shorting out I discontinued using any Battery Tender. Funny about 2 weeks later, Battery Tender contacted me and requested I return the defective for their inspection and failure mode analysis... However I had already threw the defective unit in the trash..

So in the end I would caution anyone using a Battery Tender to check it occasionally for overheating as to avoid a possible fire.

Just my $0.02...

I never trust them. I just disconnect my car batteries not in use for the winter & ocassionally fire them up throughout the odd seasons. Any of my cordless drills etc. I always unplug when I am not out in the garage. I have heard & read too many horror stories about them either over charging & causing fires or shorting out & causing fires.

IMO this is a better charger, safer and better for your battery's.
LINK to battery minders.

I use one of these every 1-2 months for 48 hours.

Once its 100% LED lights the power consumption drops to 2 watts as measured by a Kilo-A-Watt power meter on the 120 volt outlet. At this low level it should not be overcharging a 12v lead acid battery.

https://www.pulsetech.net/xc100-p-xtreme-charge-12v-battery-maintenance-charger-desulfator.html/

I have thought about buying one of these
to check the health of the battery “guts”
beyond what my MAC 130 amp load tester can do:

https://www.amazon.com/Associated-Equipm...uct_top?ie=UTF8

While your talking about batteries, I have a fairly new marine deep cycle battery that won`t go above 75% charged. I assume the plates are sulfated. Any way to get it back or is toast? I used my good optima charger on it and still won`t go above 75%. I thought the trickle charger would of helped it through the winter but I guess not.

look at the battery minders, my link above^^^

Bingo...

All my batteries go in the basement when not in use...


When needed, a little time on the charger, then back in the 'tray'...

If a pulse type charger will not bring a marine battery to full charge,
find the bad cell(s) with one of these:

https://www.amazon.com/East-Penn-Manu-Ba...9H2RG54DRMZYEJW

Then use an ounce of this:

https://www.batterystuff.com/battery-restoration/fluid/BE12oz.html

Just in the one bad cell.

Hook the battery back up to the pulse charger for 2-5 days.

This is kinda “last ditch” first aid for a wet 12v battery but more than half the time will extend the working life.

Thanks, will give it a try.

A few years ago I asked my automotive battery supplier about which kind of battery charger was best to use. They said they only sell one battery charger and this is it. I have used it long term(3-4 months at a time) with no problems. FWIW Smart charger.


From hanging around airplanes I learned about battery minders...but I use this new to me 28 volt power supply to test and maintain the battery in this cessna. It provides plenty of amps to test lights and radios without the engine running.
Going flying tonight in a about an hour.

I have owned and used 2 different load testers like you show above, neither was worth a sh!t because they really can't put the correct load on a battery. I have used my hand held load testers and all three batterys show good. But in the truck you can tell something is wrong. I take them out and to the battery supplier and they test them with a real load tester and find one bad. Waste of money the hand held ones IMO.
You are just as good to put a volt meter on your battery and have someone crank the engine and watch the voltage.

This is still the only real way to load test your battery. The battery store has one and they test every battery I replace in my truck fleet. My trucks have 3 batterys each and I buy my far share of battery's.
LINK

The operative term is "hand held", anything that fits in the hand isn't gonna have a carbon pile sufficient to put a real load on the battery.

Not sure why you think you need a battery tender. I just pull one of the cables in the fall, and reattach it in the spring then fire it up. Any battery that can't hold a charge with no load on it for six months, is ready for replacement anyway.

That's the long and short of it. Just pulled my 92 diesel out for the summer. Sat for 6 months, didn't disconnect the battery. Turned the key and fired right up just like every year for the last 7.

Ditto my roadrunner.

This has worked well for me also. Less expense, less fire risk vs trickle chargers and batteries seem to do fine for many years.

Used one of these for years when I was wrenching in the past...


So did a lot of other guys I knew, too...

I have used Battery Tenders for about 15 yrs. Before that, I used one of those switches on the similar to this:
https://lmr.com/item/BDS-14301/79-04-Mustang-Top-Post-Battery-Disconnect-Switch

My experience with these switches is only good for the season you are using the car. I used these switches but in the end, my batteries were lasting 2-3 yrs. I'm guessing its because the batt is switched off during a long Fall/Winter period. That gets expensive buying batts that often.
That is when I went to a Battery Tender. On my Turbostart agm red cap battery, it is working great since 2010. I never had a battery last this long. Now I leave the Batt Tender on the battery all Fall/Winter storage and when Im not driving the car in my garage and it keeps my clock ticking. I have gone thru 1 batt tender that lasted about 8 yrs. All that happened was the Grn and Red LED stayed on ALL the time. Never turned Green only. Stuck a new one on, my batt is still going strong.
I would not use the Batt tender that is 1.25amp on a small motorcycle type battery. I used this Batt tender on my Honda Generator with the small m/c battery. It did dry it out. Get a Batt tender that is .75 amp for m/c batteries. For me, love them.

We switched from Battery Tender to Tecmate - Optimate "smart" chargers after several failures of the Tender's.

Yes they were very popular back in the day.

There is a reason that they cost 30 bucks and the good ones cost 600 bucks.

I just installed a Noco genius charger for my trailer onboard charger. Nice unit. The are marine units. Not cheap though.

You can get them for multiple banks, so one charger can charge different banks at different rates.

Ctek is another good one. I have one where you can switch from car batt to m/c batt. Looks like they make charging kits for Ferrari too.

https://smartercharger.com/

https://www.ferraripartscatalog.com/ferrari_70003483_battery_charger_kit_p/70003483.htm

The battery in one of the road runners is at least 12 years old (red top optima that was in the car when I got it) and is still good...it's on the battery tender whenever the car is in the garage. The battery in the Indy Ram is about 10 years old, also on a battery tender.

We had a carbon pile big tester at work.Then we got the new hand held ones.I always used the big carbon one.It actually put a load on.it was adjustable so if you had a say 400 amp or 800 amp you adjusted the pile for the amps.Rocky

I am two years in on the third battery in 25 years of road time...


The first two went 10+ years...


Neither were ever on a 'tender'...

I am the GM for a battery distributorship so I will see what I can add.

We sell the Deltran "Battery Tender Plus" they have a ten year warranty and we have had to warranty one or two in the last 6 or 8 years. At $60 they seem to be a good value, they are reliable, and they seem to do a good job. That being said if you unhook the battery you should be good for months. I would put them on some kind of charge every 3 or 4 months just to help fight sulfation. We use 4 months as a benchmark to charge the warehouse inventory and the batteries we have in the field.

Load testers, the hand held ones are junk, they put a fixed load on the battery, so if that load is suited for the CCA of the battery you are testing you are in good shape. However those testers are more likely to tell you that a bad high CCA battery is good and a good low CCA battery is bad. The only way to test batteries is with a hydrometer and an adjustable carbon pile tester. More and more batteries are being made "Maintenance impossible" these days so using the hydrometer is getting more difficult. There is also lots of digital testers out there, they are not bad but nothing beats a carbon pile load tester.

Chargers, in my experience anything with a digital read out or that tells you percent of charge isn't all that good. When you have a battery that is drained below 12V the automatic chargers will shut off too early %99 of the time. They simply sense voltage and that doesn't always correlate to the battery actually being charged all the way, using a hydrometer to get the specific gravity right is the end all reading for state of charge. Often with the auto chargers you can unhook them for a few hours and hook them back up and they will continue the charge. I will say this, we actually use one of the chargers that Challenger 1 posted and it is pretty good for an automatic charger. It was given to us by a salesman and we have used it for AGM batteries for about 5 or 6 years now and it does pretty good but like all auto chargers it falls short on batteries that are below 12V at the start of the charge.

What do I use with my stuff? I have the small optima battery charger, it has worked great for the optima battery in my Barracuda(8 years old) and the one in my Jeep. It has also done a good job of charging the small SLA battery in my sons electric 4 wheeler. Its simple, its well priced, and it is above average for a "smart" charger. I have a large roll around Schumacher charger that I use for jump starting or heavy charges but luckily its something I seldom have to use.

Thats my .02 I am no battery scientist but I have been dealing with automotive batteries for 20 years now.

There is for sure a sweet spot of usage for batteries. The ones that last 8-12 years are usually not used often, but kept clean and used "just enough" to stretch the life span. However a lot of the batteries that last so long are bad as far as CCA to spec goes but they still have enough CCA to start the vehicle. Often car guys want the most CCA they can possible get not realizing that the 440 six pack roadrunner only needs like 400CCA to start, so that 800CCA battery can still start it for years after it would fail a load test.

My dads 08 ram was having no problems starting recently, it had 7 year old batteries in it. The truck still started fine but both batteries tested bad at the rated CCA. Both batteries together were good for about 750 CCA instead of 1700.

I didn’t even read all these posts because this has been discussed so often. There is not reason other than laziness to leave a battery tender on for extended amounts of time. Get of your lazy butt once in awhile and put it on and take it off the next day every 2-3 months. This also gives you a good chance to burn a few calories and check things over. If reading a few nightmare stories about fires from these things doesn’t bother you, it should.

Depends on how much "parasitic draw" the car has. I have only one car with no parasitic draw and it'll start right up after sitting for months. All of my other cars have devices that draw milliamps when sitting idle and eventually the voltage drops enough to cause starting problems.

I use the Schumacher SE-1-12S onboard chargers.

Three batteries in since 92 in my bird including the one there now,started every few months during the winter,never need one !

So take a battery cable off. Zero draw.

I use the deltran battery tender on the Duster and my Truck which I don't use so much in the winter.

The Duster's battery is 10 years old this month (Autocraft Silver) and tested at 535cca (525cca rated)

My Truck's battery is 7 years old (autocraft gold) and tests at 618cca (625cca spec).

I can't complain. I also use it on my lawnmower battery.

That's pretty much what I do. Disconnect the battery and charge it once or twice over winter.

My late father always used tenders on the four batteries on his houseboat and funny thing just the opposite occurred, he was always replacing them. Seemed to never last more than 3-4 years at most so I have no faith in battery tenders not to mention the fire hazard. I just start my cars if not driven or occasionally put a charge on them and I get good life. Same thing for my other equipment. The battery in my Kubota tractor lasted about ten years and most of the time that machine sat. It’s just more over rated BS just like a lot of things marketed to brain wash us. Another example is synthetic oil. My cars get conventional oil and my work vans always last me many years and well over 200k miles before replacement. It’s just all part of the feel good thing doing all the extra unnecessary BS. But this is my experience and opinion and of course other results may vary and are open to debate

I have a battery disconnect that I use when not driving the car to avoid any draw. Winter time it goes into a boat storage bin in the closet. Check the voltage once a month and see if it needs charged. Brand new battery, so trying this vs leaving it in the storage unit all winter.

Then you lose the whole purpose of those devices.

That is what I used to do was disconnect the cable, then got a shutoff switch, but battery life was horrible. Sulfate sets in being dormant. This is leaving it in my car in the garage. Could be in other climates your battery life can be longer by just disconnecting. Zero draw does not work for me. I live in WA state, and don't know why I had terrible batt life until I got the Batt Tender. My current batt has lasted 8 yrs strong. That's the longest ever for me.

Thanks all,

Good info to absorb. I'm chucking the tenders. I still won't leave my batteries in the cars over the winter, but it's easy to check voltage thru the winter, and use a light 2A charge only if needed.

Only one car has significant parasitic draw to maintain memory functions, but it has its own dedicated tender. The rest are old and I only lose the radio presets in a complete power-off.

All my batteries have lasted me over 5 years, one is 8, with minimal maintenance, just a quick freshen-up charge in the spring.

One of the reasons I tried the tenders was because my one, expensive, vintage red-cap sulfated in less than 4 years. That one I treated the same as the others, taking it out and leaving it alone all winter.. but it was a true cap battery, needed to have distilled water level checked and charged and filled, specific gravity checked, etc.. and I kept after it real good too.

I bought two yellow-cap maintenance-free vintage repops, and they have been OK. One is 6 years and getting weak.. but neither one cooked any acid out on the battery tenders this winter.

Cheers,
- Art

Wasn't it a charger or tender that caused the unfortunate incident in Rhinos garage?