# Did you know a float/trickle charger can KILL your battery?



## DaleH (Apr 15, 2016)

_Posted this on another boating forum I frequent ... thought some info may be valuable ..._

The charging voltage is always much higher than the maximum possible or 'usable' voltage. The* ideal full power charging voltage for lead acid marine batteries is 14.2 to 14.4 volts (double that for a 24V system)*. Sometimes one only sees 13.8 to 14 (like on my boat volt meter gauge) but that is more the variability in the accuracy of that measuring instrument.

For the best charge result, one must also wait up to ~2-days for the surface effect from the charging to dissipate; otherwise you're fooling yourself with a false (higher) reading. But if you can get 12.4 to 12.7 from a sealed battery ... post-charge, you're good to go!

Note that 'float', trickle or maintenance chargers only bring batteries up to 13.8 volts ... which is a slow incomplete charge, sulfate deposit building, excessive gassing process and one that results in reduced battery life. *If you remember anything here, know that continued use of a float or trickle charger will also eventually ruin a battery.* It essentially keeps the battery as a 'boiling' point, which reduces the electrolyte, exposes the plates, and causes them to sulfate.

Any values seen down to 11 volts as the OP saw means that the plates have sulfated and portions of the lead plates are now rendered useless. It may take a charge ... but it won't hold it, which is why you need to wait a day or two to get a good reading.

If one doesn't maintain a good charge (> 12) on a battery *within as little as 3-days of a deep discharge*, the battery can go bad by sulfating and once they do, those plates are permanently damaged and cannot be recovered.

Battery Sulfating 101:
When a lead-acid battery is discharged a soft lead sulfate material forms on the battery plates. During the battery's recharge, that material is lifted off the plates and recombined into the electrolyte. But if left in a state of discharge the lead sulfate material begins to harden and crystallize, forming deposits a permanent insulating barrier. The accumulation of such deposits - 'sulfation' - is the most destructive process in the life of any lead-acid battery. As the barrier becomes thicker and thicker the battery's ability to accept a charge - or deliver full energy - is diminished. Net result ... you'll need another battery!

Ideally for the best charging results, one should use a hydrometer to measure the specific gravity of the electrolyte, but of course that's only practical if the battery has caps to provide access to the electrolyte.


----------



## JMichael (Apr 15, 2016)

I don't know the source of your information and I'm not trying to dispute or confirm it. But I can confirm that between my boats, motorcycles, ATV's, and lawn mowers, I would frequently lose batteries after only 1-3 years use. Every since I started using Battery Tender Jr on all of them, I've yet to lose a battery in less than 4 years and some last as long as 6. I've been using maint chargers for about 20 years now.

I should probably add that I've never been one to remove my batteries and store them inside during the winter either. And I know that sitting out in the cold without being used is hard on a battery and storing them inside might negate the need or benefits of a maint charger but I'm too lazy to take them all out and I don't have a climate controlled area to store them in anyways. And my boat has a marine charger on it now instead of a Battery Tender brand maint charger.


----------



## Ictalurus (Apr 15, 2016)

JMichael said:


> I don't know the source of your information and I'm not trying to dispute or confirm it. But I can confirm that between my boats, motorcycles, ATV's, and lawn mowers, I would frequently lose batteries after only 1-3 years use. Every since I started using Battery Tender Jr on all of them, I've yet to lose a battery in less than 4 years and some last as long as 6. I've been using maint chargers for about 20 years now.



X2


----------



## richg99 (Apr 15, 2016)

I learn something every day on here. 

For many years, I've added a simple house/lamp timer to my battery charging setup. After the initial day, when the lamp timer calls for the battery charger to kick back on, some chargers revert to just two amps. I never thought that would be a problem. 

The Harbor Freight chargers that I am presently using do not revert back to two amps. They charge at ten amps ( one is smaller at 6 amps). Looks like I should just adjust the time and leave the chargers at the higher amperage. Thanks for posting. 

Incidentally, since I added the lamp timer...I've had far fewer battery issues. 

A little dab'll (everyday) do ya!

richg99


----------



## DaleH (Apr 15, 2016)

I think what you two might be doing is fine ... it probably is the person who connects a battery to a trickle charger and leaves it there all Winter that might burn the battery out.

Personally, and it has worked for me for 40+ years of boating, I give a full charge in Spring and Fall. 

Also keep the battery clean, as they can discharge without anything connected, just by an accumulation of dirt and crap (which holds condensation that completes the circuit in certain ambient conditions) on the top of the case.

When one tops off batteries with distilled water, wait 2-3 days to be fully converted into acid before charging ...


----------



## CedarRiverScooter (Apr 15, 2016)

Maybe snake oil, maybe it actually works:

https://www.pulsetech.net/PP12L-PowerPulse-12Volt-Battery-Maintenance-System-7291.aspx


----------



## richg99 (Apr 15, 2016)

Cedar...Amazon gives it 4.5 out of 5. I didn't note how many reviews, though.

richg99


----------



## lovedr79 (Apr 15, 2016)

Same here, battery tender has added years to my lawnmower and street bike battery life


----------



## timsmcm (Jul 13, 2016)

I have been using a form of the battery tender for more than 25 to 30 years if memory serves me corectly. I do not leave a battery tied to one. Every car, motorcycle, boat, mower, or truck in my stable has a tender pigtail. If it is not being used it gets a charge every week. I have had batteries last more than 10 years. My tender has paid for its self over and over.
Not connected to battery tender at all. Just think it is a great product used in the right manner.


----------



## jethro (Jul 14, 2016)

Looks like I have been doing the right thing all along! Shocking.


----------



## driz (Jul 18, 2016)

I use a HF tiny 1 or less amp trickle charger that I have had for many years. A while back I tried laving it sitting hooked up to my smaller batteries for a week or so. The results werent good at all. It didn't seem to hurt the big ones but sure did kill the smaller ones. Not any more. Now I just hook it up on a big battery for a day then rotate it and do it again in a few weeks. The small ones only get over night if that. I like to keep them in the basement where they aren't sitting in the sub zero too.
I think it all comes down to the modern circuitry on quality (read as $$$$$) chargers like battery tender. The old ones just trickle while the new modern types sense the charge and regulate themselves much like the chargers in your NIMH battery powered tech toys. I read an article recently that said the chargers (HF=????????) have the same circuitry and sensors that allow them to sense early sulfation. They rev up long enough to, for lack of a better word burn it off then revert to their idle mode or whatever they do . That's what you are paying the extra dollars for. 
Once I saw an article a hardcore biker wrote about keeping all his batteries alive over winter layup. He wired them all in series on his garage bench and plugged them into an extension cord to the door opener. Every time the door opened or closed they all got 3 minuites of divided charge all winter long. He claimed it worked great for him.


----------



## Johnny (Jul 18, 2016)

what is the take on the "amperage" of battery tenders ??
and, it is "TENDER" and not "CHARGER". . . huge difference in the two.

I read somewhere last year that the average battery tender
supplies 12 volts and anywhere from 300 to 800ma (mili-amps)
on a steady basis. (not 13-15 volts). 

If you have a battery "tender" - check the label for the input/output values and see what it says.


- - - Just curious - - -

Edit: in the Southern States like Florida, Texas, Arizona, etc, we use 
the stuff that has a battery in it 12 months out of the year and the summer
heat is what kills the car batteries - not over charging. (in most cases).


----------



## -CN- (Jul 18, 2016)

I've only used them on the batteries in my motorcycles. A Battery Tender Jr. is the brand I use, I have a few of them. There's lots of talk about this in the motorcycle community, and the main conclusion is that their purpose is for winter storage, or for prolonged non-use. What I used to do was plug in the tender and leave it on all winter. This was when the bikes were stored in a garage that didn't often get to below freezing temperatures. Batteries have lasted many years, however, I never kept a bike more than 6 years (except one that I have now) so I can't speak to the longevity beyond that. Except to go to a lightweight battery from AntiGravity or Shorai for racing purposes, I never replaced a battery - with one exception - when storing a motorcycle in a shed, exposed to the cold temperatures of winter all winter long, while on a tender. The battery needed to be replaced the spring of the second year. Most say this isn't contributed to the Battery Tender, but rather the cold temperature. I've since changed my method of storage, and I pull the motorcycle batteries and bring them in the house for the winter, fully charge them, and store them. Some batteries are a bit weak in the spring, but most times I can install them and they start the bike right up. Haven't used the tenders now for a few years. But this next winter if I remember to I'm gonna plug the batteries into the tender a few times for a couple days each time throughout the winter. 
Tenders work. But it's always best to store your batteries in a warm place. The combination of the two is probably the best way to go.


----------



## onthewater102 (Jul 18, 2016)

I cannot find my way back to a writeup by an engineer for one of the big battery companies I was looking at prior to buying my current charger, but basically said what Dale is saying about low voltage battery tenders that only send a small amount of current do contribute to sulfating of the plates & that in order to safely maintain a charge on a lead-acid battery you need a pulse charging system which alternates charging pulses and discharging pulses to both avoid overheating the electrolyte & break up lead-sulfate before they deposit and crystallize on the plates.

https://www.tstonramp.com/~rhinocharge/pulsetech_faq.html

Different source but same idea


----------



## abevelheimer (Jan 21, 2017)

yep I recommend a timed charger a 1amp or .5 amp charger should do it you can set a wall timer to make it charge a certain time and then it shuts off


----------



## TNtroller (Jan 21, 2017)

I've used BatteryMinder brand for several years after a "BatteryTender" ruined/killed a motorcycle battery over the winter. BatteryMinders are on my RV/boat/mower/yak batteries when they are not being used.


----------



## driz (Jan 21, 2017)

I still have my little HF $3 trickle charger but you can bet the next one i buy won't be [-X and El Cheapo. No way no more. Also All my batteries come in now wife bitching be damned. By Dec they are snuggled in the basement.


----------

