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Technical Can you test a "Battery Tender"

Discussion in 'The Hokey Ass Message Board' started by 5window, May 29, 2018.

  1. 5window
    Joined: Jan 29, 2005
    Posts: 8,355

    5window
    Member

    I had a battery not maintain it's full charge while on a Battery Tender type trickle/float charger device (actually a Schumacher). Another unit seemed to charge it up. Is there any way to test the functioning of these devices or are they "let me down, I throw you away" devices. Are there any benefit to one brand over another?
     
    chryslerfan55 likes this.
  2. Atwater Mike
    Joined: May 31, 2002
    Posts: 10,702

    Atwater Mike
    ALLIANCE MEMBER

    I had a Schumaker 12V charger given to me in Sacramento in 1970. Took it to Santa Cruz, Aptos, San Jose, then Merced. Never failed me, until I hooked it up to an old battery (for a 'fail-safe') with leads going to a vat for the electric rust removal trick.
    DON'T put a battery into that mix...it'll burn up your charger, within an hour!
    Damn, that charger was ACES until last year. (1970-2017) R.I.P.

    There may be a simple fix, haven't checked it yet. Bought a new one, but liked the old one!
     
    chryslerfan55 likes this.
  3. Mr48chev
    Joined: Dec 28, 2007
    Posts: 30,021

    Mr48chev
    ALLIANCE MEMBER

    You should be able to check the voltage on a battery, hook up the tender and read a slight difference in the voltage. I've got one out in the garage and might try it on a battery I have out of the rig.
    I don't know about tenders but some chargers will drain a battery if left hooked up and not plugged in or turned on.
     
    doug j likes this.
  4. sevenhills1952
    Joined: Mar 14, 2018
    Posts: 954

    sevenhills1952

    With voltmeter check a battery that needs charging. Let's say it reads 11 volts. Put the trickle charger on and it should go slowly up...11.1, 11.2, etc. with time.
    The good thing about those tenders...it may only be 1/2 (500mA) amp. So something that sits a long time it keeps battery up without overcharging.

    Sent from my SM-S320VL using Tapatalk
     
    lothiandon1940 likes this.

  5. Will they cause your alternator to go bad if you forget to disconnect them and start the car?
     
  6. tubman
    Joined: May 16, 2007
    Posts: 5,851

    tubman
    ALLIANCE MEMBER

    I had a battery tender go bad once. The circuitry that caused the charge to "float" failed and it kept charging at it's maximum rate all winter, and the next spring, the battery was boiled dry and no good (this was in a boat). I had no idea at that time what had happened, so I contacted the maker (I think it was Shumacher) and they said to "send it in". I did and got a new maintainer and a nice note explaining what had happened. If you notice most of these come originally in packaging that tells you to contact the maker rather than the retailer in case of problems. If it failed completely, you should be able to tell with a voltmeter, like the others have said.
     
  7. sevenhills1952
    Joined: Mar 14, 2018
    Posts: 954

    sevenhills1952

    No. It's like having any charger on a car and starting it, won't hurt alternator (or generator). You should disconnect once it starts.

    Sent from my SM-S320VL using Tapatalk
     
    pat59 likes this.
  8. Truck64
    Joined: Oct 18, 2015
    Posts: 5,074

    Truck64
    Member
    from Ioway

    Is this one of their more recent products with LED display and high impact plastic? If there was a power glitch it may do that. I'll have to experiment with that on a unit I have.

    Can test any charger, just monitor the charging voltage periodically as it goes through the routine. This is a good idea anyway so you become familiar with the amperages, numbers, and how long it takes. Float chargers are good at what they do but a lot of people don't grok they are only designed to maintain a float on an already fully charged battery.
     
  9. jimmy six
    Joined: Mar 21, 2006
    Posts: 9,967

    jimmy six
    ALLIANCE MEMBER

    cheap ones are just that...cheap.. with a tender always start with a fully charged battery or close to it. these things are maintainers not chargers.. I've been using them on my motorcycles for yrs without problems.

    these solar jobs work good to, i've had one on my car hauler trailer and it's always fully charged for the wench and lights...NO it's not for a trailer Queen
     
    Truckdoctor Andy likes this.
  10. 8-Track
    Joined: Jul 26, 2008
    Posts: 395

    8-Track
    Member

    Battery tenders are garbage they will charge your battery to death. Get a C-TEK charger, it will only charge when needed.
     
    scrap metal 48 likes this.
  11.  
    lothianwilly71 likes this.
  12. sevenhills1952
    Joined: Mar 14, 2018
    Posts: 954

    sevenhills1952

    Another inexpensive thing you can do is plug the battery trickle charger into a timer, so it will charge an hour a day or however long you want.

    Sent from my SM-S320VL using Tapatalk
     
    Petejoe, bct and Texas Webb like this.
  13. bct
    Joined: Apr 4, 2005
    Posts: 3,099

    bct
    Member

    look for a small spark when disconnecting or place an amp meter inline so see if there is any flow.
     
  14. bchctybob
    Joined: Sep 18, 2011
    Posts: 3,248

    bchctybob
    ALLIANCE MEMBER

    Just too weird..... I just hooked up my charger to top off my spare battery and was thinking about the two Sears battery tenders I have and how I 've never been real sure whether they are working right or not. I step over to the computer, bring up the HAMB and there's a thread on that very subject.
    Is this site psychic or what? I'll be doing some battery charger testing tomorrow for sure.
     
    5window likes this.
  15. 5window
    Joined: Jan 29, 2005
    Posts: 8,355

    5window
    Member

    Thanks to everyone for their replies. I am curious about your statement here. Do you refer to actual "Battery Tenders" as garbage or the whole class of battery attending chargers? What you say may be true, but I am always a bit skeptical when a generalized absolute statement like this is made. Is this your opinion, experience or based on actual studies/data? I really would like to learn here. The C-tek website looks impressive (easy to do) and their products get good reviews-but they also cost at least twice what the most expensive of the others does. It only has a 5 year warranty while others have 10. And things like "unique reconditioning mode" and "8 step charging program" sound like a lot of hype without really explaining anything. So, what's up?
     
    tubman likes this.
  16. I'm glad you are looking out for her.
     
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  17. Engine man
    Joined: Jan 30, 2011
    Posts: 3,480

    Engine man
    Member
    from Wisconsin

    The maintainer type chargers are meant to be permanently connected to the battery.
    https://www.batterychargers.com/en/...lly-automatic-battery-maintainer#where-to-buy

    The website shows out of stock. Maybe they quit making them.

    They are used on vehicles that aren't driven at least every week. I had a Schumacher unit on a truck that I drove in the winter would use maybe once every couple of months in the summer. One evening I heard a bang and didn't think much of it. The next time I wanted to use the truck, it didn't start. When I looked, the end of the battery had blown out.
     
  18. Don't do this...spark + Hydrogen (the lil' bubbles you see when the battery is charging)= BOOM!
    First thing I was taught at trade school about chargers was never connect/disconnect a battery charger with the power on.
     
  19. Truck64
    Joined: Oct 18, 2015
    Posts: 5,074

    Truck64
    Member
    from Ioway

    Battery technology, lead-acid automotive start type anyway, was hashed out long, long ago. Those classic Shumacher battery chargers that everybody owned at one time, are just about perfect. They figured this shit out long ago. They are based on a "taper charge". The current starts out high, the voltage low. As the battery accepts the charge the current drops off to almost nothing, and the voltage tops out.

    The caveat with these though, is they are "dumb" in the sense that if they are left connected indefinitely, they will boil the electrolyte dry and ruin the battery. At least in warmer temperatures. The old school chargers, retail type that Sears and Monkey Wards sold were "sized" (current wise) to be just right for a typical 50 or 70 Ah car battery. Especially in January. You can see this if you connect a voltmeter and observe where the voltage tops out at.

    That's what most people don't understand about batteries. They need a higher charging voltage as the temperature goes down, to overcome the increased internal resistance. About 2 volts above and beyond the OCV of a battery (12.65 volts at 77° F for a standard lead-acid battery with filler caps) and moderate outgassing is required to reach a full charge. At zero degrees it goes even higher. Over 15 volts is not out of line. The "dumb" chargers are not regulated as such, but they were "sized" to prevent problems except for the most determined idiot. In cold weather - real cold, they probably could be left indefinitely as the voltage will never rise much above a "float" charging level. In the summertime though they would max out at 17+ and cook it in short order.

    Batteries that charge and discharge normally convert the lead paste into sulfate. That's why specific gravity is measured, the acid in the electrolyte didn't go away, its simply bound up in the plates. Recharging converts the water back into sulfuric acid. But the sulfate will quickly turn into hard, permanent crystals if a discharged battery isn't recharged.

    So "desulfators" is kind of a misnomer. The battery gets desulfated every time it is charged, that's how it works. What's controversial is whether this hard permanent sulfation can be reversed. My opinion it is best to keep them charged up thoroughly and prevent it from occurring in the first place. Trying to charge a sulfated battery has been compared to washing your hands wearing rubber gloves.

    A slight overcharge from time to time is also beneficial, it "equalizes" the cells so each one is close to the baseline. This is right around 16.25 volts for a few hours. The modern chargers with their algorithms can do this safely, or at least without having to monitor the process. I have a couple different chargers, with "smart" technology but there is no substitute for an old school charger, and I use it often. As mentioned a start/stop timer works great with these.

    http://batteryfaq.org/
     
    Last edited: May 30, 2018
  20. 19Fordy
    Joined: May 17, 2003
    Posts: 7,298

    19Fordy
    Member

    8-track is correct. Can't go wrong with a C-TECH.
     
  21. 5window
    Joined: Jan 29, 2005
    Posts: 8,355

    5window
    Member

    C-Tek warranty is 5 years, Battery Tender warranty is 10 years. Price is reversed, something isn't right. Neighbor has solar powered HF units doing just fine. Confusion reigns.
     
  22. Truck64
    Joined: Oct 18, 2015
    Posts: 5,074

    Truck64
    Member
    from Ioway

    Battery Tender has something with their warranty that makes that a no-go, can't remember what it is. As I recall it's customer pays shipping both ways. Could be wrong on that. I had one croak and I pitched it. The second one has held up fine. As I understand it the flea-powered units (0.75 amperes) like the battery tender would take days to fully recharge a depleted battery. So the lights blink for several hours, and then they automagically switch to a float charge, to prevent boiling out the electrolyte excessively. For a thorough recharge some amps need to be there basically.

    This is where "sizing" of the charger (versus a maintainer or float charger) to the battery ampere hour capacity is important. You can apply 50 amps and quick charge a dead battery in an hour but it may warp plates and cause trouble or, use a wall-wart milliamp charger and wait a week or two. The proper charge and charger to a given battery is a compromise between a slow thorough safe charge and reasonable time frame. Like I said the old dumb chargers are just about perfect in this regard. They don't need a wifi connection or software updates or refuse to charge because the battery is dead, or refuse to operate in subzero temperatures etc.

    Just don't forget about it and leave it hooked up indefinitely or, use a timer. I use the dumb charger to get it all the way up, and then use the float charger.
     
  23. ST62
    Joined: Jun 27, 2017
    Posts: 69

    ST62
    Member

    I have also seen battery tenders go bad, I tell folks not to trust them-just use them every few weeks for a couple days or so.
     
  24. Truck64
    Joined: Oct 18, 2015
    Posts: 5,074

    Truck64
    Member
    from Ioway

    Then there's no point in owning one. The whole idea is to float charge semi permanently, usually through the off season.
     
  25. dorf
    Joined: Dec 5, 2008
    Posts: 1,087

    dorf
    Member
    from ohio

    i had 2 that would not work after a summer off . plugged them in struck the wires against each other .been working ever since .
     

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