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  1. #1

    Overtemp the Battery Tender?

    Anyone have a problem with battery tender sitting in front storage hatch? I rigged up one for each ski yesterday by drilling small ish holes in bottom of storage bin and battery compartment cover. Afterwards I got to thinking about max temperature inside that compartment. The skis are on a lift above the canal in direct central Florida sunlight with covers on them. The battery tender says max temp 50C (122 F), so I'm guessing it might exceed that when it's 90F OAT by 10-15 degrees.

  2. #2
    Click avatar for tech links/info K447's Avatar
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    What are the temp tolerance specs for the Battery Tender model you are using?

    Also, does that model of ‘battery tender ‘ do proper temperature compensation?

    As the battery temperature changes the optimal charge/float voltages for the battery will change. A good charger will have a temperature sensor (may be internal to the charger) and attempt to adjust the output voltage to match what the battery needs* at the sensed temperature.

    Some battery chargers have an external temp sensor that is placed against the actual battery so the charger can tell the temp of the actual battery. My primary charger/maintainer is a BatteryMinder model with external temp sensor.


    * The battery type also matters. An AGM battery has different voltage requirements than an old-school lead-acid battery.

    Some chargers are not fully compliant with AGM battery voltage requirements, creating under charging condition despite the charger showing a ‘green/full’ indicator.

  3. #3
    Box says it's good with lead acid, AGM, and gel type batteries. It lists maximum operating temperature of "50 degrees C Typical," whatever that means. Apparently this model of BT (BT Jr in my case), does not have temperature compensation (the BT Plus does).

    I'm about to find out how hot it gets in there via my trusty wifi controller for the bbq grill; it's plenty accurate.

  4. #4
    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by Cranofwaterfell View Post
    Box says it's good with lead acid, AGM, and gel type batteries. It lists maximum operating temperature of "50 degrees C Typical," whatever that means.

    Apparently this model of BT (BT Jr in my case), does not have temperature compensation (the BT Plus does).

    I'm about to find out how hot it gets in there via my trusty wifi controller for the bbq grill; it's plenty accurate.
    50 degrees Celsius is about 122F. Online converter is your friend (and you posted the 122F in the first post)

    Running electronics really close to their maximum temp spec generally results in shortened lifespan. The charger will generate some internal heat so it will be warmer than the surrounding air.

    What kind of battery do you have installed in there?

    How old is it?

    Without temperature compensations a fixed voltage charger can overcharge a battery as the battery temp rises. So you have sun heating and you have a charger that will lean towards excess charging voltage into the very warm battery. It seems possible (likely) that the result will be shortened battery lifespan.

  5. #5
    It's supposedly a "smart" charger and when I went out to check both of them around noon, they both showing solid green (fully charged). I did my temp check with the bbq grill temp controller and surprisingly temp only went up to 88F after two hours (ambient 84F). Batteries are OEM Yuasa YTX20L-BS s new 5/2018. It doesn't get THAT much hotter here even in August, low 90s and <mile from Atlantic Ocean. So I think it will be ok even with OAT in low 90s. Guess we'll see in 5-6 months.

  6. #6
    steve45's Avatar
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    I doubt that a charger like that will generate much heat. The battery is kept fully charged almost all the time. A maintainer will let it discharge and recharge it periodically, but you probably won't get any significant current flow for very long. I'm more worried about gas fumes and the potential for an electrical spark. I'm sure the switching inside my chargers is solid state, but they are not certified for hazardous environments. Therefore, on 'Skis that are covered and under a roof, I leave the charger outside of the hull but under the cover. If I have to leave a 'Ski out from underneath the roof where it could get wet, I stick the charger inside the hull somewhere.

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  8. #7
    Good point Steve, that thought has crossed my mind since the storage tray where charger sits is just below gas cap. There is no roof above the lifts, but nothing is stopping me from putting charger under the cover and out of the storage bin. Great idea thanks!

  9. #8
    TimeBandit's Avatar
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    I agree with Steve45 as well. Plus, I'd not feel so safe having a 120v power cord inside or even on top of the craft. Try keeping things out of the hull, out from between the tarp/cover, out of the sun, and dry whenever possible. Here's an example setup I've actually seen :
    1) A couple of "Battery Tender 800" units. Product states: "The interior is completely encapsulated, protected from shock, vibration, and moisture by an electrically insulating, thermally conductive, flame retardant, synthetic epoxy resin compound".
    2) Mounted vertically on the sides of a 4x4 post, and then top that post with a plank of wood or plastic - aka function as an extra shield from direct sun and direct rain spray.
    3) Attached to the DC 2 pin quick connectors were 25' extensions, so that the placement of said post was mounted slightly away from the PWCs.
    4) On the back-side of the 4x4 post was an AC junction box having a covered exterior GFI AC outlet for the two tenders.

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    Click avatar for tech links/info K447's Avatar
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    Quote Originally Posted by TimeBandit View Post
    ... Battery Tender [Waterproof] 800 ...
    A few months ago I discovered the Deltran 800mA Waterproof charger is not fully float voltage compatible with AGM batteries.

    http://greenhulk.net/forums/showthre...=1#post3107021

    I don't think I have seen a temperature compensation voltage curve chart for that model.


  11. #10
    TimeBandit's Avatar
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    I remember that thread. Agreed, for those that want one of the ultimate in tenders, you'd be hard-pressed to find something better than a BatteryMinder.
    Yet don't let NOT owning a BatteryMinder take-away from incorporating a decent tender as part of ones setup. I own no stock-shares in Deltran, the BT-800 is a descent tender for the money, and I'd go out on a limb to say even with it's fixed float voltage, it's not going to short-change an AGM asset. At least no where near the harm of not using a tender at all. BTW, I find it no coincidence that the BT-800 chose a fixed 13.4V float, aka ideal float for 70-80F, thus likely the largest market to target.


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