2 Batteries on one tender?

Discussion in 'The Garage' started by tomdubz, Nov 4, 2019.

  1. tomdubz

    tomdubz getting there Supporter

    Joined:
    Jun 29, 2010
    Oddometer:
    1,224
    Location:
    4 Cornerstan
    I've got a Battery Tender Plus single output charger.

    The two batteries in play:
    YTZ14S 12V 11.2Ah
    ES5LBS 12V 4.5Ah

    They're both AGM

    I'm thinking about using this thing but I have no idea if it's effectively series or parallel:
    [​IMG]
    Pretty sure I need parallel per the Battery Tender FAQ page here: http://www.batterytender.com/faq/products

    Someone tell me I'm an idiot.
    #1
  2. Jack90210

    Jack90210 quia ego nominor leo

    Joined:
    Oct 11, 2004
    Oddometer:
    16,431
    Location:
    :jack
    That would almost have to be parallel.

    As best as I can tell, the larger battery is going to require a longer charge period for a given amount of discharge (lowered voltage), and what the charger will "see" as it cycles charge current on and off won't be ideal for either battery.
    #2
    SmittyBlackstone likes this.
  3. RetiredandRiding

    RetiredandRiding Retired to Ride Supporter

    Joined:
    May 22, 2015
    Oddometer:
    1,405
    Location:
    Da Lat, Vietnam
    Bad idea. From the site you listed:

    "The nominal battery voltages (i.e. 12V, 8V, 6V, 4V, 2V) must be the same on each battery, and the batteries must be the same lead acid type (flooded, AGM, or Gel Cell). Also the batteries must be close to the same size in terms of amp hour capacity, and they must be close to the same level of discharge. It is also a good idea that the batteries be approximately the same age and that they be in relatively the same general condition."

    11.2 and 4.5 are NOT "close to the same size..." , so you CANNOT charge them together.

    The cable is, I believe, best used for accessories from the SAE plug on your bike.

    There's no need to keep a battery on the tender 24/7. If you switch it from one bike to the other every week of so, you should be fine.

    Or buy another tender.
    #3
  4. dtysdalx2

    dtysdalx2 Knowledge is horsepower

    Joined:
    Aug 1, 2004
    Oddometer:
    22,593
    Location:
    Moneyapolis, MN
    I didn't want to start a new thread but...

    Neighbor's car dead this morning. Put my charger on it and it went haywire. Volt meter said 1 Volt? Really dead.

    Anyway after a while I though it was a goner but after a bit and jump start from another vehicle the 13V came back???

    It that even possible?
    #4
  5. RetiredandRiding

    RetiredandRiding Retired to Ride Supporter

    Joined:
    May 22, 2015
    Oddometer:
    1,405
    Location:
    Da Lat, Vietnam
    Better to spend an extra 30 seconds to start a new post than hijack one that's UNRELATED.
    #5
    CopyCat, sieg and Boatman like this.
  6. tomdubz

    tomdubz getting there Supporter

    Joined:
    Jun 29, 2010
    Oddometer:
    1,224
    Location:
    4 Cornerstan
    Derp. Dern reading comprehension fails me again. Was only seeing what I wanted it to do. Thanks!
    #6
  7. timeOday

    timeOday Long timer

    Joined:
    Jun 20, 2008
    Oddometer:
    2,860
    Location:
    New Mexico
    When I got injured and couldn't ride for quite a while I made a cable so I could put 5 bikes on one charger. The issue I encountered was making sure the batteries are at very nearly the same voltage BEFORE you rig them together. If you fail to do that, fuses will blow. I would not attempt to recharge or fast-charge batteries this way at all. But if they are already charged, just to hold them at 13v, personally would probably do it again.

    (Actually I have mostly switched to Lithium batteries now, they will hold a charge much longer and don't need to be put on a tender.)
    #7
  8. MacNoob

    MacNoob piney fresh

    Joined:
    Jun 2, 2010
    Oddometer:
    2,664
    Location:
    The mosquito-y Center of Canada
    Tried this one time, ended up with 2 dry dead batteries. YMMV but I'm not doing it again.
    #8
  9. flei

    flei cycletherapist

    Joined:
    Apr 1, 2013
    Oddometer:
    9,424
    Location:
    Western Mass.
    IMO you are not an idiot. For several years I've used this to charge 2 batteries from my Battery Minder brand maintainer. It has worked just fine. https://www.amazon.com/BatteryMINDer-SmarTECHnology-Multiple-Battery-Connector/dp/B00LHVUGXM

    I don't know if it makes a difference what maintainer you use, but I use this solar one as my bikes/atv/mower are stored in a remote shed (https://www.amazon.com/BatteryMINDe...ller-Desulfator/dp/B0000CEWWB?ref_=ast_sto_dp)
    #9
  10. bwringer

    bwringer Gimpy, Yet Alacritous

    Joined:
    Jan 22, 2008
    Oddometer:
    3,018
    Location:
    Indianapolis
    Yep, this. Don't parallel two batteries on one tender. And swapping every month would be plenty.

    And actually, all you really need is a few hours on the tender once a month or so. This is similar to what I do; I hate leaving tenders hooked up. Too many burned out garages from that. I normally only leave them hooked up when I'm around for a few hours doing something else. Once the light turns green, disconnect and ignore for four or five weeks.
    #10
  11. tomdubz

    tomdubz getting there Supporter

    Joined:
    Jun 29, 2010
    Oddometer:
    1,224
    Location:
    4 Cornerstan
    #11
  12. RetiredandRiding

    RetiredandRiding Retired to Ride Supporter

    Joined:
    May 22, 2015
    Oddometer:
    1,405
    Location:
    Da Lat, Vietnam
    #12