Portable Battery to run Battery Tender

Discussion in 'Equipment' started by iacamacho75, Jan 14, 2020.

  1. iacamacho75

    iacamacho75 Adventurer Supporter

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    Has anyone used a portable battery to run a battery tender for charging from time to time??? I don’t have an outlet in my garage and would like to top off the battery every week or so... any suggestions? Tks
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  2. lipsee

    lipsee Been here awhile

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    Not sure if this is the same thing,,but I bought a Noco starter GB70 pack with a 12v output... My idea was to run my heater gear whilst on smalll bikes that would not support that kind of currant... Not sure if you can charge from it thou...
    #2
  3. Panther6834

    Panther6834 Adventurer

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    You want to use a battery to power a charger, so you can charge a battery. Honestly, this just doesn't make sense. Why not just but a really long extension cord, and run that from inside the house, to the garage?

    A 100ft outdoor extension cord costs as little as $25-35 on Amazon...and, if that's not long enough, you can always buy two. If you're winning to spend more money, you can pick up a portable generator for less then $300 (there's quite a few low-power ones in the $200-250 range). Best of all, a portable generator would have other uses.
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  4. CaseyJones

    CaseyJones Ridin' that train

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    For the hassle of stringing extension cords...and the risk, and maybe it's a public area...it would be easier to just take out the battery and keep the tender on in your office or utility room.
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  5. squish

    squish Out of the office.

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    There's a basic flaw in the system.
    Any time you convert from DC to AC and then back to D.C. you lose juice. It gets consumed by the process.

    Now I am not an EE but it seems like you should be able to rig up or even find a DC charge controller that would get rid of the needless DC->AC->DC, and just send a trickle charge from the bigger battery into the smaller battery. Which would give you more power to charge the battery with.

    Another option is a solar panel with a charge controller on it.

    That said, I have done what the OP asked.
    I have a battery bank on my RV and I plugged my battery trickle charger up to my inverter and charged the bike battery, from the coach batteries, but really it was charging from the roof mounted solar panel, it just happened to go through the coach battery bank and charge controller and D.C. To AC inverter and then into the trickle charger where it was switched back to D.C.
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  6. JensEskildsen

    JensEskildsen Long timer

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    Theres something wrong if you need to top up the battery on a weekly basis. It should only discharge 1-5% a month, depending on the type ect. + whatever parasittic draw from the bike.
    If the charging system is working, and battery is in good order, you should be able to let the bike sit for a couple months no problem.
    But a charger on it every few months, or before you head out for the next ride, whichever comes first.
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  7. Yinzer Moto

    Yinzer Moto Long timer Supporter

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  8. worwig

    worwig Long timer

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    I put a small solar panel, with a charge controller, on my building with no electric. Works great to top off the bike and tractor battery.
    Do NOT use a plain panel without a charge controller. Even the small panels will eventually damage the battery.

    As to your charge a battery from a battery. I tow a small trailer with my bike. In the trailer, I have a spare motorcycle battery in the trailer. I use it to charge my phones and tablets when camping. I wanted to charge the trailer battery from the motorcycle battery, when towing. Because of wiring losses and such, I put in a simple voltage boast converter. So no matter what the wiring voltage is, it is boasted to 14.4 volts to charge the camper. That simple device and a large battery would do what you are wanting, BUT in your case you would need a timer or such, since you don't want to kill the source battery. It would get messy. Think about the solar panel.
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  9. CaseyJones

    CaseyJones Ridin' that train

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    Another option, requiring far less attention, is to just get a jump starter, and use that when starting after a long shutdown.

    Then go for a twenty-minute ride. The depletion-over-time on the battery is recovered; and of course there wasn't the deep discharge by cranking it.

    I get the satisfaction of hooking up an elaborate new system in, that solves an ongoing problem; but this doesn't sound practical.
    #9
  10. iacamacho75

    iacamacho75 Adventurer Supporter

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    Im in a condo building with no access to a 120V outlet. And obviously wont take out the bikes battery everytime.
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  11. iacamacho75

    iacamacho75 Adventurer Supporter

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    i was thinking of a portable Battery such as the one in the picture, to top off the bikes battery every week or so... my garage in underground with concrete slab and cant access solar panel if installed. Was wondering if a device like this would be ok to run a battery tender for 8-10 hours to top off battery

    41FF97BC-B601-4DEB-B0F6-DEF6BB1A2F07.png 41FF97BC-B601-4DEB-B0F6-DEF6BB1A2F07.png
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  12. szurszewski

    szurszewski Long timer

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    That should work fine.

    but why do you need to top the battery off every week or so? If your battery is draining too low to start from a week - or even a few weeks - you have a problem of some kind. If you’re not riding for a long enough time to draw down a good battery (should be months) then removing or at least disconnecting the battery makes more sense.
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  13. iacamacho75

    iacamacho75 Adventurer Supporter

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    My experience with batteries is that they have optimum performance and lasts yeti most when you keep them as fully charged as possible..... riding the bike in city traffic for a few minutes rarely tops it off.... its preventive...
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  14. szurszewski

    szurszewski Long timer

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    If that’s the case you just need a longer route to ride ;)
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  15. iacamacho75

    iacamacho75 Adventurer Supporter

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    Live in Miami... the most exiting place to ride LOL
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  16. squish

    squish Out of the office.

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    Seems like buying a deepcycle 12vdc battery and the dc to dc charger would be the way to go. And much cheaper over buying one of those power pack kits that are the rage currently. Plus dc to dc charging is much more efficient
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  17. szurszewski

    szurszewski Long timer

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    Ok - that’s a fair point. Better solution then: instead of buying that fancy battery thing (though that might also be nice to have in a hurricane or other power outage), once a week you ride down to homestead and eat at Yardee Spice, and then send me pictures of your food and tell me how good it was so I can live vicariously through you. Depending on where you are should be at least a 90 minute round trip so your battery will be all charged up when you get back.
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  18. iacamacho75

    iacamacho75 Adventurer Supporter

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    Word taken.... will send pic when i visit . Tks
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  19. worwig

    worwig Long timer

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    You never mentioned of solar is an option. That would still be my solution, if it is possible.

    That power box you show is 240watt/hours. The bike lead acid battery is likely about 200watt/hours. No a good idea to try to fully charge it is dead. But, normally lead acid loses about 1% per day. So say every two weeks, loses 14%, or 28 watt/hours. So yea, it should work well for topping it off. But you will need to baby sit it, connect it, disconnect it, keep the portable box charged, etc.

    I don't care for lithium motorcycle batteries, but if you had a lithium iron motorcycle battery, then just install a disconnect on the battery, that would solve it also. Lithium has almost no self discharge, and it is not bothered by sitting around half charged like lead acid. Just make sure you disconnect it from the bike when sitting so the bike does not kill it.
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  20. worwig

    worwig Long timer

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    Is there a garage door opener or even a light bulb you can tap into?
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