How to recharge dual battery?

Discussion in 'Trucks and Trailers' started by victor_4488, Dec 10, 2009.

  1. victor_4488

    victor_4488 LawnSite Member
    Messages: 5

    I have a 2005 Isuzu NQR box truck. The two batteries are connected together. The batteries are low because I have to jump-start to get it going. I bought a PEAK 2-amp battery charger that auto-senses when the battery is fully charged and switches to trickle.
    The problem is that the charger thinks that the batteries are fully charged because there are 2 batteries... so it doesn't charge... just trickles.

    How can I charge these two batteries without removing them from the truck?

    Can I use a dual-bank charger (like a Deltran Battery Tender) and connect each battery to a seperate bank of the charger or will this not work because the two batteries are wired together?

    I read somewhere that there could be a "bridge switch" on the cable connecting the two batteries that I could flip to set the 2 batteries into parallel wiring... couldn't find such a switch.

    Can anyone help? I'm sure someone has had a need to charge a dual-battery setup on a truck/boat/RV?

    Thanks in advance!
  2. srl28

    srl28 LawnSite Bronze Member
    Messages: 1,177

    May seem like a dumb question but why cant you charge them one at a time? Disconnect the line that connects the two so there isnt a current between them that would trigger your charge to read theres enough battery power, and just charge them one at a time. When theyre all charge up properly just re connect the lines and you should be good to go, no?
  3. victor_4488

    victor_4488 LawnSite Member
    Messages: 5

    The reason that I'd rather not disconnect is because I only use the truck on the weekends. During the weekdays, I keep the truck in our fenced-off lot out back at night and move it to a streetside location during the day for advertising/visibility reasons.

    Each time I start the truck, the starter battery is hit with about a 10% loss of charge to get the engine cranking. Driving the truck 300 feet from the back to the front is not enough to recharge the battery and recover the 10% loss. Over the span of 5 days of moving back to front and front to back, the battery is dead when I really need it at its fullest on the weekends.

    What I'd like to do is plug it in on Thursday while it is sitting street-side so that it's nice and juiced for our big weekends. It'd be impractical to have to remove all of the protective covers to get to the wiring and unbolt it each week... possible, but I'd rather not risk a shock/short each week...

    It'd be nice just to prewire the leads and do a quick-connect to the charger each Thursday.

    I was thinking that I could wire a couple switches between each battery and flip the two switches to break the connection between the batteries when I needed to do a recharge... such a pain, but it's a possibility.

    Anyone have luck with those solar chargers?
  4. victor_4488

    victor_4488 LawnSite Member
    Messages: 5

  5. wellbuilt

    wellbuilt LawnSite Senior Member
    Messages: 275

    I don't know why the charger wont work the same way the truck draws juice from the battery's ?
    2 amp is a trickle charger.
    You should be able to hook one charger lead to the pos + terminal and the other Neg - lead to the frame of the truck .
    It sounds like you need new battery's .
    You should be able to start the truck more then 15 or 20 times .
    I would try equalising the battery's.
    On a warm morning leave your lites on and kill the battery's dead .
    Then charge them with a 10 amp charger all night .
    Kill the battery's dead and charge them 3 times If the battery's die again get new battery's . John
  6. hondarancher4435

    hondarancher4435 LawnSite Senior Member
    Messages: 307

    You said you bought a 2-amp charger and say it is only trickle charging the batteries well 2 amp on those big batteries is like a trickle charge and will take a minimum of 12 hours to charge them.

    The way i see it go get yourself a nice charger/starter with at least 200 amps of starting power. Throw that on there and it will start right up.

    Or if you don't want to get that put a battery maintainer on them and it will keep them at peak power at all times.
  7. Gravel Rat

    Gravel Rat LawnSite Fanatic
    Messages: 9,544

    You don't want to use a trickle charger they are not good for the batteries. Get a good battery charger that has a crank setting and puts out a good charge. Once the batteries are charged use a solar charger to keep the batteries up.
  8. jbturf

    jbturf LawnSite Bronze Member
    Messages: 1,502

    how about a remote start system,
    some of these can be programmed to
    start and run the vehicle for 20-30 minutes,
    primarily to heat or cool or keep the engine warm,
    but in your case would keep the batteries charges,
    considering your electrical system is all functioning properly to
    begin with
  9. unkownfl

    unkownfl LawnSite Gold Member
    Messages: 3,837

    You don't want to jump start the truck. It is not very nice on the glow plugs. Take the positive of one battery and connect it to the charger and on the opposite battery connect the negative of the charger. You need a amp gauge and see whats drawing the batteries down or drive the truck to the store and disconnect the batteries and have them test them.
  10. PROCUT1

    PROCUT1 LawnSite Platinum Member
    from TN
    Messages: 4,891

    Any reason you cant just let it run for 5 minutes when you move it?

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