[AT] Batteries charged backwards.

Wed Feb 12 17:46:58 PST 2020

Here's how it works, for your information:  All the devices in a
parallel-connected circuit must have the same voltage drop across them.  A
good battery has a solid 12V and change.  A dead battery has little to
nothing.  Connect them in parallel and current must flow until the voltage
drops across each of them are equalized.  Your statement about the jumper
battery having no effect on the dead battery is simply wrong.

SO

On Wed, Feb 12, 2020 at 7:33 PM Thomas Martin <tmartin at xtra.co.nz> wrote:

> Stephen
>
> Well it appears you do not understand the difference between connecting in
> series and parallel.
>
> When you jump start a vehicle, one connects in parallel, the current from
> the jumper battery does
>
> not have any affect  on the the dead battery.
>
> Tom.
>
> On 13 February 2020 at 07:52 Stephen Offiler <soffiler at gmail.com> wrote:
>
> I wouldn't purposely put 50 amps into a totally dead battery if I didn't
> have to, but then we have the example cited by others, the jump-start.
> Who-knows how many amps will flow; limited only by the internal resistance
> of the batteries and the cables & connections.  I don't think many people
> appreciate that a jump-start is actually sort of a hail-Mary maneuver.  If
> you didn't need to get the car/truck/tractor started ASAP, the smart move
> is to charge the battery slowly and correctly.  People are going to chime
> in and say "I've been jump-starting my entire life and never had a
> problem!"  OK.  Me too.  But the issue here is that it's impossible to know
> how much you might have shortened the life of that battery by hitting it
> with that big uncontrolled amperage surge.  In Cecil Bearden's case, he's
> not stuck in a field or a parking lot or whatever. He has the opportunity
> to do it right.  And that definitely does NOT include hitting it with a
> giant surge.
>
> SO
>
>
> On Wed, Feb 12, 2020 at 1:08 PM Thomas Martin < tmartin at xtra.co.nz>
> wrote:
>
> Surely US battery chargers have adjustable amperage?
>
> I thought it was a given that you wouldn't put 50 amps into a dead
> battery...
>
> Tom
>
> On 13 February 2020 at 03:14 Stephen Offiler < soffiler at gmail.com> wrote:
>
> Hold on.  A completely dead 12V battery connected to a good 12V battery is
> going to cause very large current to flow into the dead one. This is not a
> good idea.
>
> SO
>
>
> On Wed, Feb 12, 2020 at 9:08 AM < szabelski at wildblue.net> wrote:
>
> Cecil,
>
> I agree with completely discharging the batteries and then putting the
> batteries in parallel one at a time with a good 12V battery. The batteries
> will try to equalize when in parallel.  When you drain the battery, take
> the load off and let the battery sit for a while, then put the load back on
> and drain some more.
>
> You should use a battery charger that has a trickle charge feature. This
> puts a full charge into the battery at first, then drops down to a small
> charge to top the battery off. You may have to do this several times and
> should leave the charger on for at least one full day. Don’t rush the job.
>
> You can also check that each cell is good by taking a reading between each
> cell. A bad cell will indicate a lower charge then the others. Do this with
> every recharge attempt and note if you’re making any progress.
>
> Don’t know if you’ve ever gone on-line to look for videos on bringing dead
> batteries back to life, but their are some that show how to drain a
> battery, rinse it out, then refill and recharge. They appear to work out
> quite well, but I can’t swear by them since I’ve never done anything like
> this myself.
>
> Good luck!
>
> Carl
> ----- Original Message -----
> From: Thomas Martin < tmartin at xtra.co.nz>
> To: Antique Tractor Email Discussion Group < at at lists.antique-tractor.com>
>
> Sent: Wed, 12 Feb 2020 00:24:36 -0500 (EST)
> Subject: Re: [AT] Batteries charged backwards.
>
> Hi Cecil
> I  consulted a very good friend on the other-side of the isle.
> Tony is auto-electrician, of vast car, truck & tractor experience.
> He says you MUST discharge the batteries, separately with a bulb.
> They need to completely discharged. No measurable voltage.
> Then one battery at a time needs to be placed in parallel with another
> fully charged 12v battery, they then need to be connected to a 12v
> charger...
>
> Tom
>
> > On 12 February 2020 at 15:31 Cecil Bearden < crbearden at copper.net>
> wrote:
> >
> >
> >
> > > I had 2 group 31 batteries out of the tractor that were completely
> > > dead.  I hooked them up in series and connected my 24Vcharger to them
> > > as It was handy and I wanted to charge both.  After a couple of days I
> > > checked them and found that I had hooked the charger backwards.  I
> > > hooked a couple of incandescent headlights to drain the battery, but
> > > after 3 days they won't light up the headlights, but they still have a
> > > lot of spark when shorted with cables..  A guy at my battery shop said
> > > I should hook up a 6volt light to them and use that to run them
> > > down....  At $100/ea, I need to try to save these...
> > > Cecil
> > _______________________________________________
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