[AT] Batteries charged backwards.

Sat Feb 15 07:35:05 PST 2020

In regards to light bulbs used as resistors, something we've been avoiding
is the non-linear resistance of them. As the light is heated (to the point
of incandescence), it goes higher in resistance. As it gets dim, the
resistance drops... significantly. For the large portion of the discharge,
the battery voltage will be high (say 12 volts or so) and the resistance of
the light will be higher. As it drops to a few volts and the light gets
dimmer, the resistance drops and the current load increases a bit. Not a
big deal in the overall discharge rate or time; I leave it on a couple days
and the battery is pretty well discharged at this point. Reversing the
charger (mine is an old transformer based one with a steady voltage output)
shows very little current upon initial connection and it takes several
hours to develop enough internal resistance to cause significant current
flow.
As Dean points out, it takes quite a while to get to true zero but the
light bulb resistance curve seems to accelerate this discharge. I consider
battery "restoration" a "hail Mary" process but it sometimes works well
enough to pay off, sorrying about the finer details of hitting something
with a hammer isn't always necessary. As far as I'm concerned, when I try
"restoring" a battery, I have nothing to loose because it's usually dead
already. When it DOES work I put the battery on my new restorer/charger.
I've had decent luck extending battery life with that recently too.
Ken in AZ

On Sat, Feb 15, 2020 at 7:48 AM <deanvp at att.net> wrote:

> Cecil, let me try to explain why going to the 6v light helps discharge the
> battery faster.  I think your statement of “…. would not discharge the
> battery” should really be phrased as it takes too long to discharge the
> battery.  Lets assume that the 12V lamp and the 6 V lamp are designed to
> produce 60 Watts.  The 12V lamp then uses 5 Amps but the 6V lamp uses 10
> Amps to produce the same power. So the resistance of the 6V lamp will be
> half of the 12V lamp.  Or looking at it another way, the resistance of the
> 12V lamp is 2.5 ohms and the 6V lamp is 1.25 ohms.   Now lets assume the 12
> V battery has been discharged to 1.25 volts and needs to be pulled down
> further.   The 12 V lamp will only draw a ½ Amp and slowly draw less but
> the 6V lamp will draw 1 Amp initially and slowly get less. The 6 Volt lamp
> will discharge the battery twice as fast at this lower voltage which one
> could not do at the 12V starting voltage because it would burn out the 6V
> lamp. As the battery discharges a lower resistance is needed to keep the
> discharge rate at a reasonable rate. As the battery voltage drops  the
> discharge rate drops with it unless the attached resistance is lower. A 12
> V lamp would take much longer to fully discharge the battery. That is why
> the 6V lamp is used after the battery has dropped below 6V.  Just plain old
> math.  It takes a really long time to get to a true “0” V.  It just takes
> longer with a 12V Lamp vs a 6V lamp.
>
>
>
>
>
> Dean VP
>
> Apache Junction, AZ
>
>
>
> *From:* AT <at-bounces at lists.antique-tractor.com> *On Behalf Of *Cecil
> Bearden
> *Sent:* Thursday, February 13, 2020 7:37 AM
> *To:* at at lists.antique-tractor.com
> *Subject:* Re: [AT] Batteries charged backwards.
>
>
>
> The problem I cannot understand is why,  when I connected 2 incandescent
> headlights in parallel to the battery it would not discharge the battery
> completely.   My battery supplier told me to then use a 6 volt light.  I
> have seriously thought about just hooking both in series and then using
> them as power for arc welding.  A welding rod would discharge them quickly
> and completely.  Welding can be done using batteries as power...
> I charge my batteries outside for safety.  These are sealed batteries.
> Cecil
>
> On 2/13/2020 8:28 AM, Stephen Offiler wrote:
>
> I do not have ADD, although I am starting to wonder what personal issues
> you might have, Thomas.  And no, the point of this exercise is not to
> reverse the polarity,  The point is to make the best possible attempt to
> recover two batteries that have been accidentally reverse-charged.  That
> involves much more than reversing the polarity.  There's a right way and a
> lot of wrong ways to tackle each of the steps.  Discharge.  Repolarize.
> Recharge.
>
>
>
> SO
>
>
>
>
>
> On Thu, Feb 13, 2020 at 9:08 AM Thomas Martin <tmartin at xtra.co.nz> wrote:
>
> Do you have ADD? The point of this exercise is to reverse the polarity of
> a battery.
>
> On 13 February 2020 at 23:15 Stephen Offiler <soffiler at gmail.com> wrote:
>
> For some actual information on lead-acid charging, try this:
>
>
>
> https://batteryuniversity.com/learn/article/charging_the_lead_acid_battery
>
>
>
>
>
>
>
> On Thu, Feb 13, 2020 at 3:49 AM Thomas Martin < tmartin at xtra.co.nz>
> wrote:
>
> Hi Dean
>
> After the dead battery is connected to the charged 12v battery in
> parallel, a battery charger is connected, (the charged battery
>
> is there only to dictate the polarity), and charging can commence.
>
> Tom
>
> On 13 February 2020 at 20:41 deanvp at att.net wrote:
>
> Tom,
>
>
>
> Could you explain this a little further. If the current from the jumper
> battery does not have any effect(affect) on the dead battery how does it
> charge it up?
>
>
>
> Dean VP
>
> Apache Junction, AZ
>
>
>
> *From:* AT <at-bounces at lists.antique-tractor.com> *On Behalf Of *Thomas
> Martin
> *Sent:* Wednesday, February 12, 2020 12:47 PM
> *To:* Antique Tractor Email Discussion Group <at at lists.antique-tractor.com
> >
> *Subject:* Re: [AT] Batteries charged backwards.
>
>
>
> 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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