[AT] Batteries charged backwards.

Sat Feb 15 06:18:39 PST 2020

Mathematically correct, but bear in mind the entire explanation is
predicated upon your stated assumption, that both 6V and 12V lamps are
rated at the same wattage.  I agree, and in fact I mentioned this myself,
somewhere wayyyyy up there in this thread.   Also, if you have two of the
12V lamps in parallel (which I believe Cecil mentioned back there at square
One) that's going to do the same thing, double the current draw.  Which
option is easier depends on what you have laying around:  do you have a
couple of 12V headlamps, or do you have a single 6V lamp that is rated a
similar wattage as one of those?

SO

On Sat, Feb 15, 2020 at 8:38 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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