<div dir="ltr">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? <div><br></div><div>SO</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sat, Feb 15, 2020 at 8:38 AM <<a href="mailto:deanvp@att.net">deanvp@att.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div bgcolor="white" lang="EN-US"><div class="gmail-m_-1681538846691093110WordSection1"><p class="MsoNormal"><span style="color:windowtext">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. <u></u><u></u></span></p><p class="MsoNormal"><span style="color:windowtext"><u></u> <u></u></span></p><p class="MsoNormal"><span style="color:windowtext"><u></u> <u></u></span></p><div><p class="MsoNormal"><span style="color:windowtext">Dean VP<u></u><u></u></span></p><p class="MsoNormal"><span style="color:windowtext">Apache Junction, AZ<u></u><u></u></span></p></div><p class="MsoNormal"><span style="color:windowtext"><u></u> <u></u></span></p><div><div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in"><p class="MsoNormal"><b><span style="color:windowtext">From:</span></b><span style="color:windowtext"> AT <<a href="mailto:at-bounces@lists.antique-tractor.com" target="_blank">at-bounces@lists.antique-tractor.com</a>> <b>On Behalf Of </b>Cecil Bearden<br><b>Sent:</b> Thursday, February 13, 2020 7:37 AM<br><b>To:</b> <a href="mailto:at@lists.antique-tractor.com" target="_blank">at@lists.antique-tractor.com</a><br><b>Subject:</b> Re: [AT] Batteries charged backwards.<u></u><u></u></span></p></div></div><p class="MsoNormal"><u></u> <u></u></p><p>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... <br>I charge my batteries outside for safety. These are sealed batteries. <br>Cecil<u></u><u></u></p><div><p class="MsoNormal">On 2/13/2020 8:28 AM, Stephen Offiler wrote:<u></u><u></u></p></div><blockquote style="margin-top:5pt;margin-bottom:5pt"><div><div><p class="MsoNormal">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.<u></u><u></u></p></div><div><p class="MsoNormal"><u></u> <u></u></p></div><div><p class="MsoNormal">SO<u></u><u></u></p></div><div><p class="MsoNormal"><u></u> <u></u></p></div><p class="MsoNormal"><u></u> <u></u></p><div><div><p class="MsoNormal">On Thu, Feb 13, 2020 at 9:08 AM Thomas Martin <<a href="mailto:tmartin@xtra.co.nz" target="_blank">tmartin@xtra.co.nz</a>> wrote:<u></u><u></u></p></div><blockquote style="border-top:none;border-right:none;border-bottom:none;border-left:1pt solid rgb(204,204,204);padding:0in 0in 0in 6pt;margin-left:4.8pt;margin-right:0in"><div><p>Do you have ADD? The point of this exercise is to reverse the polarity of a battery.<u></u><u></u></p><blockquote style="margin-top:5pt;margin-bottom:5pt"><p class="MsoNormal" style="margin-bottom:12pt">On 13 February 2020 at 23:15 Stephen Offiler <<a href="mailto:soffiler@gmail.com" target="_blank">soffiler@gmail.com</a>> wrote: <u></u><u></u></p><div><p class="MsoNormal">For some actual information on lead-acid charging, try this: <u></u><u></u></p><div><p class="MsoNormal"><u></u> <u></u></p></div><div><p class="MsoNormal"><a href="https://batteryuniversity.com/learn/article/charging_the_lead_acid_battery" target="_blank">https://batteryuniversity.com/learn/article/charging_the_lead_acid_battery</a> <u></u><u></u></p></div><div><p class="MsoNormal"><u></u> <u></u></p></div><div><p class="MsoNormal"><u></u> <u></u></p></div></div><p class="MsoNormal"><u></u> <u></u></p><div><div><p class="MsoNormal">On Thu, Feb 13, 2020 at 3:49 AM Thomas Martin < <a href="mailto:tmartin@xtra.co.nz" target="_blank">tmartin@xtra.co.nz</a>> wrote: <u></u><u></u></p></div><blockquote style="margin-top:5pt;margin-bottom:5pt"><div><p>Hi Dean<u></u><u></u></p><p>After the dead battery is connected to the charged 12v battery in parallel, a battery charger is connected, (the charged battery <u></u><u></u></p><p>is there only to dictate the polarity), and charging can commence. <u></u><u></u></p><p>Tom<u></u><u></u></p><blockquote style="margin-top:5pt;margin-bottom:5pt"><p class="MsoNormal" style="margin-bottom:12pt">On 13 February 2020 at 20:41 <a href="mailto:deanvp@att.net" target="_blank">deanvp@att.net</a> wrote: <u></u><u></u></p><div><p>Tom,<u></u><u></u></p><p> <u></u><u></u></p><p>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?<u></u><u></u></p><p> <u></u><u></u></p><div><p>Dean VP<u></u><u></u></p><p>Apache Junction, AZ<u></u><u></u></p></div><p> <u></u><u></u></p><div><div style="border-right:none;border-bottom:none;border-left:none;border-top:1pt solid rgb(225,225,225);padding:3pt 0in 0in"><p><strong><span style="font-family:Calibri,sans-serif">From:</span></strong> AT <<a href="mailto:at-bounces@lists.antique-tractor.com" target="_blank">at-bounces@lists.antique-tractor.com</a>> <strong><span style="font-family:Calibri,sans-serif">On Behalf Of </span></strong>Thomas Martin<br><strong><span style="font-family:Calibri,sans-serif">Sent:</span></strong> Wednesday, February 12, 2020 12:47 PM<br><strong><span style="font-family:Calibri,sans-serif">To:</span></strong> Antique Tractor Email Discussion Group <<a href="mailto:at@lists.antique-tractor.com" target="_blank">at@lists.antique-tractor.com</a>><br><strong><span style="font-family:Calibri,sans-serif">Subject:</span></strong> Re: [AT] Batteries charged backwards.<u></u><u></u></p></div></div><p> <u></u><u></u></p><p>Stephen<u></u><u></u></p><p>Well it appears you do not understand the difference between connecting in series and parallel.<u></u><u></u></p><p>When you jump start a vehicle, one connects in parallel, the current from the jumper battery does<u></u><u></u></p><p>not have any affect on the the dead battery.<u></u><u></u></p><p>Tom.<u></u><u></u></p><blockquote style="margin-top:5pt;margin-bottom:5pt"><p style="margin-bottom:12pt">On 13 February 2020 at 07:52 Stephen Offiler <<a href="mailto:soffiler@gmail.com" target="_blank">soffiler@gmail.com</a>> wrote:<u></u><u></u></p><div><div><p>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.<u></u><u></u></p><div><p> <u></u><u></u></p></div><div><p>SO<u></u><u></u></p></div><div><p> <u></u><u></u></p></div></div><p> <u></u><u></u></p><div><div><p>On Wed, Feb 12, 2020 at 1:08 PM Thomas Martin < <a href="mailto:tmartin@xtra.co.nz" target="_blank">tmartin@xtra.co.nz</a>> wrote:<u></u><u></u></p></div><blockquote style="margin-top:5pt;margin-bottom:5pt"><div><p>Surely US battery chargers have adjustable amperage?<u></u><u></u></p><p>I thought it was a given that you wouldn't put 50 amps into a dead battery...<u></u><u></u></p><p>Tom<u></u><u></u></p><blockquote style="margin-top:5pt;margin-bottom:5pt"><p style="margin-bottom:12pt">On 13 February 2020 at 03:14 Stephen Offiler < <a href="mailto:soffiler@gmail.com" target="_blank">soffiler@gmail.com</a>> wrote:<u></u><u></u></p><div><p>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.<u></u><u></u></p><div><p> <u></u><u></u></p></div><div><p>SO<u></u><u></u></p></div><div><p> <u></u><u></u></p></div></div><p> <u></u><u></u></p><div><div><p>On Wed, Feb 12, 2020 at 9:08 AM < <a href="mailto:szabelski@wildblue.net" target="_blank">szabelski@wildblue.net</a>> wrote:<u></u><u></u></p></div><blockquote style="margin-top:5pt;margin-bottom:5pt"><p>Cecil, <br><br>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. <br><br>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. <br><br>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. <br><br>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. <br><br>Good luck! <br><br>Carl <br>----- Original Message ----- <br>From: Thomas Martin < <a href="mailto:tmartin@xtra.co.nz" target="_blank">tmartin@xtra.co.nz</a>> <br>To: Antique Tractor Email Discussion Group < <a href="mailto:at@lists.antique-tractor.com" target="_blank">at@lists.antique-tractor.com</a>> <br>Sent: Wed, 12 Feb 2020 00:24:36 -0500 (EST) <br>Subject: Re: [AT] Batteries charged backwards. <br><br>Hi Cecil <br>I consulted a very good friend on the other-side of the isle. <br>Tony is auto-electrician, of vast car, truck & tractor experience. <br>He says you MUST discharge the batteries, separately with a bulb. <br>They need to completely discharged. No measurable voltage. <br>Then one battery at a time needs to be placed in parallel with another <br>fully charged 12v battery, they then need to be connected to a 12v <br>charger... <br><br>Tom <br><br>> On 12 February 2020 at 15:31 Cecil Bearden < <a href="mailto:crbearden@copper.net" target="_blank">crbearden@copper.net</a>> wrote: <br>> <br>> <br>> <br>> > I had 2 group 31 batteries out of the tractor that were completely <br>> > dead. I hooked them up in series and connected my 24Vcharger to them <br>> > as It was handy and I wanted to charge both. After a couple of days I <br>> > checked them and found that I had hooked the charger backwards. I <br>> > hooked a couple of incandescent headlights to drain the battery, but <br>> > after 3 days they won't light up the headlights, but they still have a <br>> > lot of spark when shorted with cables.. A guy at my battery shop said <br>> > I should hook up a 6volt light to them and use that to run them <br>> > down.... 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