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12 v battery changed polarity overnight ?

Mikey NY

Registered
Last Subscription Date
02/28/2016
I have a 12 volt battery in a walk behind tractor. It is a small lawn mower type battery that was bought last november and installed in a david Bradley walk behind tractor with an 8 hp electric start motor. It worked fine when it was installed. It had sat for about 3 months and then the cover blew off of it and it rained for several days so it got soaked. I went out to start it a few days ago and the starter was spinning but not engaging. I discovered the starter was turning backwards. the battery was almost fully charged. when I put a meter on it ( I used several meters) the polarity was reversed. In all my yrs of tinkering with cars and stuff I have never seen this happen. So what do you all think? What is happening here?
 

Tracy T

Subscriber
Last Subscription Date
07/16/2019
I have seen it happen before once, and like you have no idea what so ever why or how.
 

Fred Van Hook

Sponsor
Age
70
Last Subscription Date
11/05/2019
Quote: Some regard this as a myth while others have noted that when it does happen the battery is only of limited use as the current flows are now acting against the ways the the internal plates were designed to operate. As such it is not possible to fully charge the battery and the overall lifespan is dramatically reduced.

 

Vanman

Subscriber
Last Subscription Date
07/10/2019
It can certainly happen if one were to connect a charger backwards to a heavily discharged battery.

While the plates are different in a charged battery, lead and lead oxide, both plates become the same, lead sulphate, as it discharges.

I don’t see this happening spontaneously though.

Keith
 

Ronald E. McClellan

Subscriber
Last Subscription Date
01/05/2020
Hook it up to something to drain the battery to total dead. A couple of auto head lights will do it. Then recharge with correct polarity. It may take a couple of times to get the plates back to normal. Ron
 

MColopy

Subscriber
Last Subscription Date
12/14/2019
I have seen this happen when a fully discharged battery is hooked up backwards on a charger but to happen to one just sitting there I would have to have an engineer explain that. I would think we would have someone here that could explain this, come on and help us out.
 

Monsonmotors

Subscriber
Last Subscription Date
02/22/2020
I have seen that once. MUCH more likely it was fully discharged and then recharged backwards.
It is now useless. Don’t trust it. In our scenario we were able to kill the battery completely and recharge correctly. Much safer to get another and start over.
Once the new battery arrives it’s “all hands on deck” step by step recheck both your charger and application connections to the last detail otherwise you’ll do it again.
 

Mikey NY

Registered
Last Subscription Date
02/28/2016
thanks for the info guys. I did not put a charger on since it had 11.9 volts already. and I am not really sure if it changed overnight, I guess it could have happened over time. I have read that it is impossible to happen like that. I was thinking that because it had got soaked along with the solenoid, that something odd happened. I have disconnected it and set outside to be safe.
 

Power

Registered
Is it possible that something is wrong with the David Bradley charging circuit, and the last time it ran, it reverse charged the battery?
 

Pete Deets

Subscriber
Last Subscription Date
01/01/2020
My guess (and guess only as it is worth what you've paid for it) is while the cover was off & the unit soaked it discharged the battery DEAD and after it dried it floated back up to a surface charge of the wrong polarity. It is junk and should be handled carefully - as few physical shocks as possible. The plates may be so badly sulphated that jarring it around could cause an internal short and then much excitement. YMMV...................PD
 

Pete Deets

Subscriber
Last Subscription Date
01/01/2020
What I didn't say very well is I think the rain may have caused something to put a load or partial short on the battery and when things dried out the partial short went away...........:bonk:.............PD
 

dkamp

eMail NOT Working
The cool thing about old electromagnetics, is that they are very frequently 'polarity neutral'... that is, they're based on coils and polepieces, and current flow in one direction appears no different than the other... as long as there's no residual magnetism in any of them. Likewise, the field and armature of the electric motor are connected such that direction will NOT be altered by polarity. This is why, when someone takes an old 6v positive ground tractor, and plops a 12v negative ground battery in it, hit the button, and it'll fire right up and run fine, as long as it has a magneto or a really strong coil.... of course, when you pull the light switch, they're really bright, and then they blow, but it starts fine.

In your case, the starter turning backwards suggests that your starter is a permanent-magnet-field... OR... the field could still be stuck, and it's trying to crank in generating mode. I've never tried it, but there's a possibility that it COULD.

It probably suffered a stuck voltage regulator cutout contact... and it MAY have reversed it's charge as a result...

But yes, it IS possible, but yes, it makes batteries chemically very angry. I wouldn't expect it to be ready to explode, but I would always err on the side of caution. Connecting a salvaged turn-signal lamp, and discharging it down super-darned flat, then putting a SMALL charger on it (1A or less) with proper polarity and walk away from it for several days (with it someplace that cannot accumulate fumes, nor provide fuel for a fire) to attempt to bring it back up in the proper polarity...

But don't place extremely high expectations on it... that electrolyte can get fussy.

On a side note, I had a boat tied to my dock one summer day. The dock was in a portion of the river where a 'no wake zone' existed, yet some bozo with a 54ft housboat came through 'on plane' (which is to say, he was digging a HUGE hole in the river). It capsized and sunk my boat (and did some damage to the dock, and my neighbors' docks too, and tried to put a dent in a bridge pier and yes, he spent a few days in jail)...

But when I arrived home the next day, I gathered my equipment and dove down to attach lift bags to bring it up to the surface. When I got down there, I heard a little hissing noise. I realized that it was the bilge pump... the automatic switch had floated up, and the little pump was churning away trying to pump the entire Mississippi River out'a that 15ft tri-hull.

Once I got it raised and pumped clear, I unhooked the battery, rinsed off the mud, and placed it in the driveway, and promptly pulled the plugs, rolled the engine over to eject the water, compressed-air the magneto, put it back together and fired it up in a garbage can full of water.

That darned battery survived being submerged 8 feet for two days, running a bilge pump... and I kept that battery in the boat for three more seasons, it worked just fine... never needed even a trickle charge.

So... stranger things have happened. I've also had a seemingly perfect battery blow up in my face due to a tiny fracture in a busbar... so be careful with it.
 

Mikey NY

Registered
Last Subscription Date
02/28/2016
I ran that walk behind tractor this evening without a battery, (it has a pull start also) I see it arcing from under the cowling near the starter. It appears to be arcing from the ignition coil under the cowling down onto the starter casing. It runs just fine, never misses a beat. Maybe the aliens are at it again? I don't think I will put another battery in this one anytime soon. I will just run it like it is.
 
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