Battery Tender - strange thing happened

[Visian]

I've been using these things for years but I can't say I've done what I did before.

I keep my bikes and mowers on the regular old metal-cased Deltran Battery Tenders. All the batteries are AGM.

This strange thing happened to one connected to one of my mowers, but it could have just as easily happened to one of my bikes.

I had to move the mowers, so I unplugged the BTs from the wall and set each on their respective mowers. I left the alligator clamps attached to the batteries. Moved the mowers (didn't start the engines, just pushed them) and things sat there for a few minutes.

Then I needed to move one of the mowers again, and in the process, the alligator clip on the positive terminal made a huge pop, major spark and some smoke. I quickly released both the positive and the ground clips and the positive clip had a good-size chuck burned away from its teeth.

Never seen anything like this happen before. On my bike I use the SAE connectors that are wired directly to the battery. When I ride, I unplug the BT and separate the SAE connector. For starting and using the mowers, I remove the alligator clips and unplug the BT.

Did this happen because I left the thing connected to the battery while it was unplugged?

I am a bit shy to reconnect it, wondering if anyone has expertise?

Ian

 

[20774]

Is there anything in the instructions or online about doing what you did? Basically, is it a no-no to simply unplug the BT from the wall and leave it that way for a long time. Is there a voltage potential back-flow from the battery thru the BT to the AC terminals? Or maybe the backflow into the BT is not intended or designed for and leaving it the way you did for a period of time caused something to fail in the BT?

 

[stooie]

Ian:

I suspect what happened is that while moving the mower for the second time the power terminal of the tender wall plug touched some bare metal on the mower completing the circuit through the mower chassis. As Ohm's Law tells us, I (current) = V (voltage) / R (resistance). Since the resistance through the chassis was near zero, the current headed towards infinity. Hence the fireworks.

Although this is an admittedly rare occurrence, it's safer to disconnect the tender from the battery to preclude the drama. (I'm guessing at this point you don't need me to tell you that.)

You probably didn't do anything to hurt the mower but the tender wiring may have suffered from the episode.

Good luck with it!

 

[Visian]

Ian:

I suspect what happened is that while moving the mower for the second time the power terminal of the tender wall plug touched some bare metal on the mower completing the circuit through the mower chassis. As Ohm's Law tells us, I (current) = V (voltage) / R (resistance). Since the resistance through the chassis was near zero, the current headed towards infinity. Hence the fireworks.

Although this is an admittedly rare occurrence, it's safer to disconnect the tender from the battery to preclude the drama. (I'm guessing at this point you don't need me to tell you that.)

You probably didn't do anything to hurt the mower but the tender wiring may have suffered from the episode.

Good luck with it!

Thanks, Bob. I will always disconnect the BT from the battery first from now on. I'll try using the BT again, and it should be pretty obvious (even to me!) if it's toast.

Ian

 

[Omega Man]

Transformers work in both directions- for the most part.
OM

 

[Visian]

Transformers work in both directions- for the most part.
OM

This never dawned on me. Electrically, I am clueless. On a lot of other things, too!

 

[junkjohn]

Connect battery charger to a battery and see if there is voltage at the wall plug end, while it is unplugged. I think there is.

 

[m_stock10506]

Ian:

I suspect what happened is that while moving the mower for the second time the power terminal of the tender wall plug touched some bare metal on the mower completing the circuit through the mower chassis. As Ohm's Law tells us, I (current) = V (voltage) / R (resistance). Since the resistance through the chassis was near zero, the current headed towards infinity. Hence the fireworks.

Although this is an admittedly rare occurrence, it's safer to disconnect the tender from the battery to preclude the drama. (I'm guessing at this point you don't need me to tell you that.)

You probably didn't do anything to hurt the mower but the tender wiring may have suffered from the episode.

Good luck with it!

While this may be what happened..... my guess is the alligator clip on the mower's positive battery connection moved while the mower was moved and slid into the negative alligator clip or the frame of the grounded mower. Look closely for another electric arc smudge on the mower. I would expect that the BT electronics package inside the case does not allow voltage to flow backwards on the 120v wire to the oultlet.

 

[Visian]

While this may be what happened..... my guess is the alligator clip on the mower's positive battery connection moved while the mower was moved and slid into the negative alligator clip or the frame of the grounded mower. Look closely for another electric arc smudge on the mower. I would expect that the BT electronics package inside the case does not allow voltage to flow backwards on the 120v wire to the oultlet.

This it basically what I thought... and the positive pole and clip were far away from any other metal. The sparking was all at the positive connector, but I am going to give the mower a close look next time I am back up at our barn.

 

[Paul_F]

Ian, why not use the same connector on the mower as you use on the bikes? This works on my mower.

 

[Visian]

Ian, why not use the same connector on the mower as you use on the bikes? This works on my mower.

I'm lazy and have not yet gotten a round tuit. I actually have the SAE connectors sitting there.

 

[azgman]

I would think that a relay or diode would be employed by Deltran to prevent any backflow. I subscribe to the theory that there was positive alligator clip (still connected to the battery anode) to ground contact and that the electro motive force came from the battery independant of the Deltran unit.

 

[rangemaster]

I'm lazy and have not yet gotten a round tuit. I actually have the SAE connectors sitting there.

Here you go...LOL.

Sent from my iPhone using Tapatalk

 

[EUGENE]

I would think that a relay or diode would be employed by Deltran to prevent any backflow. I subscribe to the theory that there was positive alligator clip (still connected to the battery anode) to ground contact and that the electro motive force came from the battery independant of the Deltran unit.

This is correct , a diode is used. From an ex sparky.

 

[junkjohn]

Connect battery charger to a battery and see if there is voltage at the wall plug end, while it is unplugged. I think there is.

I mentioned this to check for a failed diode or relay. He mentioned it as being an old charger.