JohnK
03-11-2022, 10:57 PM
I have a '67 Mustang that has been parked in a storage unit for the last several months. We moved recently and I now have a larger garage, so I decided to go get the Mustang out of storage and bring it home. I wasn't sure what sort of condition the battery would be in, so I went to the storage unit yesterday and removed the battery and brought it home to put on a charger overnight. The battery is a dark-case Optima red top 34R that was purchased in early 2020, so it's not that old. I know there's lots of "love" for Optimas on this forum but they've always performed well for me. Prior to being stored, the Mustang had been driven pretty regularly so other than this one period where it sat for several months it had not been previously neglected.
I brought the battery home yesterday and put it on an Optimate 6 (https://optimate1.com/om6/) smart charger (forgot to check voltage before putting it on the charger). When I first connected the battery it sensed that it needed to run through the desulfate program and then went into the regular charging cycle. Roughly 20 hours later I went out to check on the battery today and the charger was still indicating that it was charging at its maximum output, i.e., the battery was not fully charged yet. Not surprising given how long it had sat. I disconnected it and checked voltage and it was at 12.5V so I figured that even though it wasn't fully charged it was probably good enough to start the car and get it home. It was a little warm to the touch but I didn't think much of it. I took it to the storage unit and installed it, and the car fired right up. In fact, I was pleasantly surprised that the starter sounded much stronger than I expected. Being a nice sunny day, I put the top down and went out to run some errands. After several stops around town, I went by the post office, and when I parked the car I heard a faint hissing sound. Oh great... I thought I had a small leak in a radiator hose. I popped the hood and much to my dismay the hissing sound was coming from the battery. One corner of the case near the negative terminal was bulging and there was steam coming out of the vent port and the corner of the case. I let it cool until the hissing stopped and got home as quickly as I could (only a mile or so). As soon as I got home I removed the battery from the car and set it outside (I'd rather not burn the garage down). It was very hot to the touch and still hissing and venting steam. Here's a photo of what it looked like. I'm pretty certain that, had I not heard the hissing and had driven for any extended length of time, this would have ended very badly. My best guess is that the alternator (upgraded 100A PowerMaster) sensed that the battery was still low and fed it max. amperage to charge it.
A little googling reveals that this is not an uncommon failure mode for Optimas (both yellow and red top). I know that a lot of folks on the forum park their "fun" cars for months at a time during the winter - sometimes with, sometimes without a trickle charger. Be aware that a battery that is discharged may still be able to start your car, but your car's alternator is not the best way to recharge a deeply discharged battery. Definitely best to keep the battery on a trickle charger during the winter, or at least fully charge it on a smart charger before re-installing it in the car.
https://thefactoryfiveforum.com/attachment.php?attachmentid=163816&d=1647052034
I brought the battery home yesterday and put it on an Optimate 6 (https://optimate1.com/om6/) smart charger (forgot to check voltage before putting it on the charger). When I first connected the battery it sensed that it needed to run through the desulfate program and then went into the regular charging cycle. Roughly 20 hours later I went out to check on the battery today and the charger was still indicating that it was charging at its maximum output, i.e., the battery was not fully charged yet. Not surprising given how long it had sat. I disconnected it and checked voltage and it was at 12.5V so I figured that even though it wasn't fully charged it was probably good enough to start the car and get it home. It was a little warm to the touch but I didn't think much of it. I took it to the storage unit and installed it, and the car fired right up. In fact, I was pleasantly surprised that the starter sounded much stronger than I expected. Being a nice sunny day, I put the top down and went out to run some errands. After several stops around town, I went by the post office, and when I parked the car I heard a faint hissing sound. Oh great... I thought I had a small leak in a radiator hose. I popped the hood and much to my dismay the hissing sound was coming from the battery. One corner of the case near the negative terminal was bulging and there was steam coming out of the vent port and the corner of the case. I let it cool until the hissing stopped and got home as quickly as I could (only a mile or so). As soon as I got home I removed the battery from the car and set it outside (I'd rather not burn the garage down). It was very hot to the touch and still hissing and venting steam. Here's a photo of what it looked like. I'm pretty certain that, had I not heard the hissing and had driven for any extended length of time, this would have ended very badly. My best guess is that the alternator (upgraded 100A PowerMaster) sensed that the battery was still low and fed it max. amperage to charge it.
A little googling reveals that this is not an uncommon failure mode for Optimas (both yellow and red top). I know that a lot of folks on the forum park their "fun" cars for months at a time during the winter - sometimes with, sometimes without a trickle charger. Be aware that a battery that is discharged may still be able to start your car, but your car's alternator is not the best way to recharge a deeply discharged battery. Definitely best to keep the battery on a trickle charger during the winter, or at least fully charge it on a smart charger before re-installing it in the car.
https://thefactoryfiveforum.com/attachment.php?attachmentid=163816&d=1647052034