Sillyputty
Solar Enthusiast
- Joined
- Jul 21, 2020
- Messages
- 188
An update on my helicoil adventures: I got in on a Michael B. Caro battery group buy a while back, and the 4 - 280AH cells arrived dented, etc. To his credit, at that time Michael was prompt in contacting the supplier and ultimately giving me a full refund. At that time the cells were tapped for the shorter bolts which on most of the cells stripped out during assembly, even using a torque wrench to specs, so I decided to tap and install helicoils and studs on the ones that were stripping out, which was a majority.
Following the methods here, all the re-threaded terminals worked out fine, and the battery was in service in my camp trailer for a few seasons, along mostly bumpy gravel roads. Recently however I noticed a cell that was intermittently showing ~500mv fluctuation from the others, that would even out when the terminals were tightened. Eventually the terminal bolt stripped and wouldn't remain tight enough. This was on one of the untapped and un-helicoiled terminals, so having had such good luck with the previous terminal gave me confidence in drilling and tapping this one as well.
Unfortunately, in the end the the drill bit ended up grabbing into the aluminum, at very close to the depth I'd previous used with no problems, with the following results:
The good news: Nothing caught on fire. & 911 was prompt. Once the drill bit broke through into the internal part of the cell there were a very few sparks and a small candle-sized flame at the hole, which extinguished easily just blowing it out. The cell started slowly out-gassing, increasing in speed and intensity after 30 seconds or so, billowing huge amounts of smoke straight up like a mini-volcano and completely filling the trailer in moments. You can see the black soot on the ceiling in one of the pics. I sprayed the battery with a fire extinguisher even though there were no flames apparent by then, and after the smoke stopped billowing out, the fire dept. donned masks and safely removed the battery from the trailer.
The melamine did get charred near the offending cell, while the fiberglass (?) reinforced silicone mats I used between the cells held up fine. The bottom of the battery box beneath the damaged cell did partially melt through, but thankfully did little damage to the trailer flooring. The damaged cell's temperature after being removed and sitting for several minutes was ~195 F with the adjoining cells less than 100 F.
Another good thing: the damaged cell did exactly as described on YouTube when damaged this way: lots of very hazardous outgassing and smoke, but with no fire or explosion.
All in all I got off lightly with a smoked-out, stinky trailer, a now-unusable battery that, even though it cost me nothing, ended up providing a harrowing learning experience and lessons for the future: 1) Probably don't drill into the aluminum cell terminals. Sure, 6 times it may work perfectly, but the odds of it going wrong outweigh the benefits, and 2) If you do decide to drill and tap them, remove the battery from the trailer and separate the cells from each other and do the drilling in a safe, clear area (outside would be ideal) with proper safety and fire suppression equipment on hand; there's much less potential for collateral damage if things do go wrong.
Thanks for all the help and input from all the contributors on here - I'd not have learned how to to any of this properly nor known what to do in the event something went wrong without all your input.
Stay safe!
Following the methods here, all the re-threaded terminals worked out fine, and the battery was in service in my camp trailer for a few seasons, along mostly bumpy gravel roads. Recently however I noticed a cell that was intermittently showing ~500mv fluctuation from the others, that would even out when the terminals were tightened. Eventually the terminal bolt stripped and wouldn't remain tight enough. This was on one of the untapped and un-helicoiled terminals, so having had such good luck with the previous terminal gave me confidence in drilling and tapping this one as well.
Unfortunately, in the end the the drill bit ended up grabbing into the aluminum, at very close to the depth I'd previous used with no problems, with the following results:
The good news: Nothing caught on fire. & 911 was prompt. Once the drill bit broke through into the internal part of the cell there were a very few sparks and a small candle-sized flame at the hole, which extinguished easily just blowing it out. The cell started slowly out-gassing, increasing in speed and intensity after 30 seconds or so, billowing huge amounts of smoke straight up like a mini-volcano and completely filling the trailer in moments. You can see the black soot on the ceiling in one of the pics. I sprayed the battery with a fire extinguisher even though there were no flames apparent by then, and after the smoke stopped billowing out, the fire dept. donned masks and safely removed the battery from the trailer.
The melamine did get charred near the offending cell, while the fiberglass (?) reinforced silicone mats I used between the cells held up fine. The bottom of the battery box beneath the damaged cell did partially melt through, but thankfully did little damage to the trailer flooring. The damaged cell's temperature after being removed and sitting for several minutes was ~195 F with the adjoining cells less than 100 F.
Another good thing: the damaged cell did exactly as described on YouTube when damaged this way: lots of very hazardous outgassing and smoke, but with no fire or explosion.
All in all I got off lightly with a smoked-out, stinky trailer, a now-unusable battery that, even though it cost me nothing, ended up providing a harrowing learning experience and lessons for the future: 1) Probably don't drill into the aluminum cell terminals. Sure, 6 times it may work perfectly, but the odds of it going wrong outweigh the benefits, and 2) If you do decide to drill and tap them, remove the battery from the trailer and separate the cells from each other and do the drilling in a safe, clear area (outside would be ideal) with proper safety and fire suppression equipment on hand; there's much less potential for collateral damage if things do go wrong.
Thanks for all the help and input from all the contributors on here - I'd not have learned how to to any of this properly nor known what to do in the event something went wrong without all your input.
Stay safe!
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