By Joe Gresh
You’ve probably read the story of my new, solar, mondo lithium battery bank. It consists of 16, 12-volt, 100ah lithium batteries and so far is working well. What you don’t know is I actually have 17 lithium batteries.
When I ordered the batteries one of them was dead on arrival. Like zero volts. This is a huge red flag because the LiFePo battery is know for its ability to hold a charge for long periods of time. I tried connecting a battery charger to the thing but all I got were sparks.
CT contacted the seller and they said it’s normal and to jump the battery with another (good) battery. I tried that and got even bigger sparks. The thing was shorted internally. CT went back and forth with them, and they wouldn’t send another battery. They did give us a refund, though, so it was all good and I bought another battery of a different brand.
Once the new bank was online and operating well, I broke down all the shed-filling, cardboard packaging for 17 batteries and hauled it off to the La Luz dump (a very fine dump). This left me with a lone, dead lithium battery. I was going to toss it out anyway, so I decided to open it up and see what a lithium battery looks like inside.
The top part of the battery box snaps into the bottom but I didn’t know that, so I set the circular saw to about 1/16″ depth and (after taking the battery outside in case it burst into flames) cut the top off.
The top part was still attached. I didn’t want to cut any deeper because I had no idea what was inside. Wedging a flat-head screwdriver under the saw-cut lip and working it around the perimeter of box released the lid. Turns out I didn’t need the circular saw. After removing the lid, the internal parts easily slid out of the box, all in a nice, neat tray.
Once the thing was apart the problem was obvious. Both the positive and negative wiring to the output posts were shorted out on the big, metal plate. The shorted metal plate covers the battery monitor circuit board.
The negative switch is how the battery monitor connects the internal bits with the external world. Over charge the battery? The battery monitor switch switches it off. Short out the battery? The battery monitor switch switches it off. Drain the battery too low? The battery monitor switch switches it off. For all I know there’s a high/low temperature cut off in the thing.
It turns out whoever built the battery put the terminals to the output posts on upside down. This moved the barrel/crimp part of the wire connection that much closer to the metal plate.
All things considered, if you’re going to screw up the battery this was the least damaging way to do it. Since the + and – were directly shorted before it got to them, the electronics and lithium cells weren’t involved the short circuit. The battery monitor system kept the thing from burning up due to the short.
Once the lid was off and the source of the short removed, the battery showed voltage again. Pretty cool. I gave the battery a charge and all seemed normal. I load tested the thing at 100 amps and it held voltage fine. You know what this means.
The fix was as simple as flipping the wire terminals over allowing that extra 3/16″ clearance. I reassembled the guts into the battery and snapped the lid back on and now I have an extra, good lithium battery. While technically it’s a free battery I have some time in the repair. Now I know what’s inside the black box. I’ll probably run some gorilla tape around the box so the iffy lid attachment stays put and call it a win.
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