Posts: 2753
Location: Mauston, Wisconsin | 4reukmuskies - 4/4/2016 9:18 PM
Just wondering if any of you have experienced this and I am certainly not an electrician so any idea what may have caused it, bad battery or charger malfunction? Certainly cannot trust the charger now.
Craig
OK Craig, here's my perspective. There are two things that happened to cause the explosion.
1. Evolotion of hydrogen gas during recharge (something that is a normal part of the process).
2. An electrical spark inside of the battery. Possible causes are cracked intercell welds or post welds or a short circuit between a positive plate and a negative plate (the plates alternate in sequence).
Its not clear if your batteries are wetcell's or VRLA's. The photo seems to show a wet-cell because of the battery cell filler holes. A VRLA doesnt have removable filler caps. It also shows that there is no electrolyte covering the plates. If these are wet-cells, then I would suspect that a major factor is a lack of periodic maintenance to replenish lost electrolyte with distilled water...the explosion itself will not force all of the electrolye out of the battery jar, its physics 101, the plastic top is the weak link, most forces are directed up & out.
The battery may also have been bad and drawing excessive current from the charger, even though the charger was operating as it should. A periodic check of electrolyte levels should provide a clue, e.g., one battery is using more water than the other.
The charger may be just fine. Its easy to check it. First make sure the other "good" battery is filled to proper electrolyte levels. Go to local hardware store/home depot/menards and buy a inexpensive "digital volt/ohm meter" - read instructions and set it for 20V DC .
1. Connect the meter red lead to positive & black to negative. Write down the voltage. With charger leads normally connected to that battery, plug it in and wait 5 minutes - check the voltage again.
2. Unplug charger and disconnect the charger leads, now connect the leads normally connected to the bad battery. Repeat the test 1 measurements. The voltage should never go above ~14.4 to 14.8V.
3. As for the electrical spark, its not unusual to have cracked welds from vibration or jarring in a boat or a ATV. The only way to lessen it is to put some type of cushion under the batteries, not likely in most boats.
4. Its also possible that what looks like a perfectly good battery can explode while being charged, e.g. because of a cracked weld. It can happen with VRLA's too.
A. Don't leave the charger plugged in over 24 hours. Even a fully discharged TM battery should be fully recharged in 24hrs.
B. Given your charger is 10 years old, I would not expect much from Minnkota if it is bad.
C. If you have wet-cells inspect the electrolyte levels periodically. If both batteries are at same levels, all is good. If one battery or individual cells have lower electrolyte levels than the other battery, something is wrong with that battery or charger. If all cells are equally low its probably a charger control problem. Always go through a recharge cycle after adding distilled water to any cells.
D. A digital volt/ohm meter is a good tool to have in the boat, etc.
Battery voltages after charging with battery charger off for 8 hrs or more (resting):
Discharged = 10.5V or less.*
Partially discharged = 11V-12V*
Charged to 100% 0f capacity = 12.7V
*something is wrong! Either battery failure or charger failure.
I'm glad you didn't come home to be welcomed by the local fire department....
Good luck!
Al
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