Honda 20 HP causes battery to explode

[tessor]

I tried to use the electric start on my 2004, 20 HP Honda outboard for the 1st time this year but it didn't turn the starter motor. Assuming the battery was low on charge, I pull started the unit with no problems. After trolling for about 2 hours with only my fish-finder operational, my 12v battery exploded, splitting the battery case and blowing-off the top caps. I then disconnected the battery cables and trolled back to shore.

Once back to shore, I connected another battery (that I knew was fully charged), started the motor with the electric start, than grey clouds of smoke started comming from a small (about 4"x4") black, finned boax on the right side of the powerhead. I immeadiatly disconnected the battery and completed my fishing without use of electric start.

Any idea why the battery would explode? It is a 400ca, deep cycle that is only three years old.

Can I assume the black-finned box on the side of the powerhead would be a voltage regulator?

 

[pvanv]

Re: Honda 20 HP causes battery to explode

Severe overcharge could blow a battery, but it's rare. Usually just boils it. Of course, doing that for a couple of hours of trolling is a different story, especially if the water in the battery was low. If the alternator/rectifier/regulator is bad (the smoke sounds like yours is), that could be the culprit.

 

[tessor]

Re: Honda 20 HP causes battery to explode

That's exaclty what it was... The dealer told me that the voltage regulator was faulty resulting in an over-charge of the battery. $300 later, i'm back on the water. I can now understand the importance of having a battery box!