My Depth Finder said low voltage and i knew i had the battery on the charger all night. So i went to swap my batteries from my trolling motor battery so i could continue to fish and the terminals were burning hot. Can this be caused by a bad battery? Or is something in my depth finder or trolling motor causing it?

My Depth Finder said low voltage and i knew i had the battery on the charger all night. So i went to swap my batteries from my trolling motor battery so i could continue to fish and the terminals were burning hot. Can this be caused by a bad battery? Or is something in my depth finder or trolling motor causing it?

lose or dirty connection at the battery.

My Depth Finder said low voltage and i knew i had the battery on the charger all night. So i went to swap my batteries from my trolling motor battery so i could continue to fish and the terminals were burning hot. Can this be caused by a bad battery? Or is something in my depth finder or trolling motor causing it?

lose or dirty connection at the battery.

Thanks but not it, I check those on a regular basis

Thanks but not it, I check those on a regular basis

Did the second battery's terminals get hot when used?

Are you using wing nuts on the terminals?

It can happen that the internal battery connections to the posts are bad, a load check at a battery store will diagnose it for you.  If both posts are hot it seems too much coincidence for dirty connections.

My money would be on the cables or cable connectors. Very possible where they crimp the terminals onto the connector, it's gotten corroded inside. I see that quite often with this cheap crap on the market now. That's why I always make my own cables, using heavy, zinc plated connectors, crimped and then soldered, then use a heavy heat shrink that has a heat activated sealant that seals them when shrunk down.

Another possibitly is the studs are not making good connection where they are leaded into the battery. Several times I have seen these melt out of the battery because they were creating a resistance between the stud and the lead holding them.

I work with batteries everyday that are handling way more amps than your TM and I've never seen one heat up from bad internal connections. Not saying it can't happen, but it would be very rare. I do however, very often see them melt terminals because of bad/loose cable connectors.

What it seems to be is that the battery was still good but on its last leg. When you are trying to pull current that the battery can not produce it can cause this. Replaced the battery and so far so good but i havent worked it hard yet.

thanks for the help

Resistance to the current causes the heat.  When a battery is over worked, the case gets hot, just like if it's over charged.   Hot terminals are cause by a resistance at the terminals, that's the source/location of resistance to the current.

I hope you threw the wing nuts away and used brass hex nuts.  If not brass, at least stainless.