Bad Charger?

[ERTF]

My bow thruster batteries are charged by an AC charger on a timer. The previous owner installed fuses on both the negative and positive wires for each leg.

I caught my thruster batteries draining even when not used, which made me suspicious of this charger as the cause. I recharged then took out the fuses to see if the batteries drained. When i put the fuses back in, they sparked at the fuse holder even though the charger wasn't plugged in to AC. Is this normal or a sign of a short inside the charger?

 

[Mac2]

So many questions. I’ve never heard of a fuse on the negative side. Why are you thinking the charger is bad vs the batteries? The signs a battery is going bad is when they stop holding a charge. How old are the batteries? Was the thruster breaker turned off when you installed the fuse and it sparked? Also, why is the charger on a timer? Doesn’t it have a float mode?

 

[ERTF]

As i said, i didnt install the fuses. The batteries are at most 2 years old and basically never used. Thruster disconnected.

 

[O C Diver]

What is the battery voltage?
If the charger is plugged into 120 VAC, it may generate sparks do to significant difference between voltage of the batteries and the charger.

Ted

 

[ERTF]

What is the battery voltage?
If the charger is plugged into 120 VAC, it may generate sparks do to significant difference between voltage of the batteries and the charger.

Ted

As stated, the charger was unplugged from AC when i got the spark putting in the fuse.

 

[Mac2]

I would think a quick test of having the volt meter on the battery and then removing/replacing the fuse, would show any draw on the battery. Im not a charger expert, but capacitors hold an electrical charge, which could account for the spark. Can you tell us what charger you have and why it’s on a timer? I only ask because if the charger only bulk charges, which would explain a timer, your batteries could have fried.

 

[Delta Riverat]

Chargers do spark when connected even if not powered. Both of mine advised same in manual and not to worry, normal.

 

[ERTF]

I would think a quick test of having the volt meter on the battery and then removing/replacing the fuse, would show any draw on the battery. Im not a charger expert, but capacitors hold an electrical charge, which could account for the spark. Can you tell us what charger you have and why it’s on a timer? I only ask because if the charger only bulk charges, which would explain a timer, your batteries could have fried.

It is a pro mariner pro tournament 300 triple.

It's on a timer because why would I have a charger running constantly for batteries that are rarely used and mostly are just being kept topped.

 

[Mac2]

It is a pro mariner pro tournament 300 triple.

It's on a timer because why would I have a charger running constantly for batteries that are rarely used and mostly are just being kept topped.

Understanding Battery Float Chargers: A Comprehensive Guide

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[Mac2]

I think preventing sulfation is the big one.