not sure if this will help you out,i found this on the internet.
Battery Charger Troubleshooter
When there is a battery failure, there is a possibility it was caused by a bad battery charger. When the charger is only plugged into the wall, it should show a green light. If there is no light showing, confirm that the outlet is good. If the outlet is good, it is very possible that the issue is with the battery charger, not the battery.
If the charger is plugged into the battery only, it should show a green light. (If you have purchased a new charger within the last year, you will not get a green light if the charger is only plugged into the battery. You will get a green light however if the wall charger is just plugged into the wall and not plugged into the wiring harness) If it does not show a green light, it is likely that the charger is not making contact with the battery. The most likely reason for this is a faulty fuse on the wiring harness. This fuse is a 2-amp automotive fuse, and it should be replaced with a 2 or 3-amp fuse available anywhere that sells auto parts. The fuse can blow out if there is a short in the charging system, or if the plug-in end of the wiring harness comes in contact with a battery terminal.
When the charger is plugged into both an electrical outlet and the battery, there should be a red light showing on the charger. A red light showing indicates that the charger is in contact with the battery and is actively charging the battery. Once the battery has reached a voltage level that is considered "fully charged" the red light changes to green. If after 24 hours the light has not changed to green there is no cause for alarm! Remember that when the light is red, the battery is being charged, and you will be able to use your system. After 24 hours or so, your battery is as charged as it is going to get, and if the light is still showing red you should disconnect the charger and go fishing. Replacement chargers and parts can be purchased directly from MarCum's website.
If you are really concerned about your battery, consider getting a basic volt meter to check the voltage of your battery
. They can be bought for less than 20 dollars and will show you exactly what the voltage level of your battery is. If after 24 hours of charging your battery should have at least 12 volts (ideally 13-14 volts) and as long as it is over 12 volts it will work. If it is not at or above 12 volts you should consider replacing the battery. If your unit starts to malfunction while you are fishing, it would not come as a surprise that the voltage has dropped down to 11 volts or lower.
If the charger is plugged into the wall and battery, and you get a blinking light on the charger, it is very likely that the battery is faulty and should be replaced.
Batteries are an expendable item, and must be replaced periodically. Any store that sells ice fishing electronics will stock suitable batteries. You can also buy them at a specialty battery store, or by ordering one from our website
.The batteries that you should use are the "Sealed Lead Acid" variety, they are 12 volts, and range from 7 to 9 amps. The more amps the battery has the longer it will run on a full charge. Your MarCum unit can be powered off of any battery that is 12 volts, even a large automotive or deep cycle batteries will work.
or go to this link and have a read up.
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