Question about my fish finder battery

I am not too tech savvy about batteries, so I am hoping to find some help here. I have my Lowrance Hook 4 that uses a small 12v battery. I was fishing on Saturday and my fish finder suddenly lost power. I turned it back on and it would boot up and stay on for a few seconds after that, and then die. It did this several times so I figured my battery needed charging. I charged the battery overnight and the fish finder would still turn off. I then plugged it into another battery and it worked fine. So I checked the voltage on the battery and on the charger when it was plugged in. The battery showed just over 9 volts and the charger showed a little over 6 volts when plugged in. I hooked up the battery to the fish finder and took the voltage as it booted up, and it read around 7 volts. So my question is which is bad, the battery, the charger or both? Any info would be greatly appreciated.

Kevin

If your battery is showing just 9 volts it is bad. Here is a battery chart. So that would be the reason the sonar is shutting down.:twocents
http://popupbackpacker.com/wp-conten...art-Trojan.jpg

Even if your battery was bad, with charger on it and pluged in it should read at least 12 volts. So I would say charger is bad and may have ruined battery. If you have another charger I would hook it to battery and see what it does. If not you might even hook up a set of jumper cables and just let it sit for a hour or two. Take reading on battery before and after disconnected. May not fully charge but if it is still good it should show some increase in voltage. If not it is bad for sure. I'm assuming you are using something like a lawn mower battery.

Yes, it is a small battery. I will hook it up to my big battery charger and see if there is a difference. Thank you for the info!

Thank you for the info!