Another Battery Question???

[Capt. Birch]

Just about all modern gps and fish finders have built in voltage meters. You can go into your set up screens and turn them on. Garmin's gps allows you to set a voltage alarm. As soon as it hits the low setting the screen will flash low voltage and show it. You can tell if you are charging or not pretty fast.

[Stray Cat]

If you have room to add a battery, I would recommend using this product from blue seas. I use it on my boat and it works fine. I have one starting battery and one house deep cycle battery for each engine.
http://bluesea.com/category/2/productline/overview/329