Matt,
Look at both battery banks for a relatively small gauge wire to the positive terminsl on each bank or on the isolator. If you don't see them, you do not have an echo charger. Magnum makes a device that will work as well. Also I used to use a standard AC trickle charger. I permznent attached to the chassis batteries and plugged it into the AC outlet in the bay. Just like the echo charger and other similar devices,, it only works when AC power is present.
Dennis