Top2MP wrote:
Has any one installed a second battery in series and does that extend the life?
Will that be too much voltage?
NO.
Yes. But you can replace the one 12 V with two 6 V in series for approx. twice the capacity.
Read the tutorial recommended.
AND....you need to get a multi-meter and do some tests to be sure that your panel isn't lying to you. If there are lights only, they are notoriously inaccurate.
The battery might be bad but the charger/converter might have failed too......or both.
If your present battery has removable caps, have you checked the water level lately ? Any guess as to how old it is ??
Any name brand deep cycle battery with a similar capacity (amp hours) should be fine. An AGM type would be practically maintenance free and likely will last twice as long but is a good bit more expensive too.