Charged TM batteries night before heading out. One battery took a little longer to charge, fished all day, no issue losing power or anything like that. Got home, charged batteries and the one battery took twice the amount of time to charge. Both are fairly new batteries purchased in the last 3 months. I did leave for about 5 weeks and they did sit. Is this normal or a bad battery?

Have you tried charging with and without the jumper cable between the two batteries to see if it makes a difference?

Do you have more auxiliaries (fish finders/lights/etc) wired to one of the batteries compared to the other?

I only have the TM hooked up to them and I detach all cables when charging.

I'd check the water level in the slower to charge battery.

Do you still have the receipt?

If the water level looks good, another thing I'd try is one of those rechargers with a "recondition/desulfate" cycle.
Auto service places often have these.

Proba lynch not

May also be your charger. Try swapping the charging cables. If the problem follows the cables, it's your charger. If the problem stays with your problem battery, then it may be a battery problem.

Better not be, its new!

First thing I would check also assuming they are wet cell batteries.

I bought a new battery with a daed cell, it happens.

I would suspect a bad battery. My godson bought bought a brand new Optima blue top with a bad cell.

As stated probably bad battery.