Gel Pack vulnerabilities

[aitchw]

Could anyone tell me if Gel Packs are more vulnerable to premature failure due to being left in a low charge state than lead acid types? Also, do you use more or less the same voltage input for charging as lead acid or is it different?

I ask because I use a small gel pack based power supply to drive my fish finder and it has suddenly decided it doesn't want to hold as much charge as it has in the past and is next to useless now. It hasn't given bad service and was not very expensive so no great loss but it is the first gel pack unit I have used.

Thanks,

Howard