Normal voltage drops

[mzsk07]

I have 115ah deep cycle battery. It should provide at least 100 amperes when discharged at 5amp per hour for 20 hours. It's voltage should drop from 12.8 v to 12.2 v after proving at least 50 amperes. This is all that should happen normally. But what happens really is weird. My battery drops voltage from 12.8v to 12.2v after giving only 20 amperes. What can be the problem?

[ClassicCrazy]

Was it fully charged ? How old is the battery ? Is it flooded lead acid or a sealed AGM type ?
What was the temperature of it ?
Quality of the battery could be part of it.
Those trolling motor type inexpensive  lead acid deep cycle batteries if that is what it is - aren't really the best - they don't have as thick of plates as something like golf cart batteries or other deep cycle batteries do .
The thing would be how long will it hold at the 12.2 v.
If it is a brand new battery it can take a few cycles to break in to full capacity .
The  deeper you discharge the battery the less cycles you will get from it.
Those are some quick thoughts I had.

Larry

[Westbranch]

115 Ah  and Deep Cycle make me think it is a FLA and a modified starter battery...
First thought is that it probably needs an EQ...