personally i am not big on letting a battery sit idle for extended lengths of time, they will have a certain self discharge rate, which gets worse as they age.
over time the self discharge which just like regular discharging will build up some sulfation and over 4 months is likely to harden and become difficult to break back down on recharge.
the result is loss of capacity.
some battery technologies are worse than others when it comes to self discharge.
the higher the antimony content in the plates the higher the self discharge rate.
iirc figure on about 2% per month, which compounds like interest monthly (maybe), and likely will be higher as the batteries get older.
at the very least i would make a good log of specific gravity readings if they are flooded cells, and then upon return be prepared to fully charge them and if necessary do an equalization charge to get them back into proper condition.
how big of a bank do you have? what type of battery technology? agm, flooded,vrla, etc.. ?
each have their own concerns.
bob g