how are you deciding the battery only works for 3 hours (battery gage? lift cut out? reading battery voltages?) when it seems "dead" to you, ave you taken voltage readings at rest and with the hydraulics stalled about 3 seconds?
when you say "battery it's ok (volts, specific gravity, water level)" please describe the 'ok' water level is, and tell us the numbers for the spec. grav. and volts, at rest and when the tilt is stalled, and what control system is fitted and serial number of the truck is.
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