I got sick of dealing with issues with those power packs and battery issues on my 10 ton dump trailer. Replaced the system with a larger reservoir, a Honda engine, new pump and a valve. I will tell you all of the frustration from a slow and weak system disappeared. Most of the parts were found at Surplus Center. I think I ended up with about $700 in the conversion. Although I've sold the trailer and moved to a tri-axle dump truck, I'd never buy an electrically operated system again.
As far as reservoir size, it's funny that these electric trailer setups come with the bare minimum that is "supposed" to work. However, when you look at a dump truck or basically any other equipment that uses hydraulic power, the reservoirs are much, much larger than what it takes to actually move the cylinders.