The worst charge I had was for a PA31-350, where there was a 3 hour charge, no travel, nose in workshop and supplied battery and paperwork from Aviall [I took old battery away]. I have done the same job, just takes 19 minutes and an endorsement of MR.
DB Cooper, I think you misread UITA's post. He was not complaining about being charged 19 minutes for fitting. Nor was he complaining about a margin on the battery. He was complaining about being charged 3 hours to fit a replacement battery which was fully charged, ready to go in the hangar with the aircraft. At Aussie labour rates, I'm guessing this more than equalled the cost of the battery.
Pretty much the only use for dry charged batteries now is Aviation. They were phased out in automotive use nearly 40 years ago. The main reason they were phased out is that there was a very high warranty rate on them because workshops sold them after filling with acid but not charging before fitting them. Just fill with acid, put them in the car and take the money.
Dry batteries are made by assembling "formed" plates. That is plates that are put in a sulphuric acid bath and charged under the normal regime then dried. They restore a significant amount of charge immediately upon activation and will function immediately. However, alternators never fully charge a battery, so they will never fully restore in service and suffer premature failure.
The recommended retail price of the battery includes acid which is shipped separately in bottles and an allowance for the retailer to fill the acid and bench charge the battery.
In the old days, the most common cause of warranty was broken inter-cell welds. Improved manufacturing equipment eliminated this in the late eighties. That leaves the two major causes of warranty as sulphation from storage of wet batteries too long (lead acid batteries in storage require charging every 10 weeks) or in the case of dry batteries cutting corners in the activation process. Real manufacturing warranty issues on lead-acid batteries is below 1%.
All of this is, of course, being eclipsed by valve regulated lead-acid batteries which are sometimes called sealed lead-acid batteries. These use a very different manufacturing technology which the Japanese & Taiwanese manufacturers led the development to bring them to mass markets in the eighties & nineties. These batteries are much better for aircraft applications.
The third category are the spiral wound batteries (eg Optima & Orbital batteries). The development of these is routed in the old Australian Pulsar batteries developed by Pacific Dunlop. They are wet lead acid batteries (but sealed) and would be really excellent in aircraft, but no-one is interested in the cost of certifying them.
This is a long winded answer, but it illustrates that there is just a lot of nonsense talked to justify excessive labour charges. There should be enough margin in the battery price to cover filling & activation. The labour charged to fit the battery should be the reasonable time it takes to fit it and if you feel the need to add additional costs to cover warranty, then I'd suggest that you might need to take a look in the mirror because 3/4 of "warranty"claims on modern lead-acid batteries lie with the practices of the reseller / fitter.