For what it is worth, here is what I have learned through years of "learning" about my equipment batteries; Essentially there are five different types of chargers
1. High amp, fast charge (generally has a starting position)
2. Low amp, slow charge (as in some deep cycle chargers)
3. Battery tenders
4. Battery minders
5. Trickle chargers
Some chargers are a combination of 1 & 2.
Tenders charge at about 1.00 to 1.25 amps until the battery is "topped-off." They then go into "float" and do not charge until the battery voltage drops.
Maintainers charge at about 1.00 to 1.25 amps until the battery is fully charged, then go into a float/desulfation mode. The desulphation mode is supposed to prevent sulfation of the plates allowing the battery to last longer.
Trickle chargers charge at 1.00 to 1.25 amps continuously.
Continuously charging at a any amperage will cause overheating/boiling.
The only problem you would have to contend with is that if you use a tender or maintainer and the power does go out and the pump reverts to battery power, I think the "safety circuit" in the charging unit may "trip." You would then have to "re-set" it when the power comes back on.