Lead acid battery charging

You can certainly do this - usually for cycle-based charging, a safe voltage cap would be 14.4V with a current limit that matches the manufacturer's limitation. You should manually terminate charge when the current falls to a low-enough level (varies depending on who you read) - excess charging can boil the electrolyte or cause significant bubbles to form in gel cells and loss of electrolyte causing permanent capacity reduction. For float based charging, 13.6-13.8V would be a better choice, some cells do not need current limiting under that condition and generally can sit there all the time without much degradation. The optimal voltage does vary slightly depending on ambient temperature.

The main pitfalls are that a reversed connection will either kill the power supply or kill the internal reverse-connected bypass diode which will then kill the power supply. Another pitfall is that many power supplies don't have a true "switch" of the outputs, so connecting a battery can result in a spark as it charges up the output capacitors. When the power supply is off, any bleeder-resistors or down-programmers may end up discharging the battery slowly as well.

But they're all pretty much no big issue. If you'd like, you could use a hefty external diode to keep the battery from draining into the supply but at the cost of heat and loss of voltage accuracy (unless using 4-wire connection). I personally just use a switch to isolate the battery and slam the switch shut after the supply is on and stabilised, opening the switch before turning it off.

- Gough

You can certainly do this - usually for cycle-based charging, a safe voltage cap would be 14.4V with a current limit that matches the manufacturer's limitation. You should manually terminate charge when the current falls to a low-enough level (varies depending on who you read) - excess charging can boil the electrolyte or cause significant bubbles to form in gel cells and loss of electrolyte causing permanent capacity reduction. For float based charging, 13.6-13.8V would be a better choice, some cells do not need current limiting under that condition and generally can sit there all the time without much degradation. The optimal voltage does vary slightly depending on ambient temperature.

The main pitfalls are that a reversed connection will either kill the power supply or kill the internal reverse-connected bypass diode which will then kill the power supply. Another pitfall is that many power supplies don't have a true "switch" of the outputs, so connecting a battery can result in a spark as it charges up the output capacitors. When the power supply is off, any bleeder-resistors or down-programmers may end up discharging the battery slowly as well.

But they're all pretty much no big issue. If you'd like, you could use a hefty external diode to keep the battery from draining into the supply but at the cost of heat and loss of voltage accuracy (unless using 4-wire connection). I personally just use a switch to isolate the battery and slam the switch shut after the supply is on and stabilised, opening the switch before turning it off.

- Gough