I would not use any sort of lower output battery maintainer while coding.
As mentioned, an old school 6-10 Amp charger connected directly to the battery is probably a better option.
Also for vehicles with cigarette lighter plugs that shut down when the car is off and you do not want to connect under the hood, you can use an OBDII port connector for Deltran or other similar 3 Amp or lower battery maintainer/chargers.
http://www.amazon.com/gp/product/B00...1&sr=8-1-fkmr0