I am in a flying club with a nice low time Piper PA28 140, and we just upgraded it with with a Garmin GPS175 and Aspen E5 (eliminating some old stuff, including vacuum system). Being in the US, it's still Winter, and usage is low. However, our 8 semi-geriatric members (including me) will very soon be needing a ground power supply, so as to have a bit of mercy on the battery while getting comfortable with the new equipment. (To be honest, I could also use it for a little play time and currency in my own glass panel Arion Lightning as well.)
My thoughts are to buy an RV (that is, Recreational Vehicle) "power converter" as these are readily available at less than about $120 US (or $190 AUD) with generous capacity of 45 to 60 amps and a piper style plug. In general, the modern RV power converter units are switching style power supplies, advertising low ripple that is suitable to drive electronics with or without battery filtering. They also double as battery chargers, and can be connected long term as long as they are bought for the type of battery in use (flooded wet, AGM, lithium). In general, these have a sag in delivered voltage, so that if connected to a weak battery, they don't charge at ridiculous currents. That would seem to be safer than, say, a straight power supply that regulates to simply hold a fixed voltage of say 13.8V. I would think a simple regulated bench power supply might not be so great to connect to small semi-discharged aircraft battery that isn't too keen on being hit with, say, 60amps.
If an RV power converter unit sags in voltage to, say, 12.5V or so while in use, it seems to me that a standard battery would just give up a little charge, but be replenished once the training session is over.
An alternative would be something like the more pricey Aircraft Spruce 12V, 25A power supply with Piper plug (11-05086), currently costing $289 USD. However, although Aircraft Spruce lists it for use as a ground power unit, they also state the power supply is a Schauer model JAC2512-PC. If I go to the Schauer web site, they say it's a battery charger and not for use as a power supply. I'm guessing that's because it needs a battery to smooth out power, but I really don't know why they don't recommend it as a power supply. That plus the much higher cost made me look for something else.
What do you guys recommend ?