Re: What Battery to use & method to keep batt chrgd on test stand
If you do some research automotive batteries, you'll find that there are only about 3 companies who make them in the US. So you can even go down to the dreaded Autozone and buy a battery and it will be a good one. Don't believe me. Do the search and read.
My philosophy is get the biggest battery that will fit in the battery box with the correct terminal orientation.
I'd think the engine and fan will run fine off just the battery for as long as you would need to run it on the test stand, but to use the charger at the same time, you need a big charger or risk toasting the charger.
Unless its a jump start type charger, I wouldn't start the engine with the charger connected.
I've had good luck lately moving a small battery tender from a big battery to the motorcycle battery every 2 weeks. Why I didn't buy two I don't know.
Just my opinions...