Harman 502H battery backup vs 512H

I decided to add my photo so you know what I look like. I found someone selling a 502H battery backup and see that the latest seems to be the 512H. Does anyone know the difference between the two?

Yes, the "H" denotes a product designed for Harman Stoves. The 502 is designed for manual light stoves and the 512 is designed for stoves with auto ignition

Thanks for the info. There is a 502H for sale on the Boston Craigslist for $250.00. I don't know how many times used battery backups show up for sale or if it is a good price. This is not my ad and I do not know the seller. I'm not sure if he would be willing it to ship if someone wants it. I believe the seller is a re-seller of Harman stoves in the Newberryport area because I see a lot of used Harmans for sale on Craigslist in that town.

I would do some research first because in this case it is a "used" electronic device....how old is it anyway? it could be 10 years old. if you look on stove sentry's (or pump sentry) website, you can buy backup units cheaper directly. you can buy pure sine backups like the sf707, instead of modified sine units. Also, you can go to an inverter website and buy a larger watt inverter that has a built in transfer switch and charger. Or buy an inverter by itself and buy a transfer switch separately. The sentry battery backup units are nicely made, they are just small wattage. If you invest in a larger inverter you might use it for other things besides the pellet stove, like backing up a fridge or sump pump.