In theory a 12v 100ah battery can supply 10amps for one hour when inverted to 120v. There is, however, some overhead for the inversion and I believe you can't run the battery down to 0%, so it's somewhat less than that hour. If the saw is 15 amps, I would guess it could power it for 30-35 minutes. I would get a cheap charge controller to manage the charging aspect. You can usually put in anywhere from 12 to 24 volts and the controller can convert to what the battery needs and stop when full. These can be $15 on Amazon, and despite what many say, work pretty well.

I understand it wouldn't power it for long, but I never use it all day or I'd bring the bigger gas generator with me. Maybe what I was really asking was if one battery can handle the surge of a table saw (3k or 4k surge watts) or use 2 batteries to spread the load out. I'll keep in mind the cheap charge controller.

yeah, i built one similar to that so i could wheel it out whenever i needed power tool access. the 2000W inverter is able to start all the tools i own, and has a built-in charger function. https://www.reddit.com/r/SolarDIY/comments/10r7up0/diy_battery_backup_cart/

Glad you commented, I didn't know that make an inverter/charger. Was curious how all that worked. I like your set up. I'm gonna start with one battery and maybe do a cart like yours if I think I need it. Thanks

You should double up the LiFePo4 batteries. They are usually rated to 1C discharge rates or 1 times its capacity. In this case, you're limited to 100 amps, or 1,200 watts, continuously.

> if one battery can handle the surge of a table saw

That depends on how much current the battery can provide. The Ah rating is not a measure of power or energy. Ah times volts is energy in watt-hours. You need a high enough Continuous Discharge Rating (CDR) for the peak load. 15A @120VAC is the same power as 150A at 12VDC (ignoring conversion losses). The Ah rating can be used to estimate run time, but the Ah rating is not specified at maximum discharge rate. A 2000mAh cell can deliver 2A for an hour, but if you draw 20 A from it, the Ah rating will go down. It won't run a 20A load for 0.1 hour.

I like the one guy who commented and made a cart for his batteries in another thread. And the more I think about it, having 2 would be better overall for lots of reasons for wear and tear and extended time. Maybe 30 minutes might not be enough but an hour would. Now I'm if a single bank charger is ok for 2 batteries in parallel or get a 2 bank charger.

I would charge them together. Two chargers mean you have to disconnect/charge/reconnect the 2 packs each time. And the 2 packs must be at the same state of charge when paralleled.

Didn't know I could do that. I'm pretty rubbed in with residential electric in houses since I've remodeled homes for 20 years. But this dc/battery stuff throws me off. Can I leave the inverter hooked to along with the charger or should I buy 1 or 2 disconnects?

As long as the inverter has an ON/OFF switch, you can leave it connected. Make sure you fuse the battery output.

Thanks buddy, will do

Which inverter/charger did you end up picking?

None yet, waiting for work to slow down. But I'm thinking the harbor freight Jupiter one for 170. 2000 running and 4000 surge works probably handle a table saw. I'm debating also with making a cart to move it or stationary in the back seat of the truck.