Will this power a 12v 25ah winch

I wouldn't do it for long. A battery's charge level will drop exponentially and will be useless for attempting to operate anything well before it reaches zero volts. A 20 amp hour battery will deliver 1 amp of discharge for about 20 hours before it's completely flat. a 25 amp winch would draw this battery to completely flat, no charge in less than an hour. Realistically, the winch would become too weak to pull anything in less than 10 minutes. For using something like that, you'd want a full sized deep cycle battery that's about the size of a car battery. I'd recommend at least 100ah capacity.

This is a standby/lighting battery, not a vehicle battery. It does not have a CCA rating.

what gauge wire should i use?

It depends on the load. I have 12 gauge for 30 amp Ham Radio operation.

Battery is fully charged. Why did battery votage just get 10.3V?

30 year master tech here. THE REASON YOUR BATTERY DID NOT COME ALL THE WAY UP TO 12V IS BECAUSE IT HAS BEEN SITTING ON A SHELF FOR SO LONG IT HAS A BAD CELL.

ASIN	B07VFT6BQT
Batteries	1 Lithium Ion batteries required. (included)
Best Sellers Rank	#22,242 in Health & Household ( See Top 100 in Health & Household ) #28 in 12V Batteries
Customer Reviews	4.5 4.5 out of 5 stars (13,134)
Date First Available	August 1, 2019
Department	unisex-adult
Item Weight	42.1 pounds
Item model number	LFP1235
Manufacturer	Weize
Product Dimensions	7.79 x 6.54 x 7.09 inches

WEIZE 12V 20AH Lead Acid Battery Replace UB12200 FM12200 6fm20 EXP12200 12V 20AH 22AH Batteries

Details

Description

Specifications

Common Questions