Battery Tender 4AMP Smart Battery Charger and Maintainer - costco.com for $39.99

UPDATE: Sale has been extended to 12/15

costco.com has the Battery Tender 4AMP Smart Battery Charger and Maintainer on sale for $39.99. The sale is good through 12/15. Here are the specs:

Input: 120VAC @ 60 Hz
Output: 12 Volts DC @ 4 Amps
Charges both 12 Volt & 6 Volt Batteries
Selectable for AGM/Standard/GEL or Lithium (LiFePO4)* 12V only for Lithium
4-Step Fully Automatic Charging (Initialization, Bulk, Absorption, Float) Automatically switches to float / maintenance voltage after fully charging the battery.
Quick Disconnect accessories included: Alligator Clips and Ring Terminals
Spark Proof
Water Resistant
Short Circuit Protected
Reverse Polarity Protected
Safety timer: 72 hours
Agency Approvals: UL, BC, FCC, RoHS
Dimensions: 6.8" L X 3.68" W X 1.96" H
Weight: 1.1 lbs. (charger only)
5-Year Warranty
50 State Compliant

I was hoping the 3AMP would go on sale, but I'm OK with the 4AMP version. I plan to use it to keep my two 12v RV batteries charged and maintained throughout the winter.

LINK [costco.com]