Bests & Worsts Reviews from Amazon

This battery pack contains four 12v 9ah batteries. The batteries are model CSB HR 1234W F2. This battery pack is not made so that the batteries can be easily replaced by the user like the main UPS unit that it connects too. This is disappointing. They could have designed it so that the batteries slid out for easy replacement like they do on the master UPS unit. But you can still easily replace the batteries with a little work. Although you might break off a small plastic tab or two on the front cover in the process but it won't matter or hurt anything. Presumably your two year warranty has expired before you need to replace the batteries so you will have nothing to lose. 1. Remove the 6 screws on the back of the unit. 2. Pry off the front cover. 3. Lay unit on it's side so that the 3 screws on the front are facing up. 4. Remove the 3 screws on the front of the unit. 5. Slide the cover towards the back of the unit to remove it. 6. Disconnect the leads plugged into the F2 terminals on the batteries. 7. Remove batteries. 8. Insert new batteries and reconnect the leads. When I plugged the unit into my BR1500G UPS it basically tripled my estimated runtime per the PowerChute software. Which is exactly as expected since the BR1500G contains two batteries and the external battery pack contain four additional batteries. My reported runtime is now 96 minutes with 233 watts draw. I found no fan inside this external battery. The BR1500G contained 2 Kung Long WP1236W batteries. 12V 9ah 36W. Made in Vietnam. This external battery pack contained 4 CSB HR 1234W F2 batteries 12V 9ah 34W. Still rating it 5 stars. Although I'm disappointed about difficulty to replace batteries when the time comes. Also, I'm really curious to know if the BR1500G is able to inform the user when the external battery needs replacement or if it just gives a general replace battery message for all batteries. Looking forward to seeing future reviews.