The APC Back-UPS Network 40, or BN4001 is one of those units that has an awkward battery size (5.94″D x 2.01″W x 3.74″H) that may be hard to find at your usual go-to such as Amazon, Newegg, Tractor Supply, Batteries+, and others. However it is an excellent battery backup and purchasing a Battery in 2026 is way cheaper than purchasing a new unit.

The unit usually ships out with a CSB UPS 12240 6 F2 battery, but replacements from other companies will work just fine. Here are two solid options:

1. UPS Battery Center Direct Website – CSB UPS 12240 6 F2 12V 240W 6.5Ah
2. UPS Battery Center on Amazon

Here are other products comparable to the price and capacity of this Battery Backup Unit:

1. CyberPower ST425 425VA
2. APC UPS 425 VA BE425M
3. Amazon Basics UPS 600VA/360W
4. APC UPS 600 VA BE600M1
5. APC UPS 650 VA
6. Full Amazon search here

And here are some units with a larger capacity and better runtime:

1. GOLDENMATE 1000VA Lithium UPS
2. APC UPS 850VA BE850G2
3. CyberPower 850VA EC850LCD
4. Cyberpower CP850AVRLCD
5. Amazon Basics 1000VA/550W UPS
6. CyberPower CP1000AVRLCD
7. APC Back-UPS Pro BX1000M
8. CyberPower CP1000PFCLCD PFC
9. Amazon Basics 1500VA UPS
10. APC Back-UPS Pro 1500VA BX1500M
11. CyberPower 1500VA CP1500AVRLCD3
12. APC UPS 1500VA Sinewave
13. CyberPower CP1500PFCRM2U PFC Sinewave
14. Full Amazon Search here