How To Replace & Upgrade Your APC Smart UPS Battery

Power Supplies, Tutorials

New Battery Installation, Evaluation & Conclusion


Spending an unreasonable amount of time picking a product can be a consequence of past poor choices, but we eventually settled on Mighty Max after combing through hundreds of customer reviews (Amazon says that we must inform you that this link to Amazon Customer Reviews could be construed as an ad). We saved around five dollars by ordering the two pack (Amazon says that we must inform you that this Amazon Product link could be construed as an ad), understanding that even though it had fewer reviews, it contained two of the same highly-rated single batteries.

Arriving from Amazon partner Mighty Max after about four days, the Mighty Max ML22-12 two-pack contains two sets of terminal hardware in addition to its batteries. Note that grasping the top of the batteries is easier after pulling out the cardboard protector.

But wait, you’ll say, the ML22-12 isn’t a direct replacement for the SP12-18! But it is a replacement for the SP12-22, and it turns out that both the 22AH (amp hour) and 18AH version of these batteries have the same casing. We’ll eventually attempt to prove the veracity of its 22% greater capacity rating.

We could have bought double-sided adhesive foam tape, but we’d rather have the option of easily separating these batteries if one fails. Cutting a piece of similar-thickness foam wrap and sticking it between the batteries before taping them together seemed sufficient, followed of course by bolting on the original battery’s connector and bridge. Terminals are appropriately labeled (-) for the black wire and (+) for the red wire, and the fused link on the other end can be flipped either way.

With everything plugged and bolted back together, it was time to pick a source of continuous load: According to our P3 Kill-A-Watt meter, the coffee maker pictured uses 865W to heat a pot of water. It heats 12 cups in approximately 10 minutes, so we overfilled it to around 13.5 cups

APC’s interactive chart shows that its SUA1500 will run 8.3 minutes at 865W when equipped with a new RBC7 battery. We screenshot the most pertinent data:

Our unit would have to power the coffee maker for 10.1 minutes for our 22AH batteries to show the anticipated improvement. The first run failed with only around 8 cups of water heated in exactly eight minutes before shutdown. As it turns out, this was a problem of programming. It’s time to reset!

Draining the unit completely to force a “braindead” reset and then recharging pushed our coffee maker’s runtime out to 10.3 minutes, besting the 10.1-minute expectation. So yes, we are getting that 22% expected gain, and a bit more to be precise. Always reset your UPS after updating the battery!

That extra bit of data also gives this how-to a bit of duality, in that it resembles a review. And since it resembles a review, let’s consider the pros and cons of this battery kit:

Mighty Max ML22-12 Upgrade For APC Smart-UPS 1500
Pros: Cons:
• Provides 22% More Capacity Than RBC7
• Half the price of original RBC7 battery pack
• Requires connectors from original battery pack
• May have less longevity than original RBC7
The Verdict
Even in the unlikely event that these batteries provide half the service life of the originals, gaining 22% capacity at 50% less cost makes this two-pack a smart buy.

While the same reviews that caused us to choose this battery model over other brands imply that it might only last four years, many customers have assigned the same service life to the original RBC7 from APC. Perhaps we were lucky get eight years out of our APC RBC7? While we can only hope to have that same good luck with this pair of ML22-12 batteries, having the extra capacity is worthwhile even if this half-priced kit survives only half as long.

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