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Replace The Batteries In Your APC Back-UPS Unit Yourself For Less!

Updated on December 8, 2014

APC Back-UPS Unit

My APC Back-UPS CS 500 that needed a new battery, I took over this orphaned unit without any battery.
My APC Back-UPS CS 500 that needed a new battery, I took over this orphaned unit without any battery. | Source

What Does A UPS Do?

APC's line of uninterruptible power supplies are very handy devices. In the event of a power outage, your PC or Mac won't shut off with the power going out. Depending on the model of UPS that you are using and how large the battery or batteries are in it, you may be able to keep working for a few more minutes to an hour or so. This gives you enough time to finish saving any work you are doing and shut down your computer to prevent loss of data or risk damage to your computer hardware.

APC UPS units can also have other uses, such as providing backup power to a DVR set top box from your cable or satellite TV company. In the event of a short outage (less than five minutes), a UPS can keep your DVR set top box chugging along so that it doesn't have to go through a lengthy reboot process once signal is restored. If the batteries in your UPS have enough capacity, your DVR might be able to ride out a power outage of 1-2 hours in length and not miss any of your shows during that time.

How Long Should My UPS Battery Last?

Now, the battery in most UPS units might last a minimum of two years, maybe more depending on how frequently the battery gets used in the UPS (less outages means less use means a longer lifespan). When it comes time for replacement, which most APC units will happily let you know by setting off alarm bells that would drive one mad, or by simply lighting an indicator on the front that indicates that battery replacement is required since it has failed the self-test of the UPS unit.

Replacement UPS Battery For BK500MC or Back-UPS 500 Models

Where Can I Buy A Cheaper Replacement Battery For My UPS Unit?

I recently acquired an APC Back-UPS CS 500 model unit that came with no battery. Looking up the specs for it on APC's website, they list it as using RBC2, or Replacement Battery Cartridge #2 packs. Googling online for the specifications for this battery indicates the capacity in amp-hours as being 7 Ah and the battery voltage itself being a standard 12 volts. APC's website only list the physical dimensions, with a sticker price of $44.99 each plus shipping and handling and tax (if applicable in your state/zip code.

The model number should be indicated on either the back of your UPS or at the very least on a sticker on the underside that identifies the unit. You can search the model online for your particular model to get the specifications for what battery it uses in terms of capacity and also physical dimensions to find a match at sites such as Amazon or even eBay.

Shopping on Amazon.com, I found a battery that matched the physical dimensions exactly for my Back-UPS CS 500 model, was 12 volts, and had a capacity of 8 Ah, which would give slightly longer run time during a power outage. The price listed, at the time of this writing (and can vary higher or lower with the price of lead, so may change at any time), is $18.49 for a drop in replacement for APC's overpriced battery that they don't even manufacture, with, get this, free shipping!

If you have a business that uses several UPS units at individual workstations or are an individual that uses multiple UPS units throughout your home for computing, A/V or even medical equipment, then purchasing non-OEM replacement batteries online can be a LOT cheaper than going back through APC to buy an overpriced battery that sells for less elsewhere.

Replacement Battery For Back-UPS CS 500

A replacement battery that I ordered online for my APC Back-UPS CS 500.  It's rated for 12 Volts and 8 Ah of capacity.
A replacement battery that I ordered online for my APC Back-UPS CS 500. It's rated for 12 Volts and 8 Ah of capacity. | Source

Replacing The Battery In An APC Back-UPS CS 500

My APC Back-UPS CS 500 unit lying on its side, showing the battery access panel.
My APC Back-UPS CS 500 unit lying on its side, showing the battery access panel. | Source
The battery cover removed exposing the positive and negative terminal cables.
The battery cover removed exposing the positive and negative terminal cables. | Source
Another view with the unit lying on its top side.
Another view with the unit lying on its top side. | Source
View from above with the battery installed before re-inserting the cover panel and placing the unit right-side up.
View from above with the battery installed before re-inserting the cover panel and placing the unit right-side up. | Source

How Do I Replace My UPS Unit's Battery?

Replacing the batteries themselves isn't that difficult, depending on the model of UPS you have. For the smaller standalone units that contain only a single battery only a single door or cover must be removed or at most, removal of the screws that secure the base of the unit to the cover. For example, I have a Back-UPS 500 model BK500MC that has a metal door secured by just two screws that covers the battery bay and holds a battery in place. Removing those two screws gives access to remove the old battery and install the new one.

The Back-UPS CS 500 model BK500 is a plastic cased unit that has a plastic cover that has a ridged tab that just needs to be pressed in to allow the cover to be slid out to the side and off the unit. Once open, I have access to the positive and negative terminal cables, red for positive, black for negative. The batteries themselves are also color coded on the positive and negative posts to match, so it would be hard to make a mistake and reverse the polarity when connecting one of the individual batteries. By the way, don't ever do that, you could injure yourself and least of all, it may result in permanent damage to your UPS unit.

Once finished, put the cover or plate back in place and re-insert and tighten any screws that had to be removed and you are done. Plug your UPS unit in and it will begin charging the battery to a full state of charge to have it ready for the next brown out or power outage. On some Back-UPS units, you may need to run a manual calibration so that the unit will present an accurate estimated time remaining to APC's PowerChute software so that it can appropriately shut your computer down gracefully without suddenly running out of charge when it thought there was more left or shutting down prematurely when there is more than enough charge left over to run for a few more minutes.

A Happy UPS Is A Quiet UPS

Back-UPS unit plugged in with a good battery, quietly charging.  Hooray for no more alarm squeals!
Back-UPS unit plugged in with a good battery, quietly charging. Hooray for no more alarm squeals! | Source

How Do I Get My Back-UPS Unit To Calibrate The New Run Time?

On UPS units that don't have a built-in calibration function, wait approximately 24 hours for the UPS to charge the new battery and then load the UPS unit with something like a television that draws approximately 100-200 watts , or if you're brave enough to accept the risk, leave your PC and/or monitor plugged into the UPS while its connected to either a switched outlet or a power strip/surge protector, power on your chosen device and switch off power to said outlet or power strip/surge protector to force the UPS to run on the battery and allow it to discharge until it either shuts your PC down, if using PowerChute software, or until the UPS unit dies.

Note that deep discharging like this isn't recommended to be performed frequently and in fact APC themselves only recommends that it be done no sooner than 6 months at a time, annually being more preferred, since frequent deep discharges can shorten the life of the battery. Though it is worth noting, the older a battery becomes or is more frequently used (due to more outages/brownouts) it is worth running this at least once per year so that PowerChute can properly track the estimated run time so you don't get caught with your pants down so to speak when it believes you have more time left than what the battery can actually give.

Congratulations!

If you found this hub in search of finding a cheaper way or information on how to replace your dead APC batteries with another cheaper alternative, I hope you found it useful and that in the end it helped you save yourself some money or otherwise helped you keep an old or used Back-UPS unit from being discarded and wasting space in a landfill.

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    • jesimpki profile image
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      jesimpki 14 months ago from Radford, VA

      Thanks mechanicsguy, I hope this information was useful to you!