In this post, we will show what was necessary on how to get access into the BR24BP battery pack for APC’s BackUPS RS/XS series of battery backups. Read more for additional details, caveats and some good to know general informaton on how you can replace the stock batteries in the battery pack with your own batteries to save money and time.
BIG MONSTEROUS LEGAL DISCLAIMER: This information is provided as anecdotal as-is information. It is recommended when working with electronic components to replace the defective component with a component of the same type, model and rating. Battery backups are no exception to this rule and as such we recommend that you follow the exact ratings as specified on your UPS, even if they differ from the information on this site. When in doubt, go with a 1-to-1 replacement, or better yet, purchase a replacement battery pack from APC directly. By following the steps in this guide, you indicate that you can not sue firestorm_v1 or those of us at YourWarrantyIsVoid.Com if you burn your eyebrows off or cause damage to loved ones or property, etc..
Now that the legalese is done with, let’s talk about this a bit.
Ever since the dawn of time, or at least the dawn of the computer age, mankind has been faced with one monsterous problem: How to keep the computer running when the power goes out. Even in the 21st century, we are still not immune to the power failures, surges and brownout/blackouts that plague our planet’s power grid. The solution was to use uninterruptable power supplies (UPSes) also commonly called “battery backups” to keep the juice flowing, even though the power from the electric company had ceased. The idea was that power would be stored in batteries and would be used through specialized circuitry to recreate the line voltage that our beloved machines needed to operate. The idea was a grand saviour to the information age and since then have saved countless months of uptime loss, unavailability and other such lack of availability.
However, with every great solution is a thorn in its side. In our case with the batttery backups, the thorn is the batteries. Every now and then, through regular use and standby charging, it becomes necessary to change them out. Usually this cost is a lot less than just buying another battery backup and is a preferred method to keeping old but still usable UPSes out of the trash can. In my specific case, I have an APC Battery Back-UPS XS 1500 and it has served me extremely well through the years. Unfortunately an extended power failure had knocked it and the addon battery pack, BR24BP out of comission and had rendered the UPS useless.
Pior to just ripping the face place off of anything, even if it pisses me off, I perform a good bit of research using Google and Yahoo to attempt to find disassembly instructions for something. In the case of the battery backup’s battery pack, I had nothing but a bunch of forum posts with people looking for the same details. Unfortunately no solution was to be had so I started investigating on my own and was ultimately successful. This writeup is a testament to those findings and a howto for anyone that was as lost as I was with trying to find a way in.
This is a shot of the BR24BP in all it’s glory. Despite it’s innocent looking exterior, it’s a mofo to get into. With no visible way of getting in, I set out with my metal screwdrivers and started prying like a madman. Eventually, I was able to get the white front cover off and the secret to this beast was unlocked.
(The grey piece on the back was held together much in the same fashion, pardon editor’s fault for the back showing ajar. ) In this shot, we learn something important. The front is not held on by any fancy method, locking mechanism or other trickery. It is held to the front of the battery backup by means of a pair of snaps. One at the top of the cover pointing down, and one at the bottom cover pointing up. It would be almost trivial to modify the case so that you could get into the battery box at some point again to do a second swap out fo the batteries.
Here is a shot of the front cover. The back cover is identical to this except it is grey and has a hole for the power cable to go through. It could be theorized that the ends of the snaps are sliced to prevent from someone gaining access to the innards of the battery box. It could also be theorized that a quick session with a Dremel could prodice a hole with which to pry up on the snaps to gain access in the future without having to pry the case open like your life depended on it.
This is a shot of the rear cover after being pried off. The thin holes at the top and the bottom are the holes for the snaps. Once finally freed of both the front and the rear faceplates, we are left with the battery box and six phillips screws from victory.
In this shot, we can finally remove the only screws in this battery pack’s setup and pull off the cover to reveal the batteries inside. One special note about the covers. They are omni-directional (Editor’s note: omni-sidal seemed to not be a word. ) meaning that the “left” side could easily be the “right side”. The only thing that determined direction was that the indentation for the pedestal foot was at the bottom (pointed towards you if on a table) and that the cord came out of the “back”. Aside from that, it was anyone’s game.
(I apologize for the blurriness of the full-size picture, just use the thumbnail for general positioning data.) Behold, here is the batteries in all its glory. Keep in mind that my top two batteries are “poofy” and need to be replaced. The bottom ones, are not poofy so will get taken to a battery place to get charged and tested.
Before we get into wiring diagrams and all that nonsense, please make sure you use the right battery. These are 12 volt, 3.4A batteries. CSB# HR-1234W-F2 and are the Sealed Lead Acid (SLA) type. IT IS CRITICALLY IMPORTANT THAT YOU USE THE SAME TYPE AND RATINGS OF BATTERIES IN YOUR UPS. EXTENDING YOUR UPS MAY GIVE YOU ADDITIONAL UPTIME BUT WILL CAUSE YOUR ADDITIONAL UPTIME TO FAIL AS THE CHARGER CIRCUIT CAN NOT HANDLE THE EXTENDED CAPACITY! (Can I say this enough?) If you are in doubt about whether or not you have the right battery, take one from the pack to an Interstate Batteries or a Batteries Plus and get four just like it. Bring them home and wire up as covered below.
Wiring it all up:
The interesting thing about this pack is that despite the link that I found for APC, this is actually a 24VDC system, not a 12VDC system as advertised. Granted, the batteries themselves are 12VDC, but they are hooked into a 12x2x2 array meaning that the batteries are connected in series (to make 24VDC) and then are connected in parallel to another pair connected in series. The entire thing ends up being a 2x 24v array as shown in our next picture:
Ok, so let’s review this hookup. The umbilical cord that goes to the main BackUPS is in my hand. For now, ignore the little yellow wire. It has nothing to do with our hookup at the moment. Clockwise from top left, we have the UL (upper left) battery, UR (Upper Right) battery, LR (Lower Right) and LL (Lower Left) batteries. The umbilical has two positives and two negative leads on it. WHEN HOOKING UP BATTERIES, YOU MUST OBEY THIS IMPORTANT RULE: AT NO TIME WILL THE POSITIVE AND NEGATIVE OF THE UMBILICAL BE ON THE SAME BATTERY!!! THIS WILL CAUSE AN EXPLOSION AS THE 24V BATTERIES TRY TO (AND SUCCEED) OVER CHARGE THE SINGLE 12V BATTERY! That being said, connect one of the RED wires to the positive terminal on two batteries and connect the BLACK wires to the other two batteries’ negative terminals. At this point, all four batteries should be connected with one connection from the umbilical. Connect the BLUE wires from the positive battery’s NEGATIVE terminal to the negative battery’s POSITIVE terminal. In essence, you have created two 24 volt battery packs made of UL and UR, and LL and LR respectively.
Now, back to this little yellow wire (and the 80A fuze) This wire acts as a “Sense” for the battery backup to determine the battery pack’s overall health. The wire has a resistor shrinkwrapped inline with it and should not be tampered with. Doing so may adversely affect the UPS’s operation.
It’s been fun dissecting this battery pack however it was hard as hell initially. APC does not make it easy to pry open the front/back of their UPS battery packs. I’m hoping that someone aside from myself finds this information useful as it was not easy obtaining it. If you have any information on where to get good replacement batteries, or you wish to share your experience, feel free to fire back at me in the comments section.
Until the next post, happy hacking!
Readers Derek and Shaaz commented concerning the resistor that was inline on the yellow lead of the power cable. After performing some investigative research (edit: I tore off the shrinkwrap), I have found that it is a 1% tolerance metal oxide film resistor. The resistor color code is Red, Black, Black, Red, Brown which indicates a value of 20 ohms with a tolerance of 1%. The tolerance is key as I am still of the opinion that this is how the APC backup monitors the battery level and is able to determine the level of power left. I would not suggest using a standard resistor instead of this 1% tolerance resistor as this will affect how long the UPS thinks it has on charge remaining.
Reader “Steevo” wrote in to catch me on a critical error in regards to this resistor. M initial calculations were incorrect, the value of this resistor is not 20K ohm, but rather 20 ohm, Please make sure you use the correct resistor if you ever need to replace it.
UPDATE: More details about the power connector from the BBU power pack to the UPS
After requests for information in regards to the power pack’s connector, I realized that I had made a serious oversight. I had not documented the power connector that connects the battery pack to the UPS body. With this in mind, I took some more pictures of the connector:
The power connector has four pins holding the strain relief on. After getting the pieces pried apart, the end connector slides off and you can then see the wiring on the inside. Barring that, I went ahead and was able to extract the outside case off of the three spade connectors as shown here. In order to extract the three spade connectors, you will need to take a long sharp screwdriver and pry the plastic clips holding the spade connectors down.
Here’s the connector with the spades having been successfully extracted:
Keep in mind that the plug orientation is not certain as I’ve reinstalled the UPS and it’s buried under the desk. The red mark on the connector jacket is there for orientation purposes, but interfacing with the UPS may require that the black wire is on the left, and the yellow wire is on the right.