Back-UPS BX750MI Battery Replacement

[Buadhai]

After a lot of email go around with Schneider tech support they said:

" This unit does not have a user-replaceble battery function so battery replacement is not recommended but a whole unit replacement instead in case of battery failure."

On the other hand, they sell a replacement battery for this unit here:

https://www.se.com/th/th/product/RBC17/apc-replacement-battery-cartridge-vrla-battery-9ah-12vdc-2yea...

So, can I replace the battery, or not?

[Teken · Accepted solution]

Yes of course you can replace the battery yourself. How does the APC guy think they got the battery inside the first place?!? 🤦‍♂️

You can by any CSB branded 12 VDC 9AH high rate cell. It doesn’t have to be a APC rebranded cell.

Questions Ask . . . 👍

[Buadhai]

Will this one work: 

12V 9AH UPS CSB BATTERY HR1234W F2

(The Thai script just says it has a one year warranty.)

[Teken · Accepted solution]

Yes, perfect drop in replacement. 👍

[Buadhai]

Sorry for the continued confusion. I watched a YouTube video to learn how to replace the battery:

https://youtu.be/gRI50MITPio - How To Replace Battery UPS APC BX750MI-MS

The presenter used a CSB GP1272 F2 12 Volt 7.2 Ah (15x6.5x9.5)

So, should I use that or the CSB HR 1234W F2  12v 9Ah (15x7x10)

They seem to be slightly different in size. They are about the same price.

[Teken · Accepted solution]

The original unit comes with a 12 VDC 9AH cell which offers longer operational runtime.

The only reason anyone buys a 12 VDC 7.2AH cell is because it’s cheaper.

Both are the same physical outside dimensions regardless of what you read on the APC website.

Questions Ask . . . 👍

[Buadhai]

Thanks for taking the time to be so helpful. 

[Buadhai]

Reply from Schneider:

"If your UPS is experiencing issues due to deteriorating batteries, you can replace the battery with a new one.

"However, it is advisable to have the replacement done by a skilled dealer or service center to avoid potential "damage to the device.

"Remark : It is not recommended that customers replace the battery themselves.

"Best Regards, 

"nnnnnn nnnnnn
"Primary Technical Support Engineer l Customer Care Center"

[Teken]

If you follow the steps outlined in the video you will be fine. There is only one safety precaution that you need to follow and that is to insure the AC plug is disconnected from the wall outlet. ☝️

As seen in the video there is only four screws to remove. Than gently push in the front bezel cover (FIC) retainer (Force Retaining Clip) so the two halves can be separated.

Lastly, if your unit includes a data port to connect to APC Power Chute Software. Confirm if there are the following options available and present: Battery installation date, self test, battery calibration.

If all three are present insure you update the battery installation date. Follow up with manually initiating a Self Test and let pass and allow the battery to recover to 100% SOC (State of Charge).

Complete the process by manually initiating a battery calibration with at least 30% attached load. Let the process complete and allow the battery to recover and recharge back to 100% SOC.

If none of them are present nothing to worry about for now.

Questions Ask . . . 👍

[Buadhai]

Thanks for the guidelines. I use NUT on a Raspberry Pi rather than Power Chute (not available for Mac). Of the three options you cited, NUT only has self test.

Before I buy a new battery I will do the brain dead procedure once more. Last time I did it, the Battery Needs to be Replaced alert went away and the UPS performed fine for over a month and passed the self test. A very brief power outage caused the Battery alert to come back.

[Buadhai]

I ordered the battery. While waiting I decided to try a few things:

• Attempt to manually calibrate the current battery. It showed 98% charge (battery.charge: 98). I put on a 29% load and pulled the plug. The UPS immediately died.
• Try the Brain Dead procedure. I disconnected the battery, removed the load and made sure the UPS was not plugged in.
• Tried manual calibration again. The battery showed 98% charge, but the UPS instantly died when I yanked the power.

I'm not confident that a new battery will fix this.

[Teken]

Outside of the unit being defective everything points to a expired battery. 

Questions Ask . . . 👍

[Buadhai]

If you overlook my fat fingers, installing the battery was not too difficult. I ran the self-test which it passed:

ups.test.result: Done and passed

I'm letting the battery charge now. After 30 minutes it seems stuck on 97%

In another 30 minutes I will do the manual calibration.

I checked the voltage on the old and new batteries. I realize that without a load this doesn't mean too much:

Old: 13.16

New: 12.62

[Buadhai]

Finally, success!

It actually took three hours for the battery to go from 97% to 100%.

I used a 33% load to do the manual calibration. The Raspberry Pi shut down at the appropriate time. The Battery Runtime seems to be reasonably accurate.

Right now with an iMac, Raspberry Pi and a router the load is only 12%.

Thanks again for all your help and support. Aside from getting the UPS back, I learned a lot for which I am grateful.

[Teken]

If you had the proper test equipment you will find the old battery has a very high internal resistance vs the makers specification data sheet.

Typically a CSB branded battery will be (approximately) 18 milliohms. As you stated the resting voltage is only one indicator and once a load is placed on the cell it would fail to provide any meaningful operational runtime.

The APC Self Test performs a very crude load test and compares it to a defined table. As you saw it failed to pass this test because it can’t sustain the minimum load required to keep the unit operational.

Lastly, the specifications only indicate a 8 hour recharge time vs the charger power output.

As such allow the system to recharge the cell for 72 hours before manually initiating the battery calibration with at least 30% load.

Ensure the battery installation date is entered if available to do so. As this resets all charging reference tables if applicable.

Questions Ask . . . 👍

[Buadhai]

Three days after I replaced the battery the UPS has started generating alert messages like this:

• UPS apcups@localhost battery is low - battery.charge: 100
• UPS apcups@localhost battery needs to be replaced - battery.charge: 100

I'm not sure why or what I should do about it.

Note that the actual message from the UPS is before the hyphen. The battery charge phrase is added by the shell script that deals with UPS alerts.

[Teken]

You never answered my previous question which is has the battery installation date been updated (IF) available?!? 

This needs to be done as that will reset the internal counter. If NUT doesn’t have this option than you need to connect the system to a Windows computer running APC Power Chute Software.

As stated earlier the steps after a battery replacement are critical which are: Update battery installation date, Self Test, Battery Calibration with at least 30% connected load.

A Brain Dead reset does not circumvent the need to do all the above in order. 

Questions Ask . . . 👍

[Buadhai]

I do not have access to a Windows computer, so there is no way for me to reset the battery install date. Given the huge number of Mac computers out there it is quite shocking that they don't have a MacOS version of PowerChute

But, I should note that when Schneider sent me this replacement unit they did not set the battery install date nor did they do a calibration, as evidenced by the completely out-of-whack battery runtime data which was over 3000 minutes.

Previously you wrote:

"Confirm if there are the following options available and present: Battery installation date, self test, battery calibration.

"If none of them are present nothing to worry about for now."

I replied:

"Of the three options you cited, NUT only has self test."

[Teken]

My statement about nothing to worry about for now relates to the fact older systems do not have this option. 

As such nothing can be done by the end user. You’ll need to find someone who has a Windows computer system and have them install PCSS / PCPE.

You’ll probably find one of the software packages doesn’t show the battery installation date as being available. As this is dependent upon the firmware installed on the unit.

Given the above you will find this is treated as a soft fault or hard fault error. A soft fault error can be ignored by the user even though that’s not best practice.

A hard fault error will cause the system to stop functioning as expected in different ways depending upon how the vendor wants to force the end user to address the problem.

Questions Ask . . . 👍

[Buadhai]

This is mostly for people who get here as the result of some sort of search.

I was somewhat concerned at my inability to reset the battery date. So, I wrote to Schneider to ask if that would cause problems down the line. Here is their response:

"The date of battery installation does not affect the operation of the software in other functions.
However, I have encountered a case where there may be an email notification to change the battery if set. However, it will not affect the operation in other functions."

Not 100% clear, but at least I can now rest easy.