UPS Battery Resistance

[Anonymous user]

Dear All,

Our company sold a mount of UPS SUA1500I to our customer about 1.5 year ago.

Last week, they checked the resistance of those UPS and they saw the resistance is bigger more than 30% from the standard of APC recommended.

They gave the feedback to us. And they said those UPS battery need to be replaced.

But actually, we have ever never know about the resistance of ups battery, specially the standard resistance recommended from APC.

Can anyone can help me this standard form (for many APC UPS)?

And please help me the correct method how to check the battery resistance and know when battery need to be replaced (not depend on the battery led front of the UPS).

Please help me soonest because I can not find any information from google and we have to solve this problem for our customer soon.

Sincerely,

[BillP · Accepted solution]

I am not sure what you mean by battery resistance? I am not sure if there is a problem in translation but I need some clarification please.

Batteries typically last 3-5 years depending on usage -> What is the expected life of my APC UPS battery? | FAQs | Schneider Electric US

[Anonymous user]

Dear Ms. Angela,

Please take a look the attached file. It was sent from our customer. You can see the Battery internal resistance is difference more than 30% (red column) from standard (22 mOhm).

I really need the document to get the method and how to check this result for knowing is it true?

Please help me.

Sincerely,

[Anonymous user]

Dear Ms. Angela,

Any update with my problem?

In Vietnam, time is difference with US, about 11 hours. I think it is hard for you but please help me!

[BillP · Accepted solution]

Hi,

Are the batteries APC batteries and is there a problem other than the mOhm readings are different? Do the UPSes support their load properly?

[Anonymous user]

Dear Mr. Bill,

Now I just really need how to check the resistance of battery and standard resistance of battery from APC?

Please help me!

Sincerely,

[BillP]

This is not a value that we measure in relation to battery health. I've asked several top tier UPS support personnel here that deal with worldwide escalations and none of them have ever heard of this.

A battery is deemed bad by its capacity and voltage as well as voltage drop when a load is applied to it. We never talk about ohms in relation to measuring them or what it should be so I am not sure where this request is coming from or who told this customer to look at this value..

And sorry, yes there is a time difference, and I had to do training all day. Thanks Bill for helping.

[Anonymous user]

Hello phumd:

Battery manufacturers (some but not all) usually quote the internal resistance (more correctly termed "Impedance") for their batteries as "brand new, fully charged", and for a 7.2 Ah 12 volt cell such as used in the SU1500 I've seen values like 17 milliohms, or 19 milliohms (or 22 like this member's data table has). In my experience, having used a B & K battery tester for many years you will never be able to measure / achieve such low readings in the field with batteries that have been in service for awhile, or even brand new !

Eg :With Panasonic 12 volt 7.2 Ah cells which are premium ones I use, even with brand new batteries fresh out of the box (charged if they have been sitting for 6 months or more) I usually get readings of around 80 milliohms. I just pulled one out of a box that was dated 5 months ago and it measured 80% charge and impedance of 0.100 ohms or 100 milliohms.

When I test batteries from ups that have failed a self test and are flying the "batteries need immediate replacement" flag, the readings are usually in the 180 to 200 milli-ohm range.

Based on all this I would say the readings in that table show no sign of any cause for concern. Only when the UPS you sold fails its battery self test in 3 or 4 years will they need to be replaced !

[Anonymous user]

Dear Angela and Battman,

Thank you so much for your kindly helping.

But please take a look with this link:

Hioki 3554 Hand Held Battery HiTester, 3554 Hioki - at the Test Equipment Depot

This link above talk about an equipment for testing internal resistance of battery.

In my opinion, I think if just depend on the led "battery need to be replaced" front of the UPS we can not response timely, because we need a mount of time to replace battery, then we will dont have time for battery replacement planning!

Sincerely,

[BillP]

The UPS self test failed with replace battery LED indicator in most situations is designed to give you around a month's time before it fully fails. Sometimes though, it can fail without giving you that month's time depending on battery usage, age, environment, etc. You should probably start budgeting at the 2-3 year mark anyway to be safe.

[Anonymous user]

Thank you so much Angela!

From past to now, I just think when the replace battery led turned on, the battery must be replaced immediately.

Thank you so much for your kindly help .

Best Regards,