# What does C5A mean and how do I interpret this datasheet?

#### koya-47

Joined Oct 15, 2021
20
Hi, I'm trying to source new rechargeable batteries to replace dead ones in a tracking device. I was kindly provided with the datasheet by the manufacturer (attached). I have two questions regarding the datasheet.

For reference, the batteries have " 3.7V, 800mAh, 2.96Wh" printed on them.

1. What do the values 0.2 C5A, 1.0 C5A and 2.0 C5A under section 2 of the datasheet imply? From what I could find online it looks like it means the battery will supply 0.2 x 800mAh, 1 x 800 mAh and 2 x 800 mAh continuous current respectively over 5 hours at their respective conditions, is this correct? If not please explain it in a very basic manner as this is all very new terminology to me and Google's been a bit confusing to a newbie.

2. The manufacturer told me the following:

"Please note the batteries must have
1. Peak pulse discharge current and recommended duration
2. Peak continuous discharge current"

I've seen these values clearly stated on datasheets for other batteries but they also use notations like 0.2 C, not 0.2 C5A like on this datasheet. I'm struggling to understand where to obtain these values on the attached datasheet and if any conversion is needed between C and C5A. Any idea on where these values are specified in the attached datasheet?

Thanks!

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#### sagor

Joined Mar 10, 2019
695
1C5A is a standard measurement of the battery capacity, in this case 800mAh. The "5" is for 5 hour ratings where applicable.
So, the rating of 800mAh is actually at 0.2C5A. meaning it will provide 20% of the rated capacity (160mA) for 5 hours before the voltage drops to the final terminal voltage of 2.75V (according to datasheet) Farther down, it states 1C5A discharge (800mA) will last 57 minutes at lease, hence the 1C. Notice that is 5 times the current but 1/5 the time as 0.2C5A.
Maximum charging rate is 1C5A, meaning maximum charge rate of 800mA is allowed.
Maximum discharge current is 1600mA (2C5A - 2 x rated capacity rating) but I don't think the 5 hours applies in this case, it is just a maximum for that battery capacity rating. Confusing for sure...

#### Ya’akov

Joined Jan 27, 2019
5,659
To state what @sagor said slightly differently for possible clarification…

C5A, as a standard, can be converted to a number when the rated capacity of the battery is known. The advantage of using C5A instead of “800mAh” is the addition of a specific discharge rate. This is because a battery will not deliver any arbitrary combination of current over time that adds up to the mAh rating.

If you discharge a 1Ah battery at 1A, depending design and chemistry you may or may not be able to get 1Ah of current from the battery. Some combination of current and time will get you the 1Ah, others will not. So, the C5A rating was standardized so batteries could be reasonably compared.

As stated, this is the 5 hour rate that will provide the specified capacity of the battery, that is, how much current can I draw from the battery while still getting what i thought I paid for?

Once this is a number, it can be used to specify other things, like charging rate. The time component in the “C5A” isn’t important directly to that specification, but the number it represents is being used to talk about something else.

#### koya-47

Joined Oct 15, 2021
20
Thank you both very much! This makes understanding the C5A notation much easier!

Any idea on the second part of the question? I.e. which value in the datasheet is the peak pulse discharge current and which is the peak continuous discharge current? (I assume the latter is 2C5A from the datasheet but I'm not sure how to obtain the pulse discharge current).

#### Ya’akov

Joined Jan 27, 2019
5,659
It appears the built-in protection circuit can be activated by 2A for 7.2ms in the worst case. I am not sure why there is such a broad range. It could be that the board can programmed for that range, and they aren't saying what this cell is set for.

Given the maximum discharge rate of 1.6A, 2A wouldn't be outrageous.

#### koya-47

Joined Oct 15, 2021
20
It appears the built-in protection circuit can be activated by 2A for 7.2ms in the worst case. I am not sure why there is such a broad range. It could be that the board can programmed for that range, and they aren't saying what this cell is set for.

Given the maximum discharge rate of 1.6A, 2A wouldn't be outrageous.

View attachment 262994
Thank you very much! This is a huge help!