Maximum safe discharge rate for LiPoly batteries

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MJHanagan
 
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Maximum safe discharge rate for LiPoly batteries

Post by MJHanagan »

I am designing a new project that requires some hefty power levels to drive a series of IR emitters for 30-60 minutes at a time. I could consume up to 2000 mA at 3V which would be a discharge rate of about a 1C for a 2500 mA-hr battery. I would prefer to do this with a LiPoly battery rather than a SLA battery (which can handle very fast discharge rates but are bulky).

Do you have a recommendation for a maximum DISCHARGE rate of the LiPoly batteries you sell?

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adafruit_support_bill
 
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Re: Maximum safe discharge rate for LiPoly batteries

Post by adafruit_support_bill »

There are links to the data sheets in the product description page for each cell. These will show the maximum recommended discharge rate for the cell.

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MJHanagan
 
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Re: Maximum safe discharge rate for LiPoly batteries

Post by MJHanagan »

adafruit_support_bill wrote:There are links to the data sheets in the product description page for each cell. These will show the maximum recommended discharge rate for the cell.
I tried reading the spec sheet but I was confused by the two references to discharge rates:

(1) In Section 3 on page 2 they show a "Standard Discharge Current" specification of "0.5C5A" (where the 5 after the C appears to be a subscript). In battery parlance a "C5" usually refers to discharging the battery over a 5 hour period. And with the 0.5 in front would imply 50% of a C5 rate, so why not just express this as C10? If this is a 2500 mA•hr capacity battery then C5 is 2500/5, or 500 mA, so 0.5*C5 would then be a maximum discharge rate of only 250 mA.

(2) In Section 8.3.2 on page 7 it reads "Discharging current must be lower than (or equal to )2C5A" which would imply a maximum discharge current of 1000 mA (again assuming the C5 means capacity/5).

And, these rates differ by 2X. Is one supposed to be a "Maximum" and the other a "Design" specification?

In addition, in Section 3 they list the Maximum Charge Current as "1C5A" which would imply a maximum charging current of 500 mA (this is lower than your stated maximum rate of 1200 mA). Also in the same section the "Standard Charge Current" is listed as "0.2C5A" which would imply a charging current of 100 mA (this is lower than the charging current of your V1.2 LiPoly charger #259).

But if the "C5" is some type of typographical error and what they really meant was just "C" then the 0.5C would imply a maximum discharge current of 1250 mA in the first specification and 5000 mA for the second specification. A standard 0.2C charging rate would work out to be 500 mA which then aligns with the V1.2 charger current. Or do they really just mean "C5" so 500 mA? Quite a large range in how one might interpreter the specification sheet.

Could you help clarify how to correctly interpret their specification sheet?

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adafruit_support_bill
 
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Re: Maximum safe discharge rate for LiPoly batteries

Post by adafruit_support_bill »

(1) In Section 3 on page 2 they show a "Standard Discharge Current" specification of "0.5C5A"
The standard discharge current is 0.5 times the capacity. For a 2500mAh cell, that would be 1200mA.
(2) In Section 8.3.2 on page 7 it reads "Discharging current must be lower than (or equal to )2C5A"
Similarly, the maximum discharge current cannot exceed twice the capacity. For a 2500mAh cell, you must not exceed 5000mA.

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MJHanagan
 
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Re: Maximum safe discharge rate for LiPoly batteries

Post by MJHanagan »

Ah, so the "C5" was a typo in the spec sheet! Thanks for the clarification.

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Re: Maximum safe discharge rate for LiPoly batteries

Post by adafruit_support_bill »

Probably just a translation issue.

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