Anyone good with Microamps Milliamps etc?

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fluke
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Anyone good with Microamps Milliamps etc?

Post by fluke » Tue Mar 06, 2018 6:05 pm

So here goes.
Got a 4000 milliamp hour battery, with a constant 6 microamp drain on said battery.

How long before 4000 milliamp hour battery is dead.

If it makes any difference it is a 3.7 volt Li-ion battery.
Dave

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Re: Anyone good with Microamps Milliamps etc?

Post by desertstorm » Wed Mar 07, 2018 1:39 pm

You only normally want to take 95% of the rated capacity so 4000 x 0.95 is 3800mah 0.6ua is 0.0006 mA
3800 / 0.0006 = 6333333 hours which is 263888 days which is 722 years.
So what that tells you is that level of discharge is tiny for a battery of such a large capacity.
The self discharge rate is far higher so basically it will come down to how hot the battery is. As this has a great bearing on self discharge rates.

http://batteryuniversity.com/learn/arti ... _discharge
For the level of current you are supplying you don't need such a big battery. Nearly all the discharge is due to self discharge .
A lii-ion battery will lose 20% in the first month at 25 degrees c which will then reduce as the SOC drops.
Depending on the quality of the battery could be anything from 2-5 years. You might as well use a 2032 battery.
0.6ua is a small amount of current, what is it powering ? .
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fluke
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Re: Anyone good with Microamps Milliamps etc?

Post by fluke » Wed Mar 07, 2018 1:44 pm

Thanks Karl.

It's 2 18650 li-ions in parallel in a small power bank.

Thing I did not take into account was you should not discharge them past 2.5 volts.

I could put a small switch in there to turn it off.
Dave

"Duct tape is like the force. It has a light side, a dark side, and it holds the world together."
======
Cooper B5.5TDI wrote:I never rush a deep one....but she's handled about 14 inches so far with success

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Re: Anyone good with Microamps Milliamps etc?

Post by desertstorm » Wed Mar 07, 2018 5:36 pm

Batteries in parallel is never a good thing as the self discharge rate is a lot higher than a single cell. Effectively the cells charge each other due to differences in internal resistance and charge levels.A single cell on it's own would be better in this case
Gone but will never be forgotten
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fluke
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Re: Anyone good with Microamps Milliamps etc?

Post by fluke » Wed Mar 07, 2018 5:43 pm

Thanks Karl.
I know. But max single cell is around 3500mah,want the capacity to fully charge.

Other than that it's individual boards for charge and boost to 5 volt.
Then it get to big and messy.
Dave

"Duct tape is like the force. It has a light side, a dark side, and it holds the world together."
======
Cooper B5.5TDI wrote:I never rush a deep one....but she's handled about 14 inches so far with success

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