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Does battery self discharge when connected

Does battery self discharge when connected

(OP)
I am an electric engineer, and I read about battery self discharge phenomenon. I was wondering whether a battery self discharge rate is the same when it is unconnected (i.e. in storage) and connected (i.e. when it is plugged into a device and being discharged "normally"). In other words, when I calculate battery life time for a product, should I take add the rated self discharge of a battery to the general current calculations or not? And also-is the answer similar to all types of battery?

Thank you in advance.
Udi

RE: Does battery self discharge when connected

Yes, absolutely. That's why batteries have shelf lives, and each battery chemistry is different, since different electrolytes and materials are involved.

Your self-discharge current is usually very low level, and would likely alter the lifetime calculation by less than 1%

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RE: Does battery self discharge when connected

It depends on the device, some devices draw power when they're off.

I've also designed things that draw less current than the battery's self discharge rate making the battery the major consumer.

If the device has a real power switch disconnecting the battery entirely then the self discharge is only a function of the battery chemistry and the ambient.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Does battery self discharge when connected

(OP)
Thanks for your replies,
My question is really: does the battery self discharge at the same rate when it is being drawn from, or does the self discharge only happens when it is disconnected?

RE: Does battery self discharge when connected

Ah. Different question...
It's the same since it is really a corrosion/chemical aging process that still occurs during usage.

Keith Cress
kcress - http://www.flaminsystems.com

RE: Does battery self discharge when connected

Again, it's probably irrelevant whether it does, or doesn't, since the load probably draws way more current that the self discharge.

Think of the self-discharge as a parasitic load in parallel with the external load.

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RE: Does battery self discharge when connected

The discharge rate depend in some factors. Temperature,chemistry, age, SOH & etc. when you connects the battery to a device you must be counts on the leakage of the device too. Most of the device have a considerable leakage current.

Hadoo
Head designer at www.lianinno.com

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