# maximum practical current flow from a battery

Discussion in 'Electronic Basics' started by ted, Jun 8, 2007.

1. ### tedGuest

In the interests of minimizing weight, I'd like to use a coin battery
in my project. Unfortunately, my project is going to need about 2mA,
and I see from the data sheet of the Energizer CR2032 that its
"continuous background drain" is a mere 0.19mA. However, it also says
that 6.8mA are possible as a "pulse drain", and if I read this
correctly, a "pulse" is a period of two seconds. As these things go,
what can I expect from such a battery if I draw my 2mA for a period
of, say, ten seconds? Would I be pushing the envelope there, or not
really?

2. ### John PopelishGuest

As long as your pulse is smaller in magnitude than the one
specified, I think it is safe to extend the time and lower
the current, as long as the current, time product is not
larger than the specified pulse rating.

Since the specified pulse rating is 6.8 mA times 2 seconds,
for a product of 13.6 milliamp seconds, you should be safe
pulling 2 mA for 13.8/2= 6.8 seconds. However, as the
current approaches .19 mA, that time extends to the life of
the cell. I also suspect that this surge rating includes
lots of rest, so that the average current stays well below
the .19 mA continuous rating. In your case, that means that
for every 2 second pulse, there is a lot more than 20
seconds rest time before the next pulse, to let the
chemistry catch up.

In the final analysis, you should run a load test on a few