10 years, 5 months ago.

KL25Z on 3V coin cell


I just put a coin cell holder to the back of a KL25Z and put a 3V battery into it. Nothing happens. Board stays silent. I checked continuity and there doesn't seem to be any between the - and the two + on the board. Am I missing something?


I had to add a thin layer of solder where the back of the battery contacts the board for it to work reliably.

posted by Jerome Campbell 07 Nov 2013

Already tried that: negative.

posted by Boris Adryan 07 Nov 2013

4 Answers

10 years, 5 months ago.

Put the battery in and start measuring the voltage. One thing to bear in mind is the capacity of the battery, its ability supply the demanded current. If you circuit is demanding more than the battery can supply the voltage will drop and nothing will work.

10 years, 5 months ago.

Thanks guys. Unfortunately, even with a fresh battery and just blink, it doesn't work.

At least I know not the problem is at my end. Previously, I had assumed a 0-ohm bridge would have to be removed somewhere or something like that.

10 years, 5 months ago.

Hello Boris, Which board revision do you have (see small sticker on backside of board)? Schematics for RevD and RevE can be found here: http://www.freescale.com/webapp/sps/site/prod_summary.jsp?code=FRDM-KL25Z. You should be able to measure voltage on J4 pin 1. Do you have a multimeter at hand?

To rule out the obvious: did you insert the battery with the right polarity up?

9 years, 6 months ago.

FYI: Rev E board has a battery protector diode D7 that is _unpopulated_, so soldering the battery holder is not enough from now on! You can do a wire or 0ohm temporary - if you're quite sure not to leave the battery in while using the USB cable. (Based on the schematics you should populate a MBR120VLSFT1G)

Messed a few hours with that, hope this answer will save some of you from this!

(This diode was part of D1 on Rev D, it only affects Rev E)

(If you're looking for a battery holder this one seems to be a good choice: KEYSTONE 3003 - http://hu.farnell.com/jsp/search/productdetail.jsp?sku=908654 - they come in packs of 5)