Electronics > Repair

car remote draing battery 20uA

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boo9:
I have put week or so new battery and it stopped working,  no LED after press, works after putting new battery in.

I checked and the remote is using 20uA when not pressed.

With battery removed, I have 15K resistance on battery terminals.
C1 (upper right corner) shows aroud 20K resistance.

Is C1 kaput ?

What should be the value for C1 ? 90nF ?

wraper:
Is that battery CR2032? Considering 220 mA/h capacity, with 20uA current it will last more than 400 days. Even if it have 10x lower capacity, it would last much longer than a week.

SeanB:
I would go for any value from 1uF to 47uF ceramic 16/ 25V capacitor there, whatever you have in that size or with that spacing that will physically fit in the space. Scrub the board with IPA and dry thoroughly as well, to get rid of the fluc residues. Check the switches are not leaking as well. The higher value cap will help prolong battery life as it will better decouple the supply as the battery ages.

It likely is the capacitor leaking, and as many of these remotes use a CR2016 to save thickness they often do not have much spare capacity to begin with. A CR2032 works better, but might be too thick.

boo9:
CR2032 it is.

54uA (micro) shows now. with my $5 meter

The reason I suspect C1 leak because couple weeks ago I had garage door remote with a leaking cap but then the LED was lit up slighly all the time,   the cap at the bottom, I replaced it with 90nF and problem (LED lit) went away. Should I be replacing the 90nF with something larger ?

SeanB:
100n, 220n or 470n that will fit, with a 50v rating will work there. it is there for bypassing, not anything else, and in this application the exact value is not critical. I have added 10uF 25V tantalums in some to get better battery life, they work till the battery gets totally flat and no longer has an open circuit voltage above 5V.

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