Medela Breast pump no longer works with batteries

[Andrewcampbell2003]

Dear All,

Im a long time lurker - just wanted some help as I am not a EE.

My wifes Medela Maxi Swing breast pump will only work on the mains adaptor and no batteries.

I have checked the batteries (AAA x 6) and they are reading 8.4 Volts and the mains adaptor is reading 12 volts.
There is sometimes an audible click when the mains is connected.  I have checked and the power is getting to the board, with the mains running in parallel with the batteries with some sort of Diode.

I did watch Daves video about this but this one is a slightly different model with different issues.

According to Medela there is something wrong with the pump but I cannot return it as we have moved to Brunei:
http://www.medelalibrary.com.au/f.ashx/troubleshooting-guide-2014.pdf?dl=1

If anyone can give me some advice or tips would be helpful!

[jh15]

Just stick the baby on the emitter. They are made for that (lips).

[Andrewcampbell2003]

I'm afraid we can't because the wife isn't at the base all the time so we need a collector.

[VK5RC]

A quick /dodgy 'work around'  :how about a 12v power pack (Li whatever)  and a plug to fit in the power pack socket?

[Andrewcampbell2003]

A quick /dodgy 'work around'  :how about a 12v power pack (Li whatever)  and a plug to fit in the power pack socket?

I just checked a lipo I have lying around and it's 12v so I will try and hook that up as a containment.

Is it possible that the batteries aren't delivering enough current?

[eKretz]

Have you tried new batteries? 8.4V for 6 AAAs seems a bit low. Maybe under load it's sagging further and it's not enough. Some devices have a very low tolerance for low voltage.

[CJay]

Have you tried new batteries? 8.4V for 6 AAAs seems a bit low. Maybe under load it's sagging further and it's not enough. Some devices have a very low tolerance for under voltage.

It does, especially if they're not under load.

Could just be that the motor is worn out and is drawing too much current as well.

Definitely worth sticking the multimeter on the motor terminals when trying to start it on battery.

[Seekonk]

It may be the battery style.  I have a LED flashlight that will not work with one brand of batteries.  The battery holder has plastic that prevents contact when the battery is reversed.  The battery's positive end has a projectile (I won't take a cheap shot and use the other word) that is too fat or short to fit in and make contact.  Contact points on many items tend to be cheap and oxidize easily.  Have you tried roughing them up with the end of a screwdriver?

[eKretz]

That's a good thing to check too. Terminals seem to oxidize/corrode really fast on some things these days. Definitely use good name brand new batteries to test also. I doubt that the motors will be drawing too much current, the load is fairly light and the pump brand is a pretty reputable one (I remember from when mine was using a pump for our little ones).

[Andrewcampbell2003]

Hey guys thanks for the replies, I just want to clarify that the pump is 6 months old and had previously worked on batteries no problem.  I checked the voltage and the voltage I mentioned earlier were on the PCB itself so the power is getting from the batteries to the board just doesn't seem to be turning it on.

I haven't tried to try to hook up the lipo yet as I'm having trouble finding a connector to connect to the power supply connector.  Do lipo usually have low voltage protection circuits onboard?

[VK5RC]

I use a Panasonic 18650 cell as my 'standard'  lipo,  they have a low voltage cut off circuit,  but quite a few don't I think, 
What,  a young child / busy career and not much time!  HIHI,  It does get better. All the best. 

[Andrewcampbell2003]

ok guys quick update - so I bought a connector and I was able to get the lipo hooked up for a few minutes until it died again.  Wouldn't turn on when powered from batteries or mains.   I checked the fuse - low and behold it was finally blown.  I have since hot wired the fuse until I can get a replacement fuse in place.  I tried to find a replacement on element 14, can anyone tell me if this is a suitable replacement? I think it is a 402 (see attached) does it matter if the voltage is rated at 35v DC??
http://sg.element14.com/te-connectivity-raychem/0402sff150f-24-2/fuse-smd-0402-1-5a/dp/1843785

[CJay]

I think you are wrong that it's 0402, that's a tiny part, 1mm long and 0.5mm wide.


There's a couple of spots of what look like corrosion on the gold finger edge connector, can you clean that up and whatever it connects to?

[metrologist]

Make sure the mechanicals are clean and free, then lube. I seem to remember they get gummed up and stiff.