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Help with fixing Waterpik(rechargeable)


New Member
Hi all!

I have a rechargeable waterpik that isn't working. Upon further inspection when opened it seems that the 2.4V battery just isn't holding the charge. (An extremely common problem it seems from user reviews)

What i want to do is bypass this battery and use an old cell phone charger that i have at my disposal. Inside this unit there is a small DC motor(no rating)
that drives a gear that seems to push the water up to the tip. I've checked the load on the motor which draws almost 1A and coincidentally that is also the current being used on my old cell phone charger.

The only difference is the charger output is 5V. I honestly don't know much about motors in general but have read that alot of them will operate in the 2.2V to 5V range.

When removing the battery and plugging in the original Waterpik charger, the voltage coming in is 3.7V (3V output 100mA)with a diode directly across the motor(protection?)

Can i assume that 5v should be fine to operate this motor without any risk of
burning it out?



If you're worried about damaging it then stick a couple of 1N4001 diodes in series to drop the voltage by 1.4V.


Or you can order a replacement battery from water pi. The only reason that these batteries die, In think, is that they sseem to be under incredible stress, for the short period of time that they are actually in use.


2.4 volts means 1.2 volys times two, there's likely very little to no charge control on teh charger just a flat constant current when it's on it's based, that's likley what kills the battery, once full it causes eleveated temepratures which degrade the battery chemistry over time. If they're NiCad batteries it's again no wonder the fail, short use and then back on the charge right away is the worst thing you can do to a Nicad Pack. Why not just replace the batteries? It's likley AA or AAA batteries in a plastic housing.


New Member
I would hesitate to convert a rechargeable unit like this to a line-powered device. The cell phone charger isn't built for the bathroom environment, and the Waterpik itself is only insulated for the 2.4V batteries that it contains.

I would replace the batteries.


New Member
Update! I played around with this unit a little more and using an external power supply determined i need about 3 JANTX5615 diodes to get close to the same voltage as the battery was giving out. When i finished my mod, and powered it up(using cell phone charger) it wouldn't turn on, it looks like the motor draws more current than 1A to initially turn on and once under load it falls to the +800ma range. Cofirmed this with the external power supply also. Oh well......SOL.


New Member
I had the same issue with the rechargeable waterpik and also noted it is a very common problem.
Someone on another forum suggested it was corrosion of the plug interface and to clean it with alcohol and a cotton swab.
I did that and it worked wonders. The bad design is that the water corrodes the contacts. It happened again just now and I sprayed it with some contact spray which restored the charging power. Bad design! Electric toothbrushes have used inductive couplings for decades. To avoid the problem I would put a QI coil in.

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