How do I prolong the life of my electric toothbrush's battery?
December 9, 2005 2:12 PM   Subscribe

My electric toothbrushes keep dying...

I love using electric toothbrushes, because they force me to brush for the appropriate time, and they do a pretty good job. My current toothbrush (an Interplak) is now at the state where it will run feebly for about 30 seconds, then stop. This is after about 5 months of use. My previous model croaked similarly after about 6 or so months, too.

My wife and I probably brush a total of 4-6 times daily (combined), so I don't think our usage is out of line. Is there something I can do to replenish my battery or, if I have to get a new toothbrush, prevent it next time?
posted by websavvy to Grab Bag (20 answers total)
What kind of battery do you use and what are your charging habits?
posted by SeizeTheDay at 2:23 PM on December 9, 2005

I bet you put it back on the charger after each time you use it. Don't do that. Also, because most battery chargers are as dumb as rocks, don't leave the device charging. When it tops off, remove it from the charger.
posted by majick at 2:26 PM on December 9, 2005

Response by poster: They have built-in batteries, and sit in a base that supposedly charges them automatically. I brush, and drop the thing back into its charger.
posted by websavvy at 2:26 PM on December 9, 2005

Just buy something cheap and replace the batteries yourself then.
posted by delmoi at 2:31 PM on December 9, 2005

It's probably a crappy NiCad battery that prefers to be run down all the way. Don't put it back in the charger until it's almost dead. I have a Braun 3d that's lasted 1.5+ years with no problem.
posted by Nelson at 2:32 PM on December 9, 2005

What Nelson said. That's why I asked what kind of battery you have. If you had a lithium inside, which I doubt, throwing the toothbrush back on the charger is no big deal. But with NiCads, the don't have very intelligent memories and their chargers don't have a trickle feature.

I use a Sonicare and I only charge the toothbrush once it indicates low battery and I completely discharge it (and recharge it fully) once every couple of months. Goto BatteryUniversity for more information regarding battery usage.
posted by SeizeTheDay at 3:29 PM on December 9, 2005

This is very interesting, I bought a battery-powered Braun Oral-B brush at least 6 years ago and it's still going strong. I can leave it off the charging base and it still works at full strength for another 3 or 4 days after. I guess I just assumed they were all like that. In my mind, the lifetime of this brush is what justified the initial cost and "refill" costs.

Anyway, it might be worth experimenting as majick and Nelson suggest. It certainly can't get effectively worse than 30 seconds.
posted by Mike C. at 3:41 PM on December 9, 2005

I use a Sonicare. It sits on its charger/base constantly, and I haven't had a single problem in over three years. I replace the head every two or three months.
posted by cribcage at 3:46 PM on December 9, 2005

I use a Sonicare and have used the same one for more than two years now without any problems whatsoever. And I leave it in the charging stand whenever its not being used.

By the way, Sonicare's suck at getting algae off fishtanks. Just in case you were wondering.

And you brush your teeth alot.
posted by fenriq at 3:53 PM on December 9, 2005

I bought a battery-powered Braun Oral-B brush at least 6 years ago and it's still going strong

My girlfriend gifted me with hers when her parents bought her a newer snazzier one a year ago and it's also still going strong. I put mine back in the charger after use as well. Perhaps they used to have better anti-burn logic in them and they realized that was bad for sales...

Make sure it's not just crudded up where the stick thing moves with old toothpaste, mine has at times slowed down marginally till I took the brush off and ran it under hot water while running.
posted by phearlez at 4:04 PM on December 9, 2005

Sonicare, 3 years, and as far as I can tell, still as good as the day I bought it. (But then, yeah, I don't brush 6 times a day.)

If you can pull it apart and put it back together, you could probably replace the battery.
posted by trevyn at 4:33 PM on December 9, 2005

Stop buying cheap electronic toothbrushes and just buy a Sonicare.
posted by xmutex at 5:34 PM on December 9, 2005

You should probably make sure that somebody is not draining the toothbrush battery via secret and naughty vaginal stimulations.
posted by soiled cowboy at 5:37 PM on December 9, 2005

Response by poster: "And you brush your teeth alot."

2-3 times per day is a lot?
posted by websavvy at 7:39 PM on December 9, 2005

Memory effect in batteries is a myth. The degradation of performance over time is caused by overheating, which is a result of poor charger design.

Nonetheless, I used to use interplak, and I had a problem with the cells failing as well (I went through about three brush bodies in the 90's). I think the charging circuit is just extremely poor, allowing the cells to overheat and degrade. For the interplak specifically, I think the solution is keeping the brush body off of the charger except for fixed periods of time. When you take a trip to the washroom around dinner time put it on the base, when you take a trip to the washroom in the middle of the evening (say one or two hours later), take it off the base. Something like that anyway...

There are many charging methodologies, and I'm no expert (though I am interested in learning more). Best to break it down into three types:
  1. trickle: A trickle charger - this is what I suspect the interplak has - just keeps charging the entire time the batteries are in the charger.
  2. timed: A timed charger assumes you have fully discharged the cells and charges for a fixed amount of time which the designers predict will be appropriate.
  3. smart: A smart charger actually determines when the cell is charged and turns off.
Both timed and smart chargers often have a trickle mode, but it is quite different from a dedicated trickle charger. A dedicated trickle charger has to be able to fully charge the cell, so the trickle just isn't that slow. In the other two types, the trickle only has to overcome the self discharge rate, so the trickle can be very slow (self discharge is why you can't store rechargeable batteries in a drawer for months and still expect them to work when you pull them out).

Also, a recent question: Are electric toothbrushes worth it? Linked to studies that seem to show that cheaper spin brushes, like this Braun/Oral-B are the only electric type that outperforms manual toothbrushes.
posted by Chuckles at 9:43 PM on December 9, 2005

4-6 uses daily might require a little longer charging time... Put it on the base when you start dinner, don't return it to the base after brushing before going to bed. You will have to see how it works for your own habits... I hope the point is clear though, if you don't understand I'm happy to clarify.
posted by Chuckles at 9:45 PM on December 9, 2005

Also, I should have been a little more clear... I don't think it matters whether you have lithium, NiMH or NiCd. The premature failures are more likely due to overheating than battery chemistry. That said, the different chemistries definitely have very different properties.
posted by Chuckles at 9:51 PM on December 9, 2005

I broke my Sonicare by pushing too hard on it and not just allowing it to brush by itself. First it got kind of slow like you describe, then the head snapped completely off.
posted by fshgrl at 10:49 PM on December 9, 2005

I've been using a Sonicare for over a year with no discernable problems. Great brush.
posted by smitt at 8:11 AM on December 10, 2005

If the batteries are dead and sealed inside the unit, if you know someone handy with a soldering iron, they are likely replaceable. As with most rechargeables, caution needs to be exercised during replacement, they can dump enough current through a short to become dangerous.

/me, being the cheap bastard I am, did this with my old philishave tracer. Managed to get like 10 years total out of that thing, only replaced the blades twice. :-D
posted by shepd at 9:46 AM on December 10, 2005

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