Could a battery charger be damaged more easily than the battery / device?

[kenny1999]

I've got an electric toothbrush which is rechargeable, it had been regularly used and charged for years until one day it didn't charge. I immediately thought that the toothbrush was failing but at the end of the day I found that it was the charging stand failing, the toothbrush was fine. But I am really wondering if a charger could fail more easily, compared to the battery / device?

 

[berkeman]

If you got years of service out of that product, I'd call that a win.

BTW, did you check the GFCI outlet that the charger is plugged into? Maybe it just tripped...

 

[Baluncore]

But I am really wondering if a charger could fail more easily, compared to the battery / device?

While connected to the supply, the charger will be operating under high voltage stress, even while it is not charging a battery, so the life of a little used product will likely be decided by the durability of the charger.

It is often the starting circuit of a switching supply charger that fails after some years of being connected. You will not know that it failed earlier unless it is unplugged, or there has been a power cut, when it will fail to start again.

In the ideal, the mechanism, the battery and the charger should all fail at about the same date. If that was not the case the design would be unbalanced and the initial cost would be higher than needed.

 

[russ_watters]

I was surprised recently that my electric toothbrush charger failed as well.

 

[DaveC426913]

I've replaced my 14V drill de Walt battery charger several times, each time after it got sprinkled with a very light dusting of rain. (just a mist of splash, not rainfall).

I guess any moisture funnels down to where the contacts are, and then runs into the circuitry that way.

 

[kenny1999]

While connected to the supply, the charger will be operating under high voltage stress, even while it is not charging a battery, so the life of a little used product will likely be decided by the durability of the charger.

It is often the starting circuit of a switching supply charger that fails after some years of being connected. You will not know that it failed earlier unless it is unplugged, or there has been a power cut, when it will fail to start again.

In the ideal, the mechanism, the battery and the charger should all fail at about the same date. If that was not the case the design would be unbalanced and the initial cost would be higher than needed.

Isn't the battery easier to fail, compared to the charging stand? My thought is battery is a more complicated technology than a charger so it should fail more easily. Just like an old dial landline phone should last much longer than a smartphone, isn't it

 

[Baluncore]

In the ideal, the mechanism, the battery and the charger should all fail at about the same date. If that was not the case the design would be unbalanced and the initial cost would be higher than needed.

Maybe you fear chemical batteries, but don't understand switching converters.
I fear high voltage switching converters and battery chargers, but not batteries.

 

[anorlunda]

Pinging @berkeman and others who make a living making electronics devices.

What would you do technically to give chargers a long life?
What would that do to the cost?

 

[DaveC426913]

I think minimizing cost may be simplistic. One should factor in the profitability of having to replace components.

Try to buy a charger for a cordless drill (super cheap) without having to buy a battery ($80+) with it.

It may not be directly analogous to the profit model of phones, but I suspect it factors in somewhere.

 

[berkeman]

Isn't the battery easier to fail, compared to the charging stand? My thought is battery is a more complicated technology than a charger so it should fail more easily.

I would expect most batteries to have a shorter life than the associated electronics, but not because of them being "more complicated". Depending on the batter chemistry, there are wear-out mechanisms that gradually degrade the energy storage capacity. That's why we are encouraged to mostly discharge our phones and laptops, etc. before recharging, instead of leaving them plugged in all the time. Not cycling those batteries decreases their lifetime dramatically.

And how often do you need to replace the battery in your car, versus having to replace the Engine Control Unit (ECU)?

 

[DaveE]

What would you do technically to give chargers a long life?

1) Hire more experienced EEs with proven ability to design hi-rel power supplies. = more salary cost, if you can get them.

2) Give the design team more time to design, analyze, and test the design. = more time to market, higher NRE cost.

3) Design and implement better manufacturing tests, including burn in, as appropriate. = greater manufacturing cost.

4) Use only existing proven (i.e. older) technologies. Buy components from reliable sources, both manufacturers and distributors. Buy hi-rel versions of components. = greater component costs.

5) Use larger semiconductors, larger heatsinks, better capacitors, etc. to reduce the thermal stress in the design. = more material cost, larger size.

6) Add additional protective components/functions to the design (snubbers, transient protection, OVP, OTP, OIP, etc.). But not if more complexity means less reliability, this part can be tricky. = more NRE and production costs, larger size.

I could go on for a while yet...

This is a good summary of why I left Mil and space PS designs for the commercial, high tech world. It's not as fun as it sounds. Those designs are, perhaps optimized for their application, but it didn't feel that optimised to me. One hi-rel PS design I did in about 6 months, and then spent about 9 months more analyzing, testing, and documenting it. Total production build of 3; one for deployment, one for a spare system, and one to go into a warehouse, just in case someone wanted to test it later. I never knew what it was for, if it was ever used, or how well it worked.

Later in the expensive commercial product world, with production volumes in the 100's/ year, in my experience the biggest cost and influence on reliability was the amount of effort you let the EEs put into the design (NRE & Time to market). Plus good manufacturing processes to eliminate errors.

Cost is always a factor in engineering. Failure is often a feature; trust me, you don't want to pay for stuff that won't fail eventually. It doesn't do any good to design the best toothbrush if you can't sell any of them on Amazon.

 

[anorlunda]

It doesn't do any good to design the best toothbrush if you can't sell any of them on Amazon.

To reinforce @DaveE 's point. This power supply is for sale on alibaba.com. 12V in, USB out. I expect they have a good market and many customers satisfied by the lifetime at that price. $0.96 each.

Is it better to design a higher quality device that lasts longer? Maybe yes. Maybe no. Customers might prefer to discard them as they fail rather than invest 100x more up front for a long life device.

I can even make a good case for planned obsolescence. I remember one summer around 1980 when I returned my phone to AT&T. I found a mountain of returned phones in the phone company's lobby. Nobody wanted them.

Western Electric bragged that those phones were designed to last 45 years. Who in their right mind would want a 45 year old phone in today's world?

 

[berkeman]

How do you open that phone to see the display?

 

[DaveE]

Who in their right mind would want a 45 year old phone in today's world?

I have that very phone buried in a closet somewhere. I originally kept it so I can make phone calls if the power goes out, but I'm 99% sure that was before I had a cell phone. You can have it for free if you come pick it up.

Now it's a testament to how much useless crap I have squirreled away. I think 6 oscilloscopes at last count, plus one I actually use occasionally.

 

[anorlunda]

if the power goes out

and if you still pay for a land line. Fewer people every day have land lines. I read that Sweden is actually taking down all those telephone wires and poles.

 

[Nik_2213]

I had a batch of very nice 'safety lights' that were motion-sensing night-light on wall-wart cradle, emergency light if power failed and torch if lifted from cradle.

One by one, they died. I found a 'tear-down' failure report on-line. Seems the maker had scrimped on a few components in cradle's contactless charger. A lot out-lasted warranty, too many failed sooner, costing the company dearly in returns and good-will...

Torches are useless, as I cannot charge any since the very last base-station died. No 'user serviceable' parts, no USB socket as Plan_B...

 

[Tom.G]

No 'user serviceable' parts, no USB socket as Plan_B...

That "Contains No User Servicable Parts" is a boilerplate phrase indicating there IS a fuse inside. Every item that I've opened having that phrase had a fuse.

Of those 'sealed' items without that phrase, about 30% had a fuse. (Those were mainly wall powered and a fuse was probably needed for a safety approval somewhere.)

 

[Nik_2213]

Disambiguation: The 'double insulated' wall-wart cradle used SMDs for the contactless charger's inverter, part of which over-heated, died. The torch lacked an auxiliary charging port...