TomTom 540M dead

[jbutton]

Hi all, any help here would be much appreciated. The unit worked well for about 4 months and died last night. I had it unplugged for some time and the battery got drained and the unit switched off. At that point I plugged it in and I charged the battery for hours but I cannot turn the unit ON. No response and I held the power button for up to a minute.

anybody had this happen? is the unit dead or i am doing something wrong. thanks

J.

 

[dhn]

Plugged into where, the computer? I don't suppose you hace an AC charger you can try?

If you only have the computer as a power source (since it outputs .5A which is about half what the car charger or AC outlet puts out) then keep the unit plugged in for 5 or 6 hours (turned off) and try again.

 

[jbutton]

It was plugged in in my car for about 2 hours and then to a PC for about 3-4 hours. The light on the bottom was on so it was charging.

 

[canderson]

Are you trying to turn it on while disconnected from power, or while it's still connected? In other words, is it just when trying to run on battery that it won't power up, or even when it's connected?

 

[jbutton]

I tried both while it was connected and after disconnecting it. Nothing happens at all either way.

 

[DavidS777]

jbutton -

LI batteries are very sensitive to state of charge issues. They don't tolerate being fully discharged very well. And electronic circuits can also be sensitive to damage from under or over / polarity/ power conditions.

You might try this device:
Amazon.com: TomTom USB Home Charger for TomTom GPS Units: Electronics

Although, if your car port has been charging the unit - then this probably will not make much difference. (But they are handy to have at home; and it include various countries power adapters.)

I understand your point of: "Its charging - cause the light is on." Unfortunately - what you actually know - is that the led light works. Since you are talking about the led light on the bottom of your TT - it is much more likely that it is receiving sufficient charging power. The unit should work - while being plugged into the car port adapter.

But LED lights are extremely low power; and can easily be lit - while still not having true sufficient power to actually charge. Maybe a friend has a similar unit with charge cord that you could borrow for a bit...

Since you mentioned that this Unit was only 4 months old - it is also still under Warranty. TT support will authorize a rma and replacement; and the store which you purchased it from - might also still be willing to deal with it...

Hope this helps.

D.

 

[jbutton]

All, thanks very much for your replies. I contacted TomTom and they will send me another unit (looks like it'll be a refurbished unit). Unless this unit that died is a lemon, I am very surprised that by running the battery down the unit takes so much work/time to start up again. It really should switch itself off before it gets to that point.

thanks

 

[DavidS777]

Jbutton -

Good that your having the unit replaced.

Quick note - electronics are not bullet proof. Batteries being discharged can go into a 'opposite' polarity state. Electronics are sensitive to various current and voltage conditions.

LI batteries do not take well to being completely discharged; and actually do not store well either. (Periodically charge them up - even if not being used.)

So for your product satisfaction, and the life and health of your replacement unit - do not let the batteries become excessively discharged. :thumb:

D.

 

[canderson]

LI batteries do not take well to being completely discharged; and actually do not store well either. (Periodically charge them up - even if not being used.)

Of interest - lithiums don't appreciate being stored at 100% charge, either. It reduces overall life. While not a simple task for the average user -- if a lithium is to be stored/unused for a lengthy period of time (a month or more) without use, the industry has determined that the ideal is to store it at about 50% charge.

 

[DavidS777]

Canderson -

Thanks for that info. I had not known the above; and your statement got me doing more research....:tea:

Most GPS units are not being stored unused - longterm. Where it is best to also even reduce the temperature which the LI-IO battery is being stored at....

Me - I need to change how I'm 'storing' my GPS. It is currently plugged in - to my wall charger. From the below link - this is BAD - because of the elevated heat - caused by keeping the battery at full charge. Which they note is what happens to laptops constantly plugged into the grid...

However, keeping an LI-IO battery at Full charge - by charging it up; and disconnecting when charged; and then going on with life and using it - is not a bad scenario...

Quoting: "Similar to a mechanical device that wears out faster with heavy use, so also does the depth of discharge (DoD) determine the cycle count. The smaller the depth of discharge, the longer the battery will last. If at all possible, avoid frequent full discharges and charge more often between uses. If full discharges cannot be avoided, try utilizing a larger battery. Partial discharge on Li-ion is fine; there is no memory and the battery does not need periodic full discharge cycles other than to calibrate the fuel gauge on a smart battery."

This stuff is important (as you noted) if we wish to prolong the life of the batteries and our devices. I had been somewhat surprised that people seemed not to have any concept that fully discharging the battery (to the point the unit shut down) could cause any problems....

How to Prolong Lithium-based Batteries – Battery University

And now, because of your post, and what I've just learned - I'm going t go and unplug my gps from the wall! :thumb:

D.

 

[canderson]

The Battery University is a pretty nifty site. I learned a lot from them back in the day about charging algorithms, and was able to apply some of the ideas I found there to some specific designs.