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Tomytec Buses charging Reminder


inobu

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The V2 buses have Lipo rechargeable batteries that run down over time. If the batteries are allow run down completely it will not recharge so keep them charged.

Recovery

 

There is a possibility to recover them by spiking them with a quick tap of 5 volts 

 

Here is the jest of the issue. Lipo are susceptible to a chemical break down during discharging events. If left too long the chemical reaction can short the internal components of the battery rendering it useless. Lipo are either raw or with a PCB that protects the battery. This protection circuit will disconnect or create an open in the charging circuit that will warn the charging element not to charge.

 

This is refereed as the sleep mode. If left in this mode too long the lipo will enter into a coma and eventually die due to the chemical reaction.

 

Now the charging element will not attempt to charge the Lipo due to the protection circuit so voltage is never supplied. You can bypass that issue by applying 5v for a few seconds to "wake up" the cell. This momentary boost can establish enough voltage to clear the protection circuitry so the charging cycle can proceed.

 

If you notice the red charging led never came on after plugging in the USB cable. Its because of the lipo PCB. If your lipos are not swollen (indicating of a chemical reaction) you may be able to recover the Lipo.

 

I recovered one of mine that I had boxed up and it is charging now. We'll see if it recovers. I have a feeling that it will because its new but I'm checking for replacement as we speak. I found 2 that might work. 

 

How I did it?

 

This is a power USB to barrel connector, 2.5 jack with wire. Pay attention to polarity.

gallery_153_217_29169.jpg

 

It took the Lipo out and cut the kapton tape from the solder point. Small incisions flaps so its not exposed after I done. I used the solder points as terminal landing points. I took the 5 volts and zap the lipo for a few seconds. When I check the voltage is was 3.7 again and I put it on the charger and it started charging.

 

Inobu

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mr bachmann

must be DC as it is a battery , can the 5 volt be got from a 12 volt DC train controller say set half way or less ???

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You may be able to do so, if you have a volt meter you can measure the output and find what setting gets you 5V.

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mr bachmann

thanks I will play with Bachmanns analogue controller and meter and will let you know - good or bad , shame Tomy don't mention it in their instructions  :read2:

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Actually zapping a lithium ion battery with overvoltage is kind of dangerous and while it might revive a dead battery by burning off the insulating crystal layer from the electrodes, it could also make the battery explode and the revived battery will have a much smaller capacity than originally. For charging, a current limited USB supply is suggested  (5V DC, 500 mA) and the charge controller in the buses limits this further down to safe levels (both voltage and current). If your current is too high, the battery may just explode or if you leave the overvoltage on too long, it might get damaged further. But it might work if the battery is not completly dead, just considered damaged beyond repair by the onboard charge controller. (it's like starting a rusty motor without oil to get the rust off and make it turn, it might or might not work)

 

ps: Most Bachmann analog controllers are low frequency pulse power and the peak voltage could not be measured with a standard multimeter.

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