cigarette plug USB charger

I haven't received my USB volt/ammeter yet, but it's on its way from Amazon. I plan to check all my cords and chargers to see how they each do.

Then I'm going to play with unregulated solar cells. Seems to me that as long as the PV doesn't exceed the max charging rate (in amps) and is disconnected before the device or battery tops off, it could be a lower cost, lower weight option.

Some of these cheap no named chargers/converters have been known to destroy devices or cause fires, and even a death

http://m.smh.com.au/nsw/faulty-usb-phone-charger-blamed-for-sheryl-aldeguers-death-20140627-zsoc8.html

My suggestion is to look for the CE symbol at the very least … And its not expensive, MEC sells one with double outputs for $10

In this case trying to save a few bucks can destroy your $$$$ device or worst

The voltage for a USB power supply should not exceed 5.25v

http://www.ti.com/lit/an/slyt118/slyt118.pdf

>"My suggestion is to look for the CE symbol at the very least"

I saw some very nice looking Disney holograms on stuff in Bejing that I'm sure didn't pay any royalties. Screen-printing "CE" is even easier.

I have flung a few 12-VDC-to-120-VAC cigarette-lighter inverters out the car window as they start to smoke and sizzle.

Cheap electronics and white-gas stoves: always leave a clear path for throwing flaming objects away from you.

I saw some very nice looking Disney holograms on stuff in Bejing that I'm sure didn't pay any royalties. Screen-printing "CE" is even easier.

Buy it from a large reputable retailer, like i said MEC sells one for 10 dollahs

http://www.mec.ca/product/5031-760/ultimate-survival-technologies-volt-xl-12v-usb-chargeradaptor/

Hi David

> Then I'm going to play with unregulated solar cells. Seems to me that as long as the
> PV doesn't exceed the max charging rate (in amps) and is disconnected before the
> device or battery tops off, it could be a lower cost, lower weight option.
Depends on the battery.

All good lithium batteries have a little circuit inside which shuts off the charging current when the battery is fully charged. Also, what a solar cell puts out depends entirely on how much sunlight it is getting. Just becasue it is labelled '12 V' does not mean it will always put out 12 V. This works FOR you.

So what you do is hang your 12 V solar cell onto your battery and let it charge. Don't worry about the '12 V' bit. When the battery is fully charged it will switch off safely and the solar cell output will shoot up to above 12 V. I stuck a 10 V zener diode in series with a white LED across the output: when the LED lights up I know the battery is fully charged. Works well.

Cheers

"Depends on the battery."

Some charge controllers are intended for use with wet lead-acid batteries. Others are intended for lithium rechargeables. It works best if the charge controller is sized appropriately for the solar panel.

In the case of a lead-acid battery, you want to charge it at some current which produces about 13.6 volts at load to the battery terminals. That voltage will vary a little with the actual battery in use. Mine go about 13.6-13.7. Lithiums are different.

A solar panel will charge at less than 13.6 volts, but it doesn't work very good. Plus, if you let it go higher than about 13.8 volts, it boils off excess battery fluid, so that kills your batteries in the long run. Further, if the solar panel goes dark, you do not want the battery voltage reversing back into the solar panel. That heats the solar panel and drains the battery. A good charge controller will limit the charging voltage so that the charging current is just about right.

Additionally, a good charge controller may have an equalization mode that will help a lead-acid battery. I do not think that it is useful on a lithium.

–B.G.–

If you're watching the voltage, you can just disconnect it when it achieves the desired voltage.

A controller is not 100% efficient so you lose some of the solar panel power.

I have a solar panel I just stick on a lead acid battery. I usually don't fully charge it (which can be a problem).

Also, you don't want the battery to lose power when the sun stops shining, but again, if you're there anyway, you can just disconnect it.

"All good lithium batteries have a little circuit inside which shuts off the charging current when the battery is fully charged."

Sorry that is not true. It depends on the battery. If it is a single round cylinder cell (like the popular 18650 cells) it probably does not have a built in cut off. Some cell phone batteries have 3 connections instead of the usual 2. The 3rd is a sensor that tells the charge controller in the phone to stop charging. If you are talking about a battery pack with multiple 3 volt battery cells (laptop battery), a charge controller is sometimes built into the battery pack and it would cut off power when the battery is fully charged. In my experience most single cell lithium batteries do not have charge cut off sensors.

"It turns out the cigarette plug USB charger I used and blew up some device, puts out 12 volts, not the 5 volts USB is supposed to have

I don't know if this is common."

It is not common in my experience. Also keep in mind that the device you plugged into it may have overloaded it and cause it to fail and go to 12V. Some devices are designed to work with specific chargers that may look like standard USB plugs but in reality are not. My old blackberry phone would only charge from the blackberry specific chargers. Most other generic USB AC adapters and car adapters that I have would not not charge the phone. Yet the when I used a USB cable to connect the phone to a laptop to download or transfer data it would talk but would not charge, of charge extremely slowly.

The voltage monitor you got will work as long as you watch it during the entire charge cycle. IT would be better if it automatically cut off power to the device. That way if you look away at the wrong time you device would not be destroyed by the failure of cigarette USB adapter.

"If it is a single round cylinder cell (like the popular 18650 cells) it probably does not have a built in cut off."

So-called "protected" 18650 cells will have a small protection circuit board (PCB) included that protects against current over-drain, voltage over-charge and over-discharge, and short circuits. The PCB is basically soldered or welded to the unprotected cell, then the assembly is shrink-wrapped.

Since this increases the physical dimension of the cell, it may not fit into a battery holder designed for a bare (unprotected) cell.