Three brush charging and phone chargers

[Urgent Austin]

Hello All,

A quick question.  Does anyone have experience of running a three-brush/cutout charging system and also plugging in a phone to charge?  Is the voltage stable enough, or might I blow up my phone?!

All experiences welcome.

Many thanks!

Geoffrey

[Reckless Rat]

If it's any use, I have a 3 brush dyno on 6v and have made a little box to go between the seats, fitted with a USB charging point and a 12v cigar socket. It is powered by means of a step- up transformer which feeds 12v to the cigar socket and the double USB socket and is fine for phone charging. The system is controlled by an isolating switch that means it's only live when needed. I bought the 6v to 12v widget on the bay of E.

I tried all ways to get the usb socket to work on a 6v supply ( even though they supposedly only need 5v) but no way would it charge the phone or work the sat nav. Others have had no problems but I needed it to work without fail on a long journey and the widget only cost a few quid. PM me if you need details.

[AustinWood]

I have a cigar lighter socket in the car and use the adapter for the TomTom Sat Nav which is 5.5 V . Also for charging phones of all sorts via a USB. It's the standard A7 6V, 3-brush dynamo.
No problems at all in 5+ years and thousands of miles.

[Robert Leigh]

I have a standard car type auxiliary socket on our mag Chummy with 6v 3-brush dynamo. It certainly runs a TomTom ok; I can't remeber whether I have used it for a phone.

[Nick Salmon]

It is critical that the + and - are correctly wired. If you get is wrong it will fry your satnav/phone etc. Ask me how I know..
(Anything modern expects a negative earth)

[Ian McGowan]

Urgent, not withstanding what others have said, it all depends on exactly what is inside the large plug on the car end of the charging lead. Almost certainly there will be a 3 leg voltage regulator of the 7805 ilk which takes any input between about 10v and 35v and delivers 5 volts to the phone or GPS on charge. Now, the problem is that various devices that fulfil this function come with what is generally known as different drop out voltages. The most convenient will accept 6.5v and deliver 5v. however, they are constructed to a spec. that requires they perform between 11v and 28v input to deliver a reliable 5v output. My TomTom worked splendidly on the 6v system until I required it to perform at the same time as over rated headlight bulbs for 3 hours. After one hour the TomTom failed miserably as the headlights dragged down the voltage available at the battery. So, like Reckers, I fitted a DC-DC up convertor (AKA as a "Buck convertor" to our US cousins) to convert the 5 to 7.8v battery voltage to a reliable 11 or more volts to drive the charging lead under virtually all conditions likely to prevail, since when I have had no problem. Better safe than sorry!!

[Pearls not a Singer]

Easier & cheaper to use a USB phone battery bank. Much safer for the phone electronics which are expensive if wrecked by  a voltage spike.

I got a solar powered version from that well known car accessory shop and the phone can be charged anywhere.

[nrzam]

I use one of these to charge a powerpack with the phone plugged into the pack. Under £3 for the convertor.

https://www.ebay.co.uk/itm/193570020470

Ian

[John Mason]

I did it the Reckers way with a small converter bought via eBay. This gets around the polarity issues as I wired it direct to the battery via an in-line fuse and also an on/off switch. My car is neg earth however if it had been poss earth it is just a case of changing the input wires to the opposite terminals.

John Mason

[Urgent Austin]

Hello all, many thanks for your replies. It sounds as though the plug bit will iron out most of the ups and downs of the charging system, which was my main concern. As others have said, these devices are delicate and expensive!