USB charging outlet from ebike 36 volt battery

[eHomer]

I've tried searching the forum to see if anything like this has come up before and couldn't find anything, but apologies if I've missed it...


Has anyone ever rigged up a USB charging outlet on an ebike ?

Aside from charging a phone, I sometimes use a 7" tablet with GPS mapping, and it would be useful to power it from the bike's main battery, a 36 volt lithium-ion in my case.

Being an incurable miser , it strikes me that it must be fairly easy to adapt one of those standard cheapo 12v car cigarette lighter plugs which already have a usb 5v outlet socket. One would presumably just need some sort of zener controlled voltage dropper circuit to lower the 36v down to 12, before the plug's built in circuitry takes it down to 5v.

Has anyone done something like this for an ebike already, or is there a proprietary item already available ? I tried Googling it and found a little bit about a golf cart adapter, but it wasn't too conclusive.

I can't believe that some cheap gadget doesn't already exist to enable a usb power supply outlet from all of the 36 volt bikes and golf carts around the world !

 

[morphix]

I'm no expert with electronics (just dabble a bit) but it seems to me this could be achieved quite easily using an inexpensive voltage inverter and a USB socket. It would cost a couple of quid to build something if you can solder.. you can pick up voltage inverters on eBay from China for that will take 39-35v input and put out your 5v DC for USB. And for the USB socket, if you can't find on eBay try somewhere like BitsBox that do them. They also sell little housings, which might be ideal for your inverter circuit and and you could mount the USB socket on the side.. or you could just chop a USB cable with a suitable USB connector and wire that straight onto your inverter output pins and have the lead coming out of a drilled hole on your housing, ready to plug into your device.




LM2596 35V DC down to 1.37V ± 2.5% £1.37 delivered, from China! (probably need a voltage metre of sorts too, to adjust the trimmer to your 5v or whatever you need).

I have a little charger of some sort which has a standard female USB socket on it (obviously intended to take mains from a wall socket)...it's one of those charges for charging flat Li-Ion mobile/camera batteries that sit ontop. I'm sure these can be picked up on eBay cheap and you could adapt something like that. I would take insides out (which is obviously an AC-to-DC inverter) and replace with your DC inverter circuit, re-wire the USB socket to inverter board for your output (or fit a new socket in the existing hole)...bobs your uncle, job done? You could even utilise the LED and add an on/off switch if you wanted to go all fancy like ;-)

Something like this:

This one is for a Nokia phone. Here's a bunch of them here, for around £3 each.

 

[Deleted member 4366]

If it's just a phone, you can use one of these.
DC 4-40V to 1.5-35V Buck Converter Step Down Voltage Regulator Power Supply | eBay
You can set the output voltage to 5v or 12v. With 5v, you can charge your phone directly, except iphones, which are more complicated. There's an online explanation of how an iphone charger works if you do a search. With this device set to 12v, you can power a normal car charger for your phone. It's rated at 3A max, so might not be enough for a tablet. You can find more poweful ones if you search. Don't overload them because they'll dump the whole 40v into your lovely ipad when it fails. That's another reason to step down to 12v and then use a car charger.

 

[Deleted member 4366]

Another option would ve to get 0ne of these that has a USB charging socket.
12V DC USB 5V Rechargeable Li-po Battery CCTV Camera | eBay

 

[Geebee]

I must admit to being surprised that manufacturers aren't fitting them as standard these day's.
I was discussing exactly that with a work mate last week.

Just make sure you have some head room on the converter if you use one as a 36v pack will get up to 42v

 

[eHomer]

Thanks for the very quick and helpful replies, just what I was hoping might exist.

If I set that inverter to drop down to 12v, then I could mount that in a small box with a 3amp fuse and a standard car cig socket, (one of the boat ones that has a weatherproof cover).
I could then use any car cig usb or phone adapter to supply the tablet or phone.

It specified "4-40v" input, would that be ok for my 36v battery that shows 41.6v (when fully charged) on that little meter that I bought ? (great little device by the way, thanks for the tip).



Here's a photo as well of the plug that I modified to fit the battery pack socket, it's a standard kettle type angle socket with the earth pin removed and the hood cut off with a dremel. Being an angle socket it stops the battery being any longer and fits more snugly.




edit - a typed and sent this before seeing Geebee's comment about the 42v. So would the 4-40v be cutting it too fine ?

 

[morphix]

I must admit to being surprised that manufacturers aren't fitting them as standard these day's.
I was discussing exactly that with a work mate last week.

Just make sure you have some head room on the converter if you use one as a 36v pack will get up to 42v

Good point, like d8veh said, especially if connecting to an expensive phone or gadget. Better get a wide safety margin on input or else look at putting in some overload protection/fuse etc.

 

[morphix]

edit - a typed and sent this before seeing Geebee's comment about the 42v. So would the 4-40v be cutting it too fine ?

I think it would be fine, but just to be safe I'd put a quick blow fuse in there on the output or something.

 

[Deleted member 4366]

Thanks for the very quick and helpful replies, just what I was hoping might exist.

If I set that inverter to drop down to 12v, then I could mount that in a small box with a 3amp fuse and a standard car cig socket, (one of the boat ones that has a weatherproof cover).
I could then use any car cig usb or phone adapter to supply the tablet or phone.

It specified "4-40v" input, would that be ok for my 36v battery that shows 41.6v (when fully charged) on that little meter that I bought ? (great little device by the way, thanks for the tip).

That's exactly what I did with mine. Mine's rated at 40v, and I've never had any problem with my 36v battery up to 42.5v.

 

[Geebee]

If you don't like running equipment that close to that edge , Ebay has this and a lot of others similar with a nice big safety margin. DC Converter Step Down DC 15-60V to 12V 18W 1.5A Buck Module Power Supply | eBay

 

[morphix]

If you don't like running equipment that close to that edge , Ebay has this and a lot of others similar with a nice big safety margin. DC Converter Step Down DC 15-60V to 12V 18W 1.5A Buck Module Power Supply | eBay

Good price too.. the problem with Chinese stuff so cheap as the inverters is you can never be sure of the quality or how the thing is going to perform under load over time.. probably fine, but if you have very expensive equipment connected best to spend a bit more or else add-in your own voltage overload protection eh.

 

[gray198]

I must admit to being surprised that manufacturers aren't fitting them as standard these day's.
I was discussing exactly that with a work mate last week.

Just make sure you have some head room on the converter if you use one as a 36v pack will get up to 42v

Slightly off point, but some electric golf trolleys are now equipped with a usb charging socket for people who use gps/smart phones etc, so it must be easy to do

 

[Jimod]

I have 2 bike batteries so can cycle longer than my satnav or camera battery can last. I bought something like http://www.amazon.co.uk/Portable-Solar-Battery-Charger-1350mAh/dp/B00378SRDY/ref=sr_1_7?ie=UTF8&qid=1354635527&sr=8-7 from Lidl, it cost me a tenner and runs the satnav for more than 2 hours when the satnav's own battery starts to get low. It also re-charges the satnav as it's running it.

Much better in my mind than rigging up fancy circuits to my bike. The one in the link is fiver, get two and you could keep your phone charged as well if necessary. mine charges from the sun or a USB socket. There's not much sun up here at the moment.

 

[morphix]

I have 2 bike batteries so can cycle longer than my satnav or camera battery can last. I bought something like http://www.amazon.co.uk/Portable-Solar-Battery-Charger-1350mAh/dp/B00378SRDY/ref=sr_1_7?ie=UTF8&qid=1354635527&sr=8-7 from Lidl, it cost me a tenner and runs the satnav for more than 2 hours when the satnav's own battery starts to get low. It also re-charges the satnav as it's running it.

Much better in my mind than rigging up fancy circuits to my bike. The one in the link is fiver, get two and you could keep your phone charged as well if necessary. mine charges from the sun or a USB socket. There's not much sun up here at the moment.

Nice one Jim, often the simple straightforward approach is always better I say..unless you're a tight git like me and want to save some pennies ;-)

 

[jazper53]

I have a small motorcycle 12v battery that fits into a small leather toilet bag, soldered a standard car cig socket, I have a standard 5v usb plug that will fit in cig socket, and a standard 3 pin power inverter to 240 ac and can run laptop off

 

[morphix]

I have a small motorcycle 12v battery that fits into a small leather toilet bag, soldered a standard car cig socket, I have a standard 5v usb plug that will fit in cig socket, and a standard 3 pin power inverter to 240 ac and can run laptop off

What type of battery is that jazper? Does it last a good while between charges? Is your power setup just to charge your device or to continually power it?

 

[eHomer]

I've actually tried both of the parallel thinking methods.

I bought a USB "powerbank" a year or so ago and use it with my mapping tablet on my non-powered bikes. It has two USB outlet sockets, is about the size of an Iphone and holds about ten times the power.


I also use a small sla 12v 7ah battery in a waterproof box in my sit-on kayak, also to power the mapping tablet.

They both work well, extending the internal battery range considerably, but they both need forethought and preparation, keeping them separately charged up for when needed.

The desire to fit a standard USB charging socket to the bike's main 36v battery is that it will be a simpler ongoing solution, since the bikes battery will be always kept topped up after each trip, with no further thought. Also, the socket would always be immediately available for emergency phone power, whether the additional batteries have been loaded on or not. The add-on gizmos that people have suggested seem very reasonable, and would be a "fit and forget" solution. I think I would concentrate on dropping the 36v down to a 12v cig socket and then plugging a cheap usb cig plug adapter to get the 5v. Hopefully that would provide enough isolation between the tablet and the 36 volts, in case of faults !

( Ipad ? me ? no way. Not when you can get an android tablet with the same functionality at a third of the price !)

 

[morphix]

View attachment 4573


The desire to fit a standard USB charging socket to the bike's main 36v battery is that it will be a simpler ongoing solution, since the bikes battery will be always kept topped up after each trip, with no further thought. Also, the socket would always be immediately available for emergency phone power, whether the additional batteries have been loaded on or not. The add-on gizmos that people have suggested seem very reasonable, and would be a "fit and forget" solution. I think I would concentrate on dropping the 36v down to a 12v cig socket and then plugging a cheap usb cig plug adapter to get the 5v. Hopefully that would provide enough isolation between the tablet and the 36 volts, in case of faults !

( Ipad ? me ? no way. Not when you can get an android tablet with the same functionality at a third of the price !)

Very logical thinking, seems the most safe and convenient way. Heh, I'm with you on the ipad too, you couldn't PAY me to use that stuff.. rip-off. Android all the way for me, I love my Android phone I do have a Linux tablet too, might put that on my bike...it only needs 3.7V!

 

[jazper53]

What type of battery is that jazper? Does it last a good while between charges? Is your power setup just to charge your device or to continually power it?

The battery is a 12v 7ah I use mainly for night fishing using plug in power inverter gives me light or watch a movie on the laptop if fishing is a bit slow etc The Battery last about 6-8hours for lighting and less for the laptop continuous use, which is sufficient for a night session



Very portable, and can be adapted for multi uses

 

[eHomer]

Thanks for all the guidance and suggestions on this.

I've now thoroughly searched ebay and ordered the parts needed.

A 3 amp max voltage converter that should handle up to 48v on a board that is just under 2"x2", and a mini twin outlet USB charger plug that fits in a standard 12v cig socket and drops the 12v down to 5v on the usb sockets. (fused).

Amazingly cheap as usual, but deliveries from China seem very slow at the moment, so I may not be assembling it until after Christmas..

I've already got a small Maplin plastic case ( about 3"x2"x1.5" internal) housing my digital electric meter, so it should fit in there, and use the same simple two wire feed from the 36v controller connection.

I'll publish a picture of it on here when completed.