Golden Motor 48V10AH: getting power from charging port?

[Wummi]

Hello, I just wanted to ask if it is any problem when you get power from the round (chinch) charging port of the battery.

I don't need much, just a few milliAmps to charge my cellphone, but not all the time, so I would build a charger with a chinch port to connect to the battery if I want to.

Does this damage the BMS or is it safe?

[Marsbar]

Remember it's just not a few milliamps... you need to use the power output not input.

You are saying you want to charge a mobile, but a normal USB charger gives up to 500mA. My mains charger gives out 700mA to my telephone over micro USB.
If you want to charge your phone you need a voltage regulator, but most voltage regulators takes only 30V in maximum. Also, you need heat dispensation og 48-5V*0.5A=21,5W if you used LM7805 with 500mA output. But then again, it only takes 30V in or so if I remember right. To avoid 21,5W in heat you need to use a step down transformer, but still it would need to handle 48V.

A resistor in front of voltage regulator to lower the input voltage would not work either, since unloaded the voltage regulator still would give 48V in. (Resistor would not make any voltage drop it the current is very low)

I think the trick would be to get hold of a 30-56V to 5V step down transformer circuit. But I have not seen any, only from 30V to 5V. But still, maybee someone will design it as many people would like a 5V USB contact on their bicycles (Including me?)

[Wummi]

Cheap 110-230V Wall chargers work fine with ~50V DC

I just measured one, and it takes ~150 mA charging my phone @ 57V (fully charged battery)

so it's really not much current

[MAGICPIE3FOCUSPOWER]

Mostly charging socket is just same as output, but with thinner cable.
Just measure the voltages and you will know....

[Marsbar]

You are connecting a wall socket charger 60Hz AC 110V charger directo to the DC 48V battery? You are lucky it works... there is a possibillity the charger will be destroyed as the rectifier diodes will be overloaded since you are running it on DC. Not recommended! Most chargers specify the voltage range, example 100-250V.

[Morgen 3Eman]

Sorry Marsbar, but if the charger is labeled 100-250 volts, it is going to be a switching power supply; the input circuit consists of a diode bridge rectifier and a filter cap that turns the AC voltage into a proportionate DC voltage . Thus, the higher the AC voltage supplied, the higher the DC voltage across the switching circuit.   Having a lower voltage impressed across the input circuit will not overload the diodes.  Whoever told you that was terribly ignorant.   Wummi is correct about using them.  I can tell you where to find cheap ones:  go to the local second hand store, Good Will, Salvation Army or equivalent in your area.  I pay about $1-3 for them.  My lights, turn signals and GPS are powered by 4.5V, 6V and 12V swithcing chargers.  Light, cheap, rugged, they work just fine.

I don't have a clue about using the charging port.  Generally speaking, tho, connections are labled as "Output" or "Input" for a reason.  Any reason you can't access the output?

TTFN,
Dennis

[Wummi]

I don't have a clue about using the charging port.  Generally speaking, tho, connections are labled as "Output" or "Input" for a reason.  Any reason you can't access the output?

it would just be nice. I don't need the phone/charger all the time, and with my build the charging port of the battery would be in a perfect place.
i would just solder a chinch to my phone charger, and plug it in whenever I need it.

maybe I will open the battery and look myself, if nobody knows a good answer.

[MAGICPIE3FOCUSPOWER]

Why don't do measure the voltage?
If it's the voltage as the output.....then ...

[Marsbar]

A descent charger would have a full rectifier using 4 diodes. If you put DC into it, only 2 diodes will be used. Some chargers only use 1 diode so you have to plug it in the right way... But still, maybe the diode can take it... so probably not important.

But I am surprised a charger intended for 110V will go as low down as 48V (!) and still work properly, when it obviously is so out of specification.

But hey, maybe I should try it myself? Maybe the switching transformer really can take lower voltage than intended 

[Wummi]

A descent charger would have a full rectifier using 4 diodes. If you put DC into it, only 2 diodes will be used. Some chargers only use 1 diode so you have to plug it in the right way... But still, maybe the diode can take it...

But I am surprised a charger intended for 110V will go as low down as 48V and still work properly, when it obviously is so out of specification.

But hey, maybe I should try it myself, it it works it works and problem solved? 

I have tested a few, and not all of them go so low. some don't work with 48V
I have tested one that started working at ~22V, you just have to check a few!

[Morgen 3Eman]

The switching circuit just controls the pulse width into a high frequency step-down transformer to achieve the required output voltage.  If the input voltage is high (250 VAC), and the output current is low, the transfer pulse is very narrow, or even nonexistent .  When the input voltage is low (100 VAC) and the output current draw is high, the pulse width is much wider.  By inputing 48 VDC ( really closer to 55 VDC), the regulation system widens the transfer pulse to maintain the output voltage. I've only used 7-10 modules by various well known manufacturers, and all have worked. I don't think I've used any that had an output voltage higher than about 16VDC, and I've never tried anything but 48VDC, and always connect the neutral input pin to the Neg supply,  so I make no claim outside those parameters.   Clearly, your experience may vary. 

On a personal level, if I was in your position, (with my admitted personality defects) I would just go ahead and try it.  The battery charges at several amps, so the wire size would be more than adequate for 150 mA.  If there is a reverse polarity protection diode, the supply will not develop an output, but would not be harmed. You have to be aware that you will probably not be protected by any low voltage protection circuitry. Just be very careful with your connections, as if you make a short circuit across 48 VDC, you will probably damage something.   

Alan, what 's your thoughts on the subject?



TTFN,
Dennis

[Bikemad]

Alan, what 's your thoughts on the subject?

I'm not sure if it's the same on the later BMS boards, but on the earlier ones the power flowing through the negative battery lead (B-) had to pass through six MOSFETS, four connected in parallel (T1-T4) to control the discharge current (D-) and two connected in parallel (T5 & T6) to control the charge current (C-):



I don't know how much current can safely be passed in a reverse direction through these MOSFETs without causing damage, so Wummi will have to decide whether the convenience of using the charge socket outweighs any risk of possibly damaging the battery's BMS.

It might be safer to install a separate power socket into the battery end cover specifically for use with the phone charger, it could be fuse protected and controlled with a separate On/Off switch along with an LED "Power On" indicator too.

Alan
 

[Wummi]

thanks for the answer Bikemad! I thought something like that.

i will probably just install an usb port on the keylock side of the battery case. I think there is enough room for that.

[Bikemad]

Be very careful, A 48V USB port will probably fry your phone (or any other USB device) in no time at all.

Alan
 

[Wummi]

Be very careful, A 48V USB port will probably fry your phone (or any other USB device) in no time at all.

Alan

haha we need more POWWWEEERR




of course I meant 5V power supply AND usb port ^^