Charging A battery pack with multiple Dynamos

[JamesC]

@tcmtech- That was a very useful solution that i can dwell on. I will definitely look into that. Thank you so much

AS for the external battery, i found a high capacity battery that i could use to charge multiple devices

Battery : Tenergy C 5000mAh NiMH Rechargeable Battery

Link: https://www.all-battery.com/nimhcsize5000mahhighcapacityhighraterechargeablebattery-1.aspx

To achieve the 5V output to feed the USB hub/ports, I plan to hook up 5 of these batteries in series to get 6V and then regulate it down to 5V?

As for charging these batteries, i believe they can accept input current of up to 10A I think for the fastest charging speed

 

[JamesC]

Ok lets Say i want to hook up the APM0001 Kubota Alternator which has a 14amp output at 12V to 6X1.2V 5000mAh rechargeable batteries.

How can I set up the circuit...

 

[colin55]

How fast do you want the battery (cells) to be charged?

 

[JamesC]

How fast do you want the battery (cells) to be charged?

I know everything has its limitations and I am suggesting maybe it being fully recharged in around 1-2hours or faster if possible? The faster, the better.

Also I was wondering whether using gear systems to increase the RPM of the alternator at low speeds will still bring up the RPM as when you are travelling much faster.

 

[JamesC]

I just want to know whether this a safe circuit for a mobile phone charger.

Connecting a 9V battery to a 5V regulator and then connecting it to a female USB connector. Is it safe for me to plug in my phone

I know that the USB ports can either supply 100mA or 500mA based on the load. But is this safe. Will the phone determine how much current it will draw at 5V?

 

[JamesC]

**broken link removed**

 

[MrAl]

Hi,

That looks like it would work, but you should check some other web sites because some cell phones require other connections to the USB connector, with possibly one or two resistors.

One thing to note however, is that the 9v battery above will only provide about 500mAh of charge to the other battery. That might not be enough because some batteries are over 1000mAh easy. Thus you would only get a partial charge. Might be enough in an emergency though. Using two or three 9v batteries might get you a full charge.

 

[William I. Behen]

Another important aspect of the problem is that a dynamo or alternator produces a current, not a voltage. Thus, if the thing is spun by whatever mechanical means, it pushes a certain current, whether or no. If you unload / lightly load it, the voltage climbs, trying to force the current produced through the load. This can damage the load by overvoltage, unles some shunt path is available. In the old days, one simply moved the bicycle dynamo's friction wheel away from the tyre to stop current production....

 

[William I. Behen]

Practically speaking, be sure to limit the charging voltage to whatever the phone will tolerate, like the DC ouput votage rating of the charger supplied by the manufacturer. A zener at this voltage in parallel with plus/minus on the USB should do the trick. Sounds like a nifty app, by the way, for outdoorsey folks who want to stay connected!

 

[tcmtech]

Another important aspect of the problem is that a dynamo or alternator produces a current, not a voltage. Thus, if the thing is spun by whatever mechanical means, it pushes a certain current, whether or no. If you unload / lightly load it, the voltage climbs, trying to force the current produced through the load.

Huh? You cant have current flow without voltage.

As far as I know alternators put out a constant voltage with a current output that can vary from zero to what ever the maximum output is at a given voltage determined by a voltage regulator hence the reason vehicle alternators are rated by their constant output voltage first and peak current limit second.

 

[colin55]

Don't get confused with an actual "generator" and a "generator with regulator and/or bridge" built-in or connected to the "generator."
A lot of the comments above are totally WRONG.

 

[ronv]

Lookie these little guys....
http://www.small-generator.com/Pancake-Generator-YAF-80C.htm

 

[Diver300]

Another important aspect of the problem is that a dynamo or alternator produces a current, not a voltage. Thus, if the thing is spun by whatever mechanical means, it pushes a certain current, whether or no. If you unload / lightly load it, the voltage climbs, trying to force the current produced through the load. This can damage the load by overvoltage, unles some shunt path is available. In the old days, one simply moved the bicycle dynamo's friction wheel away from the tyre to stop current production....

Huh? You cant have current flow without voltage.

As far as I know alternators put out a constant voltage with a current output that can vary from zero to what ever the maximum output is at a given voltage determined by a voltage regulator hence the reason vehicle alternators are rated by their constant output voltage first and peak current limit second.

I would have said that alternators tend to produce a constant current not a constant voltage. The unloaded voltage from an unregulated alternator can be very large.

However, as tcmtech says, that behaviour is modified on a car alternator by the voltage regulator that adjusts the field current so that the generated voltage is constant.

You can only see the alternator's natural tendency to produce a constant current if the battery is missing or faulty, and when the load current changes, the voltage regulator cannot change fast enough to keep the voltage constant. This is what causes the phenomenon of load dump.

The voltage from an unregulated alternator will vary far more when the load changes from nothing to full load than the voltage from an unregulated power supply. The variation is so big that unregulated alternators are very rarely used, while unregulated power supplies are quite common.