Connecting 12V SuperCap Bank to Charge 72V Battery Bank from DC Wind Generator

Your help would be greatly appreciated.

I have the following concept that I am currently using and need
assistance in trying to achieve 2 things at once.
I have a DC (wind) generator that can provides almost constant DC energy.
I have a 12V Super Capacitor bank that receives this energy.

On the other hand I have a 72 volts battery bank in Series that is powering a 72 volt Electric Motor.

Due to my novice electrical background, I’d like to know how I can distribute the power from the SuperCaps to the 72 volt battery bank.

On a direct basis, I can only connect the SuperCaps to one of the 12v batteries in Parallel.

Initially, I had each 12 volt battery connected in Parallel to a 12V SuperCap (battery equivalent). But, I am not able to connect more than one 12V SuperCap to the Generator at the same time.

How would it be feasible to connect this entire system together, where as, I receive DC energy directly to the supercaps and then have the supercaps connected to the batteries and the 72 volt Electric Motor at the same time.
Is there some type of module and or circuit that can be created or???

Please Help!
Alex
787-246-6811

Sounds like what you are saying is that you have a 12V DC generator that you use to charge your 72V bank of batteries using a 12V Super Capacitor bank. You've been doing this by first charging the Super Cap with the generator, and then charging one 12V battery with the Super Cap bank. You need to do this 6 times to impart a charge to the whole 72V battery array, AND you need to do that however many times it takes to impart a full charge (i.e. 6 * n .. 'n' being the ratio of the capacity of the super cap to the capacity of one of the 12V batteries).

Am I right?

If so, you need a 12V to 72V DC-to-DC Boost Converter. Not sure if such a thing exists off the shelf, so it will probably need to be designed and built.

Another possibility is to use a 12V to 120V inverter, put a bridge rectifier on the output and then a high wattage resistor in series with that and the 72V battery array, then add a comparator to monitor the voltage level of the battery array. Use the output of the comparator to shut down the charge circuit (i.e. the bridge-rectified inverter output) using something like a relay. Also, throw some hysteresis on that comparator, so the thing doesn't chatter. BUT, that's a rather inefficient way to do it -- better to use a Switch Mode DC-to-DC converter.

Also, I'm assuming the batteries in this 72V battery array are lead-acid. If not, then you will probably need a more sophisticated battery charge monitor circuit (something more than a mere comparator). Also, if the environment that the batteries are in, is subject to large temperature variations, you might need more than a mere comparator (unless it's not important that batteries reach full charge in all cases).

Also, I'm assuming that the Super Cap bank is merely being used to transfer energy from the generator to the battery array. Is this correct?

Yes, your assumption is correct. Thank you for your insight. Gonna scour the net for a 12 to 72V Boost Converter.
Best,
Alex

Batteries have a much better energy density than even supercaps, so as Steve says, it is most efficient to charge the batteries directly from the generator.

Are the two systems close enough together to be permanently connected, so that a suitable circuit could do everything automatically ? Out of interest, what equipment are you running at 72V ?

When charging a battery, you need a voltage somewhat greater than the nominal battery voltage, or the charging would be extremely slow.
For example, the 12V battery in a car is charged by an electrical system running at about 14V.

Do to the fluctuations of the generator, I'd prefer to use the SuperCaps and then to the batteries. After what Steve indicated, it is pretty difficult to obtain a 12 to 72V Boost Converter. My question to both is, would it be much easier to connect 6 - ~12v to12~15v Boost converters and still have the battery bank connected in series for the 72 Volts that I need to run the Electric Motor. Oh, this is a system I'm developing for a Zip Line which is located far from any electrical infrastructure.

Thank you!

Ahhhh, I see, the SuperCap is a buffer between the generator and the batteries. Good idea.

Also, as long as those 6 converters are _isolated_ that might actually work. And that gives me an idea:

How about six of the following:

12VDC to 120VAC (or 240VAC -- not sure what region you're in) inverter connected to a battery charger which is connected to one battery. The inverter (and probably the battery charger, too) will be isolated, so you should be able to connect the battery chargers across the batteries and still have the batteries in series (for your 72 volt system).

This is probably the best scenario because each battery will be maintained separately and thus none will be overcharged, even if the batteries are not exactly the same (even if they are physically the same, there can be variances).

Thank you again Steve for your time and suggestions.

I think I'll go with the first, kinda feel it can be much simpler to start.

Oh, and I am located in the mountains in central Puerto Rico.

If I may, one more question, do you think a 3Amp Diode suffice for each isolation? That's the best I can get at Radio Shack. If not, I will get them online.

Best Regards,
Alex

There's no way to tell if a 3Amp diode is enough, with the information you've given so far.