Scenario 12V,20A wind generator to charge a bank of 6x 12V batteries to run a 72V motor. What would happen if you ran a 12V to 110V sine or quasi-sine invertor , through a high power rectifier to the bank of 72V batteries ? What other considerations , protections etc , should it work ?
Lots of wasted juice due to the inverter/rectifier intermediate step, and "a couple batteries' worth" over voltage. Never mind the cost that's likely to be involved in a 20 amp rectifier.
Obviously the batteries are currently sitting in series to give the 72 volts needed to run the motor. I can't see any reason not wire them so that by changing a switch, they're either series for running the motor, or parallel for charging. Once you've got 'em "stacked" in parallel, whether by way of a switch, or by rewiring them, just hook the genny up to them and keep an eye on the charge-state. You might want a current-limiting resistor in the mix, but I suspect that you could run without one, and of course, that's going to extend charge time.
It *SHOULD* work, if the charge-state is carefully monitored, but if you "slip", you may cook off or blow up one or more cells.
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You should be able to build six isolated DC-DC converters with a wide input range to accommodate the voltage variations of the generator, and also individually provide the optimum charge for each battery. Such a charger (about 25 watts) can be made using a PIC or one of many battery charger ICs, and you could add a visual "state of charge" LED indicator to each battery to detect problems.
Paul
No, the PIC is the wrong part for this. You want an LM555 :>
A two LED or two color LED indicator is a better way to go. You have more than two states to indicate:
Blink green I don't see a battery Green The battery is fully charged Blink yellow The battery is very low Yellow The battery is being charged RED Big trouble I've stopped charging this battery
n
What batteries, what wind turbine? Same goes for the inverter.
What's wrong with a PIC? They now have the PIC12HV615 and the PIC16HV616 that have built-in voltage regulator, 4 channel PWM, comparator with S-R,
600 mV reference, and other goodies that are specifically for switchmode power supplies and motor control. You can sense battery voltage and current for both charging and discharge, and directly drive LEDs as you suggest. I would use a slightly different color scheme, and use a low repetition blink to indicate status when not under charge (to conserve energy).The difficult part is the isolation. But you can make a very simple DC-DC converter on the 12 VDC generator side, to produce an unregulated raw 12-20 VDC nominal supply on the battery side. Then it is easy to make an efficient current regulated, voltage limited charging supply similar to the PWM LED drivers that are being designed and built by many companies (Zetex, Linear, TI, etc.). The PIC can be programmed for various cell chemistries and charging profiles, and also compensate for temperature.
I have also seen a PIC circuit for Lithium cells that can be chained to others in a series battery pack, and it will communicate with the others to provide an optimal charge for all, and shut down if there is danger of current reversal.
Paul
On May 2, 11:13 am, "Paul E. Schoen" wrote: [....]
Real men use LM555s. :)
You hook a zener to pin 5 of the LM555 :)
[....]This is a wasteful way to go. It is better to send the information about the charge state back to the input side and only have one DC-DC.
Since you like the PIC so much. Put one on the load side to encode the information for sending back digitally.
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