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Science Forum Index » Electronics - Misc Forum » 12V to 72V invertor for battery charging
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| N_Cook |
 Posted: Thu May 01, 2008 2:14 pm |
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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 ? |
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| Don Bruder |
| Posted: Thu May 01, 2008 4:41 pm |
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In article <fvd4qh$fpp$1@registered.motzarella.org>,
"N_Cook" <diverse@tcp.co.uk> wrote:
Quote: Scenario 12V,20A wind generator to charge a bank of 6x 12V batteries to run
a 72V motor.
What would happen if you ran a 12V to 110V sine or quasi-sine invertor ,
through a high power rectifier to the bank of 72V batteries ?
Lots of wasted juice due to the inverter/rectifier intermediate step,
and "a couple batteries' worth" over voltage. Never mind the cost that's
likely to be involved in a 20 amp rectifier.
Obviously the batteries are currently sitting in series to give the 72
volts needed to run the motor. I can't see any reason not wire them so
that by changing a switch, they're either series for running the motor,
or parallel for charging. Once you've got 'em "stacked" in parallel,
whether by way of a switch, or by rewiring them, just hook the genny up
to them and keep an eye on the charge-state. You might want a
current-limiting resistor in the mix, but I suspect that you could run
without one, and of course, that's going to extend charge time.
Quote: What other considerations , protections etc , should it work ?
It *SHOULD* work, if the charge-state is carefully monitored, but if you
"slip", you may cook off or blow up one or more cells.
--
Don Bruder - dakidd@sonic.net - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... <http://www.sonic.net/~dakidd> for more info |
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| Paul E. Schoen |
| Posted: Fri May 02, 2008 12:18 am |
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"N_Cook" <diverse@tcp.co.uk> wrote in message
news:fvd4qh$fpp$1@registered.motzarella.org...
Quote: Scenario 12V,20A wind generator to charge a bank of 6x 12V batteries to
run
a 72V motor.
What would happen if you ran a 12V to 110V sine or quasi-sine invertor ,
through a high power rectifier to the bank of 72V batteries ?
What other considerations , protections etc , should it work ?
You should be able to build six isolated DC-DC converters with a wide input
range to accommodate the voltage variations of the generator, and also
individually provide the optimum charge for each battery. Such a charger
(about 25 watts) can be made using a PIC or one of many battery charger
ICs, and you could add a visual "state of charge" LED indicator to each
battery to detect problems.
Paul |
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| MooseFET |
| Posted: Fri May 02, 2008 3:26 am |
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On May 1, 10:18 pm, "Paul E. Schoen" <pst...@smart.net> wrote:
Quote: "N_Cook" <dive...@tcp.co.uk> wrote in message
news:fvd4qh$fpp$1@registered.motzarella.org...
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 ?
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.
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
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| gearhead |
| Posted: Fri May 02, 2008 6:34 am |
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On May 1, 12:14 pm, "N_Cook" <dive...@tcp.co.uk> wrote:
Quote: 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 ?
What batteries, what wind turbine?
Same goes for the inverter. |
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| Paul E. Schoen |
| Posted: Fri May 02, 2008 1:13 pm |
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"MooseFET" <kensmith@rahul.net> wrote in message
news:7fd055f2-8275-453d-94a8-26d7fe16ce64@b9g2000prh.googlegroups.com...
Quote: On May 1, 10:18 pm, "Paul E. Schoen" <pst...@smart.net> wrote:
"N_Cook" <dive...@tcp.co.uk> wrote in message
news:fvd4qh$fpp$1@registered.motzarella.org...
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 ?
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.
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
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 |
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| MooseFET |
| Posted: Fri May 02, 2008 5:01 pm |
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On May 2, 11:13 am, "Paul E. Schoen" <pst...@smart.net> wrote:
[....]
Quote: What's wrong with a PIC?
Real men use LM555s. :)
Quote: They now have the PIC12HV615 and the PIC16HV616
that have built-in voltage regulator,
You hook a zener to pin 5 of the LM555 :)
[....]
Quote: The difficult part is the isolation. But you can make a very simple DC-DC
converter on the 12 VDC generator side,
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.
Quote: 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 |
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