PWM and MPPT, newbie, help???

bradanov · September 2010

Hi!

i have one tristar TS 60 already connected to PV. i'm extending my system so i'm considering of using my tristar TS 60 (PWM) paralelly connected with new tristar MPPT 60 (another PV), both connected to battery bank and DC load.

my question: is it ok to connect it this way? would MPPT and PWM function normal? would there be difference in voltage when charging battery?

is it OK to use PWM charger controller for other sources (i.e. wind, fuel cells)?

tnx in advance and sorry if question si stupid!

BB. · September 2010

Re: PWM and MPPT, newbie, help???

bradanov wrote: »

i have one tristar TS 60 already connected to PV. i'm extending my system so i'm considering of using my tristar TS 60 (PWM) paralelly connected with new tristar MPPT 60 (another PV), both connected to battery bank and DC load.

my question: is it ok to connect it this way? would MPPT and PWM function normal? would there be difference in voltage when charging battery?

Yes, in general is is fine to "parallel" multiple charge controllers at the battery bank (tie the controllers to the +/- battery bus connections).

However each controller should have its own solar array and wiring.

is it OK to use PWM charger controller for other sources (i.e. wind, fuel cells)?

You need to look at how the other sources use the charge controllers to manage the battery charge.

Wind, for example, the turbine is typically connected directly to the battery bank (with fuse/breaker and a blocking diode--if needed). Then a battery charge controller is configured to "diversion/dump mode", placed directly on the battery bank. The charger's "output" is then connected to a resistance heater (hot air, hot water, etc.) to "burn off" any excess energy.

Fuel cells and other types of energy systems--Don't know. For fuel cells, they probably have their own charge controller setup. You need to control the fuel usage to adjust power output from a fuel cell. You probably cannot turn off its output like a "light switch". And you don't want to run the fuel cell at 100% and use an electric dump load to just "waste" the energy. In most cases, that would be a terrible waste of fuel.

tnx in advance and sorry if question is stupid!

Not a problem... We all here have started from nothing and leaned from those around us.

You also asked about PWM and MPPT charge controllers in your title... Here are a couple FAQ's you can start with.

All About Charge Controllers
Read this page about power tracking controllers

Please feel free to ask any other questions questions. That is why we are all here--To learn and help (we are all volunteering our time here).

-Bill

bradanov · September 2010

Re: PWM and MPPT, newbie, help???

i think that voltage output from wind turbine is changing with power produced, so if it is directly connected to a battery it would not charge if the voltage isn't larger than the voltage of PV charger!
thats why i thought to connect wind turbine to a charger controler - to generate similar voltage as PV charger.

and yes, i imagined that fuel cells would generate power only when batteries are empty and there is no other sources available, so if load decrease fuel cells would continue to charge battery, thatway i would not waste fuel.

question:
if all sources (wind, PV, fuel cells) are connected through separate charger controller, and let's say they go to a equilization charging, would it be too large voltage for load (let's say it's electronics) if it is directly connected to a battery???

BB. · September 2010

Re: PWM and MPPT, newbie, help???

bradanov wrote: »

question:
if all sources (wind, PV, fuel cells) are connected through separate charger controller, and let's say they go to a equalization charging, would it be too large voltage for load (let's say it's electronics) if it is directly connected to a battery???

It is difficult to "generalize" how to connect various types of charging sources to a battery bank.

Solar panels, it is perfectly OK to turn on or off their output to control how much power is used to charge the battery bank.

Typically, wind and water turbines need a load (such as the battery) 100% of the time to control their speed. If you put a "switch" (aka solar type charge controller) between the turbine and the battery bank and opened the switch to stop the current when the battery is fully charged, the wind/water turbines will over-speed and can even self destruct.

So, generally, the wind/water turbines are connected directly to the battery bank and a "shunt/diversion/dump" type charge controller is connected to the battery bank to take any "excess power" and "dump" it to an electric load such as an electric heater.

Now, there are always exceptions. For example verticle axis wind turbines generally do not over-speed with no load--so you could regulate them this way (still the issue of the alternator having very high voltage without a load--so it may not be a good idea to use this control method for Permanent Magnet Alternators).

And, there is a new charge controller under development that can connect between a wind/water turbine and a battery bank and perform a MPPT (Maximum Power Point Tracking) type function for find the optimum Voltage*Current output from the alternator and down convert it for use to charge a battery bank. The alternator itself still needs a fixed load of some sort to prevent over-speed even with this setup.

-Bill

dwh · September 2010

Re: PWM and MPPT, newbie, help???

bradanov wrote: »

question:
if all sources (wind, PV, fuel cells) are connected through separate charger controller, and let's say they go to a equilization charging, would it be too large voltage for load (let's say it's electronics) if it is directly connected to a battery???

The depends on if the electronics are over-voltage protected. Some are, some aren't.

bradanov · September 2010

Re: PWM and MPPT, newbie, help???

Ok I understand all you said!

but (always there is BUT), let's say taht wind turbine is connected directly to battery bank (nominal voltage of wind is 48V) would charge controller connected to diversation mode still performe 4 stage charging (by diverting energy)?
how would it even charge battery when voltage is never more than 48V (is it truth?), PV would have larger voltage when charging how would wind than charge?

i'm confused?!?!?!?!

What is the lowest voltage that solar chrager controler can except as input voltage, could it be less than nominal voltage (can it do STEP-UP)???

tnx

BB. · September 2010

Re: PWM and MPPT, newbie, help???

bradanov wrote: »

but (always there is BUT), let's say taht wind turbine is connected directly to battery bank (nominal voltage of wind is 48V) would charge controller connected to diversation mode still performe 4 stage charging (by diverting energy)?

Diversion controllers can do 3/4 stage charging--But they do not charge "as well" as a traditional controller (according to a Windsun our admin).

how would it even charge battery when voltage is never more than 48V (is it truth?), PV would have larger voltage when charging how would wind than charge?

I am not quite sure what you are asking here... standard mode and diversion mode chargers are still looking at battery bank voltage. So, for example, a 48 volt battery bank will be charging around 56-59 volts.

The Solar charger will try to keep the battery at 58 volts, and the diversion controller would probably be set around 59 volts...

When there is no wind, the solar charger will be charging as normal. When there is lots of wind, then the battery voltage will be higher because of the wind charger and the solar charger probably will be supplying no extra energy.

Remember that, very roughly, the battery charging voltage will be below ~56 volts if the battery is at 80% capacity or less--So that both the solar charger and the wind turbine will be supplying 100% of their energy while charging the battery bank...

In all cases, as the battery approaches 80-90% of capacity, you will be wasting excess energy (solar charger cutting back on amount of current, diversion controller dumping current to the heater) to prevent battery bank from over charging.

At this point, many people start turning on their optional loads (water pumps, clothes washers, vacuum cleaners, etc.) to use this, otherwise wasted, energy.

Some charge controller have a contact that can be turned when the battery is in float mode--so this excess energy mode can be automated.

What is the lowest voltage that solar charge controller can except as input voltage, could it be less than nominal voltage (can it do STEP-UP)???

There is no standard solar charge controller today that can do setup charging (not that I know even 10% of the charge controllers out there--so there may be others that can setup voltage). Typically it is because step down type converters (typically Buck Mode type power supply) is the most efficient, reliable, simplest, and cheapest charger topology to implement.

There may be a new solar charge controller coming out with a step-up type charge controller--But I am not sure.

So, for a solar charge controller, the minimum input voltage to a solar charge controller is is:

Vbatt-charging + Vwiring-drop + Vcontroller-drop

For a 12 volt battery bank:

Vbatt-charging ~ 14.5 volts charging / 15+ volts equalizing
Vwiring-drop ~ 1 volt maximum or so (12 volt)
Vcontroller-drop ~ 1-2 volts

Also, remember that Solar panels will run at ~80% of their rated Vmp voltage when installed in hot climates.

And that wind turbine alternators need to be wound for the voltage--otherwise a "universal" system (one that can run at 12 or 24 or 48 volts) will start producing power at low wind/RPM for a 12 volt battery bank, but need a whole bunch of wind to produce power with high wind/RPM.

-Bill

PWM and MPPT, newbie, help???

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