How to connect two wind turbines to a battery-pack

[DavidPV]

It may be a basics question, but I have 2 48V PMA wind turbines, each one 1KW rated.

Then, I have 4  12V UPS batteries, in series for 48V, that I want the two turbines to be connected to.

I am also using a voltage sensor/relay to activate a dump load.

My questions;

i-Do I simply connect the + & -  leads coming out of both the turbines into the + & - terminals onto the batteries?

ii-Or should I connect the turbines in parallel first using a connecting strip and then connect them onto the battery's terminals,

[but aren't these (i & ii) both same ideas? And if so, I have read in the board comments as not to connect the turbines, in either parallel or series connection! For unknown reasons]

iii- In last, where do I connect the voltage sensor? Onto the same + & - battery terminals, where I have already connected the turbines?

Again, these may sound very basic questions, but may be helpful to other board members as well.

Dave.

[tecker]

 Pictures and active data

[Chagrin]

(i) and (ii) are the same idea. (ii), however, is a lot easier to work with. From your brief description of your setup it looks like you would have five different sets of wires stacked on those terminals.

The positioning of your charge controllers is the critical issue. You can't have two turbines in parallel leading into a charge controller; a voltage difference between the turbines can lead to getting current flowing from one turbine into the other.

[Nothing40]

Re:Having two wind turbines in parallel;

Wouldn't the rectifier diodes prevent any current from flowing 'into' either of the alternators? (this IS assuming alternators,and not DC generators-though a blocking diode on a DC genny would accomplish the same thing.)

[Flux]

Just connect everything in parallel.  Ideally at the batteries or via some heavy links to the batteries. No problem with the turbines, they won't bother each other even if there is some common wiring . The diversion controller does need to see battery terminal volts with no significant common cables so that it sees the true voltage.

Flux

[DavidPV]

Great, Flux,

Did you mean to connecting them parallely into a connecting-strip and getting only one set of leads onto the terminals?

WHat did you mean by heavy links?

Regarding the charge controller, or the voltage sensor that I am using, isn't there a chance it would read the PMA's output voltage, higher, rather than the actual battery voltage, since it shares the same terminals of the batteries?

Dave.

[Flux]

Nothing too complicated about this as long as the controller is connected to the battery terminals or at least to low resistance links of heavy wire or copper bar, you don't want any volt drop to mess up the controller voltage signal.

AS far as the turbines are concerned you can even let then use significant lengths of common cable as long as the volt drop doesn't cause excessive loss, they won't bother each other.

The turbine outputs do alter the battery terminal voltage that is how batteries work and it is also why voltage is no indicator of state of charge unless the batteries have been standing for hours with no charge or discharge.

The controller needs to maintain a constant voltage at the battery terminals so that the battery can accept what portion of the charging current it can manage without electrolysing and making gas.

Flux