Parallel Charging - In need of guidance

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Thread Starter

DanLonds

I want to charge a battery with two current sources. I'm thinking solar and wind.

In the hopes of using two buck-boost converters, has anyone looked into doing this sort of thing?
 
I think two or more current sources will work. The makers of the electronics will say not to do this, because they have not tested this. "void warranty" Probably your idea is a little dangerous mostly because it is not commonly done.

A battery charger will reduce charging current when the battery approaches full. It will totally stop when the batter is at 100%. Or there might be a small trickle charge at 100%.

Because there is more than one source of power you loose the ability to know how much current is going into the battery. If solar can output 0 to 1A and wind can output 0 to 1A then the battery will charge at 0 to 2A. Neither charger can see what the other charger is doing. As long as the battery can handle the 2A I think it will work just fine.

Lets say that the solar charger thinks the battery is full at 14.0 volts and the wind charger thinks the battery is full at 14.1 volts. Then at 14V the solar will stop but the wind will continue for a short time. I don't see a problem there.
 
You may have the option to employ identical switching frequencies. Then you'd stagger the switching of the two sources?

If that works, you could manage the way current flows so as to prevent conflicts of direction or polarity.

If you could share more about your project, that would be of more help.
 
I don't actually think I can synchronize the two converters. Sounds like I may be in need of a current-sense solution?
 
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BrandonJones23

As an update –

You wouldn't use a synchronous converter without implementing that output current sense control. With or without an additional parallel converter, if the inductor current is null when the synchronous (high side) switch is activated, the battery itself would generate a negative inductor current.
 
It would be pretty cool to add a diode at every output. But, I'm not sure I have the patience or want to buy all of it.
 
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BrandonJones23

I don't know that a diode at every output would actually give you enough switching power ...
 
Have you thought about utilizing forced continuous conduction mode? A controller could achieve this for you.
 
If possible, make sure you use a current sensor to check on potential metering or short circuit protection. That'll keep a more secure operation.
 
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