Hi, help with supercapacitor charge controller!

[dave_dj88]

Hi!

Does anyone kno any circuits that could control the charge and discharge current of a supercapacitor bank?

 

[jpanhalt]

How about a resistor?

John

 

[dave_dj88]

already considered it, but it's too lossy.

i actually need the supercapacitor bank to abosrb power from a bus when the supply (a PV array) delivers high power, and deliver power to the load when the supply is unable to deliver sufficient power.

any ideas? I was considering a bidirectional converter... or maybe, two converters: one for charging and the other for discharging the supercaps...

 

[jpanhalt]

inductor?

Why not give a little more information about what you are doing and need? That way, you are more likely to get more refined answers.

John

 

[Hero999]

A constant current switched mode power supply?

A resistor is no could because the efficiency will only be 50%, no matter how low the value is.

 

[dave_dj88]

Well, actually i need to vary charge and discharge of the supercapacitor with one controller... that's why i considered the bidirectional dc-dc converter. But the main issue is controlling the value of the current into and out of the supercap bank. I need to somehow be able to vary this current. But I have no idea if i can do this with a dc-dc converter because, as far as i know, they can only vary the switching duty-cycle, and thus the voltage...

 

[dave_dj88]

ok, i think is should provide more info

The image attached shows the system im working on. The load has a strict constant power requirement at a constant voltage, say 48W at 12V.

The PV array may be able to provide more or less than this power, depending on eather conditions.

The MPPT (Maximum Power Point Tracker) is a dc-dc converter that outputs 12V when the PV is able to provide 48W or more (mode 1). But when the PV is unable to provide the required power, the MPPT provides less than 12V and insufficient current for the load (mode 2).

Basically, the supercapacitor must charge up during mode 1 when the PV panel has excess or just enough power, and discharge into the load during mode 2 when the PV panel cannot supply the required power.

The main issue is to carefully control the charge and discharge current values to keep the load voltage at 12V.

Any ideas?