Author Topic: Limiting current for solar battery charger help needed!  (Read 1038 times)

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Offline Meche

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Limiting current for solar battery charger help needed!
« on: July 11, 2017, 07:20:48 pm »
Hi!

I am currently building my own system to charge a battery with solarenergy. I will design my own MPPT and simulate it before building it.
And here is my problem:

The problem is that the MPPT will provide maximum power and lets say i get out 42V and 5A from the buck boost converter. And I would like to charge my Li-Ion battery that requires 42V and 2A.
The 42V is okay but providing 5A to a battery that is specifed to 2A to charge is not good. The battery will drain current as much as it can. And I need to current limit the output from the buck boost converter with some electronics. I don't want to use something like an LM317, LM350 because it will generate a lot of heat.

I 'ive done some reaserch and I have not found any thing concrete and I am turning to his community for some help.
Is there any soulution to limit the current without generating a lot of heat? And if so how could I do that?

Best regards
 

Offline suicidaleggroll

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Re: Limiting current for solar battery charger help needed!
« Reply #1 on: July 11, 2017, 07:22:58 pm »
The current limit will be built into the MPPT.  The MPPT will track the peak power point, up to the maximum output voltage and maximum output current it's designed for.  In this case you'd design it to limit the current to 2A and limit the voltage to the float voltage of your battery.
 
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Offline Meche

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Re: Limiting current for solar battery charger help needed!
« Reply #2 on: July 11, 2017, 07:28:34 pm »
The current limit will be built into the MPPT.  The MPPT will track the peak power point, up to the maximum output voltage and maximum output current it's designed for.  In this case you'd design it to limit the current to 2A and limit the voltage to the float voltage of your battery.

Yes but if I design it for 2 A and later would like to charge another battery that can handle more Amps it would be much better to have some control over the Amps. Lets say like the Imax b6 charger you can select how much Amps to charge the battery i would like to have same functionality if its possible?. I hope I am explaning it good enough.
 

Offline suicidaleggroll

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Re: Limiting current for solar battery charger help needed!
« Reply #3 on: July 11, 2017, 07:41:05 pm »
That's certainly possible, it just depends on how you're implementing your MPPT controller.  For example the SM72442 uses a simple resistor divider on a 5V line feeding one of the pins to set the max output current.  Swap the resistor and you have a different current limit, or you could have a mux or jumper to switch between several presets.  If you're designing your own MPPT with an MCU and voltage and current monitoring, you could have a few different current limits pre-programmed that you switch between with GPIOs, or you could have a serial interface that lets you change current/voltage limits on command.
« Last Edit: July 11, 2017, 07:43:12 pm by suicidaleggroll »
 
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