BQ25504: Increasing Charge Current

George Ioakimedes

Part Number: BQ25504
Other Parts Discussed in Thread: BQ24210, TPS61200

We have some mono-crystalline single cell solar panels which have ~0.5-0.6V/2A ratings. We have some Li-Ion batteries that we want to be charged from the solar cell but all of the energy harvester ICs with boost capability only have a 100mA charge capability. I also noticed that although they can operate from single solar cells the efficiency is the best when the input voltage is closer to 1.5V.

Am I correct that if I want the best efficiency I should be using 3-4 solar cells?

Is there a method or different part if I want higher charging current, say maybe 200mA?

over 7 years ago

0 Raheem over 7 years ago

TI__Mastermind 21590 points

Hello George,
Since the peak input power for this device is 400mW, i'll suggest using a solar panel with a higher voltage and lower current than the one you currently have to increase efficiency. For a higher charging current, please take a look at the bq24210.

Regards,
Raheem

0 George Ioakimedes over 7 years ago in reply to Raheem

Genius 4950 points

Hi Raheem,

I had looked at the bq24210 but the input voltage started at 3.5V so I initially ignored it. We had wanted to use Sunpower cells as they have the highest efficiency but I can't seem to find them in a small size configured in series in order to get the higher output voltage. Any chance you know of a source that can supply cells with >20% efficiency, >3.5V so it can be used with the bq24210, and size smaller than 5" x 5"?

Regards,

George

0 Gabor Torok over 7 years ago in reply to George Ioakimedes

Prodigy 10 points

Hi,
I use BQ24210 for a solar charger with a 3.5W 6.5V solar panel. 50pcs have been working properly for two years.
Because of the size limitation a 1W or even a 2W version might be applicable for you.
For example www.voltaicsystems.com/1-watt-panel.

Best Regards,
Gabor

0 Jeff F over 7 years ago in reply to George Ioakimedes

TI__Guru**** 166136 points

George,

You might consider the two chip solution using a TI boost converter (TPS61200) and op amp as explained here: www.ti.com/.../slva345

0 George Ioakimedes over 7 years ago in reply to Jeff F

Genius 4950 points

Hi Jeff,

I hope the Holiday Season is treating you well! Thanks for pointing out this app note, it looks very interesting and I think I'll have to give it a try and see how it works for me. Just because I'm lazy, I have to ask if by any chance there's a reference layout that goes along with this app note. I'm thinking not but figured it couldn't hurt to ask.

Thanks,

George

0 Jeff F over 7 years ago in reply to George Ioakimedes

TI__Guru**** 166136 points

Hi George,

Unfortunately, I am not aware of a complete reference design associated with this app note. I suggest using the TPS61200 EVM as a starting reference for layout.

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BQ25504: Increasing Charge Current