USB/DC/Solar Lithium batteries charger LOAD and boost chips

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Nicola1337
 
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USB/DC/Solar Lithium batteries charger LOAD and boost chips

Post by Nicola1337 »

Hi and good day! :)

I've been studying this charger for several months; MCP73871 it's a great chip. But recently a doubt arised. In the product description is told that on the LOAD can be applied a project such as a Mintyboost.
Mintyboost just like Powerboost chargers are based on "boost" chips: they expect a lower INPUT voltage in order to take it up to about +5V.
However, the MCP73871 "load sharing" could take the INPUT energy from the solar panel (+6V) directly to project plugged into the LOAD.

So the booster will receive as INPUT +6V and that's shouldn't be teorically correct for a booster chip.

Is this logic correct?

Many thanks ;)
Nicola

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adafruit_support_bill
 
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Re: USB/DC/Solar Lithium batteries charger LOAD and boost ch

Post by adafruit_support_bill »

Strictly speaking, that is correct. In practice, it doesn't seem to cause any major problems.

Nevertheless, a better choice than the MintyBoost for that type of application is the Verter which is a combination buck/boost converter. https://www.adafruit.com/product/2190

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Nicola1337
 
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Re: USB/DC/Solar Lithium batteries charger LOAD and boost ch

Post by Nicola1337 »

Thank you, Bill! Will the booster output +5V in that case? Or +6V? If it's +6V, may it be dangerous to charge a smartphone?

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Re: USB/DC/Solar Lithium batteries charger LOAD and boost ch

Post by adafruit_support_bill »

When the input to the Verter exceeds 5v, the 'buck' circuit takes over and regulates it back down to 5v.

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Nicola1337
 
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Re: USB/DC/Solar Lithium batteries charger LOAD and boost ch

Post by Nicola1337 »

Yeah on the Verter I know it. I probably didn't explain the question well :)
I wonder what happens when a charger such as the Powerboost receives +6V. Will it output +5V?
My technical problem is that the Verter doesn't output more than 500 mA and I need to charge tablets or smaller devices. So I have to be sure to get +5.2V and a nice 1000 mA current.

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Nicola1337
 
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Re: USB/DC/Solar Lithium batteries charger LOAD and boost ch

Post by Nicola1337 »

I correct myself: the Verter doesn't output more than 500 mA in boost mode. When in the load sharing circuit (in the MCP73871) there is no voltage from the solar panel, it takes energy from the battery. But the boost mode of the Verter can't handle a fast charging current such as 1000mA.
If I had a Verter (TPS63060) that could handle 1000 mA in boost mode it would be the perfect solution for my project.

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Re: USB/DC/Solar Lithium batteries charger LOAD and boost ch

Post by adafruit_support_bill »

There is nothing in the MintyBoost to regulate it back down to 5v. I haven't measured it, but I'd expect the output to be a few tenths of a volt lower than the input at that point.

Note that the MintyBoost wont do more than about 500mA either. You would need something like the PowerBoost 1000 for charging tablets.

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