Project design help

General project help for Adafruit customers

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
zillatron
 
Posts: 3
Joined: Tue Mar 17, 2015 6:46 pm

Project design help

Post by zillatron »

Hello!

I've read a few historical threads referencing using The MintyBoost kit to give a steady 5v off the LOAD output of your Solar Charger (https://www.adafruit.com/products/390).

I'd like to use a combination of Solar and Battery to power USB devices in that way, my questions are:
- When there is plenty of solar power, does LOAD draw power from the battery or the solar directly?
- In that case, is the battery also being charged when there is excess solar power?
- Does the LOAD output draw power from the battery UPS-style when there is no solar power?
- Can you connect a normal mains powered power supply to the USB input at the same time as a solar panel is connected?

- If you wanted to output more than 5v 500mA, say 2A like a powered USB hub - would that be possible (with another regulator)?

Thank you!
Dan

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Project design help

Post by adafruit_support_mike »

zillatron wrote:When there is plenty of solar power, does LOAD draw power from the battery or the solar directly?
Power will come from the solar panel.

One thing to watch: the power from the solar panel comes straight from the panel, so you'll get 6v instead of the 3.3v you'd get when the LiPo was delivering power. If your load is sensitive to the supply voltage you might need a regulator.
zillatron wrote:In that case, is the battery also being charged when there is excess solar power?
Yes. Any current not used by the load goes to charging the LiPo.
zillatron wrote:Does the LOAD output draw power from the battery UPS-style when there is no solar power?
Yep.
zillatron wrote:Can you connect a normal mains powered power supply to the USB input at the same time as a solar panel is connected?
Not a good idea.. the breakout doesn't have any kind of automatic source selection circuit, so you'd basically be plugging the 6v solar panel directly into the 5v mains power or USB rail. Not a combination likely to end happily.
zillatron wrote:If you wanted to output more than 5v 500mA, say 2A like a powered USB hub - would that be possible (with another regulator)?
The MCP73871's upper limit is about 1500mA. Anything beyond that will probably kill it.

User avatar
zillatron
 
Posts: 3
Joined: Tue Mar 17, 2015 6:46 pm

Re: Project design help

Post by zillatron »

Thanks very much, exactly what I was after. :)
adafruit_support_mike wrote: Not a combination likely to end happily.
Ahh, ok. Sounds like a recipe for magic smoke escape.
adafruit_support_mike wrote: One thing to watch: the power from the solar panel comes straight from the panel, so you'll get 6v instead of the 3.3v you'd get when the LiPo was delivering power. If your load is sensitive to the supply voltage you might need a regulator.
I was thinking of using one of the PowerBoost boards or a MintyBoost, is that the right idea?

Thanks again!
Dan

User avatar
adafruit_support_mike
 
Posts: 67446
Joined: Thu Feb 11, 2010 2:51 pm

Re: Project design help

Post by adafruit_support_mike »

If you want to use a PowerBoost, ignore the LOAD output completely and connect it to the BAT pins.

It will bypass the MCP73871's load sharing abilities, but will still give you a good solar-based LiPo charger. The system will have to work a bit harder if you have a LiPo that's nearly empty, but the PowerBoost is an awesome little beast. As long as the panel can deliver enough current, the 5v output should remain stable.

User avatar
zillatron
 
Posts: 3
Joined: Tue Mar 17, 2015 6:46 pm

Re: Project design help

Post by zillatron »

Thanks very much for the advice! :)

Dan

Locked
Please be positive and constructive with your questions and comments.

Return to “General Project help”