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Off Grid Solar Charging Battery Pack
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Off Grid Solar Charging Battery Pack

by tinkerks on Sun May 02, 2021 1:26 pm

My son (age 10) wanted to build a renewably charged battery pack project for a 4H project and he's having trouble with the Solar cell not charging the battery/powerboost1000 board, even when in very bright, full sun. Here is what he has and how it's connected. Once working, he will cut and solder the conversion wiring to remove some of the converter cables and secure inside a box with some panel mount connectors.

Colossal 6V 9W Solar Panel - 9.0 Watt PRODUCT ID: 2747 <connected to> 3.8 / 1.3mm or 3.5 / 1.1mm to 5.5 / 2.1mm DC Jack Adapter Cable PRODUCT ID: 2788 <connected to> MicroUSB Plug to 5.5/2.1mm DC Barrel Jack Adapter PRODUCT ID: 2727 <connected to> PowerBoost 1000 Charger - Rechargeable 5V Lipo USB Boost @ 1A - 1000C PRODUCT ID: 2465 <connected to> Lithium Ion Battery Pack - 3.7V 6600mAh PRODUCT ID: 353

He has soldered the USB connector to the PowerBoost 1000 Charger to charge a 5V device (iPhone)

Everything works according to plan except for charging via solar panel. The PowerBoost 1000 board powers up and charges battery with a wall transformer (5V 1A iPhone charger), battery works to charge iPhone as well. I looked through the technical specs of the PowerBoost 1000 and the Solar Panel but can't figure out our problem. I'm not an electrical engineer so please explain it like I'm five :-) Thanks in advance for any help!

IMG_1216.jpg
Setup without the device plugged in,
IMG_1216.jpg (772.26 KiB) Viewed 94 times


Order: 2505751-8109758971
Date: 3/7 2021

Order: 2538008-0299975072
Date: 4/11/2021

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Re: Off Grid Solar Charging Battery Pack

by blnkjns on Sun May 02, 2021 1:35 pm

You need a solar charger, because the solar panel has no clean stable 5V output, it can also go way above, some panels output up to 10V. You kind of daisy chained together a bunch of plugs to make it fit. The product linked below will make everything work as expected: it makes sure the battery gets the right voltage to charge, it converts the voltage from the solar panel to match the need of the charging circuitry and it boosts the 3.7V from the battery to 5V output on the USB plug.
https://www.adafruit.com/product/4755

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Re: Off Grid Solar Charging Battery Pack

by adafruit_support_mike on Mon May 03, 2021 11:39 pm

The "Design Notes" page in the Solar Charger's tutorial explains why a direct connection works badly:

https://learn.adafruit.com/usb-dc-and-s ... sign-notes

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Re: Off Grid Solar Charging Battery Pack

by tinkerks on Wed May 05, 2021 9:29 pm

Thank you both for the helpful replies. This has been a fun project and it's nice to have some support. I read through the design notes and I believe that leading up to the purchase we read so many of the different product descriptions for Solar Chargers that when we stumbled onto the 1000C we thought it would be nice to have the charge controller and voltage booster on one PCB but incorrectly interpreted the 1000C as having a Solar charge controller integrated into the device when it does not.

Looks like we should have purchased the 4755 and the basic Power Boost 1000 but pressing forward...can he simply purchase the https://www.adafruit.com/product/4755 and make what we already have work? If so, how would all that connect? What inputs go to what outputs and so forth? I'm concerned the 1000C says it requires a battery be plugged in to operate but that leaves me confused about how to integrate both the 1000C and the 4755.

Would he just connect the load out of the 4755 to the 1000C battery location?

If there is anything else we need to make this work please advise. When he's all done he's going to splice, clean things up and package it into a container for a backpack so we might pick up the 10k thermistor as well to add some safety.

Lastly, since the 4755 is out of stock, would the https://www.adafruit.com/product/390 work in it's place or should I wait for restock of the 4755? Thanks a ton for the help again.

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Re: Off Grid Solar Charging Battery Pack

by blnkjns on Thu May 06, 2021 1:28 am

I don't think the older one can deliver 5V, looks like it only uses USB to charge, not as load. But second thought on my previous advice, I won't believe the new 4755 does not offer this either. Maybe it just does not exist in the Adafruit portfolio. I think we have a product-request here.

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Re: Off Grid Solar Charging Battery Pack

by adafruit_support_mike on Thu May 06, 2021 3:07 am

tinkerks wrote:and I believe that leading up to the purchase we read so many of the different product descriptions for Solar Chargers that when we stumbled onto the 1000C we thought it would be nice to have the charge controller and voltage booster on one PCB but incorrectly interpreted the 1000C as having a Solar charge controller integrated into the device when it does not.

FWIW, that's fairly common. Any time you approach a new field, you have this whole cloud of new information to process, and no context to give it order. It's easy to make early choices that don't work because you didn't have the mental connection for some relevant fact. The mistakes are valuable, even if they don't feel like it at the time, because they limit enough options to give you a system you can test.

That's the development process in a nutshell, really. Most projects are an iterative process of building something good enough to find the next problem you didn't expect, dealing with that, and building something good enough to find the next problem. Success isn't so much "mwa-ha-ha-ha.. it's alive!!" as a slow, slightly numb realization that nothing went wrong this time. That's followed by a rush that makes the whole process worth the effort, and about fifteen minutes of flipping the switch just to see the bloody thing work.

tinkerks wrote:can he simply purchase the https://www.adafruit.com/product/4755 and make what we already have work?

Yeah, either of the Solar Chargers will work. The tradeoffs between the bq24074 and the MCP73871 are listed on the bq24074's product page.

You can use a PowerBoost with a Solar Charger, but to make things work you have to bypass some of the features.

The basic idea is to ignore the Solar Charger's LOAD output and connect the Power Boost directly to the battery. That means you can't use the Solar Charger's load-sharing feature that sends power to the LOAD port first, and only uses excess power to charge the LiPo. You also can't use the PowerBoost 1000C's built-in LiPo charger.

Using the Solar Charger just as a basic LiPo charger, and using the LiPo as the upstream energy source for a PowerBoost does work though.

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Re: Off Grid Solar Charging Battery Pack

by blnkjns on Thu May 06, 2021 4:13 am

It does mean he needs 2 parts: the charger and the booster.
I have a setup with a Waveshare Solar Manager, that unit does all: solar to battery, battery to 5V, 5V to battery. It even has a battery holder for 14500 cells (I would prefer a 18650 holder though). Would be nice if Adafruit makes a similar all-in-one package.

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