USB/Solar Charger question

Breakout boards, sensors, other Adafruit kits, etc.

Moderators: adafruit_support_bill, adafruit

Please be positive and constructive with your questions and comments.
Locked
User avatar
Bel_Z_Bub
 
Posts: 263
Joined: Wed Jun 04, 2014 1:58 pm

USB/Solar Charger question

Post by Bel_Z_Bub »

Sorry if this is an obvious question, and excuse my lack of knowledge on this, but why is there a 10k resistance measured between B+ and L+? even when the board isnt charging/or powered off. On load this causes +/- a 0.35 voltage drop. I cant find any other resistance in my circuit.

I'm also monitoring the load between charger and powerboost 1000 with an ina219. would calibrating the ina219 to 10k resistor (instead of the default 0.1 Ohm) give me the right voltage? or a smart calculation in my code. or should I just move it to in between battery and charger?

The powerboost 1000 (and 500's a have) lbo light also goes on when the battery is still 3.6 but the load (after the charger) measures way below that. either in my projects or on a breadboard makes no difference.

I own two of these chargers both measure the same resistance. the regular USB/Lipo chargers I own dont measure any resistance between battery and load.

I'm using this charger becuase of the smart load sharing, I'm only using usb based power sources.

Thanks in advance!

User avatar
adafruit_support_bill
 
Posts: 88093
Joined: Sat Feb 07, 2009 10:11 am

Re: USB/Solar Charger question

Post by adafruit_support_bill »

The load-sharing circuit of the charge controller has a pair of MOSFETs to switch current between source, battery & load. That would account for the voltage drop.

Post a photo of how you have everything connected.

User avatar
Bel_Z_Bub
 
Posts: 263
Joined: Wed Jun 04, 2014 1:58 pm

Re: USB/Solar Charger question

Post by Bel_Z_Bub »

thanks for the quick reply!

So its normal I figure. So I should just move the ina219 to before the charger, or add an extra ina 219? I want to monitor the battery as well as the input power. (I could use a gpio pin for the input power with voltage divider but they are all taken)

for now I just do (measured value/91)*100 and it gets me pretty close, but the value changes when more slave devices are active.

Although I'd love to show off my project again I dont think pictures would do any good as its all stacked together with headers. the ina219 and charger are even build into one breakout. I could show you a breadboard setup with new components if it would do any good, it shows the same results.

User avatar
adafruit_support_bill
 
Posts: 88093
Joined: Sat Feb 07, 2009 10:11 am

Re: USB/Solar Charger question

Post by adafruit_support_bill »

Not sure how you have the INA219 connected now, but it needs to be all on one side or the other of the charger.

User avatar
Bel_Z_Bub
 
Posts: 263
Joined: Wed Jun 04, 2014 1:58 pm

Re: USB/Solar Charger question

Post by Bel_Z_Bub »

the L+ of the charger goes to the V+ of the ina219, and the V- of the ina219 goes to the bat pin of the powerbooster.

before the charger (battery side) the battery voltage seems steady, after the charger (load side) it drops the more current is drawn. arround 0.35V in my setup (after the powerbooster 1000 it has a raspberry, rtc breakout, a TPA2016 amp, a piTFT, a piGlow and a few leds running. I was hoping there was maybe just a simple calculation based on the measured current and voltage maybe.

I'll stick to my 91.5% script for now, its close enough. I'll adjust it according to if the screensaver is running or not lol. Thanks!

User avatar
Bel_Z_Bub
 
Posts: 263
Joined: Wed Jun 04, 2014 1:58 pm

Re: USB/Solar Charger question

Post by Bel_Z_Bub »

Just an update, I monitored it for a while and compared different load (current) values with voltage drops compared to what I measure on the battery terminals. I came to a value of arround 0.0004 V drop per 1 mA. so now I have my script do:

measured voltage + (measured mA*0.0004)

and its pretty acurate so far :)

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

Return to “Other Products from Adafruit”