PowerBoost 1000C Tutorial Enhancement Suggestion Moderators: adafruit_support_bill, adafruit

[jdmcs]

The tutorial for the PowerBoost 1000C (great product by the way) could use an enhancement. (It would have saved me time and a PCB mod.)

The tutorial currently describes the LBO pin as follows: "By default it is pulled high to BAT but when the charger detects a low voltage (under 3.2V) the pin will drop down to 0V. You can use this to signal when its time to shut down or alert the user that the battery is low. There is also a red LED connected to this pin."

This description makes it seem as if you should connect the LBO pin to a micro-controller input, which I believe is technically correct. However, if you use a SPST switch to connect EN to GND when you want your project to be OFF, then the Low Battery LED is energized (until you turn your project back ON). So while the significant power draw would be stopped, the ability of the project to programatically warn the user to charge the battery has the trade-off of slow battery drain while OFF. Not optimal. [Yes, I could probably de-solder a component on the PowerBoost to stop this power drain; however, my SMD de-solder skills are really bad and I'm working on a through-hole project so that beginners can build one themselves.]

Both this and this forum post describes a suggested use of the LBO output. It claims that by using an ON-ON SPDT switch and connecting EN to common, GND to one side ("NC" side of the switch), and LBO to the other ("NO" side of the switch), then the project can be turned OFF, and can turn itself OFF when the battery is low. For what I am working on, the user doesn't really need an advanced warning.

I'd recommend that the PowerBoost 1000C tutorial be modified to suggest this as one use of the LBO pin.

[adafruit2]

thanks, we've linked to this handy note in the tutorial FAQ :)

[johanwahlberg]

Are you sure this is necessary to achieve a UVLO function? According to the MCP73871 charging chip specs (https://cdn-shop.adafruit.com/datasheets/MCP73871.pdf) it already has both an UVLO function and another LBO output thats connected to the orange LED. The specs talks about li-ion batteries, so it should be weighted to around 3.0-3.2 V, but I cant identify the correct values in the specs.
The red LED (and i assume the board's broken out LBO pin) is actually connected to the boost chip, and not the charger chip.

I'm not exactly sure what all this means, but I'm hoping someone out there can verify that you don't need to tie LBO and EN together to have UVLO functionality on the Powerboost 1000C. Edit: ...that's safe for lipo's.

[adafruit_support_mike]

The LBO pin is connected to the TPS61090 boost converter.

The MCP73871's LBO pin is also the pin it uses to indicate whether a charging cycle is in progress. We have that one connected to the charging LED.

[johanwahlberg]

So.... do I need to connect LBO to EN to get lipo protective 3.2V Under Voltage Lock Out or not?

[adafruit_support_mike]

Yes. The LBO pin can pull EN low and keep the TPS61090 from operating while the voltage on the Vs pin is lower than 3.2v

[johanwahlberg]

This does not work for me. Using a test setup with a ~50mA load on the 5V output and a 400 mAh 3.7V Li-ion battery.
LBO is jumpered to EN. Nothing else connected. When the BAT voltage drops to around 3.2V the red LED lights as it should, but weaker than with LBO disconnected, and the PWR LED stays on, but also weaker than normal. The load continue to draw ~50mA, but I'm guessing the 5V pin output is lower than 5V. After a while the PWR LED goes black (and so does the load), BUT output is still 2.2V at the 5V pin! It doesn't go completely off until i connect both LBO and EN to GND. Unless my powerboost is malfunctioning, I would say that you actually cannot use LBO->EN as a secure UVLO function to protect your lipos, as stated by some in the forums and this FAQ.

Edit: added photo - it's a bit hard to see but it show the blue and red LEDs lit while LBO and EN are connected. The long yellow cable is for manually testing to pull EN to GND, which works as expected.

IMG_9644.jpg (165.93 KiB) Viewed 4085 times

[johanwahlberg]

Bump. Anyone else got this behavior or is my board faulty?

[ADWSystems]

Let me see if I have this right.

1) Pull EN to GND to disable the 5V output.

2) LBO is pulled high to BAT.

3) BAT is not 5V.

I don't have a low voltage (ie., almost dead) LiPo to test against. What I don't understand is how connecting either EN to GND or LBO will result in the LED turning off. Either/both GND and LBO will be low when the battery is low so other than the (possible) ability for the PowerBoost 1000C to turn itself off in a low battery condition, I don't see why the LED would go out. Therefore the low drain by the Red LED will exist in either condition. Right? Wrong? Explanation?

[johanwahlberg]

It's not really about whether the red LED goes out or not. Pulling EN to GND should disable power output from the booster. IE turn your project off while still being able to charge the battery. LBO goes low when battery power is low. In theory the low state of LBO could act as GND, pulling EN low and disabling power output. But in my case it seems that LBO just barely goes low, probably low enough for an arduino to detect it, but not *low* enough to act as a true GND for pulling EN down all the way. At least that's my conclusion...

[ADWSystems]

I think I have a corollary to the issue. When I connect EN to GND the 5V out goes to 0V. When I connect LBO to an Arduino (Atmel ATMega 328) input pin, the LBO Red LED comes on. I wonder how much output power the LBO pin actually has, and is it all consumed in driving the transistor that drives the LED.

[NT]

Can I chime in here as well because I am doing something a little more sophisticated than just using the LBO output but I am also finding something weird going on.

So essentially the Powerboost is powering a 5V load Onion Omega Expansion dock and I am using a ADS1115 analog to digital converter to ostensibly measure the battery voltage and the input voltage so I can see when mains power is plugged in and how much charge the battery might have left. However, when I plug BAT into A0 all seems ok until I try and turn off the Powerboost by connecting EN to GND. Even though the 5V load seems to stop the blue LED stays on. I have tried driving the ADS1115 using the 5V output of the Powerboost but it still seems to keep the blue LED on? And when in that state does not matter what you do you cannot restart the Powerboost unless you disconnect A0 from BAT.

Is this supposed to happen or am I just missing something? Perhaps I am not understanding how you are to measure battery voltage using the BAT pin?

Thanks.

[adafruit_support_mike]

The blue LED gets its power from the boost converter's 5v output, so something must be keeping the boost converter from shutting down.

Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.

[NT]

The blue LED gets its power from the boost converter's 5v output, so something must be keeping the boost converter from shutting down.

Post a photo showing your hardware and connections and we'll take a look. 800x600 images usually work best.

Ok well here is a picture. Hope it is clear enough.



This is also a video of what happens. Basically I unplug the USB power (keeps on chugging, great!) then I use the switch to connect EN to GND and well you can see what happens. If I disconnect BAT from anything it will turn off as expected. The ADS1115 is powered by the 5V side of the Powerboost but it does not matter if I power it from the Omega either.

Powerboost behavior

[rover67]

I had to join to post, but have been lurking for a bit.

I too did the LBO to EN connection on my powerboost 1000c and ended up ruining a LiPo in the process. I left it going overnight to test it and it never shut off and drew the battery down to almost nothing. It basically totally killed it and now it won't take a charge. I haven't measures voltages but my guess is that the LBO doesn't go to ground or zero, or the EN pin going to ground or zero doesn't really turn the thing off.

My suggestion would be to try to use a battery with it's own power management chip. That'll be what I try next.