Appallingly small LiPo charger add-on for Teensy 3.1

Status
Not open for further replies.
I'll second the tight fit on the connector - I think I saw that noted elsewhere. Will leave it to onehorse to confirm - but AFAIK the power system, pins and wiring by design is the same on 3.1 and LC.

edit> seeing Msg #52 makes sense - I'll tap the corners with plyers when I am ready to use mine with LiPo's. I thought may it was a design trick for mechanical reinforcement.
 
Last edited:
I haven't tried it on the LC yet, but AFAIK it ought to work. If you do try it, please report the results. I'll get around to it myself eventually.

OSHPark does fine work for a very, very reasonable cost but the quality and dimensions of the boards do vary. I usually check to make sure the JST connectors fit since this issue was reported but I don't always check everyone; sometimes the plating on the JST through holes is a bit thick and/or the holes are a tad small. I suppose I could increase the radii of the holes a bit to compensate for those few that are tight. I guess this is the price of low cost.
 
I'm using this on the LC and it's working great.

I want to power an RTC with the 5v output from the Teensy LC. If I understand correctly, the 5v output pin is also the Vin pin that the battery charger is using. Can I just attach my power to that pin also? Or can I not use the 5v output if I'm using this battery charger.
 
That pin can only output 5v while there is 5v on the VIN. So it will go offline when not charging and running on the battery.

What RTC do you have? I saw an Adafruit note that their unit can run at 3.3 - with some hack - I don't have one and so didn't try.
 
Right, I should have been clearer--I'm running the RTC with a separate lithium coin battery, but need to run the I2C part of the RTC board with 5v to in order to communicate with it. So this input doesn't have to be powering the RTC all the time, just when the Teensy is on.

However, I just realized that the battery itself is only 3.7V, so I must not be able to get a 5V output from that pin unless I have the USB powering the Teensy.

The RTC board I'm using is Adafruit's DS1307 breakout board. I can't find anything about powering it with 3v3 with a hack. The lithium coin battery is a 3V but the board itself needs 5V to run.
 
What not use the M41T62, you can run that an 1.5 V IIRC. And it comes as a teensy add-on! You could also just use a logic level translator to talk to your RTC if it's just I2C bus translation that's holding you back.
 
Cool! I'll try taking the resistors out and see if it works at 3v3. I also ordered a logic level translator in case I need it. Thanks for the tips.

Edit: clipping the resistors did not work. I'll try the logic level translator.
 
Last edited:
Last edited:
Hmm alright, thanks for looking. I also cannot find it. I'm not sure what the Pi fix is or why they just clipped the resistors, but it doesn't seem to work here. The logic level translator should be fine, but I might just be switching back to the Teensy 3.1 and that has everything but the crystal built in.
 
The pull ups on the Pi are strong enough to work for I2C usage - the ones in the Teensy (3.1 and LC) don't work out the same.
 
Will this charger work with a 7.4 V battery? I have an application that requires 6V and a healthy (read lots of amp-hours) battery. (It's a robot with the Teensy as its brains). I'll be actually mounting the charger outboard of the Teensy and use a ldo regulator to get 5V for the logic. I'll periodically slide into a charging station that will give me the input to the charger.

Thanks,
Jim.
 
Will this charger work with a 7.4 V battery? I have an application that requires 6V and a healthy (read lots of amp-hours) battery. (It's a robot with the Teensy as its brains). I'll be actually mounting the charger outboard of the Teensy and use a ldo regulator to get 5V for the logic. I'll periodically slide into a charging station that will give me the input to the charger.

Thanks,
Jim.

I think I've answered my own question. It won't work. That appears to be a single cell charger.

Oh well, back to the drawing board.

Jim.
 
Hello everyone.

I am now developing a project with the MK20 that comes with the Teensy 3.1 and I will add a Battery charger, so my connections are something similar to what onehorse's addon does to the Teensy. My question goes to the fact that the MK20 datasheet specifies that once VREGIN goes below 3.6V the pin VOUT3V3 is no longer 3.3V but can vary from 2.1 to 3.6. Does someone know if this would be an issue since I am using a 3.7 V Battery? Are the MK20 and other sensors I am using going to malfunction? Would it be better to use an external 3.3 V regulator?

Thanks in advance.
 
I would think you would be OK with a one cell LiPo, it voltage stays (usually) above 3V3 so it can provide 3V3 through the regulator.
 
Dear onehorse, thank you for your quick reply.

The issue that worries me a bit is the specifications indicated in the datasheet, where it says that below 3.6V, the 3.3V output cannot be guaranteed. I would also expect the output to stay 3.3V as long as my input is higher than 3.3V, but this is not what the specifications say, as it says it goes to "Pass Through mode" As shown below.
This is the reason why I was thinking if it would be a safer option to go with a 3.3V regulator, as I will also need 3.3V for some other pheripherals (Still need to check if they are below 100 mA, but if they are, the only deciding point would be whether 3.3V output can be guaranteed for a Vbatt higher or equal than 3.3V). I appreciate your oppinions on this and the ones from others in the forum. vreg.jpgpass through mode.jpg
 
Well, I am no expert on this issue but I note that I have powered the Teensy with 1 cell LiPo batteries for a long time and have never had less than ~3.2 V out of the 3V3 regulator whenever I have bothered to check, nor have I had any failure to power any peripheral device from this spigot. My advice is to ignore the datasheet for the moment, and simply test your circuit to see if there are any problems, if you can. Empirical tests are usually more telling than consulting the data sheet.

The other option is to use an inexpensive boost converter, like this one, so that you get 3V3 even if the battery drops (most unlikely) well below 3V3. This drop can happen if there is a ginormous current drain of the battery like when you power four DC motors at 2 Amps each in a quadcopter. You can easily lose a volt. On the Edison, if the input voltage drops below 3.15 V, the Edison reboots. This is most inconvenient when the vehicle is 20 feet off the ground! A boost converter eliminates this problem.
 
Last edited:
Thank you onehorse for your reply!! I have another doubt, do you know by any chance if the capacitors shown in pjrc datasheet are all electrolitic? or are some of them ceramic?
 
@onehorse, I am using your new charger remotely from the T3 board pins with a switch external to a case. Seems to be working well, will do some recharge time tests asap. Here is a diag:
pesky_lipo.jpg
 
@onehorse, have done a charging test on the new lipo charger. here are the results. I ran the APA102 pov poi (120 leds) on various colours including full white pattern to drain the 3.7v lipo single cell battery rated at 2200mAh. When the POV stopped working I connected the USB to a wall wart charger. This charger was rated at 2.5A (perhaps a bit too large a charge for the rating of your pesky charger). Anyhow, it look almost exactly 1.5hr for the red charging led to go off. This seem very fast to me. Anyhow, this gives the POV poi a good half hour of use on full colour with white, so should be fine for my uses. The charger was set to 800mA by soldering the 300mA tabs.
lipo battery.jpg
I imagine that the battery was probably nowhere near fully drained because of the amount of current the leds require.
thanks for a fab little charger.
m
 
Last edited:
Thanks for the feedback. Yes, this seems quite fast compared to the ~45 minutes to charge a 350 mAH LiPo battery in my test. But I was charging through the USB cable and these are sometimes limited to ~500 mA, so maybe these results are about right? Still, I am glad it is working for you.
 
Status
Not open for further replies.
Back
Top