energyShield - Rechargeable Arduino Battery w/ Fuel Gauge - Page 1
Forum section: electronics / general

author: aliebold
author_rank: Newbie
timestamp: March 06, 2014, 07:00:45 pm
content: Hi everyone!I'm a fan of the EEVBlog and it has definitely influenced my purchases (Fluke 115& DS2072). I am also a co-founder of a new company called NightShade Electronics that produces products for the hobby electronics community (Arduino, Raspberry Pi, etc.). We have just launched our first product, the energyShield, on Kickstarter!The energyShield is a simple and intuitive solution for powering an Arduino in remote or mobile applications. It is an Arduino shield with a lithium polymer battery, a charging circuit, voltage boost regulator, and an I2C fuel gauge. The fuel gauge provides the host microcontroller with metrics such as the battery voltage, remaining charge, and current draw.We have already reached our initial goal and we are working towards the stretch goals. These will add some incredible new features:$15,000 - 3.3v Output and Breakout Board (non-shield) Style Connections$20,000 - USB (microB) Charging$25,000 - Solar ChargingWhile the energyShield is already a fantastic, uninterruptible power source, achieving these goals will make it invaluable. The solar/USB/AC recharging, 3.3V output, and breakout board configuration will make it ideal for any project that out of reach of a power cord. The applications are, truly, only limited by the imagination!Take a look!https://www.kickstarter.com/projects/nightshadeelectric/the-energyshield-power-for-your-arduino-creativity

author: Kean
author_rank: Unknown
timestamp: March 06, 2014, 11:08:21 pm
content: Clever video, and a useful device (although I don't do much Arduino).But a bit expensive, especially for an international backer.I think the project robot would do well as a KS though - I'd buy one for my nephews (and one for myself...)

author: ivan747
author_rank: Super Contributor
timestamp: March 07, 2014, 12:07:10 am
content: Just one advise. I will say I actually tried to design a li-ion powered Arduino.If you DO add those features, specially solar charging (and USB charging, depends on how you implement it), make it a *separate* version. It is very easy to go too pricey just by adding a couple of ICs. Also watch the current. If you design it to provide 1A to the Arduino, you will have a bad time dealing with pricing. Also be careful with magnetics and DC-DC converter current loops.The Arduino with its 2 linear voltage regulators is not really designed to be power efficient.

author: ivan747
author_rank: Super Contributor
timestamp: March 07, 2014, 12:12:06 am
content: Uhm, and could you please tell me where you get this li-ion batteries from? I'm having a hard time supplying a simple 1000mAh single cell Li-ion with protection.

author: sleemanj
author_rank: Super Contributor
timestamp: March 07, 2014, 12:36:49 am
content: Interesting you've only allocated $10 USD for shipping singles outside US. You know shipping Lipo cells is a problem yeah, hopefully you've done your homework there.Personally, I'd have liked to have seen a hard shell around the cell.

author: aliebold
author_rank: Newbie
timestamp: March 07, 2014, 01:23:42 am
content: @Kean - Thank you. I'm glad you appreciated the video. Part of the expense on Kickstarter is the included shipping. The energyShield will be about $40. We are considering having a Kickstarter for the project robot. There's just a lot of design work to be done on it before it's ready for the public.@Ivan - We are currently working on the design for all of the features. I think we can do it cost effectively. We checked before promising. What particularly are you referring to about the magnetics? The EMI? As far as the inefficiency of the Arduinos regulators, we bypass them, because we supply the 5V (or 3.3v if unlocked).If you just want a couple, you can get them throughhttp://www.powerstream.com/. Powerstream is an American distributor of foreign made (they all are) batteries. If you need 100's or 1000's, track down suppliers onhttp://alibaba.com.@Sleemanj - I appreciate your concern. We have done quite a bit of research about shipping the batteries internationally. I think we finally figured it out. I would like the hard shell as well, I just don't know how to do that easily. I'll look into it.

author: ivan747
author_rank: Super Contributor
timestamp: March 07, 2014, 11:59:36 am
content: Quote from: aliebold on March 07, 2014, 01:23:42 amI was trying to avoid Alibaba, but thanksI was implying EMI, yes. I see you bypassed the regulators, I wonder how well it works when connected to the USB. And if you do supply 3.3V to the Arduino, I wonder how you'll do it. Seems like you guys have most of the product sorted out. I'm guessing you will add all the unlocks after delivering the first batches to the backers.I might use this in a prototype if I can figure out a way to put it in an enclosure. Is this board the same length as a regular Arduino? I mean, will both DC jacks line up if I put them through a project box's wall?Seems like they do.P.S. Oh, and I see your graph showing that the current goes up as the battery absolutely drops (plummets!) in voltage. I would consider it discharged at 3500mV and be done with the hassle. And it goes back to my original point, be careful with promising lots of current. A way to do it would be using high discharge rate batteries. Those don't have protection in them, though.

author: aliebold
author_rank: Newbie
timestamp: March 07, 2014, 01:22:09 pm
content: @mojo-chan - Weareusing a dedicated fuel gauge IC, though I have not noticed any problems. I've attached graphs of the current and voltage during a charging cycle. There is a little bit of noise, but this data is from the fuel gauge. There is a bigger problem that we have with it. If the battery is discharged to the point of the protection PCB cutting off, the fuel gauge's memory resets (it's volatile) and loses the record of charge accumulation. Strangely it doesn't reset to zero. I plan to compensate for this by implementing a Voltage -> Charge look-up table with interpolation and current correction. Then the % will no longer require charge accumulation. The reason I have stayed with a coulomb counter is that I really like having the current and voltage sensing functionality. Now I'm asking myself why I'm using a "fuel gauge" at all... We are currently undergoing a major redesign, so I'll look into other alternatives.@ivan - It seems to have no problems when attached to the USB. The draw on the battery decreases dramatically, but is still present on account of my USB voltage being about 4.85V. We are thinking of using a buck regulator attached to the battery voltage to provide the 3.3V. Though, at this rate, we may have 3 switching regulators in the final design. We are planning to implement the unlocks before sending out any energyShield, though the receive date will most likely get pushed back a little. At present, the energyShield is the exact footprint of the Arduino and the DC jacks line up. However, we are considering different for factors for the energyShield. Possibly making it standard shield length, possibly sitting a little lower. This is just discussion at the moment. Which would you prefer?

author: aliebold
author_rank: Newbie
timestamp: March 07, 2014, 01:25:57 pm
content: @ivan - I Agree completely about the batteries being dead at 3500 mV. I believe the newer batteries I got are protected at 3000 mV. We are thinking of "Rating" it at the safe current (able to discharge completely), but then including documentation for advanced users showing that you can draw more if you use software to limit how far your equipment will discharge the battery. That way low power applications can still take advantage of the last 10% of charge.

author: ivan747
author_rank: Super Contributor
timestamp: March 08, 2014, 01:00:27 am
content: Quote from: aliebold on March 07, 2014, 01:22:09 pmHaving both DC jacks line up a flexible option because you can mount the Arduino and the shield in an enclosure and still have access to both DC jacks. Another way is to make your jack line up with the USB A connector, that way we can leave the Arduino's power jack hidden behind the enclosure wall if we like but still have the USB A connector and the energyShield's power jack too. This trick will only work for Arduinos with USB A. I guess it's a compromise

author: aliebold
author_rank: Newbie
timestamp: March 11, 2014, 04:12:33 pm
content: We use the DS2945. I actually came to the idea of resetting the coulomb count at full charge. The problem is that we do not have a host microprocessor hooked the the energyShield at all times, so we use a pack-side fuel gauge IC. Do you have any suggestions? We're looking for a replacement.Aaron

author: tom66
author_rank: Super Contributor
timestamp: March 12, 2014, 02:47:31 pm
content: How much extra would it cost to stick a little STM8/TinyAVR on there to manage the whole set of controllers?It could act as an I2C slave and then you could use a dumb "pulse" coloumb counter, and internal ADC for Vbat and Vin.

author: aliebold
author_rank: Newbie
timestamp: March 12, 2014, 09:59:50 pm
content: That's an interesting thought. It would be three ICs instead of one, and we would have to get all of the processors flashed. It's worth looking into though. Thanks for the thought!

author: poorchava
author_rank: Super Contributor
timestamp: March 13, 2014, 01:22:22 pm
content: 15k and 20k seems quite high for additional 3.3V out and usb charging, when whole base campaign called for 10k.