Programmable Lithium Charger Shield for Arduino

Surely you need yet another way to charge your lithium batteries—perhaps you can sate your desperation with this programmable multi (or single) cell lithium charger shield for the Arduino?! Okay, so you’re not hurting for another method of juicing up your batteries. If you’re a regular around these parts of the interwebs, you’ll recall the lithium charging guide and that rather incredible, near-encyclopedic rundown of both batteries and chargers, which likely kept your charging needs under control.

That said, this shield by Electro-Labs might be the perfect transition for the die-hard-‘duino fanatic looking to migrate to tougher projects. The build features an LCD and four-button interface to fiddle with settings, and is based around an LT1510 constant current/constant voltage charger IC. You can find the schematic, bill of materials, code, and PCB design on the Electro-Labs webpage, as well as a brief rundown explaining how the circuit works. Still want to add on the design? Throw in one of these Li-ion holders for quick battery swapping action.

[via Embedded Lab]

An Interview with Tesla Battery Hacker [wk057]

We covered [wk057] and his Tesla Model S battery teardown back in September. Since then we had some time to catch up with him, and ask a few questions.

You’ve mentioned that you have a (non hacked) Tesla Model S. What do you think of the car?

It’s the best car I’ve ever driven or owned, period. Not to get too into it, but, I love it. I’ve put almost 20,000 miles on it already in under a year and I have no real complaints. Software feature requests… but no complaints. After almost a year, multiple 1700-miles-in-a-weekend trips, and an overall great experience… I can never go back to a gas vehicle after this. It would be like going back to horses and buggies.

A salvage Tesla Lithium battery had to be expensive compared to a Lead Acid setup. What made you go with the Tesla?

Actually, if you consider that the Model S battery is already pre-setup as a high-capacity pack, contains the wiring to do so, and the modules are much more energy and power dense than any lead acid battery bank, it’s actually almost cheaper than a comparable lead acid bank and all the trimmings.

I haven’t officially weighed them, but the modules from the Model S battery are roughly 80 lbs. 80 lbs for a 5.3 kWh battery is around 15 lbs per kWh, which is impressive. For comparison, a decent lead acid battery will have a little over 1 kWh (of low-rate discharge capacity) and weigh almost the same.

Also, the Tesla pack is much more powerful than a lead acid bank of the same capacity.
Generally a lead acid battery bank would have a capacity that would only be realized with slow discharges, so, 1/20C. Much over that and you sacrifice capacity for power. 1/20C for an 85kWh pack is only 4.25kW, barely enough for a central air unit and some lights without losing capacity.

Now the Tesla pack can be discharged (based on how it does so in the vehicle) at up to 3.75C for short periods, and at 1/2C continuously without really affecting the overall capacity of the pack. That means I can run 10x more power than lead acid without a loss in overall charge capacity. Leads to a much more flexible battery solution since the loads will, in reality, always be so low that this will not even come into play with the Tesla pack, but would almost always be a factor with lead acid.

Charging is also somewhat better with the Tesla battery. Charge a lead acid battery at a 1/2C and it will boil. Charge the Tesla pack at 1/2C (42kW) and it might warm up a few degrees. Oh, and the charging losses at high rates are much less than lead acid also.
Overall, without continuing to yack about the technical aspects, it’s just a much better battery, takes up less space, weighs less, and has more power available.

There are likely decent arguments for other solutions, but the rest aside, this one won out because it was definitely more interesting.

Click past the break to read the rest of our interview with [wk057]!

Continue reading “An Interview with Tesla Battery Hacker [wk057]”

An Obsessively Thorough Battery (and more) Showdown

There are a number of resources scattered across the Internet that provide detailed breakdowns of common products, such as batteries, but we haven’t seen anything quite as impressive as this site. It’s an overwhelming presentation of data that addresses batteries of all types, including 18650’s (and others close in size)26650’s, and more chargers than you can shake a LiPo at. It’s an amazing site with pictures of the product both assembled and disassembled, graphs for charge and discharge rates, comparisons for different chemistries, and even some thermal images to illustrate how the chargers deal with heat dissipation.

Check out the review for the SysMax Intellicharger i4 to see a typical example. If you make it to the bottom of that novel-length repository of information, you’ll see that each entry includes a link to the methodology used for testing these chargers.

But wait, there’s more! You can also find equally thorough reviews of flashlights, USB chargers, LED drivers, and a few miscellaneous overviews of the equipment used for these tests.

[Thanks TM]

[Charles] Tears Into a Ford Fusion Battery

Any time we hear from [Charles Z. Guan], we know it’s going to be a good feature. When he’s linking us to a blog post with phrases like “If you touch the wrong spots, you will commit suicide instantly”, we know it will be a really good feature. [Charles] is no stranger to Hackaday – we’ve featured his GoKarts, Quadcopters, and scooters before. He was even generous enough to let a couple of Hackaday writers test drive ChibiKart around Maker Faire New York last year.

This time around, [Charles] is working on a power system for chibi-Mikuvan, his proposed entry of the Power Racing Series. He’s decided to go with a used battery from a hybrid vehicle. As these vehicles get older, the batteries are finally becoming available on the used market. [Charles] was able to pick up a 2010 Ford Fusion NiMh battery for only $300. These are not small batteries. At 20” wide by 48” long, and weighing in at 150 pounds, you’ll need 2 or 3 people to move one. They also pack quite a punch: 2.1kWh at 275V. It can’t be understated, taking apart batteries such as these gives access to un-fused lethal voltages. Electrocution, arcs, vaporized metal, fire, and worse are all possibilities. If you do decide to work with an EV or hybrid battery, don’t say we (and [Charles]) didn’t warn you.

As [Charles] began taking apart the battery, he found it was one of the most well thought out designs he’d ever seen. From the battery management computers to the hydrogen filled contactors, to the cooling fan controller, everything was easy to work on. The trick to disassembly was to pull the last module out first. Since all the modules are wired in series, removing the last module effectively splits the pack in half, making it much safer to work on. The battery itself is comprised of 28 modules. Each module contains two 4.8V strings of “D” cell sized NiMh batteries. The battery’s capacity rating is 8000 mAh, and [Charles] found they still took a full charge. Since he doesn’t need the pack just yet, [Charles] removed the final bus bars, rendering it relatively safe. Now that he has a power source, we’re waiting to see [Charles’] next stop on the road to chibi-Mikuvan.

DIY Electricity and Internet for Burning Man


Despite this being [Kenneth Finnegan’s] first Burning Man, the guy came prepared and stayed connected by setting up a beefy electricity supply and a faint yet functional internet connection. If you saw [Kenneth’s] Burning Man slideshow, you know that the desert is but a mild deterrent against power, water, and even temporary runways.

He borrowed a 20V 100W solar panel from Cal Poly and picked up a bargain-price TSMT-20A solar charge controller off eBay. The controller babysits the batteries by preventing both overcharging and over-discharging. The batteries—two Trojan-105 220Ah 6V behemoths—came limping out of a scissor lift on their last legs of life: a high internal resistance ruled out large current draws. Fortunately, the power demands were low, as the majority of devices were 12VDC or USB. [Kenneth] also had conveniently built this USB power strip earlier in the year, which he brought along to step down to 5VDC for USB charging.

Internet in the desert, however, was less reliable. A small team provides a microwave link from civilization every summer, which is shared via open access points in 3 different camps. [Kenneth] pointed his Ubiquiti NanoStation at the nearest one, which provided a host of inconvenient quirks and top speeds of 2-20kBps: enough, at least, to check emails.

Wireless doorbell battery monitor


We know exactly what [Dan] is going through. We also bought a cheap wireless doorbell and are plagued by the batteries running down. When that happens, the only way you know is when people start pounding on the door because you’re not answering the bell. Well no more for [Dan]. He built a backup system which monitors the voltage of the batteries on the chime unit.

You can see the small bit of protoboard he used to house the microcontroller and the UI. It’s an ATtiny13 along with a green LED and a single push button. The idea is to use the chip’s ADC to monitor the voltage level of the pair of batteries which power the chime. When it drops below 3V the green LED will come on.

First off, we wish these things would come with better power supply circuits. For instance, we just replaced the CR2032 in an Apple TV remote and measured the voltage at 2.7V. That remote and the chime both run from a 3V source. Can’t they be made to work down to 1.8V? But we digress.

In addition to monitoring voltage [Dan’s] rig also counts the number of times the chime has rung. Every eight seconds it flashes the count in binary, unless he presses the red button to clear the count. This is shown in the video after the break. We guess he wants to know how many times this thing can be used before running the batteries down.

Seriously though, for a rarely used item like this how hard would it be to use ambient light harvesting to help save the batteries? Looking at some indoor solar harvesting numbers shows it might be impossible to only power this from PV, but what if there was a super-cap which would be topped off with a trickle from the panels but would still use the batteries when that runs down?

Continue reading “Wireless doorbell battery monitor”

Motorizing this trycicle

[Kaj] wanted to help out an aging family member by building them an electric tricycle during international Hack Day back on August 11th. He mixed in some reused parts with some new ones and ended up with bike that lets the rider troll other cyclists. Apparently when serious riders see an older man on a trike gaining on them they pedal like mad to make sure they don’t suffer the embarrassment of being passed. But there’s enough power and range to overtake the strongest of non-powered competitors.

Many of the parts came from a non-functional electric bike sold on Craig’s List. [Kaj] reports that the bike was trashed, but the motor system was mostly salvageable. He replace the batteries and charger and hooked up the motor to the rear axle. The initial install placed everything but the motor in the basket behind the rider. The weight and placement made the thing unstable when cornering. The solution was to house the batteries in a tool box and strap it below the basket. The lower center of gravity makes sure the trike is easy to handle, and now there’s still room in the basket for your groceries.

This would make a perfect platform for some road messages printed in water.