Converting an Electric Scooter to Lithium Batteries and Disabling the Safeties

There’s a bunch of different electric scooters available nowadays, including those hoverboards that keep catching fire. [TK] had an older Razor E300 that uses lead acid batteries. After getting tired of the low speeds and 12 hour charge times, [TK] decided it was time to swap for lithium batteries.

The new batteries were sourced from a Ryobi drill. Each provides 18 V, giving 36 V in series. The original batteries only ran at 24 V, which caused some issues with the motor controller. It refused to start up with the higher voltage. The solution: disable the safety shutdown relay on the motor controller by bridging it with a wire.

With the voltage issue sorted out, it was time for the current limit to be modified. This motor controller uses a TI TL494 to generate the PWM waveforms that drive a MOSFET to provide variable power to the motor. Cutting the trace to the TL494’s current sense pin removed the current limit all together.

We’re not saying it’s advisable to disable all current and voltage limits on your scooter, but it seems to be working out for [TK]. The $200 scooter now does 28 km/h, up from 22 km/h and charges much faster. With gearing mods, he’s hoping to eke out some more performance.

After the break, the full conversion video.

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Storing Energy in Liquid Form

Researchers in Singapore have created a new kind of redox flow battery with an energy density around ten times higher than conventional redox flow batteries. Never heard of a redox flow battery? These rechargeable batteries have more in common with fuel cells than conventional batteries. They use two circulating liquids separated by a membrane as an electrolyte. Each liquid has its own tank, and you can recharge it by pumping in fresh electrolyte. The redox in the name is short for reduction-oxidation and refers to the process that stores energy in the two liquids. You can learn more about flow batteries in the video from Harvard below.

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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]

Hack a Mag-Lite to be Rechargeable

rechargeMaglite

Most tools sport rechargeable batteries these days, but there’s no need to toss that old flashlight: just replace the cells with rechargable ones!

[monjnoux] had a 3-cell D-sized MagLite lying around—though you could reproduce this hack with a 2 to 5 cell model—which he emptied of its regular batteries and replaced with some 11000mAh NiMHs from eBay. The original bulb was also tossed in favor of a 140-lumens LED.

After disassembling the flashlight, [monjnoux] set about installing the new parts. He replaced the original bulb with the LED, soldering it into place and securing it with hot glue. He then drilled a hole in the body of the flashlight for a DC socket. The charger he purchased is adaptive, detecting the number of cells and adjusting its voltage accordingly. It had the wrong connector, though, so [monjnoux] simply chopped off the end and soldered on a new one. For a hack that comes in at 40€, it’s definitely a cheaper alternative to the official rechargeable model: which costs 80€. And with a duration of 7 hours (though it’s unclear whether this number reflects continuous use), it likely outlasts the official model, as well.

The ins and outs of Lithium-based battery packs

lithium_batteries

So, you’ve got your awesome project built and are ready to take it on the go, but how are you going to power it? You could use a couple alkaline cells or perhaps swipe a Litihium battery pack from some infrequently used portable device – however before you do that, why not check out what [Lady Ada] has to say on the subject?

The detailed tutorial on her site discusses the different types of Lithium-based batteries and their form factors, as well as the strengths and weaknesses of each type. Voltage ratings are covered, as well as why it is important to choose a Lithium battery pack that fits the task at hand. The dangers of improperly handling batteries are clearly noted, highlighting the importance of selecting a proper charger and resisting the urge to ever wire Lithium batteries together to increase capacity.

While the bulk of the information presented is nothing new to most of our readers, it’s definitely a worthwhile read for those just starting to use Lithium battery technology in their projects.

Solar batteries

solarbatt

[Knut Karlsen] put together a prototype set of solar rechargeable batteries. He always seemed to have batteries laying around on his worktable and figured they might as well be charging. The flexible solar cells were given to him by researchers at the IFE and are rated at 1.8V. He used superglue to secure them to the C cells. A silver conductive pen plus flat wires from a Canon lens connect the solar cells to the battery terminals. The batteries just trickle charge for now, but he’s going to try to build cells with built in charge controllers in the future.