A Li-ion Battery Charging Guide

Li-ion Battery Charging

Although [pinomelean's] Lithium-ion battery guide sounds like the topic is a bit specific, you’ll find a number of rechargeable battery basics discussed at length. Don’t know what a C-rate is? Pfffft. Roll up those sleeves and let’s dive into some theory.

As if you needed a reminder, many lithium battery types are prone to outbursts if mishandled: a proper charging technique is essential. [pinomelean] provides a detailed breakdown of the typical stages involved in a charge cycle and offers some tips on the advantages to lower voltage thresholds before turning his attention to the practical side: designing your own charger circuit from scratch.

The circuit itself is based around a handful of LM324 op-amps, creating a current and voltage-limited power supply. Voltage limits to 4.2V, and current is adjustable: from 160mA to 1600mA. This charger may take a few hours to juice up your batteries, but it does so safely, and [pinomelean's] step-by-step description of the device helps illustrate exactly how the process works.

[Thanks mansalvo]

Tesla Model S Battery Teardown

tesla-batt

Tesla Motors club user [wk057], a Tesla model S owner himself, wants to build an awesome solar storage system. He’s purchased a battery pack from a salvaged Tesla Model S, and is tearing it down. Thankfully he’s posting pictures for everyone to follow along at home. The closest thing we’ve seen to this was [Charles] tearing into a Ford Fusion battery. While the Ford battery is NiMH, the Tesla is a completely different animal. Comprised of over 7000 individual lithium-ion cells in 16 modules, the Tesla battery pack packs a punch. It’s rated capacity is 85kWh at 400VDC.

[wk057] found each cell connected by a thin wire to the module buses. These wires act as cell level fuses, contributing to the overall safety of the pack. He also found the water cooling loops were still charged with coolant, under a bit of pressure. [wk057] scanned and uploaded high res images of the Tesla battery management system PCBs (large image link). It is a bit difficult to read the individual part numbers due the conformal coating on the boards.

A second forum link shows images of [wk057] pulling the modules out of the pack. To do this he had to chip away the pack’s spine, which consisted of a 2/0 gauge wire potted in some sort of RTV rubber compound.

We’re sure Tesla doesn’t support hackers using their packs to power houses. Ironically this is exactly the sort of thing Elon Musk is working on over at Solar City.

Galaxy Note 2 gets three and a half months of standby time

bat

In the quest for the ultimate Android device, [白い熊] on the XDA developers forum created an awe-inspiring monstrosity that gives his Galaxy Note II 288 Gigs of storage and enough battery to theoretically last three and a half months.

First, the storage: the phone can now store movies, videos, apps, and music on an incredibly capacious 256 Gig SD card. Yes, this card currently sells for about $500, but having that much storage space effectively turns the Note into a portable hard drive running Android.

The battery comes direct from an eBay listing that advertises 8500 mAh inside a huge Li-ion battery. It’s extremely doubtful this battery will live up to the stated rating, but even if the new battery has twice the capacity as the stock battery [白い熊] is looking at about 10 weeks of standby time.

Yes, it’s just parts bought online and thrown together, but you really have to admire the sheer ostentatiousness of this phone.

Laptop running on a sealed lead acid battery

steupup_box

[Viktor's] laptop needed a new battery; he had the trade off between carrying around a cheap but heavy sealed lead acid (SLA) battery, or buying an expensive but light Li-Ion battery. Figuring his old laptop was pretty heavy already, and having an unused SLA available, re-purposing it for his laptop wouldn’t be too much of a hassle. Using a boost converter he built out of a custom dip MAX668, he is able to output the necessary 5 amps required. An MC 34161 voltage monitor chip is planned for future revisions, but he’s currently running it just fine. Check out some of his other cool hacks on Karosium.

Related: MSI Wind extended battery

Adjustable breadboard supply

breadboardpowersupply

adafruit industries’ latest product is an adjustable breadboard power supply kit. We’ve seen breadboard supplies before, but like most of adafruit’s kits, this is the best design you’re going to encounter. It uses an MIC2941 voltage regulator instead of the more commonplace LM317. It has a very low dropout which means your output voltage can be much closer to the input voltage. Their example is using 3AAA or a Li-Ion battery for an output of 3.3V. Input can be through a barrel jack or terminal blocks. There is a selection switch for 3.3, 5, and adjustable voltage. Using the adjustment pot you can select an output voltage anywhere from 1.3V to within .5V of the 20V maximum input. The adjusted output voltage will remain the same even if you increase the input voltage. Like all of their kits, you can find schematics, assembly and usage instructions, on their project site.

Unique Li-Ion battery tester

battery

[moris_zen] found himself with a hand full of Li-Ion batteries and no good way to see what their capacities were. He built a this unique tester really quick to get the job done. He’s using off the shelf components and a cheap pocket watch which he bought in Taiwan for $1. You hook the circuit up to your battery, click the button and the watch starts working. When it stops, you multiply that number by .38 to get your amp/hour results. Sure, he could have just used a counter, but this is an interesting approach. All he needs to do now is make a nice container to hide all of the circuitry. How could he change the circuit to make the end multiplication unnecessary?

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