When you think about it, LiPo chargers are tremendous things. They turn the potentially lethal task of rejuicing your batteries into a completely safe process (usually). All the while, they're monitoring each cell to prevent your mancave from turning to napalm.
Like most tech wizardry, these magical boxes have come leaps and bounds in just a few years. A bit more than a decade ago, a 1000 watt charger was virtually inconceivable. Today, this powerhouse can be had for about £80. Hook it up to a sufficiently capable power supply and in less than an hour, it'll sort out batteries big enough for next door's lawnmower, updating you with live info on each cell's voltage and impedance (a check of the battery's overall health). All on a full colour screen in a box a bit larger than a beer coaster.
So why am I not interested? Because I feel that modern chargers are sorely lacking in one key area.
I bought my last charger, a Cellpro 10s, in 2008. Compared to most modern models, it's the size and weight of a fridge. But it has something called 'Auto 3C', and this is an absolutely fantastic feature that very few of the new kids seem to have.
You will probably be familiar with setting the charge rate for your favourite battery. A 1000mah battery set to a 1 amp charge rate will be charged in an hour. Set it to a 2 amp charge rate and it will either be charged in half an hour or you'll come home to a fiery mess, depending on what 'c' level the battery is rated for. 3c? 20 minutes. 4c? 15 minutes (and a pretty darned hot battery). You get the idea.
Auto 3c does away with all of that. You just plug up your battery (power leads, balance leads) and press '3c charge' on the charger. This tells the charger, "Look, I don't care how you do it, but get this bugger ready in 15-20 minutes.".
What happens next seems peculiar if you're not familiar with auto charging. The charger will initially feed in current at a very slow rate-say 0.2-0.5c. During this time, it's assessing how much current the battery can take (it's usually more than you might think). It then automatically regulates current input for the rest of the charge-and the results can be very surprising. Typically, as soon as the charger is finished testing the battery out, it will whack up to 10-15C rate for a brief period-say 1-3 minutes. This is pretty scary if you're seeing it for the first time; I've witnessed 10 amps being shot into a little 800mah pack, and I'm pretty sure I shat out a kidney. (If you're unfamiliar with 'c' terms, then it's roughly equivalent to shoving a firehose into a hypodermic syringe). Trust me, the charger knows what it's doing. It gradually drops off the charge rate, monitoring cell behaviour for anything abnormal, and finally cuts the current off in the usual way.
No, the batteries do not suffer shortened lifespan as a result of this apparently drastic charge method and no, I've not had any fires in more than 10 years worth of charging. As far as I can tell, the only slight drawback is the occasional error situation that occurs when the charger can't decide what the pack's true state of health is. In this situation, the charge simply stops. Remember that this charger is older than Noah, so I feel that a few non-mancave-burning hiccups is forgivable.
Having this level of automation has saved me countless hours of head-scratching over this-and-that current setting, and it's especially useful in the field when you're rushing through things and more preoccupied with racing than charge rates. Nor do you have to worry about the battery's maximum 'c' rating, which several manufacturers don't bother to tell you anyway. I've put several '1c' batteries on auto 3c with no fireballs yet.
So here's my call to LiPo charger manufacturers: Listen up. Auto charging is a simple feature that would make a lot of people's lives easier, especially for those who have just joined the hobby. Whilst I'm no expert in advanced charging algorithms, it doesn't sound that tricky to implement and it could potentially prevent a few fiery mancave infernos.
Perhaps you know a good reason why this feature is no longer used. Maybe it's unsafe, or simply not needed? If so, leave a comment below. Otherwise, do share this with anyone who might be interested-the faster the word spreads, the more likely manufacturers are to listen up.
Thinking caps on, boffins-the RC geeks need you.
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