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Juggular

Charging at lower voltage?

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Okay, my Dyson's charger died.  The charger's output was 26v at 0.8A.  I ordered a new one.  But in the mean time, I didn't want the LiPo battery to die of hunger.  So I plugged in a 12v 6A power supply (for iMax B6) for half an hour. That's less than half the voltage.  It did charge up. 30 minutes won't charge fully. But it got enough juice to stay alive for few days.  

This got me curious. Can this be done for RC batteries?  What would be the limit?  

My understanding was that for a 7.4v battery, you'd want something higher.  8, 9, 10, 11 volt.  Like water running from higher place to lower place, the height difference would allow the electrons to flow into the lower voltage battery.  Amp is just how wide the waterfall is (thus how quickly it gets charged).  

But what I did with Dyson is like charging the 7.4v battery with 3.6v.  How did it charge?  Because of greater amp?  Does that mean if I have 3.5v 100A charger, I could charge any 7.4v?  Even 11.1v batteries?   Or does that mean that 7.4v battery will only be charged up to half because the charging voltage is half?  Would there be an equalizing point?  Like no matter how long you charge at lower voltage, you won't ever charge fully or something?  

Anybody has any idea? 

 

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There's a couple of important differences between the RC battery and the battery in the Dyson.

1. It's probably a Li-ion battery rather than a LiPo so will be a bit more robust (and cheaper) for consumer use. 

2. Consumer devices have the charger built in, where as RC batteries don't.

If the Dyson needs a 26V input I suspect it has a 6s Lithium battery. 12V alone is much too low to even start the charge on one of these, let along add anything useful. Which makes me think that the Dyson has a built in transformer that allows it to charge from an under-volted power supply. Unless what you thought was 30 minutes charge was just 30 minutes being plugged in with hardly any difference made in practice.

The difference is amp rating won't affect things. The Dyson's in-built charger will pull the amps (or more likely watts) that it needs. Considering the original power supply is rated at around 20W, and on the assumption it has a transformer that can deal with lower voltage supplies, you only need the amps to be inversely proportional to the voltage.

My new ISDT charger can handle a DC input between 10 and 34V for example. And it can charge up to 6s.

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