Zbig
lvl.4
Flight distance : 7349 ft
Poland
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M1dn1ght N1nj4 Posted at 2017-9-15 10:42
Chill out, it's a joke. Sounds like it was a bit over your head.
Anyway, just having an MCU does NOT mean the firmware is upgradable. Also, nearly every other type of battery charger, "smart" or not, does not have any form of user accessible firmware. It has software that runs on a chip, but it has one job, and does it just fine. The dock is nothing more than a distributor of power. The batteries themselves can choose whether or not to accept more incoming power, as they have their own chip on board.
M1dn1ght N1nj4, I'm sorry if my post came across as aggressive. Internet posts don't always convey the tone accurately and yours didn't occur to me as a joke. Being non-native English speaker doesn't help me much, I figure. But to the point.
You're perfectly right that, in most cases, a charger is a glorified constant voltage power supply. The actual charging control logic usually sits further down the line: it's in the phone in case of a (smart)phone and in the battery itself in case of DJI's intelligent batteries. But I have strong reasons to believe there's some additional trickery going on in the Spark's charging hub; let me elaborate. The DJI's own FAQ states the following for the battery charging times: "52 minutes for one battery, 55 minutes for two batteries and 85.2 minutes for three batteries with the battery charging hub." Now, let's take a closer look at the batteries' specs: 11.4V rated voltage (3S HV), 1480mAh capacity which gives us 16.87Wh of stored energy. And the charging hub's AC adapter specs: 13.05V, 3.83A (50W). The batteries take little more than 50 minutes for a full charge which means the initial CC charging phase is carried out at the current higher than 1C (1480mA). The current tapers off in the CV phase (as the battery has reached its terminal voltage) so you have to start with a current considerably higher than 1480mA per battery. In case of up two two batteries, 3.83A / 2 = 1.915A per battery so it's all fine and dandy. But as soon as you put the third battery, you'd need more than 1480mA * 3 = 4440mA and that gives us 58W - way over the 50W power budget of the supplied brick. And, as we established, we charge at more than 1C initially so this is a best case scenario. That is why I'm confident there's additional logic in the charging hub that sequences the power delivered to the individual batteries in the case of charging three of them. Given the level of technical advancement of the rest of the DJI's stuff, I can assure you they're not relying on the overcurrent safety measure built into the PSU (SMPS's usually just drop out under overcurrent condition, anyway). Also, as stated in the manual, the hub is able to signal the fault conditions using its colored LED and you do need an MCU running - however complex or simple - firmware for that. All that is why I honestly don't get it why you guys would prefer it to be non-updateable. Just pretend that micro-USB is not there for the time being; chances are, in the future you'll be grateful it's there after all ;)
Cheers!
Zbig |
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