HobyKing 3S 4 Balance Charger Review

July 14, 2011 9:41 | By | Add a Comment

A balance charger strictly for 3S battery packs? What might sound like an insane design choice at first blush does make a lot of sense when you think about the fact that most FPV platforms run on 3 cells, it’s the most popular pack configuration and thus always the first to go out of stock at retailers. But is this charger a hidden gem or a battery killer?

 

The charger has four 3S connectors, supporting two different balance plug types. Total power output is 200W, with a total current of 16 A. There’s a little fan that is not too annoying. One thing to note is that the minimum voltage on the datasheet is 13 Volts. We had no problem running this on the usual bench supplies, but people used to hook up to 11V solar plants will be disappointed.

The plastic case and understated design won’t win any awards. But powering on reveals a gorgeous backlit LCD screen with an insanely high contrast ratio. It is really a joy to look at. Turning the knobs however gets you back down to earth again: they feel mushy and grate against the case. Yeouch.
Worse yet, some of them won’t stop at the limits like they should leaving you wondering whether you are at Zero already or not.

The single button switches the display between charge current, total charge, total voltage and charge time. There is no need for a start or stop button, plugging in a battery means to start the charge, and pulling it out stops it again. The main terminals for the batteries are also conspicuously absent, the only connection you need is your balance connector. Simple is beautiful, though pumping 3000mA through balancing leads is certainly for the more adventurous users.

 

After connecting you can set the charge current with the analog potentiometers. This is a bit too simple: finding the right value is finicky and you can end up pumping 3 Amps into a tiny battery if you forget to turn it down first. But at least the display does tell you the current setting. The display shows “Bal” when it starts balancing, which it usually does in the final stages of charging.

The established charge procedure for Lithium batteries is a two-stage process: First the charger drives a constant current until the cells reach 4.20V each, then the charger applies a constant voltage which causes the battery to draw less and less amps as it fills up. This charger does the same thing, but the constant availability of a current selector knob means that it may surprise the user that he loses control over the charge current at some point. Button-operated chargers usually mitigate this by not making it obvious that you can change the current while charging in the first place.

Build quality of this product is good: Mostly SMD, few discrete parts, the PCBs look clean and tidy. The stacked sub-boards look professional and mate securely with the motherboard. The power cables are quite short (only 15cm) and lack a pull protection, but they do have a protective rubber gasket to prevent insulation damage. A little Atmel microcontroller drives the display and controls the charging, while each charge channel is otherwise independent from each other. Neat!

So, all is well in wonderland, right? Well no.

The unit we received suffered not only from a bad case of potentiometer rash (turning those knobs feels really uncomfortable), but worse: One output was not balancing correctly, and another output did not work at all!

 

You could think this battery is evenly balanced, but when you connect it to a different port…

 

 

…uh oh, not balanced at all.

Either problem is an absolute no-go for a LiPo charger. It simply must stop charging at 4.20 Volts, and it must work to begin with. With a PCB build quality of this level, the problem certainly lies in the QA process. Such faults must be discovered at the factory, especially considering that the user has no way to tune the balancer voltages.

 

The result of the faulty balancer port: One cell overcharged, one not full.

 

The other two functioning ports work flawlessly though, with a 0.006V tolerance.

 

Summary

This charger has some serious quality issues, despite the beautiful insides. We’d like to think that this is a one-off, but frankly multi-port chargers from Hobbyking have an ugly history of not being terribly exact with their balancing. In any case this one goes back to HobbyKing for replacement. There are some nice features like the beautiful display and the no-nonsense operation. What it needs is knobs that are a pleasure to turn, and quality control needs to be ramped up. That this thing can balance correctly is evident from the two working ports.

We will update this review once we receive the replacement unit.

 

Positives

  • High contrast display
  • Simple operation
  • 200W not bad for $50

 

Negatives

  • Quality control issues
  • Knobs are very uncomfortable to turn
  • Imprecise balancer (again, quality control issue)

 

Source

 

 

 

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