I just put some headers on top of each other. Basically it is still just “standing” in its previous headers - but higher up.
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First and foremost… It let’s you customize end-of-charge voltage**. So you could charge your cells to, say, 4.15V instead of 4.20V. Also lets you charge any series configuration with a single charger (9S, 10S, 12S, etc)
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It’s possible to build a 4+ amp charging system for less than the price of an equivalent charger. For example, a 12S 4A charger on eBay was something like $85 after shipping from China. Also, the system can be made from “Amazon-ready” parts. So if you’re in the US, you could have your parts in 2 days, rather than a month
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DIY or bust!
**Note: The voltage on most of the fixed-voltage PSU’s can be tuned slightly. There is usually a small potentiometer inside the case that let’s you adjust from, for example, 50.4 (4.20V/cell) to 49.9 (4.16V/cell)
All makes sense to me except number 2. I think what you’d be making would be a power source and not a balance charger no? Why not just get a bulk charger that will do 8 amps at 50 volts for 60$. And its somewhat adjustable to different voltages
Yeah it’s not a balance charger. You still need a BMS. It is basically just a Constant-Current / Constant-Voltage power supply with easily adjustable user-specified outputs. The DROK regulator has numerical control for the voltage and current, so you can accurately and reliably change the output with a few button presses, instead of turning a tiny screw on a potentiometer.
That said, I decided to stick with a 2A fixed-voltage laptop-style charger (~$35 plus a month wait from China). I personally don’t need a variable voltage PSU at moment. And even though it takes longer, charging at a slower rate is better for the battery
You could just get any kind of DC power supply (lap top bricks would work to) and hook it up to a digital dc-dc boost converter… And you got ur self adjustable (current and voltage) charger for less then 25$ Very nice stuff for charging everything u have in house… Adjustable voltage and current is realy helpful sometimes
I am not that electronic savvy. I have a Genssi 36V PS I wanted to do the “R33” mod on. I opened it, read posts, but I have no idea how to track down the correct resistor to add a POTI to. I adjusted the supply down to the required 33.6V (max of 4.2V per cell for 8S). I would like to get a maximum of 4.5 A out of the supply to go into my BMS and battery pack. BMS is rated at 5A for charging.
Using Ohm’s Law:
V=IR >> V/I=R 33.6V/4.5A = 7.4666Ohms
Therefore, couldn’t I just put a large 8ohm high-wattage resistor coming out of the negative terminal on the supply which would limit the maximum current to around 4.2 A (using ohms law again…33.6V/8ohms = 4.2A)? This would limit what the BMS draws from the supply and the BMS would do all the balancing of my battery…right? Right!!! 
**Edit - I want to use the existing PS since I already opened it and voided being able to send it back…
The resistor close to the positive output will control current
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I do have this charger http://www.ebay.ca/itm/361851978526 The only problem with it is that it overcharges my battery up to 42.7V I’ve opened it but there doesn’t seem to be any potentiometer in it… Has anyone already dealt with this charger? Is there a resistor I can change in order to adjust the final voltage? If it helps, i can upload pics of the inside of the charger…
Anyone EE’s here have any idea on what I may need to do to adjust the output voltage on my charger? I’m guessing I mess with one of the 3 potentiometers in the pic?
EDIT: found out the upper right potentiometer changes voltage, not sure what the other two do though.
If you have an Enertion fast charger or charger with similar circuit board layout, FYI!
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Can I get The link to your 65w power supply?
I used an old laptop psu - don’t have a link sorry. I upgraded to a 90W Lenovo one now which fit even better
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link to new one? also thanks for the insanely fast reply!
Again: had that lying around and have no link. It is also not factored into the price as I figured everybody has an old laptop PSU somewhere.
one last thing - about how long does a full charge take with the drok and your laptop psu?
All depends on charge current and battery capacity. With 90W I can charge my 10S battery at ~2A. Now divide your capacity by 2A and you’ll have the time it takes
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Can you explain how you wired the laptop psu to the drok
It’s a DC psu - you just connect GND and POS to the corresponding input on the Drok.
something like this ? http://www.ebay.com.au/itm/DC-DC-Converter-Module-Adjustable-Step-Up-Boost-Power-Supply-DC8-5V-48V-Input-GL-/282146588265?hash=item41b13f4669:g:FJIAAOSw9NdXu9ES
that one should work in principle though setting the voltage is a PITA with those potentiometers. I’d try and get one with digital settings
So you need some kind of DC splitter adapter?