need info about dc-dc boost converter [closed]

Question

I purchased a "1200W DC-DC Boost Converter Power Supply 8-60V 12V Step up to 12-83V 20A 24V 48V" off eBay. My applications are for charging a DIY 48v e-bike battery I assembled from 78 individual SAMSUNG 25R 18650 2500mAh HIGH DRAIN 25A Rechargeable batteries in 13 cells of 6 each). My other application is as a 40v bench power supply (from 12v) for a motor.

The following minimal documentation, which I assume was translated from Chinese, was included:

DOCUMENTATION:
Supports a wide input voltage 12-60V, 12- 83V wide adjustable output voltage, low dropout voltage.

SPECIFICATION:
Input voltage: 8-60V
Input current: 20A
Quiescent current: 15mA(12V liter 20V, the output voltage, the higher the current will increase too quiet)
Output voltage: 12-80V continuously adjustable
Output current: 20A MAX over 15A, please enhance heat dissipation(input, output pressure related, the greater the pressure the smaller the output current)
Constant Range: 0.5-20A
Working temperature: -40℃~85℃
Operating frequency: 150KHZ
Conversion efficiency: up to 95%
Overcurrent protection: Yes
Short circuit protection: Yes
Input reverse polarity protection: None
Output Counter filling: Yes

NOTE:
1. The input power supply voltage must be above 8V.
2. Do the input power supply switching power supply, the case load of the first connected input source and regulate voltage. Then pick up the load. (Must ensure that the switching power supply has been working), or regulate the first no-load voltage, then switch the power supply open the case. When the voltage is lower than 8V, the chip has not been working. It is easy to MOS tube breakdown.
3. When a constant voltage to constant-current mode have to ensure a constant voltage must be higher than the input voltage.

(end)

Secondary questions:

Q1: What is "dropout voltage"?

Q2: What is "quiescent current"? Why would it be quiet?

Q3: What is "output counter filling"?

Q4: I don't understand 2nd note. Maybe poor translation maybe me. Someone clarify it for me.

Q5: Can I also use this unit as a buck converter?

Now my primary question is about the pots in the image below and how they are used properly.

I can see that "Pot 3" regulates output voltage.

Q6, Regarding pot 1: Adjacent to input with no label, I assume it regulates the input voltage somehow. Can you tell me how and why I would need to do this in relation to the other adjustments?

Q7, Regarding pot 2: Labeled "CC A-ADJ", I believe it regulated the current and realize this is important. My test meter does not gauge amps. How can I practically adjust this for my applications?

Lastly Q8 regarding the battery I intend to charge:

I was told I can charge the whole mass gently at ~52v. I suspect it would be better to charge the 4.7v cells in blocks of 3, if wired to do so. What would be the best method?

Answer 1

A1: I'm... honestly not sure what is meant by dropout voltage in the context of a switching power supply, especially not a boost regulator. Dropout voltage is the difference between the minimum input voltage and the maximum output voltage of a linear (i.e. not switching) regulator. I can only guess they're sticking technical-sounding words in there. (low dropout voltage is desirable in linear regulators, so it's maybe a bit of a buzzword?)

A2: Quiescent current is the current that the regulator draws when there is no load applied to it. It's the current it takes when it's not doing anything, hence the analogy to being quiet.

A3: Not familiar with this term, unfortunately. A google search reveals no useful results. I kind of suspect technobabble.

A4: ... I think that's poorly translated as well. It seems to be saying something about requiring at least 8V input voltage, but it's such a garbled mess that it's hard to follow.

A5: Almost certainly no. Boost converters and buck converters are not interchangeable without adjusting the circuitry, in general.

A6: Without more information on the circuit, I couldn't tell you what that potentiometer is there for. Leave a comment if anyone has any ideas.

A7: This will also probably need more information on the circuit. CC makes me think "constant current", maybe?

A8: This question should probably be a separate question; it's not related to any of the others here, and I don't have an answer for it anyway. I'll leave it for someone else to answer.

Long story short, try to get your components from more reputable sources, where you can actually get good documentation. Digikey, Mouser, Newark, any of those are good sources. eBay and Amazon are not generally the place to go for electronic components.

Answer 2

The adjustment pots on these boost converters work like on a bench supply. One sets a voltage limit, and the other sets a current limit. If either starts to be exceeded, the output voltage will be limited.

Without a schematic I can't tell you what the third pot does. It may be for calibration? Or it could be input current limiting? Hard to say.

To set the output current limit, turn the current pot all the way down (hook up some kind of load to determine which way is down if you have to). Then put your multi-meter in current mode and hook + and - directly to the supply outputs. Your meter is now "shorting out" the supply. You can now turn the current pot up until the multi-meter reads your desired current.

To charge lipos you have to do 3 things.

1. Limit the current to 1C
2. Limit the voltage to 4.2v per cell.
3. Keep the cells balanced.

A boost converter can do 1 and 2, you can simply set the current to 15A or less (2.5Ah * 6). And the voltage limit to 54.6 (13*4.2v).

I would note here that I would not trust such a cheap device to do this safely. If one of the limits fails, it could easily overcharge the battery and burn your house down. The charge voltage also has to be very accurate. If you charge the pack to less than 4.2v per cell, the capacity drops precipitously. If you overcharge it, you risk overheating or bursting the cell.

The 3rd issue is harder. On small packs, like for RC models you can use a balance plug, but 13 leads is too many for that. On large EV packs its more common to use a battery manager that's permanently attached to the battery, often called a BMS. This is probably your best bet. Here's one for example: https://bmsbattery.com/66-bmspcm

..while you're at it you should probably just get an actual charger. They're common and cheap. https://em3ev.com/shop/54v6-charger/