Xl6009 low ampere output

Other Hardware General Electronics
1

I hope I didn´t miss any previous posts about the XL6009 step-up, but couldn´t find anything that suits my problem:

I´m trying boost 2x Lithium ion batteries in series to achieve a 32V output 1100ma. I measured the amperage and got 500mA .

I'm using Samsung 18650 25R batteries, they are capable of providing 20a each, while xl6009 is only drawing 1amp from each battery.

So what am I missing?

The load is 35w.
Xl6009 draws 3a at 12v when connected to dc adaptor.thats 36w
Xl6009 draws only 2A at 8v when connected to lithium ion batteries. That's only 16W

2

The load?

3

The setup works with dc adaptor instead of batteries. The problem only occurs when I use batteries

4

That would require a 32V / 7.4V = 4.3x step up and a current of about 5Amp from the batteries, which is beyond the switching capacity of an XL6009.
Leo..

2 Likes
5

I thought it's rated for 75w . It works well with 12v adaptor.

Is it possible to use two xl6009 to get 32v 1100ma

6

7.4v 2.2amps is 15w. When 15w is converted to 32v 400ma with 95% efficiency.

I don't know how it's close to 75w rating. Why does this work with 12v dc adaptor? Why not with 7.4 batteries

7

12V > 32V = a 2.66x step up, which is easier than a 4.3x step up.
Supply (input) current gets lower with increased input voltage.
Leo..

8

The adapter does two things, it gives you more current capability and you are boosting the voltage a lower percent.

That is 35 watts or 2.7 amps from the adapter. I expect with that load and the impedance of the batteries, connections, etc you are getting less volts and need more current.
Best to get bigger or more batteries.

9

I'm using Samsung 25R batteries. They can provide 20amps.

10

Yes the supply current becomes lower with voltage.

This doesn't explain why xl6009 only drawing 15w from batteries while it draws good 35w from dc adaptor for the same load.

The only difference is batteries are at 8v, dc adaptor is at 12v. According to xl6009 spec sheet it operates between 5-32v input range

11

Read the datasheet.
The switch inside the chip has a 4Amp limit.
Leo..

13

I read the spec sheet. Isn't the 4amp limit is for max output current?

Even if we assume it's for input, 8v 4amp would be 32w. It should be drawing 32w from batteries not 15w.

8v is within the operating limit of 5-32v. It works with 12v adaptor, it's draws 3 amps, that's 36w.
Only with batteries it draws less amps if the load is 35w, then it should be drawing 4amps with 8v source

14

No, the 4A is the limit for the internal switch.
And that switch isn't 'on' all the time in boost mode.
So input (battery) current must be kept well below 4A.
Can't you use three LiPo batteries in series.
Leo..

15

I don't have 3 batteries. I only have two.

If the max amps is 4A then isn't it supposed to draw 32W from batteries instead of 16w. That is 4A from 8v source.

It draws 3A from 12v dc adaptor.

I don't understand why it's drawing only 2A from 8v source

17

You can read and calculate the needed duty cycle of the 4A switch here.
Leo..

18

Are you using one of those cheap boards you buy off the internet or is this a design you made from scratch?

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image1022×1022 64.1 KB

If the former, it just not designed to boost 7.4 to 32V with 1.1A output. You are lucky you got 500mA

19

Hi, @diyenthusiast
Welcome to the forum.

Can you please post some images of your project, with the batteries connected.

What actually is the load?

Thanks.. Tom.... :smiley: :+1: :coffee: :australia:

20

Yes.its the booster. it's not able to boost 8v to 32v with 1.1A. it can boost 12v to 32v with 1.1A

21

That is correct.
So if you need to boost 7.4V to 32 with 1.1A you need to find a different board.

22

Adding a third battery solved the problem.