First Electrical Project, Stuck & Need Some Help - DIY Battery Powered Portable Monitor

Thread Starter

Tarro

Joined Jan 24, 2022
3
Newby here so sorry if this is in the wrong section of the forum or this has been answered elsewhere (I cant get the search function to work for some reason).

I am attempting to power a LCD screen salvaged from a old Ipad 2 with rechargeable batteries by following this tutorial:


The two differences between his setup and mine are:

  1. I am using a different LCD (LP097X02 SLQ1 SLQE SLN1 SLP1 LCD Panel).
  2. I am using 3.7V 2400mAh 103450 Lipo Polymer Lithium Rechargeable Batteries.

I am unable to reliably power on the screen with this setup:

  1. When I use two batteries in series the output voltage of the boost converter drops from 12V to ~4.5V and the controller board receives power but the screen does not power on (see picture).

  1. When I use three batteries in series the output voltage on the charge/discharge board is 6V, the output of the boost converter is 12V and the LCD does power on functioning as expected. However, the voltage throughout the entire circuit will unpredictably drop to ~0.5V sometimes when completing the circuit making the setup unreliable (same setup as picture except there are three batteries in series).

This is my first electrical project so I don’t know what to try next. The issue seems to be a lack of output voltage from the charge/discharge board but despite lots of googling charge/discharge boards of more than 5V output don’t seem to exist…

Any suggestions would be appreciated.

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Components used:
  1. LP097X02 SLQ1 SLQE SLN1 SLP1 LCD Panel
  2. 3.7V 2400mAh 103450 Lipo Polymer Lithium Rechargeable Batteries
  3. TP4056 Single Cell Charger
  4. XL6009 Boost Converter
 

Yaakov

Joined Jan 27, 2019
5,488
Welcome to AAC.

the first thing that strikes me is you are using cheap clip leads which are not a reliable way to get a low resistance connection. When you get the unexpected output, have you tried wiggling the clips to see if it is corrected?

It is the first place I would look, and though it might not be the problem, it should be eliminated as a possible one first. I would consider soldering wires to the modules and using something like Wago connectors so you can avoid this uncertainty. They are very reliably, very easy to use and reuse, and readily available in several configurations.
 

KeithWalker

Joined Jul 10, 2017
2,295
The biggest problem I see is that you are using a different display to the one used in the example. Have you checked that they both have the same driver chips, pinouts and characteristics? If they are not 100% compatible, you can not expect to be successful.
 

Thread Starter

Tarro

Joined Jan 24, 2022
3
Welcome to AAC.
Thank you!

the first thing that strikes me is you are using cheap clip leads which are not a reliable way to get a low resistance connection. When you get the unexpected output, have you tried wiggling the clips to see if it is corrected?
I have tested this by disconnecting and reconnecting each of the clips on each connection and it does not appear to make a difference.

It is the first place I would look, and though it might not be the problem, it should be eliminated as a possible one first. I would consider soldering wires to the modules and using something like Wago connectors so you can avoid this uncertainty. They are very reliably, very easy to use and reuse, and readily available in several configurations.
Those connectors look very useful. Are they able to connect to the terminals on the circuit boards or do they just connect multiple wires? it's difficult to tell from the pictures. If not can you make any recommendations for other components that can?

I will try soldering some of the components together with regular wire and see if that improves the voltage issue. I will post back with my results.
 

Thread Starter

Tarro

Joined Jan 24, 2022
3
The biggest problem I see is that you are using a different display to the one used in the example. Have you checked that they both have the same driver chips, pinouts and characteristics? If they are not 100% compatible, you can not expect to be successful.
I can confirm that the screen works as expected when the controller board is plugged into mains power with a 12V 1A power supply. Unfortunately there is no specific technical information (at least none that I can find) for this or the other screen in the tutorial. I only know from the comments section on the page I bought it from that the screen apparently works with both a 12V 1A power supply and a 9V 2A power supply. Is this what you mean?
 

Yaakov

Joined Jan 27, 2019
5,488
Thank you!



I have tested this by disconnecting and reconnecting each of the clips on each connection and it does not appear to make a difference.



Those connectors look very useful. Are they able to connect to the terminals on the circuit boards or do they just connect multiple wires? it's difficult to tell from the pictures. If not can you make any recommendations for other components that can?

I will try soldering some of the components together with regular wire and see if that improves the voltage issue. I will post back with my results.
The Wago connectors are designed for splicing wires together, not circuit board connections. They are amazingly versatile and reliably handle a surprising range of wire sizes both solid and stranded.

One thing that is very important when deal with multiple interconnections is neatness. You need to be able to easily trace any connection and to be sure that moving a part can't cause connection trouble. A few ohms in the wrong place from a dodgy connection can cost you a lot of time chasing phantom problems.

Developing a habit of taking time to connect things neatly, even for "simple tests" pays back in many ways. I find it also gives me time to think about what I am doing, and sometimes I realize my errors without even needing to apply power.
 

MisterBill2

Joined Jan 23, 2018
11,579
Have you verified the voltages that the display requires? Have you verified the supply voltage required by the driver electronics? Do you have every connection to the drivers and the display correct?
In addition, using a string of power converters like that is far more complex than is good practice.
What you need is a variable voltage supply able to provide the current required.
And, in addition, re-using a display is a very ambitious first project.
 

bassbindevil

Joined Jan 23, 2014
372
In your picture, the TP4056 module isn't doing much, other than acting as a protection module (some '4056 modules include that feature, some don't). It cannot charge cells in series, only parallel. (If you do want to charge cells in series, to 8.4V, the easiest solution is a module that can step up from USB-C to higher voltages; search for "2S 3S 4S 8.4V 12.6V 16.8V Step-Up Boost Lipo Li-Ion DC 5V Type-C Charger" on ebay.)
Getting 5.5V either from 3.7 cells in series or parallel looks wrong. If they are fully charged, they should be sitting at 4.2 volts or so. 5.5V from cells in series would mean one or both are below flat or very high internal resistance, or possibly the TP4056 module is confused by the abnormally high voltage.
The description of the XL6009 boost converter suggests it would be better to run it from 2S lithium (8.4V) rather than 2P (4.2V), but I guess it worked for GreatScott.
 

MisterBill2

Joined Jan 23, 2018
11,579
You have two problems, first it seems that you are trying to power the monitor with a much lower voltage than you have verified that it works on. And second, it seems that those batteries may not have the capacity to power the monitor for any useful length of time.
Understand that a lot of that yoo-toob stuff is faked, and what is being presented is incorrect at best. And because your monitor is not the same, it may have different requirements.
Are you able to measure the current when you power it from either the 12 volts or the 9.5 volts sources? Whatever source you use must be able to supply adequate current for the display to function correctly.
 
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