Li-ion power mod

Re: Li-ion power mod

Postby RobNL » Sun Feb 18, 2018 7:49 pm

I hope this explane something, I have a all in one board.
https://www.ebay.com/itm/USB-Lithium-Li-ion-18650-3-7V-4-2V-Battery-Charger-Board-Protection-Boost-Module-/192183192848

Your booster is disconnect in off mode, you don't need it in off mode.
The lipo is connect to the booster in on mode.
The lipo in connect to charger + protection in off mode, so in off mode you can load the batterie.
In on mode you can't use the load + protection, you don't need it.
If your batterie is empty, you can use the barrel.

BTW, the extra diode is sometimes allready on the boostermodule.
Attachments
Switch.jpg
CU, Rob
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Re: Li-ion power mod

Postby alphaseek » Sun Feb 18, 2018 8:15 pm

OK, I understand. And since your all-in-one board outputs 9V, you need that diode anyway.

Well, I'm going to leave mine the way it is, but your way is certainly a good way to go for others considering doing this mod.
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Re: Li-ion power mod

Postby Tugo » Sun Feb 25, 2018 11:28 am

alphaseek:
Sorry for my late reply.
I attached a couple of pictures (main board, analog board).
I hope they are self explained.
In case further explanation is needed, please let me know ;-)

Regarding noise problems: I tested everything with just 9V battery and what I have and there are differences, but not that much that I would want to change it.
When I started to build this I had significantly noisier signals.
I don't know what happened but it is way better now.
You can add an extra capacitor on the output of booster.

Do you have new or old analog board?
I have an old one and I did a modification that is explained here.
But I left both electrolytic capacitors in the board.
Attachments
Digital board.jpg
Analog board
Main-side view.jpg
Main board - side view
Main board.jpg
Main board
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Re: Li-ion power mod

Postby alphaseek » Sun Feb 25, 2018 5:30 pm

Tugo wrote:alphaseek:
Sorry for my late reply.
I attached a couple of pictures (main board, analog board).
I hope they are self explained.
In case further explanation is needed, please let me know ;-)

Regarding noise problems: I tested everything with just 9V battery and what I have and there are differences, but not that much that I would want to change it.
When I started to build this I had significantly noisier signals.
I don't know what happened but it is way better now.
You can add an extra capacitor on the output of booster.

Do you have new or old analog board?
I have an old one and I did a modification that is explained here.
But I left both electrolytic capacitors in the board.


Thanks very much for the pictures. There seems to be plenty of room for everything.

I have the old boards too. Adding the 78L05 and 79L05 seems like a good thing to do. In fact, JYE's new analog board does exactly that. So I think that's an officially approved improvement. I haven't done that yet, and may not bother. I made some noise-reduction changes described by Toshi in his PDF posted here back in July I think, and at least on the test signal it looks pretty smooth now, even powering from the battery and boost converter (without any extra filtering). So I'm pretty happy with it the way it is. The changes he suggested are:

1. Remove C7 (120pF) from the analog board, and add it to the main board in parallel with C6.

2. Add a wire connecting AGND on the analog board directly to DGND down near the bottom of the main board, so AGND doesn't have to go through the J4 header.

3. Replace the 0-ohm jumper R18 on the main board with a 10-ohm resistor. Further isolation of analog signals from digital noise.

4. Remove R21 and R22 (100K each) on the main board. These were needed only for the initial pre-build power-up test, but after that could leak digital noise into the analog signal ADCIN.
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Re: Li-ion power mod

Postby LupinIII » Sun Feb 25, 2018 10:12 pm

I just finished my battery mod. And because I found it easier to mount stuff I built a case out of wood ;) .
I'm using one of those micro USB charger boards (with over charge and over discharge protection) and a boost converter with a chip labeled B6287. Both are available on ebay (https://www.ebay.com/itm/400665524431 and https://www.ebay.com/itm/311563536624 for example; lot of other sellers are available). I removed the USB socket from the booster board (not needed in my case) and replaced the potentiometer with SMD resistors to get 8.3V. The nice thing about these two modules is that they are exactly the same width and fit nicely in line. I have no issues with noise at all, at least not more than expected. The main source of noise seems to be the screen anyway. Btw. is there an "F" revision of the analog board (DSO bought end of November on banggood) or is that just a case where the silkscreen printed weirdly? Because mine says "-00F"

I don't know how long the 850mAh battery will last, but I'm not planning to use the scope continuously for more than a few minutes anyway (it's a mobile debug tool) and if I need it anyway the charge module charging while using it. To check the battery voltage I have a thick copper wire besides the USB charge port cut flush with the case. I can touch that with the scope probe to measure the battery voltage (it's connected directly to the positive battery terminal so I put a 10k resistor in series just in case the copper pin would be touched by a grounded wire).

I cut the traces under the switch so the second pair of contacts switches power to the boost converter (first set of contacts switches power to the scope as usual). I soldered the negative output of the boost converter to the normally closed contact in the barrel jack. In case you plug in an external supply the boost converter is disconnected (but still on, because of the power switch it's powered from the battery). I didn't bother to make a hole in the case for the barrel connector though, because I don't know what I would use it for now (but still left the barrel jack on just in case).
Attachments
20180225_215133k.jpg
DSO wood Shell battery voltage measurement
20180225_215303k.jpg
DSO wood Shell battery voltage pin
20180225_212225k.jpg
DSO wood Shell internal
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Re: Li-ion power mod

Postby UnKaiF » Tue Feb 27, 2018 6:16 pm

Hi guys !
Some geek's comics:
bad design.png

Look at DSO150 little closer:
dso150_simplified_power_flow.png

Yes, we are guilty of global warming. :lol: What now ?
right design.png

Something else ? Yes !
perfect design.png
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Re: Li-ion power mod

Postby RobNL » Tue Feb 27, 2018 6:32 pm

I have a 20 A powerbank........ones loaded power for live 8-)
CU, Rob
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Re: Li-ion power mod

Postby alphaseek » Thu Mar 01, 2018 12:16 am

I think the geek's cartoons have some valid ideas. But when I tested my 1300 mah battery, I finally just gave up after five hours when the battery was down to about 3.8V and the scope was still running strong. So while it certainly isn't efficient to produce a regulated 3.3V from 8.3V, you reach a point where it's just simpler to do it the easy way if that's plenty good enough.
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Re: Li-ion power mod

Postby UnKaiF » Thu Mar 01, 2018 5:41 pm

So, I don't like to join debates, but:
1. We are geeks, I think. We, usually, do not looking for "easy way", right ? :)
2. It is so difficult - to replace TWO components ?
Advantages:
1. Increased battery lifetime [or/and] small size battery can be used. (More free space in the case.)
2. Low power | low cost | small-sized boost converter needed.
upd
3. Lower boost current = lower noise.
Last edited by UnKaiF on Fri Mar 02, 2018 3:48 pm, edited 1 time in total.
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Re: Li-ion power mod

Postby upsss » Fri Mar 02, 2018 5:24 am

@UnKaiF, first let me say a few good thinks about your ideas. I like your clear drawing especially the 2nd one where you point out the potential excessive power losses. Eliminating the original series diode at the power input is a no-brainer. This original diode was there for reverse polarity protection and since we have a wired battery, there is absolutely no need for it now and its power loss. Powering the display back-light from the 3.3V is a good idea which could add ~30 minutes of battery run time. Originally the power supply was external so saving ~100 mW wasn't a big deal.

As far as regulating the 3.3V supply directly from the Li-Ion battery, it is a bad idea. Draining a Li-Ion battery down to 3.0V or even 2.8V is perfectly acceptable, 2.8V would be the worse case condition with most common Li-Ion chargers like the TP4056. Regulating the 3.3V supply directly from the Li-Ion battery as you are suggesting, your new LDO 3.3V regulator will stop regulation under worst condition with battery voltage of 3.6-3.7V, at that point the battery still has a lot of capacity left and you probably would end-up with worst battery run time than if you power the 3.3V regulator from the output of a step-up converter.

BTW, my DSO runs with my 1340mAh battery for about 4.5 hours, I never left the series diode in my circuit and my step-up converter was set way too high ~8.8V (I didn't have the right programing resistors). If you have a trim pot to adjust the step-up converter output or the right programming resistors, you can set the output down to ~7.6V without any problems and gain probably another 45-60 minutes of run time.
Last edited by upsss on Fri Mar 02, 2018 4:48 pm, edited 1 time in total.
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