Li-ion power mod

alphaseek
Posts: 85
Joined: Thu Jan 19, 2017 5:24 pm

Re: Li-ion power mod

Post by alphaseek »

I'm still waiting for parts to come in, but I think I've found a good way to preserve the 9V barrel connector in case I ever need to use that, and switch between that and the LIPO stuff. I'm planning to follow Morgan Flint's lead and desolder the power switch, cut the existing traces to separate the two halves of the switch, so it will be restored to a DPDT, then connect everything as shown in the pic below. The current OFF switch position will continue to turn OFF the 9V supply, but will connect the charging module to the boost converter input, and the boost converter output to the main board power input. Then what is now the ON switch position will turn the 9V supply ON, but disconnect both ends of the boost converter. I'll have to connect three new wires to the switch pins, but no other trace cuttings are needed.

So if there's no power at the barrel connector, turning the switch ON will turn everthing OFF. :-) But you can still charge the battery - it's just the converter that gets isolated.

Then I have to see if everything will still fit with the barrel connector left in place. But I suspect there will be plenty of room.

Please let me know if you see any problem with this.
Attachments
LIPO Mod.jpg
LupinIII
Posts: 6
Joined: Wed Jan 10, 2018 8:19 pm

Re: Li-ion power mod

Post by LupinIII »

alphaseek wrote: So if there's no power at the barrel connector, turning the switch ON will turn everthing OFF. :-) But you can still charge the battery - it's just the converter that gets isolated.
Then I have to see if everything will still fit with the barrel connector left in place. But I suspect there will be plenty of room.
Please let me know if you see any problem with this.
I don't see any problem, except for the weird switch behaviour. I'm still unsure if I want to remove the barrel connector myself. It does take up quite alot of space and would be a nice place for the boost converter I got (one of those with the multiturn pot - which I already removed). I don't really see myself using the barrel connector anymore, when it can run from 5V USB as well (the charge module I got, can do this - it's one of those like in the very first post or the one used by upsss). It's much more likely to have a USB charger around in a pinch than a 9V supply anyway.

BUT, if you want to keep the barrel jack, I just saw something that I'd use. The socket got an unused contact that is closed when no connector is inserted and opens if you insert a plug. It breaks the ground connection (but that shouldn't matter). You could solder the GND output of the boost converter to that contact, so if no external plug is inserted the boost converter is connected to the 9V input instead automatically. You can still use the switch to break the battery connection to the boost converter in the off position. Only annoyance: in the on position the battery is connected to the boost converter, even if an external 9V is present. So it is idling along and uses a little bit of battery (but the battery charger board should protect from overdischarge even in that case). And just to be on the safe side, only connect external power in the off position, so the boost converter is off. I don't know if the barrel contact opens before the 9V contacts of the barrel plug connect.
LupinIII
Posts: 6
Joined: Wed Jan 10, 2018 8:19 pm

Re: Li-ion power mod

Post by LupinIII »

RobNL wrote:When the batterie full it consume 0.00028 A......OMG, my poor batterie :shock:
Maybe that's because the resistor values you show in your image are weird and make it not work as intended? The principle of those 431 circuits is to short circuit the LED as long as the voltage is above a certain value. That means if the LED is not on, even more current is flowing through the 431 instead. The resistors you chose (3.3k + 4.7k) means your 431 will only start to shortcircuit at above 6V. Not really any useful value for a single cell. Your LED should be on all the time on a single cell. If it isn't you either got the LED or 431 polarity wrong or your 431 is broken.
RobNL
Posts: 122
Joined: Mon Dec 25, 2017 3:11 pm
Location: The Netherlands
Contact:

Re: Li-ion power mod

Post by RobNL »

alphaseek wrote:Then I have to see if everything will still fit with the barrel connector left in place. But I suspect there will be plenty of room.

Please let me know if you see any problem with this.
Remove black lines and you have a free swich contact.
Attachments
switch.jpg
CU, Rob
alphaseek
Posts: 85
Joined: Thu Jan 19, 2017 5:24 pm

Re: Li-ion power mod

Post by alphaseek »

LupinIII, how does your charger module handle running the scope while charging? Does it ever shut down charging while the scope is on? The one I have never shuts down because the current flow never goes low enough to trigger the shutdown. That could be a problem for the LIPO.

I guess what I like about my strange switch setup is that with the switch in one position, the scope is powered by the boost converter, and the 9V input is isolated. And in the other position 9V is enabled and both ends of the boost are isolated. So the two will never mix. Also, all I have to do to install it is to remove the switch and cut two traces, then solder three new wires to the switch pins. I finished the trace cutting this morning, and the worst part was getting the switch desoldered.

I had looked at using the ground switch inside the barrel connector, but found that that switch doesn't quite close when no plug is inserted. But that's just my connector. Yours may work fine. But it means I need to do my switching on the positive side.
alphaseek
Posts: 85
Joined: Thu Jan 19, 2017 5:24 pm

Re: Li-ion power mod

Post by alphaseek »

RobNL wrote:
alphaseek wrote:Then I have to see if everything will still fit with the barrel connector left in place. But I suspect there will be plenty of room.

Please let me know if you see any problem with this.
Remove black lines and you have a free swich contact.
Yes. I finished that this morning. See pic.
Attachments
SW5.jpg
MorganFlint
Posts: 56
Joined: Sat Jun 06, 2015 9:06 am

Re: Li-ion power mod

Post by MorganFlint »

LupinIII wrote:...BUT, if you want to keep the barrel jack, I just saw something that I'd use. The socket got an unused contact that is closed when no connector is inserted and opens if you insert a plug. It breaks the ground connection (but that shouldn't matter). You could solder the GND output of the boost converter to that contact, so if no external plug is inserted the boost converter is connected to the 9V input instead automatically...
That's exactly what I did, see 3rd paragraph at this post and the one before the last picture at this one.
LupinIII
Posts: 6
Joined: Wed Jan 10, 2018 8:19 pm

Re: Li-ion power mod

Post by LupinIII »

alphaseek wrote:LupinIII, how does your charger module handle running the scope while charging? Does it ever shut down charging while the scope is on? The one I have never shuts down because the current flow never goes low enough to trigger the shutdown. That could be a problem for the LIPO.
The charger module not switching off shouldn't matter. It's in its constant voltage phase at that point, so it's the battery itself that "controls" the current (that's just how the chemistry in their works). Sure, you usually don't trickle charge a Li-ion battery, but that's no worse than keeping a cell at 100% by topping it up all the time after it discharged to 95% or something like that (which is what would happen if the charger shuts off). Anything above 85% charge level is very detrimental to the life of a Li-ion cell anyway, so no point in worrying how you keep it at 100%.
RobNL
Posts: 122
Joined: Mon Dec 25, 2017 3:11 pm
Location: The Netherlands
Contact:

Re: Li-ion power mod

Post by RobNL »

The modul I have switch off the batterie if the Voltage of the batterie will be belowe 3V7.
https://www.ebay.nl/itm/USB-Lithium-Li- ... 978851987?
Thats also the problem I have with the low batterie monitor, it never glow up at 3V6 :shock:
If I choose 3V8 or 3V9 the batterie have enough power for at least 6 hours.

BTW, I don't have to use the 9Volt plug anymore, I use the USB-charger input from computer or powerbank to charge the batterie from the shell or work with the shell if batterie is low.

BTW2, this module is better if you want to use the low batterie monitor.
https://www.ebay.com/itm/USB-Lithium-Li ... 2183192848
CU, Rob
alphaseek
Posts: 85
Joined: Thu Jan 19, 2017 5:24 pm

Re: Li-ion power mod

Post by alphaseek »

LupinIII wrote:
alphaseek wrote:LupinIII, how does your charger module handle running the scope while charging? Does it ever shut down charging while the scope is on? The one I have never shuts down because the current flow never goes low enough to trigger the shutdown. That could be a problem for the LIPO.
The charger module not switching off shouldn't matter. It's in its constant voltage phase at that point, so it's the battery itself that "controls" the current (that's just how the chemistry in their works). Sure, you usually don't trickle charge a Li-ion battery, but that's no worse than keeping a cell at 100% by topping it up all the time after it discharged to 95% or something like that (which is what would happen if the charger shuts off). Anything above 85% charge level is very detrimental to the life of a Li-ion cell anyway, so no point in worrying how you keep it at 100%.
Well, I can only say that's not my understanding. I believe the whole point of shutting down the charging process when charging current drops below 10% of the initial charging current is to avoid continuing to apply 4.2V to a fully charged lipo. I've read that if that voltage continues to be applied, the cell will be damaged and may swell up, and possibly worse. I can't prove any of that, but every lipo charging circuit I've seen includes a charging shutdown.

And the problem is, continuous 4.2V doesn't trigger any of the protection circuits. It's not excessive voltage, and it's not excessive current.

Anyway, if this is indeed a problem, I think the solution is to somehow make sure that the USB 5V supply is driving the boost converter directly whenever it's plugged in, as well as of course driving the charger. That would let the battery charge normally, with a shutdown at the end, because the charger would not be supplying any current to the booster. You can do that with diodes, but that involves an undesireable voltage drop. I don't know how this is handled in the many devices that allow charging while running the device, including the laptop I'm using right now.
Post Reply