Electronics > Beginners
9V LiPO charging circuit
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alex-sh:

--- Quote from: Zero999 on February 14, 2019, 09:19:29 am ---
--- Quote from: alex-sh on February 13, 2019, 08:23:42 pm ---Yes, it is 2S. This makes it easy.
I did notice another issue though. Minimum voltage in my case should be 7V.
9V LiPO has a cut-off voltage of 5.5V. This is too low for me. This means I cannot use full battery capacity.

I think this has to be abandoned in favour of a single 3.7V cell 2000mA. More juice and easy setup with a 9V boost converter.  Did anyone use this module:

https://www.ebay.co.uk/itm/USB-Lithium-Li-ion-Lipo-Battery-Charger-Module-3-7v-4-2v-Boost-Step-Up-5V-9V-12V/192683311240?hash=item2cdcd20088:g:q5cAAOSwt6Nbzb-t

Cheap and I suspect is probably rubbish?

--- End quote ---
Why not swap the LM7805 with a low dropout regulator?

http://www.ti.com/lit/ds/symlink/lm2940c.pdf
http://www.ti.com/lit/ds/symlink/lm1085.pdf
http://www.taitroncomponents.com/catalog/Datasheet/LM78D25.pdf

--- End quote ---

I cannot change it as the pcb is done and components are placed and I suppose there is no point - 95% time project will be powered by the external PSU. I am more concerned now about 5% - charging circuitry and the battery.

PS I did just notice a few of the above LDOs have TO-220 package (my pcb footprint). I am going to order LM2940CT-5.0
Zero999:

--- Quote from: alex-sh on February 14, 2019, 09:48:31 am ---
--- Quote from: Zero999 on February 14, 2019, 09:19:29 am ---
--- Quote from: alex-sh on February 13, 2019, 08:23:42 pm ---Yes, it is 2S. This makes it easy.
I did notice another issue though. Minimum voltage in my case should be 7V.
9V LiPO has a cut-off voltage of 5.5V. This is too low for me. This means I cannot use full battery capacity.

I think this has to be abandoned in favour of a single 3.7V cell 2000mA. More juice and easy setup with a 9V boost converter.  Did anyone use this module:

https://www.ebay.co.uk/itm/USB-Lithium-Li-ion-Lipo-Battery-Charger-Module-3-7v-4-2v-Boost-Step-Up-5V-9V-12V/192683311240?hash=item2cdcd20088:g:q5cAAOSwt6Nbzb-t

Cheap and I suspect is probably rubbish?

--- End quote ---
Why not swap the LM7805 with a low dropout regulator?

http://www.ti.com/lit/ds/symlink/lm2940c.pdf
http://www.ti.com/lit/ds/symlink/lm1085.pdf
http://www.taitroncomponents.com/catalog/Datasheet/LM78D25.pdf

--- End quote ---

I cannot change it as the pcb is done and components are placed and I suppose there is no point - 95% time project will be powered by the external PSU. I am more concerned now about 5% - charging circuitry and the battery.

PS I did just notice a few of the above LDOs above have TO-220 package (my pcb footprint). I am going to order LM2940CT-5.0

--- End quote ---
The pin-out of the regulators I suggested is exactly the same as the LM7805, so no modification of PCB layout is necessary.
alex-sh:

--- Quote from: Zero999 on February 14, 2019, 11:30:48 am ---The pin-out of the regulators I suggested is exactly the same as the LM7805, so no modification of PCB layout is necessary.

--- End quote ---

I have noticed it too. Thank you
If I used 9V boost converter, there is no need to have an LDO.
I need to come up with a battery charging circuitry first I think.
Peabody:
Do I understand correctly that the Soshine "9V" battery cannot be balance charged?  If the only connection to it is the 9V connectors, there's no way to charge the two cells individually - no connection to the point where the two cells are connected in series.
alex-sh:

--- Quote from: Peabody on February 14, 2019, 07:59:43 pm ---Do I understand correctly that the Soshine "9V" battery cannot be balance charged?  If the only connection to it is the 9V connectors, there's no way to charge the two cells individually - no connection to the point where the two cells are connected in series.

--- End quote ---

That's correct. In fact, this is not only Soshine. Other 9V LiPO PP3 batteries are the same - there are only two contracts "-" and "+" and that's it.
IMHO I do not understand why even bothering with balance charging. This is not a very expensive LiPO for a powerful quadrocopter or a car.
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