Please provide veryfied lipo batteries with matching connector for sourcing in germany and probably anywhere else

[dbrgn]

Yeah, I had to learn the hard way that reversed polarity will kill at least some of the boards (I fried a Pysense board because the cables from aliexpress did not match the convention of most batteries...)

[fuchs7]

This one also works and fits in the expansion board case:

https://eckstein-shop.de/PKCELL-LiPo-Akku-Lithium-Ion-Polymer-Batterie-37V-2000mAh-JST-PH-Connector

[lollisoft]

@fuchs7 Thanks, yesterday I have ordered the 2500mAh version. Btw, the battery that I have was rechargable after a complete discharge to 2.1V. But I had to use a separate charger. Thus the Expansion board can't recharge the battery after the low voltage is reached. This is a downside and probably a design issue for the board. To recharge the battery, I have used a Seed Studio Lipo Rider Pro.

[Colateral]

@lollisoft Depends on battery bank protection (small chip) that you have on it.

[fuchs7]

@lollisoft I'm not an expert but I think discharging a LiPo battery to 2,1 V is far below any specs.

E.g., the PKCELL battery I linked has a protection circuit that will cut off the battery at 2,4 V (see http://ecksteinimg.de/Datasheet/LP803860 2000mAh 3.7V 20161116.pdf part 13.2). But the official discharge cut-off ist much higher, at 3.0V.

This should be the spec sheet of the charger chip on the expansion board: http://www.ti.com/lit/ds/symlink/bq24040.pdf Unfortunately I'm not sure I understand it with regard to the minimum battery voltage required. My impression is there is no specific voltage required but if your battery had a protection circuit and it triggered perhaps it appeared completely "dead" (=0V) from the viewpoint of the charger?

[dbrgn]

These connectors also match and could be soldered to a LiIon cell, e.g. a 18650.

https://www.banggood.com/100Pcs-Mini-Micro-JST-2_0-PH-2Pin-Connector-Plug-With-120mm-Wires-Cables-p-1147298.html?rmmds=myorder

Note though that with this product the colors are reversed, so you either need to solder on the battery in reverse or simply swap the two cables (quite easy to do).

Edit: Yes, 2.1V is really low and will probably shorten the life of the cell. This link is also interesting: http://lygte-info.dk/info/BatteryLowVoltage UK.html

[lollisoft]

@fuchs7 I think it really has a protection for under voltage. The page did mention this: https://www.amazon.de/gp/product/B071NW4F8J/ref=oh_aui_detailpage_o04_s00?ie=UTF8&psc=1
I was unaware that it also has this under voltage protection.

The following data sheets document the characteristics and thus my battery survived.

Battery data sheet: http://www.mouser.com/ds/2/813/850mah-en-1.0ver-1090518.pdf
DW01-P data sheet: http://www.haoyuelectronics.com/Attachment/TP4056-modules/DW01-P_DataSheet_V10.pdf

The problem is with the charging chip at the prototyping board. It is unusable for the scenario where it get fully discharged.

Conclusion: The charging chip is propably meant for a different battery type. Propably two NIMH cells in series: https://electronics.stackexchange.com/questions/35869/at-what-voltage-is-a-nimh-battery-empty

Apart from the polarity (what every maker should check), the battery is ok, if a different charging board is used (Seeed Studio LiPo Rider Pro).

I'll test the combination in the next days using the 2500mAh battery, Lipo Rider Pro and two different solar modules.

[fuchs7]

@lollisoft I think the charger on the expansion board is exactly right for your battery but the chip probably does not detect your battery when protection has been triggered (battery detection is Fig.14 in the bq24040 spec sheet).

Is there a way to turn off the *Py when battery voltage is low to avoid deep discharge?

[dbrgn]

@fuchs7 said in Please provide veryfied lipo batteries with matching connector for sourcing in germany and probably anywhere else:

Is there a way to turn off the *Py when battery voltage is low to avoid deep discharge?

That is being discussed here.

[jmarcelino]

@lollisoft
The charger chip is designed for Li-ion batteries, however it is just a charger chip it doesn't do battery undevoltage protection.

From what I understand what's doing undervoltage protection is the TPS2115A power multiplexer, but that isn't designed around the batteries at all, just what works for a typical device being powered. So the LiPo "protection" may be a side effect.

In any case make sure you always use protected cells. You can also check the battery voltage through the ADC and when it goes too low have your code go into extended deepsleep.

[lollisoft]

@jmarcelino Was the battery type (Li-Ion) anywhere documented regarding the charger chip? That all should be by the vendor.

I would probably combine the expansion board electronics with the LiPo Rider Pro. But I don't like to put too much unnesecary chips onto the board. I am not yet aware of
charger and protection circuits (as discussed in my other thread https://forum.pycom.io/topic/1671/expansion-board-lipo-save-power-down-function-so-save-lipo-undervoltage)

Assembling these two boards and connecting them with another USB cable is ok for prototyping, but nit ok for a end product - so to say :-)

What about a KiCad project on github? Collecting circuits for various aspects? And documenting application notes for combining them into new ones?

Btw, I have ordered three ADS1115 4 channel 16 Bit converters to monitor these voltages. It get's an interesting project...

What is not yet clear to me is the fact that batteries probably have their own undervolt protection, that could nock out the remaining circuit so that it stops
recharging in an undervolt situation, if not properly designed.

So for my experiment, could I put the Seeed Studio Lipo Rider Pro battery connector in parallel to the expansion board battery connector and put there then the battery?
If that is possible, I could keep switched off the step up converter for the USB port on the Lipo Rider and save me a USB cable :-)