Lipo Shim not working with a specific battery type


#1

HI All, hoping someone can help me.

I’ve got a [LipoShim] and 2 batteries, a 3.7v Lipo 1200mAh, and a 3.7 Lipo 6600mAh.

At the time in question the 6600mAh is reading 3.92v, and the 1200mAh reading 3.82v.

plugging the 6600mAh into the LipoShim, all is well; the blue LED lights and the pi(zero w) boots as expected. Plugging the 1200mAh in the LED does not light, and the Shim makes a hi pitched whine.

(I’ve tried with a second battery of the same type as the 1200mAh and that’s doing the same, apart from with this one the lipo shim light comes on, but it makes a complex buzzing whining noise and the pi doesn’t boot)

I can power other devices from either battery, and my charger reports them both as in good health.

Can anyone suggest a reason that the 1200mAh might not be gettign along with the LipoShim?

Thanks.


#2

You’re measuring the no-load voltage of the LiPo- my best guess is that as soon as the Pi + LiPo SHIM are connected and try to draw a large current, the voltage is likely dropping below the off-threshold of the circuit, or perhaps even causing it to oscillate on/off.


#3

Thanks for the suggestion. Any ideas why might this be? Are the 2 1200mAh Lipos likely to be dead? Is the fact that they manage to power another device, an Adafruit Flora, likely to be the current draw on the Flora is significantly lower?

TIA


#4

The Flora is likely to require one to two orders of magnitude less current than the Pi, depending on application, since it’s specifically marketed as a low-power microcontroller.

For example a Pi 3 can be expected to top out at 700mA with a low of 230mA

The chip on the Flora- the ATMega32U4 - might require about 7mA.

The whole Flora platform at full pelt is likely to never need more than 100mA (excluding external accessories) although Adafruit seem to estimate its current consumption at a maximum of ~30mA. The chip is capble of running at much lower than even these figures under the right conditions.

So, yes, you could say significantly :D A rough best guess puts the Pi idle power consumption at about 10x that of the Flora’s maximum.

The LiPo is probably not dead, it’s just junk. Such is the minefield of Amazon batteries!

Oh and in the interest of referencing my sources:


#5

Thanks again for taking the time to reply.

I’ve now ordered a 2200mah Li-ion and 1200mah Lipo form Pimoroni. Fingers crossed I get better results with these.

I’ll keep the cr***y amazon Lipos for lower power devices.