MKR1400- Battery Issues- Support needed

Hi Guys

Im Markus from Germany. I want to use the MKR1400 for an IoT Project.
I connected over the IC2 Port a temperature sensor, OLE Display 0.96 zoll and GPS. Both sensor are connected to 5 V Pin Port.
So far everything works fine while MKR1400 is connected to USB Port and Im able to sent the data to the cloud.

However my intent is to connect the MMR over a LIPO. Therefore I bought over Ebay a LIPO with 3.7 Volt and 2500 mAH. I connected the LIPO to the Port to charge the LIPO which worked well. I can measure with the power meter on the LIPO between 4.0- 4.2 Volt, which look like that the LIPO can be re-charged ordinary.

I encountered now the issue if I operate the MKR over the LIPO only it doesn't work.

  • Has someone an idea how I get this device operated over a battery?
  • Can I use a simple an other options ?

Thanks, Markus


I believe the battery is meant to work in conjunction with a main power source which can supplied via USB or a DC source (applied to the Vcc pin). The intent of the battery is to provide an additional current source for the current spikes that are encountered during GSM data transmission/reception.

The power management design of this board is complex and not very well documented. In some ways I believe there is a design flaw here as the interaction of the battery with USB power or external power is odd and not well thought through. After experimenting with this board and seeing lots of issues, I have concluded that
the battery must be present even if the board is powered via USB or via the VCC pin.

As far as I know the board does not function with the battery alone.

ok thanks for your comprehensive answer. :slight_smile:
Does it mean that that I need both power supplies.
One LIP0 3.7 Volt directly connected over the plug, plus another LIPO for example 18650 (see link) connected to VCC Pin?

Do you mean VCC Pin or VIN Pin (See comment below)? In the manual they are saying that a further supply should be connected to VIN only.

In case that supply supply it over the VCC/VIN Pin, will be the plugged 3.7 LIPO charged?

During cellular transmissions, the peak current required by the board will exceed 500mA. This is in excess of what can be sourced by a standard USB port, so it is MANDATORY to have a 1500 mAh or higher LiPo battery plugged all the time, the current provided by the USB port will be supplemented by the battery. When powering the board using Vin, a 5V power supply that can supply at least 2A is required.



  1. Yes you are correct that the external power is supplied via VIN. You need the battery for reliable operation regardless of the capacity of your power supply supplying Vin.

2)My understanding of the power management system on the board will automatically charge the battery when power is available. So therefore if you use Vin together with a battery things should work fine.

In my case, I increased Vin to 7V because I did not want to deal with the battery. I know this is not consistent with the manual, but after multiple tries that was the only way to ensure reliable GSM Connectivity without a battery.

Hope this helps


For the record, I've had sketches run on MKR GSM 1400 whilst only supplied with a 3.7V LiPo, both connecting to Arduino IoT and my own MQTT broker.

What I did find out today (on a MKR WAN, but likely same behaviour) is when I connect the MKR GPS shield via the serial connector, the supply pins on that connector read:

  • 5V when connected to USB + LiPo
  • 1.3V when connected to LiPo only

In the latter case, the main board (WAN/GSM) runs as per normal (although on WAN the green onboard LED does not come on), however the GPS shield does init, presumably as it runs under V. If you have a line of code in your sketch waiting for new GPS data (e.g. while(!GPS.available()), the program will be stuck there.

Not sure if this is the case of the OP (as you mention you've got GPS on the 5V supplied pin), but wanted to drop this in the discussion as well. What's your reading on that 5V pin when only connected to LiPo?