Internal battery

#1

Hi,

For the moment I am powering my axos with a USB battery inside my casing (through step up DC-DC to the barrel connector). It makes the device portable, but I needs to open the cover to load the battery.
For my current build I would like to go a step further using a lipo battery and charger.
I would like:

  • to keep the cover closed as much as possible.
  • the battery to be charged every time the micro usb is connected. I don't mind that the core is 'on' in order to charge, but that would be a nice extra.
  • the battery to power the core when no usb is connected
  • being able to switch off the core.

I was wondering whether following system would work.
Is there a problem connecting the outputs of the charger directly to the step up DC-DC module? I can imagine voltage swings during charging. Will this have an effect on the core?

Thanks for the input!

#2

why don't you connect the usb power out directly to 5v? no need to step anything up there.

#3

Hi lokki,

That would indeed be much more elegant.

I did it this way because I was not sure whether the automatic switching between powered by barrel connector (power supply part) / micro-sub was going to work when the battery lowers under 5V. I have read somewhere Johannes claiming that the barrel connector needs 7+ volts in order to take control. I was unclear to me where this logic is happening.
I did not want to fry anything.

So I am unsure whether:
- this 5V pin can be used both as output or input for 5v?
- if I feed 4,75v into the 5v sockets, will the core auto-switch (from micro-usb to this input) like it does with the barrel connector?

Did you mean something like this?

image.jpg703x584 114 KB

Thanks!

#4

I would use the 5v pins between the midi section and the main board:

But you could check with a multi meter if these pins you suggest and the ones I suggest are connected.

#5

Hi Blindsmyth,

I have checked the circuit files and these seem to be connected. I'll measure tonight to be sure.
tnx!

#6

@Blindsmyth,
I have measured and can confirm these pins are connected.

@lokki
Do you think my second sketch should work?

tnx all

#7

sorry for late answer...

i don't think there is any switching between 5v and usb-supply.

you can feed 5v to that pin though, it is bidirectional.

i am unsure about your exact needs. do you need to plug the axoloti in to reprogram it regularly or do you want to use the usb-micro port just for charging?

it still feels like the easiest solution would be to hook a power bank to the usb-port directly (if you don't need to reprogram it) and charge the power bank via its own usb client input.

#8

Hi lokki,

I indeed need to sketch my use situation.
I like walking around with my synths, hence the battery. But I don't like the micro usb cable sticking out. I think the connector is too fragile. Therefore I keep the battery inside my enclosure. For my other 2 axo's I use a USB power bank inside the enclosure (which I can open to remove the bank to charge).
On the other hand I regularly (almost daily :wink: connect them to the Patcher. That is why I like the battery to be charged from the micro usb power, so I never run out of battery power. This would really be an ideal situation.

Great that the 5v pin is bidirectional, thanks for confirming.
I used the StepUp module in my previous axo's cause if you feed 12v through the barrel connector the core switches fluently from usb power to barrel DC power and vice versa when the battery is empty/removed.

I would like to be sure though whether it would be a problem to connect the battery to 5v and plug in the micro-usb in the same time since there is no switching mechanism...

#9

Hi all,

this weekend I ended up doing it like this (I needed it to be done to proceed with some other stuff..):

image.jpg1044x360 128 KB

The chargers usb port is exposed at the back of the enclosure, together with the switch that serves as on/off switch when working of battery power (still allowing it to keep charging)
The downside is I need to attach a usb cable to the extra chargers port to start charging, but I can live with that.
I skipped to path taking power from the axo for the charger. Since usb is only 500mA I liked the idea of separating it and having a dedicated charging usb line...

Thanks for the help!