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External battery pinouts?

Looking to 3D print an external batter for my Edge 530. If i use the usb port I would need 5v. That would require two 18650 lithium ion cells in series giving me 7.2-8.4v and a voltage reg to get a constant 5v. How about the pinouts on the bottom mount? I presume the unit is actually 3.6v nominal to a max of 4.2v. Could I use a single 18650 at 3.6 to 4.2 direct to the bottom pins? Didn't really want to take my 530 apart, so I thought I'd ask : ) It would also me 1/3 the size of two cells and a reg.

0 Moosewings over 4 years ago

The manual for the external battery pack sold by Garmin (https://static.garmin.com/pumac/Edge_External_Battery_Pack_ML15.pdf) has some specifications which might help, though not a lot of detail. It claims the output on the electrical contacts is 5.07V @ 1A so it seems like you may actually need the 5V output of the regulator. If you've got a power supply you can probably test it out by starting at a lower voltage and slowly increasing it until the unit starts charging. A low voltage supply *probably* won't do any damage though I can't be certain.

0 Attila over 4 years ago

SRBell said:
That would require two 18650 lithium ion cells in series giving me 7.2-8.4v and a voltage reg to get a constant 5v.

You can also use a small boost converter to get 5V from a single cell. As according to the specs linked by Moosewings, it seems that the bottom pinout might be just a "weirdly shaped USB port" so you could just charge the unit through the normal USB port and a battery bank.

In case you end up designing and willing to share the 3D printed battery connector, please put a link here.

0 SRBell over 4 years ago in reply to Attila

Seems really strange, the 5v output on the out usb port. The battery on the 530, 830 and 1030 are all 3.6v. The other odd thing is the rating 3100Ah at 5v. If it lithium chemistry, that's two cells at 3100mah. That's beyond anything I've seem in a prismatic pouch case size wise. So it's boost or buck, one or two lol. No boost units hand, so it's two cell and a buck regulator it guess. Like my Nukeproof Mega needs anymore weight lol!

0 dpawlyk over 4 years ago in reply to SRBell

SRBell said:
Seems really strange, the 5v output on the out usb port. The battery on the 530, 830 and 1030 are all 3.6v.

The 5v on the output is a USB standard. The external port can be used to charge things that require the USB standard.

The Edge itself uses standard USB charging (what the internal battery is kind of moot).

SRBell said:
If it lithium chemistry, that's two cells at 3100mah. That's beyond anything I've seem in a prismatic pouch case size wise.

The device is really expensive (as far as chargers go; you can get an equivalent one for $10). It wouldn't be surprising if they used a custom battery.

0 mcalista over 4 years ago in reply to dpawlyk

It's kinda weird that the custom connector port on Garmin's Power Pack is 5V. If the only thing it charges is the Edge, it would be more electrically efficient just to take the 3.6V output from the battery pack, and charge the Edge battery at that 3.6V, rather than boosting the output from the Power Pack to 5V, then have the Edge drop that voltage back to 3.6 V. But I guess it is a simpler and safer design if all charging voltages (both the USB port and the 5 port) are the same on the Edge, and all supplied voltages are the same in the Power Pack.

0 dpawlyk over 4 years ago in reply to mcalista

Maybe, the port on the bottom ties into the microUSB port circuitry.

The battery pack can be used as a USB charger for other devices. It has to support 5 volts.

Seems much simpler to just support 5 volts across the interface.