Droid 4: 4 Gold Pins Under Rear Cover – Successful 5V Charging at 1.5A

Hey all,

Connected a current limited power supply to Gnd and Vin on the back of my Droid 4 (pin lower right = gnd, pin lower left = Vin) at 5.0V and I had literal fast charging occurring. Screen showed charging, amperage was around 1500mA to start scaling down to 1300mA-1100mA as it reached full charge. It seems to pass through the Lithium Ion battery charging circuity so appears to be a safe way to dump in lots of power. Obviously these pins are designed to pick up power from the rear inductive charging cover that Motorola produced, but I wanted to try just pure 5.0V power.

I’m thinking of grabbing some extra rear covers and making up some drop-in charging stations or alternative inputs (like solar/etc.)

Nice to get away from having to charge on the USB Micro connector.

This seems like a VERY good thing if someone was building an external battery pack that fit onto the phone (like the one for the iPhone)…you could power it on, charge via this connector, and shut it down whenever you liked. The power draw on the phone drops off massively once it is charged so if you started with a full charge, it could float the battery all the way to empty.

Time to experiment šŸ™‚

Again, for reference:

Bottom right (when viewing back, camera at the top):
Gnd is Lower Right – Nearest the microUSB connector
Vin is Lower Left – Opposite side from Gnd on the bottom row

Don’t hit it with too much voltage! I limited myself to about 4.8V and 1700mA max. šŸ™‚


Vita Spa Part Cross Ref

It took me some time to find this info, so I’ll post it here in-case anyone gets in the same spot as me.

I found that my recently acquired Vita Elan SPA with dual 4HP pumps had one pump unplugged. Plugging it in resulted in the discovery that the pump was locked up. IĀ disassembledĀ and found the impeller failed/exploded on the motor shaft and rubbing on the housings.

The original 56Y framed wet ends for the 4 HP motors are obsolete. The parts themselves are also difficult to locate (and rather expensive) so the general recommendation is just to swap out the whole wet end with something ‘newer’


The newer Vita Spa’s use a 310-1740 wet end (impeller + housing + cover + wear ring + seals). It appears the main difference between the stock older NLA units and the newer 310-1740 is that the output fitting was shorter (new style is a little longer). The threads/mounting/etc. is otherwise the same so it should be a direct swap fit. This is a cross reference from 423038 VITA part number that is listed on their part sheets/catalogs.



VITA P/N: 423038

Generic P/N: 310-1740

Description: 56Y Frame 4HP Wet End w/ 2″ inlet/outlet (3.1″ if measured with a tape measure).