MK2 Modifications:
What modifications are done?
The 3.3V power supply to the on-board clocks is
separated, isolated &
 now supplied from a battery. By doing this the power to the clocks is very clean & low noise.. It is also independent of any noise that may be generated on the PS by other chips. The on-board 3.3V regulator is changed for a very low noise regulator with a high power supply rejection ratio (PSRR) out to the MHz range. This powers the clock handling output stages of the Xilinx CPLD chip. 

Is the modified Hiface now separate from the computer's power supply?
Yes, the 5V from the USB connection is no longer used by the Hiface. This means that the modified Hiface is no longer effected by the quality of the PS from the PC. The USB cable now only carries USB signals & ground - no power is transferred through it. The modified Hiface is more immune to the type of USB cable used - standard USB cable being fine. 

What batteries are being used?
These are Lithium Nano Phosphate (LiFePO4) batteries. This is a new & safer formulation of Lithium battery technology. It has nearly the same power to weight ratio as lithium batteries but doesn't have any of the safety issues or fire hazards associated with Lithium Ion batteries - there is no risk of fire or explosion from these batteries.

How long do the batteries last before needing replacement? 
A longevity of 15 years is given by the manufacturer, A123, for high current usage such as power tools or electric vehicles. Our low current use should ensure an even longer lifetime. 

How long do the batteries last before needing a re-charge?
Because the battery is now only powering the clocks, a charge should last for about 3 days or more of continuous play BUT the batteries are only being used when the unit is turned on. 

Do these batteries need a special handling/charging regimen like other batteries?
No, these batteries do not suffer from memory effects like others & don't need to be drained fully & then re-charged. They can be used straight away without any special consideration.

Will they explode or catch fire if I overcharge them?
No, but they will die like all batteries! I had a user who unknowingly was using a battery charger putting out 7.2V to charge them (my 2 batteries are in parallel & so only need a max 3.6V charge). The batteries survived for a while before finally dying. They didn't catch fire or emit any noxious fumes - simply overheated & died. On examination one battery endcap had partially come off the end of the battery (it still measured 3.2V).

Will it damage the batteries if I deeply deplete them?
No, but it's not a recommended practise. The manufacturers recommend that they are not deeply depleted (<2.7V) in high current situations as this effects their longevity. In our low current usage this is less of a worry, possibly not a worry at all but I still recommend to avoid this!

What happens if the batteries run out during listening?
The sound will simply stop, maybe crackle a little bit first. There is no voltage spike or loud sound that will cause damage to your speakers or ears! 

Battery Charger:
What battery charger is used?
There is now an battery charger inside the modified Hiface box which only needs an external 9V to 12V external power source - see below  

When/How are the batteries charged?
When the Hiface unit is switched off the charger will automatically top-up the batteries until full & then switch itself to standby where a tiny trickle  of charge is being applied. Charging the batteries regularly like this is not a problem for these batteries i.e. it won't shorten their lives.

External Power Supply:
Some consideration should be given to the external 9V to 12V power supply. Yes the switched mode power supplies that come with most modern appliances  WILL PROBABLY DO - you know the light ones. But it is better to use a better quality PS i.e. probably one with a transformer in it (i.e heavier). Remember, this is the feed for the 5V & 3.3V regulators in the MK2 modified Hiface box so the cleanest possible power is advisable. 

A suitable UK 9V DC supply is £14
here  but others may well be available locally in your area.
A suitable US 9V DC supply is $10 here but again others may well be available locally in your area.
What you need is 9V to 12V DC supply of 500mA or greater output with a 2.1mm plug with positive centre contact.
You could also run this off a 12V battery using an adapter plug like this or this, again respecting centre pin is positive polarity.