What I am about to describe should be used at your own risk. Warranty could be voided but no specification is given by Mackie or condition regarding power supplies. Since I have no schematics or part numbers for the DC to DC converters used in the DL I cannot state with certainty that the input voltage ranges are exceeded. I can however state that no adverse effect was noticed in the use of the battery and the unit operated normally. Typically boost and buck converters have a large input voltage range. Heat would be my biggest concern but with a battery operating voltage range of 12.9 to 12.0 V a +- 3.5% range I would not be concerned. Later I will describe the solution to shift the voltage range. I would only recommend usage in the cycle mode (battery only) not in the trickle charge (floating charge) mode which would incur higher voltages and require an AC source for operation. This also eliminates potentially unwanted ground loops that would otherwise be introduced.
The battery I used (a car battery or flooded lead acid type) is not useful for a permanent solution for this application. It would last only about 150-180 cycles. It was strictly used for test purposes (proof of concept). The type of battery recommended is the SLA (Sealed Lead Acid battery) deep cycle type as used in battery backups. These will provide 800-1000 cycles over their useful life. Based on the draw of about 2 - 2.3 amps for the Dl1608 and a wireless switch the capacity I would pick is 35 -50AH (20 hr. rating) such as the PowerSonic PS-12350NB3 (~ $65) which should last a good 3.5-7 hrs. for a 20-40% capacity discharge. Although not a deep discharge type you must balance cost and weight with battery life and I find this a good balance for this application. The AH rating is in the range of operation recommended for maximum battery life. If your typical gig is only for a few hrs. I would adjust the capacity to match your requirements but not lower than 35 AH. Keep in mind that a capacity level of 60% of the original specification after a full charge is considered end of life for the battery. Lead acid batteries have no memory effect and should be stored fully charged and recharged every 6 months if stored or continuously float charged. Typical charge times are 1.75 x discharge time, so for a use of 7 hrs. it would take about 12 hrs. to fully charge with a microprocessor controlled charger (smart charger). This is also a requirement for long battery life and to avoid overcharging. A great resource for more detail on SLA's is found on PowerSonics web site SLA Technical Manual. Measuring voltage is a poor indicator of charge state. I recommend a cooking timer for less than $10 (19hrs + range.) as a monitor for usage and charge as long as the battery is fully charged to start with. Locate the timer near the power switch of the DL as a reminder to log usage.
It helps to have a lab supply that can test the unit from the 11.0V to 13.0V as I did. I found no change in performance and current load remained about the same or lower for higher voltage but still around 1.8 -2 amps. Temperature remained steady. The battery setup included a two pole switch DPDT. the battery on the center terminals and one side for the DL the other for the charger. This keeps charger voltages from the DL. To keep the paranoid 12V crowd happy I used one of the oldest tricks in the book to reduce DC voltage a silicon rectifier diode 10 amp @ 1000V (cause that's what I had) 3,6, 10 amps are common values. This dropped the DL in voltage to 12.1 volts under load in my case. This voltage should remain above 12.00V for the duration of the recommended discharge period of 20-40%. The typical drop for the silicon diode is between .7-.8 V. under the load. I also added a small RC filter after the diode to smooth out the battery noise. Yes batteries are noisy. The cathode points to the DL for those not familiar with electronics. All electronics are between the switch and the DL including the ferrite bead on the cable.
I will do some additional measurements on leakage etc. later on.
