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20th November 2021
Comparison of various battery types (plotted on https://www.rapidtables.com/tools/bar-graph.html#) . The NiMh battery varies in capacity from 600 mAh upwards (All data Wikipedia)
AA battery capacities as listed by Wikipedia. The 9 V has low capacity in all its forms, although providing high voltage.
When D size rechargeable batteries are factored into the equation, the difference is clear: 10,000 mAh. (Amazon)
The 4 AA batteries are now down to 4.9V presumably down from 6V the day before. Sound is listenable, in fact I am listening to music but the sound is distorted under the highest volumes. Heating is non existent.
19 November 2021
A continuous hum from the power supply unit of my N2 amplifier resulted in a a temporary switch to 9V battery power. The battery was measured at about 7 volts and ran the amplifier for about an hour. A brand new battery of unknown brand was measured at 10.0 Volts and later measured at 5.7 Volts an hour later. The greater the capacity, the less the battery will run down, and stop powering the system.
A 9V battery is rated at about 400 mAh. Costs aside, the AA batteries are rated at about 1000 mAh or so. A review of recent review of rechargeable batteries showed that many of them were performing at about 1000 mAh below their rating, which was about 2000 mAh. AA batteries in general have a greater capacity and even the rechargeable batteries of this size follow this trend.
At the moment I ma using 4 x AA batteries brand new and running at 6 V. It remains to be seen if the batteries last an entire day, if they do, they can be replaced with the rechargeable NiMH batteries which in any case have a similar capacity. Actual testing will tell, but calculations have given encouraging results.
Music is clear and loud with the class A purity.
21 November 2020
Further testing: I attempted to charge carbon zinc batteries using a 9V battery using the instructions in the video, with the batteries back to back. The results were surprising: one battery started at 1 V and ended up at 1,2 V and the other battery decreased to 0.5 V. The charge did not hold steady for ling, dripping to about 1.1 V.
Attempting to hook up two batteries in parallel was better than using two used batteries in series (only marginally) two 9 Volts, but the sound quality showed distortion and this did not work, Apparently when even one of the 9V batteries is discharged to 4 volts or less, it will not power the said TE 2025 amplifier at all, and in series it cause distortion although the
Using four AA batteries in series in a battery holder worked very well for the amplifier but these batteries were removed for another purpose, but using the 'recharged' batteries in the pack did not work out well at all.
At present I am looking into making a battery holder for the D six batteries that should last more than the 9 Volts batterers which have lasted 2 or 3 days at the most. Is this borne out by the specifications of popular batteries?
9 Volt batteries have usually about 400 mAh. This advertisement seems to support this claim:
9V Rechargeable Battery Pack, LP 2-Pack 600mAh Li-ion 9 Volt USB Battery with Micro USB Charging Port for Alarms, Wireless Microphones, Smoke Detectors, Toys, Flashlights, Guitar, Keyboard & More
Another manufacturer states
BONAI D Rechargeable Batteries 10,000mAh 1.2V Ni-MH High Capacity High Rate D Size Battery Rechargeable d Cell Batteries high Capacity(8 Pack)
The information bears out the the fact that the D six batteries (we will need 6 of them ) and that is only up-to 9 Volts, actually 4 of them which will give 6 volts, will in fact last 8000/400 (conservative estimate) 20 times the life of the 9 Volt battery which anyway was not new when it was obtained that is 4 x 20 = 80 days, or 3 months at least. This is enough time to build a home made battery.
Running an amplifier off a battery, or off a clean power supply is supposed to result in better sound. I have been running my TEA 2025 based amplifier off a 9 Volt battery for 3 days. The initial voltage of about 8.5 volts has dropped to 3.5 Volts at which time the sound has begun to become distorted, and I replaced it with another 9 V battery.
Each 9V battery is rated at around 400 mAh. The current draw on the amplifier is around 100 mA, so the time for running the amplifier is approximately 4 hours, but in reality was about 10 hours, and this was not continuous. One site lists the TEA Datasheet as specifying 3 -15 Volts, but 3 V is an absolute minimum and the volume cannot be increased without increasing the distortion unacceptably. I would thin 4.5 Volts is a good level.
It is possible to construct a home made battery made out of zinc, copper and salt water, with a voltage of 9 Volts. This will save between $19 and $ 70 per year, however it remains to be seen how long the existing AA size and 9V batteries last. So far they have lasted 4 days since November 17th. The 4 AA batteries, all new at 1.5V was connected yesterday (20th November 2020)
Source: Wikipedia List of Battery Sizes
Rechargeable Batteries
A set of AA rechargeable batteries cost a total of $14 for 4 batteries and the charger. The battery is cleared for 100 recharges at least which will work out to 11 x 100 = 1,100 days or 3 years. The cost per year will therefore be . The cost of the charger and batteries for a year will be then $ and without the charger will be $5, which is much less than the other types of batteries listed here. If you already have a charger it will be much much less. One manufacturer lists the capacity as 2000 mAh which is twice the expected value, which means an even greater value.
Battery Operated Amplifiers:
Battery Powered Power AMP "Rock Solid"
Product from Website
There is this: https://www.amazon.com/DIFIIFOL-Battery-Bluetooth-Amplifier-JT-30BBT/dp/B07DXP1ZVN
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