- #1
nareto
- 7
- 0
Hello, I have a small (24 Watt) guitar amp which I'd like to retrofit with a
battery for outdoor playing. I actually study mathematics and do electronics
mostly as an hobby, so I may miss some fundamental things (i.e. bare with me). Basically, I have two little problems which I'd like help with:
1) Is the following reasoning correct and appropriate?
I need to calculate the current the amplifier absorbs in order to choose a
battery capable of providing the same current. So, given the power consumption
is 24 watts at 220 V RMS (I'm in Italy), the current is 109 mA RMS. But since
I'd attach the battery after the rectifier that's inside the amp, I actually need peak to peak
amperes, so I'd need 154 mA from the battery. So, given I'd like the battery to last at least 1
hour, I'd need one with "C" greater than 1 and 154mah (for one hour),
154*2=308mah (for two hours) and so on.
2) if I know little about electronics, I know next to nothing about battery types
(lithium, lithium-polymer, nimh and so on). What would be a reccomended choice
for my project?
Ideally I'd like it to be cheap (the DC after the rectifier is
35V, so probably I'll need many of them), have many charge/discharge
cycles, have a simple (if any) recharging circuit, which I could power from
the 35V provided by the rectified "wall" power supply (I'd add a rotary switch so the amp
would either be off, running on battery, running on 220 or charging the battery
from the 220)
There's actually another little problem, that the rectifier provides a dual
supply (+-17V) to the amp circuit, but I allready found that I could achieve
that (with the battery) with a simple op-amp circuit (found here, for future
reference: http://tangentsoft.net/elec/vgrounds.html )
any help is very much appreciated
cheers
battery for outdoor playing. I actually study mathematics and do electronics
mostly as an hobby, so I may miss some fundamental things (i.e. bare with me). Basically, I have two little problems which I'd like help with:
1) Is the following reasoning correct and appropriate?
I need to calculate the current the amplifier absorbs in order to choose a
battery capable of providing the same current. So, given the power consumption
is 24 watts at 220 V RMS (I'm in Italy), the current is 109 mA RMS. But since
I'd attach the battery after the rectifier that's inside the amp, I actually need peak to peak
amperes, so I'd need 154 mA from the battery. So, given I'd like the battery to last at least 1
hour, I'd need one with "C" greater than 1 and 154mah (for one hour),
154*2=308mah (for two hours) and so on.
2) if I know little about electronics, I know next to nothing about battery types
(lithium, lithium-polymer, nimh and so on). What would be a reccomended choice
for my project?
Ideally I'd like it to be cheap (the DC after the rectifier is
35V, so probably I'll need many of them), have many charge/discharge
cycles, have a simple (if any) recharging circuit, which I could power from
the 35V provided by the rectified "wall" power supply (I'd add a rotary switch so the amp
would either be off, running on battery, running on 220 or charging the battery
from the 220)
There's actually another little problem, that the rectifier provides a dual
supply (+-17V) to the amp circuit, but I allready found that I could achieve
that (with the battery) with a simple op-amp circuit (found here, for future
reference: http://tangentsoft.net/elec/vgrounds.html )
any help is very much appreciated
cheers