May be but I have never heard of it and have no idea of what the circuit is. I suspect neither has anybody else here or they would have answered your question by now. If you want help, you have to provide some detials or it is like asking "how long is a piece of string?"
And relying on the state of charge of batteries to get the 'correct' voltage is not the answer to put it politely!
Hi,
I'm making a dual mono +/-24V battery power supply for a DACT CT100 Phono preamp. I'm using 8X 12V 2.2Ah Panasonic SLA batteries and 4400uF,35v Elna low ESR caps (paralled 2200uF).
I wanted the charging circuit to be as simple as possible, although it would not be as convenient as the automatic ones (might be a future project).
I've accached a rough schematic of one channel's supply.
The DACT only draws 22mA per channel, so I would need to recharge no more than once every two weeks.
The setup means only one of the four batteries per channel can be charged at a time, thoiugh each battery would recharge within 1/2 hour with a 1A SLA charger.
To shorten the charging time I would use a second charger simultaneously on the other channel.
Can you see any problems with this arrangement, other than a little inconvenience.
Audie.
I'm making a dual mono +/-24V battery power supply for a DACT CT100 Phono preamp. I'm using 8X 12V 2.2Ah Panasonic SLA batteries and 4400uF,35v Elna low ESR caps (paralled 2200uF).
I wanted the charging circuit to be as simple as possible, although it would not be as convenient as the automatic ones (might be a future project).
I've accached a rough schematic of one channel's supply.
The DACT only draws 22mA per channel, so I would need to recharge no more than once every two weeks.
The setup means only one of the four batteries per channel can be charged at a time, thoiugh each battery would recharge within 1/2 hour with a 1A SLA charger.
To shorten the charging time I would use a second charger simultaneously on the other channel.
Can you see any problems with this arrangement, other than a little inconvenience.
Audie.
Attachments
I should mention that I would recharge the batteries at around 80% capacity or less, but no less than every two weeks, which would allow about 1 1/2 hours play per day.
I'll probably get two fully automatic 1A SLA charges, although I could just use the Arlec 6A Automatic 12V charger I use for my car battery. I have also used this charger to charge the same 1.3Ah Panasonic SLA battery for over seven years, and I used it again tonight for lighting, when we had a power failure.
Audie.
I'll probably get two fully automatic 1A SLA charges, although I could just use the Arlec 6A Automatic 12V charger I use for my car battery. I have also used this charger to charge the same 1.3Ah Panasonic SLA battery for over seven years, and I used it again tonight for lighting, when we had a power failure.
Audie.
Charger for +/- 24
Could you not use a 48v charger on a switch with a floating ground?
ie. the amp is grounded in the center of the pack +/- 24v then you throw the double pole switch and the charger sees 48v and charges the batteries?
maybe you could use a ti microprocessor to PWM each battery regardless of the input charger voltage and each battery would be optimally charged.
PS: I have done a lot of testing and and batteries seem to beat AC power even with all the caps,snubbers,balanced power etc... However
the sound goes through the power supply I would be interested in impedance of the sealed batteries in the audio range.
Could you not use a 48v charger on a switch with a floating ground?
ie. the amp is grounded in the center of the pack +/- 24v then you throw the double pole switch and the charger sees 48v and charges the batteries?
maybe you could use a ti microprocessor to PWM each battery regardless of the input charger voltage and each battery would be optimally charged.
PS: I have done a lot of testing and and batteries seem to beat AC power even with all the caps,snubbers,balanced power etc... However
the sound goes through the power supply I would be interested in impedance of the sealed batteries in the audio range.
WRT to the Graham Slee phono...
Are you measuring the wall wart supply or the upgrade supply? I would be quite sure the wall art is not regulated and thus under no load conditions would give a higher reading then the voltage would be under load.
There will be regulation inside the Slee. So, I would hook up a "test crib" of 24V battery power as per the specification of the PSU and it will either work and light up the LED or not if it is too low.
Do not go too high on volatage in to the Slee as perhaps the regulators are not designed (heatsink wise) to dump the xtra voltage....
Are you measuring the wall wart supply or the upgrade supply? I would be quite sure the wall art is not regulated and thus under no load conditions would give a higher reading then the voltage would be under load.
There will be regulation inside the Slee. So, I would hook up a "test crib" of 24V battery power as per the specification of the PSU and it will either work and light up the LED or not if it is too low.
Do not go too high on volatage in to the Slee as perhaps the regulators are not designed (heatsink wise) to dump the xtra voltage....
Anyone know what a battery's impedance looks like at higher frequencies, around 20khz, 100khz? In particular NiCD or NiMH cells.
The closest info I could find was this: http://tf.nist.gov/general/pdf/1133.pdf. You can find a graph of noise up to about 100khz (figure 3). And since they say noise is predominantly due to Johnson noise, can we infer that impedance remains reasonably constant up to 50khz or so? Or will the battery become inductive (i.e., no Johnson noise, but impedance rises anyway)?
The closest info I could find was this: http://tf.nist.gov/general/pdf/1133.pdf. You can find a graph of noise up to about 100khz (figure 3). And since they say noise is predominantly due to Johnson noise, can we infer that impedance remains reasonably constant up to 50khz or so? Or will the battery become inductive (i.e., no Johnson noise, but impedance rises anyway)?
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My guess would be about 1000% but that's just a guess
I'm sure whatever it is it would benefit from a bypass of 1uF + 0.2 ohms
Even with a 47u+15u decoupling network the impedance is 0.3R@10khz and 3R@5Khz. I can't add a larger cap since I'm using all film caps. So I need to know if the battery is still going to be close to 25milliR at ~20Khz. Or cross my fingers and hope that PSRR saves the day?
It'd be even nicer to get rid of the 47uF altogether, but I have no idea how the battery performs at 100Khz. I must've gone through 500 papers on battery impedance, all of them dealing in milliHertz and state of charge. Couldn't find a single one showing impedance of a cell higher than 1khz :/
It'd be even nicer to get rid of the 47uF altogether, but I have no idea how the battery performs at 100Khz. I must've gone through 500 papers on battery impedance, all of them dealing in milliHertz and state of charge. Couldn't find a single one showing impedance of a cell higher than 1khz :/
I wouldnt.
A capacitor has a MUCH higher capability to supply surge current, and to take in charge current. A decent electrolytic cap can easily supply a surge current instantly in the range of 50 amps or more, and that is conservative. For example, a flash capacitor will smack out over 100 amps in microseconds. You wont get a nicad do that, especially a whole lot of them in series which you will need to match the voltage.
Thats why remote control cars have moved to lithium polymer cells, they are much more capable of providing high current bursts, but they to have their issues, specifically cell balance and overcharge/undercharge. If you do either to a lipo cell you risk damaging the cell, or even explosion.
You will also need to heavily regulate the power supply as well, otherwise you will get dendrite formation in your nicads.
As well, you will need to actually have your power supply change its voltage output depending on cell temperature, as their voltage changes with temperature.
Put it this way. I ended up buying a 180 dollar charger just to efficiently and safely discharge and charge nicad and lipo batteries for my remote control cars.
There is no way to replace a good solid well made electrolytic capacitor with respect to surge current capability, and resistance to.. ya know.. exploding when used in a standard PSU circuit.
A capacitor has a MUCH higher capability to supply surge current, and to take in charge current. A decent electrolytic cap can easily supply a surge current instantly in the range of 50 amps or more, and that is conservative. For example, a flash capacitor will smack out over 100 amps in microseconds. You wont get a nicad do that, especially a whole lot of them in series which you will need to match the voltage.
Thats why remote control cars have moved to lithium polymer cells, they are much more capable of providing high current bursts, but they to have their issues, specifically cell balance and overcharge/undercharge. If you do either to a lipo cell you risk damaging the cell, or even explosion.
You will also need to heavily regulate the power supply as well, otherwise you will get dendrite formation in your nicads.
As well, you will need to actually have your power supply change its voltage output depending on cell temperature, as their voltage changes with temperature.
Put it this way. I ended up buying a 180 dollar charger just to efficiently and safely discharge and charge nicad and lipo batteries for my remote control cars.
There is no way to replace a good solid well made electrolytic capacitor with respect to surge current capability, and resistance to.. ya know.. exploding when used in a standard PSU circuit.
These cells will be used in a supply that draws only 10mA (DAC analogue supply). Rise time is 200ns, and the smaller bypass caps handle everything above 500khz. The first question I think has been answered, i.e., the battery would maintain its impedance within the audio range.
Now the question is just how quick can the battery respond well into the tens or hundreds of Khz range. If it can, there's no need for large reservoir caps.
Now the question is just how quick can the battery respond well into the tens or hundreds of Khz range. If it can, there's no need for large reservoir caps.
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