Has anyone come up with a clever battery recharging scheme for the gainclone? I noticed that Chris Brady (Teres turntable) uses a charging system on his battery module that senses current draw and engages charging when there is no circuit draw. (http://www.teresaudio.com/battery.html)
Can someone draw a schematic for a similar scheme applicable to the gainclone?
Also are there any further thoughts about speaker protection for a faulty gainclone power supply?
Regards
Mike
Can someone draw a schematic for a similar scheme applicable to the gainclone?
Also are there any further thoughts about speaker protection for a faulty gainclone power supply?
Regards
Mike
Konnichiwa,
Nope, but I did spend a lot of time designing a Charger circuit for my +/-36V Battery Supply I used on my Solid State (modified) Marantz Amp, El Muerto d'Agostino. There I ended up using small 2-Chamber constructuin, 12V AC transformers, rectidied with schottkies and regulated with an LM317 in "mixed mode", meaning set to a suitable end charge voltage (15V) and at the same current limited by a resistor between chip output and charger output to 0.5A for 6AH Batteries.
There was a pair of "flyback" diodes in series to each leg to the battery, in effect shutting down the circuit when not charging and I also used some cheap chokes, two per charger - 5H 200mA (wire rating 0.5A) - between the actual charger circuit and the battery charged (yes, one charger per battery).
I found that connecting/disconnecting this circuit or indeed connecting/disconnecting the mains to this circuit made no impact on the sound and thus the Amplifier could remain "always on" and thus thermally setteled and "warmed up", plus my batteries never run out of juice as they remained fully topped up.
Well, you'd need a sense resistor that senses current (or you could use a signal detector on the Amplifier output) and then triggers a relais actually supplied by the battery(s) and it would likely be a good idea to also incorporate a under voltage detecter that detects the batteries deep discharge and turns the relais off, thus reconnecting the battery stack to the charger and force charging the batteries.
You can find "switch on on signal" circuits all over the net in the context of subwoofer applications and battery monitor circuits that signal "deep discharge" too, just knit them together and you are set to go....
Sayonara
mgreene said:
Nope, but I did spend a lot of time designing a Charger circuit for my +/-36V Battery Supply I used on my Solid State (modified) Marantz Amp, El Muerto d'Agostino. There I ended up using small 2-Chamber constructuin, 12V AC transformers, rectidied with schottkies and regulated with an LM317 in "mixed mode", meaning set to a suitable end charge voltage (15V) and at the same current limited by a resistor between chip output and charger output to 0.5A for 6AH Batteries.
There was a pair of "flyback" diodes in series to each leg to the battery, in effect shutting down the circuit when not charging and I also used some cheap chokes, two per charger - 5H 200mA (wire rating 0.5A) - between the actual charger circuit and the battery charged (yes, one charger per battery).
I found that connecting/disconnecting this circuit or indeed connecting/disconnecting the mains to this circuit made no impact on the sound and thus the Amplifier could remain "always on" and thus thermally setteled and "warmed up", plus my batteries never run out of juice as they remained fully topped up.
mgreene said:
Well, you'd need a sense resistor that senses current (or you could use a signal detector on the Amplifier output) and then triggers a relais actually supplied by the battery(s) and it would likely be a good idea to also incorporate a under voltage detecter that detects the batteries deep discharge and turns the relais off, thus reconnecting the battery stack to the charger and force charging the batteries.
You can find "switch on on signal" circuits all over the net in the context of subwoofer applications and battery monitor circuits that signal "deep discharge" too, just knit them together and you are set to go....
Sayonara
As far as I understand it SLA batteries unlike some other types are very unfussy about charging.
In light of this I really don't understand why so many here are searching for a fancy recharging scheme.
when I was gaincloning with battery supplies I just used 75VA 9V + 9V transformer which rectified up to about 13V + 13V at the end of the charge. 100VA might might be better. I think about 13.7V is best
I left them on float when I was not listening and turned off the charging cct when I was ( hardly any difference in sound ! )
why would anyone want anything more complicated ?
I have I missed something ?
In light of this I really don't understand why so many here are searching for a fancy recharging scheme.
when I was gaincloning with battery supplies I just used 75VA 9V + 9V transformer which rectified up to about 13V + 13V at the end of the charge. 100VA might might be better. I think about 13.7V is best
I left them on float when I was not listening and turned off the charging cct when I was ( hardly any difference in sound ! )
why would anyone want anything more complicated ?
I have I missed something ?
Quote: "Have I missed something?"
Well, in my case, I have read many posts here and elsewhere that worried about various the failure modes of a gainclone PS where it could possibly take out the speakers. Now, I realize that some posts can lean towards hysteria but like they say "trust, but check first"
Also, there have been a few posts here that mention turning the charging supply on and off causing a thump through the speakers. For some drivers, i.e., ribbon tweeters, this presents a potential damage scenario.
Mikelm, you mention battery gaincloning like you have been there and done that - what are you listening to now? and what was your overall impression of the battery powered GC?
Mike
Well, in my case, I have read many posts here and elsewhere that worried about various the failure modes of a gainclone PS where it could possibly take out the speakers. Now, I realize that some posts can lean towards hysteria but like they say "trust, but check first"
Also, there have been a few posts here that mention turning the charging supply on and off causing a thump through the speakers. For some drivers, i.e., ribbon tweeters, this presents a potential damage scenario.
Mikelm, you mention battery gaincloning like you have been there and done that - what are you listening to now? and what was your overall impression of the battery powered GC?
Mike
Re: Quote: "Have I missed something?"
I have never heard the charger being switched ?
My implementaion of the gainclone was not, I think, good enough to give a fair impression - I will re-open the project later. I still think this avenue has something to offer
For now I am prefering my class A, bal wkg, choke regulated, SE amps - very loosely based on the JLH simple class A amplifier.
mgreene said:
I have never heard the charger being switched ?
My implementaion of the gainclone was not, I think, good enough to give a fair impression - I will re-open the project later. I still think this avenue has something to offer
For now I am prefering my class A, bal wkg, choke regulated, SE amps - very loosely based on the JLH simple class A amplifier.
Here's a couple of simple chargers...
I think the best approach that encompasses Kuei's suggestions is the Texas Instruments TI UC3906 IC. TI provides all the info you it is designed to build a complete charger by using only four external resistors(Rs, Ra, Rb, Rc).
"With the UC3906, this charge and hold cycle can be implemented with a minimum of external parts and design effort. A complete charger is shown in figure 4. Also shown are the design equations to be used to calculate the element values for a specific application. All of the programming of the voltage and current levels of the charger are determined by the appropriate selection the external resistors"
It has a ton of built-in features like Voltage and current sense comparators are used to sense the battery condition,. "The charge enable comparator on this IC can be used to remotely disable the charger. The comparator’s 25mA trickle bias output is active high when the driver is disabled. These features can be combined to implement a low current turn-on mode in a charger, preventing high current charging during abnormal conditions such as a shorted or reversed battery." It also has an overcharge protection feature.
"A very important feature of the UC3906 is its precision reference. The reference voltage is specially temperature compensated to track the temperature characteristics of lead-acid cells. In addition, the IC includes a supply under-voltage sensing circuit, used to initialize charging cycles at power on. This circuit also drives a logic output to indicate when input power is present."
Another fairly simple charger which features the AC disconnect while playing feature that Kuie mentioned is Elliot Sound's Automatic Charger for Battery Operated Preamps
This charger features two cheap relays that automatically disconnect the charger as soon as they sense a load on the battery, which is as soon as the the GC (in your case) starts to draw power.
"The idea is that the charger is left permanently connected, but of course that would normally introduce some hum into the supply lines. The sensor detects that you have switched on the preamp (or small power amp for that matter), and immediately switches off the charger, so while listening, there is no connection to the AC."
I think the best approach that encompasses Kuei's suggestions is the Texas Instruments TI UC3906 IC. TI provides all the info you it is designed to build a complete charger by using only four external resistors(Rs, Ra, Rb, Rc).
"With the UC3906, this charge and hold cycle can be implemented with a minimum of external parts and design effort. A complete charger is shown in figure 4. Also shown are the design equations to be used to calculate the element values for a specific application. All of the programming of the voltage and current levels of the charger are determined by the appropriate selection the external resistors"
An externally hosted image should be here but it was not working when we last tested it.
It has a ton of built-in features like Voltage and current sense comparators are used to sense the battery condition,. "The charge enable comparator on this IC can be used to remotely disable the charger. The comparator’s 25mA trickle bias output is active high when the driver is disabled. These features can be combined to implement a low current turn-on mode in a charger, preventing high current charging during abnormal conditions such as a shorted or reversed battery." It also has an overcharge protection feature.
"A very important feature of the UC3906 is its precision reference. The reference voltage is specially temperature compensated to track the temperature characteristics of lead-acid cells. In addition, the IC includes a supply under-voltage sensing circuit, used to initialize charging cycles at power on. This circuit also drives a logic output to indicate when input power is present."
Another fairly simple charger which features the AC disconnect while playing feature that Kuie mentioned is Elliot Sound's Automatic Charger for Battery Operated Preamps
This charger features two cheap relays that automatically disconnect the charger as soon as they sense a load on the battery, which is as soon as the the GC (in your case) starts to draw power.
"The idea is that the charger is left permanently connected, but of course that would normally introduce some hum into the supply lines. The sensor detects that you have switched on the preamp (or small power amp for that matter), and immediately switches off the charger, so while listening, there is no connection to the AC."
An externally hosted image should be here but it was not working when we last tested it.
I am in the process of designing a SLA battery charger based on the TI UC2906/UC3906 chip. It is really pretty much designed, but I still have to draw up the schematic.
This chip will control the charging modes, which can be bulk charging, overcharge and float (trickle).
From what I know about SLA's, you can use a simple constant voltage circuit, but it takes longer, and you do sacrifice battery life when you use this scheme.
A "smart" charger is pretty simple to make using this type of chip, and besides, where is the challenge is building a voltage regulator? And, you can sample the chips from TI.
Anyway, I have all the parts, and the project is on my list of things to do, probably a month or two away though.
In this interation, I was not planning to have a automatic sense. I will just unplug or turn it off when I am listening to music, and turn it back on when I am done.
Randy
This chip will control the charging modes, which can be bulk charging, overcharge and float (trickle).
From what I know about SLA's, you can use a simple constant voltage circuit, but it takes longer, and you do sacrifice battery life when you use this scheme.
A "smart" charger is pretty simple to make using this type of chip, and besides, where is the challenge is building a voltage regulator? And, you can sample the chips from TI.
Anyway, I have all the parts, and the project is on my list of things to do, probably a month or two away though.
In this interation, I was not planning to have a automatic sense. I will just unplug or turn it off when I am listening to music, and turn it back on when I am done.
Randy
Re: The Schematics Above
Konnichiwa,
I originally charged my whole 6pcs Battery Stack from one charger in series. My batteries where all from the batch but had seen around 2 Years prior service in a Standby UPS that also charged them in series. The result was very uneven charging and discharging, as batteries had obviusly aged differently.
So I would for best battery life recommend for SLA's to be charged either parallel (which neccesitates a major switching logic) or with a simple charger per battery. As said, a single LM317 in I/V limiting mode with flyback diodes will handle charging the battery fine and will allow switching simply the Mains supply to the individual transformers off for "pure battery power".
Adding the chokes allows permanent (on all the time) charging without audible downsides I could percieve compared to previous applications. The result becomes basically a "battery buffered" rather than battery supply.
Sayonara
Konnichiwa,
mgreene said:
I originally charged my whole 6pcs Battery Stack from one charger in series. My batteries where all from the batch but had seen around 2 Years prior service in a Standby UPS that also charged them in series. The result was very uneven charging and discharging, as batteries had obviusly aged differently.
So I would for best battery life recommend for SLA's to be charged either parallel (which neccesitates a major switching logic) or with a simple charger per battery. As said, a single LM317 in I/V limiting mode with flyback diodes will handle charging the battery fine and will allow switching simply the Mains supply to the individual transformers off for "pure battery power".
Adding the chokes allows permanent (on all the time) charging without audible downsides I could percieve compared to previous applications. The result becomes basically a "battery buffered" rather than battery supply.
Sayonara
After trying 4 batteries, + /- 24V shared between two channels I came to the conclusion that to avoid earthing / crosstalk compromises it is necessary to have 4 batteries per channel.
Hugh Dean made the point on another thread recently how important it is to have separate supplies for each channel.
I guess if the two channels and the batteries are all in one box it is marginally more acceptable to share supplies but if you want the best I think 8 batteries are needed
mike
p.s. using a transformer and diodes as a charger is not fixed voltage - it starts low and ends higher ! The current is high at first and then naturally drops down to a float type trickle at the end of the charge, so long as you choose the transformer with care.
P.P.S. DON'T FORGET THE FUSES !!!!!
Hugh Dean made the point on another thread recently how important it is to have separate supplies for each channel.
I guess if the two channels and the batteries are all in one box it is marginally more acceptable to share supplies but if you want the best I think 8 batteries are needed
mike
p.s. using a transformer and diodes as a charger is not fixed voltage - it starts low and ends higher ! The current is high at first and then naturally drops down to a float type trickle at the end of the charge, so long as you choose the transformer with care.
P.P.S. DON'T FORGET THE FUSES !!!!!
Mike, What would the specs be for a carefully chosen transformer? I was considering getting a custom wound transformer - 120VAC primaries, 1*34.5 volt AC secondaries, and about 1VA. I would use a single MU diode rectifier bridge. I would then trickle charge 4 12v 7A gel cell type batteries with 48 volts in series, at all times except when in use. (I would use two of these setups for isolated channels.) A single spst switch would turn off the charger when listening to music. Would gel cells be susceptable to uneven charging like Kuei Yang Wang mentions for SLA? I would only be able to listen 3 or 4 hours or so every other night max, so I would probably not need much current to maintain full charge. I would try to balance the mA to meet my needs. Are my assumptions correct? Will this work? In order to not over charge how many mA should I really end up with?
This link may provide some useful background.
http://www.batteryuniversity.com/partone-13.htm
I personally would use one 9V + 9V transformer for each series pair of 12V batteries. This means that the charger is still valid if one of the batteries is in a different condition. I used 75VA transformers.
By careful choice of transformer I meant that you need a combination of transformer regulation and diode forward voltage drop so that at the end of the charge the voltage across the battery is within the limits stated for SLA mentioned in the link.
I would aim for the voltage at end of charge to vary between 13.5V and 14.0V with the variation in the mains supply.
http://www.batteryuniversity.com/partone-13.htm
I personally would use one 9V + 9V transformer for each series pair of 12V batteries. This means that the charger is still valid if one of the batteries is in a different condition. I used 75VA transformers.
By careful choice of transformer I meant that you need a combination of transformer regulation and diode forward voltage drop so that at the end of the charge the voltage across the battery is within the limits stated for SLA mentioned in the link.
I would aim for the voltage at end of charge to vary between 13.5V and 14.0V with the variation in the mains supply.
I just ordered 4 Panasonic LC-R127R2P1 to use with my "Peter Daniel/BrianGT" GC. I am going for a simple charger; I realize there may be some shortening of battery life, but I'd rather replace the batteries than spend a bunch of time on a super fancy charger.
I'm planning on using a Stancor P-8551 24v 1a transformer to charge each series pair of batteries. I'll use a LM317 vr to drop the voltage down to about 28. A DPDT switch (or a relay) to go from charging to listening.
David
I'm planning on using a Stancor P-8551 24v 1a transformer to charge each series pair of batteries. I'll use a LM317 vr to drop the voltage down to about 28. A DPDT switch (or a relay) to go from charging to listening.
David
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.