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-   -   Definitive 24V Gainclone Battery Supply Recharging? (http://www.diyaudio.com/forums/chip-amps/25484-definitive-24v-gainclone-battery-supply-recharging.html)

mgreene 6th January 2004 02:25 PM

Definitive 24V Gainclone Battery Supply Recharging?
 
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

ThorstenL 6th January 2004 07:50 PM

Re: Definitive 24V Gainclone Battery Supply Recharging?
 
Konnichiwa,

Quote:

Originally posted by mgreene
Has anyone come up with a clever battery recharging scheme for the gainclone?
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.


Quote:

Originally posted by mgreene
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?

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 6th January 2004 08:27 PM

GC battery supply
 
Thanks Senior Wang,

Excellent suggestions - I was/am hoping that someone had reduced this one to practice already. I'm busy beavering away on my new super duper speakers :)

Mike

tiroth 6th January 2004 08:31 PM

Tried searching?

http://www.sound.westhost.com/project98.htm

mgreene 6th January 2004 08:41 PM

Thanks
 
Seems like I had seen that one some time ago but heard something like no one had actually built it - please correct me if I am wrong.

Mike

mikelm 6th January 2004 09:02 PM

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 ?

mgreene 7th January 2004 12:49 PM

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" :rolleyes:

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

mikelm 7th January 2004 04:38 PM

Re: Quote: "Have I missed something?"
 
Quote:

Originally posted by mgreene
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

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.

darkmoebius 7th January 2004 11:12 PM

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"

http://members.cox.net/darkmoebius/UC3906.gif

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 comparatorís 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."

http://sound.westhost.com/p98-f2.gif

randytsuch 8th January 2004 12:05 AM

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


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