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Old 4th May 2011, 10:44 PM   #1641
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Quote:
Originally Posted by sendler View Post
A soft start will be mandatory for any type of fast battery supply to save the power switch from an early demise.
I've heard that too, but I don't understand why? Can you explain a bit on the subject? I've heard that big solid state monoblocks could have an effect at startup which needs to be controlled by a soft-start, but I don't understand why would that be needed on a very efficient Tripath based solution? Do you think these amps have dangerous loads at startup?

And it was mentioned that many guys have killed their T-Amps by running them from car batteries. But why? That amp requires so little power!

AND: what if we just put a fuse between the battery and the amp? Can a fuse in the power input modify the sound? The mentioned commercial product uses a fuse too. Doesn't it have any side effect?
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Old 4th May 2011, 11:47 PM   #1642
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Location: Fairfield, IA
Question Any experience with T3 soft-start?

Quote:
Originally Posted by sendler View Post
A soft start will be mandatory for any type of fast battery supply to save the power switch from an early demise.
.
.
Hi Scott, have you looked at the T3a board that comes with the hifimediy T3? Sounds like it could help solve this issue. As it stands, a high current smps can also fry the switch if it's not big enough...

How about the amp boards themselves? Anything to fear there? It's always easy enough to get a BIG on/off switch... and will we get a nasty 200 W pop from just using a single switch?

I have not experimented with these options on my boards... call me chicken if you must.
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Old 5th May 2011, 02:56 AM   #1643
sendler is offline sendler  United States
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Location: ny
Default spark

i'm just judging by the size of the the spark that is thrown when I slam the last terminal down on the battery post. With 2 car batteries in series, 25v, the spark is humongous. I played with 3 batteries briefly even though it is slightly over the safe design spec of my amp at 38v and the spark is down right dangerous. And this was with the stock tank caps of 3600uf before adding an additional 10,000 that I use now. The surface mount caps on the Sure amps are very fast to start, as are the amp's circuit. This giant spark will burn a switch.
Quote:
Originally Posted by erozsolt View Post
I've heard that too, but I don't understand why? Can you explain a bit on the subject? I've heard that big solid state monoblocks could have an effect at startup which needs to be controlled by a soft-start, but I don't understand why would that be needed on a very efficient Tripath based solution? Do you think these amps have dangerous loads at startup?

And it was mentioned that many guys have killed their T-Amps by running them from car batteries. But why? That amp requires so little power!

AND: what if we just put a fuse between the battery and the amp? Can a fuse in the power input modify the sound? The mentioned commercial product uses a fuse too. Doesn't it have any side effect?
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Old 5th May 2011, 03:03 AM   #1644
sendler is offline sendler  United States
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Location: ny
Default soft start

Of the Hifime amps, I would be most interested in the mono T3.
.
SMPS are current protected so they always start just as they want to.
.
It might be possible to build a simple manual soft start for use with batteries using the first switch with a series resistor and a second switch wired straight through if you didn't want to mess with a timed relay.
.
.
Quote:
Originally Posted by Jack Caldwell View Post
Hi Scott, have you looked at the T3a board that comes with the hifimediy T3? Sounds like it could help solve this issue. As it stands, a high current smps can also fry the switch if it's not big enough...

How about the amp boards themselves? Anything to fear there? It's always easy enough to get a BIG on/off switch... and will we get a nasty 200 W pop from just using a single switch?

I have not experimented with these options on my boards... call me chicken if you must.
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Old 5th May 2011, 03:23 AM   #1645
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Join Date: Jul 2005
Location: Fairfield, IA
Talking Spark? Dangerous?

Quote:
Originally Posted by sendler View Post
i'm just judging by the size of the the spark that is thrown when I slam the last terminal down on the battery post. With 2 car batteries in series, 25v, the spark is humongous. I played with 3 batteries briefly even though it is slightly over the safe design spec of my amp at 38v and the spark is down right dangerous. And this was with the stock tank caps of 3600uf before adding an additional 10,000 that I use now. The surface mount caps on the Sure amps are very fast to start, as are the amp's circuit. This giant spark will burn a switch.
Dangerous? Well, maybe if you have an open canister of gas in your audio room... that's one way of getting some BOOM in the bass registers

I once lost about a 1/4" chunk from the tip of my screwdriver with an automotive battery... made me reluctant to try it that way on amp... i think i'll do a 3 step manual soft-start thing with these a123 batt-packs

Last edited by Jack Caldwell; 5th May 2011 at 03:28 AM.
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Old 5th May 2011, 08:09 AM   #1646
vlaca is offline vlaca  Hungary
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Quote:
Originally Posted by erozsolt View Post
I've heard that too, but I don't understand why? Can you explain a bit on the subject? I've heard that big solid state monoblocks could have an effect at startup which needs to be controlled by a soft-start, but I don't understand why would that be needed on a very efficient Tripath based solution? Do you think these amps have dangerous loads at startup?

And it was mentioned that many guys have killed their T-Amps by running them from car batteries. But why? That amp requires so little power!

AND: what if we just put a fuse between the battery and the amp? Can a fuse in the power input modify the sound? The mentioned commercial product uses a fuse too. Doesn't it have any side effect?
Hi!

I sent you message. (PM)
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Old 5th May 2011, 05:33 PM   #1647
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Talking A123 cells for T2-TK2050?

Quote:
Originally Posted by erozsolt View Post
Here is what I'd do:
1. Buy 10-11 individual cells from someone who can spot weld tabs on the batteries. There are eBay sellers who do it for free. Maybe ep buddy would do that too.
2. Attach a wire to both solder plates for each battery. I'd end up with about 20-22 wires.
3. Make a wooden box for them. After this point, I can connect them in series if I want, or measure them individually, or charge them individually. Or replace one, which is found faulty.
4. This way I'd have a box, with all the different wires in series giving me an n * 3.3 V source. I mean this way I could use the same battery pack to give 15V to my DAC, 36V to a T1, etc.
I like your idea of "parallel pirating" some of the voltage to power the DAC. etc. Battery supply is REALLY great for DACs!

In looking closely at the a123 I realized that although the source impedance is very low, the capacity is only 2.3Ah (2300mAh). This would give a fairly short run-time, probably only 2 hours or so with the TK2050.

The RedWine pack is a 25.6V/10Ah and powers my Virtues for about 10 to 12 hours continuous play at moderate volumes. So it's probable we would want at least 7Ah for the T2 w TK2050 and 10Ah for the T3

For the T2, this now takes the number of a123 cells to about x24: 3 paralleled sets of 8 series cells = 24 cells for a +26.4V supply.

That gets expensive... but it also reduces the source impedance even more, now the DC source impedance becomes less than 80 mili-ohms per leg, for a total source impedance of under 27 mili-ohms... and the AC source impedance, at less than 64 mili-ohms per leg, will end up under 21 miliohms... that's close to 0.02 Ohms which is phenomenal... in theory peak instantaneous current would be near 1300 Amperes! Now THAT should handle any sudden amplifier demands!

For the T3 which uses the STA517B in parallel, the operating voltage is between +30V to +60V... To get about 200W output into 4 ohms, the supply needs to be at about +36V, maybe +40V

And we'd need at least 10Ah, so given the available battery management systems and chargers, it might make more sense to drive the T3 with 4 sets of 12 cells in series, and then the drive voltage gets up to be about +40V/9.2AH and under 0.025 ohm source impedance.

If we use flatpack cells at 10Ah like RWA does, it's probably something like 8 of these:
High Power LFP Polymer Cell: 3.2V 10Ah (8790160-5C) 32Wh, 50A rate UN Approved (DGR)

At $50+ per cell, that gets expensive fast! Use 8 of them, then add to that the battery management module and the charger and a case + connectors + shipping cartons and it's easy to see why the RWA sells for $800
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Old 6th May 2011, 01:19 AM   #1648
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Quote:
Originally Posted by Jack Caldwell View Post
...
About battery capacity: its so easy when you think in Wh units.

The one pack version of the RedWine is 12.8 V * 10 Ah = 128 Wh
The two pack version of the RedWine is double that = 256 Wh.

The price difference between them is 300 USD, which means the RedWine batteries cost about 2.34 USD / Wh.

The prismatic (flat) cell you linked is 32 Wh and 56 USD, which means its 1.75 USD / Wh.

100 batch of 2300 mA A123 cells from here is 780 USD and its 3.3 V * 2.3Ah * 100 = 759 Wh, which means 1.02 USD / Wh.

A123 has a new prismatic cell too, its called: AMP20. Its 20 Ah * 3.3V = 66 Wh. Here is a detailed specification which says that they are actually 64.6 Wh. Look: two of these modules are exactly one RedWine module (128 Wh). And these modules just started to be available for the public (they are made for the electric vehicle market!). I'm 99% sure that RedWine uses something like two of these packs exactly, but rewires (is it possible with prismatic cells?) them them to set the voltage required.

Oh, you will like it:
Quote:
Internal resistance: 2 mOhm nom
Weight (g) 496
And its not even expensive: for example here its 60 USD, which means its 0.9 USD / Wh! Thats quite good for an A123 cell!

Here is a big thread praising them and about how hard it is to aquire a first class one.
Endless-sphere.com • View topic - A123 20AH cells source?

Last edited by erozsolt; 6th May 2011 at 01:24 AM.
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Old 6th May 2011, 01:31 AM   #1649
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The nice thing about batteryspace.com packs is that they come with a nice protection PCB. For the same price, give or take, EPBuddy offers genuine A123 ones (so better batteries) but no protection circuit. Not sure which would be the best buy.
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Old 6th May 2011, 09:02 AM   #1650
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Quote:
Originally Posted by TheShaman View Post
The nice thing about batteryspace.com packs is that they come with a nice protection PCB. For the same price, give or take, EPBuddy offers genuine A123 ones (so better batteries) but no protection circuit. Not sure which would be the best buy.
Going without a protection circuit isn't worth it. However, I'm confident that there are external protection circuits that work with A123 packs, or chargers that attach to a balancing harness.

The main point with the protection circuit is the charge-balancing: It bleeds power off of cells that have higher charge than the other ones in the battery, so that the charger doesn't leave one of them stranded in undervoltage land. Breaks the cell, breaks the pack.
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