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Old 3rd May 2011, 05:50 PM   #1611
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Quote:
Originally Posted by mootzeroni View Post
Ah, I read your post to say you were considering a dozen of those pre-packaged packs which in series would be over 120v with a tremendous discharge capability (yikes)! I've run a homemade boombox with a small LiPo pack, which has very impressive run time, but I would never-ever leave it unattended and the battery goes right back into the fireproof storage bag. Ceramic pan with lid or Pyrex glass would be even better. Lots of stories in the r/c hobby about garages being burned down and autos destroyed from overcharging LiPo batteries or accidental shorts. Spectacular flames (as you can see in the video). LiFe are indeed safer, but still a short can cause a fire. Just be very very careful.

Lastly, neither of those types of batteries can handle complete discharge... they die if discharged all the way. It's easy to see when running an electric motor, but unless you have a good metering system, with audio you won't know until it's too late.
You're confusing the types of battery!
LiPo and LiFe are NOT the same as LiFePo4

1) LiFePo4 is SAFE

2) LiFePo4 can be totally discharged, repeatedly, without significant weakening or alteration of its operating characteristics. You can run it all the way down as many times as you like, no problem.

3) LiFePo4 has a much longer life cycle, can be charged and discharged many thousands of times.

AND... of course...

LiFePo4 costs more.... MUCH more.... sigh...

Last edited by Jack Caldwell; 3rd May 2011 at 05:56 PM.
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Old 3rd May 2011, 05:51 PM   #1612
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Quote:
Originally Posted by Jack Caldwell View Post
Hi, just a quick note about using LiFePo4 batteries with the 2050 type amps. They can work very well.

1) Some of these sound incredibly good, like the RedWine Audio Black Lightning LFP supplies. I have one of these and the difference between these and any SLA or any of the smps I've heard to date is stunning.

2) Note that LiFePo4 is NOT Lithium Ion and it is NOT explosive, do not confuse the two.

3) The one spec that is missing from a lot of LiFePo4 vendors is the internal or source resistance. The best I have seen on a 3.3V LiFePo4 cell is under 30 mili-Ohms, so when you get 8 of those in series for a 25.6V battery, the total DC source resistance is around 0.024 ohms or lower, which is very good indeed.

4) And while I have not yet seen any published graphs of source impedance vs frequency for LiFePo4 batteries, but Vinnie at RedWine told me that there are significant variations between batteries. The cells he gets as custom items are extremely low impedance at HF, much lower than SLA batteries and/or most linear or switching supplies. This is probably the key reason for his supplies sounding so much better. And, no, he isn't about to tell us which vendor he gets them from... curses! foiled again!

Just the same, it is probably a useful endeavor for the diy community to explore this topic in depth. Maybe we should start a battery-powered thread for Tripaths, if it doesn't already exist...

So, in my experience with LiFePo4, about the only thing that explodes is the dynamics of your sound system.
I'd bet he is using A123 cells. They have 10 mili-Ohm internal resistance.
Have a look at the datasheet:
http://file.espritmodel.com/document...0-RCDevKit.pdf
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Old 3rd May 2011, 06:26 PM   #1613
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Quote:
Originally Posted by mootzeroni View Post
Here's a LiFe short fire for instance: YouTube - Test LiFePo4


WOW, that video shows actually how SAFE it is. Nothing happens even to that huge battery pack, only to the cable! Thanks for the video!
from the Youtube author's comment:

Quote:
This "test" was made to show what happens in case of short circuit. This is a brutal test, considering that normal LiPo could explodes or fires. This cell is LiFePo4 instead. The LiFePo4 cells never explode or fire in no case and can be overcharged.
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Old 3rd May 2011, 06:39 PM   #1614
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Question who makes the A123?

Quote:
Originally Posted by erozsolt View Post
I'd bet he is using A123 cells. They have 10 mili-Ohm internal resistance.
Have a look at the datasheet:
http://file.espritmodel.com/document...0-RCDevKit.pdf
Now THAT looks like a good battery! Under 10 mili-Ohms for DC internal resistance and 8mili-Ohms AC source impedance at 1KHz!

There may be other limiting factors, but it looks like the max instantaneous current would be 3.3V divided by 8 mili-Ohm = over 400 Amps !!

Better make SURE you never get a short across these puppies! A small gauge wire could vaporize!

So let's see...
8 x 3.3V = 26.4V w. 0.064 ohms 1KHz source Z (impedance).. great for the 2050

12 x 3.3V = 39.6V w. 0.096 Ohms 1KHz source Z... STA510a anyone?

18 X 3.3V = 59.4V w. 0.144 ohms 1KHz source Z for the STA517B type of output

Any idea of who the mfg is? It looks like A123 is a model Racing Car vendor?

RedWine's units incorporate a special low-noise charger that allows charge-on-demand, even while listening. It can be switched out completely so it is not in the circuit during listening, but I haven't heard much difference. That part might be a little harder to replicate...
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Old 3rd May 2011, 07:00 PM   #1615
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Quote:
Originally Posted by Jack Caldwell View Post
Now THAT looks like a good battery! Under 10 mili-Ohms for DC internal resistance and 8mili-Ohms AC source impedance at 1KHz!

There may be other limiting factors, but it looks like the max instantaneous current would be 3.3V divided by 8 mili-Ohm = over 400 Amps !!

Better make SURE you never get a short across these puppies! A small gauge wire could vaporize!

So let's see...
8 x 3.3V = 26.4V w. 0.064 ohms 1KHz source Z (impedance).. great for the 2050

12 x 3.3V = 39.6V w. 0.096 Ohms 1KHz source Z... STA510a anyone?

18 X 3.3V = 59.4V w. 0.144 ohms 1KHz source Z for the STA517B type of output

Any idea of who the mfg is? It looks like A123 is a model Racing Car vendor?

RedWine's units incorporate a special low-noise charger that allows charge-on-demand, even while listening. It can be switched out completely so it is not in the circuit during listening, but I haven't heard much difference. That part might be a little harder to replicate...
As far as I've read about it:

1. A123 Systems is the No. 1 brand who perfected and makes the best LiFePo4 cells. They produce the cells used in electric cars and buses and in a lot of government / defense scenarios.
http://www.a123systems.com/

2. There are a few companies which make packs made from A123 cells. The A123Racing is the name of a pack which is made by one of their subsidiaries.

3. The RC community loves these cells, as they are not burning down their "birds", like LiPo. The RC forums are full of many hundred page long threads about the A123 cells. Here is a vendor they recommend:
A123 Batteries : EP Buddy, Better Services for iCharger

4. A123 cells need special chargers!

5. Some links:
A123 Rx Pack Setup Guide
The A123 FAQ for Giant Scale and IMAC
A123 Batteries for Dummies. - FlyingGiants
RC Groups - View Single Post - A123 cell questions

Last edited by erozsolt; 3rd May 2011 at 07:06 PM.
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Old 3rd May 2011, 07:43 PM   #1616
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Talking How about this DeWalt pack?

Quote:
Originally Posted by erozsolt View Post
As far as I've read about it:

1. A123 Systems is the No. 1 brand who perfected and makes the best LiFePo4 cells. They produce the cells used in electric cars and buses and in a lot of government / defense scenarios.
A123 Systems


3. The RC community loves these cells, as they are not burning down their "birds", like LiPo. The RC forums are full of many hundred page long threads about the A123 cells. Here is a vendor they recommend:
A123 Batteries : EP Buddy, Better Services for iCharger

4. A123 cells need special chargers!

5. Some links:
A123 Rx Pack Setup Guide
The A123 FAQ for Giant Scale and IMAC
A123 Batteries for Dummies. - FlyingGiants
RC Groups - View Single Post - A123 cell questions
Thanks for the info!
The ep buddy stuff looks interesting, but only seems to go up to 19.8V (??)

BUT... in looking at the YouTube video showing the LiFePo4 batt-pack stay intact while it was melting down the heavy duty battery cable (!!!), one of the following videos had an electric motorcycle guy who was cannibalizing the a123 cells from deWalt 36V batt-packs... so then I found this:

Amazon.com: DEWALT DC9360 36-Volt Lithium-Ion Battery Pack: Home Improvement

I wouldn't have thought this is a LiFePo4 as DeWalt calls it Li-Ion and A123 calls it a NanoPhosphate Li-Ion... but if it's the same thing as LiFePo4, this could be a great and obviously very safe option for those who need a good 36V supply... and the charger is only $40...
Amazon.com: DEWALT DC9000 36-Volt Lithium-Ion 1 Hour Charger: Home Improvement

For a total of $190USD you're looking at a rather formidable PS for your 510a based boards, I think it can even be used for the 517B if you don't have the need for the full 60V for 300W and can get by with 36V supply and 150W output...!!

Think about it... if you don't mind borrowing the supply from your audio system, you can use it to power your hand-tools!!

And, last but not least, if you use the deWalt supply in stock form, we're covered by their warranty... to some of us who are building commercial products like my speakers at HolisticAudio.com, this last part can be hugely valuable: CE and RoHs certified supplies, warranty and product liability issues... many paperwork problems simply disappear by using an established, well-respected vendor's battery supply.

Now we gotta find or make a nice case to fit the batt-pack and charger!
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Old 3rd May 2011, 07:53 PM   #1617
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Default Warning: UNhappy deWalt users

Quote:
Originally Posted by Jack Caldwell View Post
... but if it's the same thing as LiFePo4, this could be a great and obviously very safe option for those who need a good 36V supply... and the charger is only $40...

For a total of $190USD you're looking at a rather formidable PS for your 510a based boards, I think it can even be used for the 517B if you don't have the need for the full 60V for 300W and can get by with 36V supply and 150W output...!!
Hmm...about that deWalt 36V battery

Amazon has a bunch of unhappy user testimonials on these batteries... looks like part of it is if you buy a battery product at Amazon it is NOT RETURNABLE and Amazon will not support you, nor will deWalt!

If you get one of these, looks like Ho' Depot or Low's are better options.
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Old 3rd May 2011, 08:50 PM   #1618
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Check BatterySpace.com

Of the LiFePO₄ stuff they carry, the ~3300 mAh cells were been the best buy last I looked. They have lower max. current output than A123 cells, but they're still pretty great!

Here's some info I collected on the 41Hz.com forum: LiFePO₄ batteries - 41Hz.com Forums

Last edited by kristleifur; 3rd May 2011 at 08:53 PM.
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Old 3rd May 2011, 11:42 PM   #1619
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I contacted batteryspace.com a few days ago and they said they can no longer ship these batteries abroad because of some export regulation issues... :S
If someone finds a workaround, please let us know.
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Old 4th May 2011, 12:13 AM   #1620
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Quote:
Originally Posted by erozsolt View Post
I hope Cristi clears up that part, because on the website, the other PSU-s have a swich where you can select which version would you like. If I choose the T1 510, I'd really like to have 36V. A 24V + 10% could only do 26.4V. If 36V is not possible on a SMPS300R then I'd go with a better Meanwell.
"Can be configured for for either dual output voltage, or single output voltage, in range of +-30V to +-72V or 24V to 72V. The stock available output voltages are adjustable within +-10% range."

If you want 36v you just order 30v single ended and then have 10% adjustment.
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