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Old Jun 09, 2006, 02:37 PM
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CBA 10X Current Amplifier - Prototype, from West Mountain Radio

This amplifier is a welcome extension of the CBA's usefulness as higher-powered LiPos come to market. It's very straightforward to use - simply connects in series between the battery and the CBA. The production unit will have a cover.

The software has not been patched for the amplifier yet, so the current settings, which are by means of the CBA's usual software, have to be set @ 1/10 the actual amperage and the corresponding mAh readings are one decimal place low.

Until the software is patched, Overlays of the graphs generated on the CBA alone cannot be overlaid on graphs made with the amplifier - the graphs are also off by a factor of 10, of course. See the graph.

I'll graph the Enerland 3300 20C shown, out to 20C (66A), and publish it in a separate thread shortly. (Edit, 6/12:
http://www.rcgroups.com/forums/showthread.php?t=529118 ).

- RD
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Old Jun 10, 2006, 01:39 AM
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Nice up-grade!

What is the new max amp/power level with this addon?

Larry
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Old Jun 11, 2006, 06:49 AM
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Larry,

I'm not sure. I'll ask Del Monday.

- RD
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Old Jun 11, 2006, 12:26 PM
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Bellingham WA
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Hello RD,

Nice. I see them on the web site, but there is no mention of price. Any idea?

Are you happy with its performance?

Tom
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Old Jun 11, 2006, 07:14 PM
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Thats great, a much welcomed item.
2 weeks ago a factory sent me 2200mAh '30C' cells after i asked for something lower than 800mAh to test. I believe they are aware that a CBA cannot test the larger cells.
I hope this items hits the market soon.
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Old Jun 11, 2006, 07:45 PM
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Hi Tom,

It seems to work well:
http://www.rcgroups.com/forums/showthread.php?t=529118

Rather than guestimate the production model's price, I'll ask Del Monday.

World Hobby,

It's my understanding that the first batch of production models will be avaiable quite soon. The folks at West Mountain Radio could tell you.

- RD
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Old Jun 12, 2006, 06:47 AM
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RD,

For graph overlays, you could export the data into excel, multiply the numbers out and then graph. I have used this method in the past and works pretty good.

2dogrc
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Old Jun 12, 2006, 08:26 AM
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Thanks, 2dog.

I'm afraid I'm a klutz with Excel - was never able to use it successfully with my CamLight discharger.

- RD
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Old Jun 12, 2006, 10:14 AM
Del Schier
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The CBA Amplifier is on our web page:

http://www.westmountainradio.com/CBAAmplifier.htm

Dave has a prototype but we are shipping the first production uints now. We have a long first come first serve list so we do not want to put them on the web page. The page processes charge cards before we ship.

If you would like to be on the list, email me. We contact you when one is ready according to the list.

Thank you,

Del Schier

West Mountain Radio
18 Sheehan Ave.
Norwalk, CT 06854
http://www.westmountainradio.com
tel: 203 853 8080
fax: 203 299 0232


Quote:
Originally Posted by RD Blakeslee
Hi Tom,

It seems to work well:
http://www.rcgroups.com/forums/showthread.php?t=529118

Rather than guestimate the production model's price, I'll ask Del Monday.

World Hobby,

It's my understanding that the first batch of production models will be avaiable quite soon. The folks at West Mountain Radio could tell you.

- RD
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Old Jun 12, 2006, 11:54 AM
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France
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Hi Del, would you maybe think of possibility to get rid of the 0.9V or 160A limit, for short bursts at least ?
The point is that in some competitions like F5B, we are trying to extract as much as a cell can supply, and as you know this typically happens exactly at just half of a cell's nominal voltage. Hence a NimH cell will supply more power @ 0.6V which will likely at close to 300 Amps for the good cells than at 160A where voltage will usually be in the 0.8-0.9V range (depending on t obviously).
I understand we are talking of a niche there,but if the system would allow by pass of protections for just graphing 5 second bursts this would be just enouh to satisfy the craziest
With that we could alo see better if/where there are physical/mechanical or chemical limits to the bursts a cell can really output.

FYI current state of the art 16 cells Nimh pack have been measured @ 3600W+ / 270A at the beginning of a burst inside a F5B glider - this is a very amazing voltage for such high amps but they need to be HOT (~80-85C) ! At the end of the burst ie about 4 seconds later current was still 240A. The poor 2.1 kg "gliders" skyrocket up @ around 240 km/h with this amont of power !
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Old Jun 12, 2006, 12:38 PM
Del Schier
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Joined May 2002
73 Posts
Actually the 0.8 volt 160 A is not a limit, it is a spec.

The limit depends on ohms law. With a "perfect battery" the Juicer may do 200 amps. We do have it fused for 180 amps but a battery would be dead before you could blow those fuses at 200 amps.

We have an FET "on" resistance plus other circuit resistance inside our product. Add the internal resistance of the battery and the associated connections and by ohms law that limits the maximum current.

Below a voltage where our FETs are full on, in order to regulate the current below that voltage we will no longer be able to regulate a constant current.

Our tests with a GP 3300 160 A shows that 160 amps is a reasonable typical spec. That doesn't mean you can't pull higher current from some other cell at a higher voltage. Of course you should not exceed the 500 watt continuous limit for the system.

If it wasn't for ohms law you would be able to pull 500 amps from a 1 volt cell

BTW as soon as we catch up on orders we plan to have a kit for two amplifiers in series parallel for 1000 watts and double the current (half the resistance).

I hope this makes sense.

Thank you,

Del Schier

West Mountain Radio
18 Sheehan Ave.
Norwalk, CT 06854
http://www.westmountainradio.com
tel: 203 853 8080
fax: 203 299 0232

Quote:
Originally Posted by Protocooler
Hi Del, would you maybe think of possibility to get rid of the 0.9V or 160A limit, for short bursts at least ?
The point is that in some competitions like F5B, we are trying to extract as much as a cell can supply, and as you know this typically happens exactly at just half of a cell's nominal voltage. Hence a NimH cell will supply more power @ 0.6V which will likely at close to 300 Amps for the good cells than at 160A where voltage will usually be in the 0.8-0.9V range (depending on t obviously).
I understand we are talking of a niche there,but if the system would allow by pass of protections for just graphing 5 second bursts this would be just enouh to satisfy the craziest
With that we could alo see better if/where there are physical/mechanical or chemical limits to the bursts a cell can really output.

FYI current state of the art 16 cells Nimh pack have been measured @ 3600W+ / 270A at the beginning of a burst inside a F5B glider - this is a very amazing voltage for such high amps but they need to be HOT (~80-85C) ! At the end of the burst ie about 4 seconds later current was still 240A. The poor 2.1 kg "gliders" skyrocket up @ around 240 km/h with this amont of power !
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Old Jul 28, 2006, 10:44 PM
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Beta software has been released which causes the CBA with the amplifier to read amps and amp hours correctly.

Overlays of curves of the same cell discharged through the CBA alone show a higher voltage for the CBA alone than for the CBA and amplifier. The voltage divergence appears to increase with increasing amperage and reaches about .05 volts @ 22 amps.

The three curves shown @ 22 amps were generated in the following order: first a curve (black) with the amplifier, then one (red) with the CBA alone, then the third (green) with the amplifier, to assure that the voltage difference shown was not a real voltage difference caused by cell degradation @ 22 amp (10C) discharge rate.

- RD
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Old Jul 28, 2006, 10:49 PM
Southern Pride
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Haralson County GA. USA
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For those interested I received an e mail a few days ago from WMR stating the new CBA amplifier unit was available for ordering at $469.95.

Charles
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Old Jul 31, 2006, 10:20 AM
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Bellingham WA
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Hello RD,

Have you been able to come up with any way to correct the voltage drop issue?

Tom
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Old Jul 31, 2006, 10:29 AM
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Tom,

Not yet, but it's being looked at.

- RD
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