anyone know why the SR-71 won't work with LiIon batteries?

[Guest receph]

AFAIR, there is a diode after each 9v battery, and two sets of caps between V+ and ground and V- and ground each. There is a series resistor inside each 9V rechargeable lithium battery, as I recall, but I can't figure out why they won't work with the SR-71.

Any ideas why?

[aardvark baguette]

because I require food energy to function. not batteries.

Failing that, Mountain Dew.

[Guest receph]

because I require food energy to function. not batteries.

Failing that, Mountain Dew.

you duplicate sound in real time?

[aardvark baguette]

**clears throat** "ahhhhhhhhh".

[hYdrociTy]

because it's no longer pretend dual mono

[Guest receph]

Another piece of humor that escapes me?

Guess I'm not yet in synch with this forum, but I am trying.

Seriously, anyone know?

[deepak]

Another piece of humor that escapes me?

Guess I'm not yet in synch with this forum, but I am trying.

That's pretty obvious.

[justin]

AFAIR, there is a diode after each 9v battery, and two sets of caps between V+ and ground and V- and ground each. There is a series resistor inside each 9V rechargeable lithium battery, as I recall, but I can't figure out why they won't work with the SR-71.

Any ideas why?

What happens if you put in an alkaline 9V and a li-ion 9V?

[Guest receph]

I haven't tried, and I don't have any alkalines lying around.

Before I spend any money.. there is a point to what you're saying, I would presume. Do you suspect it is the cutoff inside the lithiums that might be faulty?

[n_maher]

Yes, now it's the confusing moniker of 'dual headphone amplifier', whatever the heck that means.

[justin]

There is no point, but if it doesnt work w/ 2x li-ion (what exactly do you mean by it doesn't work), then try 1x li-ion and 1x alkaline, and then see if it makes any difference if the li-ion is on the + or - side

inside each cell is probably a protection circuit that looks something like this, so that needs to be added to the schematic

[Guest receph]

Thanks, I'll try it with one NiMH and one Li-Ion.

With 2 Li-Ions it works for ~.5sec when I connect the second battery and when I disconnect it, but not when they're in.

The circuit has, as far as I can tell, one diode each at the +V and -V of the batteries, dropping to two parallel caps and the opamps and buffers with filter caps, pretty standard except for the diodes. I bypassed the diodes but it still did not work (duh!).

Don't have a schematic I can post, and am unsure of the circuit, anyway.

[Guest receph]

Just out of curiosity, the thermometers cost ~$2 ea.

You sure there is one in each battery?

[justin]

i dont know if they would have built in temperature protection, but they would at least have voltage and current protection. maybe the capacitors are enough to trigger the discharge current protection. try putting a resistor 10-100 ohms in series with each cell and see if it works

[Guest receph]

I'll give that a try and post my results.

[jinp6301]

does anyone else think its funny that justin is answering questions about the SR-71?

[Guest sacd lover]

does anyone else think its funny that justin is answering questions about the SR-71?

He probably knows more about the design than Ray does.

[kevin gilmore]

does anyone else think its funny that justin is answering questions about the SR-71?

Because i'm to busy...

My guess is that the current draw is actually too low to keep the battery

protection circuit turned on. Some of the Li-ion batteries do that. They are

designed for a minimum of 10% power draw.

And justin clearly knows more about that circuit than resistor ray.

[Guest receph]

The debate just ended so I can post.

It's weird. When I hook up two NiMHs with alligator clips, then, as the

amp is running, switch one to iPowerUS Li-Polymer, then the other, it

keeps running.

But when I power up with a Li-Poly battery on one side, either side, and a NiMH on the other, or with both sides with Li-Polys, it powers up for

~.5sec and then shuts down.

[kevin gilmore]

If this is true, then it is likely that the batteries charging the capacitors is causing

an overcurrent condition and the batteries are turning off. Look up what the maximum

output current for the battery is, replace the diodes with resistors to limit the

maximum current. Should work fine. And drop less than the .7 volts that the diodes

require. Don't ever get the batteries in backwards.

[Guest receph]

Don't ever get the batteries in backwards.

Only if I want the real Blackbird, with flames coming off its butt, and all...

[Grahame]

Only if I want the real Blackbird, with flames coming off its butt, and all...

[Guest receph]

Yes, of course, a 25ohm resistor at v- and v+ solved the problem.

What else? (my 20/20 hindsight is working perfectly)

Thank you guys

I guess I was hoping that those thingies that look and act like diodes

were "secret" components RS built and custom painted, this time with a

devious substance that does not resemble nail polish. What a

disappointment...

[spritzer]

What a

disappointment...

This should be the RSA motto...

[kevin gilmore]

Yes, of course, a 25ohm resistor at v- and v+ solved the problem.

What else? (my 20/20 hindsight is working perfectly)

I smell a high priced military spec modification service being offered by APL.

Say $1500 to modify your sr-71a.

Actually a pair of the appropriately rated CRD's or fets wired for same would

be better than either diodes, or resistors.