[freeflight]

Quote:

Originally posted by aeberbach Consider that if they did add one more cell then the voltage would still only be 8.4V, but then the capacity would be smaller. And the battery would last disproportionately less time, because when voltage goes up current does also. There are some "9V" rechargables around that are really 9V, but it rarely matters. WRT the rated capcaity of all these different kinds of battery, the number doesn't tell you anything about whether or not it can drive a Grado amp or other device, it tells you how long it can do it for if it can do it at all. NiCd batteries are among the most powerful when it comes to delivering high currents - electric model aircraft usually use NiCd in preference to anything else because they can drive very powerful motors at currents of up to 80A. NiMH and LiIon typically can't.

This is comforting. Thanks.

 

[gaineso]

If you're trying to drive an amp that's designed for 9 volts and you power it from a battery that's only putting out 8.4 volts, you are starting out with a power loss of 7%. That's not really a lot, but these little solid state circuits are very sensitive to power. I'm not sure exactly what is being driven with these 9 volt batteries, but an amp is going to be way down on power, far more than 7%, maybe as much as 15% or more. There may also be some distortion and clipping issues that should probably be discussed with the manufacturer.

If you're spending the money to try to get the best audio performance, don't scrimp on supply power. Either get the full 9 volt rechargeables, or go to Sam's or Costco and buy alkalines in bulk.

You may also be able to rig a 6 cell AA holder with a 9 volt connector, depending on portability requirements. Be sure polarity is right. Be a shame to blow an amp.

Stay away from underpowered, unervoltage batteries and you'll be a lot happier.

Happy holiday and give a special prayer for the guys fighting the new war.

Gaines

 

[Jrook]

I have a buddy that works on pro video equipment and broadcast uplink power supplies he said that he has seen 9volt size lithium batteries that are found deep in the guts of these cameras. He said they are desinged to power up certain parts of the camera if there is a power glitch. These things actually have really good specs with a true 9 volt output at 500 milliamps. The only problem is I can't find them for sale anywhere. My buddy said he has never tried to buy a replacement and thinks that the camera manufacturers have them built for them and must be quite expensive. Im gonna keep looking for them.
JC

 

[Eagle_Driver]

Heh, alkalines can't even sustain their full voltage for longer than the first 5 to 10 percent of their rated life! The trouble with using them in a relatively high-drain device is that they gradually lose voltage with use, so that their average sustained voltage is only about 80 percent of their rated voltage (i.e. 1.2V for most sizes, 7.2V for a 9V battery). On the other hand, most rechargeables operate at or near their full rated voltage for most of their rated run-time between recharges - but then they drop off suddenly when they're nearly depleted.

 

[freeflight]

Quote:

Originally posted by Eagle_Driver Heh, alkalines can't even sustain their full voltage for longer than the first 5 to 10 percent of their rated life! The trouble with using them in a relatively high-drain device is that they gradually lose voltage with use, so that their average sustained voltage is only about 80 percent of their rated voltage (i.e. 1.2V for most sizes, 7.2V for a 9V battery). On the other hand, most rechargeables operate at or near their full rated voltage for most of their rated run-time between recharges - but then they drop off suddenly when they're nearly depleted.

Sounds like a reason to get some good rechargeables.

 

[danieln]

Rechargeables are able to produce much higher current (hence power) than alkalines, so power should not be a problem.

Also, I found that contrary to what many manufacturers say, regular Ni-Cd chargers will charge Ni-Mh rechargeables without problems. For those of you who need to charge 2 9V batteries at once, there are relatively cheap chargers at Radio Shack ($15? I forget how much I paid for mine) that allow you to charge 2 9V batteries at once.

 

[freeflight]

Quote:

Originally posted by Hirsch Error correction: optimum charge time is 8.5 hr, not 9.5. sorry about that! [/B]

Hi, Hirsch, thanks for info. Got mine today.
Could you tell me where I can find more info about those Plainviews?

 

[Hirsch]

The Plainview Batteries site (www.plainviewbatteries.com) has almost no information except how to order. There's actually more information on the Thomas Distributing site. If you have specific questions, both Thomas and Plainview are good about answering e-mail.

I got nervous that the battery says 17 ma max for the charger, while the charger is rated at 25 ma, so I started asking questions at Thomas and Plainview (the 25 ma charger is the right one). I got the formula for computing charge time in an e-mail from Plainview : take the battery rating (170 mAh), multiply by 1.25 (allowance for slight overcharge) and divide by charger rating (25 ma) = 8.5 hr (note that this time would be less if there was still a charge on the battery).

I'm really happy with the Plainviews so far. My usage was down the week of Thanksgiving, but I estimate that I've had them in for around three weeks, with about 25 hours of playing time in the RA-1 over that period. Still going strong, and I haven't had to switch to my second set of batteries yet. I'm really curious just how long a charge will last...

 

[Hirsch]

Well, my CT-470 says it gets 40 to 50 hours per set of batteries (two AAA NiMH and two AA alkaline). I don't use skip protection, so I should get near the top of that. The "low charge" indicator just went off, and I had recharged the NiMH batteries and put in new alkalines at the same time I put the Plainviews in the RA-1 (I use these together). So far, the Plainviews have been absolutely stable in the RA-1...sounds as good today as when I first put them in...but I wasn't expecting a charge to last anywhere near this long. I hope my second set of Plainviews is as good as the first...I thought I would have had to put them in the RA-1 by now

 

[Hirsch]

Finally had to change out the Plainviews today. The loss of the charge is not a subtle effect. One minute the amp was sounding fine, the next I thought I had a bad cable connection. I was actually testing the connections before it even occurred to me that the batteries might be discharged

Even so, not bad at all. The charge on the Plainviews in the RA-1 seems to last about the same amount of time as an alkaline! ISTM that's an unusually long useful charge for a rechargeable battery.

Still, I'm Jewish, and it IS Hanukkah...