[jhoelter]

Heya head-fi'ers,

I have a question about rechargeable batteries. I was looking at specs for 9V batteries and appearantly typical mAh for alkaline 9V batteries are 500-700 mAh. However, the most I've seen for a NiMH rechargeable 9V battery is 170mAh.
(I was looking at Thomas Distributing)

I even emailed them and was told that there is indeed that much difference in mAh between alkaline and NiMH. However, I'm also aware that on high-drain sources like digicams that even though alkaline AA's might have more mAh (maybe 2800mAh) they never realize that potential, and NiMH rechargeables (maybe 1800mAh) actually perform better.

So my question: will I get a decent life-span out of NiMH 9V's in a portable amp application, or am I better off sticking with alkaline? Any of you out there with cmoy/CHA47's care to comment?

Thanks,
Jeff

 

[DarkAngel]

You will go broke feeding a headphone amp batteries. I have Grado RA1 and it uses 2 nine volt batteries, for new alkalines
you pay $5 or more a pair. That would cost me over $10 a month
for moderate use.

NiMH only last half as long as alkalines, but you can buy 4 NiMH 9 volts plus wall charger for under $40.......pays for itself in a couple months, just keep a pair charged in advance of required change.

Bottom line figure NiMH only last 1/2 as long as alkaline, but they
are no brainer to save money.

 

[Hirsch]

I'm not sure why, but the Radioshack NiMH 9 volts completely sucked the midrange out of my Grado (they only run at 8.4 volts, but some 9 v NiMH run as low as 7.2 volts. Very few actually put out 9 v). Or, maybe Radioshack just makes a lousy battery. The ones at Thomas look interesting...

 

[DarkAngel]

Hirsch
I agree those "maha" rechargeable NiMH 9 volts from Thomas Dist. look to be much better quality than the ray-o-vacs I am currently using.......tempting to get some and try out.

In another thread a while back I e-mailed Grado about any effect if battery is 8.4v vs true 9v and they said it makes no difference.
But if was just starting I would definitely get those maha's.

My ray-o-vacs are 8.4v/150mAH while the mahas are 9v/160mAH

 

[Hirsch]

Thomas also has a Plainview, which is 9.6 v/ 170 mAh...of course, now I'm wondering if 9.6 v is too much for the Grado...

I may give them a try just to find out.

 

[Hirsch]

In looking at rechargeable NiMH 9v batteries, they ranged from a low of 7.2v (Energizer) to 8.4v 150 mAh (Ray-o-vac. Radio Shack) to 8.6 v 160 mAh (Maha) and maxed out at 9.6v 170 mAh (Plainview). There may well be others...these are the ones I looked at. The first time I tried NiMH rechargeables with the RA-1, I thought the Radio Shacks sucked the midrange out and went back to alkalines immediately. However, I decided to try again. This time I opted for the most powerful I could find: the Plainviews. So...

I put pair of Plainview 9.6v 170 mAh batteries in my RA-1 last night. The first thing I did on listening was to back off the volume control. The second thing was to test the alkalines that I pulled (they were still good). The third thing was to say "Holy S**t!!" These things work! Not only do they work, but they may work better than the 9 volt alkaline I was using(Duracell Ultra). My impression is that the bass is a bit more extended, with a slightly fuller midrange and more open highs...things that would happen with an improved power supply. BUT:

Caveats: The alkalines I was using were not new. What I was hearing could have been the difference between aging and fully charged batteries (although I've never gotten an impression of improvement changing batteries previously). Also, in going back to the alkalines, the differences seemed more subtle than my original impression (but there). I'm not entirely sure that what I heard is real and replicable...placebo effects happen (although I wasn't expecting improvement...just hoping that the NiMH would not cause sonic deterioration as the last ones did). The time taken to change 9v batteries is just long enough so that I'm not absolutely convinced my memory of the sonics is good enough to be certain of the differences I was hearing. However, there's that immediate increase in volume on same disc and volume setting I was listening to that afternoon...that was real enough.

YMMV. This could all be in my head. OTOH, I'm now sold on using rechargeables, and not just to save money. The RA-1 is still sounding good to me today...

 

[DarkAngel]

Thanks for report Hirsch
I was almost tempted to try Mahas, just found those Plainview NiMH 9 volts you referred to, kind of hidden in small print. Cost is almost twice that of Ray-o-vac set-up, 4 Plainview 9 volts plus two of the special chargers are @$60.......tempting to try, if I didn't already have ray-o-vacs and was just starting I would spend the extra for Plainview set-up.

You could skimp and just get 2 Plainviews and not have the luxurary/convienance of 2 sets........am I talking myself into this purchase?

 

[Xevion]

I use Rayovac rechargable alkalines for my stuff, they seem to work well, although I doubt they effect the sound quality short of something with a lower then advertised voltage

.

 

[freeflight]

Quote:

Originally posted by Hirsch In looking at rechargeable NiMH 9v batteries, they ranged from a low of 7.2v (Energizer) to 8.4v 150 mAh (Ray-o-vac. Radio Shack) to 8.6 v 160 mAh (Maha) and maxed out at 9.6v 170 mAh (Plainview). There may well be others...these are the ones I looked at.

Where did you find the rating of those batteries?
How come the Energizer is 7.2V?

 

[Hirsch]

Quote:

Originally posted by freeflight Where did you find the rating of those batteries? How come the Energizer is 7.2V?

I found the ratings of the batteries either by looking at a web site (Thomas Distributing is good) or by looking directly at the packaging of the battery (Energizer, Radio Shack).

I have no idea why the Energizer is 7.2 v. It will still drive most 9 v devices, but you'd have to ask the manufacturer your question.

The Plainview is the only NiMH rechargeable that I'm aware of that can output a true 9 v under load.

 

[gaineso]

NiCad & NiMH cells are 1.2 volt. Alkaline cells are about 1.56 volt. Alkaline 9 volts use a stack of 6 cells. Rechargeables vary in the number of cells. A 6 cell would be 7.2 volt, 7 cell 8.4 and 8 cell 9.6. 9.6 shoudn't hurt any devices that are designed for alkalines, but with lower voltages, you're starting off with the equivalent of run-down batteries. Fine for toys, but HiFi demands the proper power at all times.
I use alkalines in my Total Airhead, about a set a week, sometimes a little more oftem. Buy Alkalines at Sam's or Costco or stick with the expensive Rechargeables

Gaines

 

[DarkAngel]

Hirsch
Before I do something foolish like order the Plainview 9 volts
and special recharger one question. From the photo it appears
the recharger only accepts one 9 volt battery at a time! This means buying two rechargers or going through two cycles just to get charged pair.

Tell me my eyes are being decieved (if not what a pain in the ass!)

 

[Hirsch]

Darkangel,

Alas, your eyes are good.

You need to go through 2 charge cycles to charge a pair of the Plainviews (or get two chargers). Charge cycle if the battery is completely discharged is about 9.5 hours, which also allows for about 20-25% overcharge (I got this directly from Plainview, as the instructions printed on the battery are for a lower powered charger). Alternatively, you could get the Energex Tri-Charger on the Thomas site. However, this is a 16 ma charger, and would take about 18+ hr to fully charge the batteries (problematical, as it has an automatic shutoff at 15 hr)

I got two pairs of the Plainviews, so having one pair out charging for a day or two is no big deal for me. The charger is not a smart charger, so it's possible to damage the batteries if left in the charger too long. I put the charger on a lamp timer, so it automatically shuts off after the charge cycle. (However, Thomas indicated to me unofficially that the battery can handle being in the charger up to 24 hr...but if the battery gets uncomfortably hot to the touch, it's been there too long).

Error correction: optimum charge time is 8.5 hr, not 9.5. sorry about that!

 

[freeflight]

Quote:

Originally posted by gaineso NiCad & NiMH cells are 1.2 volt. Alkaline cells are about 1.56 volt. Alkaline 9 volts use a stack of 6 cells. Rechargeables vary in the number of cells. A 6 cell would be 7.2 volt, 7 cell 8.4 and 8 cell 9.6.

This is so disappointing that people (Energizer) actually reduce 9V to 7.2V in order to save one damn cell.

 

[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.