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Rechargable 9V Batteries and Wireless Packs


skinda0

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Hi all,

I decided to look at getting some rechargable 9V batteries for wireless mics and beltpacks as I thought there must be a better alternative to just buying and then throwing away the old batteries once they are dead.

I have done a bit of research and found some of the lithium and Ni-MH 9V batteries. Has anyone used these in their wireless packs with success as I have read the voltage is lower (1.2 x 6 = 7.2V) on these batteries due to them having the same number of cells as regular 9V.

 

EBL Lithium EBL Hi-MH

 

I have also seen some with a micro-USB on them for recharging which seem interesting.

Edited by skinda0
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The mics will normally work ok except the battery level monitoring will be useless because the discharge characteristics are very different from alkaline. NiMH PP3 are normally about 8.4V fully charged, not sure about lithium version. However if you make sure you replace and charge after every show then that shouldn't be a problem. What mics are you using?
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The mics will normally work ok except the battery level monitoring will be useless because the discharge characteristics are very different from alkaline. NiMH PP3 are normally about 8.4V fully charged, not sure about lithium version. However if you make sure you replace and charge after every show then that shouldn't be a problem. What mics are you using?

 

I have a few EV RE-2 mics, handheld and beltpacks and Sennheiser Freeport also handheld and beltpack that use 9Vs.

The Sennheiser G3s have been ok with rechargable AAs.

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I use NiMH cells in our Shure beltpacks, and they are fine. But you are right about voltage, mostly. Some 9v rechargeables have an extra cell, and are much closer to 9v. We use cells designed for vape machines. Shop carefully! - Ours were described as : "Replacement for 9V Alkaline 8.4V 280mAh rechargeable NiMH PP3 battery Vapex-Tech" and have been fine.
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I have a few EV RE-2 mics, handheld and beltpacks and Sennheiser Freeport also handheld and beltpack that use 9Vs.

The Sennheiser G3s have been ok with rechargable AAs.

I've used NiMH in freeports with no problem, they have no battery level monitoring worth speaking of anyway.

 

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I have used MIHM's but to be honest I don't like the way the voltage suddenly drops off, without any warning in mics and I don't find them to be as long lasting, both in capacity per charge and number of times they can be charged as the old NiCad's. I reckon I've had 100 or so over the years and now I find it so much easier to use alkalines and I think Trantec S4 mics work better with them too.
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The lithium PP3s have a lithium cell and boost converter inside so they should theoretically put out a fairly solid 9V for the full discharge.

 

Being lithium based with internal micro USB charge port and indicator LEDs you get an exact indication of full charge.

 

One significant caveat might be whether the wireless pack was happy with a PP3 that will potentially be introducing switching noise.

 

If these worked then I think you can get multi-tail micro USB fan out cables that could make charging very convenient. Especially with a custom dock that presented the sockets for easy access while shielding the end terminals.

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I'd been meaning to ask most of these questions, so thanks to all!

I have been using GP batteries (most recently the "ReCyko" branded ones) 8.4V 200mAh rechargables from CPC for Trantec VHF packs (mostly S3500). When new this works well, and the oldest one is still fine, but some of the others now fade very rapidly! I want to measure some discharge curves and the cut-out voltage of the packs but have not found the time.

 

One warning is that with these older packs you still get full carrier at the receiver well after there is not enough voltage to keep the transmitter working properly, so you get various nasty sounds with no indication what is going on from the receiver end.

As a consequence I had been looking at both 9.6V batteries and the lithium ones with internal electronics, but also of the potential issues Big Clive has raised. Can anyone suggest a reputable / stable supplier for the latter rather than Amazon Marketplace?

The Vapextech ones I have seen several places, and whilst the name doesn't seem a great start, their own website has a fairly decent data sheet for them. They certainly seem a decent idea, and should keep a workable terminal voltage for longer than an 8.4v stack. I suspect they will still be vulnerable to one cell in the stack drying out and the whole thing going high impedance however - and I have no idea where to get a charger which will charge 9.6V NiMH batteries sensibly (convert a R/C racing car charger?).

 

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The lithium PP3s have a lithium cell and boost converter inside so they should theoretically put out a fairly solid 9V for the full discharge.

 

Being lithium based with internal micro USB charge port and indicator LEDs you get an exact indication of full charge.

 

One significant caveat might be whether the wireless pack was happy with a PP3 that will potentially be introducing switching noise.

 

If these worked then I think you can get multi-tail micro USB fan out cables that could make charging very convenient. Especially with a custom dock that presented the sockets for easy access while shielding the end terminals.

I was at an event in the summer and there was a significant buzz on their radiomic [Trantec S1 HH], the user blamed the 650VA generator the system was running on. I offered an alkaline battery when theirs went flat and the buzz stopped. I don't know what the battery was [silver can with the remains of a peeled off lable] but in hindsight it could have been the case.

 

I have inspected a Saft lithium which had exploded during charging and it appeared to be 3 cells in series. I guess 1/2AA size would be too big but something like that.

Edited by sunray
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I tried rechargeables years ago and quickly reverted away from them.

The sudden drop off rendered the meters on the RX useless and it was quite scary going from three bars to no bars within minutes.

Ensuring there were always units charged up/charging is just another job you can do without.

For the price and predictably of decent AAs when bought in bulk, IMO rechargeables aren't worth the hassle.

 

 

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I tried rechargeables years ago and quickly reverted away from them.

The sudden drop off rendered the meters on the RX useless and it was quite scary going from three bars to no bars within minutes.

Ensuring there were always units charged up/charging is just another job you can do without.

For the price and predictably of decent AAs when bought in bulk, IMO rechargeables aren't worth the hassle.

 

 

Totally my experience too, except I only have cheaper mics without the battery monitoring facilities, I start hearing when there's a problem and get a spare 'out there quick'. Likewise I think rechargeables are too much hassle now.

 

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I tried rechargeables years ago and quickly reverted away from them.

The sudden drop off rendered the meters on the RX useless and it was quite scary going from three bars to no bars within minutes.

Ensuring there were always units charged up/charging is just another job you can do without.

For the price and predictably of decent AAs when bought in bulk, IMO rechargeables aren't worth the hassle.

 

I would refer the honourable gentleman to my old topic here - two years on and not a single problem, no WEEE waste, lots of happy customers and a clear environmental conscience.

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History saw the rise of the rechargeable AA cell as 1.2v 500mAh today these cells are 1.2v but 2000mAh. Likewise the PP3 has risen from 80mAh to up to 300mAh

 

Whether your radio pack correctly indicates the battery level it's highly likely that a safe system of using and charging rechargeable batteries can be found.

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