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Lectrosonics SMDWB battery use questions


valvashon

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Due to the 600 MHz band going away, we recently replaced our Sennheiser microphone equipment with Lectrosonics SMDWB series microphone packs.  We initially tried using NiMH rechargeable batteries, but found that the low initial voltage was causing shutdowns.  Our morning show is nearly 6 hours long and the batteries just weren't lasting the whole show.  We then switched to "Tenavolts" lithium rechargeable batteries and have been getting much better results with them, except for the occasional high pitched squeal or whine that happens sometimes, at a low level compared to the actual audio, after the mic packs have been on for several hours.

 

These are the dual battery model, and my theory was that the step down circuit in the lithium batteries is causing this.  It's essentially a switching power supply and when there are two of these in parallel they run together, except for the times that the switching frequency gets off a bit from each other, then you get the high pitched squeal.  I did try running a mic from only one lithium battery this morning to see how long it would last, but only got about 3 1/2 to 4 hours out of it before it shut down, even though it showed that it had 1.5 volts.  I put in a different lithium rechargeable that shows only 1.42 volts and it seems to be staying on.  I'm guessing that I might have to try the single battery theory more than once.

 

So- does anybody else have an idea as to why the microphones sometimes start to emit a high pitched squeal when using two lithium cells?  We really don't want to keep using the alkaline batteries as we are trying to reduce waste whenever we can.

 

And for the person who is going to post that lithium batteries are recommended for the single battery model and that alkaline are recommended for the dual battery model, we know that.  But we want to use rechargeable batteries, not disposable ones.

 

Thanks

 

Val

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Val- "So- does anybody else have an idea as to why the microphones sometimes start to emit a high pitched squeal when using two lithium cells?  We really don't want to keep using the alkaline batteries as we are trying to reduce waste whenever we can."

 

LEF- You answered that yourself in that it is indeed the two supersonic switching supplies in the batteries running at slightly different frequencies and generating an audible beat frequency into the transmitter. That beat frequency is dumped directly into the battery case and propagates into all the internal grounds.

 

Val- "We initially tried using NiMH rechargeable batteries, but found that the low initial voltage was causing shutdowns." 

 

LEF- The low initial voltage should not cause any problems as the constant 1.2 Volts of the NiMh batteries is well above the minimum voltage of the SM series. The transmitters shutdown at voltages less than 0.9 Volts, which is well above the voltage even with old NiMhs. My guess is that the battery LED showed red and you assumed it was about to shut down. That LED will not (!) and cannot (!) work with NiMh batteries because of there very flat discharge curve. Put a piece of black tape over the LED and use the NiMh batteries. You should get about 8 hours of use out of two Eneloop black batteries or an Amazon high capacity NiMhs. Others have had good luck with IKEAs also. Stay away from all other NiMh batteries. You also might Google some of the NiMh battery tests that others have done to see why those three brands are good choices. There are some batteries whose specs are written by the sales department and not by the engineering department.

Best Regards,

Larry Fisher

p.s. You mentioned shutdown at 1.4 Volts which should be impossible. I assume (that word) this was an open circuit measurement outside the transmitter?

Edited by LarryF
plurals for batteries
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6 hours ago, BAB414 said:

Larry, thoughts on PowerEx AAs inside the transmitters (if you can say)?

Google some AA battery reviews. It has years since I ran any tests, but I remember Powerex not meeting their stated capacity and not taking many discharge cycles before dropping in capacity. Try to find articles that are recent and not just a disguised ad.

 

Here's a long article but well worth reading. It has an interesting history of NiMh batteries. From what I know about batteries and the tests I have run, the article seems to be dead on.  https://www.filterjoe.com/2017/08/19/best-aa-rechargeable-batteries-and-chargers-2018-update/

 

Here's a test that ran the batteries at an 8 hour discharge rate using portable fans. The current pulled would be comparable to a dual battery charger. Advice is similar to the article above but much shorter.  https://www.reviewed.com/home-outdoors/best-right-now/the-best-rechargeable-batteries

 

Best Regards,

Larry Fisher

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7 hours ago, LarryF said:

Google some AA battery reviews. It has years since I ran any tests, but I remember Powerex not meeting their stated capacity and not taking many discharge cycles before dropping in capacity. Try to find articles that are recent and not just a disguised ad.

 

Here's a long article but well worth reading. It has an interesting history of NiMh batteries. From what I know about batteries and the tests I have run, the article seems to be dead on.  https://www.filterjoe.com/2017/08/19/best-aa-rechargeable-batteries-and-chargers-2018-update/

 

Here's a test that ran the batteries at an 8 hour discharge rate using portable fans. The current pulled would be comparable to a dual battery charger. Advice is similar to the article above but much shorter.  https://www.reviewed.com/home-outdoors/best-right-now/the-best-rechargeable-batteries

 

Best Regards,

Larry Fisher

Wow. Super thorough. Thanks for all the info. I've been using PowerEx with lectro for a while and it's true the batteries degrade a bit quickly but even on my older ones I get at least a good four hours. Never did a proper test and I'm pretty sure they can do at least 6 hours but I switch them out early to be safe.

 

Is it me or do the Venue 2 and SRb and SRc not have a NiMH Tx setting?

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19 hours ago, BAB414 said:

Wow. Super thorough. Thanks for all the info. I've been using PowerEx with lectro for a while and it's true the batteries degrade a bit quickly but even on my older ones I get at least a good four hours. Never did a proper test and I'm pretty sure they can do at least 6 hours but I switch them out early to be safe.

 

Is it me or do the Venue 2 and SRb and SRc not have a NiMH Tx setting?

Try a letting the transmitter run until it dies when you have some free time. That will give you more confidence in the use of NiMh.

 

There is no NiMh setting; that is what the battery timer is for. It does require some simple battery discipline in that you have to KNOW that the battery is 100% charged when the timer is started and not mixed with partially discharged ones.

Best Regards,

Larry Fisher

 

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  • 3 weeks later...

val,

 

I was curious if you tried using the non-rechargeable lithiums and had any data on how long they last with the SMDWBs.  I was also curious if you know why they recommend the alkaline.  I wish they had a chart for all the models the way they do for the SMQV's. https://www.lectrosonics.com/SMQV-super-miniature-double-battery-belt-pack-transmitter.html#battery-life-chart

 

Battery: AA, disposable SMWB Lithium recommended SMDWB Alkaline recommended

Battery Life w/ AA: SMWB (1 AA): Lithium 4.4hrs SMDWB (2 AA): Alkaline 11.2 hrs

 

Not sure how/why the SMQV's reportedly get such better battery life (or how the SMDWB can get 11.2 on alkaline versus the SMQVs only getting 6 hrs at most).  Almost seems like something might not be right with their data (or if the data is based on using the SMDWB as a recorder, instead of a transmitter - 8GB HD mono recording time listed as 11hrs 12 minutes = 11.2 hrs)

 

I thought about getting some LTs, but the battery life seems poor in comparison to the SMQVs (which only offer a limited frequency band) while the SMDWBs have a recording function but can't transmit at the same time, which isn't something I think I would need too often.

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23 minutes ago, Southeast Sound Guy said:

[snip]I was curious if you tried using the non-rechargeable lithiums and had any data on how long they last with the SMDWBs.  I was also curious if you know why they recommend the alkaline.  I wish they had a chart for all the models the way they do for the SMQV's. https://www.lectrosonics.com/SMQV-super-miniature-double-battery-belt-pack-transmitter.html#battery-life-chart

 

 

The testing labs want to test each transmitter, etc., with each type of batteries that are "recommended". If we put a chart showing alkaline, lithium, and NiMh in the manual that is submitted to them, they then run three different testing routines. So to list a different battery costs about $10,000. I can't believe that BS, either particularly since the units regulate the internal voltages and don't change any parameters at any voltage of battery type. Anyway, that is why there aren't multiple battery charts in the manuals. Once more, bureaucracy overcomes common sense.

Best Regards,

Larry Fisher

 

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7 hours ago, LarryF said:

The testing labs want to test each transmitter, etc., with each type of batteries that are "recommended". If we put a chart showing alkaline, lithium, and NiMh in the manual that is submitted to them, they then run three different testing routines. So to list a different battery costs about $10,000. I can't believe that BS, either particularly since the units regulate the internal voltages and don't change any parameters at any voltage of battery type. Anyway, that is why there aren't multiple battery charts in the manuals. Once more, bureaucracy overcomes common sense.

Best Regards,

Larry Fisher

 

$10K per battery test! Wow 

 

is that a government regulation forcing that independent testing cost upon you, as can’t you run a test in house much cheaper and put those values into the manual yourself?

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19 hours ago, IronFilm said:

$10K per battery test! Wow 


It‘s not a battery test, it’s a transmitter test (for FCC and CE marking purposes), which apparently needs to be repeated with each battery type. 
And... perhaps... I should let Larry get this. 

 

On 12/5/2019 at 6:57 PM, valvashon said:

recently replaced our Sennheiser microphone equipment with SMDWB


are these perhaps a littler older, may a year or so? Check the settings, especially power, with regards to battery life. On 50mW I get exactly 8 hourse on Nimh in an SMQV. I would be really surprised if a the newer tx couldn’t match that. Also try if in your setting you can get by on 30mW. That should definitely get you through the 6 hour mark

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1 hour ago, Constantin said:

It‘s not a battery test, it’s a transmitter test (for FCC and CE marking purposes), which apparently needs to be repeated with each battery type. 

 

That is of course what I meant by “battery test”, testing each battery type with the transmitter. 

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9 hours ago, IronFilm said:

That is of course what I meant


there‘s no „of course“, because your next sentence suggests you think it’s about the battery, but it isn’t, per se:

 

On 12/28/2019 at 4:24 AM, IronFilm said:

as can’t you run a test in house much cheaper and put those values into the manual yourself?


it’s about the tx and how it behaves with different batteries in terms of rfi, emi, and whatever else, but not really runtimes. If they put more battery types in the manual that becomes an official recommendation and they need to show that the tx stays within parameters. That’s where that lab comes in. Don’t know about US, but in the EU that is basically a government regulation (ETSI).

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The data sheets and operating manuals that they provide often do not say what parameters the units are being operated under, which leaves the end user with doubt about the actual usage times that they can get.  For example, the alkaline recommendation for the SMDWB yielding 11.2 hrs.  Under what conditions (recorder, 25 mW, 50mW, or 100mW)?  Almost all of their current transmitters operate under high drain conditions where alkalines are not an ideal choice.  The one chart that is really useful is the SMQVs.

 

Even if a third party unofficial tester (friend of the company) provided data similar to the SMQV charts, it would clear up a lot of confusion about what is presented in the majority of their data sheets.  If I had access to all the models, I'd do it, and alternatively I'd be willing to pay $20 to $30 for the data since it makes a big difference in what model I would choose.

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22 hours ago, Constantin said:

Also try if in your setting you can get by on 30mW. That should definitely get you through the 6 hour mark

 

My understanding of the SMWB/SMDWB is that the transmission power no longer effects run time on the wide-band transmitters.

The transmission power is attenuated before the antennae, but the transmitter itself isn't running at variable power, per se.

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1 hour ago, gus harris said:

My understanding of the SMWB/SMDWB is that the transmission power no longer effects run time on the wide-band transmitters.

 


Ok, that’s possible, I don’t know. 
In that case, I would like to reiterate Larrys recommendation

 

On 12/7/2019 at 3:58 PM, LarryF said:

Try letting the transmitter run until it dies when you have some free time. That will give you more confidence in the use of NiMh.


Moreover, basically everything he wrote in this thread

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On 12/28/2019 at 4:12 PM, Constantin said:


It‘s not a battery test, it’s a transmitter test (for FCC and CE marking purposes), which apparently needs to be repeated with each battery type. 
And... perhaps... I should let Larry get this. 

 

Constantin nailed it: it is a complete retest of the transmitter. It is not just a "battery test". In a reasonable world, the manufacturer should be able to state that the operating parameters do not change due to highly regulated internal voltages. No such luck; bureaucracy wins out over common sense.

Best Regards,

Larry Fisher

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I was able to do some digging and came across a B&H first look video as part of their sales page for the SMDWBs.  Not sure if they did the testing themselves or were provided the info, but it looks like the SMDWBs get very similar battery life results to the SMQVs (Perhaps slightly better when they operate at 25mW compared to the SMQVs 50mW).

 

https://www.bhphotovideo.com/c/product/1367684-REG/lectrosonics_smdwba1_smdwb_dual_digital_hybrid.html

Click on the play button and then first look smdwb

 

If I do pick some up down the road, I'll try to do a test with some alkalines.

 

Thanks for all the replies to my inquiry about the battery life.  Eventually figured out which way I will go.

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  • 2 years later...

I get the high-pitched squeal sometimes. Turning off remote control has helped, but sometimes not. I see that you sometimes get it with lithium rechargeables, sometimes not, dependng on run times. Does it happen with other battery types?

 

Basically, I'm trying to come up with the answer to:

 

What are best practices for avoiding the high-pitched squeal?

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1 hour ago, mulluysavage said:

I get the high-pitched squeal sometimes. Turning off remote control has helped, but sometimes not. I see that you sometimes get it with lithium rechargeables, sometimes not, dependng on run times. Does it happen with other battery types?

 

Basically, I'm trying to come up with the answer to:

 

What are best practices for avoiding the high-pitched squeal?

Are you on the latest firmware that cured the 2.75khz whine? , the whine seemed mainly on dpa mics..stick to Nimh batts.. 

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1 hour ago, r.paterson said:

Are you on the latest firmware that cured the 2.75khz whine? , the whine seemed mainly on dpa mics..stick to Nimh batts.. 

 If turning off the remote control function helps solve the whine, then that is 100%, definite indication that you need the updated firmware for the transmitter, as suggested by Paterson.

Best Regards,

Larry Fisher

 

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