NiMH 9v cells & charger recommendations?

[archimedes]

I've been switching over to NiMH rechargeable batteries as much as possible, and have had great results with Eneloops and the Maha-9000 charger (both largely based on advice found on this forum).

I was wondering what would be the best options for 9v batteries, though. I don't think Sanyo makes a 9v-LSD cell and the Maha chargers appear to only be set up to accept cylindrical rechargeables.

I have seen various other brands of NiMH 9v cells and chargers, but don't know what might offer the best reliability and performance. Since these are rechargeable, cost is not a huge concern (ie, willing to pay more for quality).

Thanks for any info and advice!

 

[moldyoldy]

The Maha MH-C490F 9v charger has been reliable in constant use at the church I support. Only one charger failed over the course of maybe 5 years in that service. The Maha MH-C490F 9v charger is a smart charger and will handle all varieties of nominal 9V batteries of which the church has many. In particular, the Maha MH-C400F accomodates both the 9V batteries that operate at less than 9V (8.4v) and those that operate at almost 10V (9.6v).

If you have devices that need at least 9V for operation, then I recommend the Maha version for 9.6v. For example, the advantage is that a wireless mike transmit signal is higher with the 9.6v batteries as opposed to the 8.4v batteries - and that overrides a lot of local interference, like a State Patrol radio tower visible from the church.

Note that many advertisements do not indicate what the actual voltage output under load is for the offered "9 volt" batteries. if no definition is provided, then assume the actual operating voltage is about 8.4-8.6 volts.

I have no experience with any of the 9v low-self-discharge batteries. the previous Maha 9.6v batteries have been too reliable - although they do wear out - still almost a dozen in reserve.

There are some long threads on the subject in CPF.

Moldyoldy

 

[archimedes]

I will look for the Maha 9v charger and cells, which I hadn't seen before.

Thanks very much for the information.

 

[Mr Happy]

Many people advise that one should avoid NiMH rechargeables in the 9 V size. The cells are low in capacity and fail quickly due to the internal configuration of several cells in series.

Though I have no direct experience of them, some people with audio applications have recommended the lithium ion kind of 9 V rechargeable, of which one example is here for info: http://www.batteryjunction.com/9v-lithium.html

These have the advantage of twice the capacity and more charge cycles without failing.

 

[moldyoldy]

Regarding the implied question of where to purchase the Maha chargers and 9.6v batteries, many CPF'ers use http://www.thomasdistributing.com/, however there are other sites that sell this combination.

Regarding practical runtime on the 9.6v batteries, each pastor uses one Maha 9.6v battery for each service, after which the battery is placed on charge and another battery is used. Since the wireless mikes have a power switch as well as an audio mike switch, the actual powered time is about 2 hours. No case of one of the Maha 9.6v batteries running down during an event has been reported, nor have I been present for such an event. Based on my initial testing and casual observation of how fast the batteries reached full charge, there was probably another hour of runtime available - caveat regarding the current draw on any wireless mike.

As for the Lithium Polymer or Lithium Ion 9v batteries, the site referenced above indicates that the working voltage is 8.4v or less. That is too low for our site which needs the higher voltage from the Maha 9.6v batteries to overcome the State Patrol radio tower transmissions. It is more than disturbing to have an encrypted police transmission break up a homily/sermon or speech. Since we started using the 9.6v cells years ago, no radio interference disturbances have been heard. I have been told that the 9.6v cells provide some significant "oomp" to the paintball guns, although as ex-mil, I will have nothing to do with any paint-ball games!

a moldyoldy.

 

[moldyoldy]

fyi: regarding battery failure, the church recycles the Maha 9.6v batteries when the Maha charger rejects them - blinking - because of a high internal resistance. Nevertheless, no Maha 9.6v battery has run down during a service, even when that battery was later rejected by the charger.

and yes, the church did have prior cases of "9v" batteries running down during services - those operated at 8.4v and less.

 

[VidPro]

the variations are much bigger than before, like some of the things that Moldy was saying.
there is ni-mh in slightly lower votlage, and higher capacity, and ni-mh in slightly higher voltages and lower overall capacity. one cell difference in voltage.

also there is the li-ion 2x3.6v cell, that working voltage is from ~8.4v- ~6.6V which is the lowest voltage of them all.
and there is the 3X ~3.0v cells using li-fe type technology which has a good voltage but back to poor capacity.
both of them are acting very low self discharge too, if that was the need.

if you get any of them it would be really good to have the voltage RANGE of the item your thinking of stuffing it into, many 9V operating stuff can suck a alakline battery down to near nothing , and will work with the lower voltages. some people were happier the 9.6V nominal type of ni-mh cell item for thier devices they wanted to run hard and fast. i think it was for some toy car.

and so far i cannot RELY on any of them 100%. unlike mouldy with a pastor, 2 hour time limits, and a bunch of forgiving people :-) who donate money to the cause.
My stuff has to stay up for longer than 5 hours , and if something goes wrong, they get to Replay the screwed up audio on the dvd for hundreds of times and want thier $$$ money back. and DJs get away with some pretty horrible wireless transmissions too, that are no big deal till you try and record it with a microphone , not just putting it over a "PA" system.

for a few small toy devices i have used the li-ion 2x3.6v 400ma thing and , at Least it is rechargable, and i dont have to worry about it holding out over time, as it has been low self discharge . because the device regulates and probably cheaply regulates (tosses power) the capacity was great, the voltage was not so nessisary.
right now i only charge them manually, as most of the 9V chargers i have are just slow run-on style like 25ma forever things.

 

[moldyoldy]

5 hour run time requirement? uf-da! The pastors have made it thru a 3 hour session before with no particular problem, but I am not sure what I would try with a 5 hour requirement.

We have several wireless mikes types and the battery current draw is noticeably different between them. The later models seem to have a lower current draw with no obvious loss of radiated power. However, all of them vary in how tolerant they are of lowered voltages - lower than the supposed 9.0 volt standard. Like VidPro said - some 9v battery systems are battery vampires, then some are quite intolerant of even 8.8v. and no, I did not choose any of those systems. The system I chose for wedding photography to wire the groom worked quite well.

If the main wireless mike power section can be hidden, then I might try paralleling 2 9V rechargeable batteries with known reliability in a fake power-pack and taping that to the power section. That is also too complicated for these pastors. Or simply switch to a lead-acid gel-cel battery like I used for another performer for his speaker system intended to be set up anywhere w/o regard for AC power - then figure out where to hide it.

Otherwise, I agree - I do not know of any 9V rechargeable battery system within the size dimensions of the accepted 9V battery that will run a wireless mike for 5 hours with any sort of a reserve. Maybe the 9v Lithium batteries might have a chance - and then toss them after each session. Expensive.

 

[Mr Happy]

Remember that the standard voltage of a 9 V alkaline battery is from 9 V down to 5.4 V, due to the discharge curve of an alkaline manganese cell. Any device which is intolerant of 8.8 V is a defective device, there is no other way to say it. Some devices might be forgiven for having a low battery warning at 7 V, but not 8 V. Also the radiated power of a wireless mike might depend not only on the apparent voltage of a cell, but the ability to sustain voltage under load. In that regard it is possible that a high power, low resistance battery like LiPo might perform better than alkaline or NiMH.