Remember that batteries generates some noise and you have also to decouple them. Personally I think batteries only adds work in charging and they last 8-10 years or 1000 recharges (3 years is you charge them every day) if you treat them OK. I think noone can answer you which types they think are the best but big NiMH is expensivepercy said:
Maintancefree Lead-Acid would I choose.percy said:
Well, ignoring cost, there are a few good reasons. NiMH are not good at delivering large current spikes. They'll supply their rated power just fine, but if you have something that occasionally requires large amounts of current on demand, they won't perform as well as other options (fixable with a bank of caps, I guess) . They also overheat easily, so don't plan to drain them and recharge them constantly without consequences.
NiCds can deliver large current spikes better, but typically overall capacity is lower. Cost being no object, I guess you could probably fix that, but they are also more picky about how you charge them. They perform best when fully discharged and then recharged. A work around is to just leave the amp on when you're not using it, so it completely discharges, and then recharges and is ready to go. Seems like a pain to me.
Lead Acid batteries are easy to find for low cost, high capacity, high instantaneous discharge and easily implemented off-the-shelf chargers.
I've never really used any other chemistries (except lithium, but they don't really have the ratings for this type of stuff), so I can't comment on them, but lead acid batteries are the best for all the practicality reasons you're ignoring, and ultimately, will give you the best performance with the smallest amount of additional work.
If you want to spend the money and put the work into it, I think you could eventually get the same results with any battery.
Narcisse91 said:
That problem is much more typical of the alkaline batteries.
I wouldn't say that's typical of NiMH batteries.
Just ask someone with photography experience how many seconds a dedicated flash takes to recharge with a brand new set of alkalines, or with NiCD or NiMH.
On my Canon flash it takes 3~4 seconds with alkalines, much less than a second with NiCd or NiMH.
It's fun to shoot 4 pics in one second, always with flash. People stare at you.
Courtesy Canon T90.
carlosfm,
Alkalines may be worse, but NiMHs are worse than NiCds. That was my point. I wasn't trying to say they were the worst option in that regard out of everything. Honestly, I've never played with Alkaline rechargables...
peranders,
Generally speaking, the Ah rating has nothing to do with how much current a battery can deliver quickly, in a current spike condition. The higher Ah ratings can be indicative of what the peak current available for a short period of time may be, but there are other characteristics of the battery that will have a huge impact on how quickly current can be pulled out of the battery.
Alkalines may be worse, but NiMHs are worse than NiCds. That was my point. I wasn't trying to say they were the worst option in that regard out of everything. Honestly, I've never played with Alkaline rechargables...
peranders,
Generally speaking, the Ah rating has nothing to do with how much current a battery can deliver quickly, in a current spike condition. The higher Ah ratings can be indicative of what the peak current available for a short period of time may be, but there are other characteristics of the battery that will have a huge impact on how quickly current can be pulled out of the battery.
I googled up some links which confirm what is being said here.
Between the 'new' technology batteries alkalines seems to be the worst, followed by Li-ion and then NiCd.
http://www.buchmann.ca/Article9-Page1.asp
http://www.buchmann.ca/Article11-Page1.asp
Sounds like the NiCds have impedance in the range of 75-150miliohms, whereas lead acids are as low as 1miliohm or less.
www.telepower.com.au/INT94d.PDF
It seems like in the battery world they define/measure impedance in two ways. Some say impedance is a measure of drop in voltage for given a current demand - which I'd imagine is the equivalent of "reserve power" of power supplies that we sometimes refer to. and some measure impedance based on frequency also. They run a sweep in a frequency range and see how the battery impedance changes.
http://www.powerdesigners.com/InfoWeb/design_center/Appnotes_Archive/A2615.shtm
Between the 'new' technology batteries alkalines seems to be the worst, followed by Li-ion and then NiCd.
http://www.buchmann.ca/Article9-Page1.asp
http://www.buchmann.ca/Article11-Page1.asp
Sounds like the NiCds have impedance in the range of 75-150miliohms, whereas lead acids are as low as 1miliohm or less.
www.telepower.com.au/INT94d.PDF
It seems like in the battery world they define/measure impedance in two ways. Some say impedance is a measure of drop in voltage for given a current demand - which I'd imagine is the equivalent of "reserve power" of power supplies that we sometimes refer to. and some measure impedance based on frequency also. They run a sweep in a frequency range and see how the battery impedance changes.
http://www.powerdesigners.com/InfoWeb/design_center/Appnotes_Archive/A2615.shtm
A 1Ah has the ability to deliver 1A of current for 1 hour before it is out of charge. A 500Ah can deliver 500A for 1 hour. That's all that rating means, and it has no official relation to an instantaneous current demand.
If the output impedance (which can be rated different ways, depending on the battery and the market) is significantly higher on the 500A battery, there is a possibility it won't be able to deliver as much instantaneous peak current. Of course, in real life we're not going to be comparing a 1Ah to a 500Ah, are we? If you stick to real life examples, like 5Ah to 8Ah, or even 5Ah to 5Ah, maybe that will be clearer.
Here is an example. I have a 16Ah battery in one of my cars. It starts the car without a problem every time.
I can also take a pile of 2000mAh AA NiMH batteries. Take 80 of them, put them in 8 parallel columns of 10. You will have 16Ah at 12V. I would not want to rely on that to start my car on a cold morning. Note that 72 of those batteries are only there to get 12V, current supply is limited to what the 8 parallel batteries can handle.
Try it for yourself.
Actually, you can just go to the local auto parts store and shop for car batteries. You will find 12V batteries with CA and CCA ratings. CCA is based on peak current delivery (starting the car) and CA is based on continuous. The fact that these two things are rated independantly and marked on batteries should be enough of a hint that they are not 1:1 with each other. But if you start making note of the different values, eventually you will find a couple batteries where CA is the same, and CCA is higher or lower. Or where CCA is the same and CA is higher or lower.
If you don't like the car example, since it is dealing with batteries that are typically rated in cranking amps and cold cranking amps, flip over the RC car world where you'll find NiMH and NiCds mainly.
If the output impedance (which can be rated different ways, depending on the battery and the market) is significantly higher on the 500A battery, there is a possibility it won't be able to deliver as much instantaneous peak current. Of course, in real life we're not going to be comparing a 1Ah to a 500Ah, are we? If you stick to real life examples, like 5Ah to 8Ah, or even 5Ah to 5Ah, maybe that will be clearer.
Here is an example. I have a 16Ah battery in one of my cars. It starts the car without a problem every time.
I can also take a pile of 2000mAh AA NiMH batteries. Take 80 of them, put them in 8 parallel columns of 10. You will have 16Ah at 12V. I would not want to rely on that to start my car on a cold morning. Note that 72 of those batteries are only there to get 12V, current supply is limited to what the 8 parallel batteries can handle.
Try it for yourself.
Actually, you can just go to the local auto parts store and shop for car batteries. You will find 12V batteries with CA and CCA ratings. CCA is based on peak current delivery (starting the car) and CA is based on continuous. The fact that these two things are rated independantly and marked on batteries should be enough of a hint that they are not 1:1 with each other. But if you start making note of the different values, eventually you will find a couple batteries where CA is the same, and CCA is higher or lower. Or where CCA is the same and CA is higher or lower.
If you don't like the car example, since it is dealing with batteries that are typically rated in cranking amps and cold cranking amps, flip over the RC car world where you'll find NiMH and NiCds mainly.
I think it's agreed that some form of lead acid battery is the best choice. Of the SLI's (starting-lighting-ignition) the two modern varients, AGM and Gel have some great advantages in DOD (degree of discharge).
Discharge to a standard lead-acid to a 50% discharge leads to accelerated sulfation and ultimate failure. The AGM & Gel do not have this fault and can be deeply discharged without detrimental long term effects. This would translate into long music sessions with less frequent recharge cycles.
I switched to gels 6 years ago for my sailboat. We frequently discharge to 10.5VDC (XM radio stops at 10.5V) whilst the radio is playing and instuments are on. This is about an 8 hour life.
This type of abuse would play he!! with a lead-acid leading to that 2-3 year life you spoke of PA. The AGM's and Gels can be beaten like a red-headed-step-child.
Just my two cents...
PS... somewhere on the net I read an interesting technical article on batteries for audio. I have been unable to find it. I thought it may be on Rod's website or Nuuk's. Anyway, the conclusion was NOT NiCad or Lithium Ion. It was a choice between alk's and lead acids.
Peace/Out
Discharge to a standard lead-acid to a 50% discharge leads to accelerated sulfation and ultimate failure. The AGM & Gel do not have this fault and can be deeply discharged without detrimental long term effects. This would translate into long music sessions with less frequent recharge cycles.
I switched to gels 6 years ago for my sailboat. We frequently discharge to 10.5VDC (XM radio stops at 10.5V) whilst the radio is playing and instuments are on. This is about an 8 hour life.
This type of abuse would play he!! with a lead-acid leading to that 2-3 year life you spoke of PA. The AGM's and Gels can be beaten like a red-headed-step-child.
Just my two cents...
PS... somewhere on the net I read an interesting technical article on batteries for audio. I have been unable to find it. I thought it may be on Rod's website or Nuuk's. Anyway, the conclusion was NOT NiCad or Lithium Ion. It was a choice between alk's and lead acids.
Peace/Out
There was an article on tnt-audio
I use Lithium batteries in hand held products for space reasons. Li- ion and polys are very fussy about charging and don't like being stacked in series, look how quickly laptop batteries lose capacity.
Lead acid is the easiest technology to use, but the gel variety is best. I suspect the gas bubbles formed during charging might cause electrical noise as thheir presence must affect the series impedance.
I use Lithium batteries in hand held products for space reasons. Li- ion and polys are very fussy about charging and don't like being stacked in series, look how quickly laptop batteries lose capacity.
Lead acid is the easiest technology to use, but the gel variety is best. I suspect the gas bubbles formed during charging might cause electrical noise as thheir presence must affect the series impedance.
Actually,that's not quite correct.
The AH ratings of batteries is based on a 20-hour rate.
A 20AH battery could deliver 1A,for 20 hours.
It would NOT support a 20A load for 1 hour,it would be much shorter than that,probably closer to 30 minutes.
The relationship is NOT linear.
Take the AH rating,divide it by 20,and that's the "rated" load current,for a 20 hour discharge curve.
I think the truth is that not many use batteries mostly because it's wearing out. If cost is of no object why conctrentrating yourself on a Gainclone in the first place?percy said:
My suggestion: Use four maintanance free car batteries = 2 x 24 v DC
About current: A LM3886 can deliver max 10-12 A and this is not much for a car battery.
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