Any battery design experts here?

[gentlevoice]

Hello DIYs,

I'm interested in finding/or making batteries for audio purposes, however, would like to find somebody with specialist knowledge in the design of batteries to ask some questions, if possible....

Any battery experts here on diyaudio?

A Merry Christmas to you ...

Jesper

[lineup]

Hello.

I wonder if there is any idea to make your own batteries?
We can buy good battery, re-chargable or standard
of many different types.
Manufacturers can do this very much better than we can.

The only I can think of, is making your own batteries because it is interesting and fun to experiment.
They would most sure not be neither effective or reliable.

Regards

[gentlevoice]

Hi lineup,

Well, yes, it might be - but my experience is that often things going into production and aimed at the consumer has some built-in "protective" or other measures that ensures it will work in many different situations.

For this particular purpose I would like to build hopefully a very fast battery (high surge current capacity) with an inherently very low noise level, even under dynamic conditions. And a very, very low internal resistance.

But I would need to find a sensible path between necessary design features (that makes the battery work), and at the same time omitting features that are "excessive" and maybe compromises the performance of the battery.

So, that's why ....

Best from Jesper

[Pjotr]

Hi Jesper,

If you know how much effort is put into the development of batteries nowadays (because market demands) you wouldn’t dare of thinking making your own.

Have a look here: http://www.a123systems.com/ These batteries have a Ri in the order of mohms and can safely be discharged at a rate of 100C.

I have started my car with four of those 1.1 AH cells

[gentlevoice]

Hey Pjotr,

Thanks - looks very impressive! Yes, it is my impression that a lot of research is being invested in battery development....

I might have a somewhat special approach to this, though, and would like to investigate this further.... So, if anyone is an expert on the chemistries etc. of batteries ???

Thanks for your comments lineup & pjotr.

Best Jesper

[Hendrik]

Hi, just to give you an idea of what is needed to charge a battery:


1. NiMh batteries

-zero voltage slope: you monitor the battery voltage during charge. A battery is full when the slope of the voltage curve becomes zero. Charging current should be high enough. And, little unknown, but this voltage "profile" fades when batteries get older.

-Dt charging: you monitor the temperature of the battery pack. A fast rising temperature profile means the batteries are full. (They produce heat instead of accumulate charge) This works very well with charge currents down to 1/4C. No problem with battery ageing.

-Slow charging: 1/10C for 14h. Charging deep discharged batteries with this type of charger can be a real problem. Deep discharged batteries are unable to accumulate the charge. (specially some Chinese batteries.)

-Never deep discharge NiMh batteries. The cutoff voltage should be set according to the battery pack voltage. And not 1V/Cell.
-Impedance: very low.

2. Lead acid.

-Charging is easy, see for exemple the UC3906 or the UC3909 from TI.

Same warning here: never deep discharge.


-Li-Ion: I suggest not to experiment with this battery chemistry.


Battery noise: some people use batteries for there high end preamp. To bad, batteries produce some kind of cracking very low freq. noise.


There is much more to tell about batteries. I can write a few pages about it. But you better let me know what you need.

Regards,

Hendrik

[gentlevoice]

Thanks for your suggestions for charging different battery types.

You mention that you do not recommend experimenting with Li-ion batteries... Is there any reason for this?

And then you write that batteries make some kind of cracking low freq. noise. I've heard about this before but have never seen any measurements on this (e.g. FFTs or noise spectra). Do you know if somebody have measured this?

Basically what I'm interested in doing is something like a seawater cell that can be recharged. I'm looking for something that can be made from naturally available materials that have had a minimum of industrial processing. I've found seawater cells in many different primary cell versions but haven't found any secondary cells.

Audibly good sounding & low noise, very low internal resistance, fast reply to power demands & reasonable size are some of my criteria ...

Would you have any suggestions?

Happy New Year!

Jesper