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snowflake View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 12 January 2021 at 11:35am
the brazilians seem to have a crazy car audio scene culture

https://www.youtube.com/watch?v=dvktyZS7TKE



LOL

EDIT: think some of those are actually Paraguay not Brazil


Edited by snowflake - 12 January 2021 at 11:43am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 12 January 2021 at 2:28pm
batteries - a nominal 12V lithium battery will have slightly higher voltage than a lead-acid battery but they seem to be very expensive - about four times the price of lead-acid.

As most car amps accept voltage from 9V-15A/16A is there any sense in using two batteries in series to give 24V and then regulating that down to a stiff 15A so that the amp doesn't lose efficiency at high power due to voltage sag? If so how do you do that without wasting too much power?

EDIT: or three 6V batteries in series to give 18V. 6V batteries are reasonably common and don't cost a lot more than 12V battery of half the Ah rating.



Edited by snowflake - 12 January 2021 at 3:59pm
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bass*en*mass View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post Posted: 12 January 2021 at 7:31pm
lifepo4 doesnt cost that much more compared to the weight and usable energy stored imo.
its less than half the weight and size, at almost double the energy density.
voltage sag is not as bad/high current peaks less of a problem, power cap might not be required.

modern class d amps are about 80-90% efficient, dsp is cheap, the trick with 12v Systems is efficiency - moar, efficient, cabs, less power.. :)
(currently working on a 60/200/520ah lifepo4 based, solar powered ac/dc option to run parts of our stacks for different needs, "sustainably"..) :)


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Post Options Post Options   Thanks (0) Thanks(0)   Quote snowflake Quote  Post ReplyReply Direct Link To This Post Posted: 12 January 2021 at 9:20pm
Originally posted by bass*en*mass bass*en*mass wrote:

lifepo4 doesnt cost that much more compared to the weight and usable energy stored imo.
its less than half the weight and size, at almost double the energy density.
voltage sag is not as bad/high current peaks less of a problem, power cap might not be required.

modern class d amps are about 80-90% efficient, dsp is cheap, the trick with 12v Systems is efficiency - moar, efficient, cabs, less power.. :)
(currently working on a 60/200/520ah lifepo4 based, solar powered ac/dc option to run parts of our stacks for different needs, "sustainably"..) :)




have you got a link to some good LiPo? I don't seem to be finding much for the right price. would definitely like something lighter as two of those 8V lead ones are 58kg for 165Ah.

a lot of car amps are designed to run optimally with the alternator running 14.4V. running off a standalone battery you are losing a volts or two straight away.

maybe smoething like this will provide a stable 15V. better with a big cap on its output

800w high power step-down module constant voltage/current 30a 24v-70v to 3v-58v12v48v dc-dc buck power supply module Sale - Banggood.com-arrival notice


Edited by snowflake - 12 January 2021 at 9:21pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post Posted: 13 January 2021 at 4:00pm
CATL, Winston etc., reasonably good cells, are available at about 650€ for 200Ah 12v nominal, would require additional Balancer/BMS though, incl. bits n bobs max 30kg for about 2.5kwh
If you think about adding solar, which makes a lot of sense imho, they also take more charging current - more efficient use of the panel/s :)
I wouldnt worry too much about the 14.4v, lifepo4 is about 13.2v but much more stable than lead..
Its worth looking into the Amps efficiency imo, even the classD ones vary a lot. (75-90% iirc)




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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 13 January 2021 at 6:04pm
I built my own Lithium ion pack from cells and BMS, you have to be careful as everything is live when you assemble it, but its not hard.  That way you can have a higher voltage source which will allow you to use more powerful amps without a voltage conversion stage in between.  Sure electronics do boards that run off a single supply and are high power:

Doing it this way you avoid high idle losses due to things like boost converters and inverters you also have a much more energy dense power source.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote infrasound Quote  Post ReplyReply Direct Link To This Post Posted: 13 January 2021 at 7:19pm
Originally posted by kipman725 kipman725 wrote:

I built my own Lithium ion pack from cells and BMS, you have to be careful as everything is live when you assemble it, but its not hard.  That way you can have a higher voltage source which will allow you to use more powerful amps without a voltage conversion stage in between.  Sure electronics do boards that run off a single supply and are high power:

Doing it this way you avoid high idle losses due to things like boost converters and inverters you also have a much more energy dense power source.

174v! Wacko

Didn't realise tripaths went that high



Edited by infrasound - 13 January 2021 at 7:20pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post Posted: 13 January 2021 at 9:22pm
as always it all depends imo..
specially with battery powered systems efficiency is key imo - theres a target spl for `your`application and a limited amount of available power - ideally i`d use as many cabs as possible to raise efficiency first, to raise the runtime on given capacity/power..

Will do true rms metering soon, on both, ac and dc setups, recent rough tests showed that you wont need that much power to run 4/8 proper flh subs and 2/4 synergy tops at pretty decent levels :)

i do get the point of dedicated dc amps running off high V battery packs, theoretically those should offer the highest efficiency due to lowest losses in cables and conversions, but:
- chargers are rare and expensive, both ac and dc/solar?
- you`re limited to those few dedicated amps!
- ac inverters are scarce?
- proper, rated, distro (fuses, bms, shunt etc.) gets awkward as its an uncommon V?
- suitable dsps are scarce?

None of the above issues apply to usual/common 12V setups.
- lifepo4 optimized ac+dc/solar chargers are cheap and available in all `sizes`and budgets!
- 12v car amps would work fine, less fiddle, rather plug n play, (up to 90%+ efficient too afaik)!
- with proper ac inverters you could run your existing gear and the dj gear for shows where the dc options dont cut it/are limited, doing real shows/gigs without ac is almost impossible?
- 12v distro is common and cheap, despite the slightly larger cables required due to potentialy higher currents involved of course, other than that its straight forward.
- all required/available audio parts are cheaper imo as thats what the markets have adopted to, luckily.


our application/idea/intended use is quite special though, will share measurements/experiences asap!
Embarrassed






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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 13 January 2021 at 10:24pm
lots of electronics designed for mains use will also work from DC if it uses an SMPS so you could probably power a lot of equipment from a high voltage DC pack.  But please don't mess around with a high voltage DC pack if you don't know what your doing as shorts and electric shocks are more serious than AC due to the lack of zero crossing.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bass*en*mass Quote  Post ReplyReply Direct Link To This Post Posted: 13 January 2021 at 10:47pm
yeah, you could use a dedicated inverter per device, i am not sure its worth it though..
thanks for stating the risk/cautions with high voltage devices!
(we are working with 1500V solar systems so well aware of safety standards)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 14 January 2021 at 12:50pm
I meant that the normal AC power supply for a universal voltage range device (90 -240VAC) usualy just rectifies the mains and then has a flyback converter.  If you feed it DC 127 - 340V the flyback converter is under normal operating conditions.  The only change is that half the rectifier diodes are never conducting.  However you need to be able to identify the type of power supply the device is using and possibly change components like the power switch and fusing to make it DC compatible.  A lot of audio equipment (like cheaper DJ mixers and audio interfaces) uses a plugin wall AC transformer and this will just be destroyed by connecting DC across it.  I did modify a Numark mixer that used a plugin wall transformer to to be DC powered but this involved changing 3 power supplies inside the unit.

My Packs only 16S but I didn't have any problems getting a wall charger from Aliexpress.  

Protection and mechanical switching in DC systems is much more difficult due to the the lack of zero crossing not extinguishing arcs (Important not to pull apart connectors under load).  Its important to use DC circuit breakers rated for sufficiently high voltage throughout the system to turn things off in case of fault as simply 'unplugging' could burn you quite badly in the case of a high current fault.

So with higher voltage packs you gain a lot of potential performance (peoples minds are pretty blown when they realize I can run all weekend off such a small setup) but as others have said its more expensive and costly.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kipman725 Quote  Post ReplyReply Direct Link To This Post Posted: 14 January 2021 at 12:52pm
I forgot I did write some notes for some friends on my setup:

obviously in hindsight there is a lot I would do differently!

I'm working on a 8*500W (4 ohm) DSP amplifier that's designed to be battery compatible to replace the electronics in that document.

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