Hi All,
I have inherited two massive LIFE PO4 batteries in nice alloy cases (30Kg each and approx £1,100 RRP each!) they are 48 volt / 150 Amp Hours rated and would like to use them as the power supplies and physical bases for a pair of floor standing active monitors.
Each 3 way monitor stack has three separate monoblock 500 watt class D amps and 3 channels of DAC per speaker, so 6 channels amps and dacs in total.
The 6 Ohm bass section is 95dB per watt @ 1 meter.
The 8 Ohm mids are 100dB and the TPL tweeter is 100dB sensitivity.
DAC's and A to D are built into the amps and the only input is an optical Toslink (no electrical connection with the music server / DSP)
I want to run the whole system from the batteries and use DC to DC voltage/current reduction for the amplifier boards and DAC's.
Questions:
What is the best approach or technique to achieve DC to DC reduction in this situation and any company or product component recommendations would be much appreciated!
Highest audio quality is my goal and I don't want to waste these super expensive batteries by scrimping on the DC reduction.
Thanks in advance
Alex.
I have inherited two massive LIFE PO4 batteries in nice alloy cases (30Kg each and approx £1,100 RRP each!) they are 48 volt / 150 Amp Hours rated and would like to use them as the power supplies and physical bases for a pair of floor standing active monitors.
Each 3 way monitor stack has three separate monoblock 500 watt class D amps and 3 channels of DAC per speaker, so 6 channels amps and dacs in total.
The 6 Ohm bass section is 95dB per watt @ 1 meter.
The 8 Ohm mids are 100dB and the TPL tweeter is 100dB sensitivity.
DAC's and A to D are built into the amps and the only input is an optical Toslink (no electrical connection with the music server / DSP)
I want to run the whole system from the batteries and use DC to DC voltage/current reduction for the amplifier boards and DAC's.
Questions:
What is the best approach or technique to achieve DC to DC reduction in this situation and any company or product component recommendations would be much appreciated!
Highest audio quality is my goal and I don't want to waste these super expensive batteries by scrimping on the DC reduction.
Thanks in advance
Alex.
Hi ... before possibly commenting more on your questions can I ask if you have a charger for the batteries (& what it is?)?
Also, what the voltages for the different electronics' sections are?
Cheers,
Jesper
Also, what the voltages for the different electronics' sections are?
Cheers,
Jesper
Hi Jesper,
Yes I have two fast chargers (240 volts) rated at 10 Amps, everything is still in the crates so I cant access them to see the small print on the underside.
My amps require plus/minus 48 volts DC power supply for up to 500 watts into 4 Ohms and 250 watts into 8 Ohms.
The DAC's need an input of 12 volts then they have all the requisite voltage reduction/distribution on the boards.
I am really just looking for general advice on the best ( sound quality) method to implement voltage reduction... I dont care about efficiency as I have such an insane excess of battery power available.
Once I have established the best method and possibly some components/brand names, I will subcontract the work out to a skilled electrical engineer.
Thanks again for your help.
Cheers
Alex.
Yes I have two fast chargers (240 volts) rated at 10 Amps, everything is still in the crates so I cant access them to see the small print on the underside.
My amps require plus/minus 48 volts DC power supply for up to 500 watts into 4 Ohms and 250 watts into 8 Ohms.
The DAC's need an input of 12 volts then they have all the requisite voltage reduction/distribution on the boards.
I am really just looking for general advice on the best ( sound quality) method to implement voltage reduction... I dont care about efficiency as I have such an insane excess of battery power available.
Once I have established the best method and possibly some components/brand names, I will subcontract the work out to a skilled electrical engineer.
Thanks again for your help.
Cheers
Alex.
PS, the amps were using a 60 volt DC supply from a switch-mode power supply and this increased the power output a fair bit.
I am happy with 48 volts in to get the 300 to 500 watts depending on speaker driver impedance.
I am happy with 48 volts in to get the 300 to 500 watts depending on speaker driver impedance.
Perhaps there's a chip amp for the +12V DAC supply, that meets the criteria -
- Can handle 48V DC input
- Can dissipate the power, with proper heatsinking, in a 36V drop, for whatever current the DACS take
- Is stable at low gains.
Thinking of using it as an op-amp, setting its output voltage to a static 12V. That should provide a pretty solid rail with shunt regulation. I'm sure there's a good low noise voltage reference available to use with it at a minimum gain.
Be careful with the monster batteries; I'm reminded how some people used to charge such technology in a bucket of sand out in the garage.
- Can handle 48V DC input
- Can dissipate the power, with proper heatsinking, in a 36V drop, for whatever current the DACS take
- Is stable at low gains.
Thinking of using it as an op-amp, setting its output voltage to a static 12V. That should provide a pretty solid rail with shunt regulation. I'm sure there's a good low noise voltage reference available to use with it at a minimum gain.
Be careful with the monster batteries; I'm reminded how some people used to charge such technology in a bucket of sand out in the garage.
Hi Alex ... ok, thanks for the information. So a couple of comments:
* First I would make sure that the amps will be fine with being supplied from batteries and not the power supplies they are normally supplied from. Some amps - e.g. some of hypex' amps - to my memory do not work well with batteries.
* Secondly, given that you have two separate chargers, I reckon that the batteries are surrounded by some additional circuitry - over-charge protection, other safety protection etc. If it were me I would try to get a schematic on this circuitry so as to assess to which extent this additional circuitry may influence the batteries's basic qualities (low noise, high power delivery capacity, etc.). In this context you may observe that LiFePO4 batteries in my experience need over-charge protection on EACH cell as they tend to get imbalanced almost immediately.
* Third, batteries do NOT like to be in a hot environment. To my memory the lifespan of a typical battery doubles for every ten degree C decrease.
* Fourth, again if it were me, I would consider splitting the battery packs so as to be able to more or less supply each individual amp/DAC from its own batteries. Given the wattage rating I reckon that more batteries are paralleled. This may not be a simple process, though.
* Fifth - I would consider using linear regulators to down-regulate the voltages for the DACs but not for the power amps (see also point 1). The main issue here could be the high voltages as most regulators are less well with input voltages above ~35 volts. Another option would be to make a discrete linear regulator - I reckon other people here may have a specific idea about this.
* Sixth I would consider float charging the batteries so that the (new low-noise) chargers were always on. This would omit voltage fluctuations due to chargers switching on & off and for LiFePO4s in my experience a constant voltage of 3.4 volts is suitable. This may require some other way to switch off the amps and DACs - maybe there's a power down option?
These are my rather general remarks on how I would approach such a project. A bit of warning though: it could be somewhat comprehensive (again in my experience) 😉
Cheers,
Jesper
* First I would make sure that the amps will be fine with being supplied from batteries and not the power supplies they are normally supplied from. Some amps - e.g. some of hypex' amps - to my memory do not work well with batteries.
* Secondly, given that you have two separate chargers, I reckon that the batteries are surrounded by some additional circuitry - over-charge protection, other safety protection etc. If it were me I would try to get a schematic on this circuitry so as to assess to which extent this additional circuitry may influence the batteries's basic qualities (low noise, high power delivery capacity, etc.). In this context you may observe that LiFePO4 batteries in my experience need over-charge protection on EACH cell as they tend to get imbalanced almost immediately.
* Third, batteries do NOT like to be in a hot environment. To my memory the lifespan of a typical battery doubles for every ten degree C decrease.
* Fourth, again if it were me, I would consider splitting the battery packs so as to be able to more or less supply each individual amp/DAC from its own batteries. Given the wattage rating I reckon that more batteries are paralleled. This may not be a simple process, though.
* Fifth - I would consider using linear regulators to down-regulate the voltages for the DACs but not for the power amps (see also point 1). The main issue here could be the high voltages as most regulators are less well with input voltages above ~35 volts. Another option would be to make a discrete linear regulator - I reckon other people here may have a specific idea about this.
* Sixth I would consider float charging the batteries so that the (new low-noise) chargers were always on. This would omit voltage fluctuations due to chargers switching on & off and for LiFePO4s in my experience a constant voltage of 3.4 volts is suitable. This may require some other way to switch off the amps and DACs - maybe there's a power down option?
These are my rather general remarks on how I would approach such a project. A bit of warning though: it could be somewhat comprehensive (again in my experience) 😉
Cheers,
Jesper
Thanks Jesper,
That's exactly the type of advice/reassurance I was needing... Basically just general ideas and comments I can research and either tick off the list or adopt as the way to go.
I have lots of time as the Covid 19 delays in work mean I won't even be unpacking the crates for 6 months!
I think I will look around for class A/B amp boards that need are better suited to 48 volt batteries.
The (unknown) Chinees Class D amps in the crates worry me... I have used Hypex in the past and ended up selling them and buying a pair of Ebay'd Dave Belles class A/B... They were so much better.
That's exactly the type of advice/reassurance I was needing... Basically just general ideas and comments I can research and either tick off the list or adopt as the way to go.
I have lots of time as the Covid 19 delays in work mean I won't even be unpacking the crates for 6 months!
I think I will look around for class A/B amp boards that need are better suited to 48 volt batteries.
The (unknown) Chinees Class D amps in the crates worry me... I have used Hypex in the past and ended up selling them and buying a pair of Ebay'd Dave Belles class A/B... They were so much better.
Hi Jo,
Thanks also, I have lots of heatsink surface area available: approx 900mm tall, 300mm wide and 75mm deep fins on the back of each speaker.
The batteries each have a separate Battery Management System (BMS),I havnt opened them all up yet but they say the batteries are "immune to over / under charging, electrical surges or failure in the mains"
They also say the batteries retain 90% capacity even after 2,500 charge / recharge / and up to 75% after 6,000 charges.
They are fully contained in machined alloy cases, the cases look great!
Thanks also, I have lots of heatsink surface area available: approx 900mm tall, 300mm wide and 75mm deep fins on the back of each speaker.
The batteries each have a separate Battery Management System (BMS),I havnt opened them all up yet but they say the batteries are "immune to over / under charging, electrical surges or failure in the mains"
They also say the batteries retain 90% capacity even after 2,500 charge / recharge / and up to 75% after 6,000 charges.
They are fully contained in machined alloy cases, the cases look great!
Hi Alex ... you are welcome - good luck with your endeavours here ;-)
In general battery life is dependent on several factors and one of them is discharge rate, i.e. the deeper the discharge "per discharge" the shorter the lifespan. Also, ripple on the charging voltage may affect lifespan. The A123 LiFePO4 batteries I have I have now used for 5-6 years with float charging, and they appear to be fine. Low temperatures, no discharge, highly regulated low-noise charger.
Jesper
In general battery life is dependent on several factors and one of them is discharge rate, i.e. the deeper the discharge "per discharge" the shorter the lifespan. Also, ripple on the charging voltage may affect lifespan. The A123 LiFePO4 batteries I have I have now used for 5-6 years with float charging, and they appear to be fine. Low temperatures, no discharge, highly regulated low-noise charger.
I hope it will be ok that I make this remark: I once built a Class A amplifier where I placed the SLA batteries (series connected 12V/7 AH) right under the amplifier board. And I mean right under the board - 7 cm solid copper wires directly to the output transistors. The amplifier sounded outstanding ... this is to say that, again if it were me, I would consider the system's context so as to place the batteries close to where they are actually needed. My two cents.
Jesper
As the batteries come in high-quality alloy cases I am planning to use them for a base for each loudspeaker stack, so the power supply leads would be very short, maybe 30cm or so.
Thanks again and all the very best.
A.
Thanks again and all the very best.
A.
These are not lead acid batteries, it's not desirable or necessary to float charge LiFePO4, let the dedicated BMS handle all the charging and discharging mechanisms.
These appear to be telecommunications equipment backup batteries and that's a lot of stored energy to be kept inside your home, normally these batteries would be stored in their own room inside a telecommunications facility.
There will be suitable dc-dc convertors available from companies selling telecommunications power supplies as most equipment operates from 48vdc, these types of dc to dc convertors typically convert from 48v to 36v, 48v to 24v and 48v to 12v.
I find it a bit strange to use batteries to improve audio quality whilst at the same time introduce switch mode dc to dc convertors, I would just dispense with the batteries and find a suitable high quality low noise power supply, but each to their own.
Thanks Indiglo,
The batteries were designed for back up power for intensive care military field hospital, they had solar panels for charging but I didn't have room for them!
I don't want to use "off the shelf" DC to DC reduction as hey have the dreaded switch mode supplies on board... I am looking for voltage reduction that does not use switch mode supplies.
I read about a resistive ladder network that dropped voltages from 48 volts to 24 volts so hoping to find the best quaility components and most reliable construction to acomplish this.
I have seen an old (1980's) analogue tape machine in a recording studio and its power supply failed so they were using 4 stacked car batteries to produce 48 volts DC in... The onboard passive components then dropped and split up the voltage down to various levels.... It can be done!
The batteries were designed for back up power for intensive care military field hospital, they had solar panels for charging but I didn't have room for them!
I don't want to use "off the shelf" DC to DC reduction as hey have the dreaded switch mode supplies on board... I am looking for voltage reduction that does not use switch mode supplies.
I read about a resistive ladder network that dropped voltages from 48 volts to 24 volts so hoping to find the best quaility components and most reliable construction to acomplish this.
I have seen an old (1980's) analogue tape machine in a recording studio and its power supply failed so they were using 4 stacked car batteries to produce 48 volts DC in... The onboard passive components then dropped and split up the voltage down to various levels.... It can be done!
PS That tape machine fed its signal into a massive stack of "Emegring" DAC's and was used to archive precious master tapes... The sound from that old tape machine was beautiful!
The only downside to a resistive ladder arrangement is the power loss in heat, there will be a 24volt drop times the current draw of your amplifiers, for example 24volt drop across the resistive ladder x 5 amps (amplifier current draw) will equal 120watts heat dissipation from the resistive ladder.
A switch mode dc to dc convertor will be more efficient typically 80% or more. A commercially available convertor will meet EMI standards so will be low noise compared to a cheap no-name type from e-bay.
I guess you'll have to pick your poison.
A switch mode dc to dc convertor will be more efficient typically 80% or more. A commercially available convertor will meet EMI standards so will be low noise compared to a cheap no-name type from e-bay.
I guess you'll have to pick your poison.
Thanks Indiglo,
I am starting to google around and looking forward to finding the best solution, thanks also to everyone who has posted their ideas.
Cheers
Alex.
I am starting to google around and looking forward to finding the best solution, thanks also to everyone who has posted their ideas.
Cheers
Alex.
... hi again ... just a brief comment ... resistive ladders would also void one of the key qualities of batteries (besides low noise) which is their low internal impedance.
And IMHO DC to DC converters most often are so noisy that the fine noise specs from the battery essentially will have no importance.
Cheers,
Jesper
And IMHO DC to DC converters most often are so noisy that the fine noise specs from the battery essentially will have no importance.
Cheers,
Jesper