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LiFePO4 storage

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slaz View Drop Down
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    Posted: 20 August 2021 at 11:29am
Mornin' all .... long time no post.

Well since I last posted on here, I've added significantly to my "main" setup.
It now consists of

2 x FBT Maxx4 (passive 4R version)
1 x Pioneer GM-D8704
2 x Ultramax 12v 50AH LiFePO4 batteries
1 x Berry 302USB baby mixer powered by a phone-type power bank inmto USB.

Now this all rocks, tried and tested 3 times now with over 50 peeps around - and including peeps picking up the mic and some singalong and mic chatting etc. Well pleased with it. There's obviously no serious bass, but (in the outdoor context) it works very well and sounds lovely and clean, with good overload margin on the mic.

I'll get around to put up some pics etc some day ....

But - in the meantime ... the "season" is gonna end soon, and I'm keen on keeping those LiFePO4 batteries in good nick over the winter when they likely ain't gonna get used at all.
Now I'm thoroughly converted/convinced to this type of battery ...

The much flatter voltage discharge curve (than lead-acid) is great, but it also makes it more dificult to assess the charge-state from the off-load voltage. So - anyone have experience of how to assess the charge-state ? Would like to keep em at arouind 50% or so.

TIA.
REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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slaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 20 August 2021 at 4:25pm
Just found a pic I took a while back of my implemetation of the Pioneer 8704 amp.


Maybe ita a bit cock-a-mamy, but I wanted to broadly make it (kind of) modular system orientated, rather than put all the electronics in one box/enclosure.

Now "1/4" jack outputs ? Really ? " I hear you say ....  well I decided speakons are a bit too bulky, and not good for mounting in angle ally. Also, I already had some really good quality, long 1/4" jack <-> speakon cables for the FBTs. I use those same cables to hook the FBTs to an old Matrix mains amplifier I have ... also with 1/4" jack o/p's.

I thought the voltmeter was a good idea (well I still do) ... but for anyone else wanting similar, I'd say don't use those miniature voltmeters (like I did) ... they're CRAP. Nowhere near accurate, and also slow, and the lead-out wires are super delicate. Nasty. The bigger ones are mostly better - and I'll get around to replacing miniatutre one eventually.

The idea of the chocolate block is to act a bit like a patch panel - cater for different speaker configs, bridged/non-bridged etc.

Oh yeah ...  a bit more about the 1/4" sockets. I initially mounted the jack sockets directly to the angle ally -  but luckily (i.e. BEFORE I connected anything up to em or swiched on) I was reading the setup manual for the amplifier, and came across the bit about "do NOT short speaker grounds together" - so we cut strips of perspex, drilled out holes for the socjets, and found some rubber O-rings to go over the outside threaded parts of the jack sockets to isolate from the angle ally. Its a thorough solution. So DON'T make the mistake I very nearly did .... major danger of magic smoke escaping methinks !



Edited by slaz - 20 August 2021 at 4:39pm
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studio45 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote studio45 Quote  Post ReplyReply Direct Link To This Post Posted: 21 August 2021 at 3:19pm
I think as long as the voltage is at about 3.2v, they are in the best state they can be for storage. It is basically impossible to determine SOC from voltage though as you say. So if you wanted to be sure, you'd have to charge them up fully, then drain them through an Ah meter into a dummy load until you've taken 25Ah out of each battery. For thoroughness, you'd want to do a full-drain capacity test first to determine actual capacity. Depends how long you want to spend watching an Ah meter I suppose ;)

Studio45 - Box Builder Commotion Soundsystem -Mobile PA
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slaz View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 24 August 2021 at 5:45pm
Yeah OK .... well I couldn't really see any other way to assess SOC.
Actually you'd think a USB port as a means of querying the BMS wouldn't be beyond the wit of man - eh ? Can't see it would cost more than loose change to implement.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SamV Quote  Post ReplyReply Direct Link To This Post Posted: 06 September 2021 at 6:47pm
You can get BMS with various means to output data.

Anyways Studio45 is right, 3.2v (per sec) is the standard storage voltage for lifep04. I'd be curious to test their actual capacity, have you done so? I have one of those 15a capacity testors. I've recently purchased a 120ah of lifep04 cos it was cheap and I'm getting 104ah which is still fantastic for the price, but I'm about to order 1200ah of grade a cells and JBD BMS' to build a battery bank for a friends narrowboat :)

I'd be curious to know what you think of that amp?


Edited by SamV - 06 September 2021 at 6:50pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carlosdelondres Quote  Post ReplyReply Direct Link To This Post Posted: 06 September 2021 at 8:28pm
Originally posted by SamV SamV wrote:

You can get BMS with various means to output data.

Anyways Studio45 is right, 3.2v (per sec) is the standard storage voltage for lifep04. I'd be curious to test their actual capacity, have you done so? I have one of those 15a capacity testors. I've recently purchased a 120ah of lifep04 cos it was cheap and I'm getting 104ah which is still fantastic for the price, but I'm about to order 1200ah of grade a cells and JBD BMS' to build a battery bank for a friends narrowboat :)

I'd be curious to know what you think of that amp?


The narrowboat project sounds interesting, I built a 62V li-ion 1200Ah lithium battery for our barge last winter, super happy with the performance 6 months down the line - what cells are you using?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote SamV Quote  Post ReplyReply Direct Link To This Post Posted: 06 September 2021 at 9:01pm
Mine is going to be a standard 12v affair, using Eve cells, I think 305ah iirc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote carlosdelondres Quote  Post ReplyReply Direct Link To This Post Posted: 06 September 2021 at 10:23pm
Ah 1200AH at 3.2V, thought you were building a traction pack :)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote slaz Quote  Post ReplyReply Direct Link To This Post Posted: 23 September 2021 at 3:35pm
Originally posted by SamV SamV wrote:

You can get BMS with various means to output data.

Anyways Studio45 is right, 3.2v (per sec) is the standard storage voltage for lifep04. I'd be curious to test their actual capacity, have you done so? I have one of those 15a capacity testors. I've recently purchased a 120ah of lifep04 cos it was cheap and I'm getting 104ah which is still fantastic for the price, but I'm about to order 1200ah of grade a cells and JBD BMS' to build a battery bank for a friends narrowboat :)

I'd be curious to know what you think of that amp?


Yeah - but I went for the ready-built battery - Ultramax brand. These (I have 2) are rated 50Ah each, but I haven't done any kind of capacity testing - other than playing em through the Pioneer amp. All I can say right now is they certainly seem to perform - better than I expected.

I played at a wake up in Springfield Park (Clapton) the other night - just using 2 bridged channels of the amp into a single FBT 4R 12" box - ran it hard for about 4.5 hours, and it still needed quite a bit of discharging to get it down to 3.2V/cell :-) That was a _wicked_ do BTW - 2 DJ's doing their thang with Apple laptops and those ridiculously large DJ controller things - plenty of mic action etc.
I was using my 2nd battery to power one of the Apple laptops via a cheapie inverter too !

The Pioneer amp - well I rate it pretty highly. Sounds clean to me - plenty of guts in it and well behaved. The top part of the casing is the chassis basically - the o/p devices are bolted to it.
The only downside (for me) is that its a bit on the heavy side because of that die-cast chassis .... OTOH I think I'd prefer that to relying on some active cooling with a naff little fan somewhere.
The case was luke warm after running 2 channels hard for several hours.
Overall I'd recommend it ....
REMEMBER....POLITICIANS AND DIAPERS SHOULD BE CHANGED OFTEN AND FOR THE SAME REASON
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