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First Build...
#1
Hello and thank you for forum, this place is wonderful!
I just finished my first battery pack it is a 24v system, 7s11p I chose 24v for my first build so I could fully enjoy the cost of upgrading to a 48v system later... about half way through this project I changed my mind from a 12v to 24v system and half my parts where non-refundable so this is kinda what I came up with for now... open to whatever advice you are willing to give, thanks in advance.

This is more or less everything I'm working with;

battery pack: 7s11p (~ 2ah/cell = 154ah total) fused with .5 amp fast glass axial fuses
inverter: 3000w reliable
charge controller: 12/24v solarEnz mppt wind/solar hybrid  (600w @ 24v) 
bms: XLX 24V 20A 7s
pv: (temp. solution) 2x 20w panels in series giving me 1amp in sun!
wind: (complete noob buy...) 400w 12v - ok so here is where I have a real problem, the charge controller is only rated to 300w at 12v, 600w at 24v.  My "best" idea so far other than buying an appropriate turbine for the system would be to run the 3 phases output of the 12v turbine through the charge controller that it came with, rectifying to 12v DC which I could then boost up to say 30v?  but then i run into the problem of the input on the charge controller for the wind turbine which are meant for AC... is there an affordable solution to this problem?
also while i have your brain here, I have the charge range for the pack set to 21v on low end 29v on top end, so far I've tested cell at 4.2 when the pack was bouncing along the top charge yesterday all the rest where around 4.17-8 is this recommended?
Thanks for taking the time, I have posted some pictures this might be helpful. 
We live out in the mountains and the power will begin being cutting out soon as it does every winter so I am fairly motivated to fix this and get the system actually functional. 
Happy to clear up anything I left out or got wrong, thanks!
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#2
Fulstein: Have you stress tested your battery build? Perhaps start with more solar to establish the system and then parse out the steps for adding wind. If you're stuck with 12v input from the rectifier, you'll have to boost somehow or suffer elsewhere. Not efficient but can be made to work. Is 20 amps from the BMS enough for your needs?

For 7s the charge range (21v to 29v) seems safe. Yes, keeping your cells charged to 100% all the time will reduce their service life.
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#3
Do everything gradually increasing the load. Previously, as they said earlier, you should do a load test.
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#4
(11-29-2019, 02:35 PM)Fulstein Wrote: Hello and thank you for forum, this place is wonderful!

battery pack: 7s11p (~ 2ah/cell = 154ah total) fused with .5 amp fast glass axial fuses
Welcome!   I agree, this forum has been a real asset to me as I build/manage my own system. 

>battery pack: 7s11p (~ 2ah/cell = 154ah total) f
If I may provide a point of clarification, a battery's ah capability is expressed in terms of its voltage@ah (not just ah).    When you give 7s - e.g. 7 in series - you are indicating the battery is 24v nominal.   Each of the 7 cells is 11p which is 22ah.   When the 7 cells are hooked in series (e.g. 7s) the voltage increases but the ah remain 22ah.   So your battery is more properly written as 24v@22ah  (rather than 3.7v @ 154ah). This is not a *huge* thing - but it will help others 'read you' better.


>all the rest where around 4.17-8 is this recommended?
Pretty much 4.15v (+/- a few mv) is good.   If you look at the discharge curve there isn't much power between 4.20 and 4.15 and if you limit it to 4.15 it gives you a 50mv allowance for variance between the 7s cells of your battery.   You definitely don't want to go over 4.20v.     Ont he bottom end,  (that same discharge curve), you'll find that as you get below 24.5v (3.5v/cell) the amount of remaining power is very small and the cell voltages will start to diverge.    

For me, with 1,000(s) of cells now - I've morphed into a strong focus on life-span.   So I designed and run my system operate between 4.0v top and low at 3.5v (just ahead of the discharge curve knee) in an effort to *greatly* expand the number of daily charge/discharge cycles.     As your investment increases, you may find you develop a similar focus.  

What kind of BMS are you using?   And pics are always fun!
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#5
(01-22-2020, 08:53 AM)Daniel-J Wrote: Do everything gradually increasing the load. Previously, as they said earlier, you should do a load test.
thanks for reading and responding, I have been babying the system treating it more lika an aquarium then something functional. I rarely turn the inverter on because it wasn't generating enough to recharge my little battery with 2x12v@20w panels, series to 24v.  I have tried out a couple loads, the first test was a 250w heat bulb which I plugged directly into the inverter and seemed to take my battery down 1% per minute so after 20 minutes I turned it off.  It was pulling just over 11 amps from battery. I will do a more meaningful test and share the results.

I have also increased my panels from the 2x 12v@20w series to 24v, I now have 10x12v@20w series to 24v@20w.  the wind turbine i replaced with a 24v turbine but i have moved it twice, i think it needs to go on top of the barn but it is spotty at best, solar seems to be the consistent choice.

(12-31-2019, 01:10 AM)Shade Wrote: Fulstein: Have you stress tested your battery build?  Perhaps start with more solar to establish the system and then parse out the steps for adding wind.  If you're stuck with 12v input from the rectifier, you'll have to boost somehow or suffer elsewhere.  Not efficient but can be made to work.  Is 20 amps from the BMS enough for your needs?

For 7s the charge range (21v to 29v) seems safe.  Yes, keeping your cells charged to 100% all the time will reduce their service life.
I couldnt agree more, more solar is the way to go for me, it is much easier to work with and much more reliable.  did buy a rectifier... and a second turbine, this one is 24v and even though we get what i thought was a significant amount of wind out here it doesnt seem to be producing much and is inconsistent but i am planning to move it a 3rd time and see what happens.  That is after my new charge controller comes, the brandless wonder i purchased in ignorance gave up the ghost last night in the middle some serious wind so the turbine has a rope thrown over it right now...  new charge controller is an epever with 4year plan

as for the bms the initial though was to make multiple 24v batteries and parallel them up , each with its own 20amp bms until i get something better like batrium and just baby the load on the inverter accordingly until i get enough amps to do significant work.  but the bms negative to battery isn't connecting so i have bypassed the bms and am just using the now broken charge controller (new epever should be here in 2 days) buts thats a whole different can of worms...

thanks again!

(01-22-2020, 03:48 PM)OffGridInTheCity Wrote:
(11-29-2019, 02:35 PM)Fulstein Wrote: Hello and thank you for forum, this place is wonderful!

battery pack: 7s11p (~ 2ah/cell = 154ah total) fused with .5 amp fast glass axial fuses
Welcome!   I agree, this forum has been a real asset to me as I build/manage my own system. 

>battery pack: 7s11p (~ 2ah/cell = 154ah total) f
If I may provide a point of clarification, a battery's ah capability is expressed in terms of its voltage@ah (not just ah).    When you give 7s - e.g. 7 in series - you are indicating the battery is 24v nominal.   Each of the 7 cells is 11p which is 22ah.   When the 7 cells are hooked in series (e.g. 7s) the voltage increases but the ah remain 22ah.   So your battery is more properly written as 24v@22ah  (rather than 3.7v @ 154ah).  This is not a *huge* thing - but it will help others 'read you' better. 


>all the rest where around 4.17-8 is this recommended?
Pretty much 4.15v (+/- a few mv) is good.   If you look at the discharge curve there isn't much power between 4.20 and 4.15 and if you limit it to 4.15 it gives you a 50mv allowance for variance between the 7s cells of your battery.   You definitely don't want to go over 4.20v.     Ont he bottom end,  (that same discharge curve), you'll find that as you get below 24.5v (3.5v/cell) the amount of remaining power is very small and the cell voltages will start to diverge.    

For me, with 1,000(s) of cells now - I've morphed into a strong focus on life-span.   So I designed and run my system operate between 4.0v top and low at 3.5v (just ahead of the discharge curve knee) in an effort to *greatly* expand the number of daily charge/discharge cycles.     As your investment increases, you may find you develop a similar focus.  

What kind of BMS are you using?   And pics are always fun!

Thanks so much for clarifying, I am eager to learn the jargon and get the most out of this as possible!  I really like the idea of life-span, I have a new c.c. coming in a couple days and will set the user defined to 24.5 and 28v are there any oddities to watch for with a narrower charge range (is there a better way to say that?)

here is a link to the bms i bought https://www.amazon.com/gp/product/B07ST9...UTF8&psc=1
but as i stated in a previous response it seems to have crapped out at the negative out to the c.c.* (typo earlier) so i have bypassed it for now.

I'll get some pics up today, thanks for taking the time I appreciate it
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#6
(01-22-2020, 03:48 PM)OffGridInTheCity Wrote:
(11-29-2019, 02:35 PM)Fulstein Wrote: Hello and thank you for forum, this place is wonderful!

battery pack: 7s11p (~ 2ah/cell = 154ah total) fused with .5 amp fast glass axial fuses
Welcome!   I agree, this forum has been a real asset to me as I build/manage my own system. 

>battery pack: 7s11p (~ 2ah/cell = 154ah total) f
If I may provide a point of clarification, a battery's ah capability is expressed in terms of its voltage@ah (not just ah).    When you give 7s - e.g. 7 in series - you are indicating the battery is 24v nominal.   Each of the 7 cells is 11p which is 22ah.   When the 7 cells are hooked in series (e.g. 7s) the voltage increases but the ah remain 22ah.   So your battery is more properly written as 24v@22ah  (rather than 3.7v @ 154ah).  This is not a *huge* thing - but it will help others 'read you' better. 


>all the rest where around 4.17-8 is this recommended?
Pretty much 4.15v (+/- a few mv) is good.   If you look at the discharge curve there isn't much power between 4.20 and 4.15 and if you limit it to 4.15 it gives you a 50mv allowance for variance between the 7s cells of your battery.   You definitely don't want to go over 4.20v.     Ont he bottom end,  (that same discharge curve), you'll find that as you get below 24.5v (3.5v/cell) the amount of remaining power is very small and the cell voltages will start to diverge.    

For me, with 1,000(s) of cells now - I've morphed into a strong focus on life-span.   So I designed and run my system operate between 4.0v top and low at 3.5v (just ahead of the discharge curve knee) in an effort to *greatly* expand the number of daily charge/discharge cycles.     As your investment increases, you may find you develop a similar focus.  

What kind of BMS are you using?   And pics are always fun!
here are a couple pics to help clarify, there are some unused components left over from 12v wind turbine (ie charge controllers and rectifier)

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#7
Yes sir (thanks for pics), I see axial fuses on the cells - an excellent safety technique. The battery bank has about 22ah * 26v = 572wh... so in practical terms with limited DOD say 400wh battery delivery.

A 600w @ 24v wind power system (in theory) would be able to charge the batter up in 'an hour'. Do you have steady wind? How much power do you produce on average for a day?

Looks like your overall system is pretty well matched (wind power in vs battery bank size) to deliver .. 2-3kwh/day? What are you actually getting / planning to achieve?

(I'd love to play with wind BUT my neighbors, city code, and lack of wind - all conspire to make that totally no-good for my situation - sigh. That's why I'm curious Smile )
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#8
For bms I recommend the chargery bms8 (100 dollar range) that works great with solar, if cells/voltage get near the max it will disconnect the solar panel through a mechanical contactor. Its what I been using on my system for the past year, its been excellent. Its cheaper then a baltrium and can handle as many amps as the contactor is rated for. 

The bms you have right now uses mosfets, if bms decides to stop the charge you will get voltage surges from the controller. As you you push the system closer to the max you will encounter voltage surges especially when you are charging the battery at high amps. The surges occur when the controller tries to charge the battery and bms won't accept a charge.


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#9
(02-02-2020, 04:21 PM)OffGridInTheCity Wrote: Yes sir (thanks for pics), I see axial fuses on the cells - an excellent safety technique.    The battery bank has about 22ah * 26v = 572wh...  so in practical terms with limited DOD say 400wh battery delivery.   

A 600w @ 24v wind power system (in theory) would be able to charge the batter up in 'an hour'.    Do you have steady wind?  How much power do you produce on average for a day?

Looks like your overall system is pretty well matched (wind power in vs battery bank size) to deliver ..  2-3kwh/day?    What are you actually getting / planning to achieve?

(I'd love to play with wind BUT my neighbors, city code, and lack of wind - all conspire to make that totally no-good for my situation - sigh.  That's why I'm curious Smile )

Thanks yeah the fuses are a load off, thanks Average Joe!  my next battery build use them as well and will look more like the brick build that people build for e-bikes and that.  the idea is to have a whole mess of those 24v bricks paralleled.  I bought and tested 100 more cells, ready to build just waiting on me but their capacitance is on average 2700mah each whereas the previous battery pack's average is around 2000mah per cell, will this cause problems once paralleled?

That is a very encouraging thought on the wind turbine.  I don't feel i can quite answer that yet. you are supposed to mount the turbine 20ft above  all surrounding obstacles but i want to be able to physically stop it or whatever i need to do until i am comfortable with the system.  the short answer is yes, i believe we get enough wind but i don't have the turbine in the right spot yet to that, when it gets going though its usually around 27v@2amps on average but its never more than an hour or so at a time.  Once i get the turbine mounted off the top of the barn I hope to get some better numbers and then will talk of performance in a meaningful way. 

That's too bad about neighbors and not much you can do about wind huh?  on the plus side, taking wind out of the equation simplifies the system and costs less! I haven't heard any complaints from mine but i haven't asked either but i did spray paint my turbine copper to make it look cool... i think


thanks again for taking the time, have a good one!

(02-02-2020, 05:42 PM)jonyjoe505 Wrote: For bms I recommend the chargery bms8 (100 dollar range) that works great with solar, if cells/voltage get near the max it will disconnect the solar panel through a mechanical contactor. Its what I been using on my system for the past year, its been excellent. Its cheaper then a baltrium and can handle as many amps as the contactor is rated for. 

The bms you have right now uses mosfets, if bms decides to stop the charge you will get voltage surges from the controller. As you you push the system closer to the max you will encounter voltage surges especially when you are charging the battery at high amps. The surges occur when the controller tries to charge the battery and bms won't accept a charge.


 Thanks for the suggestion and insight on the inner working of bms units the explanation of what happens when the cc send more current than the mosfet bms wants is great, thanks.  seems each component of this system is a world unto its self. 
I am checking out the website now : http://www.chargery.com/balancer.asp  looks awesome and built specifically for this application, thanks I'll look into it more and bms systems in general. 
Do you think this bms will work with multiple 24v batteries paralleled or only with one large 24v battery?  I ask becasue I would like to build my system scalable and as modular as possible (i.e. anyone could hypothetically come in and unplug or swap out a bad 24v pack) . Thanks so much for taking the time and sharing some thoughts!
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