How many BlockMons to purchase

80211

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May 19, 2020
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Trying to workout how many BlockMons I need to purchase. Getting mixed messages from YouTube videos and support,
This is my layout in a rack. Its going to be 48x 3.2v cells to make 12x 12v groups (4 cells per group), with 12 groups making 1260ah (15.12kwh) 12v pack.
My understanding this is a4s12p setup (Please correct me if I am wrong)

Also going to have a Super Capacitor to take up some of the surge loads.

So how many BlockMon's do Ineed?


image_lvzhlf.jpg
 

Redpacket

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First up, any reason you're going for a 12V system with that much storage - it's a pretty huge battery bank for 12V?
Can you tell us about what you're using the system for?
For larger loads maybe consider a 48V system or at least 24V?
The current draw & surge numbers are also much better at 48V.

Re the blockmon count, you should have a separate blockmon for every cell in that layout so 48.

If you changed to parallel connect each horizontal row of 3 cells, you could have a blockmon per row so 16.
 

OffGridInTheCity

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Redpacket said:
First up, any reason you're going for a 12V system with that much storage - it's a pretty huge battery bank for 12V?
Can you tell us about what you're using the system for?
For larger loads maybe consider a 48V system or at least 24V?
The current draw & surge numbers are also much better at 48V.

Re the blockmon count, you should have a separate blockmon for every cell in that layout so 48.

If you changed to parallel connect each horizontal row of 3 cells, you could have a blockmon per row so 16.
Agree with @Redpacket. It looks like you have created 12 seperate 12v batteries.... in 4 groups of 3? and each of the 4 groups are hooked in parallel? and all 4 groups are hook in parallel down fuse?

Even if you stick with 12v (and again, I agree with @Red - to many amps and 24 or 48 would better) you could parallel the cells - and reduce the number of blockmons.
For example if you took a group of 3 separate 12v batteries and converted that into 4s3p you would only need 4 block mons per group instead 12 per group as @Red says.
 

daromer

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You need 1 blockmon PER cell-pack. So all boils down to how many packs you going to use? recommended is not to go above 300-600Ah or something per mon.

Secondly the supercap is just waste of space and usecase. Supercap is used on car audio where you dont have enough surge power for bass. In an inverter you have built in caps to handle all surges allready and long term current is handled by the battery. You dont save anything having it

Lastly go high voltage if you can. Dont do 12v and instead do 48 aka 16s.

if you have 1 string of 16s you need 16 block mons. 16 per string.
 

80211

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Thanks all for your words and advise.
I need to go 12v as I have 2x existing 3kva Victron Inverters that are 12v. I would love to go to higher voltage.

However I'm still confused, We have
Redpacket said:
Re the blockmon count, you should have a separate blockmon for every cell in that layout so 48.

Then

daromer said:
You need 1 blockmon PER cell-pack.

I see Cell as a 3.2v Cell
I see Cell-Pack as 4x 3.2v Cells (Making 12v)

Let me try and simplify this.

How many blockmons would be required for this:

image_xdxwqg.jpg



Thanks once again.
 

OffGridInTheCity

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80211 said:
Thanks all for your words and advise.
I need to go 12v as I have 2x existing 3kva Victron Inverters that are 12v. I would love to go to higher voltage.

How many blockmons would be required for this:

image_xdxwqg.jpg
.
The aboveis 4s1p (4 inseries, 1 parallel) - you need 4 blockmons. 1 for each 'cell' in series.

This is 4s4p (4 in series, 4 parallel) - and again, you only need 4 blockmons - 1 for each 'unit'(4 cells in parallel)that is hooked in series. Its the unitsin series that BMSs monitor / balance individually. Cells hooked in parallel act as '1 cell' since parallel wiring will force the cells to have the samevoltage at all times... as if it were just 1 cell. This is why XsYp (e.g. 4s1p or 4s4p or xxx)is used toavoid ambiguity in terms :).

image_tsuoqs.jpg
 

Redpacket

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Planning to move to 48V would be much better long term.
The current drawn by 2x 3kva at 12V is truely massive, & it seems by your wanting a supercap, you already have issues with surge currents.
3,000/12 x2 = 500A! + surges on top. Jeepers!
The cables you'd need for that would be multiple parallel 70sq mm copper runs - the losses really add up at 12V.

Re the blockmons, like off grid explained, you can parallel some of your cells & have one blockmon manage/monitor that group.
With those large capacity cells, your rack layout & your high draw, I'd suggest a max of three cells in parallel per blockmon, hence the total 16 blockmons.

You should have a couple as spares too.
 

daromer

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The surges is still handled by the inverter... Nothing outside will help that you notice.....
 
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