bms batrium

100kwh-hunter

100kwh-hunter

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Hi,
I bought several months ago a batrium bms for a 24v system with 14 longmons.
Now i have done some reading on this million dollar siteand its better for me to go to a 48v system instead a 24v system.

Can i use the bms that i already have?
I was not able to get the required info on there site, that why this question.

An other question:
Sinds i am planning to make 14 packs (48v) of 100 cells each(times 3(3x14 packs) for now to start with)
The first 28 packs will be at the same capacity.(2x 14 packs)
The first 14 packs will have a SOH of more then 90%
The second 14 packs between 80% and 90%, majority will be above 90%
The rest above 80%
After this only the same capacity per packand above 80% per 14 packs

I am going to use Daromer method to fill in the packs: start with the biggest pile of cells and distribute them over the packs, till that one runs out i will take a lower mAh bucket.


With this data as described as above, do i need a bms?

Question one: Can i use the bms that i already have?
Question two: Do i need a bms?

Any input or info is very appreciated, thanks in advance.
 
Im not sure you ask question 2 at all since you allready know the answer?

A sorting method or knowing SOH of cells does not relieve you from adding protection and management.

You say you did order a "bms" from batrium but you did not tell us what product you did order and therefore we do not know to answer. With that said all their watchmons work up to 65VDC so thats not an issue. What differs is the expansion board.

14 longmons is enough to 1 series of batteries. You say you are going to have 3 then you need to order another 28 longmons.

Only way to get away with 14 longmons is to hook all your series up in paralell ending up with only 1 14s system and not 3.
 
May I ask what has convinced You to go 48 Volts?

I ask because I just finished the transition from 48 V 5 KW to 24 Volts and 2 x 3 KW.

I know, 24 volts will get You 3 KW only, not 5 per AC Inverter, so You need 2 inverters instead of one.

However, most domestic electric systems provide only 3 KW per Group. 230/240 V AC 13 A is a standard rating.

Oh, Yesss. 6 KW at 24 Volts is 200+ Amps... Thick cables, and higher loss, or? Not really.

If You have 4 banks 7s each bank will be max 50A at full load.

That is exactly the same load as if You make 2 x 14p banks and One 5 KW inverter.

Now, why 24 volts?

As You already found out, building cell banks of even capacity may not be as easy as it seems, specially because we build with cells of different origins and capacity.

Each cell bank is different and when You connect them in series You will only get the Ah of the lowest rated bank.

At 48 Volts You get the lowest of 14. At 24 Volts You get the lowest of 7.

(I have 4 rows of 7: 170 Ah, 190 Ah, 240 Ah and 280 Ah, this gives me 880 Ah at 24 Volts. Now try 48 Volts and get 170 + 240 = 410 at best (not 440).

Another reason is this: Solar input varies heavily during the Year, from almost noting in December to plenty in June.

My 5 KW inverter uses 1,2 KWh/24 Hours in Idle. No big deal in June, but in December, this may be all I get of solar input. My 24 V inverter uses 15 Watts in Idle or 0.36 KWh/24 Hrs leaving me .8 Kwh for use, compared to nil at 48 V.

(This must be a tiny plant, not? Well, I have5KW of PV panels (2 KW grid tied and 3 KW for my battery system)and I am severely running out of space, so increasing solar input may be impossible.)

One last thing: As Daromer said, the Batrium will do a great job as a bms, and it will do it just as good if You choose 24 Volts as if You choose 48 V. You just need more longmons.



Best of Luck to You

ChrisD
 
You do need a BMS.
You need to (at least):
a) know what the pack is doing, &
b) be able to trigger alarms &/or protection if something goes out of spec.
Unless you're a multi-meter addict (bad idea), it needs to be automated by a BMS.
Second hand cells increase the need for a BMS.
What you've got will work like Daromer says.
I'd suggest having a couple of spare longmons.
 
100kwh-hunter said:
Question two: Do i need a bms?
Click to expand...

LiIon without a BMS is like parachuting without parachute.

I saw several people here thinking they can go without, and i saw several people here which went without and desribed how and when her system failed.

Example; a complete bank of a 14s structure shortcut (0 Volt) and the voltage distributed to the remaining 13, which means 4.7 Volts on the cells.
 
Agree 100% BMS is worth it!. In my case, I thought I could get by with random voltmeter measurements here and there every few days. Big mistake as the lack of detail stressed several of my packs due to undetected low voltage and I had to replace several hundred cells. BMS $ would have paid for themselves - no to mention the safety features that Batrium offers to sleep well.
 
@ Daromer.
question number two: I was in doubt because several forum members and on youtube stated that you don't need a bms.
Especially if you put your pack good together, I already had a strange "taste"/bad feelingfrom/aboutit.

My Batrium "bms" is a "watchmon4"

I think also a 1 14s with 300 cells per pack is a little to much, also to take in consideration a possible repair/maintenance.
So my first setup would be 3 14s with 100 cells per pack or 6 7s with 100 cells per pack
This is not depending on the "bms" that i have.
That imust buy more longmons, is not trivial.

Thanks in advance.

@ Chrisd.
A lot of people do it the other way around, from 24 to 48, they also had very good arguments to do it.
Your thinking is also my thinking about the loss, maintenance, solar input and use of the idle mode.
Your statement about 24v holds firm solid ground, also, mind you i am still learning, before i start planning i want to know the pro's and con's
Every input is welcome and very appreciated.
In Holland we have a standardof 16 amp on 230 ac ~3.6kwh.
I can get away with 10a per group except the woodworking shed :angel:
Increasing your solar input is possible, stronger pv panels, i dont know what you have right now, but i thought LG that they have the strongest ones: 365wP.
https://www.alma-solarshop.nl/lg-zonnepanelen/1151-lg-zonnepanelen-neon2-365w.html

Thanks.

@Redpacket,
I want a "bms" but some people give me some doubt, so i thought: oke lets ask.
I really want to know what is going on inside, i am not going to take it for granted

@ Cherry,
I dont want to be impolite, but as written all above, with one but....
Parachuting without parachute is not so bad...its the face of the earth. :D
In case of Li ion, the wallet :s

Thanks for the answersand thanks in advance for all youre answers.
Best
 
I would not in any way favor 24V system compare to 48V if we talk about powering a whole house. A normal household here would at 24V would demand continues 500A :) But that is a question everyone need to determine.

No there is noone here that state that you dont need a bms. As soon as you have more than 1 cell in series you need a system that can monitor individuall cell voltages.

I think you are good to go as long as you order 28 more longmons and you will have a great setup.
Dont forget a shunt trip breaker or equal so that Batrium can disconnect the battery as well. Without that you wont have the protection!
 
Re the inverter loss comments above, better inverters like Victron the losses @48V are much less, mine is max about 35W/hr.
Some inverters, eg PIP are known for high idle current & some people have modified them & dropped this by heaps (you have to be pretty good at electronics & know what you're doing, it's not so simple to do).
 
I've been tracking AIMS 12,000 watt inverter 'loss'. For PV input kwh I get the value from Midnite Classic 150. For Inverter output values I get them from a cheap power meter attached to the AC output of the Inverter. This shows AIMS is delivering 85% of the input power. So 15% loss. I admit the values are only as good as the measurments but the AIMS documentation say 88% is 'peak' (max) Inverter effeciency - so 85% output (15% losss) is probably reasonable. I understand that more expensive inverters might achieve more of a 95% efficiency range. Mine is a 48v system. I don't think 48v vs 24v is the key issue here - but rather the quality (expense) of the inverter.
 
@ Offgridinthecity.
I have no means to insult you, but its not about the quality of the inverter.
This was for real a question 24v vs 48v.

For my first "setup experiment" i will buy something like a mpp or so.
After that if everything is running like it suppose to do, i will switch to more durable stuff, like vectron or similar.

Also your info is much appreciated, like you're aims.
That reminds me: for cheap kwh meters, i have some where some old analog kwh counters, :)
 
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