Good Morning everyone ! bank of 48 volts and 200 amp

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EMMANIJOA

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Hello Dear Sirs !
I would like to know for a 48 v bank with 200 amp how many 18650 batteries are needed and the BMS how many amps are needed.

Thanks in advance !

Jose
 

OffGridInTheCity

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Hello Dear Sirs !
I would like to know for a 48 v bank with 200 amp how many 18650 batteries are needed and the BMS how many amps are needed.

Thanks in advance !

Jose
You wrote "....48 v bank with 200 amp..." but "200 amp" is not a size but rather a load. Could you clarify what you mean?
For example:
IF you mean 48v @ 200ah (200 amp hours) then that's a battery capacity question / number of 18650s that can be answered.
IF you truly mean 48v @ 200a (200a * 48v = 9,600watts) then that's a battery load question and it would be good if you could say for 'how long' will you draw 200a.

Let's say you're asking about a 48v @ 200ah battery. 1 ah = 1000mah. So you take 200 * 1000 to get 200,000mah. Then divide that by the size of an individual cell to get the number of cells per pack. For example, 200,000mah / 2500mah cell = 80 cells per pack. You need 14 packs in series for 48v. So 14 packs * 80 cells/pack = 1,120cells total.
 
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EMMANIJOA

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I feel very happy with just one day in this forum, the professional and educated way to answer people like me who are not experts or professionals in the energy sector.
To be more exact, my need is 70amp x 12 hours of continuous work at 48 volts.

Using the formula that you sent me, it would be 4,704 cells, my second question at the beginning, what capacity would the BMS be for these cells.

once again thank you so much !!!

Regards

Jose
 

Korishan

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The BMS doesn't determine capacity. It only limits voltage and current.
 

EMMANIJOA

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Thanks

for this case what would be the recommended current

Thanks

Jose
 

OffGridInTheCity

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I feel very happy with just one day in this forum, the professional and educated way to answer people like me who are not experts or professionals in the energy sector.
To be more exact, my need is 70amp x 12 hours of continuous work at 48 volts.
Typically you buy a BMS with a little more capacity than expected use. Also the tend to come in round numbers. For example, a 100a BMS would make sense as it's 30a more than 70a - e.g. 30% headroom.

Using the formula that you sent me, it would be 4,704 cells, my second question at the beginning, what capacity would the BMS be for these cells.
Yes, at 100% and 2500mah cells, it would be 4,704 - e.g. 40kwh. However, you can't actually discharge a lithium-ion battery 100% and have it last very long. So you need to think in terms of a 50kwh battery that you discharge about 80% to get 40kwh of useable power. So now we're up to about 5,900 cells @ 2500mah each.

My own DIY powerwall is 81kwh - so I can say (from experience) that a 50kwh DIY battery bank of 18650 cells is a significant undertaking! You might consider EV batteries or LifePo4 bricks - just a lot less manual hookup / cell processing.
 

EMMANIJOA

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I really appreciate your time and kindness in answering me
Yes, I have heard your recommendation to use EV batteries, but sometimes they are a bit difficult to get or I don't know where they can be found.

regards
jose
 

EMMANIJOA

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Typically you buy a BMS with a little more capacity than expected use. Also the tend to come in round numbers. For example, a 100a BMS would make sense as it's 30a more than 70a - e.g. 30% headroom.


Yes, at 100% and 2500mah cells, it would be 4,704 - e.g. 40kwh. However, you can't actually discharge a lithium-ion battery 100% and have it last very long. So you need to think in terms of a 50kwh battery that you discharge about 80% to get 40kwh of useable power. So now we're up to about 5,900 cells @ 2500mah each.

My own DIY powerwall is 81kwh - so I can say (from experience) that a 50kwh DIY battery bank of 18650 cells is a significant undertaking! You might consider EV batteries or LifePo4 bricks - just a lot less manual hookup / cell processing.
I am a bit confused, a BMS does the charger function or a battery charger is required to be added to the BMS

Please if possible to clarifyme if it is possible to classify me

thanks
 

floydR

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Charging is handled by a charge contoller, often a mppt solar controller/ inverter charger combo, it can be a battery charger but it needs to be made fore Lithium , then you have different chemisties of lithium cells needs to be for the right chemistry
later floyd
 

italianuser

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Hi there Emmanijoa, oh you have a lot of questions I see :giggle:That's good!

I can surely suggest you to start from this: become a guru of capacity and voltage calculations, and talking about batteries... lets take any random type of battery, the 18650:love:. Please do read the whole FAQ section here, you can find a good starting kit.

So, to start with: terminology, abbreviations, measurement units. I'd say, it's no good to talk about BMS without knowing what's underneath it.

So, getting back to what OGITC was correctly saying... these are the first things to know:

A = Ampere, we love amperes. We measure current with amperes. So we could measure how many amps (current) are passing though a wire, a nickel strip, a copper bar by using, for e.g., a DMM (multimeter). That measurement will only give us an instantaneous measurement. "Now the TV is using 0.9A"... "Aww good to know"... "0.9A at 230 volts!"... "wow" (obviously the answers are from our other significant person LOL). My whole house in this moment is using:

1624575803128.png

1.62A of current at 220V. It's an instantaneous measurement.

Ah = Ampere per hour. Oh, this is good, we can measure a capacity with this. We measure our battery capacity with this. Now I'm checking cells capacity, actually it's been my main activity since May. My wife, sun, family, friends and random people met in the street really don't understand why I'm charging cells to discover their effective capacity (LA = Lithium Addiction, search it please). The last cells I checked gave me a capacity of 2047mAh measured today June 25th with an IR of 31, checked in charger n.2 (I have only 3, that's why I'm so slow! But I'm a bit of a noob still). So this cell, a 3.7V cell connected to a load (a load which runs at 3.7V) could give 2.047A for one hour. Obviously if the load only requires 1/10th of 2.047A (0.2047A) to run, then this cell should last 10 hours!

OGITC is OffGridInTheCity💯:giggle:

These were some of the first things I learnt! (What about V volts, oh you must know everything of volts and Ohm law; power; resistance, and watts, oh I love watts, it says a lot of things, for e.g. with one number you can rapresent two other numbers, and watts/hour, Wh) ... (Ah, and "battery jargon", SD, SOH, SOC, ...).

And, yes, do ask a load of questions, post diagrams, schemas and photos!

Enjoy,
jes
 

EMMANIJOA

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Jun 22, 2021
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Charging is handled by a charge contoller, often a mppt solar controller/ inverter charger combo, it can be a battery charger but it needs to be made fore Lithium , then you have different chemisties of lithium cells needs to be for the right chemistry
later floyd
Thank You so Much
 

EMMANIJOA

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Jun 22, 2021
Messages
8
Hi there Emmanijoa, oh you have a lot of questions I see :giggle:That's good!

I can surely suggest you to start from this: become a guru of capacity and voltage calculations, and talking about batteries... lets take any random type of battery, the 18650:love:. Please do read the whole FAQ section here, you can find a good starting kit.

So, to start with: terminology, abbreviations, measurement units. I'd say, it's no good to talk about BMS without knowing what's underneath it.

So, getting back to what OGITC was correctly saying... these are the first things to know:

A = Ampere, we love amperes. We measure current with amperes. So we could measure how many amps (current) are passing though a wire, a nickel strip, a copper bar by using, for e.g., a DMM (multimeter). That measurement will only give us an instantaneous measurement. "Now the TV is using 0.9A"... "Aww good to know"... "0.9A at 230 volts!"... "wow" (obviously the answers are from our other significant person LOL). My whole house in this moment is using:

View attachment 25491
1.62A of current at 220V. It's an instantaneous measurement.

Ah = Ampere per hour. Oh, this is good, we can measure a capacity with this. We measure our battery capacity with this. Now I'm checking cells capacity, actually it's been my main activity since May. My wife, sun, family, friends and random people met in the street really don't understand why I'm charging cells to discover their effective capacity (LA = Lithium Addiction, search it please). The last cells I checked gave me a capacity of 2047mAh measured today June 25th with an IR of 31, checked in charger n.2 (I have only 3, that's why I'm so slow! But I'm a bit of a noob still). So this cell, a 3.7V cell connected to a load (a load which runs at 3.7V) could give 2.047A for one hour. Obviously if the load only requires 1/10th of 2.047A (0.2047A) to run, then this cell should last 10 hours!

OGITC is OffGridInTheCity💯:giggle:

These were some of the first things I learnt! (What about V volts, oh you must know everything of volts and Ohm law; power; resistance, and watts, oh I love watts, it says a lot of things, for e.g. with one number you can rapresent two other numbers, and watts/hour, Wh) ... (Ah, and "battery jargon", SD, SOH, SOC, ...).

And, yes, do ask a load of questions, post diagrams, schemas and photos!

Enjoy,
jes
Thank You so Much !!
 

italianuser

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Messages
400
Sorry Jose, after all I didn't answer your question, nobody can really, and the reason is because it's easy to calculate the number of cells for a 48V 200Ah battery BUT having a bit more information, for e.g. what must you use your battery for, is it a low wattage load or high wattage, or 50/50, or low with some peaks.

I'll give you an answer somehow near to what you asked. My battery 51.8V 176Ah is made up from 1120 cells (well, it will be when I get there! Relatively soon, lets say). And that may seem like a good answer, but you must consider quite a few parameters which are specific for my application. So, it's like saying "How did you make that lovely 3-floor cake?", "I used flower, chocholate, eggs, sugar, cream". You see, that answer doesn't give much information on how to make the cake, really.

A first calculation is simple and fast:

- Each cell is 2200mAh (2.2Ah) at 3.7V.
- I connect 20 cells in parallel and obtain a pack with capacity 44Ah at 3.7V.
- Now I need a higher voltage actually, so I connect 14 packs in series to make a higher voltage of 51.8V (3.7V * 14); and I get a pack with capacity 44Ah at 51.8V.
- This is a stand-alone battery 14s20p, 44Ah at 51.8V, 2279Wh.
- I'll make four and connect them in parallel (44Ah @ 51.8V) x 4 = 176Ah @ 51.8V.
 

ajw22

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Nov 16, 2018
Messages
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To be more exact, my need is 70amp x 12 hours of continuous work at 48 volts.
It would be best if you could describe what exactly you want to power with the battery.
Is it going to get used every day? If so, you'll want to oversize the battery capacity by 20%~50% to extend the lifespan of the cells.
How and how quickly do they need to be recharged?
There are potentially so many aspects to consider depending on the use case, so the more info we have, the more appropriate and useful our replies can be.
 

Roland W

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That size of a battery as you are describing by your demand, and as explained from other commenters what actually that would mean if you build it with 18650 cells (used??), how much time do you have to finish this massive undertaking?

If you are planning to use this system sometime within the next 2 years, I would suggest to go on the Alibaba.com website, search for LiFePo4 280Ah cells, and just order 4x16=64 of those, which would give you about your required capacity. I am sure they can be delivered to any place in the world to your door within a few months. You just might have to pay a bit extra for customs fees.
But in general, you will end up with probably less of expense as well, as you need a lot of equipment to process thousands of cells quickly.
And the LiFePo4 system will be much safer as well, as there is almost no parts to fail, when comparing to the thousands of cells where each single one is a point of failure.

But its your choice ;)
 

EMMANIJOA

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That size of a battery as you are describing by your demand, and as explained from other commenters what actually that would mean if you build it with 18650 cells (used??), how much time do you have to finish this massive undertaking?

If you are planning to use this system sometime within the next 2 years, I would suggest to go on the Alibaba.com website, search for LiFePo4 280Ah cells, and just order 4x16=64 of those, which would give you about your required capacity. I am sure they can be delivered to any place in the world to your door within a few months. You just might have to pay a bit extra for customs fees.
But in general, you will end up with probably less of expense as well, as you need a lot of equipment to process thousands of cells quickly.
And the LiFePo4 system will be much safer as well, as there is almost no parts to fail, when comparing to the thousands of cells where each single one is a point of failure.

But its your choice ;)
Thanks a million for tour assistance
 

Eihab Bannaga

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but i think it dose not limit every battery, only every group in this case, am i right
if i am, how can we check if there is any battery goes down if it is not functioning well??

The BMS doesn't determine capacity. It only limits voltage and current.
 

Korishan

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but i think it dose not limit every battery, only every group in this case, am i right
if i am, how can we check if there is any battery goes down if it is not functioning well??
I don't know exactly what you are asking (not very good translation I'm afraid) But I think you are asking about the condition of each parallel batch of cells in a battery.
The bms monitors the whole battery, this includes the individual parallel packs. It checks each voltage of each series connection. This way the bms knows if any pack is going higher or lower on voltage than the others. If it goes higher, and the bms has a balancing feature, it will use energy stored in that pack to bring it down to the same voltage as the others.

"Most" bms units will do this level of monitoring. But not all have the balancing ability. Those that do not have balancing, will terminate charge at the source
 

Eihab Bannaga

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is there any BMS that can support both functions: monitoring & balancing??
also this BMS should support 200Ah :16P or 17P of 6000 mAh LiFePO4 Batteries
 

Korishan

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Yes, there are plenty. Just do a search for "BMS balancing" and add how many in series you need. For instance if you are building a 7s, then "bms 7s balancing".
Just note that most "cheap" bms units will only balance in very small amounts, like 100mA or less.
 
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