12v 90AH Li-Ion build

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Swazytrain

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I am currently working on a project that needs a Li-Ion battery to power a 50Lb. thrust min kota riptide trolling motor. I am a novice at this so you might have to bear with me here a bit. The end result i am looking for is to have a 12V Li-Ion battery with a 80-90Ah rating. i would like to make it up out of two packs to be mounted seperatly in a long staggered formation....

:) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :)
:) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :)

something like that.......

The cells i will be using are CGR18650E cells out of old/new panasonic tough book batters. they have a nominal voltage of 3.7V and a standard capacity of 2550mAh. what i need to find out is if it ispossible to do this in this configuration..... how many cells do i need....how do i go about the wiring configuration and what is the correct BMS for this application.... Do i sound like im asking the right questions?
 
Swazytrain said:
I am currently working on a project that needs a Li-Ion battery to power a 50Lb. thrust min kota riptide trolling motor. I am a novice at this so you might have to bear with me here a bit. The end result i am looking for is to have a 12V Li-Ion battery with a 80-90Ah rating. i would like to make it up out of two packs to be mounted seperatly in a long staggered formation....

:) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :)
:) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :) :)

something like that.......

The cells i will be using are CGR18650E cells out of old/new panasonic tough book batters. they have a nominal voltage of 3.7V and a standard capacity of 2550mAh. what i need to find out is if it ispossible to do this in this configuration..... how many cells do i need....how do i go about the wiring configuration and what is the correct BMS for this application.... Do i sound like im asking the right questions?
Click to expand...

2 packs at 7.2v each
each pack must be 80 ah min
that means 40 cells in parallel and 2 in series. (assuming 2000 mah capacity)
So 80 cells per pack in 2s 40 p configuration X 2 packs =160 cells
Wire the packs together in Series to get 14.4 volt 80 Ah ........

But that would be at full discharge capacity, which means short life span of the already used batteries.
So if you doubled the number of cells that would give roughly 50% depth of discharge.
So 320 cells would be better
 
Or 2 packs of 40Ah each and 12v in paralell :)
 
daromer said:
Or 2 packs of 40Ah each and 12v in paralell :)
Click to expand...

So what would a working diagram of this look like? What about a BMSfor monitoring and charging the cells?

[quote pid='3074' dateline='1488649333']

2 packs at 7.2v each
each pack must be 80 ah min
that means 40 cells in parallel and 2 in series. (assuming 2000 mah capacity)
So 80 cells per pack in 2s 40 p configuration X 2 packs =160 cells
Wire the packs together in Series to get 14.4 volt 80 Ah ........

But that would be at full discharge capacity, which means short life span of the already used batteries.
So if you doubled the number of cells that would give roughly 50% depth of discharge.
So 320 cells would be better

[/quote]
I know going over is ok on the voltage (way better than being too low) but is 14.5 v too much? If each pack was 80 AH when I link them together wouldn't it make it 160 AH? The battery's I'm using is new old stock so they have never been used. And I will test them all and make sure they are all of like voltage. So 2x 2s 40p battery's is what I'm looking for creating? What about a BMS?
 
Regardless of whether a cell is new or reused, you don't want to take a cell lower than 3.5V and not charger beyond 4.1V if possible. Since you will be using it for a trolling motor, I'm going to guess that you would be charging them quite often. So you want to get as many cycles out of the cells as possible.

So, increasing the number of cells/packs in your build will allow you to work in a more safer set up. Both for longevity of the cells, and the safety factor of not over-discharge/charge the cells.

As I stated in one of my other posts, these cells are like the cylinders in an engine and all give you a motor with a max rating of hp/torque. You normally do not use any where near the max, even under heavy use. If you do constantly, you dramatically reduce the life on the engine, or in this case, the battery pack.

Build a larger than needed pack (aH rating), and you'll be safe all around. Plus, you have the added bonus that if you do need the extra power (taking longer to come back in), then you'll have the reserve power to make it back.
 
WKorishan said:
Regardless of whether a cell is new or reused, you don't want to take a cell lower than 3.5V and not charger beyond 4.1V if possible. Since you will be using it for a trolling motor, I'm going to guess that you would be charging them quite often. So you want to get as many cycles out of the cells as possible.

So, increasing the number of cells/packs in your build will allow you to work in a more safer set up. Both for longevity of the cells, and the safety factor of not over-discharge/charge the cells.

As I stated in one of my other posts, these cells are like the cylinders in an engine and all give you a motor with a max rating of hp/torque. You normally do not use any where near the max, even under heavy use. If you do constantly, you dramatically reduce the life on the engine, or in this case, the battery pack.

Build a larger than needed pack (aH rating), and you'll be safe all around. Plus, you have the added bonus that if you do need the extra power (taking longer to come back in), then you'll have the reserve power to make it back.


awsome thank you so much for the info. What about a BMS? How do I go about figuring out what I would need for that?
Click to expand...
 
Swazytrain said:
I know going over is ok on the voltage (way better than being too low) but is 14.5 v too much? If each pack was 80 AH when I link them together wouldn't it make it 160 AH? The battery's I'm using is new old stock so they have never been used. And I will test them all and make sure they are all of like voltage. So 2x 2s 40p battery's is what I'm looking for creating? What about a BMS?
Click to expand...

No.
When you join two batteries in series, you increase voltage but amps remain the same.

So a 2s 40p battery would be 80 AH at 7.2 volts.
Joining two of them in series would give you 80 AH at 14.4 volts

or, like daromer said, you could do 4s 20p.
This would give you a 14.4v pack at 40 AH.
Join two of these in PARALLEL to get 80 AH @14.4v

Same number of cells in both configurations (160). I suggested two 7.2v configuration because its a little easier to solder the packs.

Most DC motors can run over voltage without damage. Many use voltage as a means of speed control and have wide range of voltage input like 0-130v.

Not sure if you even would need a BMS for a trolling motor application....you could probably just get a balancing hobby charger and hook it up as needed.
If you want a BMS I would look on ebay, AliExpress, Bangood for a BMS board of either 2s or 4s, depending on how you build your packs.
 
Figure four watt hours per cell for something that will last, you need ~1200 watt hours so 300 cells, someone worked it out another way upthread and came up with 320 so that's a good rough number.

Whether you run 3s or 4s will depend on the maximum voltage your motor will handle. If it will take 16+ volts then you will like the way it runs on 4s.
 
Elmo said:
Figure four watt hours per cell for something that will last, you need ~1200 watt hours so 300 cells, someone worked it out another way upthread and came up with 320 so that's a good rough number.

Whether you run 3s or 4s will depend on the maximum voltage your motor will handle. If it will take 16+ volts then you will like the way it runs on 4s.
Click to expand...

3S is not an option for him. Batteries should sized based on their NOMINAL rating, not full charge voltage.

With a 3S, He will be running at <12v in minutes, unless he builds HUGE battery.

A 4S battery under load will be running at 13-15 volts, typically 14.4v the nominal rating
 
Its normal with that low :) And generally not needed more on those systems since they balance like all the time.

But yes its not much.
 
UPDATE! So i have decided to go with the 2s40p 7.2V battery. I dont need extra power because i will be mounting this trolling motor to a surf board. the extra power and battery life wouldnt be needed because im not using the motor at full throttle ever.
so my next thing is i plan on putting the batteries into a semi-perminate box that can be opened on the occasion of some trouble but otherwise remain sealed.from the batteryboxwires run through a conduit to a accessable junction box.... so here is where im still not clear about this BMS? do i need it? what is the best way to monitor my batteries and charge them from the junction box without having to get at the batteries all the time?
After looking into all this im not sure if i am ready to jump in and make these batteries. I already have plentyof work fabricating these batteryboxes and fiber glassingeverything together. Is there ways to find people around that would be interested in making these for me? Im from the boston area.... anyway if i have to make these batteries i will but it would be good if i could find someone that was interestedto help.
The motor in mounted to the board and running. ill add a video when i figure out how.
P


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Cool. If you want feel free to start a Project thread about it and we can break it out from your question thread :) In "DIY Powerwall Builds"

I will sure follow it!
 
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