BMS for a 20 cell 1000 AH LiFePo4 battery pack.

[757driver]

Looking for suggestions. I am looking at installing 20 LiFePo4 cells (180-200 AH cells) for somewhere between 900 AH and 1000 AH at 12v in a power hungry (residential fridge etc) motor home that already has 1100 watts of solar and a Midnite Solar 150 controller.

I have heard good good things about the Orion Jr but it is only good for 16 cells. What retail options are available that would work for such a system with 20 cells?

Thanks for any suggestions.

Don

[NEOH]

Orion Jr = all 16 cells are in series?
Is your battery pack going to be 5P4S ?
Maybe use 5 balancers, with each 4 cell balancer attached to one string of 4 cells?

[karrak]

Each LiFePO4 (LFP) cell has a nominal output voltage of 3.2V. To make a 12V battery you have to wire four in series. As you have 20 cells you would first wire five in parallel to make four 3.2V 1000Ah blocks and then wire each of the 1000Ah blocks is series to make your 12V battery. This configuration is called 5p4s. The BMS sees each of the 1000Ah blocks as one cell so you only need a BMS that can handle four cells. The Orion Jr can handle up to a 48V battery.

1000Ah is large for a 12V system, do you already have an inverter and if so what power output is it?

Is this battery replacing an existing battery?

Do you know what your average daily power consumption is?

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[757driver]

Orion Jr = all 16 cells are in series?
Is your battery pack going to be 5P4S ?
Maybe use 5 balancers, with each 4 cell balancer attached to one string of 4 cells?

Yes, pack will be 5P4S.

[757driver]

Each LiFePO4 (LFP) cell has a nominal output voltage of 3.2V. To make a 12V battery you have to wire four in series. As you have 20 cells you would first wire five in parallel to make four 3.2V 1000Ah blocks and then wire each of the 1000Ah blocks is series to make your 12V battery. This configuration is called 5p4s. The BMS sees each of the 1000Ah blocks as one cell so you only need a BMS that can handle four cells. The Orion Jr can handle up to a 48V battery.

1000Ah is large for a 12V system, do you already have an inverter and if so what power output is it?

Is this battery replacing an existing battery?

Do you know what your average daily power consumption is?

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

Yes, two Magnum inverters, one MS2812 and one MS2012.

Replacing an 827 AH AGM battery pack.

Daily power consumption is around 4200 watts.

Understand the the wiring of the pack so only 4 cell monitors needed but was hoping for individual cell monitoring or is that not necessary or a little over the top?

Don

[NEOH]

I found this ...

http://www.batterypoweronline.com/conferences/wp-content/uploads/2012/09/Elithion.pdf

Make sure voltages are identical before connecting in parallel.
Do you have battery interconnects?

[757driver]

I found this ...

http://www.batterypoweronline.com/conferences/wp-content/uploads/2012/09/Elithion.pdf

Make sure voltages are identical before connecting in parallel.
Do you have battery interconnects?

i don't have anything yet, still in the planning stages.

[Sunking]

I found this ...
http://www.batterypoweronline.com/co...9/Elithion.pdf

Make sure voltages are identical before connecting in parallel.
Do you have battery interconnects?

The very first thing you do with any Lithium Ion Battery is connect all of them in parallel and walk away. Then you either completely discharge them to 2.5 volts for a Bottom Balanced System, or charge to 3.6 volts for Top Balance.

OP I have an Orion Jr. I use don my racing golf cart. It is way over kill for a 12 volt system as you would only use 4 channels. I used 16S for 48 volts, but got rid of it as there is no need for a BMS is you Bottom Balance.

I will tell you using 12 volts is a very bad idea for what you have in mind. Think 16S 48 volts. Will be a lot less expensive. Both a 12 volt 1000 AH and 48 volt 250 AH have the exact same amount of panel power power and both will require 1500 to 2000 watt panel system. If you use 12 volts will require two very expensive 80 Amp MPPT Controllers.Use 48 volts and all you need is a single 40 amp Controller. Not only will controller cost be 1/4, but also wire cost. With 16 S, then you can utilize an Orion Jr instead of just 1/4 of it. Best of the Chi-Com LFP batteries is CALB. Stay away from Winston and GBS. Very poor quality.

By the way do not listen to Karrak, he is a fraud and has been band a few times for poor and dangerous advice.

Last tidbit of advice is look into Bottom Balance. Requires no BMS, eliminates the chance of over discharge, and will double the cycle life of the batteries.

[karrak]

Yes, two Magnum inverters, one MS2812 and one MS2012.

Replacing an 827 AH AGM battery pack.

Daily power consumption is around 4200 watts.

Understand the the wiring of the pack so only 4 cell monitors needed but was hoping for individual cell monitoring or is that not necessary or a little over the top?

Don

Is your 827Ah AGM battery large enough and what minimum %SOC do you currently go down to? The reason I ask I that you might not need 1000Ah of LFP storage as the LFP batteries are more efficient than AGM batteries and you can use 80%-90% of the capacity. My system's LFP battery that if converted to 12V would be 720Ah with 1140 watts of solar panels is enough to supply around 3kWh per day in winter and 5kWh per day in summer. Our climate is similar to southern California. We have never needed a backup generator but have had to cut back our discretionary usage on some occasions.

When you hook the cells up in parallel, to the outside world they become one cell and it is difficult and unnecessary to monitor the individual cells.

Since you are already set up for 12 volts I don't see any reason to change the voltage. If you were starting out from scratch and didn't want to charge your battery via your car's alternator and/or didn't want to run any 12V equipment off the battery I would think 24V or 48V maybe a better choice.

Another option with the BMS is this one

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[757driver]

The very first thing you do with any Lithium Ion Battery is connect all of them in parallel and walk away. Then you either completely discharge them to 2.5 volts for a Bottom Balanced System, or charge to 3.6 volts for Top Balance.

OP I have an Orion Jr. I use don my racing golf cart. It is way over kill for a 12 volt system as you would only use 4 channels. I used 16S for 48 volts, but got rid of it as there is no need for a BMS is you Bottom Balance.

I will tell you using 12 volts is a very bad idea for what you have in mind. Think 16S 48 volts. Will be a lot less expensive. Both a 12 volt 1000 AH and 48 volt 250 AH have the exact same amount of panel power power and both will require 1500 to 2000 watt panel system. If you use 12 volts will require two very expensive 80 Amp MPPT Controllers.Use 48 volts and all you need is a single 40 amp Controller. Not only will controller cost be 1/4, but also wire cost. With 16 S, then you can utilize an Orion Jr instead of just 1/4 of it. Best of the Chi-Com LFP batteries is CALB. Stay away from Winston and GBS. Very poor quality.

By the way do not listen to Karrak, he is a fraud and has been band a few times for poor and dangerous advice.

Last tidbit of advice is look into Bottom Balance. Requires no BMS, eliminates the chance of over discharge, and will double the cycle life of the batteries.

Thanks for the information and ideas. Motor home is already fully set up as a 12v system from the alternator to the solar to the two inverters so I think I will stick with a 12v system. If starting from scratch would look at going with a higher voltage system and a DC to DC converter.

[757driver]

Is your 827Ah AGM battery large enough and what minimum %SOC do you currently go down to? The reason I ask I that you might not need 1000Ah of LFP storage as the LFP batteries are more efficient than AGM batteries and you can use 80%-90% of the capacity. My system's LFP battery that if converted to 12V would be 720Ah with 1140 watts of solar panels is enough to supply around 3kWh per day in winter and 5kWh per day in summer. Our climate is similar to southern California. We have never needed a backup generator but have had to cut back our discretionary usage on some occasions.

When you hook the cells up in parallel, to the outside world they become one cell and it is difficult and unnecessary to monitor the individual cells.

Since you are already set up for 12 volts I don't see any reason to change the voltage. If you were starting out from scratch and didn't want to charge your battery via your car's alternator and/or didn't want to run any 12V equipment off the battery I would think 24V or 48V maybe a better choice.

Another option with the BMS is this one

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

Currently DOD is to a max of 50%. I understand I will have more usable power with lithium but I wanted a slightly larger battery bank to what I have now. Looked at that BMS you mentioned and while I like the idea of wireless Bluetooth it looks like the current sensors would be a challenge to fit over a 4/0 cable.

[Sunking]

Thanks for the information and ideas. Motor home is already fully set up as a 12v system from the alternator to the solar to the two inverters so I think I will stick with a 12v system. If starting from scratch would look at going with a higher voltage system and a DC to DC converter.

OK RV is different. But that still gives you a large problem. Where the hell are you planning on putting 1500 to 2000 watts of panels?

For a 4S system, there is no need for any BMS, and a BMS is not even capable of balancing a 1000 AH battery. Example lets say you are just 1% out of Balance at the top using an Orion BMS. 1% of 1000 AH is 10 Amp Hours. Balance current on the Orion is 0.15 amps. 10 AH / .15 Amps = 67 hours or 10 days on solar. Completely useless.

If you Bottom Balance, life is easy. No BMS to worry about, pay for, and will extend the life of your batteries at least twice. You charge at 13,4 to 13.6 volts, and set your Inverter LVD to 12 volts. As for panel wattage, there is no way you are going to get 1500 to 2000 watts of panels on an RV. Rather than worry about $3000 worth of panels and another $1500 worth of charge controllers, Just buy a $75 Electronic Battery Isolator to allow you to charge the house batteries from the engine alternator. Put on a few panels for show-n-tell, but in reality will not do much for you on an RV parked in the shade so you can stay cool. Make sure you also have a generator, you are going to need it to protect those $6000 batteries.

[karrak]

For a 4S system, there is no need for any BMS, and a BMS is not even capable of balancing a 1000 AH battery. Example lets say you are just 1% out of Balance at the top using an Orion BMS. 1% of 1000 AH is 10 Amp Hours. Balance current on the Orion is 0.15 amps. 10 AH / .15 Amps = 67 hours or 10 days on solar. Completely useless.

This is not correct. As part of the commissioning process when installing an LFP battery you should make sure it is balanced. If you top balance the battery it will be 0% out of balance when you start using it. Unless there is a fault in the battery or interconnects, the battery will only go out of balance very slowly. It would be unlikely for the battery to go more than 1% out of balance over a period of a year. This equates to 0.027Ah per day. With a balancing current of 0.15A it would take 11 minutes per day to correct the imbalance.

Even if the balance circuit was unable to keep up with the battery going out of balance or a fault made the battery go out of balance the BMS would detect that one of the cells was going outside its safe operating range and raise the alarm. This is somewhat like having fuses in a circuit to protect the circuit from faults that may never occur in the life of the equipment but could be a critical safety feature if a fault or unforeseen set of circumstances pushes the equipment outside its safe operating zone.


Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[Sunking]

This is not correct. As part of the commissioning process when installing an LFP battery you should make sure it is balanced.

Please tell everyone how are you suppose to perform the initial Bulk Balance? When you receive cells, SOC is all over the place. On a 1000 AH cells you can have over 10% or 100 AH difference. At 100 AH difference you are talking 100 AH/ .15 A =666 hours.

Karrak you are the one full of chit. DIY do not have the ability or equipment to Top Balance cells. Go away, you are not welcome here.

[karrak]

Please tell everyone how are you suppose to perform the initial Bulk Balance? When you receive cells, SOC is all over the place. On a 1000 AH cells you can have over 10% or 100 AH difference. At 100 AH difference you are talking 100 AH/ .15 A =666 hours.

You have several options for doing the initial top balance:

1. Ask the battery supplier to do it for you. If you do this don't assume that it will be done correctly.
2. My preferred option, use a hobby balance charger. I have a Turnigy Reaktor 20A balance charger. An added bonus with this charger is that you can use it to do cell capacity and other tests. To do the balance, wire all the cells in parallel, set the charger voltage to 3.6V, Bal.Trickle to ON and start. When you purchase the cells they should be about 40% full so will need around 600Ah for a 1000Ah @12V battery, this equates to 2400Ah at 3.2V. It would take around 120 hours (5 days) to balance a 1000Ah 12V LFP battery using a 20A balance charger. A variation to speed the balance up is to wire the cells in series and parallel to make a 12V or higher battery and do a balance charge to 3.45V/cell (13.8V for 12V battery). When the first 3.2V cell reaches 3.45V stop the charge, hook all the cells in parallel and then finish off the balance at 3.6V.
3. Use a variable power supply set at 3.6V to charge all the cells in parallel. Stop the charge when the current going into the cells drops to around zero.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller