Lithium Battery Upgrade

[SilentService]

I currently purchased three lithium batteries to replace my 4 6v lead acid ones. I plan to run them in parallel.
(3) Zooms 12V 200Ah LiFePO4 Battery Lithium Iron Phosphate Battery Deep Cycle Rechargeable Battery with Built-in 100A BMS

In my mind, I still have to get the following;

(1) Progressive Dynamics PD9160ALV 12V Lithium Ion Battery Converter/Charger - 60 Amp
(2) Post Power Distribution Block Bus Bar Pair with Cover - 250 Amp Rating
(4) 2 AWG Gauge Ultraflex EPDM Fully Assembled Battery Cables
(1) Victron Energy BMV-712 Smart Battery Monitor with shunt

I also have a 250amp ANL fuse, a battery disconnect switch and a 2500 watt inverter.
Eventually I plan on adding around 400-600 watts of solar to supplement my two 2500 watt generators.

Solar aside, what am I missing and is the fuse, bus bars and battery cables sized properly?

[SolarPoweredRV]

I currently purchased three lithium batteries to replace my 4 6v lead acid ones. I plan to run them in parallel.
(3) Zooms 12V 200Ah LiFePO4 Battery Lithium Iron Phosphate Battery Deep Cycle Rechargeable Battery with Built-in 100A BMS

In my mind, I still have to get the following;

(1) Progressive Dynamics PD9160ALV 12V Lithium Ion Battery Converter/Charger - 60 Amp
(2) Post Power Distribution Block Bus Bar Pair with Cover - 250 Amp Rating
(4) 2 AWG Gauge Ultraflex EPDM Fully Assembled Battery Cables
(1) Victron Energy BMV-712 Smart Battery Monitor with shunt

I also have a 250amp ANL fuse, a battery disconnect switch and a 2500 watt inverter.
Eventually I plan on adding around 400-600 watts of solar to supplement my two 2500 watt generators.

Solar aside, what am I missing and is the fuse, bus bars and battery cables sized properly?

First, I would recommend running each battery directly to a (single/common) bus bar instead of stringing them together in a Parallel configuration. Electrically you will still be in "Parallel", however, by running each battery to a Bus-Bar you have the capability of pulling 100a from each battery for total of 300 (+) amps, whereas, with a "Parallel" configuration you would be limited to the 100 amp limit of the built-in BMS.

Second, you are going to have a very big battery bank, if you do decide to run each battery to a bus-bar you will want to fuse each battery (around 150a) and fuse the whole bank at 300 to 400 amps. Additionally, it is recommended that all the cables from each battery to the bus bar be the same length to ensure even charging and energy draw.

You will also want to install a battery cut-off switch, I recommend the Blue Sea battery cut-off switch.

You are going to Love having a Lithium (LiFePo4) battery bank.

I have attached a wire gauge chart below to help you with your cabling decisions:

[SilentService]

Thanks for replying! I never would have thought setting up the batteries/buses that way. One question I have using this set up. What advantages do I have going from 100 to 300 amps and do I need that much amperage?

[JKellerJr]

First, I would recommend running each battery directly to a (single/common) bus bar instead of stringing them together in a Parallel configuration. Electrically you will still be in "Parallel", however, by running each battery to a Bus-Bar you have the capability of pulling 100a from each battery for total of 300 (+) amps, whereas, with a "Parallel" configuration you would be limited to the 100 amp limit of the built-in BMS.

Second, you are going to have a very big battery bank, if you do decide to run each battery to a bus-bar you will want to fuse each battery (around 150a) and fuse the whole bank at 300 to 400 amps. Additionally, it is recommended that all the cables from each battery to the bus bar be the same length to ensure even charging and energy draw.

You will also want to install a battery cut-off switch, I recommend the Blue Sea battery cut-off switch.

You are going to Love having a Lithium (LiFePo4) battery bank.

I have attached a wire gauge chart below to help you with your cabling decisions:

Interesting, I understand the idea behind a bus bar configuration and how it could be advantageous.

On the battery bms limitation, if you string the batteries together pulling the + & - from the same battery (which I get, is not the best idea) I could see how, since everything flows through a single battery, the bms could trigger.

I have mine strung together (4 batteries) in parallel with the + off one battery and the - from the battery on the other end of the string. How is that seen by the bms?

I never thought about it. I don’t have any issues and I’ve maxed out the victron multiplus II to the point of overload on it without triggering the bms but it’s an interesting question

[SolarPoweredRV]

Interesting, I understand the idea behind a bus bar configuration and how it could be advantageous.

On the battery bms limitation, if you string the batteries together pulling the + & - from the same battery (which I get, is not the best idea) I could see how, since everything flows through a single battery, the bms could trigger.

I have mine strung together (4 batteries) in parallel with the + off one battery and the - from the battery on the other end of the string. How is that seen by the bms?

I never thought about it. I don’t have any issues and I’ve maxed out the victron multiplus II to the point of overload on it without triggering the bms but it’s an interesting question

With respect to paralleling multiple batteries; the best configuration is to use a Bus-Bar, the next best configuration is to pull the energy out of the middle of the pack (think of the cabling being in an "H" pattern), the next best configuration is to draw the + and - from opposite ends of the battery bank, of course, the least favored method is to draw from a single battery at the end of the pack. The reasoning has to do with electron flow and electrical efficiency, the electrons are going to flow from the nearest source to the load, and in the last case it would be from the battery first in line. In this case the other batteries are constantly "recharging" the first battery in line.

With a Bus-Bar configuration each battery is contributing equally to the load, making the configuration more efficient, this is also true when charging. This is also the reason you want your cable lengths to be as equal as possible for each battery.

Realistically, in an RV which configuration you choose may not make much difference, however if your configuration creates a hot spot (or choke point for the electrons) then you are loosing efficiency through wasted heat, heat in the form of warm wires is more likely in a 12v system than a 24v system, this is why many 12v installations use 4/0 (four ought) cables for their installation (24v systems can use much smaller cabling).

The Bus-Bar configuration creates the most efficient method to get energy out of multiple batteries.

[SilentService]

First, I would recommend running each battery directly to a (single/common) bus bar instead of stringing them together in a Parallel configuration. Electrically you will still be in "Parallel", however, by running each battery to a Bus-Bar you have the capability of pulling 100a from each battery for total of 300 (+) amps, whereas, with a "Parallel" configuration you would be limited to the 100 amp limit of the built-in BMS.

Second, you are going to have a very big battery bank, if you do decide to run each battery to a bus-bar you will want to fuse each battery (around 150a) and fuse the whole bank at 300 to 400 amps. Additionally, it is recommended that all the cables from each battery to the bus bar be the same length to ensure even charging and energy draw.

You will also want to install a battery cut-off switch, I recommend the Blue Sea battery cut-off switch.

You are going to Love having a Lithium (LiFePo4) battery bank.

I have attached a wire gauge chart below to help you with your cabling decisions:

If I'm reading this correctly, my bus bars should be rated for 300 amps as well?

[SilentService]

http://www.smartgauge.co.uk/batt_con.html

Your referring to method #3 on this link.

[SolarPoweredRV]

http://www.smartgauge.co.uk/batt_con.html

Your referring to method #3 on this link.

Yes, number 3 is correct.

This article explains, in detail, exactly why I recommended using a Bus-Bar configuration to connect multiple batteries. The article points out that the standard method of "Paralleling" the batteries in a simple string truly places an extra burden on the first battery (the battery with the load attached) when both charging and discharging. When using the Bus-Bar configuration each battery is charged and discharged equally eliminating excess wear on the first battery in a string.

By-the-way, the differences between the first and last battery in a simple Paralleling is astonishing when you read the article linked to above.

[SolarPoweredRV]

If I'm reading this correctly, my bus bars should be rated for 300 amps as well?

Your Bus-Bars only need to be rated for the maximum draw from your total load. Usually your Inverter will be your highest drawing load, the remainder of your 12v loads should be small compared to your Inverter draw (if you have hydraulic stabilizers and slides add 90 - 100 amps), this will give your max draw and your required fuse size. This will also determine the amperage of your other components such as Bus-Bars and cabling. Your Bus-Bars are usually rated at 250 amps at 600 volts, not 12 volts, so, you have to do the math to ensure the Bus-Bars will handle the load safely.

Reminder: this is a sustained load limitation, you may choose to consider your hydraulic system to not be a sustained load since it is usually operated for only a minute or two at a time.

I can give you an example from my own system:

Note I am running a 24 volt system so the numbers on a 12v system will be doubled.

I have fused my system at 150 amps, this is the size of the fuse that comes directly off of my battery box, so, the max draw or charge on my system is 150 amps. My Inverter is capable of charging my batteries at 70 amps, however, since I chose to go with the 150 amp fuse, I have limited my charging to 50 amps in order to not get too close to my 150 amp limitation (note: I also have a large Solar array which can add charging amperage to my system so, I need to keep those amps in mind also).

[SilentService]

Thanks for pointing me in the right direction. You gave me a lot of information to get started. I hope you don't mind my picking your brain from time to time as I progress with this project. Thanks again!

Tim