Connecting up Six LiFePO4

[Routemaster]

I see somewhere that one should not connect up six batteries up in parallel could someone be so kind as to help me out to keep the 12v output? Very new to this subject.
Den.

 

[TedH]

What battery manufacturer? That may be a restriction. Does each battery have an internal bms?

Is each battery a 12v case? If connecting in parallel, you will need good bus bars or thick cables. I configured six, 24v batteries (8 cells each) into a bank of 48 cells (6P8S). Bus bar thickness and length of connections between cells need to be uniform. I leveraged 3/8" thick, 1" wide hard aluminum bars (drilled).

 

[Routemaster]

I have bought 4 off Li Time 12v 100AH LiFePO4 Trolling Motor and then bought two more (2) later then I have a 4/0 welding cable connecting the four (4) at this time do I carry on the connection in parallel for the two or would I have to make two sets of three somehow?

 

[TedH]

I have bought 4 off Li Time 12v 100AH LiFePO4 Trolling Motor and then bought two more (2) later then I have a 4/0 welding cable connecting the four (4) at this time do I carry on the connection in parallel for the two or would I have to make two sets of three somehow?

To keep all things equal, I would carry on the connection in parallel add the two 100ah batteries into the mix of 4, 100ah batteries in same configuration for a total of six.

Do the Li time batteries have internal BMS?

 

[Steve_S]

There is absolutely No Problem with having 6 LFP battery packs in parallel.
The best way is to connect them all to a common DC Bus by using busbars.
Most "common" busbars are 4 bolt but larger ones are available.
Battery Wires to Bussbar MUST be same length for ALL Packs (excluding fuses/switches etc) *1, *2
*1 This is to ensure that they are equal for charge & discharge. LFP is Millivolt/Milliohm sensitive.
*2 Each fuse/switch/device adds resistance and therefore some voltage drop.
Battery Packs in Parallel DIVIDE both Load & Charge !

6x100AH in parallel can output a Max of 600A & take a Max of 300A (using std defaults)
Consider this when accounting for the charging capacity.

Below is a generic diagram showing 3 AIO's (All In One) Inverters in parallel along with 3 12V Battery Packs in parallel.
Each Battery Pack must be fused, with 12V you have the option of also using 100A MRBF Fuses
The BUSBARS used must be capable of handling the Max Amp Draw that your system can pull. BEWARE of the cheap "value priced" pairs found on EBay etc...

Hope it helps, Good Luck.

 

[Routemaster]

To keep all things equal, I would carry on the connection in parallel add the two 100ah batteries into the mix of 4, 100ah batteries in same configuration for a total of six.

Do the Li time batteries have internal BMS?

Yes to Ted.
Thanks all love that picture by Steve that sort thing helps.
Cheers.
Den.

 

[Routemaster]

I wrote to the company and the response was not to have more than four (4) batteries in parallel because of the damage to the BMS board.

 

[Steve_S]

If putting battery packs in SERIES, there is a voltage increase issue and should one fail in such a configuration there can indeed be many unpleasantries.

When putting packs in Parallel, they are the same voltage across all packs, the only thing that changes is the stored capacity (AH) and if any pack fails within a parallel setup, it will not have a negative affect on the other packs. There are a LOT of us here running well over 4 packs in parallel.

There are also many people here who are using LiTime batteries as Will did reviews on them, including terardowns etc over the past couple of years.

 

[augiedoggy]

If putting battery packs in SERIES, there is a voltage increase issue and should one fail in such a configuration there can indeed be many unpleasantries.

When putting packs in Parallel, they are the same voltage across all packs, the only thing that changes is the stored capacity (AH) and if any pack fails within a parallel setup, it will not have a negative affect on the other packs. There are a LOT of us here running well over 4 packs in parallel.

There are also many people here who are using LiTime batteries as Will did reviews on them, including terardowns etc over the past couple of years.

There is one drawback of the parallel wiring.. And that is the reduction of capable current from the pack available to the load which can still cause a chain reaction of the bms all shutting down. If the load is never high enough to trip the remaining bms overcurrent protection then this doesnt happen.

 

[augiedoggy]

There is one drawback of the parallel wiring.. And that is the reduction of capable current from the pack available to the load which can still cause a chain reaction of the bms all shutting down. If the load is never high enough to trip the remaining bms overcurrent protection then this doesnt happen.

How is that funny? Its a valid drawback unless the battery back is sized to output a much higher continuous amp output than the load ever reaches.

If a person has 2 100ah batteries in parallel and one battery happens to trip the bms when say a 160 amp load is put on the pack even for a few moments, (lets say its in a camper and someone leaves the coffee maker on and tries to turn on a microwave also. just for an example) Then the second battery will likely trip also. On paper the load would evenly be shared between both batteries and each battery would only see an 80 amp load but thats not how it always works in practice. (especially if the discharge curve on the batteries differed from being different cells or aged cells vs new) If it were a single 200amp rated battery it would be a non issue.

Some of the less expensive batteries do not have much of a peak rating vs continuous rating if at all.

 

[Supervstech]

There is one drawback of the parallel wiring.. And that is the reduction of capable current from the pack available to the load which can still cause a chain reaction of the bms all shutting down. If the load is never high enough to trip the remaining bms overcurrent protection then this doesnt happen.

If a 160A load is tripping the paralleled BMS of two 100A batteries, there is a wiring issue.

 

[Steve_S]

Battery Packs in PARALLEL share both Load & Charge.
2x 100AH in Parallel can deliver 100A ea or 200A collectively. 6 in Parallel can deliver 600A collectively or take 300A charge.
This assumes "Standard 100AH LFP" which outputs at 100A for 1 hour (1 C-Rate) to takes 50A for 2 hours (0.5C Rate)
Each battery pack is independent and not dependent on the others.
Each Battery Pack in Parallel MUST also be fused as well and fused per the specific packs capacities.

 

[Checkthisout]

The issue is a short that could result in backfeeding undersized conductors.

You need a fuse at the busbar for each individual battery and then adjust the overcurrent protection of each bms to not much more than it would ever deliver @ peak assuming all the batteries are working.

You want all the bms to trip if one trips, not the other way around.

 

[augiedoggy]

If a 160A load is tripping the paralleled BMS of two 100A batteries, there is a wiring issue.

Most likely yes, I agree. but some state otherwise to quote this company


https://earthxbatteries.com/lithium-battery-series-parallel-operation-2/



"Maximum Safe Operating Limits When two batteries are put in parallel the continuous discharge amp rating and charge amp rating is typically reduced to 90% of the two batteries' combined rating."



But regardless this sort of thing has been reported on the golf cart forums with both series and parallel setups. where the load the parallel packs are seeing is not 100% evenly split in real time. If someone cobbles together a battery bank of different brand batteries purchased at different time the discharge curves and resistance of said batteries may contribute to different actual cell voltages under load. All im saying is there are more potential issues to consider depending on variables with parallel packs. I see and read of reports all the time on you tube and the golf cart forums where people mistakenly buy 100amp 12v cheap batteries and have issues with the bms tripping even when they are not actually seeing a full 100amp load. sometimes this is from balancing issues and sometimes its from improperly built and speced batteries.

Again my point is once one battery has a bms trip for any reason the capacity and current output of the rest of the pack is negatively effected and the result could be the rest of the pack also going into overcurrent state.

There are also a decent amount of these 12v batteries that are limited by the bms in how many can be series connected together if at all. And it appears this limitation can also be an issue with parallel connections as in this case.

Theres also a good discussion on this here.

Why cant I run more than 4 lifepo4 batteries in parallel?

Looking at Chins or Ampere Time batteries from amazon (12v200ah models) and they both say 4s4p MAX. Why is this? How would the batteries even know if I set up for example 16 units all in parallel for a massive reserve bank? Our Lifepo4 batteries can be connected in parallels and in series...

diysolarforum.com

 

[Routemaster]

This is how I connected my first four LiFePO4s up all 4/0 (I was told larger less drop no cheap) cable lengths are the same, now I just wanted to add two more for more power. Now I have very limited space in my 5er to add 2 more and was going to stack them and continue with the parallel method but was told should not do that this is why I wrote to Li Time what they suggested is not unlike Steve's picture but smaller way. I am now stumped. Just some to point me in the right direction as I am a visual person and like to drawings or drawings where to place fusses and size.
Cheers.
Den.

 

[pollenface]

Some manufacturers specify unlimited parallel capabilities

 

[740GLE]

I wrote to the company and the response was not to have more than four (4) batteries in parallel because of the damage to the BMS board.

If they recommend this, don’t be suprised if some headaches arise.

By adding two more batteries, is this because load is increased? Or just more storage?

What’s your peak load placed on the current 4p set up? <100a or you pushing 300a?

 

[Partimewages]

If wired properly I can't understand what the issue could be for parallel operation.

 

[augiedoggy]

If wired properly I can't understand what the issue could be for parallel operation.

these are lithium batteries so it does depend on the the batteries and bms used in the batteries as there is no baseline certified standard it seems. add to the fact that a applications and load vary from application to application.

 

[DIYrich]

One risk I can envision is that batteries may change each other. The more batteries in parallel, the more potential current. I have 2 banks of one battery type, and one bank of another. All banks are about 15kwh. For some reason the solo bank seems to carry the other two while resting. I have a shunt on each bank, and can see the slight current/voltage difference.

Other situation is daisy chain via dual terminals on a battery. The battery can only passthrough so much current. If each battery is independently connected to a busbar, then not an issue.