Large cells OK in non-stationary uses?

[100 Proof]

Hi All,

Forum FNG here. This is my first post.

I’ve been successfully using solar on my TT for many years. I mainly dry camp, sometimes for up to 2 weeks. I have a degree in engineering, know my way around electricity, and used to work for a domestic solar panel manufacturer. I’m just now getting up the LiFePo4 learning curve and have read a LOT on this forum and others. I’ve seen most of Will’s YouTube videos.

I’ve currently got a 12V set of 4 FLA GC-2s that are approaching end of life after 5+ years of faithful service. The bank has a nameplate capacity of 416 Ah. I’ve never had the bank get below 70% capacity. I’m looking to build a 12V 200 Ah LiFePo4 battery. I have a few questions:

1- I’ve read on a marine forum that it is not recommended to use cells greater than 200 Ah because,

“A sales manager at Sinopoly I was talking to was adamant about using 100Ah or 200Ah cells only for assembling marine battery banks, with 100Ah being preferred and 200Ah acceptable. Large cells simply don’t have the structural strength-to-weight ratio required to be taken to sea on board small crafts and would exhibit shortened life due to internal mechanical damage arising from on-going vessel motion. It is common sense: as a cell becomes larger, its internal weight increases much faster than the rigidity and surface area of the casing and the casing is all what holds the plates together in a prismatic cell.”

With the proliferation and popularity if 270+ Ah cells, is this cell failure mode being seen in non-stationary applications, or is it possibly too early to tell? I suspect that compression mounting will be key in the long run to manage this.

2- Given that in a solar application, the purpose of a battery bank is to carry loads when the sun isn’t shining, or the loads briefly exceed solar capacity, I want to set my charge controller up to carry loads during the day without discharging, or over charging, the battery. Given the extraordinary flat Voltage curve, and the fact that Voltage levels “settle” after charging, I’m struggling to wrap my head around the variety of charging profiles I’ve seen.

Is a consensus developing around how to deal with this? For those of you with a Morningstar TriStar MPPT-45, is the custom charge profile published by Morningstar adequate as is, or did you tweak it? BTW, I see that even Morningstar has published multiple profiles; one for Battle Born, and one for “generic”. I can’t wait to see how this turns out!

Cheers!

100 Proof

 

[FilterGuy]

Hi All,

Forum FNG here. This is my first post.

I’ve been successfully using solar on my TT for many years. I mainly dry camp, sometimes for up to 2 weeks. I have a degree in engineering, know my way around electricity, and used to work for a domestic solar panel manufacturer. I’m just now getting up the LiFePo4 learning curve and have read a LOT on this forum and others. I’ve seen most of Will’s YouTube videos.

I’ve currently got a 12V set of 4 FLA GC-2s that are approaching end of life after 5+ years of faithful service. The bank has a nameplate capacity of 416 Ah. I’ve never had the bank get below 70% capacity. I’m looking to build a 12V 200 Ah LiFePo4 battery. I have a few questions:

1- I’ve read on a marine forum that it is not recommended to use cells greater than 200 Ah because,

“A sales manager at Sinopoly I was talking to was adamant about using 100Ah or 200Ah cells only for assembling marine battery banks, with 100Ah being preferred and 200Ah acceptable. Large cells simply don’t have the structural strength-to-weight ratio required to be taken to sea on board small crafts and would exhibit shortened life due to internal mechanical damage arising from on-going vessel motion. It is common sense: as a cell becomes larger, its internal weight increases much faster than the rigidity and surface area of the casing and the casing is all what holds the plates together in a prismatic cell.”

With the proliferation and popularity if 270+ Ah cells, is this cell failure mode being seen in non-stationary applications, or is it possibly too early to tell? I suspect that compression mounting will be key in the long run to manage this.

2- Given that in a solar application, the purpose of a battery bank is to carry loads when the sun isn’t shining, or the loads briefly exceed solar capacity, I want to set my charge controller up to carry loads during the day without discharging, or over charging, the battery. Given the extraordinary flat Voltage curve, and the fact that Voltage levels “settle” after charging, I’m struggling to wrap my head around the variety of charging profiles I’ve seen.

Is a consensus developing around how to deal with this? For those of you with a Morningstar TriStar MPPT-45, is the custom charge profile published by Morningstar adequate as is, or did you tweak it? BTW, I see that even Morningstar has published multiple profiles; one for Battle Born, and one for “generic”. I can’t wait to see how this turns out!

Cheers!

100 Proof

I have only recently started hearing the claim that you should only use 200aH cells for mobile so I really don't know how true it is. However, I assume the statement only applies to the aluminum case cells (?). Large Winston cells have been used in mobile systems for a very long time.

The 'strength-to-weight' argument about the aluminum cells does not quite add up for me. If you are putting cells on a boat, you better have them tightly packaged together in a box with no possibility of them moving around in the box. As such, they are going to be one solid package and the aluminum cases are going to be like a honeycomb and quite strong.

Another point is that a boat environment can have a lot more violent movement than a typical RV. (If you have ever been in a small boat dropping off of 10 ft swells you know exactly what I mean) Consequently, as a rule, it would be less of a problem in an RV.

One thing that is true is that the small threads on a lot of the aluminum cells are not very strong and if there is *any* movement of the cells in relation to each other, it is likely to be a problem. However, that is true of all the aluminum case cells, not just the high Ah ones. Because of this Will has said several times that you should only use Forutune cells with their big-ass studs for mobile applications. Since Fortune cells are 100Ah, could this have morphed into "only use low Ah cells"? Stranger misconceptions have happened.

Finally: The skeptic in me can't help but wonder if the "sales manager at Sinopoly" had ulterior motives. The high Ah cells are in short supply right now. Maybe he wants to steer the sales to the cells that are not already in short supply.

Let me close by reiterating that I don't know if it is a problem...... I just wish there was more data behind the statement.

 

[Rocketman]

There have been many people here using the 280ah Lishen or Eve cells in RV's. I will be one one them when my ship comes in... (Really they are on a ship ). So this spring I will be using eight 272ah Lishen cells to create a 12v 500ah(usable) battery for my MotorHome. This will be replacing a Lead Acid 440ah four-CG2's.

I can't help you on your Morningstar equipment (I am using Victron).

2- Given that in a solar application, the purpose of a battery bank is to carry loads when the sun isn’t shining, or the loads briefly exceed solar capacity, I want to set my charge controller up to carry loads during the day without discharging, or over charging, the battery. Given the extraordinary flat Voltage curve, and the fact that Voltage levels “settle” after charging, I’m struggling to wrap my head around the variety of charging profiles I’ve seen.

A good quality Solar Charge Controller won't overcharge the batteries if you can control the specs. After it is charged the SCC drops to "Float" - you set the float voltage equal to what your cell settles to. Then no more power is being added, and the solar is providing the power to your rig.

 

[100 Proof]

I have only recently started hearing the claim that you should only use 200aH cells for mobile so I really don't know how true it is. However, I assume the statement only applies to the aluminum case cells (?). Large Winston cells have been used in mobile systems for a very long time.

The 'strength-to-weight' argument about the aluminum cells does not quite add up for me. If you are putting cells on a boat, you better have them tightly packaged together in a box with no possibility of them moving around in the box. As such, they are going to be one solid package and the aluminum cases are going to be like a honeycomb and quite strong.

Another point is that a boat environment can have a lot more violent movement than a typical RV. (If you have ever been in a small boat dropping off of 10 ft swells you know exactly what I mean) Consequently, as a rule, it would be less of a problem in an RV.

One thing that is true is that the small threads on a lot of the aluminum cells are not very strong and if there is *any* movement of the cells in relation to each other, it is likely to be a problem. However, that is true of all the aluminum case cells, not just the high Ah ones. Because of this Will has said several times that you should only use Forutune cells with their big-ass studs for mobile applications. Since Fortune cells are 100Ah, could this have morphed into "only use low Ah cells"? Stranger misconceptions have happened.

Finally: The skeptic in me can't help but wonder if the "sales manager at Sinopoly" had ulterior motives. The high Ah cells are in short supply right now. Maybe he wants to steer the sales to the cells that are not already in short supply.

Let me close by reiterating that I don't know if it is a problem...... I just wish there was more data behind the statement.

Part of my concern about the physical cell stability is that my travels take me off pavement fairly often, sometimes on really rough roads and sometimes on wash board roads that set up some nasty harmonic vibrations. Like you, I wish there was more data than I have been able to find. Engineers like data!

 

[k3nny]

Take a look the build @cinergi is doing. He purchased SOK batteries off the shelf (back when they were in stock) and then went full mad scientist on a giant 48v system using 280ah cells.

He also has a youtube channel.

https://www.youtube.com/channel/UCAq6fS_qQQMU8a564v1-Ttw

Interesting stuff. It's all going in a custom 5th wheel. I think we're going to continue to see larger ah capacities. Even Battleborn is coming out with a larger battery here soon ( different build than prismatic cells though ).

They are using larger prismatic cells in electric garbage trucks. Those modules are pretty secured though with multiple packs inside of a metal case. FWIW, one of the design tests for these cells is to drop it from 1.5M terminal side down and check for damage, leaks etc.

 

[HRTKD]

I'm frequently off pavement with my toy hauler. My two 4s 280Ah batteries are well secured. Each battery has a compression frame and then that compression frame is secured to the subfloor of the trailer.

I'm not seeing any issues with movement. I recently rechecked all the bolts on the cell terminals and found no instances of loosening. If the battery cells were moving around, I think the bolts would be the first sign.

 

[eranrund]

I'm frequently off pavement with my toy hauler. My two 4s 280Ah batteries are well secured. Each battery has a compression frame and then that compression frame is secured to the subfloor of the trailer.

I'm not seeing any issues with movement. I recently rechecked all the bolts on the cell terminals and found no instances of loosening. If the battery cells were moving around, I think the bolts would be the first sign.

Any details/photos of your build? Would love to see how you've built a compression frame and then secured it to the floor. Thanks!

 

[HRTKD]

Any details/photos of your build? Would love to see how you've built a compression frame and then secured it to the floor. Thanks!

Quick-n-Dirty battery compression frame.



Compartment where it all lives. The battery frames are held down with 1.5" angle aluminum on the sides and the front.

 

[FilterGuy]

Those cells are not going to move!! Good Job.

 

[jwelter99]

I think this is partially coming from the likes of BattleBorn and other assembled battery providers who utilize smaller cells to build up a pack. They are under threat as you can buy 4 280Ah LiFePO4 cells for $400 and easily build something for under $600 that is about the same size as a BB but 2.8x the energy capacity. So $600 versus $3000.

So they start to spread the FUD that the large cells are not suitable.

But this is bullshit as if you think about lead acid we've been hauling big lumps of batteries all over this planet for decades without too much hassle or failures -- as long as they are safely mounted.

The only concern is to make sure you have a rigid frame to keep stress loads off the terminals and to safely keep the complete battery stationary in a crash, roll over, etc, etc, and you are fine. The simple compression setups you see here are perfect examples of what needs to be done.

 

[Bob B]

Did you see how ghostwriter66 characterized it over here?

looks like theyre doing 310AH batteries now for around same price as the 280.

At the rate I'm going my cells will be ancient history before I figure out what the capacity is.

diysolarforum.com

 

[jwelter99]

Did you see how ghostwriter66 characterized it over here?

looks like theyre doing 310AH batteries now for around same price as the 280.

At the rate I'm going my cells will be ancient history before I figure out what the capacity is.

diysolarforum.com

Whats wrong with large breasts in motion? A good bra is all that is required.

 

[Bob B]

Whats wrong with large breasts in motion? A good bra is all that is required.

Did you see the part where she indicated they had a spike in failures the larger the cells. I think the issue is the internal pouches in the cells ... external shock absorption won't do much to help unless it's a pretty exotic setup.

 

[Luthj]

I think the issue is the internal pouches in the cells

Prismatics don't have pouches inside.

Its true the larger cells have taller laminate rolls, which have more force per layer pulling on them. Just a matter of geometry.

Now big high density prismatics are fairly new to the market, so it could just be early teething issues with manufacturing.

Compressing the cells externally with a fixture, especially one with springs or high density rubber pads, provides significant support for the laminate layers. Mobile applications with these larger cells should strongly consider some type of fixture.

 

[cinergi]

Take a look the build @cinergi is doing. He purchased SOK batteries off the shelf (back when they were in stock) and then went full mad scientist on a giant 48v system using 280ah cells.

?

@100 Proof --
I'm doing what I can to mitigate vibration and movement problems by using neoprene between the cells & plywood and using rubber feet under the battery "box" ... so they'll be very tight, under pressure, and have shock absorption. I shouldn't have stress on the cell terminals and the "guts" of the cells shouldn't be sloshing around.

My build thread & parts list are in my sig below if you're interested...

 

[eranrund]

Quick-n-Dirty battery compression frame.

View attachment 38467

Compartment where it all lives. The battery frames are held down with 1.5" angle aluminum on the sides and the front.

View attachment 38468

Thank you!

 

[100 Proof]

?

@100 Proof --
I'm doing what I can to mitigate vibration and movement problems by using neoprene between the cells & plywood and using rubber feet under the battery "box" ... so they'll be very tight, under pressure, and have shock absorption. I shouldn't have stress on the cell terminals and the "guts" of the cells shouldn't be sloshing around.

My build thread & parts list are in my sig below if you're interested...

Thanks!