Fogstar or Roamer and why

[Guigsy]

Yes we don’t pull same currents, but prismatic do run hotter than cylindrical, and it’s not me only, do your research.
We don’t use automotive traction cells here, these are much weaker cells.

Each prismatic cell will produce more heat, but there's less of them. So the total heat the battery produces will be roughly the same. Same chemistry. And like I said, they're in similar external boxes, so the cooling ability will be about the same. I bet they end up being roughly the same temperature overall.

 

[Hoovie]

There seems to be a bit of an obsession of Fogstar and Roamer batteries on this forum (plus KS Energy I guess)
And go on Youtube, the only game in town for a "vanlifer" appears to be the Ecotree Lithium.

There are other options, and ones which JUST WORK without having to constantly wonder what BMS is fitted? does it top or bottom balance? are they prismatic or cylindrical cells? is the case Royal Blue or Navy Blue? (ok, I made the last one up, but wouldn't be shocked to have read that discussion )

So i’m torn between these 2 suppliers so has anyone any advice or experience or indeed suggestions of anyone else

i’m looking at minimum 400ah single or double

cheers Al

So really for me, the question is - Do you want a new hobby, or do you just want a battery?

I run a pair of Polarmax Lithiums in my Motorhome. 100Ah each, as part of my 500Ah Hybrid system, but that Hybrid bit is by-the-bye.

I initially got these from the supplier (Alpha Batteries) to evaluate and check for all the things that people are reporting on Lithiums, such as:

1. Going into sleep mode when not enough load (Got experience of KS Energy doing that and the user needing to keep lights on just to stop the battery shutting down! Seen it with other brands as well);
2. Batteries built-in SOC reporting going Haywire (got experience of that with Lithiums fitted with the JK BMS (as loved by Andy of the Off-Grid garage fame) amongst others);
3. Batteries shutting down when the temp gets close to zero (no, they should NOT shut down, just not allow charging as the most).
4. Multiple paralleled Batteries going out of sync with each other (pretty common one for most brands. There are even facebook groups where folk claim batteries with Bluetooth BMSes cannot be paralleled, but non-bluetooth BMSed can (they think that as they have no idea what the SOC on a non-BT Battery is so assume it matches!)
5. And a few other bits and pieces (such as can it be serviced? many Lithiums are sealed and case cannot be removed. Relion is an example of that, but it is pretty common).

I benchtested the Polarmax Batteries for a few weeks, charging and discharging. Low loads to check for sleeping; high loads to check they delivered, etc, then I put them in the Motorhome and ran them in a "real life" situation for a couple of months I think it was. Basically I tried to find fault with them and break them.
And in the end, I didn't send them back, I bought them with my own money as they did not fail a single test I performed.
I don't know if they top or bottom balance (don't care). I don't know if they are cylindrical or prismatic cells (prob prismatic, but doesn't matter); and I don't care that I cannot program the BMS to the nth parameter. In fact, I don't even know what brand of BMS is in the battery, as it really doesn't matter if it works like it should.

I can check the batteries to see if all is ok if I want, so did so this morning to get some screenshots for this post....

Two Batteries - perfectly in sync. Under heavy load or high charge the SOCs can go out from each other by up to 1% I have noticed.

These batteries communicate via a RJ45 data cable in order to balance charge levels between the two batteries and not just balance the internal cells.

Cells for each balanced well enough I reckon. (Top? Bottom? Who cares!)

6mV difference between highest and lowest. That will do me!

And Info for Current, Temp and Cycles to date.

(temp is to -20C as the batteries have integral heaters)

Sometimes it is worth paying a little bit extra for a battery that is fit and forget and just does what you want it to!

 

[Gromett]

There seems to be a bit of an obsession of Fogstar and Roamer batteries on this forum (plus KS Energy I guess)
And go on Youtube, the only game in town for a "vanlifer" appears to be the Ecotree Lithium.

There are other options, and ones which JUST WORK without having to constantly wonder what BMS is fitted? does it top or bottom balance? are they prismatic or cylindrical cells? is the case Royal Blue or Navy Blue? (ok, I made the last one up, but wouldn't be shocked to have read that discussion )

So really for me, the question is - Do you want a new hobby, or do you just want a battery?

I run a pair of Polarmax Lithiums in my Motorhome. 100Ah each, as part of my 500Ah Hybrid system, but that Hybrid bit is by-the-bye.

I initially got these from the supplier (Alpha Batteries) to evaluate and check for all the things that people are reporting on Lithiums, such as:

1. Going into sleep mode when not enough load (Got experience of KS Energy doing that and the user needing to keep lights on just to stop the battery shutting down! Seen it with other brands as well);
2. Batteries built-in SOC reporting going Haywire (got experience of that with Lithiums fitted with the JK BMS (as loved by Andy of the Off-Grid garage fame) amongst others);
3. Batteries shutting down when the temp gets close to zero (no, they should NOT shut down, just not allow charging as the most).
4. Multiple paralleled Batteries going out of sync with each other (pretty common one for most brands. There are even facebook groups where folk claim batteries with Bluetooth BMSes cannot be paralleled, but non-bluetooth BMSed can (they think that as they have no idea what the SOC on a non-BT Battery is so assume it matches!)
5. And a few other bits and pieces (such as can it be serviced? many Lithiums are sealed and case cannot be removed. Relion is an example of that, but it is pretty common).

I benchtested the Polarmax Batteries for a few weeks, charging and discharging. Low loads to check for sleeping; high loads to check they delivered, etc, then I put them in the Motorhome and ran them in a "real life" situation for a couple of months I think it was. Basically I tried to find fault with them and break them.
And in the end, I didn't send them back, I bought them with my own money as they did not fail a single test I performed.
I don't know if they top or bottom balance (don't care). I don't know if they are cylindrical or prismatic cells (prob prismatic, but doesn't matter); and I don't care that I cannot program the BMS to the nth parameter. In fact, I don't even know what brand of BMS is in the battery, as it really doesn't matter if it works like it should.

I can check the batteries to see if all is ok if I want, so did so this morning to get some screenshots for this post....

Two Batteries - perfectly in sync. Under heavy load or high charge the SOCs can go out from each other by up to 1% I have noticed.
View attachment 752963View attachment 752964
These batteries communicate via a RJ45 data cable in order to balance charge levels between the two batteries and not just balance the internal cells.

Cells for each balanced well enough I reckon. (Top? Bottom? Who cares!)
View attachment 752965View attachment 752966
6mV difference between highest and lowest. That will do me!

And Info for Current, Temp and Cycles to date.
View attachment 752971View attachment 752972
(temp is to -20C as the batteries have integral heaters)

Sometimes it is worth paying a little bit extra for a battery that is fit and forget and just does what you want it to!

£599 for 100AH vs £369 from Fogstar. A bit extra is one thing... But this is quite the difference.

 

[MisterB]

There seems to be a bit of an obsession of Fogstar and Roamer batteries on this forum (plus KS Energy I guess)
And go on Youtube, the only game in town for a "vanlifer" appears to be the Ecotree Lithium.

There are other options, and ones which JUST WORK without having to constantly wonder what ....

So really for me, the question is - Do you want a new hobby, or do you just want a battery?


I benchtested the Polarmax Batteries for a few weeks, charging and discharging. Low loads to check for sleeping; high loads to check they delivered, etc, then I put them in the Motorhome and ran them in a "real life" situation for a couple of months I think it was. Basically I tried to find fault with them and break them.
And in the end, I didn't send them back, I bought them with my own money as they did not fail a single test I performed.
I don't know if they top or bottom balance (don't care). I don't know if they are cylindrical or prismatic cells (prob prismatic, but doesn't matter); and I don't care that I cannot program the BMS to the nth parameter. In fact, I don't even know what brand of BMS is in the battery, as it really doesn't matter if it works like it should.

Sometimes it is worth paying a little bit extra for a battery that is fit and forget and just does what you want it to!

That sounds like a lot of testing, checking, in depth knowledge etc to get a battery that 'just works'! Perhaps you also see this battery lark as a hobby

 

[Hoovie]

That sounds like a lot of testing, checking, in depth knowledge etc to get a battery that 'just works'! Perhaps you also see this battery lark as a hobby

Initial Note - I am NOT supplying this product as I don't sell kit anymore from the start of the current Financial Year.

When I used to supply products, I used to first check them out extensively to make sure they worked as they should. This goes for Chargers, Solar Controllers, and other Motorhome electrical items, INCLUDING Batteries.

So no, I didn't see this battery 'lark' as a hobby, I saw it as a BUSINESS. And a Business where you supply a quality product which works and you don't get returns on.

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[Hoovie]

£599 for 100AH vs £369 from Fogstar. A bit extra is one thing... But this is quite the difference.

Get what you pay for.

If you read the OPs question, they ask "...or indeed suggestions of anyone else". This is a suggestion from someone else.

 

[Gromett]

Get what you pay for.

I don't see that the extra you get for that £230 is paying for what you get?
Is there a specific flaw in the Fogstar one that is a game changer that is not present in the Polarmax that warrants £230 more?

I am not knocking your choice/decision in any way. I for instance won't touch any other brand other than victron for chargers, MPPT and inverters due to quality issues I have had with other so called good brands.
And I certainly won't touch cheap chinese no name tat. So I understand the argument. For example I had so many failures with Sterling stuff I refuse point blank to use them anymore, but they have a good reputation.
I have never had a victron product fail on me. But on batteries, I am not totally convinced there is enough difference between the battery brands as most of them are just assembling components made by other people.

I did a brief search on Xplorer and found they also do what they call a base battery which is the same price as the Fogstar.

12v Xplorer Base 100ah Lithium LiFePO4 Battery - Alpha Batteries

12V Lithium battery by Xplorer for Lead acid battery replacements. General Information This specification defines the performance of rechargeable LiFePO4 […]

www.alpha-batteries.co.uk

Are they a better brand than Fogstar? Or is it the specifics in the PolarMax battery itself you like? So would you pick an Xplorer Base over a Fogstar if so is there a specific reason.

I note you seem to be particularly taken with the cross battery balancing. That suggests to me there is more technology in the battery than is actually necessary for most motorhome leisure battery systems?

I personally don't see £230 worth of value in the PolarMax product for my particular use cases, but others may have different ideas.

If you read the OPs question, they ask "...or indeed suggestions of anyone else". This is a suggestion from someone else.

I wasn't knocking you, I found your post interesting but I had questions That is why I marked your post with "Nice One" rather than just a like.


PS: Just re-read my post. Hope I am not coming across as argumentative. I am not trying to be, I am genuinely curious as I will be spending money in the near future on batteries.

 

[Hoovie]

I don't see that the extra you get for that £230 is paying for what you get?
Is there a specific flaw in the Fogstar one that is a game changer that is not present in the Polarmax that warrants £230 more?

I am not knocking your choice/decision in any way. I for instance won't touch any other brand other than victron for chargers, MPPT and inverters due to quality issues I have had with other so called good brands.
And I certainly won't touch cheap chinese no name tat. So I understand the argument. For example I had so many failures with Sterling stuff I refuse point blank to use them anymore, but they have a good reputation.
I have never had a victron product fail on me. But on batteries, I am not totally convinced there is enough difference between the battery brands as most of them are just assembling components made by other people.

I did a brief search on Xplorer and found they also do what they call a base battery which is the same price as the Fogstar.

12v Xplorer Base 100ah Lithium LiFePO4 Battery - Alpha Batteries

12V Lithium battery by Xplorer for Lead acid battery replacements. General Information This specification defines the performance of rechargeable LiFePO4 […]

www.alpha-batteries.co.uk

Are they a better brand than Fogstar? Or is it the specifics in the PolarMax battery itself you like? So would you pick an Xplorer Base over a Fogstar if so is there a specific reason.

I note you seem to be particularly taken with the cross battery balancing. That suggests to me there is more technology in the battery than is actually necessary for most motorhome leisure battery systems?

I personally don't see £230 worth of value in the PolarMax product for my particular use cases, but others may have different ideas.


I wasn't knocking you, I found your post interesting but I had questions That is why I marked your post with "Nice One" rather than just a like.


PS: Just re-read my post. Hope I am not coming across as argumentative. I am not trying to be, I am genuinely curious as I will be spending money in the near future on batteries.

My take is that I would not want to deal with returns on anything I supply. For ANY products.
So I avoid unknowns. And I avoid stuff I know people have had issues with that should just not be there. Product failure is unfortunate but it happens. Design Faults and poor QC can be a nightmare!

So take that sister thread here about hassles with a Roamer (I think) where the SOC shifts around for no reason and the cycle count has jumped to 7000+ randomly. That has got to be a failed item. And I have read other posts on Forums with similar tales ref the SOCs. If I sold that user the battery, it is up to me to sort it. That costs time and money for me as well as inconvinence for the user.
I mentioned a problem with a KS Energy battery. Owner has constant issues and has resorted finally to leaving the Victron Inverter I fitted on so there is enough load to stop the battery falling asleep. That is not how it should be. He has tried to get KS Energy to look into it but they are not interested. He wants to get more battery power also, but you can be sure it won't be another KS Energy battery joining the first! Again, if it were me who supplied that battery, it would be down to me to sort it.
And a key thing with Batteries .... if they need to get shipped, they are a bugger to courier. Only a limited number of couriers are willing/licensed to take them (I think they are classified as dangerous or explosive?) and it is expensive compared to anything else.

I won't deny the Polarmax is pricey. It is competing with a higher tier of battery than the Fogstar and Roamer. It is more comparable to say the Relion or Battleborn units.
The Explorer Base battery you mentioned is a nice battery. It lacks the integral heaters and it lacks the Bluetooth BMS. But for a typical user, neither are essential and actually the Bluetooth BMS can just add confusion quite often. I installed the 300Ah Base unit a few months ago along with a raft of Victron kit from a Multiplus at the start all the way to Victron panels on the roof. I briefly considered Roamer or Fogstar for this install, but wanted the known quantity of a brand I trusted and with an otherwise Victron Install, I wanted something with the same level of quality (I would like to try Victron Batteries sometime but they are just too much cash ).
Are they are bettery brand? They are certainly more established and from a supplier with many decades in the business, so that is a factor for me.

Funny enough, I have had more Victron kit fail on me than I have had batteries fail . But any products can fail, and Victron is no different to any other except it tends to be a much rarer occurance and Victron tend to manage the RMAs so as a Installer it is less hassle.

And the other factor is WHY are you buying something and what happens if it fails?
I bought and installed an Eberspacher many years ago and it was very good. Those chinese diesel heaters you get now are around 1/6th the price and the last Diesel heater I installed on my camper was one of those. And one I installed for a friend was fine. But I would NEVER EVER install one for anyone commercially because they can be poor quality. It took me 3 goes to get one that worked correctly in my van. Nothing to do with the installation; all down to the supplied kit.


PS. You mention my interest in the cross-battery balancing? It is something I look at quite carefully now as I have had issues previously with paralleled batteries getting out of sync with each other. When this starts, it does tend to get worse and you can get into a situation where you no longer have full capacity available to you. It is not life-threatening or an amazingly critical thing, but you want and exxpect batteries to be used pretty equally really, don't you?
It happens on Lead as well if you get a weak battery which is affecting the others in the bank. When you have batteries in Series, it is fairly easy to install external battery balancers to keep everything aligned, but in Parallel it is impossible to do, unless the batteries themselves support it. IIRC, the Victron Smart Batteries will keep themselves all in sync with comms between them. I don't know if you ever came across them, but the Valence U-Charge battery I think had good inter-battery communications as well. These were quite popular on the used market when Lithiums were starting around the £900-£1000 for a 100Ah unit. I never got round to trying one, but people I know who did seemed happy with them (although I don't think anyone ever managed to get the inter-battery comms cables!).
The Polarmax is the first battery I have tried myself where the balance between the batteries have been nigh on perfect. They may drift a little when supplying heavy leads or under fast charging as every battery made is slightly different to another and all balancing is at low current, but they will correct themselves when under rest.


If I were buying a battery for myself, then maybe would be tempted to get a Fogstar as they do look very good value for money, but I would probably go all the way and just build my own if I wanted to experiment
(But while I like to fiddle around and monitor all my electrics indeed, I also want them all to work flawlessly when I am away camping).
FWIW, I would look at Fogstar before Roamer generally if those were the only two option in town

 

[Gromett]

My take is that I would not want to deal with returns on anything I supply. For ANY products.
So I avoid unknowns. And I avoid stuff I know people have had issues with that should just not be there. Product failure is unfortunate but it happens. Design Faults and poor QC can be a nightmare!

So take that sister thread here about hassles with a Roamer (I think) where the SOC shifts around for no reason and the cycle count has jumped to 7000+ randomly. That has got to be a failed item. And I have read other posts on Forums with similar tales ref the SOCs. If I sold that user the battery, it is up to me to sort it. That costs time and money for me as well as inconvinence for the user.
I mentioned a problem with a KS Energy battery. Owner has constant issues and has resorted finally to leaving the Victron Inverter I fitted on so there is enough load to stop the battery falling asleep. That is not how it should be. He has tried to get KS Energy to look into it but they are not interested. He wants to get more battery power also, but you can be sure it won't be another KS Energy battery joining the first! Again, if it were me who supplied that battery, it would be down to me to sort it.
And a key thing with Batteries .... if they need to get shipped, they are a bugger to courier. Only a limited number of couriers are willing/licensed to take them (I think they are classified as dangerous or explosive?) and it is expensive compared to anything else.

I won't deny the Polarmax is pricey. It is competing with a higher tier of battery than the Fogstar and Roamer. It is more comparable to say the Relion or Battleborn units.
The Explorer Base battery you mentioned is a nice battery. It lacks the integral heaters and it lacks the Bluetooth BMS. But for a typical user, neither are essential and actually the Bluetooth BMS can just add confusion quite often. I installed the 300Ah Base unit a few months ago along with a raft of Victron kit from a Multiplus at the start all the way to Victron panels on the roof. I briefly considered Roamer or Fogstar for this install, but wanted the known quantity of a brand I trusted and with an otherwise Victron Install, I wanted something with the same level of quality (I would like to try Victron Batteries sometime but they are just too much cash ).
Are they are bettery brand? They are certainly more established and from a supplier with many decades in the business, so that is a factor for me.

Funny enough, I have had more Victron kit fail on me than I have had batteries fail . But any products can fail, and Victron is no different to any other except it tends to be a much rarer occurance and Victron tend to manage the RMAs so as a Installer it is less hassle.

And the other factor is WHY are you buying something and what happens if it fails?
I bought and installed an Eberspacher many years ago and it was very good. Those chinese diesel heaters you get now are around 1/6th the price and the last Diesel heater I installed on my camper was one of those. And one I installed for a friend was fine. But I would NEVER EVER install one for anyone commercially because they can be poor quality. It took me 3 goes to get one that worked correctly in my van. Nothing to do with the installation; all down to the supplied kit.


PS. You mention my interest in the cross-battery balancing? It is something I look at quite carefully now as I have had issues previously with paralleled batteries getting out of sync with each other. When this starts, it does tend to get worse and you can get into a situation where you no longer have full capacity available to you. It is not life-threatening or an amazingly critical thing, but you want and exxpect batteries to be used pretty equally really, don't you?
It happens on Lead as well if you get a weak battery which is affecting the others in the bank. When you have batteries in Series, it is fairly easy to install external battery balancers to keep everything aligned, but in Parallel it is impossible to do, unless the batteries themselves support it. IIRC, the Victron Smart Batteries will keep themselves all in sync with comms between them. I don't know if you ever came across them, but the Valence U-Charge battery I think had good inter-battery communications as well. These were quite popular on the used market when Lithiums were starting around the £900-£1000 for a 100Ah unit. I never got round to trying one, but people I know who did seemed happy with them (although I don't think anyone ever managed to get the inter-battery comms cables!).
The Polarmax is the first battery I have tried myself where the balance between the batteries have been nigh on perfect. They may drift a little when supplying heavy leads or under fast charging as every battery made is slightly different to another and all balancing is at low current, but they will correct themselves when under rest.


If I were buying a battery for myself, then maybe would be tempted to get a Fogstar as they do look very good value for money, but I would probably go all the way and just build my own if I wanted to experiment
(But while I like to fiddle around and monitor all my electrics indeed, I also want them all to work flawlessly when I am away camping).
FWIW, I would look at Fogstar before Roamer generally if those were the only two option in town

Thanks for that very comprehensive answer. I can see you are coming at it from a different angle to me. I wasn't thinking about selling on or installing for others. If I was then I wouldn't be quite so price concious to be honest and would be looking at the RMA and support side more closely. Usually if something is within 10 or even 20% I will pick the better one. But when the prices difference is almost double then I think twice. Batteries and and as you point out diesel heaters are prime examples of this.

I am not really sure how the parallel multi battery balancing communication is important though. In parallel if one battery gets 0.1V above another then surely they would self balance. With the BMS taking care of ensuring all the cells within each battery are in balance. In a series configuration though I can see that the inter battery communication would be vital as you need the same cell voltage across all 4 cells in all 4 batteries.

 

[Hoovie]

Thanks for that very comprehensive answer. I can see you are coming at it from a different angle to me. I wasn't thinking about selling on or installing for others. If I was then I wouldn't be quite so price concious to be honest and would be looking at the RMA and support side more closely. Usually if something is within 10 or even 20% I will pick the better one. But when the prices difference is almost double then I think twice. Batteries and and as you point out diesel heaters are prime examples of this.

I am not really sure how the parallel multi battery balancing communication is important though. In parallel if one battery gets 0.1V above another then surely they would self balance. With the BMS taking care of ensuring all the cells within each battery are in balance. In a series configuration though I can see that the inter battery communication would be vital as you need the same cell voltage across all 4 cells in all 4 batteries.

You would think they would self-balance with current transferring from one to another as the voltages equalise. But it doesn't tend to happen I agree that makes sense that it should, but why it doesn't happen I can't explain.

But the trouble then starts when charging or discharging and in a similar way to a Lithium battery with unequal/unbalanced cells causing individual cells to error when they are over voltage even though the external charge voltage is within range, it is possible for an 'unequal' battery to affect the charger mode, or to shut down if very low on a discharge and stay off when the charger is enabled as the other battery (which will be low as well, just not as low) is sucking up all the charge power and the balance gets worsened.
It becomes a bit of a nightmare trying to sort this out and get batteries back on track!

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[Gromett]

You would think they would self-balance with current transferring from one to another as the voltages equalise. But it doesn't tend to happen I agree that makes sense but why it doesn't happen I can't explain.

But the trouble then starts when charging or discharging and in a similar way to a Lithium battery with unequal/unbalanced cells causing individual cells to error when they are over voltage even though the external charge voltage is within range, it is possible for an 'unequal' battery to affect the charger mode, or to shut down if very low on a discharge and stay off when the charger is enabled as the other battery (which will be low as well, just not as low) is sucking up all the charge power and the balance gets worsened.
It becomes a bit of a nightmare trying to sort this out and get batteries back on track!

I have never heard of this happening to anyone. I will have to take your word that it is an issue as you deal with this. I can't understand how it happens or why and that I do not like. Strange...

 

[Hoovie]

I have never heard of this happening to anyone. I will have to take your word that it is an issue as you deal with this. I can't understand how it happens or why and that I do not like. Strange...

Strange indeed. But not an isolated incident. I never got to the bottom of it either. But you can see why this specific thing became of interest to me and a point to check

 

[Gromett]

I saw a tear down of the fogstar batteries some time ago and I was fairly impressed with the build quality and construction with only a few minor quibbles. Here is the video again in case anyone hasn't seen it. I have also put another one of his videos where he compares it to the eco-worthy battery. I haven't been able to find a tear down of a Roamer battery sadly.

 

[Raul]

Gromet,

The battery in principle it’s ok, the bms it’s pasive balance via resistor bleeding the high cell. This is all good IF, the pack is assembled by matched cells, balanced and fully charged at first cycle. With matched cells, it is expected that cells remain in balance, and only minor corrections will be dealt by the bms. Unfortunately, this is not the case. Many batteries end up unbalanced and unmatched cells, right from the start. Because we want it now, fast and cheap,so things has to give. No free lunch.
More expensive batteries have better design, better bms, and better cells. Buying power dictates who gets better cells. Most of this prismatic are EV traction rejects, reclassified for storage grade.
Now cylindrical lfp are different, they were not meant for EV in the first place.

 

[Gromett]

Now cylindrical lfp are different, they were not meant for EV in the first place.

Not going to argue with you on the rest of it. But your take on the packaging is wrong. Tesla only use cylindrical and it has major advantages for automotive use over prismatic.

^{_{Subscribers  do not see these advertisements}}

 

[Raul]

Each prismatic cell will produce more heat, but there's less of them. So the total heat the battery produces will be roughly the same. Same chemistry. And like I said, they're in similar external boxes, so the cooling ability will be about the same. I bet they end up being roughly the same temperature overall.

Nonsense, it’s not by cell count but volume. Take one prismatic, and 10 cylindrical equal volume and capacity- 100ah prismatic against 10x 10ah cylindrical. The cilindriacal’s will have grater surface area. The rest is simple physics of energy conservation and thermodynamics. Greater surface area will dissipate more heat.

 

[Raul]

Not going to argue with you on the rest of it. But your take on the packaging is wrong. Tesla only use cylindrical and it has major advantages for automotive use over prismatic.

Tesla lfp?

 

[Gromett]

Tesla lfp?

Yes. Also chemistry and packaging are not directly linked. one does not infer the other.

 

[Gromett]

Nonsense, it’s not by cell count but volume. Take one prismatic, and 10 cylindrical equal volume and capacity- 100ah prismatic against 10x 10ah cylindrical. The cilindriacal’s will have grater surface area. The rest is simple physics of energy conservation and thermodynamics. Greater surface area will dissipate more heat.

Not correct. The same chemistry will result in the same amount of heat generated. A cylindrical cells heat is spread over a larger area resulting in a lower spot temperature.

The main difference between prismatic and cylindrical is this;
A cylindrical cell has a lower energy density but is able to release it's energy faster.
A prismatic cell has a higher density but cannot release it's energy as fast.

Cylindricals are also easier/faster/cheaper to manufacture once you crack it.

 

[Guigsy]

Nonsense, it’s not by cell count but volume. Take one prismatic, and 10 cylindrical equal volume and capacity- 100ah prismatic against 10x 10ah cylindrical. The cilindriacal’s will have grater surface area. The rest is simple physics of energy conservation and thermodynamics. Greater surface area will dissipate more heat.

Roughly the same volume of cells. All in the same box. Total amount of heat produced will be roughly the same. Just the cylindrical cells might warm the trapped air inside a bit quicker.

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