LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

[CharlieJ]

@newhaul #7229

A cautionary note: Denis didn't recommend charging much below freezing and he provided no hard number for charging as a function of battery capacity below freezing . He was describing the electrochemical process and the affect of cold temperature on it.

[evm1024]

Originally Posted by john61ct

SNIP %<

And I'm not claiming BB is not a great choice for some use cases, just not mine, not for me.

If I learned A123 was their OEM maybe, but they're probably K2 or Liitokala, or even Full River, meh.

I like Battleborn and might buy one.

I really want to take advantage of your knowledge and insights.

Please tell me of your use case and why that disqualifies Battleborn.

Also, can you explain why K2 and Lithokala are inferior to A123? And Headway for that matter. I'm going to spend some money soon and really would be glad to see the information that you base your opinion on before I buy some Headway cells.

[newhaul]

Originally Posted by CharlieJ

@newhaul #7229

A cautionary note: Denis didn't recommend charging much below freezing and he provided no hard number for charging as a function of battery capacity below freezing . He was describing the electrochemical process and the affect of cold temperature on it.

as I stated it is actually of little to no consequence for our house banks the charge rate alone is rarely if ever is over .3C .
And if out batteries are below freezing there really is no reason to charge them due to the boat being in winter layup.
Those of us that liveaboard well I like my living space about 68℉ so batteries are not much below 55℉ ( at least on my boat they are going to be mounted below the sole on top of my keel).

[Dockhead]

Originally Posted by evm1024

I like Battleborn and might buy one.
.

Note that these are rated at 2C discharge for 30 seconds, which means a $2000 pair of 100 amp BB's would only give you enough power for a bow thruster drawing 200 amps @ 24v nominal, which is a pretty tiny bow thruster. Mine needs about 500 amps, or maybe closer to 400 amps if there is less voltage sag like with LiFePo.



If you have to use a dedicated thruster bank, then this is the very use case for AGM starter batteries, which can be discharged for short periods at 6C or whatever, and should be quite a bit cheaper.



Lithium would be good for bow thruster but only if you can connect to a larger house bank. This was actually a limiting factor in sizing my bank. I decided it shouldn't be smaller than about 300 AH @ 24v in order to keep the discharge rate when using the bow thruster as close to 1C as possible (the battery power is supplemented by power from a 100 amp alternator).

[john61ct]

If you purpose build a LFP pack from top-notch cells as a high-power bank dedicated to bowthruster, windlass winches etc

using appropriate wiring etc

I does not need to be huge, can safely can go 3-5C for even 20min or more, and if otherwise coddled, will likely get full rated life cycles or near. Supported by ICE input even better,

Of course it needs to have the Ah for the runtime without dropping much below say 2.8V under load bouncing back to 3+V at rest,

and a bigger bank would be better and give longer service.

This could also act as a redundant "Reserve" of sorts to House, for other essential circuits in a pinch, even as Starter.

[evm1024]

Originally Posted by Dockhead

Note that these are rated at 2C discharge for 30 seconds, which means a $2000 pair of 100 amp BB's would only give you enough power for a bow thruster drawing 200 amps @ 24v nominal, which is a pretty tiny bow thruster. Mine needs about 500 amps, or maybe closer to 400 amps if there is less voltage sag like with LiFePo.



If you have to use a dedicated thruster bank, then this is the very use case for AGM starter batteries, which can be discharged for short periods at 6C or whatever, and should be quite a bit cheaper.



Lithium would be good for bow thruster but only if you can connect to a larger house bank. This was actually a limiting factor in sizing my bank. I decided it shouldn't be smaller than about 300 AH @ 24v in order to keep the discharge rate when using the bow thruster as close to 1C as possible (the battery power is supplemented by power from a 100 amp alternator).

The Battleborn is fine for my use case but more than twice the cost of what I'l exploring. Driving a big thruster is not in Battleborn's niche.

I'll start a new thread when I get a bit further along.

[Dockhead]

Originally Posted by evm1024

The Battleborn is fine for my use case but more than twice the cost of what I'l exploring. Driving a big thruster is not in Battleborn's niche.

I'll start a new thread when I get a bit further along.

OK, look forward to it.


You can make it work of course, but why? Dedicated thruster batteries are NOT a deep discharge use -- this is a use case more like a starting battery. So lithium doesn't really give any advantage besides low voltage sag. You would not be using any of the other advantages of lithium.


Now if you could connect the bow thruster to a lithium house bank, that's a different story. And that's what I'm going to do.

[CatNewBee]

There are small and very powerful Li start batteries without BMS that can be used for the bow thruster application.

But back to the initial discussion.

I would also opt out batteries built from cylindric cells and drop-ins for some reason.

Lets start with the massive parallel cylindrical configurations. There are 2 flafor of them, without cell fuses and with cell fuses. Without cell fuses in case of a cell short all neghbof cell will discharge their energy to the single cell with a catastrophic bang, not good. Batteries with cell fuses would blow the single cell out of the circuit, and only the energy of the single cell will discharge over the short, so still some heat for a while, deformation and maybe side effects to neighbor cells, but not that violent. Dead cells, disconnected cells etc will slowly start degrading the pack, the other cells will have higher charge and discharge loads, degradation will then quickly increase as more cells fail, finally the designed current distributed ver many cells concentrates on the few remaining causing a cascading blow of the remaining cell fuses and a total loss of the pack.

Batteries with single cells in serial configuration are easier managable, and a failing cell is identifiable and replaceable.

Now to the drop ins with BMS. I don't like them either. First, the BMS AND THE DISCONNECT LOGIC are inside and predefined by the manufacturer to a specific purpose that may be different to yours. The BMS and the Logic are powered by the pack, means you cannot store it for a long time offline, the logic will drain and destroy the cells if not physically disconnected from the cells. BMS, balancer and FET produce heat inside the pack, what is counterproductive for battery life. Settings of the BMS cannot be configured by the user, you rely on the smartness of the manufacturer, over current, over voltage may wreck the electronics, especially in serial configurations for higher system voltages with imbalanced packs. The currents are limited way below the capability of the cells. You pay a lot of money for less performance, shorter life, unrepairable electronics and batteries. They are a feel good pack if you consider them disposable easy to manage commodity, like in business applications in health care, military, police etc. where TCO is not a factor and you have tax payers or insurance money at your disposal. This batteries there are sized and built for purpose, for the specific device. They are not general purpose batteries meant to be combined in different combinations in series or parallel. And they usually are meant to be online or in use 24/7 once activated, not stored for a long period of time offline, and to be routinely replaced.

[GoneDiving]

Originally Posted by CatNewBee

I would also opt out batteries built from cylindric cells and drop-ins for some reason.

Lets start with the massive parallel cylindrical configurations.

Batteries with cell fuses would blow the single cell out of the circuit, and only the energy of the single cell will discharge over the short, so still some heat for a while, deformation and maybe side effects to neighbor cells, but not that violent. Dead cells, disconnected cells etc will slowly start degrading the pack, the other cells will have higher charge and discharge loads, degradation will then quickly increase as more cells fail, finally the designed current distributed ver many cells concentrates on the few remaining causing a cascading blow of the remaining cell fuses and a total loss of the pack.

Batteries with single cells in serial configuration are easier managable, and a failing cell is identifiable and replaceable.

This is correct but only really applicable to to the extreme user operating at the full capacity of their pack.

If a cell dies in my dive scooter, with 10 cells in parrallel, that routinely discharges at >1C, it will be immediately noticable and (as you said) detrimental to the other cells in the parrallel string if it is continues to be used.

I doubt the average Tesla driver would notice the isolation of 1 of 72 cells on their drive to work and the other cells would easily cope with a 1.5% increase in load.

It could be argued that the best battery is the one that needs no management. Obviously, this is a pipe dream but with careful engineering and component selection is nearly possible. The scooter mentioned above has no BMS so I was paranoid about voltage drift and cell balance when I first got it. 8 years later all cells are +/- 0.1v and it still takes a beating. 😁

I say this not to promote one cell or architecture over another but just to highlight that proper selection and forethought can save a lot of heart ache down the road

Cheers.

[Pete7]

Originally Posted by john61ct

But I would be skeptical about them preventing swelling without any compression plate / strapping.

John posted the above, but I am skeptical of his advice as he doesn't provide personal or linked data to back up his ideas.

So what is the concensus on this LFP strapping/case requirement to prevent swelling? is it a real problem that is going to happen or just someones off the cuff idea?

I note that Battleborn and Winston cells have ridged cases that seem to allow an air gap. Is allowing cooling around the cells more important than mounting them in a case? Seem to remember Will Prowse just tapes them together with double sided sticky tape and a strap to stop them moving about in use.


Pete

[rgleason]

Revelation: No LiFePo as a bank. Therefore I do not understand some of the nuances of the the systems or technology. (In fact, Mainesail advised LiFePo is not cost effective for my boat at this point in time.) I am however preparing as the wallet allows.

I believe Ethan [Evm1024] did have a thread on Lifepo for windless awhile ago.
http://www.cruisersforum.com/forums/...ss-129837.html

Perhaps that discussion thread could be continued? Here is a search of Evm1024's other threads which might be useful because his posting are generally very informative and topical.

[evm1024]

Originally Posted by rgleason

Revelation: No LiFePo as a bank. Therefore I do not understand some of the nuances of the the systems or technology. (In fact, Mainesail advised LiFePo is not cost effective for my boat at this point in time.) I am however preparing as the wallet allows.

I believe Ethan [Evm1024] did have a thread on Lifepo for windless awhile ago.
http://www.cruisersforum.com/forums/...ss-129837.html

Perhaps that discussion thread could be continued? Here is a search of Evm1024's other threads which might be useful because his posting are generally very informative and topical.

Thanks, where do I send the money?

That thread is a blast from the past for sure.

The echo charge was not viable - I bought 2 and did a bunch of reverse engineering on one. Pretty much a dead end.

However, Victron and others buck-boost DC to DC charger/power supplies are much more on what I was looking into then and now.

[john61ct]

I've been collecting old echo-charge units as they come up cheap, anyone with some they don't want send me a PM.

Also Blue Sea CL series ACRs (BatteryLink, PN 7600), getting rarer these days.

[Maine Sail]

Originally Posted by Pete7

So what is the concensus on this LFP strapping/case requirement to prevent swelling? is it a real problem that is going to happen or just someones off the cuff idea?

Manufacturers such as Winston require cell compression/strapping and sell heavy duty aluminum end boards and the strapping for this.

This cell was out of a Mastervolt MLI battery that had no cell compression on the lower bout of the cells, which is exactly where they bulged.





There was a compression bar near the top of the cells but none at the bottom where they bulged..

[john61ct]

Yes it's a lot of force, seen people woefully fail trying to use even thick plywood.

Even thick aluminium plate can be found reasonably priced at yards in metro areas, not hard to cut.

For those who think effort in extra intra-bank cooling is worthwhile (I don't for House banks), put plates between each cell with short "wings" extending out say 2" past the cell sides (not up in height, stay below the case height!)

to act as heat sinks

and maybe thermostatically switch on computer-style fans at 30°C post temp.

But crazy overkill for a non problem IMO.