Lithium battery abuse

[mrsmelly]

48 minutes ago, Dr Bob said:

Young?

Young.......................? I hit the big two score and ten in April! Have you got the Noodles yet?

 

Yeah, I know your ancient lol, just thought I would rub it in, you are even older than my missus 🤣

The noodles are a con mate, that bloomin Rose has buggered off with them 

[Dr Bob]

3 minutes ago, mrsmelly said:

Yeah, I know your ancient lol, just thought I would rub it in, you are even older than my missus 🤣

The noodles are a con mate, that bloomin Rose has buggered off with them 

Tell me about it!

I bet Auntie Waitrose will be adding them to her list to auction in a few days. Hope there are a few trees still standing in Welsh Wales.

[mrsmelly]

1 minute ago, Dr Bob said:

Tell me about it!

I bet Auntie Waitrose will be adding them to her list to auction in a few days. Hope there are a few trees still standing in Welsh Wales.

Ive only been as far as the pub. There is no telly or mobile fone reception, bloomin big mast thing has come down lol. Still, my wifi works so there is tinternet and net flix stuff. No property damage where we are. We are sheltered half way oop an ill, in a valley.

[Mike Todd]

1 hour ago, Dr Bob said:

Maths was never my strong point. I lied. It was three..

After your (justified) comment on safety, I am horrified to hear an engineer admit to failings in maths. In almost all situations, a good dose of maths underpins all of the design calculations - sometimes quite complex. A  casual approach to the maths can lead to all sorts of issues -especially with a misplaced decimal point! (Or mixed units) Miscounting scores could create a problem in claiming certain benefits!

 

Pots and kettles come to mind . . . 

[Dr Bob]

29 minutes ago, Mike Todd said:

After your (justified) comment on safety, I am horrified to hear an engineer admit to failings in maths. In almost all situations, a good dose of maths underpins all of the design calculations - sometimes quite complex. A  casual approach to the maths can lead to all sorts of issues -especially with a misplaced decimal point! (Or mixed units) Miscounting scores could create a problem in claiming certain benefits!

 

Pots and kettles come to mind . . . 

Me?

I'm a Chemist. We employ engineers to do the maths.

[peterboat]

5 hours ago, Dr Bob said:

Think about it. Your set up is

Step 1, charge to 80-90% not 100%

Step 2, solar controller backs its power off when it gets to target current

Step 3, the battery manufacturers own BMS can isolate/balance in an emergency

 

That is 2 steps better than charge to 14.0V and ask the cheapo chinese board to isolate as a routine.

At least I'm getting there after Mrs Bob

 

5 hours ago, TheBiscuits said:

 

I thought @peterboat didn't have the Valence master BMS that does the charge disconnect? 

 

The other thing is, you are using cheap (and also expensive) Chinese circuits to keep yours safe.

 

You just have multiple layers of redundancy and actively manage your bank personally.  Would you fit your system to a hireboat, or lend Stuck-Fa-Coin out to family with the lithiums in circuit? 

 

I do strongly agree that you have a higher duty of care if your company are destruct testing lithium batteries.  You qualify as someone who "ought to know better" as the court ruled about the gasfitter on the Arniston deaths.

 

 

No disconnect on my BMS, I rely on the midnite controller turning off, the genny alternator has long cables and it doesn't get above 28 volts so I watch the meter, not that I use it much 

[MtB]

4 hours ago, Dr Bob said:

Me?

I'm a Chemist.

 

Excellent. You might be able to help in this thread then!

 

 

[Dr Bob]

44 minutes ago, MtB said:

 

Excellent. You might be able to help in this thread then!

 

 

Not that sort of Chemist Duh!

......but Auntie Waitrose's answer was pretty spot on. Trying to avoid the trivialities of this forum.

[nicknorman]

9 hours ago, Dr Bob said:

 

Step 1. Aim normally to charge to 80% not 100% (ie 13.8V not 14.0V) to keep well clear of the critical zone

 

Obviously I agree with the general point of having at least 2 levels of safety. I just want to pick up on your point above. One cannot correlate charge voltage with SoC. If you charge very slowly, 13.8v will get you to about 99% SoC. If you charge very fast, when you hit 13.8v maybe you are as low as 80% but I think it would have to be very fast as in 1C. Our alternator in slow charge mode gives about 95A into the 600Ah, ie about C/6. It takes a long time for the voltage to get over 13.6 and by the time it is 13.8v the SoC is about 95%. So (depending on how fast you charge) I suspect that actually you are charging to quite a lot more than 80% if you charge until the voltage hits 13.8v.

 

Just on the safety point are there actually many examples of LiFePO4 cells going on fire/exploding or whatever? I thought the general feeling was that they were pretty stable and robust compared to other chemistries and the danger was more to the wallet than to life and limb.

[peterboat]

15 minutes ago, nicknorman said:

Obviously I agree with the general point of having at least 2 levels of safety. I just want to pick up on your point above. One cannot correlate charge voltage with SoC. If you charge very slowly, 13.8v will get you to about 99% SoC. If you charge very fast, when you hit 13.8v maybe you are as low as 80% but I think it would have to be very fast as in 1C. Our alternator in slow charge mode gives about 95A into the 600Ah, ie about C/6. It takes a long time for the voltage to get over 13.6 and by the time it is 13.8v the SoC is about 95%. So (depending on how fast you charge) I suspect that actually you are charging to quite a lot more than 80% if you charge until the voltage hits 13.8v.

 

Just on the safety point are there actually many examples of LiFePO4 cells going on fire/exploding or whatever? I thought the general feeling was that they were pretty stable and robust compared to other chemistries and the danger was more to the wallet than to life and limb.

I charge relatively slowly on solar, it hits 13.9 drops to 13.6 absorb then 13.4 float, absorb can be be for only a few minutes if sunny, float really is float 0 amps going in. Expensive solar controllers are worth the money when expensive batteries are at risk. 

[Naughty Cal]

9 hours ago, nicknorman said:

Obviously I agree with the general point of having at least 2 levels of safety. I just want to pick up on your point above. One cannot correlate charge voltage with SoC. If you charge very slowly, 13.8v will get you to about 99% SoC. If you charge very fast, when you hit 13.8v maybe you are as low as 80% but I think it would have to be very fast as in 1C. Our alternator in slow charge mode gives about 95A into the 600Ah, ie about C/6. It takes a long time for the voltage to get over 13.6 and by the time it is 13.8v the SoC is about 95%. So (depending on how fast you charge) I suspect that actually you are charging to quite a lot more than 80% if you charge until the voltage hits 13.8v.

 

Just on the safety point are there actually many examples of LiFePO4 cells going on fire/exploding or whatever? I thought the general feeling was that they were pretty stable and robust compared to other chemistries and the danger was more to the wallet than to life and limb.

Battleborne claim that their lithium 12v batteries can be held at a float charge of up to 14.6v for up to 3 weeks with no damage to the cells. 

 

Not sure why anyone would have a float charge voltage set quite so high though.

 

On longer runs our Sterling lithium sits happily at 14.2v for a few hours at a time. It has not decided to spontaneously combust yet.

[nicknorman]

18 minutes ago, Naughty Cal said:

Battleborne claim that their lithium 12v batteries can be held at a float charge of up to 14.6v for up to 3 weeks with no damage to the cells. 

 

Not sure why anyone would have a float charge voltage set quite so high though.

 

On longer runs our Sterling lithium sits happily at 14.2v for a few hours at a time. It has not decided to spontaneously combust yet.

Seems unlikely since the say charge at up to 14.6v with an absorb time of 20 mins. Can you link to the source of your information?

in my opinion, holding at 14.2 for a few hours will shorten the battery life. Of course you are starting off with a very long life so maybe eg halving the life doesn’t matter.

[Alistair1357]

I don't know where 14V comes into a "dangerous" zone in the case of my Winston cells - The supplier recommends a maximum charge of 4V per cell which is 16V if I understand maths correctly? 

 

https://files.gwl.eu/inc/_doc/attach/StoItem/3861/ThunderSky-Winston-LIFEPO4-100Ah-WIDE-Datasheet.pdf

[Naughty Cal]

16 minutes ago, nicknorman said:

Seems unlikely since the say charge at up to 14.6v with an absorb time of 20 mins. Can you link to the source of your information?

in my opinion, holding at 14.2 for a few hours will shorten the battery life. Of course you are starting off with a very long life so maybe eg halving the life doesn’t matter.

It's in the link below in the comments section below the main article. 

 

https://battlebornbatteries.com/charging-battleborn-lifepo4-batteries/

 

If we get 6 years from the Sterling then it will have been better value than lead acid batteries. Any longer is just a bonus.

Edited February 20, 2022 by Naughty Cal

[nicknorman]

56 minutes ago, Naughty Cal said:

It's in the link below in the comments section below the main article. 

 

https://battlebornbatteries.com/charging-battleborn-lifepo4-batteries/

 

If we get 6 years from the Sterling then it will have been better value than lead acid batteries. Any longer is just a bonus.

Yes I found it. Seems surprising and against all perceived wisdom. Everything else in that section talks about a 20 minute absorb and then 13.6v. I’d say it’s a rogue comment bearing in mind the chemistry of their cells is the same as everyone else’s.

[MtB]

1 hour ago, Alistair1357 said:

I don't know where 14V comes into a "dangerous" zone in the case of my Winston cells - The supplier recommends a maximum charge of 4V per cell which is 16V if I understand maths correctly? 

 

https://files.gwl.eu/inc/_doc/attach/StoItem/3861/ThunderSky-Winston-LIFEPO4-100Ah-WIDE-Datasheet.pdf

 

I haven't read the data sheet yet but received wisdom is it is fine to charge at whatever voltage you can persuade your charger to deliver but once you get to to approaching 100% SoC, you must stop charging. NOT carry on at a float voltage.

 

 

[nicknorman]

1 hour ago, Alistair1357 said:

I don't know where 14V comes into a "dangerous" zone in the case of my Winston cells - The supplier recommends a maximum charge of 4V per cell which is 16V if I understand maths correctly? 

 

https://files.gwl.eu/inc/_doc/attach/StoItem/3861/ThunderSky-Winston-LIFEPO4-100Ah-WIDE-Datasheet.pdf

Winston cells are not normal LiFePO4. They have yttrium as well. They have a slightly higher max charge and a higher max discharge voltage.

[MtB]

1 hour ago, Alistair1357 said:

I don't know where 14V comes into a "dangerous" zone in the case of my Winston cells - The supplier recommends a maximum charge of 4V per cell which is 16V if I understand maths correctly? 

 

https://files.gwl.eu/inc/_doc/attach/StoItem/3861/ThunderSky-Winston-LIFEPO4-100Ah-WIDE-Datasheet.pdf

 

 

Ok, this is a good example of how technical requirements can be misinterpreted. That's not quite what the data sheet actually says is it? I quote:

 

"Maximal charge voltage 4 V The cells is damaged if voltage exceeds this level"

 

If you follow the link on the data sheet to the Thundersky website, the page for your battery says:

 

"Recommended initial and subsequent charging is to 3.65 V."

 

 

[nicknorman]

4 minutes ago, MtB said:

 

Ok, this is a good example of how technical requirements can be misinterpreted. That's not quite what the data sheet actually says is it? I quote:

 

"Maximal charge voltage 4 V The cells is damaged if voltage exceeds this level"

 

If you follow the link on the data sheet to the Thundersky website, the page for your battery says:

 

"Recommended initial and subsequent charging is to 3.65 V."

 

Good point! As we have seen so often on here and elsewhere, people instinctively read into something what they want to see, not what the writer intended.

[MtB]

1 minute ago, nicknorman said:

Good point! As we have seen so often on here and elsewhere, people instinctively read into something what they want to see, not what the writer intended.

 

 

Not only that, but they then propagate their misunderstanding as fact, using authoritative language.

 

Alistair1357 says his supplier "recommends" charging at 4.00V when they absolutely did not, they gave 4.00V as an absolute maximum cell voltage above which the cells would be damaged. Different thing.

 

The Thundersky recommended charge voltage is 3.65.

[Alistair1357]

12 minutes ago, MtB said:

 

 

Not only that, but they then propagate their misunderstanding as fact, using authoritative language.

 

Alistair1357 says his supplier "recommends" charging at 4.00V when they absolutely did not, they gave 4.00V as an absolute maximum cell voltage above which the cells would be damaged. Different thing.

 

The Thundersky recommended charge voltage is 3.65.

Please do not ascribe bullshit to my name. Read my post carefully. Then, if you wish to quote what I said; you can cut and paste exactly what I said.

[MtB]

2 minutes ago, Alistair1357 said:

Please do not ascribe bullshit to my name. Read my post carefully. Then, if you wish to quote what I said; you can cut and paste exactly what I said.

 

Ok.

 

2 hours ago, Alistair1357 said:

The supplier recommends a maximum charge of 4V per cell which is 16V if I understand maths correctly? 

 

As demonstrated, your supplier does not recommend 4V per cell.

[peterboat]

3 minutes ago, Alistair1357 said:

Please do not ascribe bullshit to my name. Read my post carefully. Then, if you wish to quote what I said; you can cut and paste exactly what I said.

I read the data sheet it says 4 volts, I fitted a big bank of these last year can't remember what we balanced them at, but if the sheet said 4 volts that is what we would have done 

[Alistair1357]

I can't understand pigheadedness - the term "maximum" is what is you're missing MtB. None of your replies include that. You choose to ignore it. 

[Alan de Enfield]

7 minutes ago, Alistair1357 said:

I can't understand pigheadedness - the term "maximum" is what is you're missing MtB. None of your replies include that. You choose to ignore it. 

 

Surely 'maximum' means that it is OK to do that (example : 70mph maximum on a motorway ?) and you can do 'the maximum' continuously.

The motorway signs do not say you should drive at 65mph - but - you can occasionally creep it up to 70 mph.