Lithium battery abuse

[MarkH2159]

11 hours ago, Dr Bob said:

 

The comments that some uniformed people make on here is mindblowing. Where do you get that information from? At best it is misleading and at worst DANGEROUS! If you had said 'mostly safe and happy under 90%' then I would agree.

 

See the following link to a thread posted 3 years ago. At that time there was certianly not enough data to support your claim. Our company has been working on the thermal runaway issues since then (and including LiFePO4 cells) helping develop a pre theremal runaway warning technique. I consider myself a technical expert on this type of battery chemistry, even if I cant design the electical system to control alternator charge.

 

 

I would recommend MarkH2159 read that thread and the associated links.

 

Anyone considering installing a home brew system of LiFePO4s needs to do a safety assessment on what they are installing and the starting position for that is to as much as possible keep away from 100% charging. I use 90% as my upper limit over which the auto disconnect works and my 'operating proceedure' says only go to 100% when I am personally in manual control of the voltage and current. Keeping LiFePO4s at 90% or below is very very unlikely to present an ignition hazard on well trusted cells (it is not going to happen on a canal boat). The risk is much higher at 99%.

There is very little point in taking these to 99%. The whole idea is that you dont need to fully charge. Why risk safety when thermal runaways are a risk?

Obviously you missed my post where I said I set the BMS is set to cut the charge at a Pack Voltage of 14v and the discharge at 12v,

This keeps the LiFePOs in the safe zone (90% high - 10% low) and that along with regular cycling is all they need.

[Tom and Bex]

This all seems very complicated when you could just have a correctly set up battery monitor and read the SOC at a glance😂

 

Ours gets synchronisation once a month or so, and now it's set up seems to give very accurate readings. Even after leaving synchronisation for 6 weeks it was still accurate to within 5%.

Edited February 17, 2022 by Tom and Bex

[nicknorman]

9 hours ago, MarkH2159 said:

Obviously you missed my post where I said I set the BMS is set to cut the charge at a Pack Voltage of 14v and the discharge at 12v,

This keeps the LiFePOs in the safe zone (90% high - 10% low) and that along with regular cycling is all they need.

I will me mention  that once you go “up the knee” at a low charge current and hit 14v you are at a much higher SoC than 90%. At low charge currents it will be more like 99%.

[Dr Bob]

On 17/02/2022 at 22:42, MarkH2159 said:

Obviously you missed my post where I said I set the BMS is set to cut the charge at a Pack Voltage of 14v and the discharge at 12v,

This keeps the LiFePOs in the safe zone (90% high - 10% low) and that along with regular cycling is all they need.

 

You may have said that but you also said (see below)

 

On 16/02/2022 at 21:45, MarkH2159 said:

 

 

On 16/02/2022 at 22:54, MarkH2159 said:

LiFePO4s are perfectly safe and happy at under 100% charge state.

 

I repeat again, this at best misleading and at worst DANGEROUS. If you are homebrewing a system, you need to be very careful if you are taking LiFePO4s up to 100% (or 99%). Once you are in the voltage knee (95%+) then you are in territory where you need to be in control of what is going on. Mark, you blindly tell the world that they are safe and happy in that regime. For newbies who dont understand, that is DANGEROUS.

How do you know you are not at 100% in one cell. You look at other forums and people will report their cell balance at 3.7V, 3.5V, 3.4V and 3.4V. Is that safe? Of course it isn't. Only someone who didnt have a clue, or a fool would operate like that. You say in one breath that you charge to 90% then in another you say to almost full. Almost full to most uninititated is 99%. In no posts do you say keep away from 100%.

Homebrewing an Li bank needs thought and consideration of what can go wrong and actions that keep the system safe. By buying a 'one stop shop' from a vendor it is different - they have responsibility - but homebrewing is different, you have responsibility.

I have read a previous post of your on another thread (which recieved 4 greenies - so it must be right???????????????) which suggests to me that you dont really understand the main issue with Li's. Can you remind us of how you avoid overcharging? I may have got it wrong and you do fully understand and if so, sorry I mentioned it.

 

 

 

Edited February 19, 2022 by Dr Bob

[peterboat]

16 minutes ago, Dr Bob said:

 

You may have said that but you also said (see below)

 

 

 

I repeat again, this at best misleading and at worst DANGEROUS. If you are homebrewing a system, you need to be very careful if you are taking LiFePO4s up to 100% (or 99%). Once you are in the voltage knee (95%+) then you are in territory where you need to be in control of what is going on. Mark, you blindly tell the world that they are safe and happy in that regime. For newbies who dont understand, that is DANGEROUS.

How do you know you are not at 100% in one cell. You look at other forums and people an people will report their cell balance at 3.7V, 3.5V, 3.4V and 3.4V. Is that safe? Of course it isn't. Only someone who didnt have a clue, or a fool would operate like that. You say in one breath that you charge to 90% then in another you say to almost full. Almost full to most uninititated is 99%. In no posts do you say keep away from 100%.

Homebrewing an Li bank needs thought and consideration of what can go wrong and actions that keep the system safe. By buying a 'one stop shop' from a vendor it is different - they have responsibility - but homebrewing is different, you have responsibility.

I have read a previous post of your on another thread (which recieved 4 greenies - so it must be right???????????????) which suggests to me that you dont really understand the main issue with Li's. Can you remind us of how you avoid overcharging? I may have got it wrong and you do fully understand and if so, sorry I mentioned it.

 

 

 

He has a BMS on it Bob that balances and disconnects the charge and discharge 

[Dr Bob]

2 minutes ago, peterboat said:

He has a BMS on it Bob that balances and disconnects the charge and discharge 

Yes Pete, I understand that, but what else? What other precautions is he taking?

[TheBiscuits]

18 minutes ago, Dr Bob said:

Yes Pete, I understand that, but what else? What other precautions is he taking?

 

Does he need any more? He's got high/low voltage/current/temperature disconnect at pack level and at individual cell level.

[peterboat]

19 minutes ago, Dr Bob said:

Yes Pete, I understand that, but what else? What other precautions is he taking?

None because your Tesla just uses the same, my BMW charges up to 100% and then balances except 100% isn't really 100% as it has a buffer and never gets there.

2 minutes ago, TheBiscuits said:

 

Does he need any more? He's got high/low voltage/current/temperature disconnect at pack level and at individual cell level.

I thought he had it covered very well, more than me as I rely on the solar controller doing its stuff. My genny I just watch the voltage and it seems ok for the small usage it gets 

[Dr Bob]

4 minutes ago, TheBiscuits said:

 

Does he need any more? He's got high/low voltage/current/temperature disconnect at pack level and at individual cell level.

 

2 minutes ago, peterboat said:

None because your Tesla just uses the same, my BMW charges up to 100% and then balances except 100% isn't really 100% as it has a buffer and never gets there.

Of course he needs more! If you buy a system from a vendor, the responsibilty for a working system lies with the vendor. If you homebrew, you are responsible.

 

What has this forum decended to? 2 years ago, it gave out generally safe advice.....but this?

I have just spent two days in 2 * 8hr meetings doing a Hazop (a hazard assessment ) on a new piece of kit going into our lab. Basically, identify anything that can go wrong (mainly aimed at safety) and anything with a 'red' outcome - ie one or more dead, you identify sufficient mitigation (even if it is a one in a million chance of the thing happening). An individual homebrewing his own Li's needs to do this himself.

In this case with the alternator directly feeding the battery via BMS, the only protection from overcharging is the BMS. What happens if it fails? What happens if it fails as it reaches its high voltage cutoff (at 14.0V in Mark's case). Simple, the batteries will overcharge if the disconnect fails. What else is he (or anyone else using this simplistic system) doing to mitigate over charging? It is downright dangerous if there is no other mitigation. Buying a full system from one company might be ok (but I still wouldnt be happy) but buying individual components ie a cheap chinese BMS and integrating it onto bare cells is not a clever idea on its own. With no mitigation and publically anouncing there are no problems would be seen as negligent in the event you kill your wife/kids/grandkids. Ignorance would be no defence.

The discussion on here 2 years ago was all about different levels of protection. My system use 6 levels to avoid overcharging (over the top (?) but I consider myself a technical expert on over charging Li's - and need to be whiter than white  -if there was a fire on my boat, I want to avoid prison).

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

Step 2. Have a controllable source of power (ie a B2B or alternator controller) so the power is reduced and cut off before you reach high voltages. Note a recent post by Nick saying his latching relay is his EMERGENCY DISCONNECT, ie you should be reducing power and cutting it off before you activate an emergency disconnect. I use a B2B which monitors its own voltage and backs off power at or before 13.8V. A piece of wire may stop damage to the alternator (I do that as well) but it does not stop overcharging.

Step 3. An audible alarm on my BMV 712 which sounds at 13.9V. That has to be cancelled to stop the noise. You then manually disconnect.

Step 4, An auto disconnect switch is triggered by the BMV relay at 13.9V to operarate in emergency only.

Step 5, An cheap board from amazon (£10) which sounds an alarm at 14V.

Step 6 A BMS board monitoring cell volage and activates the auto disconnect switch at a cell voltage of 3.8V

 

Some of the steps are linked, ie the BMV could go wrong so steps 3 and 4 would fail. The auto disconnect switch could go wrong  and steps 4 and 6 would fail. In either case I still have 4 steps of protection. To be honest, I am getting fed up of the B2B so often I skip Step 2 and manually disconnect at 13.8V but I am very consious of this action and ensure it happens. In the 3 1/2 years of operation my auto disconnect has only activated once -other than when it was being tested.

 

It appears a number of you are working on the basis of one step is enough - ie a cheap chinese BMS that will isolate the power. Why do you think Sterling insist on their B2B? Yes it is about voltage etc but it is also about safety. With the B2B you have at least two levels of protection. Newbies need to understand this and not be blindly led into unsafe operating practices.

 

Three years ago Tom used an off the shelf alternator controller, MP homebrewed his own controller. Then Nick homebrewed an all singing all dancing very elegent system with control of power and emergency cutoffs - but he knew what was in the box. Pete, you yourself pushed the point of only going to 80% to keep safe, but at least you had a manufacturers BMS/Battery combined.

 

........and my Tesla. Warnings from Elon everywhere that its not good to go to 100%. It's not just about battery life. It's about safety as well.

 

 

[Martin Nicholas]

Then, to muddy the waters, Tesla go and say:

Quote

If your vehicle is equipped with an LFP Battery, Tesla recommends that you keep your charge limit set to 100%, even for daily use, and that you also fully charge to 100% at least once per week. If Model 3 has been parked for longer than a week, Tesla recommends driving as you normally would and charge to 100% at your earliest convenience.

The Tesla definition of 100% remains moot. One definite take-away from this is that the two types of Li cells should be treated differently according to Tesla. The self-appointed Tesla gurus confidently say that this action drives the batteries into the hip region (the charge curve is a hip-knee shape) recalibrating the range estimation. I an not a Tesla guru; neither do I understand anything about boats apparently.

[Dr Bob]

1 minute ago, Martin Nicholas said:

Then, to muddy the waters, Tesla go and say:

The Tesla definition of 100% remains moot. One definite take-away from this is that the two types of Li cells should be treated differently according to Tesla. The self-appointed Tesla gurus confidently say that this action drives the batteries into the hip region (the charge curve is a hip-knee shape) recalibrating the range estimation. I an not a Tesla guru; neither do I understand anything about boats apparently.

Tesla are responsible for their system and I just drive it. If anything goes wrong with the batteries, Tesla will be held responsible (I hope). I trust them to keep me safe.

If I was homebrewing, I would take reasonable precautions to ensure I was doing things properly, safely and was not negligent. For insurance purposes as well as liability, it is important.

[MtB]

56 minutes ago, Dr Bob said:

Of course he needs more! If you buy a system from a vendor, the responsibilty for a working system lies with the vendor. If you homebrew, you are responsible.

 

What has this forum decended to? 2 years ago, it gave out generally safe advice.....but this?

 

 

I think the problem lies with the plethora of 'drop in' LA equivalents and the 'tear down' videos on youtube by Will Prowse in particular, where he buys one and dismantles it on camera, and usually finds just a BMS PCB from a manu he recognises and declares the battery product 'great' or 'rubbish' depending on the PCB and the general standard of construction. 

 

The message people get from these tear down videos is all you need are the cells and a BMS PCB to build a battery. Pick your components well and Bob's your uncle, so to say. 

 

Most of these drop in LFP batts come from china etc but now Sterling has launched one, and it too 'only' has a BMS PCB inside. I haven't looked at the installation instructions but the only further safety level Mr Sterling appears (at first sight) to demand is a B2B if you use an alternator. It looks to me as though he either feels his BMS PCB is bomb-proof reliable, or if there is a really big accident, the company will just go under from the compensation claim. Or maybe he has insurance for that. 

 

Have to say, I was surprised to see Sterling offering a drop in LFP. It definitely creates the public impression that with cells+BMS, all bases are covered. I also think a lot of people see "12Vdc" and simply don't grasp the sheer amount of energy stored in these LFP batteries. 

 

Thank you for bringing your safety perspective to this. 

Edited February 19, 2022 by MtB
Missing word

[Martin Nicholas]

18 minutes ago, MtB said:

I also think a lot of people see "12Vdc" and simply don't grasp the sheer amount of energy stored in these LFP batteries. 

or an LA bank come to that.

 

I'd like to know which is safer: your drop-in LFP pack or the LA pack it just replaced.

Edited February 19, 2022 by Martin Nicholas
More

[MtB]

7 minutes ago, Martin Nicholas said:

or an LA bank come to that.

 

I'd like to know which is safer: your drop-in LFP pack or the LA pack it just replaced.

 

Have a guess....

[TheBiscuits]

Just now, MtB said:

 

Have a guess....

 

I'll guess at the bucket of sulphuric acid containing many kilos of a known toxic heavy metal that lets out explosive gases when overcharged.

 

Familiarity breeds contempt, innit.

[Dr Bob]

22 minutes ago, Martin Nicholas said:

or an LA bank come to that.

 

I'd like to know which is safer: your drop-in LFP pack or the LA pack it just replaced.

 

 

7 minutes ago, TheBiscuits said:

 

I'll guess at the bucket of sulphuric acid containing many kilos of a known toxic heavy metal that lets out explosive gases when overcharged.

 

Familiarity breeds contempt, innit.

Spot on.

LA's are also dangerous, just in a different way. Hydrogen Sulphide is a killer.

Not that may peeps put LA's under their beds though.

[mrsmelly]

1 minute ago, Dr Bob said:

 

 

Spot on.

LA's are also dangerous, just in a different way. Hydrogen Sulphide is a killer.

Not that may peeps put LA's under their beds though.

Yaaaaaaaaaaaaaaaaaaaaay..............young Andys back 

[Dr Bob]

4 minutes ago, mrsmelly said:

Yaaaaaaaaaaaaaaaaaaaaay..............young Andys back 

Young?

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

 

[TheBiscuits]

3 minutes ago, Dr Bob said:

Young.......................? I hit the big two score and ten in April!

 

April which year?

 

[Dr Bob]

2 hours ago, peterboat said:

 

I thought he had it covered very well, more than me as I rely on the solar controller doing its stuff.

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.

Just now, TheBiscuits said:

 

April which year?

 

At least I'm getting there after Mrs Bob

[TheBiscuits]

29 minutes 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.

 

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.

 

 

Edited February 19, 2022 by TheBiscuits
spellink. twice!

[TheBiscuits]

17 minutes ago, Dr Bob said:

At least I'm getting there after Mrs Bob

 

It was the two score and ten I was querying.  You must have had a very tough paper round! 

 

[Dr Bob]

3 minutes ago, TheBiscuits said:

 

It was the two score and ten I was querying.  You must have had a very tough paper round! 

 

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

[TheBiscuits]

2 minutes ago, Dr Bob said:

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

 

It's a terrible thing when the memory starts to go ...

[Dr Bob]

9 minutes ago, TheBiscuits said:

 

The other thing is, you are using cheap (and also expensive) Chinese circuits to keeps 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?

Your are right, they are a mixture of cheap and expensive Chinese circuits which is exactly why I have multiple layers of redundancy.

The beauty of my set up is that I can just isolate the Li's and return the boat to LA only when the sprogs take over on board.

1 minute ago, TheBiscuits said:

 

It's a terrible thing when the memory starts to go ...

It's not starting.

 

Its already gone!