Monitoring lithium batteries

[WotEver]

The answers to your questions are...

 

Probably not in the short term but it will likely shorten its life. 

 

Yes, pretty much, especially when they are young. Temperature monitoring though should be part of the BMS function. 

 

Yes, talk to Peter

 

9 hours ago, Dr Bob said:

The issues that still bug me are

- will it overload my  90A alternator although likely it will only run for an hour or hour and a half to replace my 100Ahr overnight usage

- are LiFePO4 really that stable to thermal runaway....I'm not totally convinced?

- Can I get some cheap 2nd hand Lithiums?

 

[WotEver]

11 hours ago, peterboat said:

You are right but because in our boat systems we dont draw big current the batteries dont go out of balance, in cars huge current is drawn and a BMS is essential to balance both the batteries and cells that make up the pack. My drive batteries will hardly be working in my system because my plan is to move when the sun is shining and solar is producing a lot of amps, my batteries are for emergencies not day to day travel

Because you don’t draw huge currents your cells won’t go out of balance quickly. But they will still go out of balance eventually. Hopefully, with a well-selected set of cells, this will take a year or more. 

 

But it might happen sooner

 

[Robbo]

10 hours ago, Dr Bob said:

- will it overload my  90A alternator although likely it will only run for an hour or hour and a half to replace my 100Ahr overnight usage

- are LiFePO4 really that stable to thermal runaway....I'm not totally convinced?

- Can I get some cheap 2nd hand Lithiums?

- If you have leisure batteries they will put a lot of load on your batteries when charging as well for long periods,  this really is how big your bank is and how much they can take.  So if you have a 400ah leisure bank it will be able to take 90amp easy if it was 50% at DoD.

 

- Yes, chemically LiFePO₄ are one of the most stable batteries you can get.   You're not convinced because of the word Lithium and phones exploding, however that is other Lithium batteries (mainly Cobalt) where they are not stable and can easily thermally runaway.   A VRLA battery is more likely to themally runaway than a LiFePO₄

 

- Let me know if you find some

Edited August 30, 2018 by Robbo

[Dr Bob]

1 minute ago, Robbo said:

- If you have leisure batteries they will put a lot of load on your batteries when charging as well for long periods,  this really is how big your bank is and how much they can take.  So if you have a 400ah leisure bank it will be able to take 90amp easy if it was 50% at DoD.

 

- Yes, chemically LiFePO₄ are one of the most stable batteries you can get.   You're not convinced because of the word Lithium and phones exploding, however that is other Lithium (mainly Cobalt) where they are not stable and can easily thermally runaway.   A VRLA battery is more likely to themally runaway than a LiFePO₄

 

- Let me know if you find some

On charging, typically we are having to put 100 Ahrs back in when we start off in the morning (660Ahr bank). Alternator starts at circa 70A dropping to 60A in 5 mins then down to 40A after an hour. Steady reduction after that. Alternator temp doesn't go over 70 deg. 

With Lithiums, I guess it may stay at 60-70A but only need an hour (if there is some sun for solar later). Possibly I would be tempted not to run the engine everyday when not moving, so then 2 hrs at 70A. That sounds like it is at the limit of the alternator.

[peterboat]

16 minutes ago, WotEver said:

Because you don’t draw huge currents your cells won’t go out of balance quickly. But they will still go out of balance eventually. Hopefully, with a well-selected set of cells, this will take a year or more. 

 

But it might happen sooner

 

You are wrong as you will see when we film the batteries this morning, and from James experience of over a year on these batteries.

I have just boiled a kettle and that was taking over 40 amps per battery, the imbalance was up to 20 mv per cell as it drew this current but mostly in single figure, as soon as the kettle was boiled the imbalance was down to 2-4mv per cell this is without active balancing, the battery at the moment is at 75.99% SOC and very happy

[WotEver]

2 minutes ago, peterboat said:

You are wrong as you will see when we film the batteries this morning, and from James experience of over a year on these batteries.

I have just boiled a kettle and that was taking over 40 amps per battery, the imbalance was up to 20 mv per cell as it drew this current but mostly in single figure, as soon as the kettle was boiled the imbalance was down to 2-4mv per cell this is without active balancing, the battery at the moment is at 75.99% SOC and very happy

I’m not wrong. The cells are not perfect and they WILL go out of balance eventually. Even Jono’s  As I said, this will take some time, possibly years with a well matched set. They’re not magic, just chemistry. 

[Robbo]

2 minutes ago, Dr Bob said:

On charging, typically we are having to put 100 Ahrs back in when we start off in the morning (660Ahr bank). Alternator starts at circa 70A dropping to 60A in 5 mins then down to 40A after an hour. Steady reduction after that. Alternator temp doesn't go over 70 deg. 

With Lithiums, I guess it may stay at 60-70A but only need an hour (if there is some sun for solar later). Possibly I would be tempted not to run the engine everyday when not moving, so then 2 hrs at 70A. That sounds like it is at the limit of the alternator.

The alternator may be reducing power as it's getting hot and not because your batteries are demanding less.   You could test this by turning something high powered on and using a clamp meter to see.  (A shunt on the battery won't show the amps, as the extra load is not going via the battery.).   If it is because the alternator is getting hot, then additional cooling won't make anything worse.

[MtB]

5 minutes ago, WotEver said:

I’m not wrong. The cells are not perfect and they WILL go out of balance eventually. Even Jono’s  As I said, this will take some time, possibly years with a well matched set. They’re not magic, just chemistry. 

 

This process seems to be very slow however, given the empirical evidence of users. Even that American bod with the irritating writing style comments that cells stay in balance for years on end in regular use on his sea boats. 

[WotEver]

7 minutes ago, Mike the Boilerman said:

 

This process seems to be very slow however, given the empirical evidence of users. Even that American bod with the irritating writing style comments that cells stay in balance for years on end in regular use on his sea boats. 

Yes indeed. With well matched cells it could take many years. But it WILL happen. 

[MtB]

5 minutes ago, WotEver said:

Yes indeed. With well matched cells it could take many years. But it WILL happen. 

 

For an experimental installation such as mine however, this means cell balancing as a function of any automated battery management is something I can dispense with. I just need a cheapo DVM on the bulkhead for each cell (or cell bank if I use those tiny cells like in the RELiON batts), then I can see in passing if any cell is getting out of step and manually balance at my convenience.

 

 

 

 

Edited August 30, 2018 by Mike the Boilerman
Stray capitalisation

[WotEver]

9 minutes ago, Mike the Boilerman said:

 

For an experimental installation such as mine however, this means cell balancing as a function of any automated battery management is something I can dispense with. I just need a cheapo DVM on the bulkhead for each cell (or cell bank if I use those tiny cells like in the RELiON batts), then I can see in passing if any cell is getting out of step and manually balance at my convenience.

Let us know how that works out for you

[Dr Bob]

25 minutes ago, Robbo said:

The alternator may be reducing power as it's getting hot and not because your batteries are demanding less.   You could test this by turning something high powered on and using a clamp meter to see.  (A shunt on the battery won't show the amps, as the extra load is not going via the battery.).   If it is because the alternator is getting hot, then additional cooling won't make anything worse.

The reduction is not because its getting hot. If that was the case, if I turned on something high powered, the charging amps on the meter would drop to power that draw (ie the alternator cant produce any more). This doesnt happen.

No, the drop in charging current is just typical of a battery restricting how much current it can take as it drops down to the tail current when nearing fully charged.

[MtB]

Just now, WotEver said:

Let us know how that works out for you

 

I will no doubt write about it endlessly on here....

 

[MtB]

Next thing to consider is temperature monitoring. I really REALLY don't want a cell to overheat and melt through the baseplate of the boat so this needs to be automatic. A thermocouple attached to each of the four cells can monitor the temp. Next I need an electronic device to read the thermocouple and open a switch at say 50C, which will de-energise a relay and disconnect the battery bank. 

 

Any suggestions anyone? Something simple rather than something Victron!

 

Or maybe a bi-metal strip and a microswitch....

[peterboat]

40 minutes ago, WotEver said:

I’m not wrong. The cells are not perfect and they WILL go out of balance eventually. Even Jono’s  As I said, this will take some time, possibly years with a well matched set. They’re not magic, just chemistry. 

So why havent James cells gone out of balance?

20 minutes ago, Mike the Boilerman said:

 

For an experimental installation such as mine however, this means cell balancing as a function of any automated battery management is something I can dispense with. I just need a cheapo DVM on the bulkhead for each cell (or cell bank if I use those tiny cells like in the RELiON batts), then I can see in passing if any cell is getting out of step and manually balance at my convenience.

 

 

 

 

Mike buy two valence batteries, its less painful than all this playing restrict charging to 13.8 volts [you can do this with the whispergen] and like me just check the batteries once a month to find all cells balanced. I at the beginning did top balancing with the computer and since then all has remained the same

Edited August 30, 2018 by peterboat

[MtB]

15 minutes ago, peterboat said:

So why havent James cells gone out of balance?

Mike buy two valence batteries, its less painful than all this playing restrict charging to 13.8 volts [you can do this with the whispergen] and like me just check the batteries once a month to find all cells balanced. I at the beginning did top balancing with the computer and since then all has remained the same

 

But they cost £1300 each! 

 

Or do you still know of a source for s/h?

[WotEver]

18 minutes ago, Mike the Boilerman said:

open a switch at say 50C

40C

17 minutes ago, peterboat said:

So why havent James cells gone out of balance?

Because it’s too soon as I’ve already stated twice. 

20 minutes ago, Mike the Boilerman said:

de-energise a relay and disconnect the battery bank. 

De-energising suggests that it’s otherwise permanently energised. That’s a waste of power. Consider a bistable contactor instead. 

[peterboat]

Sorry to say take one failed it was a bit fuzzy and paul was moving the camera!! he has gone to charge up his real camera and get the tripod out as well take two will be this afternoon!

26 minutes ago, Mike the Boilerman said:

 

But they cost £1300 each! 

 

Or do you still know of a source for s/h?

I might do Mike he is away until end of this month so when he gets back I will ask for you ok?

[peterboat]

26 minutes ago, WotEver said:

40C

Because it’s too soon as I’ve already stated twice. 

De-energising suggests that it’s otherwise permanently energised. That’s a waste of power. Consider a bistable contactor instead. 

Tony the batteries are in use every day some were made in 2006 one chap has these at his house and he is off grid and they arnt going out of balance. Remember they were made for mini subs where reliability was essential which is why they were 2.5k new

[MtB]

3 minutes ago, peterboat said:

 

I might do Mike he is away until end of this month so when he gets back I will ask for you ok?

 

 

Ok thanks! 

 

No hurry, this project is just idle speculation at the moment. Not even sure which boat to install it in but probably the one with the 24v Whipspergen. 

 

Although I have another candidate boat with an utterly goosed 12v set of FLA domestics.

[Robbo]

1 hour ago, Dr Bob said:

The reduction is not because its getting hot. If that was the case, if I turned on something high powered, the charging amps on the meter would drop to power that draw (ie the alternator cant produce any more). This doesnt happen.

No, the drop in charging current is just typical of a battery restricting how much current it can take as it drops down to the tail current when nearing fully charged.

You could test how hot your alternator gets when pushing the amps for a few hours too see how it performs.

[peterboat]

Here is the video ta da  if it hasnt worked here is the you tube link https://youtu.be/aDI-Ql3nqxA

 

[WotEver]

7 minutes ago, peterboat said:

Here is the video ta da  if it hasnt worked here is the you tube link https://youtu.be/aDI-Ql3nqxA

Which shows that the internal BMS is continually balancing the cells in the same way that Mastervolt implements. If they’re continually balancing themselves then no wonder they stay in balance!

[nicknorman]

12 minutes ago, peterboat said:

Here is the video ta da  if it hasnt worked here is the you tube link https://youtu.be/aDI-Ql3nqxA

 

Had a quick look (I’m at the airport awaiting a flight). Very interesting. So how exactly do you connect between your PC and the battery? Some proprietary interface, or some standard cable?

Edited August 30, 2018 by nicknorman

[peterboat]

1 minute ago, WotEver said:

Which shows that the internal BMS is continually balancing the cells in the same way that Mastervolt implements. If they’re continually balancing themselves then no wonder they stay in balance!

Balance is inactive because its in green and it says its inactive when it goes to yellow at the beginning of the video its because I have connected the puter to it and activated the BMS. Under normal circumstances I dont connect the puter to it for months so the battery must be balancing by design

1 minute ago, nicknorman said:

Had a quick look (I’m at the airport awaiting a flight). Very interesting. So how exactly do you connect between your PC and the battery? Some proprietary interface, or some standard cable?

A 19 quid cable off Amazon and software that James had I have 60 amps going into the bank at the moment washer on and all is wellmI will look at the other two batteries tonight to see how they are doing