Issues with lithiums in very cold weather?

[Tony1]

 

The background to this query is that I've decided to move my lithium batteries from a warm bedroom cupboard out into the engine bay.

If I remember it, there were about 15 nights last winter when the temp went below zero (I was on the Llangollen)- and sometimes well below zero. On a few nights it went down to -9 on the cut, and even by midday it was still barely above zero.  

 

I understand that its is ok to draw current from lithiums down to -5 or lower, which is very handy as I do like to use the electric kettle for a coffee on a freezing winter morning. 

 

But I am aware that charging lithiums below zero degrees can damage them, and I was curious about how lithium users deal with this issue on the very cold mornings that we occasionally get. I was talking to a boater not long ago about the positive attributes of lithiums, and he mentioned that on one of those very cold winter mornings he spoke to a few boaters who'd had problems with their lithiums.

 

I didnt pick up on the detail of the issue, but I would guess the BMS in the lithiums disconnected the batteries when it sensed the very low temperatures, and I think this meant the loads were disconnected as well as the charging, so I presume the boats had no power.  

 

There are ways around this, such as heating pads, and I'm curious how much power these things use on the very cold nights, and whether they are considered worthwhile? 

Other folks have pointed out that if the batteries are placed directly onto the steel of the swim(?) plate (which seems to be the most common location), they will kept around zero at worst, because the water under the surface doesn't go below freezing (unless its apocalyptic freezing).

So maybe insulation pads are counter productive?

Do some people deal with the cold issue by simply running the engine for say 20 mins before they do any charging? 

 

So I've heard some people say its almost a non-issue, and I've heard a couple say they have had complications with lithiums on the very coldest days. 

With all that said, I'd love to hear the experiences of anyone who's cruised with lithiums in freezing weather. 

 

Edited July 23, 2023 by Tony1

[Alan de Enfield]

1 minute ago, Tony1 said:

There are ways around this, such as heating pads

 

If your batteries have disconnected themselves, where will you get the power to run heat-pads ?

[rusty69]

6 minutes ago, Alan de Enfield said:

 

If your batteries have disconnected themselves, where will you get the power to run heat-pads ?

I suspect the heater comes on before the BMS disconnect. 

[magnetman]

5 minutes ago, Alan de Enfield said:

 

If your batteries have disconnected themselves, where will you get the power to run heat-pads ?

Presumably the heating system would turn on before the batteries disconnected .

 

My lithium batteries are LTO which can deal with sub zero temperatures but the LFP are advertised as potentially having some problems. 

 

I'd just ignore the insurance clause and carry on with them in the cabin. 

 

 

 

 

[Tony1]

13 minutes ago, Alan de Enfield said:

 

If your batteries have disconnected themselves, where will you get the power to run heat-pads ?

 

On the more fully featured BMSs that come with many new batteries, the heating will be activated at a set temp.

E.g. on the Fogstar batteries, the temp sensor will activate the battery's built-in heating pad before it gets to zero. So you are using the battery's own energy to keep it warm. 

On external heating pads, a similar thing will happen. So that stops the batteries disconnecting. 

I dont have any of that on mine, but I can set something up to disconnect the chargers if the battery goes below zero. The loads that would power the heating pad, on my DIY system, will never be disconnected due to a temp sensor. 

 

 

7 minutes ago, magnetman said:

Presumably the heating system would turn on before the batteries disconnected .

 

My lithium batteries are LTO which can deal with sub zero temperatures but the LFP are advertised as potentially having some problems. 

 

I'd just ignore the insurance clause and carry on with them in the cabin. 

 

 

The problem is that it does look as if some sort of fire protection is going to be a requirement for indoor batteries (and I've heard that coming from several directions now), so I figure I might as well bite the bullet and get them relocated. 

My thinking is that it will avoid any arguments with an over zealous BSS inspector who might try to fail the boat because my batteries are exposed to the interior (and there isnt enough space for a fireproof/steel box to be fitted about them).

It would be a pain to fail, and then have to scramble to get the work done in the two weeks or whatever it is that you get to put things right before they recheck. 

 

And to be fair, people are not reporting problems with them in winter, so maybe its all fine...

 

Edited July 23, 2023 by Tony1

[magnetman]

Indeed. Your boat is probably rather more 'residential' than either of my boats. I like living in a shed with minimal installations so when the BS inspector comes I usually find there and no batteries other than the engine starter. 

 

Fork 'andles !

I suppose having 7KwH of illicit lithium batteries might be found out if there were to be a cataclysmic event but I don't go there. I stay here. 

 

Edited July 23, 2023 by magnetman
grammar

[rusty69]

1 minute ago, magnetman said:

I like living in a shed with minimal installations so when the BS inspector comes I usually find there and no batteries other than the engine starter

That will be my strategy too. 

[magnetman]

The global warm bin situation might mean less cold winters anyway. 

 

 

[rusty69]

The obvious solution is to move the batteries south for winter. 

[magnetman]

I think putting them lower down in the boat will reduce the issues due to the water temperature. 

 

 

Air is the basic issue in the world. If the whole world consisted of only water there would be considerably fewer problems..

[Naughty Cal]

Our LFP battery once got below zero degrees last year. The van sits unheated on the drive and it was only after a prolonged cold spell that the battery got cold enough for the BMS to stop it accepting charge.

 

It wasn't really a problem. We could still discharge the battery and after a few hours with the heating on the battery was warm enough to accept charge again. Although it didn't help that the solar panels were covered in ice so realistically the battery saw no charge that weekend until we drove home.

 

No harm done. 

[magnetman]

Given that some of the biggest swinging dicks in the world are microchip manufacturing companies one does have to wonder whether all of these electronics are actually needed or perhaps just pushed by vested interests. 

 

Think Tesla is big? 

 

What about Nvidia ? 

 

 

 

 

[Tony1]

2 minutes ago, rusty69 said:

The obvious solution is to move the batteries south for winter. 

 

The batteries would obviously love to disappear off to a warmer place, and I would love to oblige them, but alas there are complications.

 

I did briefly consider removing the lithiums into a storage box on the towpath, and installing two crappy lead acid batteries to pretend I've never had lithiums aboard.  

But then they would want to know why I had three B2B chargers in the boat. So I'd have to rip those out, plus all the wiring...

Then they'd want to know why I needed all those BMV712s, the BEP switch, the battery protect disconnect, etc etc.

 

Maybe the approach I should take is to attempt the BSS with the lithiums and if the guy fails it, then I can rip out all of the current wiring (bar the MPPTs), then spend £200 on some cheap lead acids and set up a basic lead acid system to pass the inspection.

 

Only a complete scoundrel would then put all of the lithium gear back in place a few days later, so I definitely wouldn't do that.  

 

[nicknorman]

21 minutes ago, Tony1 said:

 

The background to this query is that I've decided to move my lithium batteries from a warm bedroom cupboard out into the engine bay.

If I remember it, there were about 15 nights last winter when the temp went below zero (I was on the Llangollen)- and sometimes well below zero. On a few nights it went down to -9 on the cut, and even by midday it was still barely above zero.  

 

I understand that its is ok to draw current from lithiums down to -5 or lower, which is very handy as I do like to use the electric kettle for a coffee on a freezing winter morning. 

 

But I am aware that charging lithiums below zero degrees can damage them, and I was curious about how lithium users deal with this issue on the very cold mornings that we occasionally get. I was talking to a boater not long ago about the positive attributes of lithiums, and he mentioned that on one of those very cold winter mornings he spoke to a few boaters who'd had problems with their lithiums.

 

I didnt pick up on the detail of the issue, but I would guess the BMS in the lithiums disconnected the batteries when it sensed the very low temperatures, and I think this meant the loads were disconnected as well as the charging, so I presume the boats had no power.  

 

There are ways around this, such as heating pads, and I'm curious how much power these things use on the very cold nights, and whether they are considered worthwhile? 

Other folks have pointed out that if the batteries are placed directly onto the steel of the swim(?) plate (which seems to be the most common location), they will kept around zero at worst, because the water under the surface doesn't go below freezing (unless its apocalyptic freezing).

So maybe insulation pads are counter productive?

Do some people deal with the cold issue by simply running the engine for say 20 mins before they do any charging? 

 

So I've heard some people say its almost a non-issue, and I've heard a couple say they have had complications with lithiums on the very coldest days. 

With all that said, I'd love to hear the experiences of anyone who's cruised with lithiums in freezing weather. 

 

I think the temperature thing is a bit over-hyped. There is a big difference between minimum discharge temperature and minimum charge temperature, and neither is a solid cutoff.
 

Take charging: bear in mind the cells allow charging at 1C (eg 200A for a 200Ah battery) down to about 0c. Below that you can still charge safely but at a lower charge rate, ie 0.1C by the time you get to -10c. Most boat installations don’t charge anywhere near 1C so you should be ok charging down to a few degrees below zero (depends on charge rate vs capacity). As you say, with batteries near the bottom of the boat it’s unlikely to get below a couple of degrees below zero.

 

For discharging there is less of an issue, discharging down to about -20c is ok, it’s just that capacity is reduced.

 

Our batteries are in trad stern modern engine area and I did put a heating pad underneath that I can switch on manually. It takes about 60w (4.5A). I have used it on occasion “just because I can” but it hasn’t been necessary. We don’t live aboard but we were out in January with the canal iced over. I didn’t see less than 5c on the battery temperature even when we arrived to an unheated boat.

 

So I  wouldn’t fret about it and certainly there is no need to heat the batteries for discharge. You could add a manually controlled heating pad for charging - and discharging the batteries into that isn’t an issue unless the batteries get below -20! - just switch it on a while before you want to charge the batteries if they are zero or below (I doubt they ever will be).

[n-baj]

The instructions with my battery states they can be discharged in temperatures down to -20 deg c. The battery will direct all incoming power to the heating pad until it gets to a temperature where it can be charged. 
 

I was more worried about the batteries getting too hot putting them in the engine bay but after a few hours river cruising it didn’t go above 30 deg c. 😃

[magnetman]

Or source a BS scheme inspector who will issue a pass. 

[rusty69]

1 minute ago, Tony1 said:

 

The batteries would obviously love to disappear off to a warmer place, and I would love to oblige them, but alas there are complications.

 

I did briefly consider removing the lithiums into a storage box on the towpath, and installing two crappy lead acid batteries to pretend I've never had lithiums aboard.  

But then they would want to know why I had three B2B chargers in the boat. So I'd have to rip those out, plus all the wiring...

Then they'd want to know why I needed all those BMV712s, the BEP switch, the battery protect disconnect, etc etc.

 

Maybe the approach I should take is to attempt the BSS with the lithiums and if the guy fails it, then I can rip out all of the current wiring (bar the MPPTs), then spend £200 on some cheap lead acids and set up a basic lead acid system to pass the inspection.

 

Only a complete scoundrel would then put all of the lithium gear back in place a few days later, so I definitely wouldn't do that.  

 

Mine passed the BSS this time round (last year). I doubt they will be safe next time though. 

[Tony1]

1 minute ago, magnetman said:

Or source a BS scheme inspector who will issue a pass. 

 

If you have a reliable method for obtaining the services of such a creature, do please PM me with the relevant details.

As far as I know, many of them have their own little hobby horses that they like to focus on, and if I get the bloke who treats lithiums the way a 16th century peasant treats a suspected witch, I've had it. 

5 minutes ago, nicknorman said:

I think the temperature thing is a bit over-hyped. There is a big difference between minimum discharge temperature and minimum charge temperature, and neither is a solid cutoff.
 

Take charging: bear in mind the cells allow charging at 1C (eg 200A for a 200Ah battery) down to about 0c. Below that you can still charge safely but at a lower charge rate, ie 0.1C by the time you get to -10c. Most boat installations don’t charge anywhere near 1C so you should be ok charging down to a few degrees below zero (depends on charge rate vs capacity). As you say, with batteries near the bottom of the boat it’s unlikely to get below a couple of degrees below zero.

 

For discharging there is less of an issue, discharging down to about -20c is ok, it’s just that capacity is reduced.

 

Our batteries are in trad stern modern engine area and I did put a heating pad underneath that I can switch on manually. It takes about 60w (4.5A). I have used it on occasion “just because I can” but it hasn’t been necessary. We don’t live aboard but we were out in January with the canal iced over. I didn’t see less than 5c on the battery temperature even when we arrived to an unheated boat.

 

So I  wouldn’t fret about it and certainly there is no need to heat the batteries for discharge. You could add a manually controlled heating pad for charging - and discharging the batteries into that isn’t an issue unless the batteries get below -20! - just switch it on a while before you want to charge the batteries if they are zero or below (I doubt they ever will be).

 

Cheer Nick, I was beginning to suspect the cold thing was being overplayed a bit, but my concerns arose again after talking to that boater (and I do trust the guy, he seemed a very solid character and not prone to exaggeration)- and he was very clear that there were at least three boaters (in his vicinity) who hit temporary snags when it went below minus 9 last December. 

 

I guess what I'm pondering now is whether its worth installing insulating mats, or heated pads, or just on the bare steel. 

 

[ditchcrawler]

5 minutes ago, Tony1 said:

 

If you have a reliable method for obtaining the services of such a creature, do please PM me with the relevant details.

As far as I know, many of them have their own little hobby horses that they like to focus on, and if I get the bloke who treats lithiums the way a 16th century peasant treats a suspected witch, I've had it. 

I think he meant find one who will visit the boat, drink tea and eat biscuits, take your money and write the ticket out, not one who likes or dislikes anything

[Tony1]

Just now, ditchcrawler said:

I think he meant find one who will visit the boat, drink tea and eat biscuits, take your money and write the ticket out, not one who likes or dislikes anything

 

Thanks Brian. I dont suppose you know of such a gentlemen anywhere in the midlands or northwest? If you do, PM me (I wouldnt want anyone's reputation being discussed publicly).

 

25 minutes ago, n-baj said:

The instructions with my battery states they can be discharged in temperatures down to -20 deg c. The battery will direct all incoming power to the heating pad until it gets to a temperature where it can be charged. 
 

I was more worried about the batteries getting too hot putting them in the engine bay but after a few hours river cruising it didn’t go above 30 deg c. 😃

 

I hope you'll keep us posted on how the Fogstars perform in colder weather. I'm particularly curious about how much energy they are going to use in keeping themselves above zero on those very cold nights. If you can fill in a chart of temp vs SoC every 30 minutes throughout the night that would be very helpful.

 

[n-baj]

22 minutes ago, Tony1 said:

 

 

 

I hope you'll keep us posted on how the Fogstars perform in colder weather. I'm particularly curious about how much energy they are going to use in keeping themselves above zero on those very cold nights. If you can fill in a chart of temp vs SoC every 30 minutes throughout the night that would be very helpful.

 

Will do but the heater won’t be activated on discharge only so they won’t be keeping themself above zero overnight, unless I start to run the generator overnight, which will undoubtedly make me incredibly popular amongst the locals and nearby boaters 😃

 

There’s a chance I’ll be on hook up over this winter anyway, which will be shame as I was looking forward to seeing how the battery performs over the winter.

[nicknorman]

1 hour ago, Tony1 said:

 

Cheer Nick, I was beginning to suspect the cold thing was being overplayed a bit, but my concerns arose again after talking to that boater (and I do trust the guy, he seemed a very solid character and not prone to exaggeration)- and he was very clear that there were at least three boaters (in his vicinity) who hit temporary snags when it went below minus 9 last December. 

 

I guess what I'm pondering now is whether its worth installing insulating mats, or heated pads, or just on the bare steel. 

 

If you are going to put Li in the engine bay there are two thermal enemies - too hot and too cold. Too hot when the engine is running for a long cruise in summer, too cold when the engine is not running in winter.

 

So IMO one desirable thing is some insulation to protect against rapid temperature change (hot engine). Our boat already had a wooden battery box (made from thick ply, 15mm or so) so I just added some thin foam sheets around the batteries to limit the thermal conductivity to the batteries. Also for some vibration isolation. Then I added some heating stuff between insulation and batteries. I think it’s an important point that there is no point in putting a heating pad between batteries and bare steel - all the heat will go into the cut!

 

Since the battery box only comes about 3/4 way up the batteries, I also built a lid made from foam/grp sandwich and, since we tend to have long cruising days, I added a small fan and ducting to blow cabin air into the battery chamber to keep it cool. Comes on with engine ignition.
But in your case, perhaps an enclosed and insulated battery box with ducted air from cabin might be a good idea. You already have warm air in the cabin from the stove etc, might as well use it and a small amount of current for a fan to maintain an even temperature in for your batteries.

Edited July 23, 2023 by nicknorman

[booke23]

I have a Victron Lithium Iron Phosphate battery in my engine bay, and the BMS won't allow charging below 5c. You can change this setting in the app but it warns of permanent damage and void warranties if you do this. 

 

Some winters it can be a pain...but I'm a leisure boater. Sometimes I'm only at the boat once every fortnight. On one cold snap last winter the BMS wouldn't allow solar charging for at least 10 days as the battery never got above 5c. However starting the engine does bring the temp up in the engine bay after about an hour of running.

 

Obviously if you were living on the boat I imagine it wouldn't get so cold soaked. 

[Tony1]

7 minutes ago, nicknorman said:

If you are going to put Li in the engine bay there are two thermal enemies - too hot and too cold. Too hot when the engine is running for a long cruise in summer, too cold when the engine is not running in winter.

 

So IMO one desirable thing is some insulation to protect against rapid temperature change (hot engine). Our boat already had a wooden battery box (made from thick ply, 15mm or so) so I just added some thin foam sheets around the batteries to limit the thermal conductivity to the batteries. Also for some vibration isolation. Then I added some heating stuff between insulation and batteries. I think it’s an important point that there is no point in putting a heating pad between batteries and bare steel - all the heat will go into the cut!

 

Since the battery box only comes about 3/4 way up the batteries, I also built a lid made from foam/grp sandwich and, since we tend to have long cruising days, I added a small fan and ducting to blow cabin air into the battery chamber to keep it cool. Comes on with engine ignition.
But in your case, perhaps an enclosed and insulated battery box with ducted air from cabin might be a good idea. You already have warm air in the cabin from the stove etc, might as well use it and a small amount of current for a fan to maintain an even temperature in for your batteries.

 

Thanks a lot Nick, I have to say pushing air from the bedroom into the battery box sounds like a cracking idea. 

Why waste electrical energy which costs a lot (in diesel) to replace, when there is an abundance of very warm air in the bedroom from the stove? 

A small tube/pipe using a low power computer fan would probably push enough air to keep the batteries well above zero. 

I think you've hit on a great idea there. 

 

 

 

 

 

[nicknorman]

3 minutes ago, booke23 said:

I have a Victron Lithium Iron Phosphate battery in my engine bay, and the BMS won't allow charging below 5c. You can change this setting in the app but it warns of permanent damage and void warranties if you do this. 

 

Some winters it can be a pain...but I'm a leisure boater. Sometimes I'm only at the boat once every fortnight. On one cold snap last winter the BMS wouldn't allow solar charging for at least 10 days as the battery never got above 5c. However starting the engine does bring the temp up in the engine bay after about an hour of running.

 

Obviously if you were living on the boat I imagine it wouldn't get so cold soaked. 

As I mentioned, 5c or zero c (depending on which manufacturer) is not a binary limit. Below this temperature, charging is OK provided current is well below 1C. Depending on you solar output Vs battery capacity, it might be sensible to change the BMS cutoff to allow relatively low current charging at lower temperature. Unfortunately a BMS is either on or off, it can’t be on below a certain current and then off for higher current. It would be up to you to ensure that max charging current was less than say 1/10th capacity.