question

valden avatar image
valden asked

Lithium battery charging in Arctic expedition conditions

@Ur12VMan , @Daniël Boekel (Victron Energy Staff)

Hi 12VMan (and Victron staff please). I found your thread on Lithium battery protect settings while searching, but decided my comment should be a new question.

Thanks for your answer in that thread, mentioning that Victron lithium batteries issue a temperature alert at 5C. This gets my attention. My research to date was indicating that lithium batteries are OK for charging down to around 1C (and for discharging well below 0C, as an aside). I need to pursue this, as I'm planning to use Victron LiFePO4 batteries in Arctic conditions, in an expedition yacht that will be static for days to a week or two. Water temps will be down to around 2-3C, sometimes lower depending on icing. I'm looking into the need for heating for the battery box, which will be under the insulated floorboards and so outside of the primary heated spaces. If 5C is the real deal, I need to get serious with calculations on battery energy that might be consumed in making the batteries warm enough to be chargeable. Or other heating.

So, where is this 5C figure coming from? OK, I see +5C mentioned in the 12.8V LiFePO4 battery data sheet.

This prompts a few specific and important questions, about the Victron 12.8V 300Ah variants:

1. What is the lower internal battery temperature at which the battery signals to a connected BMS that charging is not permitted?

2. If the answer to Q1 is different than +5C, what is the consequence in terms of battery health (and charging efficiency?) of charging occurring between the two temperatures?

3. Does the answer to Q2 depend on the rate of charging?

4. If the internal battery temperature is just high enough for the battery to allow itself to be charged, and in this case at a low rate of 20A per battery (80A from a normal alternator, shared between 4 batteries), will this charging slowly warm the batteries up such that a higher rate of charging can be initiated in due course?

5. At what battery temperature (measured by a sensor on the positive terminal, or is there a way to get the internal temperature?) can high rate charging at ~150A per battery be initiated, such that no appreciable damage to battery health occurs? Would it be prudent to step the charging rate up slowly as the batteries warm up?

Clearly, it will be helpful if I rig a temperature sensor for the battery box, to guide appropriate action before each charging session.

The boat will use an Integrel On-Engine Charger (basically a big and very efficient second alternator) which can charge at up to a very high rate. Or it can be turned off so that charging is via the engine's standard alternator only. I might need to raise the battery box temperature before starting to charge each week or so. Heat from the main engine during these charging events will then help.

Thank you for your help with these questions. :-)

Lithium BatteryBMSTemperature Sensortemperature
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9 Answers
ur12vman avatar image
ur12vman answered ·

Hi Valden,

The BMS will not allow charging, at any rate, below an internal temp of 5C. This can be changed in the settings, but will void the battery warranty. I have heard that other manufacturers batteries with the same chemistry will allow charging at a lower temp, but I have no experience with that. The batteries have internal temp sensors and you can read that temp via the bluetooth app Victron Connect. The same sensors alert the BMS of the internal temp and will either allow charging or not.

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valden avatar image valden commented ·

Thanks for this information. Very helpful.

Can you recall what the internal temperature setting for charging can be dialled down to? Warranty will not be the issue in a survival situation, but being able to gently charge and warm the battery up could be. Of course, if 'breaking the glass' can be avoided, it will be.

I'm guessing the change to the minimum charging temperature is made in the settings of the battery, not the BMS.

Thanks. :-)

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valden avatar image
valden answered ·

In a reply to @Ur12VMan yesterday I asked what internal temperature setting a Victron 12.8V 300Ah Smart LiFePO4 battery could be dialed down to, to allow charging at that minimum temperature.

I downloaded the VictronConnect application and used the Demo function, which allowed me to dial in a temperature of -20C. As you said 12VMan, there's a warning that going below 5C will void the warranty. The Manual for the batteries provides the same advice. Warranty is three years for these batteries.

I've been comparing this 'feature' of the Victron lithium batteries with Mastervolt equivalents. From what I can see, Mastervolt do not have the same warranty voiding provision for charging at temps below +5C, though they do suggest that doing so is not ideal for battery health. Mastervolt advises that the batteries might not accept charge at below -5C. Their warranty is two years.

The Victron and Mastervolt batteries use the same chemistry. Is anyone aware of any technical reason why their health status wouldn't follow a similar trajectory if charged similarly in cold conditions?

I'm talking with high latitude sailors to see what their bilge temperatures looked like in icy fjord conditions. :-|

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jwfrary avatar image
jwfrary answered ·

@Valden I’m sure I read an article in the victron blog not so long ago where they used a heat matt to get the battery box up to the required level.

You may have to insulate the box in some way so that your preventing the worst of the cold from the bilge transferring to the batteries, indeed your in trouble if the inside of the boats getting down to 5deg anyway,

have you thought about additional starting power for your main engine as at low temps lead acids have reduced performance.

You could run a small coolant circuit under the box, or be sneaky with your plumbing so that the calorifier plumbing runs under your battery box might be just enough to get you above the threshold.

I have worked in the Baltic in the winter a fair bit on ships that were supposedly designed to work in those temps and we had lots of trouble with things getting to cold. - electric heating and have systems just don’t work! That’s why all the Baltic trawlers have a refleks stove! - no electric!

all solvable in a yacht though I think, especially where your accommodation heating will lend itself to raising the temp of your equipment to some degree.

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valden avatar image valden commented ·

Hi Jw. Thanks for these thoughts. Very helpful.

Yes, I'm considering a heat mat for the battery box. It'll use electricity though, which is potentially a trap. Also, our yacht will have a Webasto diesel fan heater with hydronic reheating at the outlets (better for even heating and condensation control than Reflex, not to mention a toasty warm bathroom!), which is also a potential trap, given it uses electricity!

Here's a question an engineer at Victron might know the answer to.

- Re batteries being cold and/or at a low SOC, in what condition(s) does the 12.8V 300Ah lithium battery's Bluetooth chip stop working? Extra-low SOC is my guess.

Experienced Arctic sailors are telling me that keeping batteries that are installed in a sub-floor battery box above +5C will be a challenge in winter. Water temperatures in Arctic Norway will be in the +1 to +2 range. Overnight surface icing can occur in some fjords due to radiative heat loss, but doesn't lower the subsurface temperature, to which the boat's bilge is tied. Nevertheless, batteries shouldn't be positioned against the hull at the waterline. Ours won't be.

Raising the temperature of 200+kg of battery thermal mass that's positioned in an ice box, tied to an unlimited thermal mass (the ocean) is something of a losing game. Insulation can only help if heat is added.

- Re question 4 in my original post, how much heat do the batteries generate themselves from being used?

An ongoing low level of discharge will occur while we're anchored (radio, lights, heater fan, hydronic pump, fridge/freezer, laptop chargers), with occasional bursts of higher discharge (microwave, kettle, ... hair-dryer!).

The batteries' self generated heat, together with battery-box insulation, maybe a heat mat or similar, and leakage of ambient heat from the occupied spaces of the boat, might just be enough.

I need information, to keep Victron lithium batteries in this evaluation.

I have been impressed overall with Victron's provision of information about its products, but in this instance it is not keeping up with Mastervolt. Have a look at Mastervolt's manual for its lithium batteries and you'll see what I mean. Full disclosure about low temperature performance.

OceanVolt are teamed with Valence, Cleantron and Victron. Valence advise that if their batteries are to be charged at below 0C, keep the charging rate to below 40mV.

- How can I get more information about performance (including charging) of Victron lithium batteries in conditions below +5C?

- Is there anything intrinsic to the design of Victron lithium batteries that causes the very conservative minimum charging temperature of +5C?

I will talk today with Australia's national importers for Victron and Mastervolt. Perhaps they've helped equip our Antarctic Division.

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danielw avatar image
danielw answered ·
Hi Valden and Ur12VMan,

I'm also very interested in this temperature problem.
If you check Winston batteries, they allow charging to -45°C, as far as I remember. All of them are LiFeYPO4, the Yttrium is responsible for low temperature chargeability.
Victron used to use Winston cells... the new, very small and light Victron Smart Lithium batteries use different cells, don't know which. But still LIFeYPO4, if the datasheet is right.
I can't see the reason why Victron limits it to +5°C, which would be correct for non-Yttrium doted Lithium chemistry. I would love to read a statement from Victron.

Heating the battery "by itself" = electrically is kind of weird.

Thanks

Daniel
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iand avatar image iand commented ·
That's not correct, the Winston data sheets show *discharge* curves down to -45C but carefully omit any mention of minimum charging temperature... :-(


The oft-quoted "minimum charging temperature" of 0C (or +5C) is not actually a hard limit, what happens is that as the temperature drops the maximum allowed charging current also drops, but most manufacturers don't provide any details of this because it could open up a warranty claim can of worms for them -- so they specify the temperature down to which you can charge at maximum current, and cut off charging below that.


Some with built-in BMS allow charging at lower temperatures, for example, the BYD LVL 15.4 battery says minimum operating temperature is -10C, but notes that charge derating will occur between -10C and +5C -- without giving details of how much, because the BMS is internal.


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ponzoa avatar image ponzoa iand commented ·
My understanding is that lithium will allow discharging at virtually any temperature, and their brochures play with this. The problem is charging. As they get closer to zero, they accept less and less and in theory, charging at above a certain amount of mA while below 0ºC will damage the chemistry of the battery hence you'd be able to throw it away.


If this is true, I suggest seeking to keep them at 10ºC or above which should be manageable if the rest of the vessel is we'll insulated. As you mentioned, the water temp will average at about 2ºC in winter but your bilge (as long as it's not against the hull) should stay at or above 5ºC. I would definitely have a system to be abale to heat them though if they get below say 8ºC as they start to reduce their acceptance of charge from above that.

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michelg avatar image
michelg answered ·

Hi everybody !

Suggestion, take a look at Dometic / Waeco Tropicool coolers. They offer an insulation which is pretty good, AND they have a Peltier element. You can select a HOT temperature to keep your batteries warm, and using a supplementary solar panel to provide the energy for the cooler.

It could be an option. Here is the link :

https://www.dometic.com/en/se/products/food-and-beverage/coolers/electric-coolers

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marekp avatar image
marekp answered ·

@IanD

I have Winston cells and I asked manufacturer for the low temperature specification.

They set me this chart.

image00105-16-110-12-11-48-31.png

But in the written answer they stated as follows:

Yes, our battery can work in low temperature.The temperature range of charge & discharge of our battery is -45℃ to 85℃. To operate the battery performance better, we suggest that the customer do heating function when the ambient temperature is below 0℃ (depending on the customer's design conditions).

and

When charging, if the battery temperature is lower than 0 °C, the battery capacity will not reach the standard power, the battery's cycle life will decrease,this is a characteristic of all of batteries in the world, so we recommended that the battery charged at room temperature will be better, cycle life will be better.

As you can see the table say that charging at -25C is OK but they do not recommend it. :)

If low temperature operation is required the LTO battery is much better choice.


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valden avatar image valden commented ·
Hi marekp and others.

If I recall correctly Victron’s specification for the minimum allowable battery temperature during charging is 5C. If a battery in the bank is below this temperature it will trigger an alarm with the BMS. A lower temperature for charging can be set via Bluetooth connection to the battery with the Victron Connect app, but doing this will void the warranty.

Last winter our aluminium boat was out of the water for several weeks on a few occasions and was therefore exposed to colder temperatures than if it had been in the water. As a result the bilge spaces were colder than we had previously noticed. On a few days the overnight temperatures were going to be low enough to cause the battery temperatures to drop below 5C. My strategy was to get some heat into the batteries during the day and early evening, by discharging them more than usual (down to 30%) then charging them with a faster than usual charging current, but still well within the recommended maximum rate. The effect of this was that the batteries self heated during charging and started the cold nights with higher temperatures and did not fall below 5C. Another option would have been to put a small fan heater in the bilge, but that didn’t appeal to me. Heating mats under the batteries would be better.

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marekp avatar image marekp valden commented ·

@Valden

My battery is located in the unheated utility building and when in winter outside is -25C inside is close to it.

To keep my battery warm I build a Styrofoam box and inside is small 12V fan on one end and 60W infrared bulb directed at aluminum heat sink. Bulb is controlled by thermostat.

Last winter this heating system used around 900Wh in 5 months to keep 18C inside. It would probably be much less if I set the temperature to 10C or less.

6xmpii.jpg

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valden avatar image valden marekp commented ·
Hi Marekp. That’s a very nice solution. 900Wh seems to be a very acceptable consumption to achieve the temperature profile you did, in those conditions. I agree that you could drop the temp in the box a fair bit lower, while keeping an eye on the internal battery temps via Bluetooth.
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ludo avatar image
ludo answered ·

As your life depends on these batteries, I'd forget Lifep04 and would go the dependable way with AGM or Gel.

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marekp avatar image marekp commented ·
@Ludo

LTO is much better choice.

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ludo avatar image ludo marekp commented ·
I have no idea what LTO is ?
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ludo avatar image
ludo answered ·

But if you can get LTO only as 4Ah round cells you need too many connections, every connection is a potential problem. Also you'll need a lot of balancers etc. I prefer cell's with 200+ Ah.

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marekp avatar image marekp commented ·

@Ludo

Here is a source for bigger LTO cells.

https://shop.gwl.eu/LTO-technology/

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ludo avatar image
ludo answered ·

Yes, but still only 30Ah, and the supplier is giving the bad advice to use cells in parallel. In this way single cell faults will go unnoticed, in th RV community we have lots of customers that have problems with their capacity, most of the time one cell of the parallel array is dead.

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marekp avatar image marekp commented ·

@Ludo

Tesla battery does not have a problem with parallel setup.

In parallel setup cell would have to fail open to be not noticed but even than you will see it at capacity.

But you will do what suits you. :)

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