Storing Lithium over winter

[Neeves]

BOATING/FISHING: In and Out of a Deep Sleep

As the title suggest - what to do with your batteries when the vessel is locked down for the winter.

Its of no concern to those of us who sail 365, like Australia, South Africa - but might be an interesting read, or not, for those in higher latitudes.

Jonathan

 

[PaulRainbow]

If your BMS has an on/off button, such as the JK BMS i use, just charge/discharge to 60% and turn the BMS off.

 

[jakew009]

BOATING/FISHING: In and Out of a Deep Sleep

As the title suggest - what to do with your batteries when the vessel is locked down for the winter.

Its of no concern to those of us who sail 365, like Australia, South Africa - but might be an interesting read, or not, for those in higher latitudes.

Jonathan

Absolutely nothing, just make sure they are not left for an extended period of time at a very low state of charge.

 

[shanemax]

Correct me if I am wrong but to charge a Lifepo4 battery at 0c 32F will screw it up so a 150 watt solar panel perhaps putting out 7-10 amps, on a sunny frosty day is not recommended. We have many days in the uk where the temperature dips to minus 10 centigrade especially further north. Just Googled it and Google seems to agree.

 

[geem]

Correct me if I am wrong but to charge a Lifepo4 battery at 0c 32F will screw it up so a 150 watt solar panel perhaps putting out 7-10 amps, on a sunny frosty day is not recommended. We have many days in the uk where the temperature dips to minus 10 centigrade especially further north. Just Googled it and Google seems to agree.

If you buy a decent MPPT, such a Victron. It has a setting for temperature. You set the charge disable function at, say 4degC. It won't charge.

 

[geem]

Absolutely nothing, just make sure they are not left for an extended period of time at a very low state of charge.

Don't leave them at 100% either. The perfect SOC for long term health is 50%. As Paul has suggested. Discharge to 60% and turn off the BMS is a good solution. The natural self discharge will likely see them at 40% by the end of the winter. They will therefore have averaged 50% SOC over the winter.

 

[RunAgroundHard]

There is a recent article on Attainable Adventure Cruising on this subject, somewhat based on this other article: -

Don't murder your batteries, tips for winter storage of LFP batteries

Conclusion from the above Panbo article: -

To avoid being caught in such a situation I have refined my opinion on LFP-battery winter storage to just a few cardinal rules. In my opinion there are only three acceptable practices for LFP winter storage.

If shore power is available leave the battery pack on charge throughout the winter. Set a storage voltage of 13-13.2 volts and leave the charger on. If you want an increased time cushion in case of power loss, use the standard float voltage of 13.5 volts or the manufacturer’s recommended float. Check on the system often to ensure power remains on and the batteries are being maintained. Bluetooth or the Victron VRM remote monitoring is very useful here. Even a 120-volt AC outlet with a small charger will be sufficient. If the battery has self-heating features, you must check on the battery during the initial cold snaps in which the self-heating and charging should have engaged to ensure proper heating and charging. If you anticipate temperatures low enough to initiate internal heaters, ensure there is sufficient amperage available from the charger to power all heaters in the system simultaneously as some heaters in large batteries require 1 to 10 amps to bring the temperature up before a charge will be allowed. In some scenarios that could be a significant amount of power, and more than a small charger can handle.
Remove the batteries. Take them home and put them in a warm place and on charge using a quality charger such as the Victron IP65 or IP22 with storage mode engaged or charge to a mid-level SOC and shut them down. Even in this scenario, you should still check them often.
The least desirable option in my opinion is to charge the batteries to nearly full and secure all possible loads, preferably with battery disconnect switches. Making a checklist for this scenario is particularly useful. It would be wise to check on the batteries weekly for the first month to evaluate power losses and adjust the interval of the visits as needed. Check after prolonged periods of cold weather and charge as required. Routine monitoring is still a must. Sometimes this is not possible with boats that are wrapped and fully winterized. In that case another option is mandatory.
Regardless of what you choose, walking away from the boat for 3-6 months is a bad option. Protect your investment!

You need to subscribe to Attainable Adventure Cruising to read their conclusions.

 

[st599]

Correct me if I am wrong but to charge a Lifepo4 battery at 0c 32F will screw it up

Not just screw it up - it's one of the things that can cause an internal short and thermal runaway.

The big LiFePO4 gensets that you see being used at events, all have internal heaters to keep them above 10C.

 

[PaulRainbow]

All charging sources in a LFP installation should have a low temperature cutoff setting, set it to 4degC (as per post #5)

Some batteries come with inbuilt heat mats, or you can fit your own. You have to weigh up the benefit though, it's OK to spend a little power on a heat mat if you are going to charge with something puts enough power out, like a mains charger, for instance. But, using power on a heat mat to allow a small solar array to operate in cold temps could mean you actually lose power.

 

[Refueler]

Question to Paul and anyone else who may know the answer ...

I bought recently as known a LiFePo4 battery for my E-outboard ... too big and now it serves for various other jobs.

The seller was really pleased to tell me it had built in Heater as well as BMS ... but as there is no instructions with it .. and seller alreadyt showed his lack of expertise in another question .. I ask you guys :

How does the heater work ? Is it triggered by battery being on charge and when temp drops - it activates ?

 

[geem]

Question to Paul and anyone else who may know the answer ...

I bought recently as known a LiFePo4 battery for my E-outboard ... too big and now it serves for various other jobs.

The seller was really pleased to tell me it had built in Heater as well as BMS ... but as there is no instructions with it .. and seller alreadyt showed his lack of expertise in another question .. I ask you guys :

How does the heater work ? Is it triggered by battery being on charge and when temp drops - it activates ?

With a JK BMS, if the low temperature setting is acrivated within the BMS, the BMS will use any connected charging device to first send amps to the heater circuit until the temperature is high enough to allow normal charging of the battery

 

[PaulRainbow]

There is a recent article on Attainable Adventure Cruising on this subject, somewhat based on this other article: -

Don't murder your batteries, tips for winter storage of LFP batteries

Conclusion from the above Panbo article: -

To avoid being caught in such a situation I have refined my opinion on LFP-battery winter storage to just a few cardinal rules. In my opinion there are only three acceptable practices for LFP winter storage.

If shore power is available leave the battery pack on charge throughout the winter. Set a storage voltage of 13-13.2 volts and leave the charger on. If you want an increased time cushion in case of power loss, use the standard float voltage of 13.5 volts or the manufacturer’s recommended float. Check on the system often to ensure power remains on and the batteries are being maintained. Bluetooth or the Victron VRM remote monitoring is very useful here. Even a 120-volt AC outlet with a small charger will be sufficient. If the battery has self-heating features, you must check on the battery during the initial cold snaps in which the self-heating and charging should have engaged to ensure proper heating and charging. If you anticipate temperatures low enough to initiate internal heaters, ensure there is sufficient amperage available from the charger to power all heaters in the system simultaneously as some heaters in large batteries require 1 to 10 amps to bring the temperature up before a charge will be allowed. In some scenarios that could be a significant amount of power, and more than a small charger can handle.
Remove the batteries. Take them home and put them in a warm place and on charge using a quality charger such as the Victron IP65 or IP22 with storage mode engaged or charge to a mid-level SOC and shut them down. Even in this scenario, you should still check them often.
The least desirable option in my opinion is to charge the batteries to nearly full and secure all possible loads, preferably with battery disconnect switches. Making a checklist for this scenario is particularly useful. It would be wise to check on the batteries weekly for the first month to evaluate power losses and adjust the interval of the visits as needed. Check after prolonged periods of cold weather and charge as required. Routine monitoring is still a must. Sometimes this is not possible with boats that are wrapped and fully winterized. In that case another option is mandatory.
Regardless of what you choose, walking away from the boat for 3-6 months is a bad option. Protect your investment!

You need to subscribe to Attainable Adventure Cruising to read their conclusions.

There's a couple of things wrong in that article, in my opinion.

1. "Set a storage voltage of 13-13.2 volts and leave the charger on. If you want an increased time cushion in case of power loss, use the standard float voltage of 13.5 volts"

13v is OK, 13.2V is getting a bit high, 13.1V would be better.13.5V is too high, It is going to hold the batteries at almost 100% SOC. Very bad.

2. "charge to a mid-level SOC and shut them down", that's correct, but contradicts 1 above if you use 13.2V or even worse 13.5V.

3. "The least desirable option in my opinion is to charge the batteries to nearly full and secure all possible loads, preferably with battery disconnect switches."

Using 13.5V for storage and leaving the charger on (see point 1) is even worse than this.

 

[lustyd]

All charging sources in a LFP installation should have a low temperature cutoff setting, set it to 4degC (as per post #5)

Just being pedantic but if there is a heater as per second half of your post this will prevent it from working so the above should have that caveat and only be set if no heater is present in the battery or if solar as you said.

 

[PaulRainbow]

Just being pedantic but if there is a heater as per second half of your post this will prevent it from working so the above should have that caveat and only be set if no heater is present in the battery or if solar as you said.

Yes, good point.

 

[jakew009]

Don't leave them at 100% either. The perfect SOC for long term health is 50%. As Paul has suggested. Discharge to 60% and turn off the BMS is a good solution. The natural self discharge will likely see them at 40% by the end of the winter. They will therefore have averaged 50% SOC over the winter.

I have literally thousands of EVE LF280K cells intentionally held at 100% (~13.65v) permanently on mains standby applications. There is no measurable loss of capacity even after a couple of years beyond calendar aging.

 

[geem]

I have literally thousands of EVE LF280K cells intentionally held at 100% (~13.65v) permanently on mains standby applications. There is no measurable loss of capacity even after a couple of years beyond calendar aging.

It will happen. But it might take 5 years.
13.65v is not the same as being held at 14v as some do. If you are on standby mode you need the battery capacity to be available. This isn't the same as storing them for longevity. Since the lifepo4 curve is so flat, voltage hardly moves from 20 to 80%. Only by discharging them to 60% can you be certain of the SOC for storage. Voltage can be misleading.
On a boat with solar in daily use, we charge to 14v then float at 13.4v (actually double that as we are 24v). This isn't really float. It takes about 8% of the battery capacity to drop back to 13.4v. It simply keeps us out of the fully charged storage mode for better battery life.
we hope to have our batteries in use for many years to come. So far we have only done 130 cycles and that is with everything running from them. Watermaker, immersion heater, cooking, kettle, and all normal boat loads

 

[PaulRainbow]

I have literally thousands of EVE LF280K cells intentionally held at 100% (~13.65v) permanently on mains standby applications. There is no measurable loss of capacity even after a couple of years beyond calendar aging.

But as you are using them for standby applications you don't really have the option to maintain them at 60%, or you'd need twice as many cells, if keeping them at 100% shortens their life a little, so what, it isn't going to halve their lives. But keeping boat batteries at 100% SOC for Winter storage would make no sense, it shortens cell life for no benefit whatsoever.

 

[geem]

I have literally thousands of EVE LF280K cells intentionally held at 100% (~13.65v) permanently on mains standby applications. There is no measurable loss of capacity even after a couple of years beyond calendar aging.

What temperature are you storing the standby batteries at? Have you done full certified capacity tests on the batteries since they were installed?
The design of the standby pack should really be based on 13.4v not 13.65v in my opinion. This would give way better life. Also storing at circa 15degC would.d help battery life but would reduce available Ah when you need it

 

[lustyd]

Keeping batteries half charged on a boat used half the year. Might be better value overall to use everything to its potential

 

[geem]

Keeping batteries half charged on a boat used half the year. Might be better value overall to use everything to its potential

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