Can you trust the low temp cutoff in EG4 LL?

[xy74]

The battery is in an insulated cabin in southern Ohio. Occasional use. 2-3 weekends a month depending on weather. Obviously not getting a whole lot of solar production now with the sun below the leafless trees until spring, but we get some. But with a full battery, we can run what we need for the weekend. I'd like to leave the charging system running while we are gone so we can return to a hopefully full battery. (The separate inverter would be off, so no drain.) My concern is low temperature in the shoulder seasons. A typical high of 45 and maybe goes down to 25 at night. Doubt it ever goes below freezing inside the cabin then, but what if you get the unexpected night of 10 or 15? Now maybe it does get below 32 inside for a bit. Can I trust the BMS to save the battery in the morning when the sun comes up?

Equipment is 1 EG4-LLv2, Victron 250/60, and 5 295w solar panels in series.

 

[Sharing Society]

I've sent an email to Signature Solar technician asking about charging an LL v2 battery below 32F.
We'll see if they respond

 

[Sharing Society]

@EG4-Jacob @EG4_Jarrett @EG4_Ty

 

[EG4_Jarrett]

If I remember correctly, the batteries have thermistors built into the voltage harness (I can't recall if the LL has thermistors, or a temperature sensor on the BMS board. Ill have to pull one apart to check, but either way it will read the temp). In my experience, the thermistors/sensor do an excellent job of measuring temperature in the battery, and in the surrounding area as well.

As far as charging and discharging in cold temperatures, you can lose some of your capacity. If it's below the temperature protection spec, you want to try and get the battery warmed up above that temperature. The battery will go into protection mode if the thermistors/temperature sensor are measuring the temperature correctly and it's below the Temperature Protection spec. (>14F <149F)

You can discharge at lower temperatures than you can charge though. For charging, you want the battery to be above freezing. The range on that is 32F - 113F. For discharging the battery, the spec on that is -4F - 122F.

TLDR: So long as you are above 32F in the colder seasons, you should be fine to charge the battery.

 

[ryankshaw]

If you're concerned about the low temp protection on the batteries, you could also add a second low temp protection on the PV wire in to the battery. Then you'd have 2 switches that have to be on in order for the battery to charge. so 2 different thermostats have to think it is above freezing and 2 different relays have to be activated.

I just did something similar for my rv build, but it was because my batteries had no low temp protection at all.

here's the general idea:

1. get one of these to measure the temp on the ouside of your battery:
   
   https://www.aliexpress.us/item/3256805806160370.html
   (make sure you pick the one with the right voltage for your system)
2. program that so that when the temperature is above 2 degrees celsius (or whatever safety margin you want), it turns on.
3. have the thing that it turns on be one of these:
   
   https://www.aliexpress.us/item/3256805571568129.html
   (make sure you pick "DD" (dc to dc) option, and the one above the max amps you expect your solar to ever have
4. wire that right between the + of your solar fuse disconnect and the + of your battery
5. with the net result being that unless that thermostat is recording a temp over freezing, you will have no voltage coming in from your solar panels to your battery.

 

[Sharing Society]

If I remember correctly, the batteries have thermistors built into the voltage harness (I can't recall if the LL has thermistors, or a temperature sensor on the BMS board. Ill have to pull one apart to check, but either way it will read the temp). In my experience, the thermistors/sensor do an excellent job of measuring temperature in the battery, and in the surrounding area as well.

As far as charging and discharging in cold temperatures, you can lose some of your capacity. If it's below the temperature protection spec, you want to try and get the battery warmed up above that temperature. The battery will go into protection mode if the thermistors/temperature sensor are measuring the temperature correctly and it's below the Temperature Protection spec. (>14F <149F)

You can discharge at lower temperatures than you can charge though. For charging, you want the battery to be above freezing. The range on that is 32F - 113F. For discharging the battery, the spec on that is -4F - 122F.

TLDR: So long as you are above 32F in the colder seasons, you should be fine to charge the battery.

I received an email from a tech that said
"Unfortunately the battery will not discharge when it is in the protection state."

That seems to contradict what you said that it WILL discharge but not charge if below 32F and above -4F

 

[EG4_Jarrett]

"Unfortunately the battery will not discharge when it is in the protection state."

They are correct. If the battery is in the protected state, it will not discharge.

If the temperature is below 23F, and you apply a charge, then the battery will go into protection. Recover at >32F and <140F.

If the temperature is below -4F and you start to discharge, then the battery will go into protection. Recover at >14F and <149F.



I'll double check with our battery tech, but the battery shouldn't go into protection mode just because the temperature is low.
I have not personally tested a battery at -4, the last time it was -4 in Texas, I was locked in my house because all the roads stayed iced over with no water or electricity for a week because the state of Texas doesn't know how to handle temperatures that are less than 80 degrees ? (I'm still a little bitter about it).

However, I know for a fact that our battery tech has tested this himself and when I get to the office tomorrow, I will double check with him.

As far as charging and discharging in cold temperatures, you can lose some of your capacity.

This is based off of all lithium batteries. This is the purpose of our BMS going into protection mode, so that this does not happen. Should have clarified that in my previous post.

EG4 batteries will got into protection mode if they start to charge or discharge out of the temperature specs listed on the spec sheet of the battery.

 

[HighTechLab]

From my experience and understanding with the EG4-LL V2's operation, you are correct. The temp sensors are mounted on the top of the battery cells, screwed into the bus bars that connect the cells together. There are 4 sensors in total.

I have not personally tested a battery at -4, the last time it was -4 in Texas

Y'all need an environmental chamber then. They are fun. You can make snow in July.

 

[Jack Rabbit Off Grid]

The battery is in an insulated cabin in southern Ohio. Occasional use. 2-3 weekends a month depending on weather. Obviously not getting a whole lot of solar production now with the sun below the leafless trees until spring, but we get some. But with a full battery, we can run what we need for the weekend. I'd like to leave the charging system running while we are gone so we can return to a hopefully full battery. (The separate inverter would be off, so no drain.) My concern is low temperature in the shoulder seasons. A typical high of 45 and maybe goes down to 25 at night. Doubt it ever goes below freezing inside the cabin then, but what if you get the unexpected night of 10 or 15? Now maybe it does get below 32 inside for a bit. Can I trust the BMS to save the battery in the morning when the sun comes up?

Equipment is 1 EG4-LLv2, Victron 250/60, and 5 295w solar panels in series.

Your Victron has an adjustable low temperature charge cut off built in. i don’t know how to use it but see it in my settings.

 

[EG4_Jarrett]

Y'all need an environmental chamber then. They are fun. You can make snow in July.

We've tested it, I just was not a part of that testing. But yes, environmental chambers are fun!

 

[xy74]

If the temperature is below 23F, and you apply a charge, then the battery will go into protection. Recover at >32F and <140F.

If the temperature is below -4F and you start to discharge, then the battery will go into protection. Recover at >14F and <149F.

View attachment 184277

I'll double check with our battery tech, but the battery shouldn't go into protection mode just because the temperature is low.
I have not personally tested a battery at -4, the last time it was -4 in Texas, I was locked in my house because all the roads stayed iced over with no water or electricity for a week because the state of Texas doesn't know how to handle temperatures that are less than 80 degrees ? (I'm still a little bitter about it).

However, I know for a fact that our battery tech has tested this himself and when I get to the office tomorrow, I will double check with him.



This is based off of all lithium batteries. This is the purpose of our BMS going into protection mode, so that this does not happen. Should have clarified that in my previous post.

EG4 batteries will got into protection mode if they start to charge or discharge out of the temperature specs listed on the spec sheet of the battery.

OK, now I am definitely cornfused after reading the manual again as well as your post. It says the low temp charging cutoff is 23f. So does that mean it will allow charging at 31-30-29-28-27-26-25-24? Isn't that supposed to be what we are trying to avoid?? But your last sentence says it won't allow charging out of spec.

 

[xy74]

Your Victron has an adjustable low temperature charge cut off built in. i don’t know how to use it but see it in my settings.

TY. As best I could gather from the Victron manual I need some other gadget accessory to make that work. I may just do that anyway.

 

[xy74]

If you're concerned about the low temp protection on the batteries, you could also add a second low temp protection on the PV wire in to the battery. Then you'd have 2 switches that have to be on in order for the battery to charge. so 2 different thermostats have to think it is above freezing and 2 different relays have to be activated.

I just did something similar for my rv build, but it was because my batteries had no low temp protection at all.

here's the general idea:

1. get one of these to measure the temp on the ouside of your battery:
   
   https://www.aliexpress.us/item/3256805806160370.html
   (make sure you pick the one with the right voltage for your system)
2. program that so that when the temperature is above 2 degrees celsius (or whatever safety margin you want), it turns on.
3. have the thing that it turns on be one of these:
   
   https://www.aliexpress.us/item/3256805571568129.html
   (make sure you pick "DD" (dc to dc) option, and the one above the max amps you expect your solar to ever have
4. wire that right between the + of your solar fuse disconnect and the + of your battery
5. with the net result being that unless that thermostat is recording a temp over freezing, you will have no voltage coming in from your solar panels to your battery.

Didn't see 48v options, but I like your thinking.

 

[Brucey]

TY. As best I could gather from the Victron manual I need some other gadget accessory to make that work. I may just do that anyway.

Get a Victron smart battery sense (SBS) for $40. Connect to battery. Enable it's ve.smart Bluetooth network and then the 250/60 can be configured for low temperature cutoff at temp of your choosing based on the temp returned by the SBS.

 

[EG4_Jarrett]

OK, now I am definitely cornfused after reading the manual again as well as your post. It says the low temp charging cutoff is 23f. So does that mean it will allow charging at 31-30-29-28-27-26-25-24? Isn't that supposed to be what we are trying to avoid?? But your last sentence says it won't allow charging out of spec.

Yes, the battery will allow you to charge until it gets down to 23F (We recommend not charging below 32F as it is the environmental spec we have listed on the spec sheet). By charging and discharging out of spec, I was talking about the parts I had highlighted on the spec sheet.



But if you are charging your battery, and the temperature drops to 23F, it goes into protection mode. If you try to start charging below 23F, it will go into protection mode. 23F is the temperature spec for charging that will throw the BMS into Protection mode in fear of damaging the battery cells.

You want to try and charge above freezing, but there is a spec that will make it so the BMS protects the battery from being damaged, and if you exceed that spec, it will go into protection mode.

 

[xy74]

Get a Victron smart battery sense (SBS) for $40. Connect to battery. Enable it's ve.smart Bluetooth network and then the 250/60 can be configured for low temperature cutoff at temp of your choosing based on the temp returned by the SBS.

Just read the marketing on it and sounds like the ticket. Thanks!

 

[xy74]

Yes, the battery will allow you to charge until it gets down to 23F (We recommend not charging below 32F as it is the environmental spec we have listed on the spec sheet). By charging and discharging out of spec, I was talking about the parts I had highlighted on the spec sheet.



But if you are charging your battery, and the temperature drops to 23F, it goes into protection mode. If you try to start charging below 23F, it will go into protection mode. 23F is the temperature spec for charging that will throw the BMS into Protection mode in fear of damaging the battery cells.

You want to try and charge above freezing, but there is a spec that will make it so the BMS protects the battery from being damaged, and if you exceed that spec, it will go into protection mode.

OK, I think I get it. Seems odd that they wouldn't engineer that cutoff at 32.

While re-reading the manual I again noticed that EG4 suggests storing the battery at 100%. (Seems like many people suggest 40-60%.) Since this will sit idle with zero load a lot, would it be better to leave the solar on all the time or try to leave the battery at a lesser SOC? Any thoughts on that?

 

[EG4_Jarrett]

Most people say 40-60% to store a battery for a whole year. The concern about charging the battery and storing it is more about how long it will take before the battery totally discharges.

If you let it sit, the battery will start to self-discharge. It's just something that batteries do. If you are leaving them at say... a cabin, or a guest house that you don't visit often, then yeah. Charge it to 90-100% and leave it. There shouldn't be an issue. They will stay charged for a long time.

 

[solarenvy]

My "power station" is in an 8'x4' shed just outside my cabin. This houses the inverters (2 x 6000XP) and battery rack (5 x EG4-LLv2). While the shed is well insulated, it can drop below freezing on especially cold nights in central VA. My solution is to keep it comfortably above ~40F with supplemental heat (2 for redundancy): https://www.amazon.com/dp/B0BZ79ZLMP?ref=ppx_yo2ov_dt_b_product_details&th=1

I chose this heater so I can control it remotely and automate as needed while consuming relatively little power needed to keep above the desired temp threshold. When nights are expected to be especially cold, I'll heat the space a little extra during the day to minimize overnight battery drainage. A 2nd heater is plugged into the grid as an emergency backup. It's all automated using temp sensors and device automation.

 

[Brucey]

My "power station" is in an 8'x4' shed just outside my cabin. This houses the inverters (2 x 6000XP) and battery rack (5 x EG4-LLv2). While the shed is well insulated, it can drop below freezing on especially cold nights in central VA. My solution is to keep it comfortably above ~40F with supplemental heat (2 for redundancy): https://www.amazon.com/dp/B0BZ79ZLMP?ref=ppx_yo2ov_dt_b_product_details&th=1

I chose this heater so I can control it remotely and automate as needed while consuming relatively little power needed to keep above the desired temp threshold. When nights are expected to be especially cold, I'll heat the space a little extra during the day to minimize overnight battery drainage. A 2nd heater is plugged into the grid as an emergency backup. It's all automated using temp sensors and device automation.

How much power do you find you use with the portable electric heaters, say for 24 hours?