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Cold batteries
Posted: Mon Nov 29, 2021 4:01 pm
by Stinsy
My 5x Pylontechs are in the attic which is unheated. Well I have worked very hard to make it as unheated as possible! In the coldest conditions the batteries report a lower max charge rate and the inverter obeys this.
Yesterday I noticed the max charge rate was 50A (10A per battery), I was concerned the batteries might not fully charge in my 4hr cheap widow. However, after c. 70mins the charge-rate increased. I guess they warmed themselves up a bit.
Today they're reporting max charge rate of 95A or 19A per battery. I can only remember seeing 25A per battery or 10A per battery before, I thought there was "normal" and "cold", 19A seems a bit random, does anyone know what values are reported in what conditions?
Re: Cold batteries
Posted: Wed Dec 01, 2021 6:37 am
by Stinsy
Just had a thought. Maybe the top and bottom batteries were cold middle ones were warm. So (25x3)+(10x2)=95. That means we are back to 10A = cold, 25A = normal.
Re: Cold batteries
Posted: Wed Dec 01, 2021 8:19 am
by Mr Gus
Question is, are you tempted to make a seasonal wrap & take some measurements? (to ensure they self warm over this period, akin to a freezers proximity to a wall & waste heat)
A cold loft is very blooming cold, what are your winter & summer extreme numbers thus far?
Re: Cold batteries
Posted: Wed Dec 01, 2021 9:27 am
by Stinsy
The cold isn't really a problem to be solved, I'm more about understanding the behaviour. 5x batteries at 48V being charged at 10A each is 2400W, even if they carried on at that rate for the whole 4hr cheap period I'd still get most of a charge into them. However they warm up while being charged. My inverter/charger maxes at 3.5kW anyway so "coldgating" doesn't slow me down by much.
If I had a 6kW-capable inverter/charger it'd make a bigger difference. But even then I'd prefer buying more batteries over fashioning an insulated (or dare-I-say-it: heated) enclosure.
I wonder what the implications would be if someone was using the batteries without a BMS data connection between batteries and inverter/charger? They could continue to charge the stack at 6kW even though the BMS has "coldgated" them down to 2.4kW. Could the be damaged? Obviously the BMS doesn't throttle the charge-rate without good reason.
Heat is another consideration. A "universal truth" is that batteries don't like heat. The attic sure does get hot in summer. However I've never noticed either charge or discharge rate being throttled in summer. And I've seen plenty of installations of these batteries in Africa, so I'm not sure how much of a consideration this is.
Re: Cold batteries
Posted: Wed Dec 01, 2021 9:55 am
by Joeboy
Stinsy wrote: ↑Wed Dec 01, 2021 9:27 am
The cold isn't really a problem to be solved, I'm more about understanding the behaviour. 5x batteries at 48V being charged at 10A each is 2400W, even if they carried on at that rate for the whole 4hr cheap period I'd still get most of a charge into them. However they warm up while being charged. My inverter/charger maxes at 3.5kW anyway so "coldgating" doesn't slow me down by much.
If I had a 6kW-capable inverter/charger it'd make a bigger difference. But even then I'd prefer buying more batteries over fashioning an insulated (or dare-I-say-it: heated) enclosure.
I wonder what the implications would be if someone was using the batteries without a BMS data connection between batteries and inverter/charger? They could continue to charge the stack at 6kW even though the BMS has "coldgated" them down to 2.4kW. Could the be damaged? Obviously the BMS doesn't throttle the charge-rate without good reason.
Heat is another consideration. A "universal truth" is that batteries don't like heat. The attic sure does get hot in summer. However I've never noticed either charge or discharge rate being throttled in summer. And I've seen plenty of installations of these batteries in Africa, so I'm not sure how much of a consideration this is.
Stinsy, what is your state of health percentage? I am at 96% in year 4. Year 4 being the oldest battery in the stack. Our stack lives in a cold garage and I have my dod set at 90%.
Re: Cold batteries
Posted: Wed Dec 01, 2021 10:05 am
by Mr Gus
By that "seen in africa" do you mean..
Enclosed in africa (roofing materials taken into consideration? (In loft type conditions)
Or, used in African heat ground floor, open exposure but with a chance for breeze to blow through, & presumably shared protection from sun, set to a concrete foundation (floor) to allow for some kind of heat dissipation?
Context is
Cheers
Re: Cold batteries
Posted: Wed Dec 01, 2021 11:08 am
by Tinbum
I have a couple of Growatts in my unheated workshop and have a small greenhouse tube heater 60w under them that I turn on as required for a short time during really cold weather.
The Pylons are going in a separate small insulated room (inside a barn) with the inverters. The heat from the inverters should keep the room warm enough in winter and the barn keep them cool enough in summer.
A BMS connection is certainly required.
Re: Cold batteries
Posted: Wed Dec 01, 2021 1:05 pm
by Stinsy
Joeboy wrote: ↑Wed Dec 01, 2021 9:55 am
Stinsy, what is your state of health percentage? I am at 96% in year 4. Year 4 being the oldest battery in the stack. Our stack lives in a cold garage and I have my dod set at 90%.
I don't have a way to read that information. I'm keen to! How do you get it? I've seen people connect raspberry pis to the "console" port of their top battery but I haven't done that.
Mr Gus wrote: ↑Wed Dec 01, 2021 10:05 am
By that "seen in africa" do you mean..
Enclosed in africa (roofing materials taken into consideration? (In loft type conditions)
Or, used in African heat ground floor, open exposure but with a chance for breeze to blow through, & presumably shared protection from sun, set to a concrete foundation (floor) to allow for some kind of heat dissipation?
Context is
Cheers
The one's I've seen in Africa have been in outdoor/shaded installations. My attic might well get hot in summer (35℃ would be my guess) but I'm sure the ones in Africa (and Australia) get hotter despite them benefitting from a draught.
Re: Cold batteries
Posted: Wed Dec 01, 2021 1:30 pm
by Mr Gus
Thanks stinsy.
I can only throw my own experience of a south & north facing low pitch, low height slate roof (uk) getting into the 40's in summer heat.
Don't guess, get readings & an idea, seasonally. I left one up there to get an idea of loft hatch insulation & general area, plus also when to work up there as it is "crawl space" only ..awkward & uncomfortable through to unbearable.
Re: Cold batteries
Posted: Wed Dec 01, 2021 1:35 pm
by Joeboy
Stinsy wrote: ↑Wed Dec 01, 2021 1:05 pm
Joeboy wrote: ↑Wed Dec 01, 2021 9:55 am
Stinsy, what is your state of health percentage? I am at 96% in year 4. Year 4 being the oldest battery in the stack. Our stack lives in a cold garage and I have my dod set at 90%.
I don't have a way to read that information. I'm keen to! How do you get it? I've seen people connect raspberry pis to the "console" port of their top battery but I haven't done that.
Mr Gus wrote: ↑Wed Dec 01, 2021 10:05 am
By that "seen in africa" do you mean..
Enclosed in africa (roofing materials taken into consideration? (In loft type conditions)
Or, used in African heat ground floor, open exposure but with a chance for breeze to blow through, & presumably shared protection from sun, set to a concrete foundation (floor) to allow for some kind of heat dissipation?
Context is
Cheers
The one's I've seen in Africa have been in outdoor/shaded installations. My attic might well get hot in summer (35℃ would be my guess) but I'm sure the ones in Africa (and Australia) get hotter despite them benefitting from a draught.
It is displayed on the sems portal (goodwe) in the one level down maintenance info. Can you maybe run rs232 and see data on hyperterminal?
