Low temp protection and dump load?

[NorthTown2022]

Having only remote access for extended periods I have concerns of my battery going into low temperature protection. I'd like to have the ability to defer unused solar to heat a small space.

Perhaps a long shot but is there a way to have a condition set to dump load if battery is in protection?

I've got spare panels and Victron MPPT if that helps but at this point I'd prefer to use the existing 3650W array.

 

[MisterSandals]

I have concerns of my battery going into low temperature protection.

Have you considered digging down below frost line and housing your batteries there?

 

[NorthTown2022]

Have you considered digging down below frost line and housing your batteries there?

Yes I've thought about this many times. I have a full size backhoe to do the digging as well but I am only 5' from the water table. That would also be a job I don't have time for this year. I'd like to get a little something setup soon even if its temporary for this year.. unfortunately winter will be here soon.

Dump load from Victron MPPT, 48V contactor, thermostat and a LARGE resistor? It would be nice if I could run this even if BMS has battery in protection..?

 

[MisterSandals]

It would be nice if I could run this even if BMS has battery in protection..?

What BMS? How would the BMS signal some other device that it was in a particular state?

My simplest idea is to have a temp sensor in close proximity to the sensor your BMS uses and use that as a proxy signal. If one thermostat is at 32F, the other one should be too and it doesn't matter if the BMS has actually gone into protect, you don't want to charge it regardless.

So if your proxy thermostat detects 32F (or whatever you are comfortable with, 35F?), then you could divert power from solar to your LARGE resistor. (i still like the idea of a hot water heating element in water)

I dunno, just brainstorming.

 

[NorthTown2022]

What BMS?

I'm using a JBD AP20S003S contactor type and WITHOUT heat function.

How would the BMS signal some other device that it was in a particular state?

Was thinking.. hoping.. maybe there would be some sort of MPPT logic that could dump load if the battery was in a disconnected state but revert back to set dump load parameters if the battery is not in protection. Yeah probably a little unrealistic.

My simplest idea is to have a temp sensor in close proximity to the sensor your BMS uses and use that as a proxy signal. If one thermostat is at 32F, the other one should be too and it doesn't matter if the BMS has actually gone into protect, you don't want to charge it regardless.

So if your proxy thermostat detects 32F (or whatever you are comfortable with, 35F?), then you could divert power from solar to your LARGE resistor. (i still like the idea of a hot water heating element in water)

My goal is to get heat in the space regardless of SOC. I am hoping to use the existing array for this if battery is in protect due to several days of nasty weather. At least once the sun starts to shine and panels are clear I can start with heat and then a charge.

Perhaps I just don't fully understand how this works yet and I'm probably over complicating things as well ? maybe I should be setting up a couple of them 445W panels in parallel and going direct to a 50V DC thermostat (if that exists) to the load, similar what you suggested in my other thread.

I like water for the thermal mass it would provide but extra work right now. I suppose this could this be done with glycol in a sealed tank (with a relief of course)?

I dunno, just brainstorming.

Appreciated!

 

[lifthouseb4windows]

I am here and stuck with what seems to be ai.ilar issues. Not enough battery bank to mess with a water heater timer and go away for a few days and hope for sunny days during the timing, without coming back and discovering drained batteries. I have a 4kW array, 48V500Ah APS, 5kW off grid with grid-tie hybrid MPPT all-in-one charger/solar controller, which has some COM ports and a little 12V signal port to start a generator. I must be home during the middle daytime to turn on the hot water heater, take a shower, and then turn it off.
I wonder how to automate this, purchased a dump load relay device that dumps whenever the charge controller is trying to float charge, and the two seemed to be fighting each other. Might just buy a new system that has a hardwired dump load already built into it but it seems that if my system is grid-tie-able then why can't I use it to sell back to myself and call the "AC-IN (from utility grid)" an "AC dump load" and connect it to an AC hot water heater so that my inverter/charger can use it's pre-existing circuitry to decide when to "sell" extra AC power when batteries are nearly full? Silly but serious idea, good thing I haven't blown myself up, yet. If I was more confident and liked tech better, I'd learn raspberry pi and coding and hack things, but I'm looking for simpler solutions. I'd install an MPPT switch that reads when my charging voltage is nearly at max for the day and read my batteries and decide how much to offset to a "grid" OR a "dump load.". It seems possible, would really love help,

 

[MisterSandals]

I wonder how to automate this, purchased a dump load relay device that dumps whenever the charge controller is trying to float charge, and the two seemed to be fighting each other.

I wonder if your rebulk charge voltage is too close to your float voltage. In such a case your dump load may be significant enough to draw down from float voltage quickly and your SCC goes into bulk charging (and stop dumping load).

What are your charge settings and how many amps is your dump load?

 

[lifthouseb4windows]

I wonder if your rebulk charge voltage is too close to your float voltage. In such a case your dump load may be significant enough to draw down from float voltage quickly and your SCC goes into bulk charging (and stop dumping load).

What are your charge settings and how many amps is your dump load?

I think the problem is mixed. The batteries were reconditioned and fell out of sync from day one, even though I applied a constant passive-inline desulphation frequency, and connected all the terminals to each respective positiv, etc in order to to try and harmonize a motley lot of 12 AGM 12v90A truck batteries which I chose because of replaceability in the long run, set in legs of 48v so that's 300A supposedly. I haven't grounded the battery bank yet and am learning that it is done, and sometimes in the positive side but not without knowledge. The charge controller handles up to 80A charging and I have it set to 40 because I believe the charge should not be over 15% of the bank capacity. I am learning how to manage my batteries individually and in series and still have a lot to learn. I can see the possibility that a motley mix of ages of similar batteries confuses the system into never reading a useful charge value.

 

[McKravitts]

Yes I've thought about this many times. I have a full size backhoe to do the digging as well but I am only 5' from the water table. That would also be a job I don't have time for this year. I'd like to get a little something setup soon even if its temporary for this year.. unfortunately winter will be here soon.

Dump load from Victron MPPT, 48V contactor, thermostat and a LARGE resistor? It would be nice if I could run this even if BMS has battery in protection..?

Instead of putting your batteries bellow the frost, you could bring the heat from below the frost line up to your batteries using heat pipes. They are extremely high efficiency heat transfer devices and require no external power.

Nasa uses them to control the temperature of spacecraft components. I used one to keep a fishing hole open in the ice all winter. I placed one end of a heat pipe about 3 feet under the surface of the ice and other end just at the top of the ice line.
Since your water tabkle is just 5 feet down there should be plenty of heat (water has a very high heat capacity).

 

[NorthTown2022]

Instead of putting your batteries bellow the frost, you could bring the heat from below the frost line up to your batteries using heat pipes. They are extremely high efficiency heat transfer devices and require no external power.

Nasa uses them to control the temperature of spacecraft components. I used one to keep a fishing hole open in the ice all winter. I placed one end of a heat pipe about 3 feet under the surface of the ice and other end just at the top of the ice line.
Since your water tabkle is just 5 feet down there should be plenty of heat (water has a very high heat capacity).

Interesting..

 

[McKravitts]

Interesting..

Do you know the temperature of the below ground water?

 

[OzSolar]

Here's an interesting idea from the company that invented a passive solar tracker back in the 80's. I'm not saying it's affordable but it it really cool. I know of some that are 20 years old and still working.

"The sun’s heat moves liquid from side to side. This action allows gravity alone to turn the Track Rack to follow the sun—therefore no motors, no gears and no controls to fail."

Here's their battery enclosure. No mention if it can keep a LFP from freezing in Canada as I think it more for reducing extremes. Still the concept is sound.

Cool Cell® – Battery Enclosure – Electronics Enclosure | Zomeworks Corporation

Zomeworks features the Cool Cell, a highly insulated, passively cooled, outdoor battery enclosure. A water reservoir cools this electronic enclosure,

www.zomeworks.com

 

[NorthTown2022]

Do you know the temperature of the below ground water?

I do not but I'm very curious. Got a shallow tile well and will drop a sensor down mid February if I can make it out there!

 

[NorthTown2022]

Here's an interesting idea from the company that invented a passive solar tracker back in the 80's. I'm not saying it's affordable but it it really cool. I know of some that are 20 years old and still working.

"The sun’s heat moves liquid from side to side. This action allows gravity alone to turn the Track Rack to follow the sun—therefore no motors, no gears and no controls to fail."

Here's their battery enclosure. No mention if it can keep a LFP from freezing in Canada as I think it more for reducing extremes. Still the concept is sound.

Cool Cell® – Battery Enclosure – Electronics Enclosure | Zomeworks Corporation

Zomeworks features the Cool Cell, a highly insulated, passively cooled, outdoor battery enclosure. A water reservoir cools this electronic enclosure,

www.zomeworks.com

I'm getting a permission error trying to open the link.

 

[OzSolar]

I'm getting a permission error trying to open the link.

It works when I click on it. Go to zomeworks.com and look around.