Can I run 500W baseboard heater on this system?

[Helianthus]

Hello,
First timer seeking help.

My system is 12V :
Lifep04 100ah battery
1000W (2000W peak) inverter (Roarbatt)
Renogy MPPT 30a controller
2 breaker circuit panel
One 240W solar panel

I'm attempting to power a 500W (4.2a) electric baseboard heater. When I turn it on the battery drains steadily and rapidly and within 3-5 minutes Error message flashes on MPPT controller.

Do I need a larger inverter? Larger battery? Are my cables from battery to inverter too small or poor quality (came with inverter)?

Hope this is enough information.

Any help appreciated, thank you.

 

[LeoThomson]

A 100AH will store about 1200W of electricity.

A 240W panel will put out 240W.

A 500W baseboard heater will use 500W

So without any sunlight the baseboard should drain the battery in 2 hours and 20 minutes, if you have sun on the panel, it will last about 4 hours.

Your inverter is plenty big enough, but I do not know why your mppt would flash an error message.

 

[sunshine_eggo]

Yes.

500W/12.8V/.85 = 46A. You'll likely want at least 6awg wire and insure your connections are tight.

12.8V*100Ah = 1280Wh

1280Wh/500W = 2.56 hours from full charge.

Your 240W panel in perfect solar conditions with unshaded exposure from sunrise to sunset should replace about 80% of what the heater uses for the day.

The following day, you may then run it for 2.56 hours * 0.8 = 2.05 hours.

Your battery is likely not fully charged, and when it cuts out, the MPPT flashes error because it can't detect a battery.

 

[Helianthus]

A 100AH will store about 1200W of electricity.

A 240W panel will put out 240W.

A 500W baseboard heater will use 500W

So without any sunlight the baseboard should drain the battery in 2 hours and 20 minutes, if you have sun on the panel, it will last about 4 hours.

Your inverter is plenty big enough, but I do not know why your mppt would flash an error message.

That is encouraging that I'm in the ballpark with my design, thank you, and yes, I'm wondering that as well. Thank you

 

[Helianthus]

Yes.

500W/12.8V/.85 = 46A. You'll likely want at least 6awg wire and insure your connections are tight.

12.8V*100Ah = 1280Wh

1280Wh/500W = 2.56 hours from full charge.

Your 240W panel in perfect solar conditions with unshaded exposure from sunrise to sunset should replace about 80% of what the heater uses for the day.

The following day, you may then run it for 2.56 hours * 0.8 = 2.05 hours.

Your battery is likely not fully charged, and when it cuts out, the MPPT flashes error because it can't detect a battery.

 

[Helianthus]

That may be so, that the battery isn't fully charged, but it is almost fully charged. MPPT showing 92%? Maybe I need to let it top off to start this experiment from 100% full.

Are you recommending 6 gauge wire from battery to Inverter specifically, or, all connecting wiring indoors?

Much appreciated

 

[sunshine_eggo]

That may be so, that the battery isn't fully charged, but it is almost fully charged. MPPT showing 92%? Maybe I need to let it top off to start this experiment from 100% full.

MPPT % reading is voltage-based and completely worthless. Your battery is fully charged when it has been at 14.4V for at least 30 minutes measured at the terminals.

Are you recommending 6 gauge wire from battery to Inverter specifically, or, all connecting wiring indoors?

6awg between battery and inverter.

10awg min between MPPT and battery.

Both suitably fused or breakered.

That is encouraging that I'm in the ballpark with my design, thank you, and yes, I'm wondering that as well. Thank you

Is running this heater for no more than 2 hours per day your goal? The "4 hours" given by @LeoThomson means you are completely empty at that point. You will not be able to run the heater until the battery is charged.

 

[Helianthus]

MPPT % reading is voltage-based and completely worthless. Your battery is fully charged when it has been at 14.4V for at least 30 minutes measured at the terminals.



6awg between battery and inverter.

10awg min between MPPT and battery.

Both suitably fused or breakered.



Is running this heater for no more than 2 hours per day your goal? The "4 hours" given by @LeoThomson means you are completely empty at that point. You will not be able to run the heater until the battery is charged.

Thanks so much for clarifying. I'll let it charge fully and start from scratch. Fingers crossed it is just under charged.

I'll get some 6awg for that connection. I think I have 8 on the rest so should be ok.

Leo was spot on with my own estimations of the parameters of being able to run it 2hrs/day and the recharge up to 80% next day.

I'm sure once I get this started, I'll learn the capacities of the system pretty quickly but I'm just getting going with this being my first system.

Much appreciated, thank you very much!

 

[LeoThomson]

Thanks so much for clarifying. I'll let it charge fully and start from scratch. Fingers crossed it is just under charged.

I'll get some 6awg for that connection. I think I have 8 on the rest so should be ok.

Leo was spot on with my own estimations of the parameters of being able to run it 2hrs/day and the recharge up to 80% next day.

I'm sure once I get this started, I'll learn the capacities of the system pretty quickly but I'm just getting going with this being my first system.

Much appreciated, thank you very much!

Just because our estimates agree, don't assume we are right lol

Have fun experimenting and remember safety first. shorting the battery is not something you want to experience.

 

[Helianthus]

Just because our estimates agree, don't assume we are right lol

Have fun experimenting and remember safety first. shorting the battery is not something you want to experience.

Aha, Good point, but thanks just the same! And, yes, I've been guided by a Master Electrician for the safety aspect. Although he's not deeply versed in solar it's been really helpful and I've learned a lot.

I've been having a great time with the whole process....except for this moment when I wished to be using it. Thank you!

 

[sunshine_eggo]

Curious what application only needs 500W of heat for 2 hours per day...

 

[LeoThomson]

Curious what application only needs 500W of heat for 2 hours per day...

A baseboard heater apparently. You might want to use it heat a campervan or a bedroom to take the chill out of the air in the morning.

 

[Helianthus]

@sunshine_eggo My apologies, I hadn't seen your last comment. I've built a small shed (45sq. ft.) as a music studio. My hope was a small solar system and small heater would be enough to heat it up for the occasional bouts of winter songwriting sessions. After my recent trials, I've concluded it is too small to get up to temp from a really cold start, like 35F, but it can top off the room if starting at a moderate temp like 60F and give me solid performance. I may need to upsize if I want more use out of it from cold starts. Luckily I do have a home and a warm living room.

 

[sunshine_eggo]

@sunshine_eggo My apologies, I hadn't seen your last comment. I've built a small shed (45sq. ft.) as a music studio. My hope was a small solar system and small heater would be enough to heat it up for the occasional bouts of winter songwriting sessions. After my recent trials, I've concluded it is too small to get up to temp from a really cold start, like 35F, but it can top off the room if starting at a moderate temp like 60F and give me solid performance. I may need to upsize if I want more use out of it from cold starts. Luckily I do have a home and a warm living room.

heh... I have a similar (when viewed from a mile away) situation...

I have 10' of an uninsulated 40' shipping container blocked off with a room dividing curtain as a "wall." I have a custom Lithium NMC battery built from Plug-in hybrid batteries. This time of tear, I may find myself with 0-3 hours of PV charging due to low battery temps. If the sun is out, it heats the container up well enough in most cases for afternoon charging, but sometimes I need a little boost.

So I run a 1500W space heater on an Wifi plug I can turn on/off remotely. If it's not too cold (1°-7°C), My system allows for the PV to power loads even if the battery can't charge, so the PV powers the heater until it's warm enough to start charging:




Of course, I have 3kW PV and a big battery. It's really only good for maybe 1°C extra/hour as the R value of a shipping container is about 0.003/in.

 

[Helianthus]

O my, that's serious data right there, wow and that is a significant sized system, awesome.

Nice! Yes, sounds really similar in how my space needs to be managed, I'm glad to know I'm not too far out on a limb. Thanks for the tip on using the battery life to heat the space and battery so it can charge, duly noted.

I have a reeeeally basic question maybe you can answer in your sleep?

Battery is fully charged now and the controller is hopefully shutting down the over voltage charge properly, but what I'm seeing is the controller shuts the PV off and the voltage spikes up on the display to 16v or so, then slowly settles back down to 13.3v and then turns the PV back on. It keeps cycling like this. Is it normal? I thought it would hit a "Float" setting and just stay settled?

I've installed the Renogy BT-1 app and the DC Home app, but manual settings don't seem to alter this cycle. Maybe that's just how it works?

Please let me know if starting a new thread is best for this change of direction. Thanks

 

[sunshine_eggo]

O my, that's serious data right there, wow and that is a significant sized system, awesome.

Nice! Yes, sounds really similar in how my space needs to be managed, I'm glad to know I'm not too far out on a limb. Thanks for the tip on using the battery life to heat the space and battery so it can charge, duly noted.

I don't know if that's applicable to you. I have the PV to run it. I don't think you do.

I have a reeeeally basic question maybe you can answer in your sleep?

Battery is fully charged now and the controller is hopefully shutting down the over voltage charge properly, but what I'm seeing is the controller shuts the PV off and the voltage spikes up on the display to 16v or so, then slowly settles back down to 13.3v and then turns the PV back on. It keeps cycling like this. Is it normal? I thought it would hit a "Float" setting and just stay settled?

No. Your battery is likely out of balance. What is likely happening is that a single cell in the battery is hitting the upper limit, and the BMS is cutting off incoming charge. To the MPPT, it's as though the battery has suddenly been removed, and it can't clamp down on its charging fast enough, so the voltage spikes.

As the battery settles, the voltage drops and the BMS begins to allow charging, so you're getting a "cycling" effect.

The only way to fix this is to return the battery because you can't charge it to the recommended voltage, OR you hold it at the highest voltage the battery can sustain without seeing the voltage spike. Generally, start at 13.8V boost and 120 minute boost duration. Set float to 0.1V below boost. Keep increasing boost until you see the spike. Decrease voltage until it holds that voltage for the two hours (again, float to 0.1V below boost). Keep this up until you can get to 14.4V without seeing the voltage spike.

 

[Bud Martin]

BTW, you did disable the battery equalization function on the Renogy since you are using LiFePO4 battery, correct?

 

[DPC]

@sunshine_eggo My apologies, I hadn't seen your last comment. I've built a small shed (45sq. ft.) as a music studio. My hope was a small solar system and small heater would be enough to heat it up for the occasional bouts of winter songwriting sessions. After my recent trials, I've concluded it is too small to get up to temp from a really cold start, like 35F, but it can top off the room if starting at a moderate temp like 60F and give me solid performance. I may need to upsize if I want more use out of it from cold starts. Luckily I do have a home and a warm living room.

I bought my wife a Chinese diesel heater for her gazebo

40watts of electrical is all it needs

I can understand not wanting to use fossil fuels if that’s your goal

Maybe look at a solar heating system?

 

[LeoThomson]

@sunshine_eggo My apologies, I hadn't seen your last comment. I've built a small shed (45sq. ft.) as a music studio. My hope was a small solar system and small heater would be enough to heat it up for the occasional bouts of winter songwriting sessions. After my recent trials, I've concluded it is too small to get up to temp from a really cold start, like 35F, but it can top off the room if starting at a moderate temp like 60F and give me solid performance. I may need to upsize if I want more use out of it from cold starts. Luckily I do have a home and a warm living room.

I insulated my shed pretty well (but not extreme) and I find it is about 10C (18F) warmer than outside with just me inside it and inverter powering lights, router and PC. A radiant heater will rise the temperature inside, but it is slow. I found an electric blanket draped over my chair will make it comfortable for me while it is 15C (60F)

Maybe an electric blanket as part of the solution will work for you as well?

 

[Helianthus]

I don't know if that's applicable to you. I have the PV to run it. I don't think you do.



No. Your battery is likely out of balance. What is likely happening is that a single cell in the battery is hitting the upper limit, and the BMS is cutting off incoming charge. To the MPPT, it's as though the battery has suddenly been removed, and it can't clamp down on its charging fast enough, so the voltage spikes.

As the battery settles, the voltage drops and the BMS begins to allow charging, so you're getting a "cycling" effect.

The only way to fix this is to return the battery because you can't charge it to the recommended voltage, OR you hold it at the highest voltage the battery can sustain without seeing the voltage spike. Generally, start at 13.8V boost and 120 minute boost duration. Set float to 0.1V below boost. Keep increasing boost until you see the spike. Decrease voltage until it holds that voltage for the two hours (again, float to 0.1V below boost). Keep this up until you can get to 14.4V without seeing the voltage spike.

Aha, I knew something wasn't right. Hope I'm not damaging anything.

B/c it is a space I don't use every day, I think I have the time (and I like a challenge) to try the fix you suggest and monitor it. I'll set it up and see how it goes over the next few weeks. I've had only two fully sunny days in the last two weeks so it's slow going. Very much appreciate the thorough response, thank you.

 

[Helianthus]

BTW, you did disable the battery equalization function on the Renogy since you are using LiFePO4 battery, correct?

I hadn't, but had changed it to 14.4v in USER mode. Ultimately, I reverted back to the stock Li settings in the controller to pay it safe.

 

[Helianthus]

I bought my wife a Chinese diesel heater for her gazebo

40watts of electrical is all it needs

I can understand not wanting to use fossil fuels if that’s your goal

Maybe look at a solar heating system?

Thanks, I'm trying to make it simple with the solar, but if it gets too complicated or is insufficient, I may look to alternate heat sources. I know electric isn't the necessarily the best option for heat in general, but I'd like to not have various systems to maintain in this space if you know what I mean?

 

[Helianthus]

I insulated my shed pretty well (but not extreme) and I find it is about 10C (18F) warmer than outside with just me inside it and inverter powering lights, router and PC. A radiant heater will rise the temperature inside, but it is slow. I found an electric blanket draped over my chair will make it comfortable for me while it is 15C (60F)

Maybe an electric blanket as part of the solution will work for you as well?

Thanks, nice, that's a good idea, and could work while I wait for it to warm up for sure. I have insulated it pretty well with 1.5in panels all around and batting in the walls. Similar to yours it keeps about the same temps higher than outside. Ultimately, I need my acoustic guitars to be happy when I bring them out there...and also my fingers.

 

[Helianthus]

BTW, you did disable the battery equalization function on the Renogy since you are using LiFePO4 battery, correct?

Not sure my prior response went through, apologies if this is doubling up.

I hadn't. I ultimately reverted out of USER mode to the Li settings to play it safe. When I go forward, looks like I should disable Equalization fx in USER mode? Maybe do this before I alter the settings to balance the battery and see if it helps?

 

[yodamota]

Why not try adding one more panel? 480w of solar would make a big difference.