8 replies to this topic

[Stokeme]

I’m getting a PowerUrus 100ah lfp4 battery built by RoyPoy w/BT. Bought off site, hope they ship it. It’s vid rated thumbs up. Construction looks good. Also looking at a Renogy 1000w pure sine inverter.
https://www.amazon.c...Y2s9dHJ1ZQ&th=1
If I build a portable with everything thing needed, inverter, controller, input & output accessories, I’m looking at this heater … Caframo True North Heater, it’s a recommended marine unit.
https://www.caframob...load/link/id/10
https://www.amazon.c...DKIKX0DER&psc=1

I am looking at spending less (in my mind) on solar renewable heat & not be subject to propane or diesel. Plus can use the Battery elsewhere. Anyone using this or anything similar?
Hey Vic … can you help out with an easy rule of thumb for the electrical challenged. With the 3 settings … 600, 900, up to 1500W, how does that W convert to nightly aH battery usage? I get aH aspect I think or should I be looking at it differently? How long can my battery/inverter setup keep the heater going?

Edited by Stokeme, 05 April 2023 - 11:07 PM.

[Vic Harder]

Sure, I can do that.  I don't think you will like the results though. Let's start with the lowest heat setting, 600W.  Watts is a power measurement, the result of multiplying Volts times Amps.  So 600W = 60*10 = 6*100, or in this case, 12V*50A or 120V * 5A.  100AH = 50A * 2 Hours.

 

Your 100AH lithium battery, if you could use all 100AH, would give you 2 hours at 600W of heat.  That's it.  

 

Now that won't happen, because you have 5% or so power loss from converting 12V to 120V, and will be running some lights/etc and want a bit of safety margin built in.

 

Another factor is your choice of a 1000W inverter.  You can't even use this heater at full power. 900W is near the max output of your inverter.  (This is why I have an AIMS 3000W Pure Sine inverter for our 1800W induction cooktop).  If you decide to get a bigger inverter so you can run the heater at full power, keep in mind that the lithium battery has a BMS which limits the maximum draw on the battery.  That's why I have two Battle Born 100AH batteries, they can put out 100A each, allowing me 200A * 12V = 2400W of max power draw.  

 

Let's run through the math for my induction cooktop at 1800W to help drive this home.  1800W = 12*150A.  If I run the cooktop for one hour, I'll have 50AH left (assuming no losses or reserve power).  Make sense?

 

Granted your heater won't have to run all the time, but still, the ability to draw large amounts of electrical power from a truck/camper is possible if your battery bank is big enough, but your recharge times get longer too. I have 330W of solar that I've seen upwards of 300W from even up here in frozen Calgary this spring.  300W is going to take how long to recharge my one hour of cooking time?  300W = 12V*25A.  150AH = 25A*6 hours.  Possible, but most of a sunny day.  

 

And this is for a piddling small cooktop/heater, never mind an EV!!!

Edited by Vic Harder, 05 April 2023 - 11:47 PM.

[Jack]

To add to Vic's numbers, there's about 120 kWh in 4.5 lb of propane (a 20 gallon tank or two 10 gallon tanks). There's about 1.2 kWh in a Lithium battery. It would take 100 lithium batteries (100Ah) to provide about the same amount of heat as a tank of propane. It takes about 15 minutes to recharge a tank of propane (say an hour if you have to drive out of your way). If you recharge those 100 lithium batteries from your truck, you are using fossil fuels. If you have effectively 300W solar for 6 hours each day (and all days are sunny), it will take 100 days to recharge the 100 batteries.

 

We have a Toyota Prius Prime (hybrid EV), but in the winter, heating significantly reduces range, and at colder temperatures, the internal combustion engine kicks in automatically.

[Vic Harder]

To add to Vic's numbers, there's about 120 kWh in 4.5 lb of propane (a 20 gallon tank or two 10 gallon tanks). There's about 1.2 kWh in a Lithium battery. It would take 100 lithium batteries (100Ah) to provide about the same amount of heat as a tank of propane. It takes about 15 minutes to recharge a tank of propane (say an hour if you have to drive out of your way). If you recharge those 100 lithium batteries from your truck, you are using fossil fuels. If you have effectively 300W solar for 6 hours each day (and all days are sunny), it will take 100 days to recharge the 100 batteries.

 

We have a Toyota Prius Prime (hybrid EV), but in the winter, heating significantly reduces range, and at colder temperatures, the internal combustion engine kicks in automatically.

You read my mind Jack, I was just going to look up the AH in fossil fuels.   Amazing.

[Stokeme]

Thanks for the electrical breakdown. Appreciate the sobering energy transfer info. Naïveté but at least not too stupid to ask. I already knew about frigid charging, not release of energy with lithium, should have factored in the actual renewable temperature aspect a bit more. Assumed 1000W/100aH, so completely blown up, back to the drawing board.

Edited by Stokeme, 06 April 2023 - 11:53 AM.

[craig333]

Quiet dry heat. Nothing not to like about electric heat. I'll even use it on those rare occasions I plug in. Just not practical for us. 

[Stokeme]

I’m sure it’s in your impressive build thread Vic, but, do you rely only on solar, or do you also travel with a generator? I’m mulling over a dual fuel type with the propane option. Any thoughts on using gas vs propane for a small (maybe cheaper) generator? Yes Craig, dry heat was a goal for me. Might go back to considering diesel, starting from scratch this time.

Edited by Stokeme, 06 April 2023 - 04:16 PM.

[ckent323]

Stokeme,

 

You asked Vic but I will jump in and share our info and experience.

We have one 360 W solar panel, a Victron 100/30 Smart Solar Controller, a BVM-702 Battery Monitor with bluetooth dongle (installed prior to the BVM-712 model being available) and two Lifeline 6V GPL-4 220Ah batteries that provide up to 110AH of energy. 

Since I installed that solar system in 2021 we have not needed any other power source even in Alaska and Canada in September and October.  It replaced a 200 W solar system (and the Victron 75/15 Solar controller) that in certain conditions could not fully recharge the batteries everyday.

However, unlike Vic, We have a propane cooktop and a 3-way refrigerator that is run primarily on propane.  We also have propane heat.  We do have a 12 v refrigerator in the truck cab but it runs off the truck electrical system.  I am confident we could install a 12 v refrigerator and the system would still keep the batteries up.  For better or worse the Norcold 300 propane refrigerator continues to work well.

I hope this information is helpful.

 

Craig

Edited by ckent323, 06 April 2023 - 05:33 PM.

[Vic Harder]

I’m sure it’s in your impressive build thread Vic, but, do you rely only on solar, or do you also travel with a generator? I’m mulling over a dual fuel type with the propane option. Any thoughts on using gas vs propane for a small (maybe cheaper) generator? Yes Craig, dry heat was a goal for me. Might go back to considering diesel, starting from scratch this time.

No generator for us. Rarely plug in either. We keep an sharp eye on the SOC of our batteries and switch to propane for cooking if needed. The induction unit gets used mostly inside, as my spouse is Leary of flames in a tent… someone (??) taught her about that years ago. ;-)