Truma electric Combi with Induction Cooking and similar systems for off-grid expedition trailers?

[Sid Post]

I am considering an all-electric Expedition trailer configuration. This does not mean I won't have other cooking or heating options, but the base trailer itself would be all electric. With solar panels and vehicle charging, eliminating LP tanks on my travels seems like a good idea, at least initially.

The Truma electric Combi covers the basics for heat and hot water, and an Induction cooktop is a reasonable option in RVs and OTR Trucks today, so likely a reasonable and reliable option too.

I can add ~1,000 watts of solar panel capacity to my tow vehicle in addition to whatever my trailer has. An Anderson connector would add 30A service if needed for extended stationary needs. Batteries would be sized to the total load, so I will skip battery specifics here.

And yes, I have a lot of experience with Solar off-grid systems, so I am well beyond the basics here. My mobile solar experience is not as extensive, though I run an uprated alternator now in my tow vehicle, and I have done limited solar in the past.

Thoughts for and against an all-electric Expedition Trailer?

TIA,
Sid

 

[SBSYNCRO]

I have two friends with all electric Sprinters set up similarly (though one uses a diesel heater for cabin heat). Both of them regret relying on electric for heating. The cooking doesn't seem to be as big of a problem, but both of them can only have hot water for VERY brief periods and only when they are sure they will either be driving before they need it again or there is very reliable and strong sunshine. One buddy has 400 ah of lithium batteries and heating enough for a single shower (or two very short navy showers) knocks his power down to something like 60% from full. The first time he told me that I was shocked. Personally I would never go that route for cabin or water heating, but I'd consider it for cooking.

I assume you're looking at the Truma Combi Eco Plus (or Comfort Plus, which is higher output). Those are not designed to run in purely electric mode unless on shore power (110 AC). On 12v they are a hybrid LPG/electric system. Let's say you "forced" the shore power mode using 12v batteries and an inverter:

Assume 40% duty cycle over 8 hours to maintain temps at night and 90% inverter efficiency, along with 80% max battery utilization. At low mode (the Eco Plus) you run at 850w, which would be 2.72 kWh overnight consumption (315 amp hours at 12v). If it's a "Comfort Plus" running in high mode that number becomes 5.44 kWh (630 amp hours at 12v). Add in fan controls and some overhead and you're probably at about 330 amp hours or 650 amp hours, depending on the mode. So if you had a 500 amp hour battery pack (which is massive in normal terms), you'd be consuming about 83% of your usable storage overnight. (e.g. you'd wake up to a 17% battery remaining). If you run the Combi Eco Comfort, you'd need a minimum of 1,000 amp hours of battery storage. All that says nothing of running any other electrical demand (lighting, water pump, etc). Replenishing this draw each day is going to take either a massive alternator and a good long drive, a massive solar array (minimum 850w and perfect conditions for the low output scenario), or a dino fuel-powered generator...

Compare this to using the same units in the manner in which they are designed (hybrid electric+LPG):
Electric is only used for fan control (average current 1.6A | transient max 6.1A according to documentation). 8 hours at 40% duty cycle 1.6 x 8 x 40% =only 5.12 ah literally 100x less than trying to do it in all electric mode.

I don't understand this obsession with "all electric" (home or RV). It's just too inefficient when compared to burning propane or diesel when you consider the money and weight invested in a system that can handle the loads. (also a lot more complicated to build and maintain).

 

[workerdrone]

I always wanted to do a system where the engine coolant and house hot water share a heat exchanger...small insulated hot water tank like a 5-10 gallon. Extra points for fitting a mini woodstove or aux heater in the loop that uses same fuel as the vehicle and provides house heat plus ability to pre-heat engine if it's really cold out

Electric heat only makes sense to me if it's something that directly heats your body, like a blanket or vest

 

[Sid Post]

I have two friends with all electric Sprinters set up similarly (though one uses a diesel heater for cabin heat). Both of them regret relying on electric for heating. The cooking doesn't seem to be as big of a problem, but both of them can only have hot water for VERY brief periods and only when they are sure they will either be driving before they need it again or there is very reliable and strong sunshine. One buddy has 400 ah of lithium batteries and heating enough for a single shower (or two very short navy showers) knocks his power down to something like 60% from full. The first time he told me that I was shocked. Personally I would never go that route for cabin or water heating, but I'd consider it for cooking.

I assume you're looking at the Truma Combi Eco Plus (or Comfort Plus, which is higher output). Those are not designed to run in purely electric mode unless on shore power (110 AC). On 12v they are a hybrid LPG/electric system. Let's say you "forced" the shore power mode using 12v batteries and an inverter:

Assume 40% duty cycle over 8 hours to maintain temps at night and 90% inverter efficiency, along with 80% max battery utilization. At low mode (the Eco Plus) you run at 850w, which would be 2.72 kWh overnight consumption (315 amp hours at 12v). If it's a "Comfort Plus" running in high mode that number becomes 5.44 kWh (630 amp hours at 12v). Add in fan controls and some overhead and you're probably at about 330 amp hours or 650 amp hours, depending on the mode. So if you had a 500 amp hour battery pack (which is massive in normal terms), you'd be consuming about 83% of your usable storage overnight. (e.g. you'd wake up to a 17% battery remaining). If you run the Combi Eco Comfort, you'd need a minimum of 1,000 amp hours of battery storage. All that says nothing of running any other electrical demand (lighting, water pump, etc). Replenishing this draw each day is going to take either a massive alternator and a good long drive, a massive solar array (minimum 850w and perfect conditions for the low output scenario), or a dino fuel-powered generator...

Compare this to using the same units in the manner in which they are designed (hybrid electric+LPG):
Electric is only used for fan control (average current 1.6A | transient max 6.1A according to documentation). 8 hours at 40% duty cycle 1.6 x 8 x 40% =only 5.12 ah literally 100x less than trying to do it in all electric mode.

I don't understand this obsession with "all electric" (home or RV). It's just too inefficient when compared to burning propane or diesel when you consider the money and weight invested in a system that can handle the loads. (also a lot more complicated to build and maintain).

Super helpful.

For trailer certifications, liquid fuels are not allowed, so no Diesel heat, my preferred heating source.

Where I am going, propane refills are problematic too. I will have ~1,000w of solar panels and at least 400ah of LiPo4 batteries and a 30A connection from my tow vehicle to charge them, especially on cloudy days. I may end up adding a Honda EU2000i or similar generator if needed to support my travels, as gasoline is relatively easy to get.

And yes, the Truma all-electric heating and water heater is being recommended to me. I still haven't given up hope of adding a "port" to put Diesel heat into my trailer and to save my batteries. Perhaps, I just need to use the dedicated "shore power" AC port and an external gasoline generator.

Regarding the ECO Nazi and Extreme GREEN movements, to say I am not a fan is an understatement. My 55MPG VW Passat polluted less than my 4-cylinder Honda Accord. I do try to make "Earth-friendly" choices in general, though. Energy efficiency and low-impact travel matter to me, within reason and existing technology.

I also have a lot of off-grid solar experience running systems from 12V and 400W to 48V and several thousand Watts.

 

[Sid Post]

I always wanted to do a system where the engine coolant and house hot water share a heat exchanger...small insulated hot water tank like a 5-10 gallon. Extra points for fitting a mini woodstove or aux heater in the loop that uses same fuel as the vehicle and provides house heat plus ability to pre-heat engine if it's really cold out

Electric heat only makes sense to me if it's something that directly heats your body, like a blanket or vest

Electric blankets and vests work really well for me. However, 10F boots are #$%!

As I get older, the difference between a ~60F breakfast table and 10F is SIGNIFICANT!

Water, other than showering, can be dealt with as long as it doesn't freeze. December showers in a Belgian castle with unheated water coming out of the stonework was pretty brutal!

 

[Gravelette]

Propane is widely available in AK and Canada. Seems your best option since the numbers don't work for all-electric.

 

[Sid Post]

Propane is widely available in AK and Canada. Seems your best option since the numbers don't work for all-electric.

Yes, if I were limited to North America, propane is a better option in most cases.
In Central and South America, in more remote areas, propane is a lot more limited. No clue regarding the Australian Outback, but Diesel heaters seem to be popular out there, so I'm guessing outside of major cities, Diesel is generally a better option there too.

 

[Gravelette]

Don't let the perfect be the enemy of the good!

 

[Sparse Gray Hackle]

Don't let the perfect be the enemy of the good!

Said another way, “Seek success, not perfection”. Analysis paralysis is a problem that many of us suffer.

 

[Gravelette]

^^^ I think that one's a better fit! I know we are all hoping this time will finally work out for OP.