Question Questions Regarding Upgrading to Lithium

[Kevin D Pem]

propane furnace blower (is this AC or DC? and how many amps does it draw? need to find out even though it's intermittent)

12vdc on the blower.

This is what I propose. Not only does my friend have his set up this way but I do, kind of. My solar and inverter/ battery bank is 24vdc and the inverter feeds the rv power cord. this handles all rv loads and charges and maintains the 12vdc battery and system native to the RV

A little about my set up. I use a refrigerator designed and built for apartment use, made by Avanti. I use a portable ice machine during the day. I use an Instant pot and inductive cook top. I have propane stove/oven and propane convective heater (not furnace). I have 1000w of my 2000w available solar. Seems that my almost identical solar controllers don't play together well, so I am waiting for another controller to get here.

With each RV I get I move my system from one to another as I store the unused RV. I have been using this type of set up for about 7 years with no problems. I have also set up such a system for at least 5 other RVers. Only difference between others system and mine is the choice to set up my solar as a 24 volt system, both systems work equally well, I just find adding a independent solar system simplifies the operation as only seldom do I need to plug into the grid and if I do I simply disconnect from inverter and connect to generator/grid.

One more note. I live off grid with my RV. Other than a 2 mo. stent while recovering this last year I could count the number of times I was on the grid sense 2003 on my fingers.

 

[Nomadist]

Ah, so you are suggesting the All Battery/Inverter Model. I'll do some investigation into that.

 

[Kevin D Pem]

Ah, so you are suggesting the All Battery/Inverter Model. I'll so some investigation into that.

Yes I am. I tried to modify the drawing more clearly but allas my software is not up to snuff. So I will show you.
Keep in mind that your charger has higher voltage than the battery produces. What that means is most power will come from the higher voltage connection. When the voltage sags from the 60a charger due to a higher load that It will produce, the remainder of that load will come from the battery. I keep saying this a little different so one of my comments will hit the spot.

I am building a box for this but for now I have power, Living in the same place you are remoding takes some adjusting. This is a 24v inverter, notice I have the house cord connected to the inverter. If I were running a 12v system I would disconnect the charger from the house wiring and run charger cord to the grid or genset If I were using one. My solar keeps up with my loads so I don't even have a cord run outside. I would do that by unplugging the cord from the inverter and sending it outside to plug in. Other than solar I only have a 24vdc poor boy generator that is connected directly to the battery from outside access door. I must admit however that the generator is in storage at this moment. I will have access to storage later today if that generator is of interest.

 

[Nomadist]

I asked around and I don't think this system will work for me. I understand why it works for you but here are the drawbacks for my situation:

Drawbacks of All Battery/Inverter System​

• unless plugging into shore power is rare, this shortens the lifespan of the battery even when plugged in since lifespan is best thought of as contingent on "power throughput over the life of the battery." Interestingly, this is the same thing when measuring refined carbohydrates (flour, sugar, etc.) in humans, too; the more refined carbohydrates through the body over the lifespan, the more damage and therefore the lower the human lifespan or at least lower healthspan.
• there are several single points of failure: converter/charger, inverter, battery. If any of those fail, I lose access to AC power
• the currently spec'd inverter is not large enough to run my air conditioner whereas the air conditioner will always start from shore power; said another way, I would have to greatly increase the size of the inverter to be able to run the a/c when plugged into shore power thus raising the price

On the other hand, using shore power/generator through a relay permits unlimited use of high-power loads such as:

• the air conditioner
• electric heater
• microwave
• electric pressure cooker

without stressing any of the other components of the system.

My guess is that the reason this works for you and the others is because you are rarely attached to shore power/generator and using an air conditioner. I expect I will be doing this often in summer. And you're comfortable with the several single points of failure...I'd like to avoid those.

 

[Kevin D Pem]

we all have our ways. I do have A/C and plug it in to shore power when needed, however a generator is used for this more than the grid. I guess what I am saying is I have my cake and eat it too because I can have both systems working at one time. The cycle life of Lithium is roughly 4000 cycles. a cycle is calculated in a calculated full discharge. Keep that calculated in mind as there is no suggestion full discharge is in anyway acceptable.

I fully accept the 10 year life of the inverter, the expected 10 year life of the solar AGM batteries, and have extra MPPT controllers. The converter I use to maintain the 12v house battery via the inverter was new in 1983' I have spare parts for the inverter( after all I built it), but don't believe I will need them. My inverter board is 3000w but the transformer is 1500w 100% duty cycle, capable of 3000w intermittent. I too am concerned about long term life of system.

My suggestion is think outside the box. I spend my insanity that way?, but don't expect others to see it my way.

 

[Nomadist]

we all have our ways. I do have A/C and plug it in to shore power when needed, however a generator is used for this more than the grid. I guess what I am saying is I have my cake and eat it too because I can have both systems working at one time. The cycle life of Lithium is roughly 4000 cycles. a cycle is calculated in a calculated full discharge. Keep that calculated in mind as there is no suggestion full discharge is in anyway acceptable.

I fully accept the 10 year life of the inverter, the expected 10 year life of the solar AGM batteries, and have extra MPPT controllers. The converter I use to maintain the 12v house battery via the inverter was new in 1983' I have spare parts for the inverter( after all I built it), but don't believe I will need them. My inverter board is 3000w but the transformer is 1500w 100% duty cycle, capable of 3000w intermittent. I too am concerned about long term life of system.

My suggestion is think outside the box. I spend my insanity that way?, but don't expect others to see it my way.

Don't get me wrong: I do appreciate you raising this model to me because it had me think through things. I'm learning a lot through this process.

Regarding the battery life, the way it was explained to me is that the flow of electricity through the battery is what diminishes working life. We tend to think if it as cycles because that's how we use batteries but an additional way of measuring it would be, "how many amps have gone through the chemistry?" Additional diminishment occurs with every deep discharge, of course, as you point out.

But it wouldn't work nearly as well if we rated batteries as "10,000 total aH." People would immediately ask, "How many charge/discharge cycles does that work out to?" And cycle count includes the extra diminishment due to deep discharges.

And you are plugging the AC directly into shore power so even your model allows for that.

 

[Kevin D Pem]

a couple of questions:
if the voltage never goes down to chemistry storage voltage then what actually goes through the battery?

Where are you getting your data? (Website or???) will you share?