It seems to me a lot of the discussion/conventional wisdom of "24/48 volt systems will always be cheaper/more efficient compared with 12 volt systems" is in the context of stationary systems, cabins, homes, etc. And that for us mobile folks (land based, marine is a different story), the equation is a bit different.
Here are a few of the reasons I see the equation being different for (small to medium) mobile systems:
I'm not arguing that 24v doesn't make sense for mobile applications, I think in many cases it probably does, but I think there are more tradeoffs and factors to consider for those of us with mobile setups. I am admittedly just beginning to wrap my head around PV, battery storage, etc, so there is probably a lot I am missing, or misunderstanding. That is sort of what this post is about. I'm 'thinking out loud' and hoping to instigate a productive conversation on the topic, and hopefully learn a thing or two. Other than wiring and charge controller wattage, what other benefits and efficiencies does 24vdc bring to the table. Tell me where my thinking is wrong (or right)?
Here are a few of the reasons I see the equation being different for (small to medium) mobile systems:
- We don't just feed everything through an inverter and wire everything in 110. So the voltage we choose isn't just a 'storage voltage' its ideally the voltage we will be using for most of our wiring, so it follows that the voltage we use will have a larger effect on the system and the appliances/electronics/products available to us.
- We generally are talking about smaller spaces ~40-300 square feet at most. So the cost of wiring should be a smaller part of our budget than with a larger stationary 'whole house system.' Or maybe I am thinking about this point backwards, maybe the wiring cost is greater for mobile systems since more of our wiring is lower voltage higher amperage wiring when compared with wiring in 110?
- We are also talking about smaller square footage available for PV so in contrast to stationary setups where space is often plentiful and big panels are cheap, the charge control is somewhat less likely to be the bottleneck in our system (one of the major reasons to consider 24vdc).
- For many of us, mobile power requirements/draws will be much much lower than the draws required for all the creature comforts of a house. So like point 2 this should in theory reduce the cost of wiring as % of total system cost by allowing the use of smaller gauge wire.
- 12 volt appliances appear to be much more plentiful (especially used) and often substantially cheaper than 24 volt alternatives. You could easily use a dc-dc converter, but there is a conversion loss of 4-6% iirc (?) when converting 24vdc to 12vdc, not major but also not ideal.
I'm not arguing that 24v doesn't make sense for mobile applications, I think in many cases it probably does, but I think there are more tradeoffs and factors to consider for those of us with mobile setups. I am admittedly just beginning to wrap my head around PV, battery storage, etc, so there is probably a lot I am missing, or misunderstanding. That is sort of what this post is about. I'm 'thinking out loud' and hoping to instigate a productive conversation on the topic, and hopefully learn a thing or two. Other than wiring and charge controller wattage, what other benefits and efficiencies does 24vdc bring to the table. Tell me where my thinking is wrong (or right)?