Trying to narrow down possible plans for my electrical system build for my camper van conversion. I've spent months reading and searching these forums and watching videos and have an okay baseline of understanding, but need some help figuring out where to go next.
Here are the requirements I'm working with for my build (some of this could possibly be altered if needed)
Requirements
Energy Needs
I used the energy audit spreadsheet and found that I need roughly around 5000 watt-hours of energy per day, with a peak of around 2500 watts max surge load if I avoid running multiple high watt devices at the same time (cooking mostly)
Charging
I want all of the following...
(Solar) Rooftop mounted solar panels - depending on the system config I could possibly at most get 600-900 watts of solar on the roof of my van
(Shore) Connect to standard 15amp household service (maybe 30 amp RV style, but not sure)
(Vehicle/Alternator) My van has dual high output alternators (though I'm still investigating safe continuous output) so I'd like to be able to charge my house batteries via alternator when driving (100-200 amps?)
System Options (all with lifepo4 batteries)
System 1 (12V 500-600ah?)
System 2 (24V 400-500ah?)
System 3 (????)
Questions
1) One of the main things I'm struggling to wrap my head around is how to go about using my vehicle/alternator as a charging source if I use a 24v system. I've watched Will's videos on this and other random recommendations and it sounds like it requires some extra steps to convert the 12v vehicle output and then charge the 24v battery bank. In some cases this can be accomplished with the design of the system, in other cases by using specific DC-DC chargers that will take 12V from the vehicle and output 24V to the battery bank. I've also seen some who have designed DC to AC to DC systems where an inverter is placed in the middle to work around this. But overall I'm not sure what path makes the most sense in terms of trying to go from 12V to 24V (as opposed to just keeping the house battery 12V for simplicity's sake). It seems like there are some limitations here if trying to push more than 100 amps into the battery pack from the vehicle based on the DC to DC offerings on the market currently, but again, I could be wrong.
2) For the house battery bank I've been looking at so many different possible configs with building my own pack. From an energy density standpoint it seems like most just use the 280ah cells as a starting point. So if I did this for a 12V system does it make more sense to build multiple 4s batteries, each with their own BMS, and then connect all of these batteries together in parallel to reach the desired ah capacity? This seems like it adds extra cost/complexity with all of those BMS for each pack. Or does it make more sense to try and build a larger pack of 8 cells instead to create a pack, then connect those packs together? I think I'm getting lost in the possible amount of configurations of cells if I build my own pack with the 280ah cells. The end result being either to achieve a 400-500ah 24v battery bank, or a 500-600ah 12v battery bank. It seems like building a 24v pack doubles my battery cost more or less, which makes it seem cost prohibitive, but maybe I'm missing something here. Also, I've seen many talk about issues keeping the cells balanced depending on the configuration for the pack.
3) The 12v or 24v question also comes down to the inverter. I've read enough to realize the amps are halved on the higher voltage 24v system, which saves on cabling costs and gets me more watts from a 24 volt system than a 12v system with the same inverter. I seem to be right at the threshold in terms of wattage for the inverter (2500-3000ish watts) when it comes to needing to step up from 12v to 24v, but again, I'm not exactly sure here.
4) In terms of the overall system I'd like if at all possible to try and buy most of the components (not the batteries) from one manufacturer (pending they make everything that is needed), and then use a monitoring system for the batteries and the whole electrical system. This step is somewhat cost dependent since I've got to work within a budget. Was originally thinking of using Victron for most components, but again, I could be barking up the wrong tree and it doesn't make sense to pursue the system as a whole like this. Maybe it's fine to just mix components across manufacturers instead of getting myself locked into trying to use all the same?
I think that mostly sums up where I'm at currently, trying to figure out which direction to take this whole thing, 12v or 24v given so many different considerations.
Super appreciate any help or guidance anyone is willing to offer. Thanks!
Here are the requirements I'm working with for my build (some of this could possibly be altered if needed)
Requirements
Energy Needs
I used the energy audit spreadsheet and found that I need roughly around 5000 watt-hours of energy per day, with a peak of around 2500 watts max surge load if I avoid running multiple high watt devices at the same time (cooking mostly)
Charging
I want all of the following...
(Solar) Rooftop mounted solar panels - depending on the system config I could possibly at most get 600-900 watts of solar on the roof of my van
(Shore) Connect to standard 15amp household service (maybe 30 amp RV style, but not sure)
(Vehicle/Alternator) My van has dual high output alternators (though I'm still investigating safe continuous output) so I'd like to be able to charge my house batteries via alternator when driving (100-200 amps?)
System Options (all with lifepo4 batteries)
System 1 (12V 500-600ah?)
System 2 (24V 400-500ah?)
System 3 (????)
Questions
1) One of the main things I'm struggling to wrap my head around is how to go about using my vehicle/alternator as a charging source if I use a 24v system. I've watched Will's videos on this and other random recommendations and it sounds like it requires some extra steps to convert the 12v vehicle output and then charge the 24v battery bank. In some cases this can be accomplished with the design of the system, in other cases by using specific DC-DC chargers that will take 12V from the vehicle and output 24V to the battery bank. I've also seen some who have designed DC to AC to DC systems where an inverter is placed in the middle to work around this. But overall I'm not sure what path makes the most sense in terms of trying to go from 12V to 24V (as opposed to just keeping the house battery 12V for simplicity's sake). It seems like there are some limitations here if trying to push more than 100 amps into the battery pack from the vehicle based on the DC to DC offerings on the market currently, but again, I could be wrong.
2) For the house battery bank I've been looking at so many different possible configs with building my own pack. From an energy density standpoint it seems like most just use the 280ah cells as a starting point. So if I did this for a 12V system does it make more sense to build multiple 4s batteries, each with their own BMS, and then connect all of these batteries together in parallel to reach the desired ah capacity? This seems like it adds extra cost/complexity with all of those BMS for each pack. Or does it make more sense to try and build a larger pack of 8 cells instead to create a pack, then connect those packs together? I think I'm getting lost in the possible amount of configurations of cells if I build my own pack with the 280ah cells. The end result being either to achieve a 400-500ah 24v battery bank, or a 500-600ah 12v battery bank. It seems like building a 24v pack doubles my battery cost more or less, which makes it seem cost prohibitive, but maybe I'm missing something here. Also, I've seen many talk about issues keeping the cells balanced depending on the configuration for the pack.
3) The 12v or 24v question also comes down to the inverter. I've read enough to realize the amps are halved on the higher voltage 24v system, which saves on cabling costs and gets me more watts from a 24 volt system than a 12v system with the same inverter. I seem to be right at the threshold in terms of wattage for the inverter (2500-3000ish watts) when it comes to needing to step up from 12v to 24v, but again, I'm not exactly sure here.
4) In terms of the overall system I'd like if at all possible to try and buy most of the components (not the batteries) from one manufacturer (pending they make everything that is needed), and then use a monitoring system for the batteries and the whole electrical system. This step is somewhat cost dependent since I've got to work within a budget. Was originally thinking of using Victron for most components, but again, I could be barking up the wrong tree and it doesn't make sense to pursue the system as a whole like this. Maybe it's fine to just mix components across manufacturers instead of getting myself locked into trying to use all the same?
I think that mostly sums up where I'm at currently, trying to figure out which direction to take this whole thing, 12v or 24v given so many different considerations.
Super appreciate any help or guidance anyone is willing to offer. Thanks!
