For the 240V system I have decided to use Victron hardware. These products seem to be amongst the most advanced on the market. I had bad experience with Xantrex (Schneider) several times and an unresponsive support. I have a few chargers and an inverter from Xantrex. They work ok as long as you keep them dry. A bit salty air and they spit the dummy. My outback 60A solar charger, which I have in the slide-on camper still runs strong and I would regret dumping it, but it simply is not up to the task of charging the Lithiums with maximum available power.
I have calculated our power consumption on a hot day and a cold day and looked at worst case scenarios. We would like to keep the generator at home and save the 54kg for the Honda 30is, which we have since years for the house when we have power outages and need to keep a minimum running.
Adding a little safety margin to the average consumption and we get to around 5 – 5.5 KW peak usage and a total of around 12-13KWh a day worst case. With a usable solar capacity of around 2.0KW , we should be ok with 5-6 hours of full charge. First of all it is not realistic to expect 5 or 6 hours full charge, with shaded areas and/or higher temperatures and secondly this is worst case, on average we should use less. With the total of 2.7KW panels I have compensated for temperature, shade and conversion losses (the chargers can handle full 1200W each) but if I really get to the limits of the chargers I can disconnect 2 pairs of panels on each strand to keep the overall input power below the charger limits. I will have to wait and see how the panels perform and if I really need to disconnect at times. There is not much more to do, because the roof space is fully utilised and the solar chargers are at their max with the largest Victron 150/85 times two.
The Victron devices have many nice features and one them is that the solar charge controllers and the inverter/chargers can run in parallel. One can connect 2 solar chargers to the same bank and they will communicate via a connection cable. Since the Lithium batteries can take a much higher charge than the solar controllers can deliver it is safe to run them both into one battery bank when really needed under certain circumstances.
The inverter/chargers can do the same thing, produce double the output of 230V when running in parallel (2x3000W = 6KW) and also 2 x 120A charge current when running in parallel. Victron confirmed to me that I can run both chargers and the solar controllers in parallel into the same bank and might be able to achieve a charge current of 400A. This is still below the rating of my contactor (500A), which is controlled by the BMS to switch off charge or load when cell voltage leaves healthy ranges. This will be a rare situation, but it can happen, because one of the battery banks is on the truck and the other is on the van. If we leave for a few days with the truck this bank will not get much charge other than 50A from my Sterling DC-DC charger in the truck. If I use my radios heavily while away, the battery will loose charge quite a bit. On return to the van the other bank is most likely fully charged, so all available capacity (solar + AC shore power over 2 x 15A leads) can be utilised to charge the low bank as quick as possible. In the mean time both inverters in the van can draw from the full battery if needed.
Another feature of the Victron Multiplus is that if the demand of AC is higher than the available AC input then it will automatically draw from the battery. For example, if we are by any chance in a caravan park (will probably not happen too often) we might only have one power point available with one lead. Now 15A will not go far when we use our cook top and air con and espresso machine and microwave at the same time. The supply will not handle that, but the two Multiplus running in parallel will with parts of the power coming from AC and the rest from battery.
One other reason I have dimensioned the system as it is, is the consideration of discharge current. Although the Lithiums can deliver huge currents and can discharge to 20% and lower (with constraints) my thoughts about best practice is to choose a battery capacity that the max discharge current is no more than 0.5C, meaning with 700Ah batteries I can use 350A and have 0.5C discharge current. Also, anything above 400A (fuses, cables, contactors etc) becomes really big and more expensive.
One other feature of the Victron inverter is a UPS function. If shore power drops it will automatically switch to battery in a blink that output is uninterrupted. This is a nice feature, but will probably not be needed too often since we will be free camping most of the time without shore power, most likely also without generator.
The system was designed with redundancy in mind and the fact that one bank resides on the truck and not the van, otherwise a 24V system would have looked more logical. I would have saved one solar charger ($800) and the 5KW inverter would have been a little cheaper than the two 3KW inverters, but if something goes south then we have nothing. Since I decided against gas, we only have diesel for heating, we depend on electricity, so redundancy was of some importance.