Charging your Engine's Battery with your Solar Panels! 

Hm, I would suggest a device like the Votronic VCC 1212-30. A direct parallel connection could have a number of problems, especially when the cell types are so different and the wires so long. - If the starter battery is disconnected and one of the batteries is full while the other one is empty, it could be impossible to connect them again. The charging current would be so high that the fuse/protector would open (what is good). - If you start the inverter, there could be a very high current coming from the starter battery and going through the long wire and the shunt to the inverter. Again the fuse would open. - Same if you start the car engine. A high current could come from the lithium battery. - Lithium batteries and lead batteries have different end-of-charge/discharge voltages and also different charging curves. The integrated BMS in your lithium battery will only step-in when the absolute ratings are violated. It will not make sure that the long-term treatment is in a healthy way. (This problem may be there anyway because all your chargers are obviously designed for lead batteries, so you have to live with this. Hopefully you don't have a charger that tries to treat the battery with pulse loading and similar things that are done to increase service life of lead batteries.)

Nice. I don't have a van yet but have a solar system i am practicing on, on my balcony. solar panels, controller, agm marine battery. I was thinking of getting a 140 amp keyline isolator, that many ducati owners use (i have not yet ordered my 2022 promaster). It comes with a 180 amp alternator, i was thinking of getting the upgraded 220. Apparently these are not smart alternators. The fridge i have on order has its own battery so i am less worried about power shutoff for it, and am only going to be doing weekends at the start. You mentioned your alternator is a smart one. Are N. American ones not the smart ones? My other question is I have an intelligent charger for my car battery, 2/6/12 amp, it senses and then adjusts the charge. it has alligator clips. I was thinking of having a plug on the driver's side that is just basically a sealed 110v extension cord. I was thinking i could plug my charger into that, which would be shore power. So where would i clip the alligator clips of the charger onto? Still directly on the (house) battery terminals? Or bus bar? or where? At the start my solar is not too big, nor is the controller. I expect a 2-3 hour drive each way would top up my battery for the weekend and i could get a second battery. And we get overcast days. the solar would help keep a charge until i upgrade the solar system. I see you are not a fan of the isolators but it seems like a good solution to me, and i think it provides more than 2 amps. Thanks! Love your vids. What is your engine now providing with a 180 amp alternator when driving? 9 amps? or was that your solar?