I had the same problem and replaced my 2 60Ah Victron gel batteries with a 100Ah lithium LifePo4 battery. I have a Fleet with diesel heater, cooler, light and som charging is the main power consumption. I also have a 275W solar panel, but not much effect where I live at this time of the year. Lithium battery works much better for me, camped this week and it was around 0F. I have a battery with internal heat and Bluetooth and find that essential. The BMS automatically stops charging when the battery is to cold and starts the internal heat until the temp limit is reached. The Bluetooth gives a good overview regarding the status of the battery (power left, current power consumption, voltage, number of cycles, charging) which makes it possible to plan and manage before you run out of power. One of the many benefits with a lithium battery is the rapid charging. I run a 30A Victron DC/DC which gives me 30Ah in one hour. So if I am running out of power I start the truck and charge the battery as much as required. On this week hunting trip for 2 nights I used around 50 Ah a day. It was cold and relatively short days when it comes to daylight so the heater was running for 16 hours a day which is around 30Ah. Then the cooler, light, charging of phone/tablet is around 15-20. It was clear weather and sunny, but it only produced 13Ah the first day and 15Ah day 2. The BMS/Bluetooth gave me full control of the situation, so I managed w/o running the truck. I have experienced the diesel heater stopped working due to not burning clean and soothing with my led batteries. When the voltage drops to low the fan slows down but the pump delivers the same amount of fuel. Leads to the wrong fuel/air mix, soot and shut down. Lithium batteries holds the voltage much better and will deliver good voltage all the way down to the BMS shut down when it is 5-10% left.