Help needed with electrical setup for overlanding

Question

I am converting my 2011 Nissan Frontier Pro-4x to an overland-ready setup. For this, I want to set up a separate electrical system to power certain items. I need some help calculating the requirements and consumption for my system.
Here is what I have planned so far for a dual-battery power supply setup:

Stock alternator to charge both batteries, 130 amps
12v Deep cycle battery, need to know the right aH requirement for my setup
Battery isolator
Inverter (probably a 300w inverter)

And here are the power consumers I have planned:

Laptop MacBook Pro, connected to an inverter. Needs around 60 watts per hour per average (95w max). Needed for 8 hours per day
4g modem & Antenna (Peplink Pepwave Max Transit Mini), connected to 12v DC. Needs 12 watts per hour. Needed 8 hours per day
Diesel Heater 12v DC, needs 72 watts per hour (only needed occasionally at night, in very cold weather)
Fridge, 12v DC, needs ~35Ah/day, runs all day

I'd expect the second battery to be fully charged by the alternator every 2 days at the worst.
I need help calculating the total aH requirements that I have, especially with the inverter it becomes a bit confusing.
Thank you!

mitchkman · Answer

Here is my calculation that I came up with (please check if this and my conclusion makes sense):
+---------------+-------------------+---------+------+--------------------------+------------------+
|               | (Average) Wattage | Voltage | Amps | Hours used on a cold day | aH usage per day |
+---------------+-------------------+---------+------+--------------------------+------------------+
| Laptop        |                60 |      12 |    5 |                        8 |               40 |
| Modem         |                12 |      12 |    1 |                       12 |               12 |
| Diesel Heater |                72 |      12 |    6 |                       10 |               60 |
| Fridge        |              27.6 |      12 |  2.3 |                       24 |             55.2 |
|               |                   |         |      |                          |                  |
| Totals        |             171.6 |         | 14.3 |                          |            167.2 |
+---------------+-------------------+---------+------+--------------------------+------------------+

My conclusion is that at the very least a 200aH deep cycle battery is required to keep everything running for a day with the above usage pattern.
However, this would drain my battery well below 50% which would decrease the life span of the battery significantly.
I am thinking of  getting 3x100aH batteries and connect them in parallel. Additionally, I worry a bit that my 130amp alternator might take a long time to charge the batteries up again.
I'm thinking of getting a solar panel to help keep those batteries charged. I'd also get a DC/DC charger to make sure the batterie(s) receive the correct voltage to charge up to 100%.

Help needed with electrical setup for overlanding

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