Defender second battery location
It’s the very system used in a large majority of vehicles running AGMs.
None are suffering what you’re claiming.
Also, cycling the main battery to 50% SOC is a good thing, cycling batteries is a good thing.
Don’t listen to us though, Drivesafes only been doing this for decades and I only worked on Military electronics and electrical systems - what would we know [emoji41]
Defender second battery location
Er whoops, I thought Rexy already had the DC-DC.
If it was me this is what I’d do on a dirty of tdi
- upgrade alternator to a 100amp/hr disco, I did mine when the OEM one failed, if you have the coin that upgrade sooner
- two batteries will fit but I relocated the AUX that previous owner fitted under the passenger seat to the cargo area. A normal size battery won’t fit under the drivers without serious mods
- fit a redarc battery isolator either the basic or the one that allows back charge from solar to dart battery
- fit Victron regulator
- fit Anderson plug somewhere convenient to plug solar into.
- run cable from fridge to load side of regulator
- fit fuse box if want more circuits.
Oh two batteries under the seat doesn’t leave a lot of room for much else....so to answer your main question, it’d be tight adding a c-Tek in there as well and be a pain when you need to work on the system.
The above set up seems to work well for me, give me the capacity I require, leaves the starter alone, seem to get good life out of batteries...although I do swap them out st three years regardless.