Good job on that link, appreciate the effort.

I tried to limit my comments to context on this thread and my own use case.

Your proposed set up on the linked thread is a split yellow top system where the AH is shared across main and starter. Same as you proposed here. Its a well thought out system that fits a lot of use cases. I'm not knocking it.

But like the OP, I chose to have a dedicated starter in reserve and a 100ah aux used in isolation when in camp. But even so, this kind of set up does not need a DCDC. A simple relay could cover it.

To sumise my reasoning and experience with the ctek250:

I went with DCDC because at the time I was not happy with my aux battery SOC on direct alternator. I also had a battery failure from overcharging. So I gave the DCDC a shot.

At time of install I did have concerns about limited charge rate not covering my needs and reliability.

Years have now passed, and if I had to start over on the TDI battery bay today I would go again and get another DCDC with selective lead acid and lithium charge maps. I now know for sure that 20amps of dedicated bulk charge on a 100ah battery is enough to replenish my usage on that vehicle. And I have had zero faults on the unit even though it has been submerged in rivers and vibrated through dusty hell back. I can have mix and match batteries and my aux is very happy with the dcdc charge map.

The new ctek 250 has a charge map for lifepo4 and much improved solar mppt algorithm. So I would give it another look.


Now there are the 100ah lifepo4 batteries that are starting to drop to around the $500 mark - I think DCDC set ups will become more common .