Battery banks

[Nidnoi_V]

ll batteries are based on LiFePO4

I¨m seeking your Advise; I’m about to convert a Catamaran to an Electric /Hybrid. With this setup, I will be able to use my motor between 4-5 hours depending on Sea stake, etc. or pure electric, which means I can save roughly 20 Liters or 17 KG per usage or per day

However, I will also have things running on 12/24, which my Idea is to make a Secondary battery bank on 24V, running fan, light, navigation, etc.
For A/C appliance and propulsion, I would have 28Kwh at 48V DC

1. Solution 1

3 Battery banks

a. 48V Battery bank running with 600 AMP or 28. KWh weight 250KG
b. 48V Battery bank running with 600 AMP or 28. KWh weight 250KG
c. 24V Battery bank running with 1200 AMP or 14.2 KWh weight 165KG
Total Weight 665 KG

2. Solution 2

2 Battery banks

a. 48V Battery bank running with 750 AMP or 35.5 KWh weight 312,5KG
b. 48V Battery bank running with 750 AMP or 35.5 KWh weight 312,5KG
Total Weight 625 KG

I¨m aware I will need DC/DC converters from either 48 to 24/12v or 24/12V
My concern is here how much AMP hours will I lose when downgrading to 24/12 V
For Charging the batteries, the following installation is made 2800 watt Solar power plus also regen from the Electric Engines when sailing for sail

 

[snoobler]

The DC converters aren't particularly lossy. Better than AC to DC. You could probably count on 90% efficiency.

A 120W load will take 10A @ 12V, but the converter will only pull about 5A from a 24V source or 2.5A from a 48V source.

Option two appeals to me with 48/24V and 48/12V converters as needed.