Nanni diesel hybrid propulsion.

"What is now the state of the art in batteries in gravimetric energy density [Wh/kg]? Especially the Price/Kg?"

For std lead acid batts about 10% better than 1890.

Good shopping can find golf carts at about a buck a pound , that will deliver an amp a pound , long term.

Aint progress grand?

FF

 

this is close to best battery consumers can buy

http://elitepowersolutions.com/products/product_info.php?cPath=40&products_id=149


• GBS 3rd Generation Li-ion Batteries Product Specifications:

- Nominal Voltage: 12.8V (4X 3.2 V)
- Nominal Capacity: 200 Ah
- LiFeMnPO4 chemistry
- Operation Voltage Range: 11.2 to 14.4V
- Weight: 24.9 kg or 55.0 lbs
- Dimension: 500X259X142 mm or 19.25 X 10.2 X 5.5 in
- Max Charging Current: 3C
- Max Discharge Current: 3C (continuous) / 10C (pulsed)
- Cycle Life : >1500 (80%DOD)
- Operating Temperature: -20 to 65 C or -4 to 149 F
- Self Discharge Rate: <3% monthly
- Accessories included: jumpers, bolts or rivets, washers, split washers and cell covers

12.5V*200Ah=2500Wh=2.5kWh nominal, 25kg, 1500$

so that's 10kg/kwh. And 600$/kwh

I think those are lithium manganese so safe in a boat. If they are true lipos then a bad idea. LiFePO is slightly worse in terms of weight price close to same.