No question if it was my boat. Solar plus LiPo is the way to go.
1. We are liveaboards so our demand is constant and lead acid batteries don't last, even the best AGMs.
2. We are in a suitable sunny environment
and solar does 90% of our requirements.
We have a 420 with 850 W (increasing to 1000W) of solar panels
and 800AH Lithium house batteries. Usable AH is 600 before automatic protection system isolates the batteries. This will handle some days of inclement weather
in winter but our backup is a Honda
2KVA portable genset and/or the engine
Although you gave good charging
with your alternators, this is only really useful when you are motoring. We are cruisers and we spend lots of time at anchor
so the motors may not be used for days or weeks. You don't really want to run your diesels at idle just to generate power. Also check the alternator
output, it should be suitable for lithiums but it best to make sure.
Advantages of lithium:
1. No voltage drop. We are constant at 13.4V approx even under high load.
2. More usable AH. With lead acid you can't use more than 50% of rated capacity, and to get useful life really shouldn't go below about 70%.
3. High current
drain. With lithiums we can run appliances
such as toaster, hair dryer etc., via the inverter
without voltage drop or damage to the batteries
4. Long life. Lithiums are rated in cycles and ours are rated at 3000 cycles or more. Assuming a cycle is a day (liveaboard) we expect 10 years plus. We have been getting a loss of capacity with AGM
after 2.5 years.
5. Lifestyle. No more worrying about the #*^+! batteries.
6. High recharge rate. Can accept as much as you can pump in right up to about 98% capacity. Lead acids reduce the charging
when they near full charge and take a long time to obtain full charge.
7. 21 st century vs 19th century technology.
8. Much lighter weight.
1. High capital cost. Offset by long life so the nett per annum cost is about the same over 10 years by my estimation.
2. Need suitable charging devices. In my case I had to upgrade the OEM Christec charger
that came with the boat. Newer boats such as 421 probably have the later chargers with more pin settings including a lithium suitable program. Suggest you check.
I'd suggest if you are buying
a new boat:
1. Check the price
of factory solar. Solar is CHEAP! Chances are you will pay too much for the factory option. But although panels
, don't forget about installation
costs which can be messy after market. Get a price
to supply and install after purchase
2. 1000AH solar. The more the merrier. Panels
3. Good solar charger
with a lithium program. Not a problem but check before you buy.
4. Check the factory installed charger has a lithium program
5. Use lead acid for the engines. Low use, cheap will do, replace regularly.
6. Good inverter
7. Find a reputable lithium supplier who understands the technology. Most don't!
8. Pay the money
and buy quality. Cheap lithiums can be risky.
My experience is its always best to go direct to the final solution. You will eventually go lithiums, unless you are only using the boat occasionally, so it's better to do it right first time. Upgrading later always is more costly in my (unfortunate) experience.
CASABLANCA L420 #86