High-level request for advice and opinions on changing over from AGM
I have been reading the massive Lithium thread, but at nearly 300 pages after hours and hours I still feel like I would like the help of a crisper summary of Lithium applied in the cruising environment
Here is my simple summary understanding:
Here is the power system I have now:
- Lithium is much more expensive upfront, but might be competitive if you factor in lifecycle.
- Lithium can use 80% of the Ah in the batteries vs 50% for lead
- Lithium charges linearly instead of asymptotically
- Lithium is much lighter
- Lithium can be packaged in drop-in battery formats (e.g. SmartBattery and StarkPower)
- House bank: (5) Lifeline AGM 210Ah batteries= 1050 Ah nominal (1-year old, but boat just came out of charter)
- (2) 250W Kyocera Solar Panels
- 5kW Onan Genset
- A Lagoon 450 with 5 people living full-time as a family cruising (tropics)
- 2 small fridge/freezers that are drawing about 10 amps 24/7
- Fans, lights and water pump that are no big deal
- Every morning we are down to 12.0-12.3 v from just the fridges and lights (no DC powered inverters in use)
- Every morning we run the generator for 2-4 hours depending on how much water/laundry/ice we need making, and charge the laptops/phones/toys during this time
- During the day, the solar will often keep the house up past 12.7v and sometimes even go over 13v.
- But by late afternoon we are often back to 12.2v, again no inverters, no water making under DC, music rarely played. Lights, fans and the 2 small side-opening fridges
- So we run the generator again, do more water/ice/laundry if we need it.
It seems to me that we are running the generator too much no?
With the nominal 1050 Ah house bank, we should have 500 Ah right? And all-in the lights/fans/water-pump and fridges show 11-13 amps on the battery monitor
. Call it 13A x 12 hours = only 150 Ah of usage, but why does the house get down to 12.0-12.2 by the morning with that size bank? Yes, when I turn off the fridges it will jump back to 12.6. So does that mean that I have misunderstood how to manage my batteries? Do I charge when it is at 12.2v under the load at the given moment, or do I have to keep turning off all the loads and then check what is the voltage on the house and if is > 12.2 w/o load it is still good? <<< This is a key question.
Going forward with the assumption that I am only getting about 150Ah out of these batteries, I am thinking of Lithium.
Is it as simple as StarkPower suggests? I buy 7 of the 125Ah (750Ah) deep cycle batteries that weigh just 240# vs #670 for the current
set of AGMs. They cost $1440 each or $10k. I pull the AGMs out, pop the Starks in and save 430# of weight. And now I only have to run the generator about 1/4-1/3rd as much?
Now, the 750 Ah bank would get fully charged with the 5kW genset in what roughly 1.5 hours? And it would much more efficiently suck up the solar during the day right? And presumably stay fully charged so we would no longer need the evening genset cycle. Unless we wanted to run the AC appliances
Then, jumping the shark, if I were to add an arch on the back of the 450, and extend towards the aft a row of additional solar panels
, I think I could comfortably carry 6 more, to have a nominal 2kW system. That seems like it would be enough to start indulging in some inverter
use, and keep several 85W macs plugged in, and perhaps judiciously use the water or laundry
or ice maker? And perhaps getaway with not needing to run the genset at all on normal sunny days?????
Please if you have the patience to give me links to [better] existing threads or sources. But at the highest-level, aside from the money
involved, can I run the boat off of just solar with a Lithium house bank? <<< This is what I really want to know - how awesome can I make the boat from a power point of view (setting aside upfront costs). How realistic of expectations can I indulge in?
Many thanks in advance for any and all help,