We just completed an upgrade from a 1200ah Mastervolt AGM
bank to 1200ah Mastervolt Lithium
While still at the service dock
I shut off shore power
and allowed the new house battery
bank to discharge to 50% SOC over 3 days, then turned on shore power
and it took 3 hours to charge to 100%. I was ecstatic.
We have 200 amps of charging
capacity and charging
amperage was 196 for the first hour to 70%, then 168 for the second hour to 90%, and in the final hour dropped from 145 to float.
After cruising for 3 years living on the hook full time with AGMs that took forever to charge and required running the generator
2-3 times longer than I think is necessary, this was astounding and worth the investment for me.
It took 7-8 hours to charge my AGMs to 100% and routinely it took 2-3 hours in float to go from 97% to 100%. Charging amperage in bulk mode always started at 190 then quickly dropped to 145 and rarely stayed there for more then 30 minutes before dropping to 90 and below. Awful and frustrating.
In normal use I would run the generator
for 3 hours or so to get the AGMs to 95% or so then shut off, but they need to be topped off to 100% at least once a week or their performance will degrade. We lost
2 of the original 6 batteries
because I was reluctant to do so.
We are excited about our new lithium batteries
which will serve our cruising lifestyle far more effectively than our previous AGMs
Our house battery bank of six 6v Mastervolt AGMs provided 1200ah at 12v, which is 600 usable ah (50%). Current
cost of this battery bank is @$4,300.00
Our new lithium battery bank of three Mastervolt 12v 400ah batteries also provide 1200ah, of which 960 is usable (80%). Current
cost of this battery bank is $18,000.00. We could have used just two of these batteries instead of three, but I wanted the higher capacity to go longer between charges.
We originally wanted lithium when refitting Grace for cruising 3 years ago but the cost was prohibitive. Since then the cost has come down, the tech is better, and our frustrating experiences cruising with AGMs has motivated us to upgrade. The actual cost over time for lithium is lower for cruisers like us who live on the hook.
- Usable ah-
can go longer between charges.
- DoD cycles-
Mastervolt AGMs are rated for minimum 2000 charging cycles, lithiums for minimum 3000 charging cycles, 33% longer life.
- Charging time-
As described above, it took 3 hours to charge the new lithiums from 50% to 100%, which would be 6-8 hours for the AGMs.
- Charging SOC-
Lithiums are fine, even prefer, not being charged to 100% so I can use the peak charge curve for 1-2 hours and stop wherever that is as often as I like. AGMs MUST be charged to 100% at least once a week or so to keep them functional. Not doing so for the first year of cruising lost
me 2 of the six batteries I started with.
- Solar/Wind generation-
AGMs HATE the variable charge levels of solar
generation and require charging to 100% once a week or their ability to accept a charge greatly degrades/diminishes. Lithiums are able to maximize the energy generated from our solar
This past winter I had to change generator oil
once per month or so (every 100 hours), a ridiculous amount of generator use. With the lithiums I should be able to get by with wind and solar most of the time and use the generator once or twice a week during the winter for a couple of hours- 12 hours per month vs. 100 hours per month is a BIG difference that figures into the cost and quality of life on the hook.
As a side benefit, lithiums are significantly lighter, so Grace's weight distribution problem from replacing a 110 gallon fuel tank
with a 90 gallon fuel tank
is fixed, no more 2 degree list when the tanks
In case you worry about safety
and fires with lithium batteries, that is an issue with going cheap
and not having the proper setup, which can be expensive. Most of what I needed was already in place from Grace's electrical refit
of an integrated Mastervolt system, and the battery monitoring and management systems have double and triple redundancies. Lithium is a waste for dock
queens, but we are on our boat
100% of the time and pay close attention to all of Grace's systems, so if there's a problem we will know it almost immediately.
Fun fact- we like to use an AC popcorn air popper every evening while watching TV and with the AGMs we would run the generator for 5 minutes to do so (if not charging). With our new lithiums we can do so from battery power without the generator. That one little change is a great metaphor for the difference these batteries will make for us.
We are happy and excited about our new lithium batteries! Our first week was nirvana and we have high hopes that their initial performance will continue.