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Richard Nye

9/4/2025 7:31 AM

We're full time cruising, so doing a major retrofit on the boat is like changing the tire while driving down the freeway. What I did was install a Battery Bank Manager System (link: https://marinedcac.com/pages/bankmanager?srsltid=AfmBOoptkntMpnBYeiiiMpJ55lnWb0Dfnfjd5u5pKlvLThjSRF_hIoG7) and left some AGM batteries in the house bank. That allowed me to add significant lithium battery capacity to the house bank, but without the need to change the charger, inverter, alternator, etc. I know, people will say that you shouldn't combine AGM with lithium. But this device does it safely IMO. There are a lot of videos online explaining how it works.

My house bank was 6 AGM 4D 220Ahr Lifeline batteries. I replaced 4 of the AGM batteries with 4 Epoch 460Ahr 12V batteries to get 920Ah at 24V. I was able to go from 330 Ahr @ 24V usable (220Ahr/12V battery x 6 batteries / 2 to convert to 24V X 50% usable = 330 Ahr @24V) to 938 Ahr (460Ahr/12V LiFePO x 4 batteries / 2 to convert to 24V * 90% usable + 220Ahr/12V AGM battery x 2 batteries / 2 to convert to 24V X 50% usable = 938 Ahr @ 24V). That's almost a 3X increase in battery capacity in the same space without a lot of modification. It took me about a week to install.

I am having a few minor nagging issues with the Battery Bank Manager, so I can't go all in on an endorsement. But it does work and it has allowed me to get the benefits of lithium and almost 3X my house bank capacity without changing anything else.

Since I purchased the BBMS Clark has gone through a divorce and had medical problems, so support is spotty. I would do the same again, but if I had a "port" to lay up in for a long time I would probably change the charging equipment.

Lucky Chucky

9/4/2025 2:51 AM

Mark,

A blog post sounds great. May I suggest a grid section breaking down the elements, manufactures, ratings, price points, etc...Big Jack, Richard, Jerry, and others with serious experience in this subject will be gold!!!

Richard, I took note of your comment about less charging time on the genset and the savings involved with keen interest cuz when I'm on the hook, I'm running genset 3-4 hours a day (even with solar). Thanks buddy!

My electrical guru in Panama told me that his cost analysis of switching to Lithium was it may cost double the price of AGM but lithium last 3 times longer (plus save space, weight, etc), but I don't recall if he factored in all the costs of other parts upgrades such as invertor, chargers and whatnot into his analysis?

Mark Tilden

9/3/2025 6:15 PM

Hey Lucky:

Yep....it's not a trivial undertaking. Fortunately, I've been moving in this direction for quite a while, so, for example, when we switched the inverter/chargers, one of the criteria was units that could handle Lithium Batteries. We've also handled the charging of the main engine start battery, which will remain AGM (we only have one big alternator).

I'll definitely let people know how it goes. Maybe a series of blog posts???

Mark

Lucky Chucky

9/3/2025 11:13 AM

Dear Mark,

I've followed your threads for years about converting from AGM to Lithium and have always run up against the issue of conversion of all my elements: alternator, regulator, invertor, battery chargers, batteries, etc...

...but I've shied away from such a big switch, especially while in transit from continent to continent...

We replace 14 AGMS in 2024 and looking to 2029 to make the switch to Lithium and will monitor your experience...good, bad, and indifferent.

Salute.

~Lucky Chucky

Mark Tilden

9/2/2025 2:06 PM

Richard:

Thanks for the added data point. We are different in a few ways:

1. We are not "power conservative" as you are. My wife LOVES refrigeration. :-) We have a total of five refrigerators/freezers on board:

(a) Two dual-drawer fridges in the galley/saloon (the primary refrigerators. She really likes these over the traditional door refrigerators and she has a huge pantry where the upper 2/3 of the big door refrigerator would have been.

(b) The dedicated icemaker under the pilothouse settee

(d) A small drink refrigerator on the flybridge

(e) And because we were still carrying a cooler in the cockpit, I put a 24V "icebox conversion kit" in the insulated icebox/locker under the settee in the pilothouse.

All that to say, I don't think our DC power draw is ever as low as 15 amps. :-)

2. We have two 5KW Victron inverters. We seldom, if ever, get close to using all the inverter capacity, but they are setup so that they can provide 240V across both inverters or 120V from just one and all the 120V loads are easily switched from one or the other so we have good redundancy if one fails.

3. I have 2400 watts of solar (six 400 watt panels on the hardtop and pilothouse roof), but we don't get anywhere near as much consistent sun as you do. They still make a big difference and I wouldn't be running my gen nearly as much if my batteries were even marginally healthy.

I do look forward to making MUCH less use (but more efficient use) of my big 25KW generator (which powers my hydraulic get home). Even with the AGMs today, I can charge at 300+ amps--but, as you observed, only for a brief time. I look forward to being able to both charge the batteries more quickly and efficiently with Lithium AND keep my big gen happier by loading it more.

Mark

Richard Nye

9/2/2025 1:36 PM

Regarding generator use and lithium batteries. I installed lithium batteries last summer. While comparing my trip to the Bahamas in 2024 with AGM vs 2025 with lithium, I found I used my generator only ONE THIRD(!) of the time after the lithium install. I attribute that to faster charging with the lithium (same charger, but AGMs charge so much slower during absorption and float), and that lithium batteries are more efficient and have less loss. I usually run my generator for 1-2 hours every other day. That's a savings in fuel and increases my range. Less generator maintenance also. I only have a 2500W inverter, so no big loads on the batteries. My average use is about 15A @ 24V, and I have 1400W of solar.

Richard

Untethered

Mark Tilden

9/2/2025 11:50 AM

Hey Mike:

Mark Tilden, Enjoyed your recap of Alaska on the SOA Blog. I found the stats especially interesting. I'm curious about your generator time comment. On a multi-day anchorage, about how many hours did you run the generator on those days between arrival and departure?

Thank you!

I didn't keep an accurate daily log of generator run time, but I would estimate that it averaged about 3.5 hours/day. Less on the sunny days. Maybe a little more on the cloudy/rainy days. My house batteries are at a stage where they will only discharge to about 75% state of charge before the terminal voltage starts to fall off rapidly, so I'm really only getting about 20% of the capacity (from 95% to 75%). They definitely need to be replaced.

And....I hope you take us through your decision process in deciding what batteries you choose.

THe final decision is yet to be determined, but my starting position is to use the Victron NG batteries. I can put six 300AH 24V batteries in place of my 24 2-volt cell batteries and get about 1400 useable amp-hours on the NG batteries (that is based on discharging them to a 20% state of charge) vs. 800 amp hours (at best--more realistically about 650 AH since I try not to go below 60% on the AGMs). So, with fewer, lighter batteries I will more than double my usable capacity.

Why the Victron batteries? Because I value the clean integration with their charging systems and I am impressed with their quality and support. I like the intelligent per-cell monitoring built in.

I have already replaced my two Mastervolt inverter/chargers with Victron Quatro Inverter/chargers, and I plan to replace my two Mastervolt Mass/100 house chargers with Victron Sklla-i chargers (I'll have two perfectly functional Mastevolt 100-amp chargers for sale this fall!)

I'll keep you posted as I get closer to actually pulling the trigger on the battery swap. Now all I need to find is some young strong backs for hire to help me get 24 CL800 batteries out of the master bilge. :-)

Mark

Mike Cero
M/V Sea Rose (6605)
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Mike Cero

9/2/2025 10:50 AM

Mark Tilden, Enjoyed your recap of Alaska on the SOA Blog. I found the stats especially interesting. I'm curious about your generator time comment. On a multi-day anchorage, about how many hours did you run the generator on those days between arrival and departure?

And....I hope you take us through your decision process in deciding what batteries you choose.

Mike Cero

M/V Sea Rose (6605)

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