Why lithium ?

Google Mirror
1

With the goal of getting more people interested let me share why I am looking at lithium. If we don’t get a group of 25 to 30 interested the event would be cancelled.

On Aloki presently, I have two battery banks. Bank 1/starting battery is a single 105 amp hour firefly AGM. That bank is fine and won’t be replaced. Bank 2 / house bank is three Firefly AGM 105 Ahr or aprox 315 amp hour bank to draw on. This combination has worked very well for the last five or so years, but is starting to show its age. Time to either replace or upgrade. I thought about lithium in the past but discounted the idea because of the complexity and the less than sterling performance of earlier lithium type batteries. (did you know there are six types of lithium batteries - I didn’t.) Technology has definitely advanced the subject to where I think it is a viable and safe upgrade to my Nonsuch. A live aboard electrical engineer friend of mine has the system I’m projecting (with more lithium batteries) in use aboard his 55’ Amel over in the Mediterranean for two years now and is amazed at the performance.

So, after some research , I’ve concluded that Victron systems offers a reasonable and safe upgrade that offers a major improvement to Aloki’s house bank that would meet and exceed my needs. Victron batteries in particular have the highest safety record of ‘runaway battery’ issues. (basically, none) In speaking to my insurance carrier, ( you should as well) , adding Victron batteries to my boat will not void or alter my insurance coverage.

Basically, the start battery remains as an AGM battery. A Victron dc to dc charger is wired to that AGM battery which then charges the new lithium house battery bank. A monitoring device (standard or premium) is added as well as changing out a multiple selector battery switch. The battery charger remains the same but will only charge the AGM battery, not the lithium bank. That’s it. ( a bit simplified but accurate)

The goal on Aloki is less engine charging (the boat is on a mooring) and more service time for Refrigerator , heating, lights ,etc. On any diesel engine to electric motor conversion the lithium option makes a lot of sense. Couple Solar into the mix and one becomes quite self sufficient .

With my 100A alternator or 110VAC battery charger the charging cycle for lithium is reduced quite substantially. Longer battery life cycles, lower self discharge rates and weight reduction from three AGM / total 315 Ahrs @ 222 pounds to two LiPho /total 400 Ahr @ 90 pounds. Less weight and more amperage. There are quite a few other advantages but discussing them and your needs is the point of the event. Hope to see you at the workshop.regards, Gary /Aloki/Oyster Bay NY

1 Like
2

Gary,

Not sure if you’re monitoring Discourse and will see this, but if there’s a way to participate remotely, I’m definitely interested.

Victron has a strong reputation for their products.

As you pointed out, there are a number of different “Lithium - something” technologies out there now. Victron’s are LiFePO4 (Lithium Iron Phosphate, if I remember correctly.

BOAT/US, which is now a wholly-owned subsidiary (and, it feels, mouthpiece) of GEICO Insurance, went on record about the safety of the LiFePO4 technology in an article about Lithium three years ago. My insurance company, Merkel, has had no problems with my installation.

– Bob

1 Like
3

Gary,

Where does the engine alternator output go to?

Does the battery charger really go to the AGM starter battery and not the lithium bank. I understand that the side not connected to the existing charger gets charged through the DC-DC charger form the side that is connected to the battery charger.

Ward Woodruff
413-847-0620 cell

4

Hi Ward,
Your question was directed to Gary, but I’ll pipe in just the same because because I find it interesting to watch focus move from utility stuff ( like batteries ) to automation ( computer stuff ). I’ve been referring to this broadly as “power management”.

To operate safely, lithium batteries use BMS’s that protect the battery cells from a number of conditions that can damage the battery or be dangerous. BMS needs to act quickly and decisively to protect the battery, which sometimes means opening the circuit very quickly when the alternator may be running full tilt. An open circuit while operating at full load causes a voltage spike. There is lots of energy being produced in the coils of the alternator and the fields don’t collapse instantly so the wiring experiences a huge voltage spike. Lots of alternators got fried in the early days by BMS systems. The DC-DC charger is an elegant and inexpensive way to mitigate this risk. The starter battery can easily absorb the energy and avoid the voltage spike.

A secondary issue is that lithium batteries have comparatively low internal resistance they can draw more current ( charge faster ) than other batteries. Most 100 amp alternators are designed for continuous operation at 50 amps. This works well with AGM and other chemistries because they can absorb lots of power at the beginning of the charge cycle but the rate tails off dramatically as they charge (internal resistance increases). Some folks mitigate the risk of excess heat by adding thermal protection that reduces alternator output when it gets hot. Other manufacturers offer remote rectification which moves the rectifier ( AC-DC conversion ) outside the alternator reducing the heat generated inside the alternator.

An interesting aside about marine automation. The guy in the slip next to Soave this season has a brand new Axopar.

What a stark difference in technology… 1987 Nonsuch berthing next to a 2025 Axopar. At the start of the season, Mark’s outboard was refusing to lift all the way out of the water. Being a new boat the problem was covered under warranty, the service techs debugged the problem remotely and deployed a software update to fix the problem. Software… really ?

Pretty much everything on the Axopar is computer controlled… I have mixed feelings about that.

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

5

What’s wrong with this picture? I hate to see September go as much as anyone but can we go back in time? Be safe out there mates and hope to see you at the lithium presentation sometime in December.
Brian

image0.png
image0.png1376×1032 330 KB

6

Thanks Rob, that makes perfect sense.

I have the same Firefly battery, number and size as Gary.

I have two 100 amp alternators in parallel derated by an external regulator to 80 amps each. These alternators charge the house bank. The DC-DC charger charges the start battery from the house batteries.

When infrequently on shore power, the house batteries get charged by an inverter charger, 80amp charge capacity. The starter battery gets charged by a 40. amp charger that existed before the battery/inverter charger upgrade.

There is no 1-2-both switch. I believe it is impossible to accidentally discharge the starter battery with house loads as hooked up.

Ward Woodruff
N33 #8 Margery
Niantic Bay, CT

7

Brian,
This to will pass… we still have a few more weeks to enjoy autumn sailing. Lucky for you winter in the same marina as you sail from.

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

8

Ward Woodruffwwoodruff52@gmail.com
unread,
Sep 29, 2025, 2:03:05 PM (18 hours ago)

to INA-Nonsuch-Discussion-Group@googlegroups.com

Gary,
Hi Ward,
*** Disclaimer - I am not an expert on this subject. Please confirm anything said with a trainer professional. Well, basically it’s the purpose of this workshop - a trained professional will be the person to ask.

Where does the engine alternator output go to?
**** As I understand it, presently with AGM batteries , if you have a battery selector switch you can direct the alternator output to either /any battery bank you have installed. With the AGM/Lithium configuration the alternator output would go directly to the AGM battery using an “on/off” battery switch as to never mix Lead and lithium. Rob made some good points above.

Does the battery charger really go to the AGM starter battery and not the lithium bank.
*** yes. I would think it’s very unlikely that any battery charger has the capability to send two different charge instructions to two types of battery types.
I understand that the side not connected to the existing charger gets charged through the DC-DC charger form the side that is connected to the battery charger.
*** correct.

Ward Woodruff
413-847-0620 cell
*** Regards, Gary

9

I’ll chime-in here just to provide some ancillary information from my experience with LiFeP04 (AKA, Lithium Iron Phosphate) setup on Felix. A few things right off the bat:

– When “lithium” is discussed in house battery arrays, it means LiFePO4 – it is not referring to Lithium Ion like the batteries found in all consumer electronics and tools. Lithium Ion batteries are the (relatively) unsafe ones and one should think twice about their safety and purpose aboard a boat.

– When you compare AGM or other lead/acid batteries to LiFePO4 realize that a 100ah lead battery can provide only 50ah of usable capacity while a 100ah of LiFePo4 provides a full 100ah of usable capacity. So in my case, swapping 400ah of AGM (200ah of which were usable) to 300ah of LiFePO4 (300ah of which are usable) increased my usable capacity by 50% while downsizing the footprint and weight significantly. Not only that, but think of swapping out 200lbs of lead for 70 lbs of LiFePO4 and less than half the footprint! That’s huge for boats.

– LiFePO4 is a safe chemistry that is really very reluctant to have a runaway. Far less so than any lithium ion tools and gadgets you may have aboard, and far less so than AGM lead batteries about which I found out.

– LiFePO4 batteries cannot be charged below freezing! It will permanently brick them. Some have internal heaters to deal with that but it’s a consideration for you northerners in the east – not so much of an issue in the PNW. I think they’re safe at freezing if no charging is employed but check me on that.

– Generally, you do not want to have multiple LiFePO4 batteries in parallel – size up to the largest single battery that meets your ah needs. Unlike lead, individual LiFePO4 batteries have balancing algorithms for each cell that can get messed up by having multiple LiFePO4 batteries (and their associated BMS - battery management systems) in parallel. Recommended to only have multiples if a single cannot meet your total ah needs.

After an AGM house battery runaway that almost burned down my boat, I swapped out the 4) 100ah AGM house batts for a single 300ah LiFePO4, while keeping the lead starter batt for a hybrid array. Using the proper controller and retaining a some lead in a lead/LiFePo4 parallel array has many benefits over straight LiFePO4 banks and associated DC/DC chargers, and battery isolating switches, etc., and allowed me to keep all of my standard charging sources intact – Victron shore power charger, mppt solar array, and 80amp externally-regulated engine-driven alternator. I didn’t have to replace or modify any charge sources.

To do this, I use a device called a BankManager to manage charging and associated switching of the lead and LiFePO4. Essentially, the charging/discharging of the LiFePO4 occurs through the lead – the lead is a safe buffer. I won’t delve into all of the details of how it works and why I think it is the way to go – there are lots of videos on that. I can tell you it’s been entirely hassle-free, safe, reliable, inexpensive, and most importantly to me, charges the LiFePO4 correctly – something all of the dedicated LiFePO4 chargers are bad at.

– Using lead in a parallel lead/LiFePO4 array with the BankManager eliminates most of the problems faced when charging LiFePO4 – without that, I believe that there are considerations with alternators. I only know about that from reading as my setup protects against that. Regardless, I think an alternator needs to be externally regulated to address some of that risk.

Anyway, hope some of that is helpful!

I am not in any way affiliated with BankManager – I’m just a very satisfied user.

Eric Larsen

S/V Felix 1981 30C #115

Olympia, WA

1 Like
10

Hi Eric,
Absolutely, BankManager is an example of a power management tool.

I followed “Emily & Clark’s Adventure” for a while, and used one of their videos to guide me through diagnosis and resuscitation of Soave’s refrigerator.

Clark does a good job summarizing complex topics, and I highly recommend his videos as an intro for any of the many topics he covers.

In 2021 when Clark released BankManager it filled an important niche, for owners that wanted to leverage new battery chemistries, without investing in equipment designed for the battery.

It’s been a while since I thought about power management on Soave, I look forward to getting a refresher course in December. The various design tradeoffs get complicated.

Rob

s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

11

I guess nobody picked up on the anomaly in the picture that I sent. No one commented anyway have another look when you get time.

12

I guess nobody picked up on the anomaly in the picture that I sent. No one commented anyway have another look when you get time.
Brian

image0.png
image0.png1376×1032 330 KB

13

I just figured year-round gales were normal up there in the NE…

14

Brian

Good answer
Brian

15

Weather events starting before they finish… Errors from the National Weather Service … possibly forced by chaos due to upcoming government shutdown ?

This to will pass…

Rob
s/v SOAVE
NS33 #009
Cedar Point YC
Westport, CT

16

Gary and all

On the Boats US app under Small Craft Advisory on Sept 29 the left hand column repeated 4 times;

Begins Oct 1 at 12AM EDT
Ends Sept 30 at 6AM EDT

So we go back in time six hours or the small craft advisory lasts for a year less six hours.

Just sayin’
Brian

17

I looked over the Victron information on Li integration with lead acid battery, assuming that someone of lead acid is retained for a start battery. My eyes glazed over reading the instructions for the various parts needed for a Li battery. Four to 4 devices, fuses and a rats nest of wire.. Then I looked at the Bank Manager Eric mentioned. Seems like a very neat piece of kit, understandable and easy to install.

Causes a rethink of battery systems…

18

It really is a simple and elegant solution and very low cost comparatively.

With LiFePO4 batteries now commonly available to 400+ ah, it’s as DIY and simple as you can get.

Above that, split the ttl desired ah into two batteries and run an additional separate layout. But I’ve not experienced a need for that! 400 usable Ah is a lot of juice.

19

Here is an intersting overview of the state of it all.

20

BankManager looks like a great idea. Very easy compared to adding new DC to DC and AC chargers.

All I wanted to do was add one 100ah LiFePO4 battery but was stopped by the following warning/threat I received from my insurance company.

“Thank you for your inquiry about replacing your battery bank with lithium iron phosphate (Li-Ion) batteries. We can currently accommodate these with Aviva, but please note that this policy may change in the future. It’s crucial that the charging and monitoring system is specifically designed for Li-Ion technology and marine use. Additionally, the installation must be carried out by a professional to ensure safety and compliance with insurance requirements, and must be professionally maintained. Retaining receipt of professional installation is advised.”

Tom