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