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Learning so much
here. Thanks! How does the BMS disconnect only the load side?
Did you install new battery switches or relays that can
isolate load and charge circuits to the batteries that are
monitored by the BMS? Also, if the BMS shuts down the load side, doesn't
this make the entire boat blackout or is it a BMS on each
battery isolating load and charge circuits? If the latter,
I don't understand how the circuits can be isolated when
the load and charge are connected to the same battery.
Thanks for the information on the
Sterling switch. I had no idea that existed. It should be
standard installation on any vessel with a high-output
One thing that is certain here. These batteries are not
"drop in replacements" as many manufacturers suggest.
Vessel - Cream Puff - SM2K - #275
cruising - French Polynesia
On 5/3/2022 9:44 AM, Scott SV Tengah
That's a very valid concern and one that needs to be addressed in
And it has been addressed:
(1) Dean does it through having a secondary, always connected
small AGM bank.
(2) For my Victron based system, if the BMS decided to disconnect,
it ONLY disconnects the load side. The battery bank is still
connected to the alternator and the energy continues to flow. If
the BMS decides that the batteries can't take any more charge, it
doesn't disconnect, it turns off the charging systems.
I don't know enough about Mastervolt, but I'm guessing it's
addressed. I cannot speak to other systems.
With lithium, I strongly believe that people need to understand
how their systems work. Same with their Genoa furler that has
circuit breakers/thermal switches. Same with every system on our
On Tue, May 3, 2022 at 02:44 PM, Mark Erdos wrote:
If a high output alternator is suddenly
disconnected from the battery bank with the engine
running, that electric energy has to go somewhere. Watch
how quickly a fire ensues. I would imagine, if one is
using the bow thruster the engine is most certainly
With best regards,
Sailing Vessel - Cream
Puff - SM2K - #275
Currently cruising -
On 5/2/2022 10:05 PM, Alan Leslie
Everyone has different requirements (and ability to pay!) ...
so everything relevant needs to be considered....those Victron
batteries are VERY expensive !
n=1 studies are often not useful ...on my previous boat I had
AGMs that lasted 10 years, I have an Amel friend who has his
set of AGMs now for 9 years, Ours are 6 years and still
performing.....because they have been well managed.
But I don't think that's the point.
My concerns, still, are around this sudden disconnect
business, and now, about how you deal with periods away from
I can see now that it is possible to have very high short
duration discharges from LiFePO4 batteries, as needed for the
bowthruster, but we had better be sure we have enough peak A
availability so that the battery BMS doesn't suddenly decide
its had enough and disconnect at the worst possible moment.
When Covid struck, we had left the boat in a marina connected
to shore power with a battery charger on and the frig and
freezer running, fully expecting to be back in a few weeks.
A year later I came back and everything was OK.
How would that work with Lithium?
I understand they don't like to be kept charged and actually
prefer to be disconnected - so would it make sense then to
have say one or two AGM batteries (with their own charger)
just to keep the boat going and disconnect the Lithium when
parked for an indeterminate time?
Another option might be, for us, we have a 100A Victron Skylla
battery charger which has a Power Supply mode - maybe
disconnect the battery bank and put the Skylla in Power Supply
mode when leaving the boat??
I really like the potential that LiFePO4 batteries offer but
my concerns, as everyone now knows, are wide ranging....and
developing daily....but not necessarily in the negative!
2007 A54 #69