I am no physics expert, I enjoy learning
on the job and I feel I learnt a lot over the past weeks about batteries
schemes and types of use etc thanks to the many contributions on these topics on CF. I am about to change batteries
and am facing some questions that I hope I can get advice on. Here is the context.
batteries (2xFLA) have started to loose strength down to a point where I had to choose between AP and fridge to keep voltage above 12v in day-long (over 10hrs) passages last summer. They are 7-8y old. During one winter (2y ago) I inadvertently left the boat
(on the dry) with the shore power
cable connected to the boat
(but not to the grid) and service
batteries went down to 3v, something that hit them a bit (reduced amps) but did not kill them though. I had so far no real clue of the need to ensure they were as close as full prior to leaving the boat for a week of 2 throughout the sailing season. Topping them up was my only routine I must confess.
I did quite a bit of reading on CF and elsewhere in order to assess the best way forward.
Boat is 37ft, central cockpit
hence not much place for solar
, aft being covered by packed dinghy
and access to platform and seats in the aft corners, the best place to sit when it gets sunny and not too bumpy. An arch would be the solution but since I’m only coastal sailing at the moment I consider this too much for now. Outside of the pushpit on each side could be a 2nd best. But for now all I need is to secure a day of passage
with sometimes anchoring
overnight (with possibility to run the engine
if needed) with consumption
of max. 120Ah (and up to 180Ah at anchor).
bank is composed of 2x 140Ah FLA batteries for service and 1x 70Ah maintenance-free lead acid for engine
. Condition of the latter looks great with 13.1v 2 months after haul-out. Service bank is currently around 12.6v but rapidly goes to 12.4v under load and lower when running the Ebenspächer heater
or else. Service also supplies bow thruster (580A) and windlass
(Lofrans, 800 or 1000w? not sure).
Last WE I went to the boat again and tested the charger
with the various options for battery
types. The model is a smart charger
Hitec from Tecsup 12v/25A yet is 20y old. To my half-surprise, boost voltage was lower than the specs in the manual for each of the options. This convinced me to not only buy a new set of batteries but also a new charger. The type would be Victron 12v/50A smart charger (smart as in smartphone, it allows connecting with Bluetooth, a cool feature to better understand what is going on), it will work
well with the newly acquired BM (BMV712) that will measure SoC and consumption
. Its shunt is rated 500A.
After much reading and also given the room available in the battery box
, I am considering to put 4x T-105 that will provide 450Ah. This larger bank will avoid going too deep on DoD. However I was wondering about the following points:
- is T105 ok to operate the windlass
and the bow thruster? Engine is always running when using any of them, yet not sure if they would be too hard on the batteries?
- does the shunt power (500A) allow for the peak consumption from either bow thruster (580A is quoted, which I suspect would grill
the shunt) or windlass, whatever the highest - or should I separate these from the shunt that will be coupled to the service bank?
- the charger comes in 2 versions: with 2 or 3 separate outputs. If the answer to the first point is that windlass/bow propeller
should not draw from the T105 , then either I opt for the 3-output model and place or try and find another type of battery
. If from the secont point, then 3-output mode with a separate start battery would be the solution?
- would installing solar
in the future influence any of these elements?
I very much appreciate any input on these!