Battery capacity at anchor.

[Driver]

We often anchor overnight and top up the lead acid batteries with the generator as necessary. When the voltage drops to 24.5v and I know we will be moving/cooking soon, I use the parallel switch to extend the capacity by connecting the engine start batteries. I do not let the voltage drop below 24v. The engines start happily at this voltage, are seperately recharged and the generator has its own battery. Any harm in this please?

 

[Driver]

Should have said " I do not let the voltage drop below 24.5v"

 

[DavidJ]

My preference would be to not use the parallel switch to extend capacity but to charge the ‘house’ battery with the generator if required.
I’m thinking at night if a storm kicks in and you start to drag anchor you need to 100% guarantee that the engines will fire up, turn of the switch.
I’d like to see 13V (in my world) on the dedicated starter battery at all times.

 

[Hurricane]

Whats the boat?
IMO, none of the main builders allow enough battery capacity.
I used to get through a set every couple of years.
You can run that campaign of charging in the morning etc but they never fully recover so after about 3 days away from shore power they drop dangerously low.
My solution seems to have worked.
I installed some solar panels - not enough to fully charge the batteries but enough to finish the daytime charging without using the generator all day.
Our campaign is now to run the generator for an hour or so in the evenings (also run the aircon to cool the cabins).
Then let the batteries do their bit overnight.
And hit them again in the morning, charging at a high rate for a couple of hours.
Batteries charge fastest when they are most depleted so finishing a charge using the generator is a bit inefficient.
But the solar panels take over that low current charge during the daytime.
The net result is that I can keep pace with the charging/discharging and the batteries now don't get dangerously low.

Also, don't measure the batteries with voltage alone.
If you haven't got one, get one of those Battery Monitors and monitor the battery state by %age
Victron supply their BM series (I think thats their name) - these days, their battery monitors report to a phone over Bluetooth.

 

[SC35]

Our domestic batteries will last a couple of nights without issues.
The only time I would use a link switch would be to start an engine - I have three domestic batteries that also start one engine, and a dedicated engine start battery for the other engine.
I don't ever want to be in a situation where I can't start any engine!

 

[Driver]

Many thanks for all of your replies to this and my parallel post. Its a Pearl 50. I am not worried about starting the engines, they always spin well at 24.5v. Then there is always the seperate generator for back up. I think I will fit solar panels, a job for next winter, but my current concern is to not cause any damage by bringing the smaller start batteries on line for the time being.

 

[Paulfireblade]

Normally leisure batteries and starter batteries are a different composition to cope with the different type of discharge profile of the two different circumstances so your starter battery is unlikely to be ideal for the leisure environment.

Solar sounds a far better solution.

 

[Hurricane]

Normally leisure batteries and starter batteries are a different composition to cope with the different type of discharge profile of the two different circumstances so your starter battery is unlikely to be ideal for the leisure environment.

Solar sounds a far better solution.

Actually, boat builders like Princess use the same batteries for the engines as the house set.
Ours certainly are.
I did buy a set of AGMs once for the house set but their performance wasn't any different to the wet lead acid so I didn't see the point of spending any more on AGMs or Gels.