Single sensing VSR ....

[simonfraser]

Ok, not looking for a witch hunt / or i told ya so.

As another forumite pointed out, all batteries providing charge will have a reduced voltage, obvious.
So as i have a dual sensing VSR and a solar panel the VSR is basically always latched when i start the engine.

The single red top starting battery is clearly man enough to start my engine in the cold. But, if you look at the red top battery site it does not recon they ‘fit’ for v big engines 5l etc. so i have fitted a second red top in parallel. Probably overkill, but i just don’t need the hassle of it not starting on a Sunday morning. And two reds fit, a larger wet battery does not. (Guess what, the 35A VSR fuse still blows when starting with two reds)
So have taken the fuse out of the dual sensing VSR.

Another foumite suggested a single sensing VSR.
I just want to be 100% clear what i could do:
Single sensing, that is going to be sensing the start battery.
If the solar is high on the house side, the VSR will not latch.
If i have the dual shore charger (engine and house) on, the VSR will latch as the start battery is over 13V.
Disconnect the shore charger and trundle down to the slip on the trailer, now the start battery may still be 13V for a few minutes.
But then i lower the leg, powered by the start battery.
And switch the ignition on, this will lower the start battery voltage to 12.5V, glow plugs on the diesel i guess.

So now the VSR is not latched any more ?
Start the engine and the 35A fuse for the VSR wont blow ?

Now the alternator pushes the start battery voltage up to high 12V and the VSR latches ?
Then i pull the chain up with the windlass, will the VSR disconnect straight away, or stay latched and thus the 35A fuse will still blow ?

I dont want to fit some humongous fuse to a VSR, e.g. 100A, even though a VSR may be able to take it as 100A from one battery to the other just does not sound right. And if there is a battery issue i want the fuse to blow asap.

Am i making sense ?

 

[pvb]

My god you're making hard work of this! If you don't want to fit a sensible fuse in the VSR connection, my suggestion would be to take out the VSR and sell it on eBay. Replace it with a low-loss splitter - this will take the alternator output and share it between the start batteries and the house batteries, but will not let the start batteries discharge into the house bank. There are various makes, I have a Quick ECS163 which has 3 outputs; if you only need 2 outputs, there's the ECS162 at around £135. The Sterling Pro Split R is a similar device.

https://www.mareshop.eu/boat_uk_en/quick-ecs-162-charge-separator-2-outputs-160a

 

[PaulRainbow]

Forget the VSR.

Fit a low loss splitter, such as https://www.batterymegastore.co.uk/victron-arg100201020-r.html

It will charge all of your batteries from the alternator. It will never parallel the two banks. The solar will charge the domestic bank, but not the Red Tops.

 

[Hoolie]

I agree you're not making proper use of the VSR so you might as well remove it.

I have a Smartguage/Smartbank system that acts like a dual-sensing VSR but the three banks are connected by high current relays 150amp continuous and 450amp short duration. When the relays are activated the batteries are interconnected as a single large bank.

The alternator is connected to the starter battery, so if for instance I'm using the windlass with the engine running all the batteries provide current. That's the way it's designed to work.

The mains charger is connected to the house batteries and when it's on and the volts are over 13.6 the other two banks are also charged. When the house bank voltage falls, the relays cut out and each bank is then separate and the starter and windlass batteries don't discharge.

I have a couple of solar panels that I am going to connect to the house bank. Again when that's up to the threshold voltage the relays kick in and all the batteries will get solar charged.