VSR/ACR before or after main switch?

[oilybilge]

I few years ago I fitted a Blue Seas SI-ACR to my 24-foot sailing yacht. (It's a standard two-battery system, with a 120ah house battery and 80ah starter battery. The boat is on a swinging mooring, and we don't use much electricity.) I connected the ACR downstream of the main switch, since there was no reason for it to be on when I was off the boat, and I liked the idea of being able to switch off absolutely everything when going ashore.

However I've now fitted a 70w solar panel, and I'm wondering whether to move the ACR to the battery side of the main switch.

The pros and cons as I see them are:

Pros: when there's enough sun, the ACR will close and both batteries will get a charge, not just the house battery.

Cons: It's one more thing to go wrong. For instance, it doesn't always disconnect. Sometimes the little green 'Batteries Combined' light shows for hours after the engine has stopped, and only goes out when I briefly turn the main switch off and on again. I'm rather nervous about leaving it to its own devices for up to a month at a time.

Has anyone had good or bad experiences of either arrangement?

 

[Daverw]

It’s probably staying on as the battery voltages are still high. With solar onto your house and vsr switched in both batteries will be as charged as available power.

Even if it stays on what problem will this cause if no other loads are on? Have you fitted a solar controller?

 

[Tranona]

It is really only the house battery that needs the solar. Your current system is not ideal. Better to keep the 2 banks separate with their own isolators and use a VSR to split the charge from the alternator and then wire the solar just to the house. There is really no need to combine the 2 to start the engine in normal circumstances although some people do provide a link switch to use the house bank to start the engine in an emergency.

Alternatively fit a BEP Marine switch cluster bepmarine.com/en/p/716-SQ-140A-DVSR/Square-Btery-Distribution-Cluster which I have used on my last 3 boats

 

[Stemar]

On a similar boat, with similar needs, I used one of these, set to charge the engine battery first, then the domestic, because the engine battery should rarely need anything, but I always want it topped up.

EP Solar Duo-Battery Solar Charge Controller 12/24v 10A. £33.30

The alternator was hard-wired to the engine battery and a split charge relay, energised from the ignition warning terminal on the output when the engine was running.

A budget system, rather than a high performance one, but it worked well for years.

 

[oilybilge]

Even if it stays on what problem will this cause if no other loads are on?

None whatsoever, as long as everything behaves itself. It was really horror stories like this from a fellow Finesse-owner...

Batteries discharged by faulty VSR

... that made me wonder if the (minimal) risk of, say, a VSR getting stuck in the closed position and draining both batteries outweighs the (minimal) advantage of charging the engine battery when I'm off the boat. That's all.

 

[LittleSister]

. . . For instance, it doesn't always disconnect. Sometimes the little green 'Batteries Combined' light shows for hours after the engine has stopped, and only goes out when I briefly turn the main switch off and on again. I'm rather nervous about leaving it to its own devices for up to a month at a time.

That used to happen to me and is normal. It stays on until the batteries dissipate their higher 'float charge' (is that the correct term, I can't remember?), which is higher than the VSR shut off voltage, and can take quite a time if time if your batteries are in good condition and you've no, or only a tiny, load on them. I found the time it stayed on reduced significantly as my batteries got older, and in any case if there was any significant load on either battery it would go off almost immediately.