Up until recently, with the engine running, even at low revs, the alternator was charging both the starter and the house battery banks with no problems. Then for no apparent reason only the starter battery is receiving a charge. I am sure the problem is likely to be something very simple but I find boat electrics overwhelming. I have checked for a tripped fuse and have found nothing. I am hoping this forum can give me some things to check before I invest in an electrician.

The boat is on a swing mooring. Shore power has not been used for ages, but there is a solar panel which keeps both battery banks topped up. 

Photos here, if that helps.

All help appreciated. 

 

No reason to hire a professional. The culprit is your Stromat SV1, which is charging the engine battery first, and only when the engine battery reaches 13,8 V will the old fashioned relays click (yes you can hear it), and start charging the other battery groups.

I guess that you can find a manual for the Calira Stromat on the internet, but is is rather simple.

In an emergency you would appreciate to be able to start your engine, while stereo, refrigerator and TV are less important. Therefore the Stromat charges the engine battery first. If the engine battery drops below 12,8 V, the relays will cut off power to anything but the engine battery.

The cables from the Stromat are marked I-II-III, it is important that II is the one connected to the engine battery. On my boat Hanse had installed the cables wrong.

You can use the search function to get more information about the Stromat.

https://www.myhanse.com/relais-swtitch-battery-charger_topic12098_post99211.html?KW=stromat#99211" rel="nofollow - https://www.myhanse.com/relais-swtitch-battery-charger_topic12098_post99211.html?KW=stromat#99211

P.S.

As owner of a H370 I suppose you know Marco's homepage?

http://www.wesailhanse.se/370_manuals.htm

After my first winter I had similar issues.  It turned out that the team at Greifswald had removed a 125A fuse in the engine compartment, just to the left of the engine battery, whilst winterizing.  They left the fuse on the chart table but by the spring they'd forgotten where it came from so I set off without it fitted.

After reporting charging issues and reminding them of the "spare" fuse they asked me to check in the engine compartment.

I can't remember if my issue was the house bank not charging under engine or shore power, but it might be worth checking for a blown fuse.

A photo of the inside of the Stromat may explain better than words.

In this thread, as well as in others, the function of the Stromat Current distributor/Ladestromsverteiler, does not seem to be fully understood.

Some myhansers have upgraded to a better/more expensive model, and it is evident, that the Stromat from 2005 is tecnically old-fashioned.

Remember that the engine battery (and the alternator) have to be connected to the terminals marked (II).

(Available in the US??)

All it is doing is delaying charging the house bank until the engine battery has reached a designated voltage.  In reality the engine battery is only used for a few seconds (admittedly with a high current) so shouldn't need more than a few minutes to get fully charged.

Instead of relays I would go for a battery splitter. This isolates the battery Banks from each other and also allow the alternator to charge multiple Banks at once.

You need the mosfet type. Both Sterling-power, Victron (argon FET) and Vetus has battery splitters.

I have installed such a device in my old boat, not difficult.

In an emergency you can connect your consumer batteries with jumpstart-cables to the starter batteries, but I would watch this closely to see if anything gets hot.

A boat is a big hole in salty water suitable for throwing large amounts of money in.

If your boatbudget is large, change the Stromat to a modern item. Otherwise just make sure, that alternator and engine battery is connected to II on the current distributor.

My Stromat is 16 years old and makes clicking noises from time to time, but otherwise works okay.