winter rewiring project

[bobgosling]

Current (pun intended) set-up is a 55A alternator charging a
70Ah engine battery and 85Ah domestic via an old-fashioned relay switch, i.e. not voltage sensitive. Domestic is loaded with the following :
Navman 7200 DSC-VHF (has a built in digital barometer)
Garmin GPSMAP 130 (greyscal LCD low power)
Nasa Navtex
Rule Bilge pump
Eberspacher (knackered at the moment but may get it fixed)
JRC1500 Radar
Nasa Log, Depth, Wind
Autohelm ( rarely used )
Car stereo
Nav lights
Cabin lights

I have obtained an X-Split 3 output unit and want to add more to the domestic bank by adding another 85Ah ( same make as current - which is only a few months old ).

I believe that traditionally with 2 domestics one is set up as 24 hour services with the other for everything else. In my set-up that would put just the Eber and bilge on one battery. I'm thinking of adding the VHF-DSC and GPSMAP and Navtex to that battery too. With it left with a small solar panel trickle charging I'm hoping to get to the boat with Navtex loaded and VHF's barometer showing latest trend. A good 20 minute engine run to get out into my sailing area should stick enough charge into it I hope. 20 minutes back again too.

Reason for adding the GPS to the same battery as the DSC-VHF is that it just feels "wrong" to not have them on the same battery.

Does that sound sensible ? What would you do ?

Boat, 28ft Seal, is kept on a mooring with weekend "pottering" use and hopefully next year a cross channel trip.

 

[KenMcCulloch]

Dear Bob
I have been studying up on electrics because when I took over Border Maid I found the electrics to be a priority for upgrading. I am by no means an expert but the first thing to say is that it reads like a very long list of (in some cases power-hungry) devices even for 2 x 85Ah batteries. An overnight passage under sail with the radar on (remember if it is fitted you are more or less obliged to have it on) navlights VHF and instruments is going to make a very big hole in 85Ah. The starting point should be having adequate battery capacity - add up your loads for the longest anticipated period between charging, and double the figure in Ah to give an idea of the capacity you need. On Border Maid for example I just have a VHF, basic GPS, Bidata Log/ES and nav lights and 85-100 Ah is reasonable.

It's common just to wire the domestic batteries in parallel although some - usually larger - boats I have sailed on do have 2 domestic banks and a separate engine battery. I think the idea of having a battery dedicated to the radio and GPS is a good principle, but if the quid pro quo is running everything else off one battery, and your navlights starting to fade after 5 or 6 hrs I would have another think. I have found 'The 12 Volt Bible' a really useful source.

No doubt someone who actually knows what they are talking about will be along soon.

Cheers

 

[bedouin]

I think you should first ask yourself what you are trying to achieve by having two separate domestic banks - and that depends on the sort of use you make of the boat.

In general I would say stick to a single bank, with batteries in parallel, unless you have a good reason to do otherwise.

For example with the split you suggest, if you were doing an overnight sail you would find the bank powering the lights, radar and instruments taking all the load with your second bank doing very little. Under those circumstances you would probably find that a 12 hour night trip drained that bank well below what was desirable.

 

[alldownwind]

In general agreement with others, I'd simply parallel the two domestic batts. In which case you could trade in your 3-output X-Split for a (cheaper) 2-output one (excellent bit of kit IMHO).

 

[Malcb]

My set up on my 23 footer, is 2 x 85Ah batteries, Somoya Combi battteries, that support both starter and domestic via a 2-1-both-off switch.

I have an on board mains Sterling charger system, and a 70Ah Alternator.

My output, apart from the normal nav lights, depth gauge etc. is Navman Chart Plotter, Navtex, Autohelm (operating via the Chart Plotter (sometimes), Waeco 18 Ltr Fridge (which has a battery protect system), and a TV.

While cruising round the Solent, and to the West Country, this year, I've never had to use more than one batttery, i.e. the motoring during the day, puts enough power into the batteries, so that I can run all of the above, and start the next day, without switching to the other battery. That is on nights I was on a mooring with no shorepower. If I was on nightly shore-power, then obviously no problem.

So most times, I really only need one battery, the other is in reserve. Bearing in mind that before I start, because of the Sterling battery charger, my batteries are really very well topped up.

I'm going to add a radar system tihs year, but I won't change the batteries.

I do, however, carry a 'PowerPack' for those unforseen little emergencies, and for blowing the dinghy up (via a High Speed Inflator) /forums/images/graemlins/laugh.gif