I need a permanent live 12v feed, suggestions please?

FullCircle

FullCircle

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I have a need for a permanent live 12v feed to a couple of items on the boat.
These are:

CD Radio unit memory
Webasto Combi Timer clock and settings
Alarm (to be fitted)
VHF? (Good idea or not?)

I have the common 2 leisure batteries and a starter battery, and really don't want to add another battery. Obviously the current 3 batteries go through a 3 separate isolator switches system (1 Negative and 2 positive) which feed the main bus.

How do you view taking a feed direct off one of the leisure batteries and then switching/fusing it seaparately, or is there a small rechargeable supply I can fit in the main feed which will supply the small amperages I need for these 'tickover' functions?

Thanks
 
I have permanent (fused) feeds to my bilge pumps, which is normal practice.

I would not bother with a permanent feed to a VHF I see no point in that personally.

As for the clocks and radio memories I have a nice little 12v sealed lead battery (the type used for house alarms) which I intend to fit one day (tum te tum). My intention is mainly to feed the radio memories. I hope to have it completely seperate and charged via a mini solar panel, probably the trickle charge type, they appear to be good enough to keep up with the radio drain.

As they are designed to keep up with a power cut in the house and still fire the house alarm for so many minutes (I dunno) I suspect this might also be a solution you could consider, thus maintaining your house batteries remain killed via the main switch.

What I am trying to find out, as the small battery I have is 2.45Ah is whether or not I should be fitting some sort of regulator if using even I tiny solar panel.
 
I have run the feed for the hi-fi direct to the house bank with an in-line fuse; exactly the same way it's done on a car. Have to do the same if you wanted leccy bilge pump. Not that you need one in a car!

If you are worried about the draw on the batteries, how about a little solar panel?
 
I have a seperate wire which comes off one of my two domestic batteries which feeds similar items to your list. I have an inline fuse where the wire comes off the battery. I would not worry about the amount of power that will be used, it should be very little.
 
Initially I had my memory for the stereo connected to a 125Ah battery. The battery was not left in brilliant shape charge wise and a few weeks away from the boat determined it was flat as a pancake on our return.

The drain is tiny, granted; but it is still a drain and not a good idea to leave, especially with an alarm draining away too. In a car it is expected you will be using it regularly.

I now have a wind generator because I hated charging the batteries with the engines, hence why I allowed a radio to flatten the bank.
 
Jim,

Why not put in a seperate switch panel from the normal 1/2/all switch feed, and then leave the switch panel permanently on.... that way you can, in the worst case also isolate these drains.....

You can get switch, that have a flip up cover to operate (aircraft style), and so wouldn't be knocked off by accident.....

Gives you best of both worlds....
 
J
its not the drain that concerns me, its the safety integrity of the electrical system, as my boat is a long way out on the trots. Alarm will be one of those that phones me and says'Yer boats being nicked!'
The VHF is because I have a Silva S15 with Navtex incoming.
Unfortunately, charging with a wind generator will not happen unless I can get a cheap serviceable used setup, as I have it in mind to get a DuoGen, and I am saving for that. I already have a Kawasaki 4 Stroke Genny which can be pressed into service for those dire flat battery moments. In reality, the batteries have stayed in a good state of charge with my usage pattern.
 
The safety is not an issue as long as you use the correct components. Ensure you use a correctly rated fuse close to the battery. You can still use a switch, for my bilges for example I use a heavy 3 way rocker, ON-OFF-ON (auto switches).

Are you suggesting leaving the silva switched on all the time to receive navtex? Did they make the S15 to allow you to switch off the VHF side and still receive navtex?

I can give you a good example of why not to leave a VHF switched on while you are away:

Last year in the middle of summer we were leaving the boat at around midnight, it was a very still night and we were just pottering down the harbour with the o/b just more than tick-over. Next thing all hell broke loose as a DSC Mayday alarm started, obviously on someones external speaker. We could not talk above the mercury outboard but now could not hear the outboard over this alarm 200yds away somewhere on the marina.

The alarm went on and on and in the end we saw staff running down from the marina offices trying to locate who had forgotten to turn off the VHF. Cabin lights around the marina started to come on.

Do you want to be that person who wakes up the whole anchorage. Returning to your boat with a broken hatch and the wires pulled out of the back of you radio by a drunk sleepy sailor who has been kept awake by your radio screaming for 30 minutes????

Just a thought!
 
Good point about DSC, but already have that covered for when we are on board, at night.
Switch radio to external speaker only.
Switch External Speaker off, on rocker switch. In the event of DSC, no loss of sleep.
You are right though, scratch VHF from the want list.
It seems sensible to have the fuse near the battery too, except if it blows, I wont know where to look(or maybe the next owner!) until I remember which could be a while. Switch with cover also sounds good, and I think illuminated too.

My bilge pumps are bizarrely on the main switch panel, so thats another good idea from Dogwatch Electronics Inc.

Now all I need is a source of nice looking switches that fill the bill.
 
The 12 volt sealed batteries normally found in fire alarms and good quality (not domestic) security alarms, are designed and rated to keep the`alarm going for a minimum of three hours.
Same applies to emergency lighting batteries.
We test all of ours at School for longevity twice per year.

A good quality battery like a Yuasa NP series unit will commonly last about Ten years in my experience.

Steve
 
Do you envisage any problems using a trickle charge solar panel to leave charging for one of these? I was thinking of the wallet type you see in argos or maplin...

The one I have is a GasTon 12-2.2 (12v 2.2AH / 20HR)

I know very little about battery charging....
 
I would use one of these as close to the + terminal of battery as you can (or feed side of isolator) then cable to your permanently live accesories as required.
 
No there shouldnt be any problems at all with charging a sealed lead acid battery.
They are designed to be left on float charge constantly whilst the mains is up.
Some of the charging circuits on some alarm panels are quite primitive, just a rectifier, capacitor and a voltage regulator basically.
I think you would be able to connect your solar panel directly, without too many problems.
You will of course need to develop more than 12V for the battery to charge.
A gentle 13.5 to 13.8 is the usual voltage.

Steve.
 
In my opinion the tiny 2.4AH SLA batteries can be easily damaged by overcharge. However I also suggest that your permanent current drain for radio alarm etc may be significant as compared to the output of a small solar panel. My experience was that a 2watt solar panel in Oz summer would not maintain the battery when a car radio memory was connected. But without the drain it keeps the battery fine. Maybe I had a high current car radio.
The point is you need to check the current drain of radio and alarm. It seems to me a real possibility that the solar panel could kill the battery if the permanent drain was disconnected Yet not maintain the battery with the load on. So a regulator may be appropriate. But then you may as well spend the money on a bigger battery or use one of the ships batteries with a little solar boost. olewill
 
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