Fitting a domestic Battery

[Martin007]

Hi, this is my first post, and I am in the process of trying to make improvements to my second boat purchased late last summer.

I want to fit a domestic battery but have very limited experience with 12V electrics. Is this something that is relatively straightforward and what are the typical pitfalls I should look out for. Are there any books that will 'walk me through the installation'

Many Thanks /forums/images/graemlins/smile.gif

 

[ShipsWoofy]

12V Bible

This should give you all the advice you need.



Right Click THIS LINK and select save target as.

It is quite large but worth the wait.....

 

[guspw]

Re: 12V Bible

Martin,
A year ago I taught myself 12V marine electronics from books and internet. I subsiquently installed an entirely new charging system including a smart alternator regulator, voltage sensitive relay(VSR) split charging, solar panel regulator and all new wiring, fuses etc.
This had to be done as the old system was a complete mess and would simply destroy batteries and never supply enough power.

this took quite a lot of reading before gaining the confidence to buy and fit anything but once at that stage it was fairly straight foward for me and the system works like a dream (can easily handle 30 hour crossings of the irish sea under sail).

It can appear complicated at first but there are lots of books that will tell you everything you need to know and work out. The one posted above is a good one but also check out some more recent publications as I found there have been some usefull advances in technology i.e. in VSR's
The main thing is to carefully work out your requrements (as the books will tell you) and build a system on paper before jumping in and buying the things the glossy brochures tell you you need.

I found Merlin Power-Store (01202603742) very helpfull in working out what I actually needed (even before I became a customer!)

 

[boatmike]

A very good little book is "Boat Electrical Systems" by Dag Pike Published by Adlard Coles in paperback 1992. It has the advantage of assuming you know absolutely nothing about electrics at all and tells you all you need to know in words of one syllable. Thoroughly recommend it.

 

[Stemar]

I second ShipsWoofy's suggestion, well worth downloading this. If you understand everything in that little book, you'll know more than plenty of so-called experts /forums/images/graemlins/smile.gif

When I did mine, I kept my current domestic installation and added a starting battery.

What you'll need to do is separate the engine's electrical system, including the charging circuit from the domestics, then come up with a method of charging the domestics.

I use a relay energised by the charge warning light to alternator connection. On a big boat with sophisticated systems, you'd be better off with fancy battery voltage sensed gizmos like the Adverc or Stirling, but the relay works as well as a plain internally regulated alternator, such as you probably have at the moment. IMHO it's all you need on a small boat with simple systems - and the relay only costs a fiver!.

If you would like a circuit diagram and a bit more detail, pm me with an email address.

 

[Evadne]

Some good notes on marine electrics (and other subjects) at this site at Reading University.

 

[Andrew_Fanner]

Re: 12V Bible

Where might one obtain a VSR? Searching the Maplins and RS websites have not produced anything meaningful, unless I'm asking for the wrong thing.

 

[Guest]

VSR site ....

www.kddpowercentre.com

I have no connection with this - other than a very freindly correspondence with him - who obviously knows what he is talking about.

/forums/images/graemlins/cool.gif

 

[pvb]

VSRs...

Merlin sell the BEP range of VSRs.

 

[Stemar]

Re: VSRs...

IMHO you don't need a VSR for a simple system. I use an ordinary relay, switched by the warning light contact on the alternator. This is around 0v when not charging and 12v once the alternator's spun up, so it charges both batteries in parallel. I used the dynastart relay from my old engine, but if I hadn't, I'd have used one of these

 

[bluedragon]

Re: VSRs...

Using a relay to bring in the domestic battery makes sense and the charge control light circuit seems a neat way of doing it (in fact I might well do this in my current re-wire)...but I think the VSR adds something a bit extra for not much more cost. As I understand things, it senses Battery 1 voltage and brings battery 2 in when 1 is close to fully charged. This means the engine battery gets priority immediately after engine start. Is my understanding correct??

 

[halcyon]

Re: VSRs...

Depending on type, you can also charge battery 1 from battery 2 if you have a solar panel etc fitted to battery 2.

Brian

 

[TonyMS]

Re: VSRs...

In the past I've made my own shunts.

Get some resistance wire from Maplin - about 4 Ohm/m. Wind enough turns round the terminals of your low-current meter, or somewhere closer to the load, but also in parallel with the meter. You need enough turns so that at your planned highest current your low-current meter reaches full deflection.

To calibrate, you have to put this now shunted meter in series with a known meter.

Tony

 

[pvb]

Yes...

Yes, you're right. It's called a VSR (Voltage Sensitive Relay) because it measures the voltage on the primary battery it's connected to (usually the starting battery) and only closes to charge the secondary battery (usually the domestic bank) once the primary battery has charged up to a certain voltage.