I've currentll got one battery on my 26M, but as I have a spare battery from an old scrapped car, I thought it would be a good idea to wire it in with the main battery.
I fancy it would be a good idea to keep the 2nd battery purely as an engine battery so that I'm not left in the position of not having a battery to start the engine, but the big problem is how to wire it up.
There appears to be a main isolating switch which could have a dual battery position on it [as supplied from the factory] as well as a place alongside the existing battery and wiring for the 2nd battery. Can anyone confirm if it is just a simple job to wire in to the existing battery, ie. black negative wire to existing negative, and red positive to existing red positive, [ is that parallel?] or is it a tad more complicated?
Paul
[Ex 'Crackerjack' - 26M]
An update on my query.
I have now wired in the 2nd battery, taking a negative from the original neg terminal and using a positive, already wired into the main on/off switch. It was all pretty undramatic with no sparks or hot wire [thank goodness].
What happens now is that it appears that I can turn either one or the other battery on/off or have both on, or of course, both off. I'm still not sure whether it is worth having one especially for the motor or just not bother. Does anyone have any thoughts?
Paul
[Ex 'Crackerjack' - 26M]
Hi Paul
If you talk to a dozen people about the best way to wire dual batteries, and the best way to use them, you'll get a dozen different answers! There isn't really a "right" way.
For example, my arrangement is one battery primarily for engine starting, and a second battery for everything else. But I can switch things around so either can be a backup for the other one. This requires some more complex switching than you've got.
With a simple switch arrangement like yours you're going to be using one battery for everything at any one time. It's generally best only to have the switch in the "Both" position when the engine is running in order to charge both batteries. If you leave two batteries connected in parallel while not on charge you can end up with one partly discharging the other, because their characteristics will never be identical.
A typical regime is to start the engine while switched to "A" or "B", then switch to "Both" so as to get best use of the engine's charging output. Then when you stop the engine, switch to "A" or "B", depending on which battery you want to use to supply the instruments and whatever else you're using.
When you next come to start the engine, switch over to the other battery, especially if you've been drawing power from the first one for a long time (e.g. after overnight mooring). This ensures you have a fully charged battery for starting.
You don't need to be too pedantic about this though, especially if you don't have a lot of electrical equipment running. The most important thing is only using "Both" when charging (i.e. engine running), or possibly when starting if you have problems starting with just one battery where both together can give an extra boost.
I hope this helps
Rick Jones (Treasurer), former 26X & 19 owner, Isle of Wight
I have one of the other dozen or so variantsthat Rick mentions!
I have 2 batteries - one is dedicated to starting and the other is dedicated to "house supply". I have a voltage sensitive relay fitted that ensures the starter battery is charged first when the motor is started and when it reaches its working voltage the relay trips and diverts the charge to the house battery.
I also have a shore power connection with an "intelligent" charger as well as a wind generator.
All these ways of charging the batteries are to ensure as far as possible that
1. I can start the motor and
2. I will always have enough power in the house battery to keep the beer in the fridge at the requisite temperature.
Mike
That is exactly what I had in mind Mike. When you have the time to think about it, I don't suppose you could rough out a wiring diagram could you?
Paul
[Ex 'Crackerjack' - 26M]
Hi all, having recently become the owner of 'Dixie' an 'M' I am also in the market for a 2nd battery, and read with interest the comments from Rick and Mike. I like Mike arrangement but would like to introduce a solar panel. Has anyone any observations regarding this ?? Chris
I have a wind generator in my set up so I think a solar panel can be installed alonside other charging devices in the same way (however, do check the solar panel instructions to make sure you don't end up burning something out!)
Take a look at BEP marine website concerning VSRs which I think is very useful. Also, the US discussion forum is loaded with info on battery choices - I got tons of knowledge from there.
Congrats on your purchase of Dixie - look forward to meeting you on the water.
Mike
Avoid all the switching and forgetting too.
The charger in on an O/B is a current source.
If you split the charging before the regulator you can charge both batteries separately.
Split the output using half a bridge rectifier from Maplin.
As the charger is a current source the voltage drop across the diode does not matter.
I have used this technique for the last 10 years without any problem.
My motor battery for the past 5 years has been a sealed lead acid from Netto currently at Maplin. It was sold for car starting and tyre inflation and comes with a battery isolator switch, all for £20.
What has happened to the pictures
A picture saves a thousand words.