Twin Batteries

[Gas]

Sorry to be a pain but some time ago I know I read a post regarding wiring two batteries with a relay and it had a diagram I thought I saved but can

[mw]

Try codies web site I think its on there

mark

[Gas]

Thanks Mark got it.

[Brian]

Instead of using an ordinary relay, as on Coddy's site, I used a Voltage Sensitive Relay. This way when the altenator output reaches 13.7 volts the batteries are linked as soon as the voltage drops they separate. The relay cost

Edited January 13, 2011 by Brian

[wotu2uk]

Craig,

 

If you look further in the BEP catalog, they do the two isolating switches, the bridging switch and the VSR as a set, with the correct labels on (house, start and emergency), linked in the form of a square, with bridging links.

 

There is a Poole firm which does ALL BEP stuff, including the hard-to get bits,

 

John

Edited January 13, 2011 by wotu2uk

[duncan]

am I the only one who thinks that such 'solutions' are a sledgehammer to crack a nut for our usage profiles?

 

with the exception of just after starting the engine, if it's running I have over 14v in the circuit ie alternator output voltage so what would such a VSR do for me?

 

going the whole hog to a smartcharging system is a different matter, and I understand the relationship between charged state and usable charge - and it's importance in cruising boats!

 

while I'm at it I always find it amusing that these diagrams show the engine battery at a higher Ah than the ancillaries...but that's another thing entirely.

[lady jane]

while I'm at it I always find it amusing that these diagrams show the engine battery at a higher Ah than the ancillaries...but that's another thing entirely.

 

duncan,

out of interest how should they be shown ?

it was interesting with grahams optima that it was only 50 a/h but has a cca of 800 for a weight of 17kg against a normal heavy duty battery 140 a/h with 760 cca for a weight of 35 kg.

thanks,

andy

[Brian]

while I'm at it I always find it amusing that these diagrams show the engine battery at a higher Ah than the ancillaries...but that's another thing entirely.

The reason the diagram I put up showed the batteries like that is:

My boat came with an 85Ah Leisure battery and I happened to have a brand new 105Ah starting battery so rather than wasting money, I used what I had.

I didn't bother with isolating switches etc, as the boat lives at home in my driveway, I decided to keep things simple (less to go wrong).

[duncan]

while I'm at it I always find it amusing that these diagrams show the engine battery at a higher Ah than the ancillaries...but that's another thing entirely.

The reason the diagram I put up showed the batteries like that is:

My boat came with an 85Ah Leisure battery and I happened to have a brand new 105Ah starting battery so rather than wasting money, I used what I had.

I didn't bother with isolating switches etc, as the boat lives at home in my driveway, I decided to keep things simple (less to go wrong).

Brian

 

I hadn't realised that you had 'created' that particular diagram - my comment was based more on a generalisation.

 

I have also noticed that we tend to have 'bigger' starter batteries because starting the engine is important! The reality however is that a good condition high CCA battery for the starter, and high Ah (possibly low CCA) for auxiliaries.

 

I will also admit that I used to designate the larger battery as 'starter' for years before I thought a little more about it - both are high CCA units. This habit was partially fed by such diagrams.