Gardner 3LW Charging

[BoaTedandDad]

Hello All, I'm slowly refurbing our 3LW on our boat and have had the dynamo sent away and refurbed which is 12v and now like new. We have bought a new engine mount, large front pulley and Leece Neville alternator which is 12v but our starter motor is 24v. My plan was to keep it simple and have two very separate systems with the dynamo doing nothing but charge the starter batteries and then the alternator charging the leisure batteries. I want to keep the leisure side 12v and run everything on the boat on 12v. The issue I'm having is going from the 12v dynamo charge to the 24v starter batteries. Today it was suggested using a series parallel switch to overcome this but I am out of my comfort zone on this and would appreciate any advice. Has anyone else installed the system I was thinking of doing? Am I barking up the wrong tree? I know I need a regulator for the dynamo which I have and  that is a 22amp one, other than that I was looking at converters (12v to 24v) but I've held off yet as I'm not convinced. Appreciate any suggestions and help.Thanks in advance guys.

[David Mack]

Can't help with the specifics of your question, but what was the arrangement before the refurbishment? Did it have a 12V dynamo and 24V starter? And was the starter battery 12V or 24V? How was it all connected up?

[Tony Brooks]

39 minutes ago, BoaTedandDad said:

Today it was suggested using a series parallel switch to overcome this but I am out of my comfort zone on this and would appreciate any advice

 

At one time I think Mercedes vans used an automatic switch that parallel the start batteries when not starting and put them in series when the starter was operated, so I think a properly wired switch (if available) would do it.

 

The start battery should be always all but fully charged, so a 12 to 24 converter fed from the domestic bank would also d the job. It won't need to have a very high output.

 

A dynamo won't charge unless it has a regulator connected to supply the field current, and if you fed the field direct from the output or battery it would very quickly burn the dynamo out, so you need a regulator if you intend to use it.

[agg221]

@Ben Jameson has 12V charging and a 24V starter motor. He may be able to comment on whether what has been suggested matches his installation.

 

The other option would be to find a 12V starter motor. I can't see it in your picture but my guess is that you have a CAV BS5. These are available in 12V and 24V and this is the route I took. They show up for the Gardner, Kelvin and some Fordson tractors.

 

Alec

[BoaTedandDad]

4 hours ago, David Mack said:

Can't help with the specifics of your question, but what was the arrangement before the refurbishment? Did it have a 12V dynamo and 24V starter? And was the starter battery 12V or 24V? How was it all connected up?

Hello David, I think the best way to describe it was a snakes wedding! There were some 15 batteries laying all over the boat when we took delivery and the concerning thing was that the starter was powered by two batteries but one of them was a leisure. This with random wires chopped and joined all over gave me absolutely no confidence at all hence I decided to start a fresh and remove everything. Both the dynamo and starter are the originals, I sent the dynamo off to be tested and rewired which has now been completed. I'm yet to fit it and wire it in.

4 hours ago, Tony Brooks said:

 

At one time I think Mercedes vans used an automatic switch that parallel the start batteries when not starting and put them in series when the starter was operated, so I think a properly wired switch (if available) would do it.

 

The start battery should be always all but fully charged, so a 12 to 24 converter fed from the domestic bank would also d the job. It won't need to have a very high output.

 

A dynamo won't charge unless it has a regulator connected to supply the field current, and if you fed the field direct from the output or battery it would very quickly burn the dynamo out, so you need a regulator if you intend to use it.

Thanks Tony, I have the original regulator and found a brand new one when stripping the boat out, so I'm happy with that part. I was also told that toyota used the same principle on the early Land cruisers, looking online earlier it seems caterpillar use one on certain machines but its a US purchase by all accounts.

4 hours ago, agg221 said:

@Ben Jameson has 12V charging and a 24V starter motor. He may be able to comment on whether what has been suggested matches his installation.

 

The other option would be to find a 12V starter motor. I can't see it in your picture but my guess is that you have a CAV BS5. These are available in 12V and 24V and this is the route I took. They show up for the Gardner, Kelvin and some Fordson tractors.

 

Alec

Thanks Alec, yes its def a CAV and I believe it to be a BS5. I have looked all over it for a stamp to confirm its a 24v as I'm only going on how it was wired to tell me this. There are no markings that I can see (obviously had the cover off and looked around the servo etc) but as said above in another reply, I have so little faith in what I found especially the fact it had a leisure battery on the starter. This may have been desperation to get it started or was it put on and then another battery added as it wasn't man enough. Which of course it wouldn't have been in all probability.

[agg221]

Yes, that is a CAV BS5 (assuming it has a 5" diameter body; if it's 6" then it's a BS6 but that would be unlikely).

 

What is written on the plate with the two connecting terminals on it?

 

The only way I found to test mine was to try starting the engine with a single known good starter battery - it was sluggish. I then added a second known good starter battery temporarily and it was vigorous! I have now swapped mine to a 12V which works fine on the single huge truck battery (900CCA so it had better!)

 

Alec

[nicknorman]

Normally when you have a big (old fashioned) engine with 12v alternator or dynamo, and 24v starter, you connect the dynamo or alternator to one of the 12v batteries. A contactor (big relay) when at rest puts the other 12v battery in parallel with the first, so they both get charged when the engine is running. When you press the starter button /turn the key or whatever, this powers the contactor solenoid which moves the second battery connections to be in series with the first and connects to the starter.

 

Not sure where you would find such a contactor but the one I am familiar with was on an old lorry, so lorry type places or old fashioned auto-electrical people might be able to help.

[BEngo]

When built, the operating voltage of a BS5 starter is stamped or sometimes printed on the paxolin plate that the three terminals are fitted in.

 

If the plate has been renewed or reversed during a repair the voltage marking  may be missing.