Do I have a problem here.

[Sneaky Pete]

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I am considering replacing the two batteries, Trojan 70Ah, currently in use on my Oceanis 323. Reason both are 6/7 years old and to upgrade to higher Ah if possible. Dilemma is batteries are in parallel as shown in picture, both are used to start engine, both are used to power instruments and lights when engine doesn’t run. I don’t know what type of battery they are, leisure, DC, CC. Which type do I replace them with. The engine is a 3YM20 Yanmar which starts very easily. I have posted a picture of the switching arrangement. All are shown in the on position, if one of the isolators is switched off engine can still turn and all electrics work, if the other is the one switched off engine can turn and all electrics work. Do I have a problem with this arrangement? Very grateful to comment on these couple of issues.

 

[JumbleDuck]

View attachment 48586 View attachment 48587

I am considering replacing the two batteries, Trojan 70Ah, currently in use on my Oceanis 323. Reason both are 6/7 years old and to upgrade to higher Ah if possible. Dilemma is batteries are in parallel as shown in picture, both are used to start engine, both are used to power instruments and lights when engine doesn’t run. I don’t know what type of battery they are, leisure, DC, CC. Which type do I replace them with. The engine is a 3YM20 Yanmar which starts very easily. I have posted a picture of the switching arrangement. All are shown in the on position, if one of the isolators is switched off engine can still turn and all electrics work, if the other is the one switched off engine can turn and all electrics work. Do I have a problem with this arrangement? Very grateful to comment on these couple of issues.

Your batteries are only in parallel when they are both switched on. If I were you I'd look at getting the biggest battery which fits the space of the current two as house, a small Red Flash or similar filling in the end or nearby as engine start, and rejig the wiring slightly to have separate circuits and an emergency parallel.

 

[prv]

If I were you I'd look at getting the biggest battery which fits the space of the current two as house, a small Red Flash or similar filling in the end or nearby as engine start, and rejig the wiring slightly to have separate circuits and an emergency parallel.

+1

I have two 210Ah batteries, which is probably overkill, but I would guess that one of them would fit in the space and give you a 50% increase in capacity. Then a separate small engine battery, and a relay that connects them together only when charging.

Pete

 

[sailorman]

+1

I have two 210Ah batteries, which is probably overkill, but I would guess that one of them would fit in the space and give you a 50% increase in capacity. Then a separate small engine battery, and a relay that connects them together only when charging.

Pete

this looks a good price & i am tempted to get one, i can then add the existing engine battery into the domestic bank
http://www.mdsbattery.co.uk/shop/productprofile.asp?ProductGroupID=8555

 

[Noahsdad]

As previously stated with a VSR between domestic and engine battery.
This is my set up and no problems.

 

[VicS]

if one of the isolators is switched off engine can still turn and all electrics work, if the other is the one switched off engine can turn and all electrics work

I hope you are not saying that the engine will crank and all electrics work if both are off

If all is wired correctly it should be able to use ( and charge ) either one of the two batteries with that set up.


Choice of battery is up to you and what will physically fit but with that set up so called" dual purpose" batteries would be the obvious choice.


It would perhaps be better to look at a larger deep cycle battery ( or two 70 ah in parallel) to use for domestics and a smaller high rate ( Red Flash or Odyssey) battery to use solely for engine starting but that would mean modifying the battery mountings etc although a compact AGM battery could be mounted somewhere convenient in the engine compartment.
Ideally you would then separate the engine and domestics wiring, change the switching arrangements and incorporate some form of split charging system.

Depends on how far you want to go and how confident you are to make the necessary alterations.

Sorry repeats much of what has already been said while I was typing,

 

[Sneaky Pete]

I hope you are not saying that the engine will crank and all electrics work if both are off.

When the isolators are in the off position all electrics are off.

I was thinking about a separate battery for the engine and the addition of two possibly 88Ah batteries for the general electrics. The removal of the battery boxes would allow for longer batteries either in parallel or as suggested one large battery i could make a small tray to keep battery(s) in place. The engine compartment does not allow for more than what is seen in picture however there may be an opportunity to put an engine start battery into the large cockpit locker. Thanks for the opinions, invaluable.

 

[yoda]

The question that comes to my mind with the current arrangement is to do with charging. Do both batteries get charged if one is turned off? If yes then somewhere you probably have a diode unit of some sort. If not then I would seriously consider some form of splitter/vsr/charging unit so that both engine and domestic banks are charged when the engine is running.

Yoda

 

[pete]

Looks like a similar arrangement to my Oceanis clipper 311 although I only had one battery fitted under the steps and one in a box to the port side of the stern gear under rear berth.

Last year I had a revamp and fitted both the original 80AH house batteries under steps in boxes wired in parallel and a new 65AH starter battery under the rear berth. I also fitted a split charge relay and a Nasa BM-1.

I only did this after the boat came out for the winter but hopefully I won't have to worry as much about flattening the starter battery when moored up without shore power in future.
Pete