Cybers
New Member
Hello, need advice on a battery for my boat? It has a 2 cylinder 20hp Volvo inboard engine. Will a standard car battery be good enough?
What size/type of battery do I need?
- Thread starter Cybers
- Start date
rosssavage
Well-Known Member
More info needed.
Is it a dedicated engine battery? (ie nothing else runs off it..)
If so, yes, a standard car battery would be fine, except there's no such thing as a 'standard' battery, they all have different capacities and physical dimensions.
Do you have the old one? If so, get one with the same numbers on it (xxxAh and xxxCCA) and the same size. If not, measure your battery box and get one to fit. Bigger is better than smaller, and one that is too small won't have enough CCA (cold cranking amps..) to turn your engine over.
If in doubt, go to your local motor factor / Halfords spotty yooff and get one suitable for a small diesel engined car.
Is it a dedicated engine battery? (ie nothing else runs off it..)
If so, yes, a standard car battery would be fine, except there's no such thing as a 'standard' battery, they all have different capacities and physical dimensions.
Do you have the old one? If so, get one with the same numbers on it (xxxAh and xxxCCA) and the same size. If not, measure your battery box and get one to fit. Bigger is better than smaller, and one that is too small won't have enough CCA (cold cranking amps..) to turn your engine over.
If in doubt, go to your local motor factor / Halfords spotty yooff and get one suitable for a small diesel engined car.
PaulGooch
Well-Known Member
Leisure batteries are sensibly priced now, so i'd fit one of those. They have a bit of extra plate support compared to a car battery, so might last a bit longer. As Ross said, fit the biggest you have room for (within reason).
dingdongs
Well-Known Member
heres a site for an idea but leisure battery can be discharged and recharged many times whereas a car battery will not survive once you have other devices running from it. http://www.alpha-batteries.co.uk/leisure-batteries/ ;
Jurgen
Well-Known Member
Have used these guy's before for all of my boat batteries, really good service and changed a duff 1 without quibble
www.batterymegastore.co.uk
www.batterymegastore.co.uk
Tranona
Well-Known Member
If it is a dedicated engine start battery then anything recommended for a small diesel engine car will do that fits the space you have. Engine start batteries have a really easy time in a boat, provided you have a good charging system to give an instant charge when you have used it. If you have an alternator and you run the engine enough to get it up to working temperature each time the battery will last for years.
The problems start if you want to use the same battery for powering your other electrical requirements. Then you need to consider having a separate house bank and a split charging system that always ensures the start battery is charged first and wire the boat so that all the services come from the house battery. Sensible also to have some way of using the house battery to start the engine in an emergency.
VicS
Well-Known Member
Yes and i think you will find that your owners manual probably specifies a 60Ah battery
The Americans seem to have a different philosophy. They opt for a main battery for all purposes, starting and domestic, and a reserve battery that can be used if necessary. The main battery gets priority charging.
ITYWF that it is what is described in Nigel Calders book.
Cybers
New Member
Thanks to all, very good info. The original battery was a old car battery that didn't work..... Which is why I was scratching my head a lot, the only electrics I will be running are nav/stern lights, VHF, gps and fishfinder.
rosssavage
Well-Known Member
In that case a leisure battery would be better.. Again, big as you can (sensibly) get.
VicS
Well-Known Member
In what way did not work ?
If you will be running much load without the engine running ( like a sailing boat does running nav lights etc all night) then I agree a Leisure battery may be a better choice
Dont forget LED lights can reduce your battery drain enormously
Cybers
New Member
Bought the boat as a non runner so was dead and wouldn't hold a charge after a couple of attempts of charging it......
Cybers
New Member
Thanks for all the advice it's been great, forgot to say the engine has a hand crank just incase of electric start problems which works so am thinking that just 1 battery would be sufficient. Have ordered a leisure battery which set me back £75 which ain't as bad as I was expecting.
Assassin
Well-Known Member
Never use a leisure battery as a main engine battery, the reason people use leisure batteries is for leisure items.
Leisure batteries are not designed for the large starting currents required by a starter motor, which effectively short circuits the battery, they are designed for low drain applications. It is a common misconception thet they are the same as a car battery, they're not, stick to a car battery.
If you want a one battery system then opt for a traction or semi traction battery, they are designed to cope with the high current of a starter motor and will cope with small discharges, and suffer heavy or total discharges without damage.
Leisure batteries are not designed for the large starting currents required by a starter motor, which effectively short circuits the battery, they are designed for low drain applications. It is a common misconception thet they are the same as a car battery, they're not, stick to a car battery.
If you want a one battery system then opt for a traction or semi traction battery, they are designed to cope with the high current of a starter motor and will cope with small discharges, and suffer heavy or total discharges without damage.
PaulGooch
Well-Known Member
Completely and utterly 110% wrong.
Assassin
Well-Known Member
If its wrong them please explain why so many people using leisure batteries for starting engines suffer so many issues with defective batteries, and why even the manufacturers tell you not to use them for high drain applications such as starting engines. Are they all wrong.
[2068]
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Most leisure batteries have thicker plates than starter batteries.
They should last better if being discharged by lights, fridges, etc.
For use as a starter battery as well, just choose one with enough cranking amps (it will end up being larger/heavier than a similar capacity starter-only battery).
They should last better if being discharged by lights, fridges, etc.
For use as a starter battery as well, just choose one with enough cranking amps (it will end up being larger/heavier than a similar capacity starter-only battery).
Assassin
Well-Known Member
This is correct, they do indeed have thicker plates. This is nothing to do with starting as it is for protection of sturdiness when they are heavily discharged, a conventional starter or car battery will go down to around 10.5 volts, below this it will be scrap, a leisure battery will often go as low as 9-9.5 volts without damage, hence the thicker plates.
Car or engine batteries are rated by their amp/hour rating and cold cranking amps, or A/H and CCA rating, leisure batteries are only rated by their A/H rating and are normally based on what is called the discharge rate. In simple terms; if we have a 100 A/H rated battery it should give 100 amps of output for one hour, it wont, you will be lucky to get 100 amps for more than a few minutes, this is due to its dicsharge rate which is commonly the 20 hour cycle, specialised batteries can have the standard 40 hour cycle.
To calculate the battery rating you take its A/H rating and divide it by the discharge or cycle.
100 A/H rating divided by 20 hours = 5
What is this 5? this is the maximum amps discharge it should have, or in simple terms a 100 A/H leisure battery will give a maximum of 5 amps output for a guaranteed 20 hours. 5 amps X 20 hours = 100 amps; Simples.
Car or engine batteries are rated by their amp/hour rating and cold cranking amps, or A/H and CCA rating, leisure batteries are only rated by their A/H rating and are normally based on what is called the discharge rate. In simple terms; if we have a 100 A/H rated battery it should give 100 amps of output for one hour, it wont, you will be lucky to get 100 amps for more than a few minutes, this is due to its dicsharge rate which is commonly the 20 hour cycle, specialised batteries can have the standard 40 hour cycle.
To calculate the battery rating you take its A/H rating and divide it by the discharge or cycle.
100 A/H rating divided by 20 hours = 5
What is this 5? this is the maximum amps discharge it should have, or in simple terms a 100 A/H leisure battery will give a maximum of 5 amps output for a guaranteed 20 hours. 5 amps X 20 hours = 100 amps; Simples.
[2068]
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Agreed, but the point is that there are dual-purpose leisure batteries that will be quite happy working as starter batteries.
Something like this:
http://www.tayna.co.uk/EXV125-Enduroline-Calcium-Leisure-Battery-P8758.html
Or this, which is what Flower Power currently has (x3).
http://www.tayna.co.uk/Numax-CXV30HRMF-P3673.html
Something like this:
http://www.tayna.co.uk/EXV125-Enduroline-Calcium-Leisure-Battery-P8758.html
Or this, which is what Flower Power currently has (x3).
http://www.tayna.co.uk/Numax-CXV30HRMF-P3673.html
Assassin
Well-Known Member
These are an example of the semi-traction batteries I refer to.
We have the same issues with 4X4's where electric winches are used, often the faster winches use very high powered electric motors, and we also use at least a semi traction battery to replace the original battery, in most cases its a traction battery.
I think you may be confused with terminology, its all to do with cycle, a conventional car battery has a medium duty cycle, a semi-traction has a deeper cycle, and traction batteries have deep cycles.
We have the same issues with 4X4's where electric winches are used, often the faster winches use very high powered electric motors, and we also use at least a semi traction battery to replace the original battery, in most cases its a traction battery.
I think you may be confused with terminology, its all to do with cycle, a conventional car battery has a medium duty cycle, a semi-traction has a deeper cycle, and traction batteries have deep cycles.
PaulGooch
Well-Known Member
It is you who is confused by terminology. I'd suggest you do some research on Google as i'm off on out on my boat and don't have time to explain it all.
