New to this scene

[rob]

Would 100ah start my Johnson 90hp outboard...?

[daveinglasgow]

yes and if it is a VRO model please turn it off and pre mix as they often stop working and that will kill your engine!

Dave

[rob]

Thanks dave, didn't know you could turn it off...! I'd rather mix it myself as I've heard some stories of engines being wrecked with oil starvation.

[daveinglasgow]

they are renowned for it so when playing with these engines even in the workshop we use premixed fuel!

[Paulsjenny]

Hi rob , with the batteries , I have a 100ah Liesure batt and a normal car batt , I also bought a solar panel (£25)and put it in the window so the the starter battery (car) is always getting a trickle charge , just something for you to think about . Works for me

Paul.

[rob]

Hi paul, there was a car battery in my boat when I bought it but it's not holding the charge.
Thanks
Rob.

[Coddy]

What are the main differences between car batteries and leisure batteries ?

Leisure batteries and car batteries both make use of lead acid technology. That is to say they are both plastic boxes that contain rows of interconnected rectangular flat lead plates and a mix of sulphuric acid and water.

The main priority of a car battery is to provide starting power for the vehicle. In addition it will provide a stable flow of power for the car electrical systems. A car battery cannot be allowed to remain far below 'full charge' for any length of time without physically degrading and permanently losing performance.

The main priority of a leisure battery is the flow of power with engine starting coming secondary to that. Some leisure batteries are not actually designed for starting engines while others have both capabilities.

The internal structure of a car battery contains many, thin lead plates. The surface area* of all of these lead plates combined allows for the strong boost of power required to start the car engine.

By contrast a leisure battery contains fewer plates, each of which is physically thicker.

Each lead plate, when submerged in sulphuric acid and water is capable of storing and releasing energy. A thick plate will release its energy slowly. A thin plate will do the opposite.

Over the past century car batteries haven't changed much in their basic design. Engineers, by experimenting with different numbers of lead plates, different sizes and thicknesses, managed to create lead acid batteries for specific jobs.

So why do leisure batteries tolerate being fully discharged and why do car batteries not?

The chemical reaction between the acid and the lead plate causes atoms known as electrons to jump from the (+) plates to the (-) plates. In doing so the basis of electricity occurs.

When a car battery stands for a period of time without recharging, the thin lead plates minus their electrons will sulphate and degrade. Their performance will be reduced permanently.

Thicker plates, because of their smaller surface area* rarely lose 'too many' electrons and will not suffer the same level of destruction via sulphation. This means that a leisure battery can stand being fully dis-charged and will ultimately power your appliances for a good deal longer before needing replacing.
(* surface area to mass ratio)

There are also Deep Cycle Batteries which are built to directly power electric motors, heating elements, winches, compressors, fridges, information processors and other electrical devices. they are designed to allow repeated full 'dis-charging' and charging without shortening the lifespan of the battery.
An ordinary lead-acid car battery is kept topped-up all the time by the car alternator and never runs flat. If it does - its life will be foreshortened significantly as it cannot survive being below 90% charge for very long. This is a trade-off in the form of CCA (Cold Cranking Amps) power instead.
Deep Cycle Batteries by contrast are built with heavier charge and discharge cycles in mind and can be used up fully / remain uncharged for longer periods of time with less deterioration and fewer adverse affects on the overall performance.

I hope this clears up any misunderstandings about batteries.
Yes I work with batteries as part of my job.

Dave

[davidemania]

Very clear and interesting indeed

ciao
Davide

[rob]

Wow, everything you wanted to know about batteries but were afraid to ask...!
Thanks for that dave,
Rob.

[rob]

they are renowned for it so when playing with these engines even in the workshop we use premixed fuel!

Hi dave, what's the ratio for the mix...?