« Reply #9 on: Oct 28, 2019, 6:27 pm »
Britannia and our other 'occasional use' vehicles and plant are all on mains float chargers.  We regularly get  7-10 years from standard car/truck batteries.  I've had the same car battery in Britannia since purchase and ...hoping I don't regret this ... it still seems more than adequate to start from cold.  I've changed the truck battery twice ... in 29 years.  A cheap continuous charger from Aldi is all that's needed as it doesn't need to do much charging, just keep the battery voltage up. 

Alternatively a small solar panel.  We use that in our RIB to keep the batteries up and recharge if the auto bilge pump kicks in. Throughout the recent wet weather they have always been full when we have tested the voltage. Same cost ( ish ) as a charger and cheaper to run !

The Caravan Club did a review of 'leisure' batteries some time ago and found that a lot of them ( not all ) were just car batteries with a different sticker and much higher price.

« Reply #8 on: Oct 28, 2019, 2:36 pm »

There are a lot of marketing "claims" out there for various batteries but I'm highly sceptical of most/all of them - lead/acid battery tech hasn't made any significant improvement for a century!

There have been some more recent improvements to prolong battery life such as the "Enhanced Flooded Battery" which is still basically a "Wet" Lead acid battery but with better plate design and more importantly the addition of a system to prevent "Acid Stratification" which can occur with a partially discharged battery (About 80% charge level) where you get, after standing,  acid  more concentrated in the lower part of the plates causing sulfaction. In cold weather  on gridlocked roads where batteries don't always get a full charge this can be a problem. Requiring charging with an external charger.
To solve this an AGM (Absorbed Glass Mat) battery can be used where the acid is absorbed in Glass Fibre Matt between the plates which make the battery less prone to sulfaction, and makes it "Spill Proof"
Other bonuses are, lower internal resistance, high currents on demand, long service even when deep cycled, stands up well to cold weather and has a low self discharge rate, maintenance free, lighter than equivalent basic lead acid, and can be charged at up to five times faster. However they are dearer than normal lead acid but cheaper than Gel batteries.

« Reply #7 on: Oct 28, 2019, 11:51 am »
First you need to know what you want the battery for.  A hovercraft should only need a starter battery - the engine alternator/generator will easily produce enough power to supply all of the electrical gear.  First check what type of battery the vehicle that the engine came from required - look for the CCA (Cold Cranking Amps) rating and ignore the capacity (AH) value (you don't need large storage capacity as it's for starting only).  Using the CCA, find a smallest & lightest battery that meets or exceeds it (larger number) that is the correct shape/terminals to fit whatever space layout you need (standard battery code chart is HERE).

Deep cycle (leisure) batteries primary benefit is tolerance to discharge (down to 10%) - they aren't so good at supplying large amounts of current (no CCA rating so shouldn't really be used as a starter battery.  If you keep a vehicle battery charged to more than 30% or so it'll be last for many years (I usually get ten years or more out of standard automotive batteries).  Let it go flat and you risk permanent plate damage - sometimes you get away with it but often not!  If your hovercraft is going to sit around unused for months then fully charge the battery and make sure it is electrically isolated.

There are a lot of marketing "claims" out there for various batteries but I'm highly sceptical of most/all of them - lead/acid battery tech hasn't made any significant improvement for a century!
« Last Edit: Oct 28, 2019, 11:56 am by John Robertson »

« Reply #6 on: Oct 28, 2019, 10:36 am »
Thanks Nick & Warby. Yes, they can take a bit of punishment. As a recreational off roader,,in a past life,, & a 4x4 instructor in the RAAF, I've put a few through their paces. Even a roll over by a student "who knew better!" in an old Land-Rover. Banged the crushed guards (wings) out & drove her home. I'll go with your recommendation. thanks.

« Reply #5 on: Oct 28, 2019, 9:57 am »
Hi Warby,  I need it for the starter but I thought that a marine battery was shock resistant or something.
I've never heard about marine batteries being shock resistant. I would have thought an automotive environment was just as bad for shock loads.
As Nick said there are light weight batteries out there but expensive. There have been big changes in battery technology in recent year. There are now batteries designed for stop/start applications where car engines stop when you pull up at traffic lights etc.
Follow Nick with a good basic starter battery, cheaper and with good maintenance they can last easly 5 years.

« Reply #4 on: Oct 28, 2019, 9:45 am »
Some very special batteries out there now that are light (50%) and powerful etc
Strangely 300% + cost however.  :o
Costs are without doubt.
Benefits aren't necessarily as claimed!
IF you buy a "light aviation" it will be all of the above
but if OKd by microlight aviators ---
THEN- they will have researched well and asked around, so go with that----
or just A Cheapo accepting that AFTER FOUR YEARS of use--- it may be better to THEN have

1 A new cheapo battery REALLY looking after it-
2 Or STILL be using a four year old "possibly special battery" that you've just fitted and forgotten?
All IMHO of course! ::)

Out of interest Ive gone for the looked after cheap one, followed by a repeat of this, after about 3-4 years
Safe rather than sorry.
Weight IS an issue, but more important is starting the engine!!!
Memories are BETTER than Dreams---"Capn" FLINT

« Reply #3 on: Oct 28, 2019, 9:13 am »
Hi Warby,  I need it for the starter but I thought that a marine battery was shock resistant or something.

« Reply #2 on: Oct 28, 2019, 8:11 am »
The term "Marine batteries" generally refers to Deep Cycle batteries designed to supply a smaller amount of power over a long period of time unlike starter batteries designed to supply a lot of power in a few seconds ie starting an engine. The term Deep Cycle generally refers to Lead Acid batteries. Also called Leisure batteries for caravans.
Most larger boats, yachats etc will have a starter battery for the engine and Deep Cycle for cabin lighting etc
With lead acid batteries the difference is in the Plate design.( Google Deep Cycle Battery)
However with the advent of Lithium Ion batteries, I think they will suit both purposes

« Reply #1 on: Oct 28, 2019, 12:10 am »
I have a feeling this has been discussed before, but, all replies appreciated. Thanks. :-[