Leisure batteries

[helen&tony]

Hi
i've just had my main starter battery replaced, as it has been promising to fail for months.....to be honest , I don't know how it has lasted.... Whilst in the shop (a battery specialist) I asked about leisure batteries, and it seems that there is no such animal over here....the nearest thing is a non-spill sealed battery....not the same thing, I know, as it is the construction of the plates that make the difference, so , my question is....does anyone have any experience of using a normal accumulator in a leisure application, and how long will they last, also, if deeply discharged, will sulphating prevent re-charging?
Cheers
Helen

[francophile1947]

I've used my second battery (winterised model) as a leisure battery for about 18 months with no problems.

[helen&tony]

Hi Franco
Thanks....that's the sort of info I need
Cheers
Helen

[patnben]

Hi Helen,

A traction battery should not regularly be discharged below about
70% capacity or the plates will start to buckle. A leisure battery
has much thicker plates and can be discharged to around 40%
without buckling the plates.

If you fit a standard traction battery in parallel with your normal
battery, you could discharge both down to 70% capacity and still
start the Bongo more reliably than a single traction battery due to
the much lower internal battery resistance.

You also have the same power available in leisure mode 2 x 30%
= 60%. All you need is a bit of common sense to ensure that you
don't discharge both traction batteries too far. I have been doing
this for over 4 years and on the odd occasion have reduced my
2 traction batteries to around 50% without any starting problems
in cold weather whatsoever, and I still have the same batteries.

Science is truth, facts only confuse the issue.

[helen&tony]

Hi Pat'n'ben
Interesting....I understand the leisure battery has different construction to prevent buckling, as I have used leisure batteries for very many years, and given some of them a real "working out"....but , frankly, I've never done the "math" as you put it so succinctly, as to just connecting normal starting batteries in parallell as you suggest which will probably solve our problem....especially if I wire a couple of volt meters in to ensure that I don't overdo the discharge.....are there any issues with overloading the alternator if two batteries are discharged to the 70% capacity (for each) level you suggest, and would an earth lead of sufficient length as a busbar 'tween each terminal (plus to plus etc.) cause any risk of fire etc.
Thanks
Helen

[Aethelric]

I guess it really depends on how much you are taking out of the battery, and how long before its charged up again. I've left my lights on overnight before, and been unable to turn the engine next day, but after charging the battery up it still lasted for years. But it would not take that abuse on a regular basis.

Starter batteries can work fine at starting vehicles when a lot of their capacity is gone. A good engine should start in about 6 seconds and take 100Amps - thats 10 ampere minutes out of a "80 ampere hour" battery. Should be easy peasy. But leave the sidelights on overnight, say 4 lights at 6W each for 12 hours, thats only 24 ampere hours, and most cars won't be able to start in the morning!! The battery is fine, it will usually start the car with no problem, its just that its now maybe 3 years old and has nothing like the capacity it had when new. I read a post on here about folk flattening a 110AH battery overnight supplying 4A for an electric blanket. I think there is a lot of specmanship goes into published battery specs. The quoted capacity is only there, under very tightly controlled conditions (usually an ideal temperature and a very low current) and only applies when new.

Personally, I'd prefer to have the starter battery reserved for that purpose, so when I'm camped overnight or for a few days I'm not worried about starting when its time to leave. But I'm quite happy using a separate starter battery as a leisure battery until its no longer fit for service. Then I may buy a proper leisure battery (unless I get a great deal on a starter battery of course)

Dave

[patnben]

Helen,

The factory fitted "Winter pack" has 2 traction batteries fitted in parallel,
and as far as I am aware; uses the same alternator as the standard version.
The standard starter motor is 2 kW but the "Winter pack" starter motor is
2.2 kW and a heavier build quality. To reduce voltage drop, the positive
power cable from the second traction battery on the "Winter pack" is
routed directly to the starter motor terminal; and the negative terminal is
connected to the nearside wheel arch with a short power cable and an
existing 10 mm set screw in the wheel arch.

As you are using the standard starter motor you can simply connect the
2 battery positive terminals directly together using a cable of at least the
same size as your existing negative power cables. Route the cable over,
and fix with suitable clips, to the air inlet hood. If you can find about
4 feet of 20 mm flexible plastic conduit to pass the cable through, then
this will add to the perceived security. As there is no over current protection
in the starting circuits; you should ensure that all positive power cables are
securely fixed with proper terminals; and adequately protected from physical
damage.

Using battery voltage to determine available capacity is only reliable with
healthy batteries which have been at rest for several hours. A fully charged
battery should measure 12.6 Volts, a 50% discharged battery will measure
around 12.2 Volts. You can adopt this method but It's better to do the maths
using the power values for your intended leisure appliances when wild camping.
For a small van, I would much prefer this simple method of providing leisure
power, particularly when the van is used for daily use when both batteries are
always available for starting purposes.

No doubt others will disagree, but suck it and see, at least it hasn't cost a
great deal and very little work, you could easily convert to a split charge
leisure system later on if you so preferred.

PM me with Email address if you would like some photographs.

Ben.

[lev8]

Hi,
I have used regular starting batteries in my boat for years and they cope with a lot of punishment. On the subject of sulphating, last year, I was too busy to get aboard and I let the batteries go completely flat for a few months, the batteries (4) would only take a little charge so, I got one of these http://www.courtiestown.co.uk/ and some EDTA, only one battery failed to recover to normal capacity after 2 weeks of treatment. It had one bad cell and though I could see the innards I couldn't find a short etc, so maybe something broke. I would recommend these see through batteries as well as batteries with the charge plates in separate cells. If your buying good quality they don't seem to cost any more but they give you a lot of added benefit.

[helen&tony]

Hi
Thanks, all, there are some interesting thoughts there. It looks like I shall have to use a standard battery (starter), but I may be tempted to buy a small genny to charge during the day. I shall mainly use the second battery for lighting, music, and electric water pumps, as we intend to make a "cookhouse" trailer, rather than convert the Bongo, as its' multi-purpose role is too valuable to lose. When not in use camping, we will wire a lot of circuits to the second battery, and use the second battery at night to power a bank of roof-mounted spots (when we get around to fitting them). Plenty of projects!!!!
Cheers
Helen

[moonshine]

I also used a starting battery as a leisure battery in one of my previous boats for several years, only replacing it with a proper leisure battery when it finally died.

I am a little confused as to previous references to "traction batteries". Maybe the terminology has changed, but when I worked in the battery charger industry (many years ago), the term traction batteries meant the type of batteries used in fork lift trucks, milk floats, etc., to actually drive the traction motors. These batteries were therefore really deep-cycle batteries and could be safely discharged almost completely. Leisure batteries (a term not used then, we simply called them deep-cycle batteries), fell somewhere between starting batteries and traction batteries.

[helen&tony]

Hi Moonshine
Now there's a thought....I can hunt round the battery dealers, and ask for fork lift batteries....if I can find one of the right dimensions, we'll be "Quids In"....they just don't "do" camping here.
Cheers
Helen

[Chas]

Hi Ben,

Can you clear up some of the terminology used here please. When you say that '....[the]battery should not regularly be discharged below about
70% capacity or the plates will start to buckle'

What is meant by capacity here? Would I be right in thinking it's the amphour rating? So a normal vehicle battery rated at 100Ah can be used to provide (say) 30A for 1hr on a regular basis (or 3A for 10hr) whereas the leisure battery can provide twice that before damage?

Also what is meant by 'regularly' is it a case of you may get away with overdischarging once or twice but more than that forget it?

Cheers Chas

[patnben]

Hi moonshine,

Of course you are absolutely correct that the term "traction" is conventionly
used in association with battery driven vehicles, I simply used the term to
differentiate between a leisure battery and a normal car battery, whatever
that means. I would hopefully justify my use of the term in that I have owned
2 pedestrian controlled fork trucks fitted with "Normal Car Batteries" and the
manufacturers called them "Traction" batteries. I would add that the under
voltage cut out did operate at a much higher load voltage than our normal
fork truck to protect the plates. If this causes more confusion than it was
meant to resolve I will use the term "Starter Battery" with my apologies.

Hi Chas,

To produce the high current required to crank the engine, starter batteries
have a large number of very thin plates packed tightly together to reduce
the weight and size of the battery. On the other hand, a leisure - or deep
cycle battery - has a much smaller number of very thick plates which, while
subject to the same stresses, can resist the buckling effect when heavily
discharged.

As the maximum output current is proportional to the total area of the plates
it follows that leisure batteries cannot produce the heavy currents required
for cranking.

Taking your example of a 100 Amp hour starter battery, The capacity is 100
Amp hours at the manufacturers tested discharge rate which is normally the
capacity acheived with a new battery which has been fully discharged over
a 20 hour period at 20 degrees Celcius, this equates to a current of 5 Amps
for 20 hours. If you draw more current than this; then the capacity will fall
below the specified Amp hour rating. As the reccomended minimum capacity
is around 70% then you only have available for use around 30 Amp hours from
a fully charged starting battery. This is all theoretical stuff according to the
manufacturers, many starter batteries are often discharged well below the
recommended values and appear to suffer no ill effect, but it would be wise
to treat them with respect if you want maximum life from the battery.

The same reasoning applies to leisure batteries except they can safely be
discharged to around 40% capacity which in your example means that you
may expect to draw around 60 Amp hours power from a new battery provided
you don't exceed the 20 hour rating. Normally, if you over discharge a leisure
battery, it's voltage may fall to an extent that fluorescent fittings may fail
to strike.

The moral of this "story" is:
Always charge your batteries at every available opportunity.

[moonshine]

Hi patnben,

thanks for your explanation, I just wanted to clear up any confusion, and you have done that admirably.

Makes me wonder why the manufacturers of your fork trucks fitted car batteries instead of proper traction batteries though. Maybe it was for cost reasons, or maybe they thought that most people would have more access to car batteries when the time came to replace them.

Quite agree with your final comment about keeping batteries as fully charged as possible.

Colin.