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Guidance for newbies to motorhoming about maintaining leisure batteries
Coming new to motorhomes has been a steep learning curve and we have made lots of mistakes (getting stuck in the mud on a poorly chosen grass pitch first time out for example). The biggest mistakes to date have been, of course, to do with battery mismanagement and you can read about our ‘battery woes’ in this previous post:
https://wherenexthun.blogspot.com/2021/02/the-continuing-saga-of-motorhome.html
We have been doing some reading up on battery management and now share our findings in this blog post, aimed at newbie motorhomers like us.
We tackle the following questions about leisure
batteries:
·
Why do we have a leisure battery in a motorhome?
·
What type of leisure batteries are there?
·
How do we choose an appropriate new battery for Bryony, our
Autosleeper Broadway EB?
·
How should we charge our leisure battery during winter?
·
How should we look after and maintain our leisure battery so that
it works effectively and lasts much longer?
Any useful references are
listed at the end of this post.
Why do we have a leisure
battery in a motorhome?
Our leisure battery is a
Hankook DMC27 90Ah deep-cycle sealed lead battery, of calcium construction,
100% maintenance free and with a 4-year guarantee so it is a pity that we ‘inadvertently’
reduced it to 11.8v by misunderstanding how the EC700 unit and Sargent systems
work in our motorhome!
It is located under one of the
bench seats and the first thing any beginner needs to do is use the handbook to
find the location of theirs.
Our leisure battery:
·
runs all the
power in the habitation unit when not on an electric hook up (EHU)
·
runs the lights,
water pump, toilet flush, heating, and anything else requiring a 12v charge
e.g., trackers and alarms
·
anything we
have plugged in when off grid (remember it doesn’t supply a 240v power, only
12v, so anything that requires 240v power/has a three-pin plug cannot be run
off the leisure battery)
·
smooths
out irregularities in power supply to prevent power spikes/surges
A battery works by:
·
storing
power which we need to put into it
·
not taking
any more power for storing when it is fully recharged
·
the power
level in the battery falling as we use electrics in the habitation unit
·
slowly
dissipating its power over time, irrespective of whether we are using it or not.
(It will drain away even if you switch off EVERYTHING!)
We should
·
never
allow the battery power level to fall below 50%, and
·
always recharge
it when it falls to 50% charge
Remember that a vehicle battery
is different to a leisure battery:
·
Vehicle
batteries start engines and so have thinner plates and are designed for short,
fast bursts of high power to start up an engine and are recharged by the
alternator
·
Leisure
batteries allow a slow release of power over a far longer time period and then
need recharging (deep cycling) - see later notes on charging a leisure battery.
·
Only AGM
type batteries can be used in both roles
·
In most
cases a vehicle battery cannot be used as a leisure battery and visa versa
A good breakdown of the
internal workings of a leisure battery can be found at:
We found useful charts to put in
our handbook (see below) and it is worth learning how to use a multimeter to
check the voltage charge of your batteries, if you don’t know how to do it.
Note that a 100% fully charged
battery is 12.7v. A 50% charged battery is 12.2v. Don’t fall into the trap that
we did, of thinking that a recharged battery showing 13.5v means it has been
really fully charged. This just happens when you charge a battery up. It may
well show this higher voltage but that is temporary and four hours later it
will be around 12.8v or so.
What type of leisure batteries are
there?
The main batteries we quickly
look at below are:
·
Open and Sealed
Lead batteries
·
AGM
batteries
·
Lithium-ion
batteries
·
Gel
batteries
Open and Sealed Lead acid batteries
These are the most common
battery type, containing a liquid inside (electrolyte and are often known as
‘flooded batteries’). Lead plates sit in this liquid (sulphuric acid solution).
‘Open’ batteries have removable caps through which you can top up electrolyte
fluid using de-ionised water, so that the plate tops remain covered. Exposed
plate tops lead to sulphation and damage so that the batteries won’t hold their
charge.
·
Advantages: cheapest option for a leisure battery
·
Disadvantages: require regular maintenance
and checking of electrolyte levels, very heavy (eats into payload), become
permanently damaged if they go below 50% discharge
Sealed lead acid batteries are maintenance free and
designed to operate for a certain number of cycles.
·
Advantages: maintenance free, safer than open battery type
· Disadvantages: more expensive than open lead acid battery, permanently damaged below 50% discharge, relatively heavy
AGM stands for Absorbent Glass Mat. There is matting between the plates which absorbs the electrolyte solution in the battery.
·
Advantages: resilient, can be used as starter and leisure batteries and be
discharged slightly lower than 50% without damaging them; cope better with
vibrations and cope with more recharging cycles than lead acid types
· Disadvantages: expensive and recharging must not go above 14.2v
Similar to AGM technology, gel batteries are leak and maintenance free. Instead of matting there is thicker gel. They tend to be used more in vehicles where there is a high risk of crashing or damage e.g., jet skis, quad bikes etc. Electrically, gel batteries are unlikely to perform any better than wet acid type batteries.
·
Advantages: can be discharged down to 20% without permanent damage, good for
frequent off grid motorhoming, generally longer service life in temperatures
over 25C
·
Disadvantages: more expensive than lead acid
or AGM batteries, perform poorly on high charge/discharge rates, must not be
charged higher than 14.2v
Lithium-ion (LiFePO4) batteries
·
Advantages: self-contained and maintenance free, contain own charge manager,
cope better with frequent discharges down to 20%, last longer than most battery
types, half the weight of other battery types, great for extended off-grid
motorhoming
·
Disadvantages: significantly more expensive
than other battery types
Finally, there are lead crystal batteries but we
haven’t found out much about them. The electrolyte is in crystal form.
·
Advantages: self-contained so no spillage risk, can be very deep cycled,
little risk of sulphation, can better tolerate heavy discharge loads e.g., from
an inverter or from continuous charging from solar panels
·
Disadvantages: more costly than lead acid or
AGM batteries
How do we choose a new leisure battery
for ‘Bryony’?
We read that there are only three reasons to replace a
leisure battery:
·
the old
one has lost capacity and won’t hold its charge
·
the
battery flattened badly and died
·
the
battery is no longer suitable for your particular ‘power’ needs
We seem to have ‘rescued’ both our batteries but in
truth, only time will tell. We have tentatively booked a local trip in late
April/early May down to Cornwall, lock down restrictions allowing, to do a
little ‘off-grid’ motorhoming as a check on how both batteries cope.
But what if we do need to buy a new leisure
battery?
We could do a straight replacement, like for like, or
we could look at an alternative battery type; or we could get a similar one but
of a higher rating.
How do we decide? What might influence
our decision making?
Well, we could start our thinking by asking ourselves
some questions:
·
How often do we ‘anticipate’ going ‘off-grid’ and for how long each
time?
·
What ‘essential’ things in the motorhome use power off the leisure
battery? (e.g., tracker, alarm etc?)
·
What 12v appliances do we have in the habitation unit and what ‘watt
hours’ do we need from the battery to meet their demands? What battery capacity
size will this dictate?
·
Do we want to consider a dual leisure battery set up? What impact
would this have on our payload calculations?
·
What solar panel system do we have and what is its wattage outage? How
effective is it in winter recharging our batteries?
·
What physical space do we have for the leisure battery – what are
the dimensions of the current storage box – length, width, height? Is there
safe space for a further battery or a bigger battery in the existing space?
·
How many times do we want to discharge down to 50% and then fully
recharge a leisure battery? (known as cyclic life – the higher this is, the
more work the battery can do during its life in your motorhome)
As you can see from above, a major consideration is thinking
about how long your leisure battery lasts in terms of how many
appliances can be used before it drops to its 50% discharge level; and in terms
of the length of time to keep it before replacing it i.e., lifespan.
These deliberations partly depend on the power rating
of the existing battery you have. Ours is a 90Ah capacity. So, we could drain
off it 1Ah (Amp hour) for 90 hours or 10Ah for 9 hours. Of course, we wouldn’t though
would we, because you can only allow it to drain down 50% before recharging, so
in essence we could do 1Ah for 45hrs or 10Ah for 4.5hrs before needing to
recharge it fully.
How long a battery will last in terms of years
depends on how many of these discharge and recharge cycles the battery goes
through. With proper care (topping up electrolyte levels etc, not allowing it
to drop below 50% discharge and careful, steady recharging using a smart
charger), then a leisure battery should last 4 years at least.
Go out and measure the physical space available
for your battery before making any decisions because if you opt for a
larger capacity battery it will probably be physically bigger.
Consider your battery capacity requirements. We personally think that 90Ah is probably the minimum you would want for a leisure battery and is fine if you mainly use sites with EHU’s and occasional one night off grid pitch ups. 100Ah or 110Ah would probably be better if you are planning lots of off-grid motorhoming. (We are not sufficiently knowledgeable yet to discuss the implications of getting a higher capacity battery than the one you might have. Given our experiences, we would certainly want to discuss with our dealer the implications of fitting a higher capacity battery with regard to how the EC700 unit and our current solar panel system would be affected).
If you read our ‘battery woes’ posts, you will already
know that an alternative we are investigating is the addition of another solar
panel so that both will supply sufficient charge over winter to both the vehicle
and the leisure batteries. Then we won’t need to worry about them holding their
charge over winter. We could do this and then replace the battery with a higher
capacity one as well we guess.
One tip from the Camping and Caravan Club that they see as a rule of
thumb is:
“The heavier the battery, the
more lead it contains and therefore it has the ability to hold a larger
capacity of charge. If you want a leisure battery to provide power to perform
deep cycling, a heavy battery is a good place to start.”
There is a ‘verified leisure battery scheme’
to help perspective purchasers. The National Caravan Council (NCC) run
the scheme and publish a list of batteries which meet the verification
process. The website for this is at
https://www.thencc.org.uk/Our_Schemes/ncc_verified_leisure_battery_scheme.aspx
The NCC have three categories of battery
·
Category A – high storage capacity, good for lengthy periods away from EHU
·
Category B – EHU used on majority of trips with occasional off grid work or
power demands from power hungry devices
·
Category C – covers basic operation of habitation equipment and short periods
off EHU
Another thing to think about when choosing a new
leisure battery is what draw will each of the appliances you will be
using have on your battery? Now we confess, because this now involves a
little maths, one of us is rather hazy about what follows (he took five tries
to get his maths ‘O’ level at a C grade!!). And one of us isn’t that interested
in electronics and leaves it all to him!
Anyway, if you find out the wattage draw of
each appliance commonly used in your motorhome and then estimate how
many hours you might use it during a typical day, you can work out what
capacity battery you might require for your needs. Remember to include
the charging of devices such as smartphones and laptops in your calculations,
as well as alarms and trackers.
For example, our 12v TV draws approx. 2.5Amp hours
and on average we use it for four hours each day. This equals 4 x 2.5 = 10amp
hours. A water pump might draw current of 0.7amps every time it is used. We
might use the pump for thirty minutes a day so 0.7 x 0.5 = 0.35amp hours.
By totalling up the daily amp hours usage of our
commonly used appliances, we can then work out how many Ah we use off-grid per
day and therefore what capacity battery we might need. For example, if our
total Ah use per day was 33amp hrs, and we were planning to be off-grid for two
days that would be 66amp hours we would need from our leisure battery. That is
a huge amount given we don’t want the battery to fall below its 50% discharge
level either. Hence, we fit solar panels to give some charge back to our
batteries during the day. So now we’d need to look at our solar panels and what
charge they give to our batteries and factor that in as well.
Bottom line, we are still getting our heads around
this part of understanding our battery system and so will be relying on our
dealers to help us decide whether to uprate our battery, or add another solar
panel, or do both!
How should we care for our leisure
battery?
And this is where we say “We wish we had known
this beforehand”. But, as always, we are often heard to say “You don’t know
what you don’t know”.
Let’s start with knowing how to check your
battery levels:
·
Remember if you have driven the motorhome or had it
recently connected to the mains or an EHU, you must let things settle for four
hours as the reading will be higher than normal. Remember the chart at the
start of this post? At 12v, a leisure battery is considered to have reached a
discharged state.
Also remember:
·
the
capacity of your battery determines how long it can provide power before it needs
recharging
·
capacity
is expressed in Amp Hours (Ah). The higher the Ah on the battery, the longer
period the battery provides power for and the longer it takes to recharge
fully.
·
there are
of course, other factors that will affect your battery performance, such
as:
·
its age (5
years +?)
·
its size
(Ah capacity to start with?)
·
your
appliance consumption demands (how much power you use over what time period and
how often you have to recharge it?)
·
the temperature
(cold will lead to worse performance)
When caring for your battery:
·
charge it
up immediately after buying it (in case it has been sat on a shelf for a year
or two) OR ensure you buy this year’s battery (look for the date on it)
·
install it
correctly using high quality connection clamps (not crocodile clips). Clean the
terminals and coat them with a thin layer of Vaseline
·
Know which
appliances are doing a constant draw on it e.g., trackers and alarms, or
reversing cameras
·
also know what
amp draw your other appliances do
·
monitor
electrolyte levels in lead acid batteries regularly and top up with de-ionised
water where necessary. The electrolyte should cover the top of the lead plates
·
make sure
the gas relief tube off the battery is secure and not crushed when placed in
the hab unit and that it is exiting the unit correctly
·
always
wear correct protective clothing – safety goggles, protective clothing and
gloves – you are dealing with acid
·
always
recharge when the battery reaches 50% discharge
·
if taking
the battery out of the motorhome, store it in a cool dry place and charge it
fully before storing; then put it on a periodic maintenance top up charge
throughout the storage time
·
never overcharge
it i.e., leave it permanently on a mains connected charger – but you could
leave it on a permanent mains hook up IF you have a timer clock plug within the
set up – which allows you to leave it on charge for only four or five hours a
day
·
don’t
reverse the polarity by mixing the connection clips
·
don’t let
anything cross the attached terminals so that it causes a short circuit – this
is a fire risk
·
over
winter (or during a prolonged lock down)
o
charge it
before leaving it on site
o
attach a
trickle charger to it
o
avoid
leaving it on permanent mains unless you have an intelligent battery charger
o
consider bringing
it home to charge up at least once per month but remember your tracker may be
disabled if you remove it from the Moho
o
ensure
that your solar panel is giving sufficient input to overcome any draws on the battery
– so that overall, the battery does get topped up during the day even despite
the weaker levels of sunshine in the winter months
o
switch off
the EC unit if you have one!!
You can charge up your leisure battery in the
following ways:
·
on a mains
EHU every so often
·
as above
but permanently on using a timer switch as outlined above
·
taking it
for a long drive every few weeks so that the engine alternator charges it up to
around 80% – long means an hour+ journey time. (We read somewhere that using
the engine will never fully recharge a leisure battery but we can’t now find
where we saw that point made so that we can verify this fact further - sorry)
·
using
solar panels on the roof, or as a portable fold out set-up
·
using a
generator (but since we have never used one ever, and assume it would need some
form of inverter, we don’t feel remotely qualified in any way to comment on
this method – sorry)
·
using a
portable charger unit
https://www.youtube.com/watch?v=p4gJeV3yNOo&list=WL&index=261
Horton (see references below) pointed out in his blog
post that how efficient your onboard charger will be at charging your leisure
battery, will depend on the age of your Moho.
He also acknowledged that some motorhomers don’t really regard the
onboard charger as a ‘true’ battery charger since they rarely charge up the
battery beyond 13.7v (and this wouldn’t therefore allow you to get the best out
of a new gel or lithium-ion battery). On the other-hand if you have an
‘intelligent’ charger onboard, then this is likely to take these batteries to
around 14.8v – much better.
From our personal viewpoint, given our distrust of
our EC700’s erratic behaviour and the failure of our solar panels to overcome
the draw demand of the tracker etc (see our previous posts on our battery woes)
we think the best way to charge our leisure battery is to remove it, bring it
home and periodically charge it up with a good quality portable plug-in battery
charger (before returning it back to the van for a few weeks so that it can power
the tracker once more). But this is our personal preference and many
experienced motorhomers will argue the best way is to have the Moho on the
drive at home, plugged into the mains on a timer switch.
Which ever way you decide to charge up your battery,
note these points:
·
different
types of leisure battery prefer different rates of charge
·
always
check the rate of charge recommended by your battery manufacturer
·
long slow
charges are better than short fast ones
·
before
charging a battery, ensure it is disconnected from everything so that nothing
interferes with the charge
·
flat
batteries will struggle to absorb a charge initially and it may take a couple
of hours before a charge shows on the meter
·
if a flat
battery is recovered it is unlikely to ever regain its former performance level
So, what kind of portable chargers are
there?
“You pay’s your money and you take your chance”.
Buying a cheap charger is a false economy because it
could overcharge your leisure battery and cause ‘off-gassing’ and/or ‘boiling
dry’. The plates get exposed, sulphation occurs, the battery dies –
permanently. There is also a fire risk as well with the gassing. Remember
sealed batteries cannot be topped up with electrolyte to replace that lost off
in gassing!
There are different types of portable charger:
·
cheap, basic, unregulated chargers – the voltage can reach 15v as
the battery reaches full charge; this is too high for low maintenance charging;
and, there is nothing to drop this voltage - so, there is potential for damage.
Such a charger would need turning off as soon as a 12.7v battery charge is
reached
·
semi-automatic chargers – cut out at around 14.4v for low maintenance
battery and 15.2v for a standard battery. Thus, they monitor the state of
charge and turn off when the charge is reached.
·
Fully automated leisure battery chargers (also called multi-stage
chargers) – are the best and most expensive. They can be left on permanently
connected to the battery without overcharging it. Most have 3 stages – a
constant current with rising voltage to the batteries maximum state of charge
(bulk charge); then a constant voltage which is gradually lowered (absorption
stage); and finally, a dropped voltage with steady current (the float stage)
·
Good semi or
fully automatic chargers will also check battery temperature, provide
overheating protection and alter the charging settings accordingly
·
Our Ring charger,
for example, has seven stages and includes a desulphation stage, a
reconditioning stage and a soft start stage.
With regard to what the best
portable chargers are – we don’t do
recommendations as such and we don’t gain financially in any way from
mentioning a product. However, from reading various forums, popular brands seem
to be Numax, CTEK, Ring and Halfords. We read that the bigger your charger, the
quicker it will charge your battery – a 16amp charger will charge a 100Ah
battery from 50% to 100% in just over three hours whilst a 4Amp charger would
take just over twelve.
There are off-grid
options for charging your leisure battery
but we feel it would be very cheeky of us to try and summarise these in this
post given we have yet to do any off-grid camping in the motorhome. So, we
refer you to this web page from the Camping and Caravan Club which seems to
give a good summary of what can be done.
We hope this post
has helped you improve your knowledge and understanding about your leisure
battery and what you need to do to maintain it in a healthy state so that it
meets your needs and lasts you several years.
If you have any
comments or suggestions to add, please drop us a comment in the box below. In
the meantime, stay safe, stay well, keep planning your motorhome breakout for
when lock down is lifted and remember, when you finally get out and about, ‘take
care out there’.
Steve and Maggie
References
https://www.hortoncommon.co.uk/?s=leisure+batteries
PS: we have subsequently found this excellent and informative website below which gives a huge amount of information about batteries and also solar panels. Its worth a read at
http://www.aandncaravanservices.co.uk/how-does-a-battery-work.php Also read:
http://www.aandncaravanservices.co.uk/battery-technology.php
Comments
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Hi, we always look forward to hearing your comments, tips and thoughts. Drop us a line or two below. Take care now. Steve and Maggie