G' day to all. I have a coach built camper running one 75Ah starter
battery and one 85Ah leisure battery both under the hood and standard
fit. I should like to connect two sealed 110Ah batteries fitted one on
drivers step and one on passengers step as backup power for when we
are not on mains. The question is how should these be charged? They
say you should only charge batteries of the same capacity at the same
time so I guess that means I shouldn't just extend the cable from my
current leisure battery supply so what should one do?

I emailed Sterling and they replied "Look at our battery to battery
charger 12 v 50 amp  unit, this will charge them about 5 times faster
and put 2 x more useful power into them" but no explanations as to the
conclusion!

I could of course just keep the two 110Ah batteries isolated from the
engine system and just charge them when on mains but this would seem a
waste and I would also need some way of ensuring I don't drain them
too much in use.

Bit long winded but generally what do you guys do and how much success
have you had with your systems?

TIA.

On Sat, 20 Sep 2008 16:58:15 +0100, Colin 
wrote:

>G' day to all. I have a coach built camper running one 75Ah starter
>battery and one 85Ah leisure battery both under the hood and standard
>fit. I should like to connect two sealed 110Ah batteries fitted one on
>drivers step and one on passengers step as backup power for when we
>are not on mains. The question is how should these be charged? They
>say you should only charge batteries of the same capacity at the same
>time so I guess that means I shouldn't just extend the cable from my
>current leisure battery supply so what should one do?
>
>I emailed Sterling and they replied "Look at our battery to battery
>charger 12 v 50 amp  unit, this will charge them about 5 times faster
>and put 2 x more useful power into them" but no explanations as to the
>conclusion!

PS: This is a rapid charge system and in danger of cooking batteries I
suspect which is why they say only use on standard lead acid batteries
NOT sealed etc!

Colin expressed precisely :

> I could of course just keep the two 110Ah batteries isolated from the
> engine system and just charge them when on mains but this would seem a
> waste and I would also need some way of ensuring I don't drain them
> too much in use.
>
> Bit long winded but generally what do you guys do and how much success
> have you had with your systems?

You could install a four position switch between the already installed 
leisure battery, in an accessible position whilst on the road. This 
then switches the charge (and discharge) between the three batteries 
and also allows an 'all isolated' position.

Another way would be to add two more charge relays, one for each extra 
battery. Then just add he switch so it switches the domestic load 
between the three batteries. This same switch would need to be used to 
allow the mains charger to charge up each of the three batteries in 
turn, when on mains.

The wiring needs to be quite substantial - probably 4mm and with a 
30amp fuse at each battery as close as possible to the terminal.

-- 
Regards,
        Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

"Colin"  wrote in message 
news:0m4ad411oj93u0vhk4rg2vkgu825q41h5m@4ax.com...
> G' day to all. I have a coach built camper running one 75Ah starter
> battery and one 85Ah leisure battery both under the hood and standard
> fit. I should like to connect two sealed 110Ah batteries fitted one on
> drivers step and one on passengers step as backup power for when we
> are not on mains. The question is how should these be charged? They
> say you should only charge batteries of the same capacity at the same
> time so I guess that means I shouldn't just extend the cable from my
> current leisure battery supply so what should one do?
>
> I emailed Sterling and they replied "Look at our battery to battery
> charger 12 v 50 amp  unit, this will charge them about 5 times faster
> and put 2 x more useful power into them" but no explanations as to the
> conclusion!
>
> I could of course just keep the two 110Ah batteries isolated from the
> engine system and just charge them when on mains but this would seem a
> waste and I would also need some way of ensuring I don't drain them
> too much in use.
>
> Bit long winded but generally what do you guys do and how much success
> have you had with your systems?
>
> TIA.
>
>

Hi Colin

I would back up what Harry says, but the problem with potentionaly charging 
4 batteries with your Alternator, I am worried you will burn it out.
what is the output of the Alternator?
You don't say what the camper is, but I would look into adding another 
Alternator to just charge the leisure battery's, but could be a bit 
complicated !!

The only thing is as you say only use the same amperage if wired in 
parallel.

Hope that helps

metwo

On 20 Sep, 17:01, Colin  wrote:
> On Sat, 20 Sep 2008 16:58:15 +0100, Colin 
> wrote:
>
> >G' day to all. I have a coach built camper running one 75Ah starter
> >battery and one 85Ah leisure battery both under the hood and standard
> >fit. I should like to connect two sealed 110Ah batteries fitted one on
> >drivers step and one on passengers step as backup power for when we
> >are not on mains. The question is how should these be charged? They
> >say you should only charge batteries of the same capacity at the same
> >time so I guess that means I shouldn't just extend the cable from my
> >current leisure battery supply so what should one do?
>
> >I emailed Sterling and they replied "Look at our battery to battery
> >charger 12 v 50 amp  unit, this will charge them about 5 times faster
> >and put 2 x more useful power into them" but no explanations as to the
> >conclusion!
>
> PS: This is a rapid charge system and in danger of cooking batteries I
> suspect which is why they say only use on standard lead acid batteries
> NOT sealed etc!

You'll still need to get the power from somewhere. As others have said
your standard alternator may not be able to charge more than one or
two batteries at a time. Options for charging:

1. Alternator
2. Solar panel(s)
3. Portable petrol generator

Ideally a control circuit would switch different batteries to charge
and drain as needed for the leisure side while always keeping the
starter battery at good charge and only using it for starting.

I don't know of any such control system but try a Google search for
12v charge controller such as

  http://www.google.co.uk/search?hl=en&q=12v+charge+controller&btnG=Google+Search&meta=

seems to pull up some useful results. Maybe there's some help to be
had there....

--
James

James Harris wrote:
> On 20 Sep, 17:01, Colin  wrote:
>> On Sat, 20 Sep 2008 16:58:15 +0100, Colin 
>> wrote:
>>
>>> G' day to all. I have a coach built camper running one 75Ah starter
>>> battery and one 85Ah leisure battery both under the hood and standard
>>> fit. I should like to connect two sealed 110Ah batteries fitted one on
>>> drivers step and one on passengers step as backup power for when we
>>> are not on mains. The question is how should these be charged? They
>>> say you should only charge batteries of the same capacity at the same
>>> time so I guess that means I shouldn't just extend the cable from my
>>> current leisure battery supply so what should one do?
>>> I emailed Sterling and they replied "Look at our battery to battery
>>> charger 12 v 50 amp  unit, this will charge them about 5 times faster
>>> and put 2 x more useful power into them" but no explanations as to the
>>> conclusion!
>> PS: This is a rapid charge system and in danger of cooking batteries I
>> suspect which is why they say only use on standard lead acid batteries
>> NOT sealed etc!
> 
> You'll still need to get the power from somewhere. As others have said
> your standard alternator may not be able to charge more than one or
> two batteries at a time. Options for charging:
> 
> 1. Alternator
> 2. Solar panel(s)
> 3. Portable petrol generator
> 
> Ideally a control circuit would switch different batteries to charge
> and drain as needed for the leisure side while always keeping the
> starter battery at good charge and only using it for starting.
> 
> I don't know of any such control system but try a Google search for
> 12v charge controller such as

You might want to ask this question on alt.fan.landrover and/or on 
Landrover newsgroups as many people use split charging systems with 
winches for off-roading.

-- 
Paul -xxx  (mobile)

... stuff

METWO wrote on 20/09/2008 :
> Hi Colin
>
> I would back up what Harry says, but the problem with potentionaly charging 4 
> batteries with your Alternator, I am worried you will burn it out.
> what is the output of the Alternator?
> You don't say what the camper is, but I would look into adding another 
> Alternator to just charge the leisure battery's, but could be a bit 
> complicated !!
>
> The only thing is as you say only use the same amperage if wired in parallel.

The cable length and (relatively) small cable size would restrict the 
charge current to the batteries due to voltage drop. You need to use 
fairly large cable sizes - not for the current, but to avoid some of 
the voltage drop.

-- 
Regards,
        Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

"Colin"  wrote in message 
news:0m4ad411oj93u0vhk4rg2vkgu825q41h5m@4ax.com...
> G' day to all. I have a coach built camper running one 75Ah starter
> battery and one 85Ah leisure battery both under the hood and standard
> fit. I should like to connect two sealed 110Ah batteries fitted one on
> drivers step and one on passengers step as backup power for when we
> are not on mains. The question is how should these be charged? They
> say you should only charge batteries of the same capacity at the same
> time
No, you just need to ensure that when all the batts are connected together 
(ie when the split charge relay has closed) the charging device, alternator 
in your case, is capable of holding the voltage necessary to charge them. 
You'll only get probs with circulating currents if you wire different 
batteries in parallel with no charger connected.

> so I guess that means I shouldn't just extend the cable from my
> current leisure battery supply so what should one do?

Assuming they are identical Id keep the two 110ah batteries permanently 
wired in parallel.  Then, provided I was confident the alternator could keep 
the voltage of the whole lot above about 13v with everything switched on, 
I'd just use a conventional split charge relay for the combined 110ah batts. 
For a few quid more you could get a split charge diode which would ensure 
the 110ah batts dropped out of the circuit if the charging system voltage 
dropped, something like 
http://www.marcleleisure.co.uk/store/voltage-drop-split-charge-diode-p-426.html?cPath=24_46. 
You could then get in the realms of rewiring the existing charging cicuit 
for the firct leisure battery and replacing its split charge device with 
this one.

Much simpler, if it'll fit in the tray, is replace the 85ah batt with 
another identical to the 110s you're buying and just wire all three in 
parallel.  Your existing setup will then charge them all at once.

> I emailed Sterling and they replied "Look at our battery to battery
> charger 12 v 50 amp  unit, this will charge them about 5 times faster
> and put 2 x more useful power into them" but no explanations as to the
> conclusion!
>
You're better off talking to one of their tech guys rather than emailing.

Rgds

Andy R

On Sat, 20 Sep 2008 16:58:15 +0100, Colin 
wrote:

>G' day to all. I have a coach built camper running one 75Ah starter
>battery and one 85Ah leisure battery both under the hood and standard
>fit. I should like to connect two sealed 110Ah batteries fitted one on
>drivers step and one on passengers step as backup power for when we
>are not on mains. The question is how should these be charged? They
>say you should only charge batteries of the same capacity at the same
>time so I guess that means I shouldn't just extend the cable from my
>current leisure battery supply so what should one do?
>
>I emailed Sterling and they replied "Look at our battery to battery
>charger 12 v 50 amp  unit, this will charge them about 5 times faster
>and put 2 x more useful power into them" but no explanations as to the
>conclusion!
>
>I could of course just keep the two 110Ah batteries isolated from the
>engine system and just charge them when on mains but this would seem a
>waste and I would also need some way of ensuring I don't drain them
>too much in use.
>
>Bit long winded but generally what do you guys do and how much success
>have you had with your systems?
>
>TIA.
>

I just bunged in a ZIG unit and switch and then switch from Battery to
Battery when driving. Ive got 2 leisure batteries and it works fine
for us

On Sat, 20 Sep 2008 16:58:15 +0100, Colin 
wrote:

>G' day to all. I have a coach built camper running one 75Ah starter
>battery and one 85Ah leisure battery both under the hood and standard
>fit. I should like to connect two sealed 110Ah batteries fitted one on
>drivers step and one on passengers step as backup power for when we
>are not on mains. The question is how should these be charged? They
>say you should only charge batteries of the same capacity at the same
>time so I guess that means I shouldn't just extend the cable from my
>current leisure battery supply so what should one do?
>
>I emailed Sterling and they replied "Look at our battery to battery
>charger 12 v 50 amp  unit, this will charge them about 5 times faster
>and put 2 x more useful power into them" but no explanations as to the
>conclusion!
>
>I could of course just keep the two 110Ah batteries isolated from the
>engine system and just charge them when on mains but this would seem a
>waste and I would also need some way of ensuring I don't drain them
>too much in use.
>
>Bit long winded but generally what do you guys do and how much success
>have you had with your systems?
>
>TIA.
>
My Landrover has the normal feed to the caravan battery via the 12S
plug controlled by a split charge relay.  In addition to this I added
an 85Ah leisure battery to the vehicle and this is charged via a relay
controlled by a voltage sensing circuit so that the on-board leisure
battery is only connected in parallel to the starter battery when the
latter presents a terminal voltage above 13.8V.  This system works
very well for me as I use a 12v compressor fridge/freezer in the
Landrover.

However - your battery capacity is fairly high, and I would seriously
consider a second alternator with a modified charge controller to suit
sealed AGM or even Gel cell batteries.  If you are looking at charging
your pair of 110Ah batteries while stationary then consider a Kestrel
controller as used in narrowboats to maximise charging current where
engine revolutions are quite low.

HTH

Neil

(Reply via NG please)

Neil explained on 22/09/2008 :
>  In addition to this I added
> an 85Ah leisure battery to the vehicle and this is charged via a relay
> controlled by a voltage sensing circuit

Quite a good idea that voltage sensing type relay. Most can have their 
set point adjusted, so it should be possible to set it up for the 
second and third batteries to only charge when the voltage is quite 
high - high indicating a surplus of charge current.

-- 
Regards,
        Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Sun, 21 Sep 2008 08:16:20 +0100, "Andy R" 
wrote:

>
>"Colin"  wrote in message 
>news:0m4ad411oj93u0vhk4rg2vkgu825q41h5m@4ax.com...
>> G' day to all. I have a coach built camper running one 75Ah starter
>> battery and one 85Ah leisure battery both under the hood and standard
>> fit. I should like to connect two sealed 110Ah batteries fitted one on
>> drivers step and one on passengers step as backup power for when we
>> are not on mains. The question is how should these be charged? They
>> say you should only charge batteries of the same capacity at the same
>> time
>No, you just need to ensure that when all the batts are connected together 
>(ie when the split charge relay has closed) the charging device, alternator 
>in your case, is capable of holding the voltage necessary to charge them. 
>You'll only get probs with circulating currents if you wire different 
>batteries in parallel with no charger connected.

I actually heard what happens is that the smallest battery will drag
the other two down to roughly the same capacity as the smallest
battery, in this case 85Ah.

>> so I guess that means I shouldn't just extend the cable from my
>> current leisure battery supply so what should one do?
>
>Assuming they are identical Id keep the two 110ah batteries permanently 
>wired in parallel.  Then, provided I was confident the alternator could keep 
>the voltage of the whole lot above about 13v with everything switched on, 
>I'd just use a conventional split charge relay for the combined 110ah batts. 
>For a few quid more you could get a split charge diode which would ensure 
>the 110ah batts dropped out of the circuit if the charging system voltage 
>dropped, something like 
>http://www.marcleleisure.co.uk/store/voltage-drop-split-charge-diode-p-426.html?cPath=24_46. 
>You could then get in the realms of rewiring the existing charging cicuit 
>for the firct leisure battery and replacing its split charge device with 
>this one.
>
>Much simpler, if it'll fit in the tray, is replace the 85ah batt with 
>another identical to the 110s 

Not an option sadly.

>you're buying and just wire all three in 
>parallel.  Your existing setup will then charge them all at once.

Elsewhere someone has said it could overstress the alternator if I did
this? Having said that I think the easiest and simplest solution for
me would possibly be some kind of manual switch to divert the
alternator charge from the current 85Ah to the twin 110Ahs and vice
versa. And also do similar to the current camper mains charging unit
(Mine only appears to charge the leisure battery is this usual?) so
that any one time I am only charging one type of battery (the 2 x110s
or the 1x95)

Then I wouldn't need to worry about diodes & relays etc which to me is
just something else to go wrong.

The switching method has it's drawbacks of course with overheating
switches according to that url you gave. Anyone using a switch they
could recommend?

I currently check state of charge etc with a multi meter at differing
stages of our stay. Any sites on voltages we should not let our
batteries fall below?  I understand checking voltages with the onboard
meters is not very reliable anyway. Any reasonable alternative
monitors?

One final question if I may. I could put the twin 110Ah batteries in
the rear cupboard and vent it to outside but this would involve a lot
of cable, voltage drops etc.... The step on either side of my van is
ideal and fits like a glove but obviously this is inside the cab so
not ideal and the standard battery boxes don't fit so any ideas on a
box that would fit like a glove which I could the cover these and add
a vent to outside?

Thank you all thus far for your help in this & the other
responses. I like the KISS principle though.

On Sat, 20 Sep 2008 21:34:01 +0100, Harry Bloomfield
 wrote:

>METWO wrote on 20/09/2008 :
>> Hi Colin
>>
>> I would back up what Harry says, but the problem with potentionaly charging 4 
>> batteries with your Alternator, I am worried you will burn it out.
>> what is the output of the Alternator?
>> You don't say what the camper is, but I would look into adding another 
>> Alternator to just charge the leisure battery's, but could be a bit 
>> complicated !!
>>
>> The only thing is as you say only use the same amperage if wired in parallel.
>
>The cable length and (relatively) small cable size would restrict the 
>charge current to the batteries due to voltage drop. You need to use 
>fairly large cable sizes - not for the current, but to avoid some of 
>the voltage drop.

 Yes I was planning on using this 10mm stuff
http://tinyurl.com/3uj7nn

Although here http://www.fridge-and-solar.net/dual_bat.htm 
he recommends 13.5mm but that is hard to get hold of here and
difficult to use as it's so thick.

On Sat, 20 Sep 2008 20:04:00 +0100, "METWO" 
wrote:

>"Colin"  wrote in message 
>news:0m4ad411oj93u0vhk4rg2vkgu825q41h5m@4ax.com...
>> G' day to all. I have a coach built camper running one 75Ah starter
>> battery and one 85Ah leisure battery both under the hood and standard
>> fit. I should like to connect two sealed 110Ah batteries fitted one on
>> drivers step and one on passengers step as backup power for when we
>> are not on mains. The question is how should these be charged? They
>> say you should only charge batteries of the same capacity at the same
>> time so I guess that means I shouldn't just extend the cable from my
>> current leisure battery supply so what should one do?
>>
>> I emailed Sterling and they replied "Look at our battery to battery
>> charger 12 v 50 amp  unit, this will charge them about 5 times faster
>> and put 2 x more useful power into them" but no explanations as to the
>> conclusion!
>>
>> I could of course just keep the two 110Ah batteries isolated from the
>> engine system and just charge them when on mains but this would seem a
>> waste and I would also need some way of ensuring I don't drain them
>> too much in use.
>>
>> Bit long winded but generally what do you guys do and how much success
>> have you had with your systems?
>>
>> TIA.
>>
>>
>
>Hi Colin
>
>I would back up what Harry says, but the problem with potentionaly charging 
>4 batteries with your Alternator, I am worried you will burn it out.
>what is the output of the Alternator?

I think it's about 72Amh if memory serves me well (it hasn't for many
years)

>You don't say what the camper is,

I did didn't I? It's a coachbuilt based on a 1994 transit chassis
(Rimor)

> but I would look into adding another 
>Alternator to just charge the leisure battery's, but could be a bit 
>complicated !!

How on earth does one add another alternator. Not to the engine
surely?

On Sat, 20 Sep 2008 19:09:36 +0100, Harry Bloomfield
 wrote:

>Colin expressed precisely :
>
>> I could of course just keep the two 110Ah batteries isolated from the
>> engine system and just charge them when on mains but this would seem a
>> waste and I would also need some way of ensuring I don't drain them
>> too much in use.
>>
>> Bit long winded but generally what do you guys do and how much success
>> have you had with your systems?
>
>You could install a four position switch between the already installed 
>leisure battery, in an accessible position whilst on the road. This 
>then switches the charge (and discharge) between the three batteries 
>and also allows an 'all isolated' position.

Why four way? would it not be better to use the two 110 batts as one
then? I like the idea of an inboard isolator though. Mine has a
starter battery isolator under the hood which proved faulty anyway as
well as inconvenient as a safety feature. Why would it isolate the
starter battery anyway if not just a safety feature? Maybe it means
once the standard leisure battery had run down it could then run the
down the starter battery but my multimeter tests confirm they are
completely separate units anyway! ie onboard mains charger only
charges leisure battery. Though alternator does charge both on the
road.

>Another way would be to add two more charge relays, one for each extra 
>battery. Then just add he switch so it switches the domestic load 
>between the three batteries. 

Too much to go wrong.

 PS:

I seem to recall somewhere a device was available that beeps when
voltage drops to a set level. \this could be handy?

Colin used his keyboard to write :
> Why four way? would it not be better to use the two 110 batts as one
> then? 

If the four batteries are identical and all new, then fine you can do 
that.

> I like the idea of an inboard isolator though. Mine has a
> starter battery isolator under the hood which proved faulty anyway as
> well as inconvenient as a safety feature. 

A switch able to carry 500amp DC needs to be very substantial, most of 
these isolators are somewhat lacking. Current into and out of a leisure 
battery will be much more modest, say 30amp max.

> Maybe it means
> once the standard leisure battery had run down it could then run the
> down the starter battery but my multimeter tests confirm they are
> completely separate units anyway! 

The leisure battery should be charged via the charge relay, which 
serves two purposes...

1. It stops the leisure battery being used to start the engine.
2. It stops the starter battery being discharged by the domestic load.

> ie onboard mains charger only
> charges leisure battery. 

Correct

> Though alternator does charge both on the
> road.

Correct.

I managed to leave the lights on of my car last time I was away, 
flattening the cars battery. I simply ran a bit of thin two core flex 
across from the leisure battery, to the car battery which allowed the 
mains charger to put enough charge back in to start it, after a few 
hours.

-- 
Regards,
        Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

Colin brought next idea :
>  Yes I was planning on using this 10mm stuff
> http://tinyurl.com/3uj7nn
>
> Although here http://www.fridge-and-solar.net/dual_bat.htm
> he recommends 13.5mm but that is hard to get hold of here and
> difficult to use as it's so thick.

My charge system works pretty well, despite it being a car and caravan 
- which is much longer and involves plugs and sockets adding 
resistance. I ran a 4 or 6mm cable the length of the car. This feeds 
both the battery and keeps the fridge running. For your much shorter 
cable runs I would suggest 6mm ought to be ample.

You asked about adding a second alternator. All you need is a modern 
alternator - these have the charge controlling circuits built into 
them, then take your 6mm cable from it to the battery - not forgetting 
the earthing. The not so easy part is the mechanical fixing and drive 
belt.

Another way would be an upgraded alternator with more output, to 
replace the one you have.

-- 
Regards,
        Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

"Colin"  wrote in message 
news:0m4ad411oj93u0vhk4rg2vkgu825q41h5m@4ax.com...
> G' day to all. I have a coach built camper running one 75Ah starter
> battery and one 85Ah leisure battery both under the hood and standard
> fit. I should like to connect two sealed 110Ah batteries fitted one on
> drivers step and one on passengers step as backup power for when we
> are not on mains. The question is how should these be charged? They
> say you should only charge batteries of the same capacity at the same
> time so I guess that means I shouldn't just extend the cable from my
> current leisure battery supply so what should one do?
>
> I emailed Sterling and they replied "Look at our battery to battery
> charger 12 v 50 amp  unit, this will charge them about 5 times faster
> and put 2 x more useful power into them" but no explanations as to the
> conclusion!
>
> I could of course just keep the two 110Ah batteries isolated from the
> engine system and just charge them when on mains but this would seem a
> waste and I would also need some way of ensuring I don't drain them
> too much in use.
>
> Bit long winded but generally what do you guys do and how much success
> have you had with your systems?

I haver had the following arrangement for ten years with no problems. (The 
system is 24V but that makes no odds)
The three leisure batteries charge from the alternator via three relays. The 
relays have timers so the batteries are connected at 45 sec intervals after 
the engine is started. The batteries are of different capacities and some 
are old, some new, at any given time. A small diameter wire runs from the + 
terminal of each battery (via a 1A fuse at the battery) to a voltmeter on 
the dash. Each battery has a separate ammeter. Three separate 'intelligent' 
chargers (the 24V 15A ones used mostly for marine applications) operate 
automatically when external mains is available. All main battery feeds 
consist of  two parallel 4mm cables.

Bill

"Bill Wright"  wrote in message 
news:juudnaVFF9pzFkTV4p2dnAA@pipex.net...
> I haver had the following arrangement for ten years with no problems. (The 
> system is 24V but that makes no odds)
> The three leisure batteries charge from the alternator via three relays. 
> The relays have timers so the batteries are connected at 45 sec intervals 
> after the engine is started. The batteries are of different capacities and 
> some are old, some new, at any given time. A small diameter wire runs from 
> the + terminal of each battery (via a 1A fuse at the battery) to a 
> voltmeter on the dash. Each battery has a separate ammeter. Three separate 
> 'intelligent' chargers (the 24V 15A ones used mostly for marine 
> applications) operate automatically when external mains is available. All 
> main battery feeds consist of  two parallel 4mm cables.

PS:
1. That should read 'two parallel 6mm cables'.
2. You can't really damage an alternator as long as you don't repeatedly ask 
it for maximum load for a protracted time. The alternator has an internal 
current limit.
3. Batteries of unequal capacities do not present a problem. Batteries that 
are discharged to different degrees when charging starts do not present a 
problem either. Assuming no batteries are in very poor condition, the 
batteries that are most heavily discharged simply take more charge until the 
terminal voltages of all batteries are equal.The alternator voltage will 
always be above any battery voltage, so everything is going to get charged 
to a greater or lesser extent.
4. All batteries should have fuses at the pos terminal. These should be 
sized to be just adequate for the highest load that will be imposed, or the 
highest charge current that will be applied. I have 30A fuses at the 
batteries (24V remember).
5. It's wise to have a big-ass fuse on the feed from the alternator to the 
relays. I have a 60A one.
6. I have an isolating relay on the vehicle battery, so it can't be 
accidentally discharged when parked. Obviously the starter motor feed 
bypasses this fuse.

Bill

On Tue, 23 Sep 2008 19:32:47 +0100, Harry Bloomfield
 wrote:

>Colin used his keyboard to write :
>> Why four way? would it not be better to use the two 110 batts as one
>> then? 
>
>If the four batteries are identical and all new, then fine you can do 
>that.

I plan on using two 110s in parallel is that not better than two
single 110s?

>> I like the idea of an inboard isolator though. Mine has a
>> starter battery isolator under the hood which proved faulty anyway as
>> well as inconvenient as a safety feature. 
>
>A switch able to carry 500amp DC needs to be very substantial, most of 
>these isolators are somewhat lacking. Current into and out of a leisure 
>battery will be much more modest, say 30amp max.

Where do you get 500 amps from?

Colin has brought this to us :
> On Tue, 23 Sep 2008 19:32:47 +0100, Harry Bloomfield
>  wrote:
>
>> Colin used his keyboard to write :
>>> Why four way? would it not be better to use the two 110 batts as one
>>> then? 
>> 
>> If the four batteries are identical and all new, then fine you can do 
>> that.
>
> I plan on using two 110s in parallel is that not better than two
> single 110s?

As two single connected batteries, there is scope for the future for 
one to deteriorate and perhaps fail. It alone could then be replaced 
rather than both needing to be replaced to retain the match.

>> A switch able to carry 500amp DC needs to be very substantial, most of 
>> these isolators are somewhat lacking. Current into and out of a leisure 
>> battery will be much more modest, say 30amp max.
>
> Where do you get 500 amps from?

The likely maximum cold cranking current needed to turn the engine 
over. Check the CCC spec printed on your starter battery.

-- 
Regards,
        Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

On Mon, 22 Sep 2008 18:31:26 +0100, Harry Bloomfield
 wrote:

>Neil explained on 22/09/2008 :
>>  In addition to this I added
>> an 85Ah leisure battery to the vehicle and this is charged via a relay
>> controlled by a voltage sensing circuit
>
>Quite a good idea that voltage sensing type relay. Most can have their 
>set point adjusted, so it should be possible to set it up for the 
>second and third batteries to only charge when the voltage is quite 
>high - high indicating a surplus of charge current.

The one I fitted isn't adjustable, it's a sealed unit and very
stable(supplied by Tony Maris actually), but I do have another lying
around somewhere that is!  Chaining several to connect different
batteries at different times might be problematic, as each switch will
have a certain amount of hysteresis in it's operation, which could
leave unpredictable interconnections upon removal of alternator
voltage.  Only one of my batteries is on a voltage sensed connection,
the caravan split charge is ignition controlled as normal thus
ignition off - no connection.

Neil

(Reply via NG please)

On Sat, 20 Sep 2008 16:58:15 +0100, Colin 
wrote:

>G' day to all. I have a coach built camper running one 75Ah starter
>battery and one 85Ah leisure battery both under the hood and standard
>fit. I should like to connect two sealed 110Ah batteries fitted one on
>drivers step and one on passengers step as backup power for when we
>are not on mains. The question is how should these be charged? They
>say you should only charge batteries of the same capacity at the same
>time so I guess that means I shouldn't just extend the cable from my
>current leisure battery supply so what should one do?
>
>I emailed Sterling and they replied "Look at our battery to battery
>charger 12 v 50 amp  unit, this will charge them about 5 times faster
>and put 2 x more useful power into them" but no explanations as to the
>conclusion!

They don't like people asking questions. I suppose it's in case they
get caught out selling unnecessary products. Most of us can get by
with basic solutions.

>I could of course just keep the two 110Ah batteries isolated from the
>engine system and just charge them when on mains but this would seem a
>waste and I would also need some way of ensuring I don't drain them
>too much in use.

Your current alternator could never keep up with them anyway unless
you were driving for days. Keep them separate and charge using a half
decent automatic charger when on site, like the Halfords one at about
£38. We have ours for years with no trouble.

>Bit long winded but generally what do you guys do and how much success
>have you had with your systems?
>
>TIA.
>

dont waste your time with the likes of sterling
http://www.sterling-power.com/
 or smartguard
http://www.smartgauge.co.uk/
Sterling way overcomplicate things to justify the overpriced products.
Smartguard just don't have a clue technically speaking as most of
their information is copied from elsewhere and their products are no
better than standard caravan gauges. At least one case of a boat being
damaged by fire with their useless smartbank bullshit and duff advice.

Try to hang on to your money by avoiding greasy snake oil salepeople.
Remember the price of their crap means you could have bought four or
five new batteries!!!!!!!!

Great site for learning here
http://www.fridge-and-solar.net/index.htm
** Posted from http://www.teranews.com **

On Tue, 30 Sep 2008 12:43:04 +0100, Alan <alanLN@netcom.nospam> wrote:

>On Sat, 20 Sep 2008 16:58:15 +0100, Colin 
>wrote:
>
>>G' day to all. I have a coach built camper running one 75Ah starter
>>battery and one 85Ah leisure battery both under the hood and standard
>>fit. I should like to connect two sealed 110Ah batteries fitted one on
>>drivers step and one on passengers step as backup power for when we
>>are not on mains. The question is how should these be charged? They
>>say you should only charge batteries of the same capacity at the same
>>time so I guess that means I shouldn't just extend the cable from my
>>current leisure battery supply so what should one do?
>>
>>I emailed Sterling and they replied "Look at our battery to battery
>>charger 12 v 50 amp  unit, this will charge them about 5 times faster
>>and put 2 x more useful power into them" but no explanations as to the
>>conclusion!
>
>They don't like people asking questions. I suppose it's in case they
>get caught out selling unnecessary products. Most of us can get by
>with basic solutions.
>
>>I could of course just keep the two 110Ah batteries isolated from the
>>engine system and just charge them when on mains but this would seem a
>>waste and I would also need some way of ensuring I don't drain them
>>too much in use.
>
>Your current alternator could never keep up with them anyway unless
>you were driving for days. Keep them separate and charge using a half
>decent automatic charger when on site, like the Halfords one at about
>£38. We have ours for years with no trouble.
>
>>Bit long winded but generally what do you guys do and how much success
>>have you had with your systems?
>>
>>TIA.
>>
>
>dont waste your time with the likes of sterling
>http://www.sterling-power.com/
> or smartguard
>http://www.smartgauge.co.uk/
>Sterling way overcomplicate things to justify the overpriced products.
>Smartguard just don't have a clue technically speaking as most of
>their information is copied from elsewhere and their products are no
>better than standard caravan gauges. At least one case of a boat being
>damaged by fire with their useless smartbank bullshit and duff advice.
>
>Try to hang on to your money by avoiding greasy snake oil salepeople.
>Remember the price of their crap means you could have bought four or
>five new batteries!!!!!!!!

Does make you wonder how we ever got by without these people in the
past. Some of their ideas are no doubt sound but the prices certainly
aint.

>Great site for learning here
>http://www.fridge-and-solar.net/index.htm
>** Posted from http://www.teranews.com **

Lovely website, shame he no longer maintains it. He done well though.

Thanks.

Don't run your batteries in parallel, just connect up a split charge
arrangement to each one. Supplement this with a mains charger if
needed. Arrange the leisure load to be switchable from any battery and
feed the mains charger into the load side of your selector
arrangement. Your battery selector could be a 4 way switch or a
combination of individual switches.
I am including the vehicle's own battery in the list to allow you to
charge it from the charger should it ever be needed.
The vehicle alternator will be quite OK without any problem.

John