Second leisure battery

Had a look round a potential new van and Would like to fit a second leisure battery.  Has anybody done this in a Symbol c2008-11?  If so, where did you put the battery?  It was easy in my 2002 Symbol - one under each seat.
Thanks

Hi am interested in doing the same but am unsure about connecting the two together and issues around battery types, ages and capacities as well as my solar charger link.

(I’ve asked about this on another post re issues with my heater draining the battery)

Rob

I have recently fitted a second battery in my 2014 Warwick Duo and put it under the pasanger seat , but if you have a swivel as I have you will need to fit a low hight battery (190 mm o/a hight) . I  used 10 mm wires under the AS cab carpet where the carpet from the upstand finish with the rubber original cab matting,fuse t each end with midi fuses and 30 amp fuses on the + cable, you will have to cut the matting away for the battery tray and level the floor to take out slope , I had a metal battery tray made just larger than the battery and about 60 mm high . Be very careful cutting the rubber matting under the seat as wiring looms pass under the matting. My existing leisure was about 6 months old and I checked with a very good auto electrical firm and Tynna batteries concerning and they said as long as both batteries are of a similar size and both flooded lead acid they would be fine . Checked with Mark at AS as I have a solar panel an makes no difference . All is fine and no problems.

Thanks.  That's really helpful.  I haven't actually bought the van yet but this will help me to negotiate with the dealer.

Have a look below on the link for unbiased professional and very experienced battery information. These people are very well respected by the motor home industry and specialise in battery technology and detailed examination of failed batteries.   Both batteries should be of the same age, amp hrs, manufacturer, type, in fact the same batteries if you want the best results for your money. I would also check the capacity of the inbuilt charger used when plugged into the mains as you will be asking it to do twice the work which it is not designed to do. But you have to wonder how long the existing battery has been sat around before being fitted to the van and how long the van has been sat around with that battery in it. If your new battery is bought at a suppliers with a quick turn over then the age of the two "matched batteries could be a difference of three years or more. If you don't want to have an imbalance between batteries then buy two together of the same make type etc. The Varta LDF90 is a good multi purpose battery made by one of the biggest battery manufactures, Johnson Controls and is only 190 mm in height. The Yausa L36 EBF is a relative newcomer but reports from A&N caravans are very good. I had a 1999 Symbol and manage ok with one of the Varta units at 90 amp hr with a 100 watt solar panel and a voltronic MPPT controller. I have a similar set up now on my A/S Montana which I will admit has more room on the roof for solar panels than the Symbol. If a job is worth doing its worth doing well and that can cost. One thing I would'nt do is let a auto electrician that has no experience with motorhome or campervans anywhere near it without specific recommendations on the subject.  [You must be registered and logged in to see this link.]

roan wrote:My existing leisure was about 6 months old and I checked with a very good auto electrical firm and Tynna batteries concerning and they said as long as both batteries are of a similar size and both flooded lead acid they would be fine

Sound advice, the batteries certainly don't have to be identical but I suggest that a difference of 30AH between capacities would be a maximum difference. If your existing battery is 3 years old or less and has never failed then I wouldn't feel the need to replace it when installing the second.

At least once a year, disconnect both batteries and make sure they are both holding their charge independently as, in parallel battery installations, one battery can use much of its energy supporting a failed partner.

RE the location of the Hab battery mine (a 2012) was under the long bench seat on the front right as you walk in. I simply put one in the very large space to the left of it at the back in a battery box which was fixed in place with straps. fairly easy job but did buy 2 new batteries (Varta) as the one which came with the van was only 85amp and I wanted two 110amp as I had no Solar.
If you do have a solar why not see what size you have and look to put in a decent large amp or indeed if you only go on sites with hook up you don't need it
David

So did you fit two 110amp batteries I only ask as that would make a big upgrade to 220 amphrs.  So that would need a charger of 20amps.  The rule being, the charger will support a battery bank 10 times it max output. So a 22 amp charger will support a battery bank of 220amp hrs   That’s in an ideal world with new batteries and not including a starter battery. So A and N would have us use a 5 times rule in the real world . That would mean a charger with an output of 45amps! Have read of this link, very informative. ://www.aandncaravanservices.co.uk/how-does-a-charger-work.php

Hi Biffo
Yes I did fit two batteries and the inbuilt charger did seem to cope very well, (I did have a word with a Auto Electricial mate first who said it would) 
I fitted two to cope with when mostly we went on the Warners motorhome show for 5 days. I also installed inline voltmeters which although not perfect gave some indication of their state and even after the 5 days they showed well into mid 12v range. by the time I had done the drive back home almost fully charged again so very little for the charger to do.
I did not have a solar panel and my new van comes with two 100a batteries as standard and a solar panel so not expecting any trouble.
If you are in the sunshine don't expect you would have any trouble if you have converted all your lights to LED
David

Voltmeters are so cheap I would fit one on each battery. While the batteries are both connected they should be indicating the same value so check the displays agree all the time.

Then if you disconnect them from each other and let them rest for a day check they still agree. A suspect battery will sag down more than a good one. The differences are small which is why they need to follow each other well.

The inertia weight of a battery even in a small shunt will be huge so restraining the battery securely is vital. A 100Ah battery is roughly 25KG so if it suffers a 4G crash (small) it becomes 100KG for a split second.

Hi

biffobear wrote: Have read of this link, very informative. [You must be registered and logged in to see this link.]

Very informative but WRONG!  

I never thought I’d find myself defending smart chargers but:

Despite their statement that motor home chargers work on timers, every motor home charger I’ve seen is either a constant voltage (like the old Zig) or a smart charger.

A smart charger will charge at the same current throughout the charge cycle regardless of the battery capacity (it has no defined output voltage at start of charge as stated). If you charge two batteries in parallel the current will split according to the capacity of each battery. Yes it will take longer but only roughly in proportion to the change in capacity. It will only switch to voltage when the battery is almost fully charged.

Generally there is no upper limit for a smart charger although a charger not designed for motor homes may have an extra  stage to detect a faulty battery. Such a unit may detect a large capacity as faulty.

I’ve no experience of the Schaudt EBL 100 that they give as an example but it looks like a good piece of kit. I would be amazed it it worked in the way they say, that would make it “not fit for purpose” in my view.

I have emailed Schaudt’s technical department in Germany and asked them to comment. I’ll report back when I get a reply.

Brod

Brod is so right about the information at the link being wrong. The author has produced a lot of evidence but made wrong conclusions and obviously has no experience of operating high capacity battery banks.

My main criticism of C-Tek is they overstate the capacity of battery it is suitable for, claiming a 5A unit is good for up to 160Ah. A battery of that capacity would need 8A at least to be appropriate for all circumstances.

Hi  

HairyFool wrote:My main criticism of C-Tek is they overstate the capacity of battery it is suitable for, claiming a 5A unit is good for up to 160Ah. A battery of that capacity would need 8A at least to be appropriate for all circumstances.

Horses for courses.

To be fair they only give 160Ah for maintenance (i.e. maintaining a reasonably well charged battery). They do however quote 110 Ah at 22 hours to 80% and that charging time may be acceptable to some.

The only reason why it may not charge a 160Ah battery from flat (assuming the user can wait that long) is that it has timeouts on each stage.

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Peter Brown wrote:The author has produced a lot of evidence but made wrong conclusions and obviously has no experience of operating high capacity battery banks.

Not sure about the “high capacity” bit though. It sounds as though they may be just measuring the terminal voltage while the charger is in the current phase;  the results of which are pretty meaningless on any capacity battery apart from giving you a very rough idea of the state of charge at that time.

Brod.

Hi  


I have had a reply from Schaudt. They seem an on the ball company, I was impressed by the quick reply, and they confirm that the A and N assessment of how their equipment works is incorrect.

From the A and N Caravans website (about the Schaudt Electrobloc EBL 100):

 “These EBL 18amp units start off charging a battery at 14.3v for a set timer period, such as 4 hours for a 'Wet Acid' battery. After 4 hours the charger drops to a slow charge 'Float/Trickle' rate of 13.8v, regardless of whether the battery is fully charged or not.”


I looked at the Electroblock manual and it seemed a well-designed bit of kit and specified the IUoU charging curve, this is the standard DIN charging standard used by just about all smart chargers supplied in Europe (and beyond). In order to clarify I contacted the manufacturer’s technical department.

Here are my questions and the replies from Udo Lang of Schaudt GmbH Technical (the manufacturers) in Germany

Question 1
From the Electrobloc EBL 100 manual (SDT-0004-01EN)
“Suitable batteries 6-cell lead acid or lead gel batteries of at least 55 Ah”
The manual does not state a maximum Ah battery capacity. Is there a maximum recommended battery capacity and if so what is it?

Reply:
“The EBL is good for about 180…200Ah. When the battery is bigger than this, it will just take longer to charge. When the reaction is to change after 4 hours into float charging the charger is defect.”

So it works like any other smart charger If a unit switches to float after 4 hours as claimed the unit is faulty. There is no maximum battery capacity.


Question 2
Can you confirm the existence of the timer and at what point in the charging cycle it starts?

Reply
“Yes - but first the battery should be charged completely up to 14,3V. With battery selection switch in position lead acid the period in which the EBL keeps the 14.3V with some mA will be about 4 hours after the battery has reached 14,3V and the current is down to nearly zero”.

So, this clarifies the four-hour bit. It doesn’t switch to float after 4 hours whether “the battery is charged or not”. It goes through the standard smart charge cycle and switches to float 4 hours after the charge is completed - a very different scenario.

Question 3

There were actually three questions, the 3rd was about the burnt connectors but I think there was language barrier problem. and I don’t think they understood my question because they just advised that I buy a new one.


As for why the unit on the burnt I can’t say but I think it extremely unlikely it was to do with the high battery capacity. If you connect more than one battery the charger works at the same current. It is not overloaded, the current is simply shared between the batteries.

Brod

Peter Brown writes -
"Brod is so right about the information at the link being wrong. The author has produced a lot of evidence but made wrong conclusions and obviously has no experience of operating high capacity battery banks".  



For your information we have been fixing and servicing Caravans and Motorhomes since 2011. 
When I say 'Servicing' that included rebuilding gearboxes and Engines as well as the usual habitation side. 
When I use the term "rebuilding" these major components, I mean stripping right down to 'Crank Out', regrind, new bearings, etc. Not just the usual Fiat route of sticking in a new unit from the line.  

We specialise in repairing all Charger/Controllers from around the world from Italy, America, Germany, Holland, France, Britain, etc.
To better understand the Alternator and mains charger failures we were seeing, we spent a lot of time in 2012/13 cutting open hundreds of batteries we removed from vehicles. Trying to work out why some batteries regularly caused carnage and others behaved well. 
This has given us an insight into real world battery chemistry. Not just the new/laboratory theory, but real usage of how they behave at 2 years plus - Degradation, Full Failure, Build quality, Construction, Technology, etc. like no one else.
   

We fixed failures on motorhomes with big battery banks and single banks. We rebuilt Alternator and Starter Motors and did Solar. 

So we do have quite a bit of experience working on large capacity battery banks as it was this 'breed' of motorhome that tended to suffer more from Alternator failure. Often at less than 30,000 miles when a Truck alternator would cover 250,000 miles using a smaller capacity Alternator. 
That suggested an anomaly, and it was us that designed an electronic Alternator Heat Tag that recorded peak temperatures that showed how close a motorhome Alternator runs near to it's limits when fitted with a just a twin battery bank. We would remove these Tags when the vehicle came back in for a service and extract the data.

We were the first to warn of overloading Alternators, when they had previously been regarded as an 'unlimited' current source, when their capacity was finite.

Bosch must have seen the same issue elsewhere because subsequent to our work, in late 2015, they  brought out a new Alternator that has heat sensing built in. This Alternator backs down the charge when the Alternator temperature exceeds set limits.

So given the above as an example of the level of 'detail' and depth we go to ensure we deliver a good product, wouldn't it seem odd for us to be able to repair a charger, after reverse engineering the circuitry, and then not bother to find out how it operates? 
Surely before you even look at a blown up charger you need to understand how it functions and what it is designed to do?
How would anyone hope to repair a CBE CB5XX charger if you didn't know it was the only mainstream charger range than actually powers down after 10 hours at 13.6v Float? 
How we would even manage to get away with repairing two let alone the thousands repaired or rebuilt if we sent them out faulty?
   

In an earlier post you write -
"Sound advice, the batteries certainly don't have to be identical but I suggest that a difference of 30AH between capacities would be a maximum difference. If your existing battery is 3 years old or less and has never failed then I wouldn't feel the need to replace it when installing the second.

At least once a year, disconnect both batteries and make sure they are both holding their charge independently as, in parallel battery installations, one battery can use much of its energy supporting a failed partner."


Sorry, but wrong again.
Electrical flow around batteries is all about resistance and 'ease of flow'.
When electricity has a choice of multiple paths, it always takes the easy one. No matter if the other path is only a teeny weeny bit more difficult, it will choose the easy path.
So if you have two batteries wired up and the path of one has a slightly higher resistance than the other, which battery will the magic electrical mites come from?

If you have two batteries and one is a different size, or has 3 months worth of internal corrosion or has wiring that is a longer/thinner cable or a less efficient technology, etc. which one will get more of the charging systems current?

A battery bigger than another will have a different resistance, as will a 3 month old one against a new one.
Unless you balance them EXACTLY one battery will work harder than the other. This won't just result in lost battery lifetime but can impact the Capacity of the battery bank, with it being a lot less than the owner realises.

If the batteries are the same age, same technology, same size, same manufacturer, etc. they will be used and charged equally. Alpha Batteries are the only retailer we know of that understand this and the only ones that guarantee to send out matched batteries, from the same batch, when more than one is ordered.

I am guessing from your second paragraph that you have significant experience of one battery failing before the other, maybe this has been a result of your adopted flawed practises? 

In our experience, if wiring batteries in parallel is done correctly they both work/expire equally.

If they are not balanced, then the batteries work against each other resulting in even the newer one having half the usual life, so it is false economy to not start with a properly configured balanced battery bank.




Brod, It is interesting to read your email from Udo and your interpretation of what he is trying to say.
I have known Udo since 2011 and like the guy very much. While his English is very good, his translation of what he knows into English is sometimes difficult to read. Just as you note in your text, " I think there was language barrier problem" with question 3.

I would suggest it reads like there is a language problem with all three questions.
If the Elektroblock EBL charging modules works as per your interpretation of what Udo is/isn't saying, then what is the point of having a Timer?

The CTEK XS7.0 has an 8 hour timer for the same charging stage as the Schaudt, are you saying that Timer does not have any impact either and is a waste of space in the CTEK manual? 

Have a look at the CTEK manual near the bottom of the 'How does a charger work' web page 



I love your 'review' of the CTEK  charger's capability when replying to HairyFool -
"The only reason why it may not charge a 160Ah battery from flat is that it has timeouts on each stage".

Doesn't that mean that you you now accept Timers exist, and actually think the CTEK Timers significantly affect the way the charger works with a big battery?
Aren't you saying that when a charger is matched with a overlarge battery bank that is incompatible with the timers, the charger can become ineffective?


Sounds like you are not only accepting that Timers are used but are also suggesting every charger has a practical  limit on the size of the battery bank it can efficiently support? 
Well I never. 

It is an interesting interpretation, but I think I side with HairyFool that the documentation overstates the CTEK's capability as we don't rate them other than overpriced under performers. 


One of your other quotes sums up the CTEK range really well, you write -  
"They do however quote 110 Ah at 22 hours to 80% and that charging time may be acceptable to some".

Isn't that interesting that they quote the charging time to 80% and not fully charged?
Isn't that a bit like requesting your Bank Balance and the bank saying "80% of your Balance is £93.10"??
How about asking the Audi Dealer what size the fuel tank is, "It's 80% size is 43.6 litres", he replies.

Nobody wants anything quoted as an "80%" figure, that bonkers, they want the 100% figure. To know how long it takes to charge to 100%, so why quote 80%?? 

Could it be the CTEK's can't actually get a big Leisure battery to 100%, or if it can they don't want to have to quote it in the weeks it takes?

The C-Tek manual states the bulk phase is max 20 hours @ 5A thus IF 100% efficient (never) can only charge a 100Ah battery from truly flat although they should never be totally flat

It then defines the absorption phase as 5 hours max but what happens between the two? What happens if the battery is not fully charged at the end of the 20 hours? The charger cannot reduce the current yet maintain the voltage as indicated in the graph. 

The transition between the two stages is defined by when the BATTERY starts to absorb less current, all the charger can do for that total of 25 hours is supply up to 5A allowing the terminal voltage to rise to a threshold of 14.4 Volts so what happens if the battery is still not fully charged at the end of 25 hours? 

The end of the absorption phase is defined by when the BATTERY charge current falls to a steady value (what tolerance is "steady") such that the energy going in (current) is equalled by the energy coming out (heat?). "Smart" charging keeps the period in this final stage to a minimum. I think if it gets to 25 hours without getting that low steady current it should restart charging and of course then the second time around it may well achieve full charge.

Going back to the Soft start phase this is also nonsensical. Soft Start is 5A, Bulk is 5A so what is supposed to happen at 12.6V? What is the kink in the Voltage line at the transition point and why the step in the current, the table says they are both at the same current. Soft start is probably a good idea but if you take a rested battery that is partially discharged and connect it to a dumb charger it "soft starts" itself. At switch on the current will start at a nominal rate then after a short time it then rises to the charging rate once the electrochemical reaction is fully established. Once again the BATTERY defines charge current so what is the charger doing?

Finally the float phase is meaningless. Any normal battery up to 160A that takes 5A to maintain float is in trouble but there are far too many variables to define what it should be (battery size, age, temperature, technology). The charger if truly smart could know within reason what is a valid float current as a function of the charging phase.

A rather lengthy first quote from AllaFEvans, it would have been nice if he'd posted an introduction to himself [You must be registered and logged in to see this link.] so we knew who he was.

I'm not going to respond in detail but I do have an additional 41 years professional experience operating lead acid cell batteries and I was paid enough for my knowledge to be able to buy new Auto-sleeper motorhomes.

As I've said many times on this forum, most readers aren't tuned in to the finer points of technical theories, they would just like sound practical and economic advice from those who have been there before.

You start a thread asking if anyone has fitted a second battery and by the end of the thread you need a degree in electrical engineering.

Peter, Apologies, I thought my lengthy introduction on who we are covered it, sorry.



HairyFool, Excellent questions and observations. You are obviously well clued up and want to know the real world technical operation, not the theory, so I will try and cover that.

As you observe, most 'Smart' chargers are not.  

I won't reply in relation to the CTEK's as they are not relevant to Motorhome Leisure use anyway. In anycase there are so many models and variations it wouldn't be easy to cover them all.

Secondly extremely few mainstream motorhome manufacturers fit Smart chargers, most fit either fixed 13.8 voltage Power Supply/Chargers or multi stage chargers, which are obviously different to a smart charger.
The Sargent PX300 3 stage unit is probably the only British one with an O'level, but that is in Art, so even that can't really be placed in the Smart category.

Almost all advice from anywhere you will find, says to keep the Leisure battery fully charged when possible. Not to discharge below 50% Depth Of Discharge (DOD) as the ideal compromise between lifetime and usability.

The Bulk phase or first stage of a charger is not there to charge the battery fully, it's there to 'wake it up'.
Most Leisure battery charging will often 'skip through' the first phase quite quickly unless the battery has been over discharged. 
The Bulk phase on a CTEK, is there to cope with a 100% DOD, 'pancake flat' car battery. 
This First/Bulk phase will usually charge the battery at max current and around 14.3v until the voltage at the battery reaches 14.3v 
Once this is achieved, which on a typical Leisure battery can take just 5 minutes, it switches to the MAIN event which is usually the second stage where the 'Fast' charging is done. 
Don't confuse a voltage of 14.3v at the battery terminals with the battery being at the same voltage, it isn't. 
The battery SOC voltage will still be at 12.4v, or whatever. 
These stage voltages are about the charger voltage, so the voltage at the battery, not the actual battery voltage. 

In this second stage the current is not 'pumped' into the battery (as most people believe), but dictated by what the battery will pull. 
It is the battery that decides how much current is drawn, not a Leisure battery charger. Remember we are talking about motorhome chargers, not Automotive.


In this second 'boost' stage a constant 14.3v (I use this as a typical voltage not exact) is applied with decreasing current.
CTEK call it the Absorption Phase.
Although the voltage is fixed at 14.3v, the current reduces as the battery charges up, until it is drawing about an amp or two.

In the CBE CB516 charger this phase has no timer at all, the phase will run forever or until the current being pulled by the battery drops below a set level (around 1 amp).
Obviously if the battery is no longer drawing much current, then the charger can safely assume it is 'full' and switch to the next phase. 
Many Car battery chargers use this same trigger to switch to the next stage.

The problem is not all batteries will be perfect. Some will never drop below a 1 amp draw because of an internal fault or because the battery bank is so big that a 0.8amp draw from each of 4 batteries amounts to nearly 4 amps and way more the chargers 'fully charged' switch point. 
Therefore the charger continues at 14.3v 'Fast charge' mode when it isn't wanted. 
The battery then overcharges, warms up, starts to gas and in some circumstances can eventually explode as it gets so hot. 
A big, new battery bank will just degrade internally, lose capacity rather than explode. You can see why a big battery bank doesn't work on a CBE CB516 style charger without Timers?  Go above two batteries on a CB5xxx and need to be 'hawkeyed' when charging. 
 
If you are lucky the strain on the charger will cause it to fail before the battery throws acid and bits of casing all around the van. And yes we regularly see exploded batteries to prove the point, three reported on the MMM forum in one week by various owners and we think exploding batteries will be heard of more next year.

Schaudt put a Timer on this phase, as do the best manufacturers, forcing the charger into a far less destructive mode if the battery is less than ideal, even if it isn't charged fully.

The Schaudt charger models were revised about 2006 and again in 2011 and although the Timer intervals were increased each time they didn't really keep pace with the way motorhomes were being used and modified. The 2011 on Schaudt EBL's have up to an 8 hour timer, but an early 2005 unit can have just one hour.

So while the short Timers on a Motorhome charger might be a pain, they are there for safety. Many Car style chargers have no safety timer at all, which is why the instructions will tell you not to leave it unattended for even a short time.
The CBE CB516 charger is definitely not one to leave on long term EHU.

The 'Smart' CTEK has timers, forcing it onto the next stage. 
However, the final stages do 'tests' on the battery and if the battery has a fault that causes the voltage to drop, it starts the entire cycle from the very beginning so it can have another go at exploding the battery.
It wouldn't give it an A'level, well maybe a minor pass in Art as it does look quite good.

Soft Start is relevant to the CTEK's design role of bringing up Car Starter batteries from totally flat, as any battery discharged so low is almost certain to have suffered damage. Like potentially shorted, sulphated cells. 
If you imagine a battery being so poor that each cell is virtually a dead short, then that is like putting an iron bar across the charger, which any charger (including an Alternator) is going to struggle to survive.
 Soft Start prevents the battery destroying the charger.
Only one motorhome charger has the equivalent of a soft start, the rest will mostly pop if you put them through the scenario above.

And to those who say they are "current limited, etc and will handle any load", then yes the electronics do have protection built in, but it won't protect against misuse.
For example one Leisure charger is designed to operate flat out, using a temperature sensor in the output stage to regulate the charger work rate. But it takes a little while for the heat of the output components to reach the temperature sensor mounted on the same heatsink. 

So if you ask it to bring up a battery from very low the current draw by a single battery rises the temperature so high and so quickly, the component can be burnt out before the temperature sensor wakes up. 
Imagine 3 x 100Ah batteries run down low trying to draw nearly 60amps from an 18a charger? It might tolerate it a few times, but ultimately it will take it's toll. 

So you can see why motorhome chargers can have practical limitations on battery bank sizes, and why the industry put that 'guide' at 10 times the charger output converted to AH? On an 18amp charger, that is a 180Ah total battery bank which should make an allowance for the Starter battery if that is also charged by the unit.
That is not our guide, ours would be a "5 times rule", not 10.


Some Schaudt Elektroblocks can charge the Starter battery at up to 6 amps, which is a third of the charger output, so look at what your particular charger supports when calculating the battery bank size.

Fiat White vans cover hundreds of thousands of miles without  Alternator issues. Trucks cover massive distances in the millions of miles. 
Very rare to hear about Alternator failure in a car, yet you regularly read about Motorhomes suffering them, often at low mileages. 
Usually those fitted with tired multi-battery banks.
Doesn't that suggest that Alternators have limits as well? 

Even the most stupid would accept that putting 20 x 100Ah batteries on a 10 amp charger isn't going to work and that there are limits. 
What isn't always clear is exactly what those limits are for all Motorhome Power Controller chargers and what technology is used inside the box that dictates those limits. 
But we try to give guidance on the exact units we know have weaknesses, see our "Add a Second Battery" web page. It also includes guides on what to do to improve the charging with an additional battery.


HairyFool, You are right about Float being next to useless because a Sargent PX300 could be asked to Float a 75Ah battery right up to 400Ah which is why Float is about short term use only. 
While a charger may overcharge a single battery on log term storage EHU, a few milliamps spread across 4 batteries isn't going to help keep them in peak condition.

Well over my head. Simple for me asked if on board charger would cope with two batteries not one from a mate in Autoelectrics he said it would Bingo added two new batteries. No problems with this for the nearly two years I  had the Dorset, when sold took out the two batteries I had put in and replaced with the original which had been kept nice and warm and fully charged in my garage.
As I said Simple

Heanorboy wrote:Well over my head. Simple for me asked if on board charger would cope with two batteries not one from a mate in Autoelectrics he said it would Bingo added two new batteries. No problems with this for the nearly two years I  had the Dorset, when sold took out the two batteries I had put in and replaced with the original which had been kept nice and warm and fully charged in my garage.
As I said Simple

You can generally add a second battery to many motorhomes and it might appear to work o.k. but did the batteries get 100% charged?
Did they lose capacity faster than they should?
Would they have lasted their full lifetime or suffered failure at 3 years?
Did they charge as fast as they might or the usual 'half' speed? 



I guess it depends on what you are happy with : optimum or otherwise?

Those who have joined the forum recently will not know that my Autosleeper was designed and built with two leisure batteries, one of 100Ah and the other 75Ah sited some 7 metres apart both connected in parallel to the Sargent PSU towards the centre of the vehicle by 2.4 mm sq stranded wires.

With the support of an 80W solar panel and extensive use off hook up, they performed perfectly for 6 years and I'm perfectly satisfied with that. I'm sure they would have still been ok now if it hadn't been for a combination of a high ambient temperature causing an obscure mechanical fault to the inline fuse to the solar panel and my flippant use of a laptop for extensive periods assuming it was being powered by the sun.... One of the batteries failed but I replaced both like for like.

Which model of Sargent PSU does it use?

The second worst, the EC325 which is of a very poor design and was quickly replaced with the EC328