# fitting second leisure battery



## vicdicdoc

I'm having a 'cloudy brain' day . . (happening more & more now I'm 60  )

I've decided that I want to fit a second leisure battery into my Fiat based Lunar Champ A520; its already got one (I think 90amp) leisure battery fitted under the drivers seat but its got no markings on it - regardless, I'll be purchasing two new deep cycle leisure batteries together so I know they are both new & evenly matched - my question is (forgive me for being dumb) - do I connect (+) positive to (+) positive & (-) negitive to (-) negitive . . or (+) to (-) ??? 
also do I need to add a second negitive earth strap or will the original surfice ?


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## Scotjimland

Hi Vic

It's Pos to Pos and Neg to Neg. Your original earth strap should be fine.

Look here for some helpful info>>>> Click Here<<<<


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## 96854

*Second leisure battery*

Hi,
you must connect the `same to same` i.e. positive to positive/ neg to neg. If you wire `in series` - pos to neg - you will end up with 24 VOLTS and fry most of your electrics. Have a look at the following links:
http://www.eclipsehistory.org.uk/photogal/engindrg.htm
http://www.kampenwagen.co.uk/Leisure Battery.htm

The second one appears to be written by an auto electrician who definitely knows his stuff. I have used his plans to make an automatic charging/fridge circuit, and it works superbly.


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## vicdicdoc

Thanks Scotjimland & Paulocbx for the welcome info, I was 'almost' certain that was the correct wiring up but began to doubt myself ! 
I've ordered 2 x 85amp deep cycle leisure batteries from a local stockist @ £36 each. 
I really would have liked 2 x 110amp but the under seat space is not quite big enough. 
Second question - is there a need to fit an in-line fuse ( ~ 40amp) between the two leisure batteries ? I can't see the reason there should be one but just to make double sure your advice is again indispensable.
many thanks [in advance]


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## Scotjimland

Hi Vic 

No need for a fuse between the batteries .. good luck with the project


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## RobinHood

vicdicdoc said:


> Second question - is there a need to fit an in-line fuse ( ~ 40amp) between the two leisure batteries ? I can't see the reason there should be one but just to make double sure your advice is again indispensable.
> many thanks [in advance]


The advice I've seen quoted is that if the batteries are adjacent, a fuse is not required, if they are not, then a fuse is recommended, and with a long wiring run potentailly passing thrugh bodywork I could see the reason for this.

On my previous 'van, the batteries were under the driver's and passenger's seat respectively, and were fuse protected in the positive line. On my current 'van', the two batteries couldn't be closer to each other (in the garage), but have been protected by a fuse in the positive line between them.

Not sure where you are mounting your second?


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## Brambles

Also note when connecting two batteries in parallel, the +ve feed to electric systems should be taken from one battery and the -ve (to chassis) from the other. This balances up any volt drop in the cables especially if the batteries are not mounted next to each other. Same if you have a whole bank of even 100 batteries +ve from one end of bank and negative from way along the other end of the bank. 

Agree a fuse should be fitted between the batteries if they are not located together in case cable shorts, but when they are next to each other as long as there is no danger of any shorts or damage to cable then leave the fuse off. The problem is if the fuse was to blow you may not know about it as one of the batteries could still provide power.
If the batteries are far apart and cable could be shorted through damage, and you have wired as I have mentioned above, then two fuses will be required , one either end of cable. Better to make sure connecting cables are just extremely well protected and prefarably have batteries sited next to each other.

And please - negative earth vehicle, connect positives 1st and then negatives. If your spanner shorts positive to chassis with negs disconnected - no problem. 

Jon.


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## grout20

*Connecting to two parallel Leisure batteries*

Re Brambles last posting on this old thread, if there is a solar panel charging the leisure batteries, and also a mains inverter option in the system, does "Brambles rule" still apply?

i.e. should ALL connections to the +ve terminal be to ONE of the parallel batteries, and ALL connections to the -ve terminal on the SECOND parallel battery?

I'm checking over our own solar/regulator/lcd display/inverter wiring trying to figure out if it's all correct/most efficient.

Everything LOOKS professionally installed .. but the two old leisure batteries that came with the van failed (ok .. 7 years old and now replaced!) but with evidence of overcharging/boiling, despite a regulator in the system. And the Statpower 1500 inverter stopped working last year too! :roll:

The Solar/LCD dispay often shows 14.5 in sunshine, and you can hear the nice new batteries bubbling away. Is that right? :?

Thanks in advance for any advice

john


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## DABurleigh

John,

Jon is entirely correct, though I would not call it a rule  Whether it makes the slightest bit of difference in practice depends on the currents you draw and the thickness and lengths of the cables joining the batteries.

The higher the currents and thinner and longer the wires, the longer life you will get out of your batteries by doing as he recommends. For batteries together joined with welding cable, forget it if it happens to be already wired in "ladder" configuration.

See this thread:
http://www.motorhomefacts.com/ftopicp-168474.html#168474

Dave


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## CliveMott

*CLIVE,S SITE*

Or a few hints here also!

http://www.motts.dsl.pipex.com/second leisiure battery.htm

http://www.motts.dsl.pipex.com/SPLIT CHARGING SYSTEM.htm

If you go the the bottom of any of these pages you will find a link back to my main menue where lots of other junk can be found.
C.


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## grout20

CliveMott ... thanks for the reply ... useful advice as always.

Your parallel battery diagram suggests connecting the MH to the +ve off one battery and the -ve off the other battery.

Is that the best solution when connecting a Solar Panel to the batteries (from the regulator) and also when connecting an inverter to the batteries as well? Or doesn't it really matter?

And one final query (talk about taking advantage!  with a regulator in the system, any suggstions why my (separate) LCD display shows up to 14.6V? 

A faulty display?, or the solar regulator failing to cut-off at 14.4V limit to stop the batteries bubbling dry? 

(Both batteries sizzle nicely when the sun shines! :roll: )

Thanks in advance

John


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## DABurleigh

John,

As Clive's not around.

The same Physics applies whether it is a solar panel or anything else, so, yes, in principle. In practice it is as I tried to explain in the post above. Frankly for solar charging currents, don't worry unless your batteries are apart or connect by thin wires.

If, on the other hand, you are really fishing for your bubbling battery fault, I can assure you it has nothing to do with your wiring configuration, and probably everything to do with a faulty regulator. To check for certain, get a multimeter on your battery terminals when the sun shines. It shouldn't be above 14.4V; if it is not, but your battery is still bubbling, it has a duff cell.

Dave


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## CliveMott

*INTELLIGENT CHARGERS*

Many Motorhome power supplies and even solar regulators use "intelligent charging techniques". That is they take the battery terminal voltage above 14 volts under later phases of charge to ensure a faster and more complete charge than limiting the voltage to 14 like the alternator does.
Intelligent chargers are often refered to a "3 or 4 stage chargers".

BUT there is a downside to this technique.

How do they work?

In phase 1 a charger will limit the charging current to that sustainable by the charger. For a mains hookup it will be a constant current. For a solar panel it will be sun and panel size dependant. This will last until the battery voltage typically reaches 14 volts.

Phase 2 and the charging current will be regulated down to stop the battery voltage going in excess of 14 volts. That is until

Phase 3 and the charging current has fallen to a lowish level and then the voltage is allowed to continue to rise to say 14.4 volts (sometimes it more). This will continue until

Phase 4 and the charging current has again fallen to a very low level and the battery is then considered "charged" and the charger voltage is then reduced to 13.5 - 13.8 volts as a maintaining charge.
When this last phase kicks in the charger output current drops to zero until the battery voltage falls sufficiently to allow current to flow again.

Now, the potential problems here are :-

1 The battery is getting old and leaky and the leakage current is in excess of the very low charge current required for phase 4 to kick in. Hence it remains at 14.4 volts and gently boils the battery.

2 You have some small load on the battery (Radio / Alarm for example) and the same scenario as 1 will apply.

3 You have significantly increased your battery bank size and the normal leakage for this bank size is in excess of that required to allow phase 4 to kick in and reduce the voltage.

I believe that this is why after all these years that all motor vehicle manufacturers still stick with a limit at 14 volts and accept the 80% charge limitation this is likely to achieve. It remains the best compromise if you want to limit warranty claims and minimise gassing.

After all the technology for "intelligent charging" could be incorporated within the vehicle alternator regulator at zero cost of they wished to do it.

Its your choice. I notice that some of the principal suppliers of chargers to European motorhomes have a selection link for selecting "maintaining" or "3/4 stage". So even they remain on the fence in this debate.

Good luck
Clive


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## CliveMott

*AND THERE'S MORE!*

Chargers for industrial batteries, like those fitted to fork lift trucks are today a lot cleverer. They monitor the rate of fall of charging current so can allow for leakage. Also they frequently charge in large pulses monitoring how the battery voltage falls each time the charging pulse stops. There are many different charging regimes which can be defined. However I do not believe that this level of sophistication has so far reached leisure battery chargers fitted to recreational vehicles.

Does anyone know differently?

C.


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