# Charging the batteries.



## Pudsey_Bear (Sep 25, 2008)

Has anyone considered incorporating the VB with the LBs to make it a bigger system, it would mean a bigger bank of batteries to both start the engine and to use for leisure, if used with a low volts cut out there should be no problems, and obviates the need for extra gizmos to charge both sets.

What extra bits would be needed more than a couple of thicker leads to connect them.

I assume there must be some problems if it's done this way, but I can only see the advantages, but the Mh 12v sparky side is a minefield, so I don't mind being shot down in flames, but if it wouldn't work it'd be nice to know why specifically.


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## Bazbro (May 9, 2005)

The biggest danger I see, Kev, is that there may then be insufficient 'juice' in the vehicle battery to start the engine. Ok, so you propose a "low voltage" warning, but (certainly with a diesel engine) a pretty hefty "ooomph" is needed to start and that may not be available if you're using the engine battery as part of a leisure system.
A nice idea but I wouldn't bother. Another leisure battery for £80-£100 solves all the problems before they even start!


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## Fatalhud (Mar 3, 2006)

Engine and leisure batteries are designed differently

Engine battery is designed to cope with a massive currant discharge over a short period, 
To put a leisure battery through the same load can damage the lead plates and shorten the life of the battery
Although I would admit to using the leisures batteries to start the engine when in the sticky brown stuff :wink: 

Alan H


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## Pudsey_Bear (Sep 25, 2008)

How many of us actually buy a real leisure battery, if in fact they even exist anymore, mine are sold as vehicle batteries, but the spec is identical to a starter battery, just labeled and sold differently.

And a 12.5v cut off point would ensure more than enough power for starting bearing in mind more than one battery supplying it, in effect both systems would have a boost by using a combination.


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## Wizzo (Dec 3, 2007)

Kev_n_Liz said:


> And a 12.5v cut off point would ensure more than enough power for starting


I'm no technical bod but I'm not sure that is a practical limit. Under no load situations my batteries may read 12.6v or above but as soon as anything is turned on the voltage reading drops by around 0.2v and can be as low as 11.8v whilst still happily supplying lights and tv etc.

I'm with Fatalhud on this one. The two types of batteries are (or should be) different and I for one would prefer to keep them separate.

JohnW


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## PaulW2 (May 30, 2010)

Some motorhomes (for instance Elddis) incorporate a switch that enables you to run the motorhome utilities off the vehicle battery, as an alternative to the leisure batteries. Presumably intended as an emergency measure only.


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## Pudsey_Bear (Sep 25, 2008)

I'm no expert either, and I only offer the combination as a suggestion, mainly as I thought it might be a interesting topic than to actually get feedback on actually doing it.

LBs are it seems only such if you spend a bit more than I would like to, as the technology is a little different, but the market is a lot smaller, so supply and demand dictates the prices.


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## listerdiesel (Aug 3, 2012)

I'd not have a problem with that in principal, subject perhaps to a decent switch between the for isolating one from t'other.

Whatever folks say about leisure batteries and starter batteries, there are only so many ways you can build a wet lead-acid battery! The biggest issue is quality. Buy a good quality battery and it will last you for years if looked after.

If you buy a decent Varta 110AH car battery as I have in the Discovery, there's no real reason why it couldn't be used as part of a motorhome system. We don't as the vehicle is obviously separate, but in Kev's position I'd certainly give it a go.

Peter


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## Pudsey_Bear (Sep 25, 2008)

I had a quick Google and feel so much better.

VB v LB


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## Pudsey_Bear (Sep 25, 2008)

Posts crossing in the ether :lol: :lol:


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## spykal (May 9, 2005)

Hi Kev

The idea of using the power available in the vehicle battery does make a lot of sense ...well it does to me :lol:

Our Autocruise motorhome that we have now allows the use of the vehicle battery as an alternative source of 12v power to our 2 habitation batteries, the Sargent unit fitted to our van will, if we choose to use it, also protect the Vehicle battery from over discharging by automatically switching back to the leisure batteries at a level that will ensure that the vehicle battery will still have enough power to start the engine.

I have mentioned this feature to many an owner but rarely do I find that anyone uses it or even knows about it :roll: ... I do and always have used the vehicle battery to supplement the leisure batteries.

When we had an Autosleeper Executive that had primitive Zig unit for charging and power I often used the vehicle battery to power the TV via a special bit of kit which cut off the power automatically to protect the vehicle battery ....just the same as the Sargent unit in our modern van does now. The device I used came from Maplin but they do not supply it now. The nearest I can find that would do the same job is this one from Waeco << ( intended for use with a cold box but just as useful for running anything 12v from the engine battery while stationary)

Batteries need using, they do not last that much longer if you do not use them. So I agree with you that in that having all that power just sitting under the hood of a van and ignoring its availability is not very sensible.

Good thread !

Mike


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## Bazbro (May 9, 2005)

A further thought, Kev... If it was "the norm" to do as you suggest and then someone suggested a small relay to keep the two different types of battery separate, I think everyone would be saying "What a great idea, and it answers the problem of flattened batteries and me not being able to start my bloomin' engine in the morning!"

Vehicle manufacturers don't fit batteries that are larger than is actually needed. If the battery is shared, after a extra-heavy night's usage of lights, water pump, telly, heating, etc., it follows that capacity much less than standard could leave you stranded. If you really need that extra capacity, it must be cheaper and easier to just fit another leisure battery - have you seen the exorbitant cost of inter-battery cabling??

20-25 years ago, AutoSleepers never fitted "leisure batteries" as standard and you were expected to use the vehicle battery for leisure purposes as well. That policy didn't last - it was an eccentric decision of Anthony Trevelyan's, I think.

But have a go at it, Kev. I'd take a set of jump leads with you, though! 

Yes, a good thread.


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## listerdiesel (Aug 3, 2012)

Kev_n_Liz said:


> I had a quick Google and feel so much better.
> 
> VB v LB


They are on dodgy ground in the second half, the bit about thick and thin plates and the effects thereof.

But basically they are the same thing, just packaged differently.

It's all about surface area, not as much about the thickness of the plates.

Peter


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## Bazbro (May 9, 2005)

I thought thicker plates, apart from being more expensive, were merely better able to resist buckling?? Maybe not.


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## listerdiesel (Aug 3, 2012)

Bazbro said:


> I thought thicker plates, apart from being more expensive, were merely better able to resist buckling?? Maybe not.


To a degree that is correct, thicker plates do resist current induced distortion, but the main reason for having different thicknesses of plates was to provide different capacities of battery in the same case dimensions.

This in the old days, a battery would be listed as a 7-plate, 9-plate and 11-plate, with corresponding increases in capacity as the number of plates in parallel went up.

This enabled the manufacturers to use a standardised range of cases with a range of capacities, the smaller capacities having thicker plates and separators.

I've got some old Oldham battery brochures that list the different types with plate details.

Peter


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## 747 (Oct 2, 2009)

You probably need all of your van batterys capacity on a Winters morning at -5. In Summer, it will take a lot less power to turn the engine over.


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## Pudsey_Bear (Sep 25, 2008)

Bazbro said:


> A further thought, Kev... If it was "the norm" to do as you suggest and then someone suggested a small relay to keep the two different types of battery separate, I think everyone would be saying "What a great idea, and it answers the problem of flattened batteries and me not being able to start my bloomin' engine in the morning!"
> 
> Vehicle manufacturers don't fit batteries that are larger than is actually needed. If the battery is shared, after a extra-heavy night's usage of lights, water pump, telly, heating, etc., it follows that capacity much less than standard could leave you stranded. If you really need that extra capacity, it must be cheaper and easier to just fit another leisure battery - have you seen the exorbitant cost of inter-battery cabling??
> 
> ...


I haven't said it was the "norm" Bazbro, how could I when I said it was only a suggestion, and how can it be cheaper to buy extra LBs, when there is one already there getting used for a split second every so often, then get's ignored except to power an alarm, which would be better served by the solar.

And to have Peter, who's job entails daily contact with both batteries and the charging of say it's not a bad idea, is enough for me, and maybe in the future I might run a cable the 600mm or so and try it, once I figure out it's size, and fusing etc, the Smartcom would then be redundant except for running the fridge in transit.


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## Pudsey_Bear (Sep 25, 2008)

listerdiesel said:


> I've got some old Oldham battery brochures that list the different types with plate details.
> 
> Peter


I told em Oldham, still going sort of.


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## teemyob (Nov 22, 2005)

*batteries*

make sure you have some jump leads to hand.

We have 3 batteries

Chassis
Habitation
Dedicated inverter.

Can battery ran low just by running the Eberspacher a bit too long. Had to jumo it from the Habitation.

TM


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## Pudsey_Bear (Sep 25, 2008)

Always do, even if I don't need, others might.

But I've never flattened any LBs since we started, so it's only in an exercise anyway, but if going again I'd get a matched pair of decent ones and use them both as LB/VB, think of the savings in extra bits to charge a traditional setup, no clever relays needed, no B2B, spend it on better quality batteries, maybe 4 x 6v instead of 2 x 12v.

My only thoughts would be about both the panel and the alternator feeding the batteries at the same time, I don't see a problem as wouldn't the alternator sense the full charge and stop and also the solar controller.


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