# Do the leisure batteries charge when driving?



## adonisito (Nov 6, 2009)

Yes, I know I should know this, but never having had a problem with the leisure batteries, its never occured to me until now. This is because we are away next week and will not be on any form of EHU.
So, how can I find out, is it common practice in vans? Do I need a battery master?

Thanks.


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## teemyob (Nov 22, 2005)

*BM*

Hello,

Yes they do charge.

No you don't need a Battery master.

TM


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## adonisito (Nov 6, 2009)

Goodness, that was quick, thanks Teemyob.


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## wakk44 (Jun 15, 2006)

The leisure battery should be charged via a split charge relay when the engine is running.

It can be checked either on your control panel(if you have leisure battery status indicator)or by putting a voltmeter across the leisure battery terminals and then starting the engine,when there should be an increase in voltage.


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## Wizzo (Dec 3, 2007)

Agree with the above but just be aware that once the vehicle battery is fully charged after starting then the charge to both batteries will drop to a trickle whether or not the leisure battery is still nearly flat or not. It may take some driving to put back what you have taken out.

JohnW


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## WildThingsKev (Dec 29, 2009)

Wizzo said:


> Agree with the above but just be aware that once the vehicle battery is fully charged after starting then the charge to both batteries will drop to a trickle whether or not the leisure battery is still nearly flat or not. It may take some driving to put back what you have taken out.
> 
> JohnW


Is that the case? Never knew that.

Presumably then that is where battery to battery chargers come in?


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## subfiver (Oct 15, 2011)

> be aware that once the vehicle battery is fully charged after starting then the charge to both batteries will drop to a trickle whether or not the leisure battery is still nearly flat or not


Alarmed by this statement; I had assumed that once the vehicle's battery achieved full charge then the bulk of the alternator's output, after ancilliaries like lights etc, went into the habitation batteries. This is certainly what happens on my boat, via a Victron Argo-FET battery isolator.

If my Pilote (delivered next month) doesn't do this I shall me mightily pee'd -off as I was relying on this to avoid EHU's (when the sun's not shining, that is!)


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## Wizzo (Dec 3, 2007)

Yes it surprised me too, but read the blurb on the Sterling B2B charger and that is what it says. I can say from practical experience too, that since changing my vehicle battery last year my hab battery no longer charges up as quickly on a journey - something I had never before considered and like you I always assumed the alternator just kept pumping out full juice regardless.

JohnW


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## blondy (Aug 23, 2007)

Yes it's well worth having a bat to bat charger fitted in my opinion,
Mine works very well, since fitting never had flat leisure bat,
I have no solar panel fitted.


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## DJP (May 9, 2005)

They do charge but has anyone ever measured the amperage they charge at?
The reason I ask is that our 1st van (2005) Lunar did not appear to charge the batteries whilst driving. I had an auto electrician check it out for me and yes, they were charging (vehicle battery fully charged at the time). They were charging at............*2 amps!*. So 2 x 110amp batteries after a weekend away and we might have used 30% of the power, approximately 65 amps, it would have taken 32+ hours of driving to replace the power used.
The auto electrician (he was fitting the towbar and A Frame at the time in Stoke on Trent) said that 2 amp was about right!


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## nicholsong (May 26, 2009)

I fitted a Sterling B2B which gets round the problem very effectively, especially since I average about 25 miles per travelling day, but that is sufficient to give me 2-3 days of wild-camping on 2X80amp batteries which are far from new.

I don't know for sure, but I imagine it will also prolong the life of my batteries since they will be kept topped-up for longer periods. Possibly offsetting some of the cost of the B2B over the years.

Maybe someone could comment on longevity point?

Geoff


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## Wizzo (Dec 3, 2007)

Thinking about this, for those of us without B2B chargers at the moment it may be better to drive with everything electrical turned on that you can - radio, lights, fog lights, heater blower etc - that way the engine battery will need more power from the alternator and thus will also supply more power to the leisure battery!

 

JohnW


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## WildThingsKev (Dec 29, 2009)

Wizzo said:


> Thinking about this, for those of us without B2B chargers at the moment it may be better to drive with everything electrical turned on that you can - radio, lights, fog lights, heater blower etc - that way the engine battery will need more power from the alternator and thus will also supply more power to the leisure battery!
> 
> 
> 
> JohnW


'Been thinking about this, and I read a related technical thread on outandaboutlive forum yesterday so today I ran a simple test. (X250 base van)

It might be specific to Rapidos, and from recent threads on here even they vary, but here it is.

Unplugged ehu and switched on extract fan and some halogen bulbs ; total draw 7A which I left for 8 hours to get the twin leisure batteries down significantly. After a bit of recovery time the batteries were at 12.4v, vehicle battery was fully charged.

Started the engine, on tickover the CBE panel initially showed 21.5A going in to the leisure batteries. Revving the engine didn't make any difference, NOR did turning on full headlamps and cab fan. So sadly there goes that theory Wizzo, at least on my van

Also; after 3-4 minutes, by which time the charging current was down to about 15A, I turned the engine offf and reconnected the ehu which showed a similar charging current of 16A and which over the next 3-4 minutes reduced at the same rate as it had been doing on the alternator.

That suggests to me that the alternator charging circuit on the Rapido is doing a pretty good job of charging the leisure batteries even when the vehicle battery is fully charged.


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## DABurleigh (May 9, 2005)

Wizzo said:


> Thinking about this, for those of us without B2B chargers at the moment it may be better to drive with everything electrical turned on that you can - radio, lights, fog lights, heater blower etc - that way the engine battery will need more power from the alternator and thus will also supply more power to the leisure battery!
> 
> 
> 
> JohnW


I know where you're coming from, but quite the reverse, actually 

The charging currents to vehicle and leisure batteries with a split charge relay are determined solely by Ohm's law. And that means if you use decent cable to the leisure batteries, you can get large charging currents.

So, for example, when I fitted my B2B, I actually had to provide an option to switch it out of circuit when I was running the roof aircon off my alternator and Victron inverter, because I needed more than the B2B's maximum of 45 Amp output to keep a positive energy budget into my leisure batteries. So effectively I retreated to a good old simple split charge arrangement to get MORE charging current into the leisure battery.

Similarly if you have ancillaries such as blower, wipers, lights you will find this results in a much smaller charging current to your leisure batteries.

Dave


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## 747 (Oct 2, 2009)

My Burstner does not drop back to a couple of amps when the van battery is fully charged. The ammeter on the control panel shows a true reflection of the leisure batteries taking what they need. This may be due to having the Elektroblok system controlling the maximum charge rate.


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## Wizzo (Dec 3, 2007)

DABurleigh said:


> I know where you're coming from, but quite the reverse, actually. Dave


OK I'll admit to being confused now. I know little about this electrickery stuff and the only laws I know are Sod's and Murphy's.

Are you saying that the blurb from Sterling is wrong or that the deficiency can be overcome by rewiring the supply to the leisure battery/batteries?

JohnW


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## DABurleigh (May 9, 2005)

I'm not sure what part of what blurb and what deficiency you are on about, but just search my posts on MHF about the B2B chargers.

I've long said the B2B is brilliant technology, but whether it makes a sensible purchase depends on your particular requirements and pattern of use, and even then, it only gains over a split charge relay, yes, with sensible cable (I have mine doubled up for better flexibility than one thick one) over a minority of the charging cycle for batteries depleted at least to 50%.

Here's one:
http://www.motorhomefacts.com/ftopicp-582226.html#582226

Dave


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