# Leisure battery charged from Alternator?



## Fancythat (Dec 1, 2011)

Hello,

I want to get something clear in my head about how my leisure battery is being charged from the alternator.

First, my batteries (Starter and Leisure) are on their last legs and both drop dowm to around 12.5 or less very quickly...they are booked in to be replaced in about a weeks time. When I start my engine, the control panel shows a 14.4 voltage at both batteries, therefore the alternator must be charging the leisure battery also.

Here's the questions...

Is it normal for the leisure battery to get charged from the alternator? (second-hand 2008 Swift Suntor 590RL)

Alot of people on this site have talked about buying expensive battery-to-battery chargers, so do you think that someone has fitted one to my MH? or is it normal that the alternator also charges the Leisure battery? I know that the starter battery and the leisure batteries are not directly connected together as their voltages fall at different rates.

Many thanks


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## runnach (Dec 1, 2011)

Fancythat said:


> Hello,
> 
> 
> Is it normal for the leisure battery to get charged from the alternator? (second-hand 2008 Swift Suntor 590RL)
> ...



I believe it is normal practise that both batteries albeit independant of each other are charged from the alternator, certainly the case on my van.

In respect of the leisure battery, it is important to establish what amperage the battery is being charged at .

Remember if you have an 85 amp battery and it is charging at  3 amps per hour as an example ...then it will take 28 hours or so of consatant engine running to fully charge the battery ....worth consideration before changing the battery .N aturally this assumes that the battery is flat and you are charging solely from the engine and not using  240 v mains

Also it is worth bearing in miind that if you are running the fridge off the 12 v option then the amperage to the battery will be reduced and it will take longer to charge .

I am pretty sure my understanding is accurate, but others of a more electrical nature will no doubt correct me and expand upon my answer 

Channa


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## oldish hippy (Dec 1, 2011)

please look back through my posts and look for goat boys site  


please can a forum mod make a sticky post with the link to goat boy as i seem to only post his site he is nothing to do with me but it was the best and easiest info i found  and have posted this a lot in last few days thankyou


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## Beemer (Dec 1, 2011)

My vehicle and leisure batteries are charged off the vehicles alternator too.
Mine is a 2005 vehicle.
I think it is standard to have both batteries being charged from the alternator if the vehicle is factory built.


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## Fancythat (Dec 1, 2011)

Beemer said:


> I think it is standard to have both batteries being charged from the alternator if the vehicle is factory built.



I think you may have hit the nail on the head "...if the vehicle is factory built"

What confused me was reading several threads about people fitting expensive battery to battery chargers. I can only assume that they are fitting them to self-build MHs then?


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## Fancythat (Dec 1, 2011)

oldish hippy said:


> please look back through my posts and look for goat boys site



Thanks Oldish Hippy, I read Goat Boys article about leisure battery installation. Very informative.


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## Fancythat (Dec 1, 2011)

Thanks Channa, the batteries will be fully charged before fitting & I do not use the fridge.


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## lebesset (Dec 1, 2011)

although new batteries seem to charge to 12.7 when new , it isn't long before they reach a maximum of 12.5 ...that seems to be the norm 

my batteries [ including starter ] have maxed at 12.5 for about 3 years and are just fine like that 

are yours worn out , but still holding a 12.5 charge ?


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## vindiboy (Dec 1, 2011)

There is a simple relay that allows charge to your leisure batteries when the engine is running, very common and basic  kit. The previous poster was correct in saying that having your fridge switched to 12 volt  will be a big drain on your charging system too,  there is also a relay in the fridge wiring system that only allows  power to the fridge  [ 12 volt ] when the engine is running, this is to prevent rapid battery drain.I never run my fridge on 12 volt now as  I feel it is not worth the bother, as we move frequently even when wild camping we find that our fridge  after running all night on gas will remain  chilled for many hours when travelling till it goes back onto gas again.


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## vindiboy (Dec 1, 2011)

In my Caravanning days I fitted a connection in the boot of my car and kept a spare battery  connected to it so that as I drove about in the car I was charging a spare battery for the van so always had spare capacity, you can also do this via the towing hitch electrics as there is  a pin for this too. ie it is live when the engine is running , again through the relay  in the engine compartment.


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## Fancythat (Dec 1, 2011)

Hi Vindiboy, I don't use the fridge ever. The question was whether or not the leisure battery on my MH is charged by the alternator as standard (i.e. from the factory) or whether some other battery to battery charger had been fitted. I had previously been led to believe that the leisure batteries were normally only charged via a 240 Volt hookup, solar panels, or genny and that if you wanted to charge via the alternator you had to buy some expensive kit to do it. It seems that this was duff information and that it is quite usual for the leisure batteries to be charged from the alternator on factory built MHs. No fridges here :0)


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## vindiboy (Dec 1, 2011)

OK, if your control panel is showing 14.5 volts when the engine is running ,this indeed proves that a charge is coming in from the Alternator,  it does NOT mean that your batteries are charged to this amount , ONLY that this is the INCOMING rate, it will take some time for your batteries to reach and maintain this  voltage.If you leave your van hooked up to mains and  ensure that a charger is in line and active [ you should have  an in built charger on a van of your age ] and leave it on charge for 24 hours and then check  your batteries are  at about 14 volts and holding you may find that you don't need  new batteries at all.


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## Firefox (Dec 2, 2011)

It's possible to to charge batteries off an alternator after a fashion but I've found I get 80% charge or so. You may get more or less depending on your batteries and set up. The alternator is a pretty crude tool. The best chargers operate in steps of time at constant voltage and constant current. My 240 V mains smart charger gives 90-95% charge. Think of building up charge on the lead plates as piling balls up. If you slap them on any old how they fall off or don't fill the gaps. If you place them carefully, you can pile them higher.

That's why a battery to battery or alternator to battery charge unit can give good results but they are expensive pieces of kit. You can fit them to self builds or to proprietary conversions. I haven't got one fitted. All I have got is a 100A cable and manual switch. I don't even use a relay, LOL.


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## Fancythat (Dec 2, 2011)

Alas I tried recharging the batteries last weekend using the latest and greatest Ctec charger in Recond mode (desulfate mode). Also I went for a 2 hour drive yesterday and this morning my leisure battery is at 12.2 volts and my starter is at 12.5 volts. Last night they were both at around 13.5 volts when I went to bed. All last year they were staying above 13 volts. Anyway, I'm getting a new starter battery and 2 x new leisure batteries fitted in a week as I wildcamp full time.

Merry Christmas everyone


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## NicknClair (Dec 2, 2011)

Take a look at this link, might be useful and the main reason I took a production Swift Kontiki and fitted a B2B;

Sterling Power Products: Battery-to-Battery Charger Information

The original split charge system is (Pardon the expression) a load of toilet. Especially when you have a battery of 270AH and do a lot of "Wild Camping".
I have 3 methods of power replenishment;

1. Upgraded Mains Charger, which is also an Inverter (Commonly called a Combi unit). Was more interested in the inverter as the wife wants her hairdryer/use of a Microwave, but having the improved mains charger insures my leisure battery can be left on hook-up when at home, but also be charged at the correct stage with the correct volts and amps input. This was a handy upgrade as the factory mains charger is also a bit on the weak side for the size of leisure battery fitted.
2. 120W Solar Panel, for when the Sun is on our side. Ideal when weather is good, as not heating and less lighting means less power, so the panel 9 times out of 10 keeps us going for a few days without intervention.
3 and the most important, our B2B charger. As kindly pointed out the Alternator can be a crude device (especially when used in a standard/basic split charge circuit), HOWEVER when using such a device as a B2B charger, the alternator can be used to your advantage. I have lived with a B2B fitted to the last 3 vans and would not go back as being able to start the van and produce up to 50A on the engine merely ticking over is no different than running a genny with a very good mains charger coupled to it, only i'm not worried about a different fuel source to carry, nor loosing valuable storage space to keep a genny on board (not including the weight).

Standard split charge systems use a simple spot light relay and are typically installed using 2 or 2.5mm cable, which when using a clamp meter on the Swift I measured a pathetic 9.2Amps. Now take the fact that I have a 270AH Battery, which gives me roughly 80ah of usable power above 12.0V. 80Ah divided by 9.2Amps would mean that I would have to run my engine for roughly 8-9 hours before getting all the power back to my leisure battery (This principle can be used when using a genny coupled to a mains charger i.e a 20A mains charger would take roughly 4 hours of running to get the battery back to full capacity). Now take the B2B I have fitted, (which is a 50A unit), I would look to be running the engine for roughly 1.6 hours. Now take the fact that we normally move off the place we stay after say 2 days, meaning by the time I have driven a couple of hours down the road, the leisure battery would be fully charged ready for it's next pounding. If the wife has used the hairdryer, then I can simply run the engine for a little while just to "Top-up" the battery if and when needed.

B2B's are simply brilliant and just do the job. As an ex self builder, it is reasonably easy to install to either a self build or a production motorhome. I have lost count on how many I have fitted to other people's vans. Will I keep using them.............................. DAM RIGHT!!!!!! With using the van in all weathers, it means that we always have an ability of getting power back to the battery bank quickly and safely. If you have one installed, it is so important to make sure the correct cable is used, as your investment simply will be a waste of money!!
When I change the van, I will be looking forward to fitting the new "Wildside" range of units when they are released, which include a solar regulator fitted into the unit!!!

Sterling Power Products: Find out more abotu Wildside


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