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 1 or 2 Alternators?

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Andy W
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PostSubject: 1 or 2 Alternators?   Mon May 04, 2015 5:41 am

I am just about to embark on converting an L400 Delica to take my wife and i through Europe and on to Singapore and am in the process of designing the electrical system.

The dilemma is that the vehicle has an air conditioning system fitted to it but we are not likely to use it, therefore it will be redundant; this then leaves a space on the engine where a second alternator could be fitted.

We are going to be travelling for the experience rather than having all of life's luxuries with us, so will not have a TV, microwave, surround sound system etc. just the basics such as lighting, fridge, chargers etc. and space will be at a premium.

If I stick with the original single alternator, I will need to have a split charging system and all of the paraphernalia that goes with it to charge the leisure battery (probably a 110Ah one) which will take up space and have to charge both batteries as required which could be slow for the leisure battery.

If i fit a second alternator dedicated to the leisure circuit in the space where the A/C compressor was, i will have a spare alternator if one fails and a single fast charging system for the leisure circuit which is relatively simple.

The final alternative is to leave the A/C system as is and replace the standard alternator with a larger unit which will allow faster charging times but have all of the associated split charging system as well which would probably be the most expensive choice.

So, I am wondering what peoples thoughts are on this and whether you have experience with similar situations or any other suggestions to throw into the pot! I am also considering fitting a 100w solar panel to the roof of the vehicle to assist with the charging as well - not sure whether this will influence any decision about the alternator though.

Thanks for any thoughts you have,

Andy
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Tom Mc
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PostSubject: Re: 1 or 2 Alternators?   Mon May 04, 2015 7:04 am

Absolutely useless when it comes to electrics, but I'm good at welcoming folk to the forum ...

WELCOME!!! cheers

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Dave10101
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PostSubject: Re: 1 or 2 Alternators?   Mon May 04, 2015 7:58 am

Hi. I am running twin alternators on my Defender 90. I likewise don't really understand why people go for the split charging system. I believe the split charge works well but:
A: if you lose one alternator - you have lost all charging capabilities.
B: You have to charge you main battery before charging your aux battery (user can override this).
C: If the split charge goes wrong, well who knows the outcome?

Twin Alternators with a link switch allow:
A: Both battery systems to be completely independent.
B: If one alternator goes down you have a second which can be linked to charge both batteries.
C: From the moment you start the engine both batteries will receive charge.
D: If something goes wrong all you have is a standard charging system x2 (worst case unhook the belt and don't charge).

The only downsides are:
A: Weight of a second alternator.
B: From the engine you are powering a second alternator (i.e. using minimal BHP).

I run 2x 100amp alternators charging the standard starter battery (optima red top) from one alternator and from the other I charge 2 Optima yellow tops for all auxiliary electrics. On top of this I too run a small solar charging system. (it's small but keeps up with the fridge, led lights, water pump & radio etc).

If you need any further help please ask?
Dave.
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Assassin
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PostSubject: Re: 1 or 2 Alternators?   Mon May 04, 2015 11:56 am

I would normally go for a split charging system as for most vehicles it is fine, but you do need to uprate everything including the alternator, they are cheap and easily maintained and modern monitoring and programmable electronics make setting them up and programming them to your requirements a doddle.

However; while in Europe a defective alternator is not a problem as they can be sourced from anywhere, Singapore may be a different proposition. In such cases, or if you are away from civilisation for more than a week I would opt for the twin alternator set up for reasons of durability and reliability and connect them with a key operated breaker, this gives you two totally separate circuits and the capability to link them if one alternator becomes defunct while out in the wilds.

You start your engine as normal and lift your bonnet, insert your key and turn, this connects both circuits together to run off one alternator, you switch it off again when you stop your engine to isolate them back to preserve the integrity of your engine battery.

One thing I always advocate is putting on a marine alternator as they are sealed and waterproof, even if you only fit one, they are expensive but so durable they will often outlast the engine; its money well spent.
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Dave10101
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PostSubject: Re: 1 or 2 Alternators?   Mon May 04, 2015 9:38 pm

A Assanin says - it's pretty much what works for you & what you feel is best suited for your trip. Cost wise I think they would be in the same price area. I have my link switch in the cab so can connect at anytime whilst driving (winching etc). By connecting the batteries the charge of them will equal out so you could end up with 2 half charged batteries or your equipment draining both your starter battery & aux battery. So linking should only happen when you need an extra boost or to charge both batteries. So if you flatten your starter battery your aux can link and provide starting power - if you flatten the aux battery you can link your starter and have aux power. (with the latter you do risk not being able to start your engine). Many people will say alternators last forever and they don't go wrong often enough to worry about it - I have had one (starter side) go down & I did another 750 miles before I sourced a replacement. It paid off for me to have the twin alternator system! (If I needed an alternator I could have got one within a few days but as I was not desperate for one our journey continued on).
Dave.
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Tom Mc
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PostSubject: Re: 1 or 2 Alternators?   Wed May 06, 2015 8:01 am

Didn't even know you could buy a marine alternator. That's a good call, although it may cope with water ingress but still be vunerable to liquid mud I would have thought???

Tell us more.

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diesel_jim
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PostSubject: Re: 1 or 2 Alternators?   Thu May 07, 2015 2:02 am

The last few defenders I've had, I've fitted twin alternators on to. I'd do it to my Td5 110 if I could find one small enough (diameter) to fit in properly.

I used them for running my winch (and done the same conversions on several friends vehicles)

I figure it just keeps the winch wiring away from the rest of the vehicle, and if it went t!ts up then the rest of the vehicle wiring would still be OK.

modern split charge units are great, but also expensive. the twin alt route was nice and cheap.
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Scratch&Skid
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PostSubject: Re: 1 or 2 Alternators?   Thu May 07, 2015 2:11 am

I am interested in the defender twin alternator setup. Does anyone have more info on this.

I have a split charge system in my 110 that I built myself for about £40 which works a treat but the thought of a second alt running the 2nd battery has crossed my mind more than once.

It would also mean I could mount the auxillary battery in a more favoured location without to much of an issue.

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diesel_jim
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PostSubject: Re: 1 or 2 Alternators?   Thu May 07, 2015 2:24 am

It's easy.

Make a bracket to bolt the alternator to the engine (You can buy the pre made brackets or fab one yourself... Gwyn lewis does kits: here <---)

Wiring is easy too... big cable from the alternator back to the second battery.  then the warning light wire back to the dash (and the way I do it... some disagree) to a warning light bulb (on a pre Td5 defender there is a 24v warning light already fitted into the dash lights, so just needs a 12v bulb putting in) then through the contacts of a relay (spotlight type is fine) and then back to the +ve of the new battery.

then take an ignition switched +ve from the dash, and take it through the coil of the relay (with a fuse) back to earth.

So when you turn the ignition on, the relay will energise and the second alternator warning light will come to life. then it'll charge the second battery AOK.  earthing through the chassis shared with the main alternator works fine too. even different voltage (say a 12v and 24v on the same vehicle) will work OK.

Some people say that you don't need the relay that I use, and you can just wire the alternator straight to the ignition 12v via a warning lamp.  I suppose that would work, but some alternators use the warning light as a sense wire to measure the voltage in the battery, so in theory you could over or under charge the aux battery if the second alternator is sensing the voltage from the main wiring system.

Plus, using the relay, both systems are totally separate.
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Scratch&Skid
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PostSubject: Re: 1 or 2 Alternators?   Thu May 07, 2015 2:30 am

Spot on ta! food for thought.
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Dave10101
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PostSubject: Re: 1 or 2 Alternators?   Thu May 07, 2015 9:04 am

As above, that is how I wired mine but I cannot remember if I used a relay. I also used the Gwyn Lewis mount as it's all a perfect fit and much quicker than making one. Just make sure you main Alternator to battery wire is thick enough to cope with the amps the alternator will put through it.

I had a friend do this conversion but could not get it to work, which was very good luck it did not work. Basically he assumed fitting the alternator, connecting the main output wire up and putting the belt on would allow it to work - it did not put a charge out because he had not used an exciter wire (hence the bulb & 12v + feed as above).
Checking through his (poor wiring skills) I found the main output wire from the alternator was wired direct to earth - unfused.
If he had managed to get charge out of the alternator it would not have been a pretty sight.

Dave.
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diesel_jim
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PostSubject: Re: 1 or 2 Alternators?   Thu May 07, 2015 5:59 pm

^^^^ YIKES!!! doh

That would have let the smoke out of the cables!
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Assassin
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PostSubject: Re: 1 or 2 Alternators?   Thu Jun 11, 2015 5:26 am

Marine alternators are basically sealed units and as such they can run filled with oil, fuel, water, and even mud. They do require maintaining but this is as simple as periodically cleaning with a hose to clear loose mud and debris, blowing with an air compressor to remove everything else, and spraying with the top up waterproofing spray. You then grease the bearings.
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