2nd battery charging
 

We are planning to fit a second battery to our land rover for our drive through africa. I see you can either spend £40 on a basic diode or £200 on a 'battery management system'. can anyone tell me which is better?
Is it a case that the diode just splits the charge and isolates the batteries and the managment system directs the charge more effectivly?
Thanks
rob


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www.longroadtripnorth.com

Or a split charge relay at about 20 quid

Or a boat switch at about 40 quid

From memory the diode system create quite a large loss

For cheap battery management systems start your trip in south africa (wonder how much you would save by shipping the vehicle to SA, buying all the gear and then driving back to the UK - probabily enough to pay for the shipping)



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Rich
LR101 300Tdi Ambi 'Tiggurr'

I have 4 batteries (24 volt Toyota) with a "basic" diode block. Works perfectly fine. Solid state, cheap (30 euro), rugged, made for the purpose. The diode block looses 0.7 volt over the diodes causing some warmth but it has cooling fins for that. No worries maintenance free etc. Install and never have to look at it again! All the fancy stuff breaks down.

Cheers,

Noel

[This message has been edited by noel di pietro (edited 25 July 2005).]

Hello Noel,

There's plenty of info on the web about split charging, also on the drawbacks of diode based circuits. Because the diode drops charging current, the battery is never fully charged and works below its full capacity. All it means means is that you carry around a piece of equipment that weights a lot yet doesn't serve its purpose. If that doesn't bother you, fine. If not, I'd recommend more refined solutions. You can find out more here: http://www.hellroaring.com/nodiode.htm

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Roman (UK)
www.overlandcruiser.info

I still prefer a relais that switches as soon is the alternator kicks in (cause I will forget the manual switch).

The diode indeed takes 0.7 volts, what in 12V set up is considerable if you ask me (in a 24V set up that's only 0.35V a battery...)

Robbert,

This is precisely why commercial/utility vehicles are fitted with 24V circuitry. If you take good care of your truck, it may live long enough to be rewired for 48V.

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Roman (UK)
www.overlandcruiser.info

on my 300Tdi 90 i have twin alternators and twin batteries.

This works perfectly, one battery and alternator runs the vehicle, whist the other does the winch.

this way, if either alternator packs up, i can switch the link switch and join botehr batteries together and carry on.

The only down side is that you can't easily fit anything else on the engine, like AC or air compressors (like i've got waiting in the garage), so i might well be converting to the diode type splitter soon!

Hi Roman,

Theory and practice! I have dual voltage indicators and while the motor is running they always indicate between 28 and 30 Volts charging voltage. Seems enough to me! What is 0.7 V on that! And the TLC only has a 30 Amp alternator! Never had any problem with insufficiently charged batteries. I run a compressor fridge, lights, laptop, 500 watt 24V/220V converter etc. No problemo todo !!

Cheers,

Noel

We shipped my Toyota over from the UK last July and within 2 months the Lucas split charge solenoid had packed up and I was unable to get a replacement.

I have since reused the wiring and just installed a simple manual switch to separate the two batteries when I've parked up for the night.

Its simple to close the switch at the end of day vehicle check and open it again in the morning's pre-drive check. Simple.

If you buy any other sort of "device", buy two and the bring the second unit as a spare. It's a real pain in the arse to find both batteries flat in the morning and you're not parked on enough of a slope to bump start the vehicle.

@Roman,

On 48V I'd better drive my truck (Lada 2104) electrically. Can get rid of the engin, throw a solar panel (with charge mgt off course) on the roof, and just avoid those winters at +60°N.

Sounds like a good id, but first that trip around the Caspian. I heard petrol is cheap there anyway.

That is what I mean, what Bundabasher said! Solenoids are no good, they have moving parts and burn their contacts. A diode block as no moving parts. My diode block can handle 70 amp and the alternator supplies max. 30 amp. So it is heavily oversized and therefore as reliable as the Toyota itself!

cheers,
Noel

Noel,

Are you sure the alternator on your TLC only produces 30 Amps? The specifications on mine says it is "rated at" 80 Amps. I'm not completely sure whether that means it actually pumps out 80 but it might.

I agree Redhouse,the TLC alternator should be 80 amps as standard(maybe it looks like 30 when covered in muck!).
And Dieseljim's dual alternator setup is really the tops when it comes to reliability and having a backup charging system.If you've got room,i'd certainly reccomend shoe-horning a small Jap alternator in there.If you go along to your local scrappy and have a look at some of the small hatchback Jap cars,you should find a tiny alternator that'll do the job.Don't be put off by how small they are,the rating is usually very good as these cars are designed for lots of short journeys so need to be able to keep their batteries charged.If i had room on my camper i'd have one,but as it's so tight i've rigged up a 40amp relay on a manual switch that's only energized by having the ignition key turned on.That way it does'nt matter if i forget to turn it off! Well it's simple and works,and best bit of all is the cost...£2.10p

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Just going for a short ride on my bike....

My Iveco has a bank of relays activated by the little wire coming off the alternator that heads off into the dashboard for the charge light. The relays activate things like the spots, aux batteries, fridge, power ampli (before it got nicked)

The system's only weak point seems to be corrosion in the push on connections.

A second alternator looks like a good idea, particularly on 24v vehicles, preferably with an independant drive belt.

For those who only have one accessory mount or one spare groove on the drive pulley, Magnetti Marelli make a few models of alternator with an aircon compressor integrated in the same casing (mounted on the smaller Fiats, Renaults and Citroens)

Happy scrapyard hunting!

Luke, that sounds like an interesting option - any idea what models to target at the scrappie ?