split charger system on a 200tdi discovery

[muddy4x4xfar]

hey all , im in the process of re-building my discovery 200tdi.

im currently thinking of fitting an auxillary battery to it as ill be running alot more i.e winches etc.

but i was just wondering what split charges you guys use and whats recommended. ?

ill be running a 100 amp alternator also if this makes a difference,

im kind of in the process of learning electrics so thats why im asking you guys what your recommmendations are?

many thanks

chris

[zardos]

I would recommend not to use a split charge system for winches as your wasting a lot power power potential, they are only really useful for running stuff when you engine is not running e.g. fridges and other electrical camping related equipment.

They also create an additional failure point as winching can cause them to have to switch high current loads frequently.

If you need the best of both worlds - e.g. winching and running a fridge then go for a Voltage sensitive relay (VSR) with a manual bypass switch using a chunky (250A) battery isolator.

This means that when winching you can use the power from both batteries and the alternator to power the winch (with the VSR bypassed)

When in camping mode the fridge won't be able to flatten you start battery.

If ever flatten you start battery but not you aux battery you can connect the 2 easily to start the car.

[muddy4x4xfar]

I would recommend not to use a split charge system for winches as your wasting a lot power power potential, they are only really useful for running stuff when you engine is not running e.g. fridges and other electrical camping related equipment.

They also create an additional failure point as winching can cause them to have to switch high current loads frequently.

If you need the best of both worlds - e.g. winching and running a fridge then go for a Voltage sensitive relay (VSR) with a manual bypass switch using a chunky (250A) battery isolator.

This means that when winching you can use the power from both batteries and the alternator to power the winch (with the VSR bypassed)

When in camping mode the fridge won't be able to flatten you start battery.

If ever flatten you start battery but not you aux battery you can connect the 2 easily to start the car.

hi cheers for reply how would i got about charging both batteries with out a split charge system off one alternator?

cheers

[zardos]

Just connect them together permanently.

e.g.

Wire the negative to negative

and

positive to positive

you now electrically have a single battery of the combined power of both batteries, no change to the charging system need, this is really the simplest way to do it (make sure you use suitable size cable, I would go for at least 50mm^2)

[muddy4x4xfar]

brilliant , i didnt realise it was that easy , thanks guys

[lyron]

yes, many thanks for that information, never thought of doing it that way.

[Maverik]

I think I'm going down this route too with the black Disco, put an isolation switch in the circuit too so I can always take the 2nd battery offline for normal use.

Mav

[zardos]

If anybody is interested I can give a more detailed electrical explanation of why a split charge system is pointless for use with Winches.

Also note that I and others that I know have been using this type of setup in competition for 6+ years, with winches that can draw up to 2500A in theory and never had a problem.

Just remember you should not use your winch for extended period of time under heavy load without the engine running (this should be an unlikely scenario)

[fozsug]

If anybody is interested I can give a more detailed electrical explanation of why a split charge system is pointless for use with Winches.

Also note that I and others that I know have been using this type of setup in competition for 6+ years, with winches that can draw up to 2500A in theory and never had a problem.

Just remember you should not use your winch for extended period of time under heavy load without the engine running (this should be an unlikely scenario)

Yes please, i would be interested.

[zardos]

First off the primary design of a normal vehicle electrical system is for the car battery to only provide power to start the vehicle. Once the engine is running the alternator is the primary source of power.

It does this by having a higher voltage output (usually 14.4v) and the alternator will maintain this up to around it's rated current draw (100A in muddy4x4xfar's case)

This is why as vehicles have been equipped with more electrical items (heat rear screens, head front, screen, heated wing mirrors, heated seats, etc ...) the alternator output has been increased.

e.g. a LandRover series with few electrical items would have had a 45A alternator/dynamo, where as a current model Disco or Range rover is likely to have at least 120A alternator.

The battery will only provide power if the voltage has been pulled down by a load that is greater than the alternators rated output.

With a single winch motor that can draw between 500A and 0A depending on the load of the pull, it is easy to pull the voltage down enough for the battery needing to assist the alternator.

So there are a few different ways of implementing a split charge system but all are designed to allow the higher voltage output of the alternator to charge 2 separate battery bank(s), but when the alternator is not supplying power (engine not running) then the 2 battery banks are separate.

They all do this using the fact that the alternator normally has a higher output voltage (unless the current draw is above it's max output)

So I will focus on the most common way of implementing a split charge system using a Voltage Sensitive Relay or VSR for short as this is simplest to understand.

The simplest VSR will connect the 2 battery banks (here after known as vehicle and aux) together when voltage on the vehicle side is above it's set level (Normally this is around 13.3V)

The load (the winch) will be connected to the aux battery.

So with the engine not running the voltage on the vehicle side should be around 12.8V from a fully charged battery, thus the two battery banks are separate as there is no charging happening, the load cannot flatten your vehicle start battery.

With the engine running the voltage on the vehicle battery side should be around 14.4V from the alternator, thus the two batteries are joined and the charge from the alternator is split between them.

So for use with winches, there are two different scenarios.

1. The current drawn by the winch is below the alternators rated output.

All power is provide by the alternator as it will still maintain it's higher voltage and thus the vehicle and aux battery will remain connected.

So VSR is doing nothing, so no point having it in this scenario.

2. The current drawn by the winch is above the alternator rated output.

The voltage of the system will drop disconnecting the two batteries (the relay will have to disconnect a load equal to the alternator's output, switching a high load will shorten it's life)

Now you have now lost around two thirds of you electrical generating capacity (say 100A hours from alternator, 100A hours from the vehicle battery, leaving you 100A hours from the aux battery), this will seriously affect your winches performance and it will slow.

But once the winch load has been disconnected from the vehicle battery and alternator, this side will quickly return to 14.4V thus reconnecting the two battery banks and immediately having to supply a high load (again this type of switching will shorten the life of the relay)

This connect/disconnect cycle can happen many times a second when winching, thus leading to early failure of the VSR relay.

There are less common ways of wiring up split charge system, using more exotic parts that can overcome some of these problems but all have the same drawbacks listed below:-

• They all add complication and an extra point of failure
  
• They all decrease the performance of the winch by removing a power source (you are just carrying dead weight of a infrequently used battery)
  
• Their primary goal is to allow you to start you engine, but when you are winching your engine should already be running
  
• The parts used have to be rated significantly above the alternator output and these can be expensive.
  

Hopefully explains why a split charge system is not suitable for use with winches but very suitable for use with running fridge, etc when the engine is not running.

[Bowie69]

All good points, well made

One thing about having a split charge is that if you flatten the car battery, or you can't get the engine to start, you only have a chance of flattening the one of them.

Engine stops -second battery is still charged, you may be able to winch yourself out of a situation to enable you to work on the engine.

Lights or something left on in the truck overnight -flat vehicle battery, one switch to connect the two batteries together with the relay and you get it started immediately.

This is assuming you are using something like X-Eng's solution, which is a 200A non-VSR relay, and just uses the alternator sense wire to decide whether to connect the two or not (you could use the oil pressure switch too).

[zardos]

I agree that a split charge systems has many other good points but the main design goal is to ensure that engine can be started after a load has drained the aux battery when the engine was not running.

With a bit of extra complication you can have the best of both worlds using a split charge system with a manual bypass that directly connects the battery for use when winching.

I would still class something like X-Eng's X-Charge product as a voltage sensing relay, just it's switching voltage is determined my the minimum voltage require to operate the relay coil, this will normally be at a lower voltage than a proper VSR.

And you could with the engine running still cause the the two battery banks to be separated (very dependant on the relay used as to when it would separate the two battery banks)

And with a lower disconnect voltage 200A might not be enough

e.g. with a single motor winch connected to the aux battery and drawing 500A you will get in theory 100A from the alternator and 200A from each battery, thus the relay would need to handle at least 300A (there so many factors that the actual current supplied from each component could be higher or lower)

You could also swap the winch load to the main battery/alternator and configure a relay / other switching mechanism to protect the aux battery from draining to much when winching, but this is very complicated to get right automatically (easier with a manual switch)

In this setup it would be better as you would only loose one third of your power generating capacity, but it would be much easier just to carry one of these small jumpstart packs, and use all of you main batteries for winching.

Also to note that not having a split charge system is better for your batteries as well.

Batteries come optimised for two different discharge patterns:-

higher discharge rate, but to a lower discharge depth (normal car batteries)

lower discharge rate, but to a higher discharge depth (leisure batteries)

Which type do you choose for your winch batteries, where you want high discharge rate and depth?

If don't have a split charge system, then the load is split between multiple batteries and the alternator, therefore each battery will be discharged at a lower rate and they will be at a higher state of charge at the end of the winching operation.

We all know that flattening lead acid batteries is bad for their lift span and that an alternator does not have a "charged state" to affect.

This is why a lot of people are using twin alternator setups as this will reduce then need of battery power when winching (it won't increase your battery recharge rate though)

[vulcan bomber]

No split charge setup beats 2 alternators.

Gives you 2 seperate electrical systems that can be joined via the battery possitives with a big isolator...

That gives 2 alts and 2 batterys to power your winch.

[zardos]

Yes, sorry I meant 2 alternators and 1 or more batteries with no split charge.

or some people go for

2 alternators, one 12v with one battery, one 24v with two batteries (2 12v in series to give 24v) as using 24v has some advantages but also adds complications and has a few disadvantages as well.

The are lots of different ways of doing things

[UdderlyOffroad]

Plenty of threads on this and other forums debating the merits of various split-charge systems. There is no 'right' answer to this one. It depends on your intended application.

My take on it (given I haven't actually got to that stage in my rebuild yet!):

VSR or split-charge relay, essentially it's a case of tomato/tomato. All it does is sense the engine is on and charging, and connects the two batteries together. It's only how it determines the state of the engine that differs. Either way, even an 'HD relay' may not be suitable for connecting the two batteries together when winching...the potential to draw large currents across the relay contacts will shorten its life.

I want my split charge to do both, i.e. let me run camping kit without discharging the starter battery AND be additional power available for winching or jumpstarting. Therefore, I'm going to fit an suitable relay to connect the two batteries when the engine is running, but also have a suitable rated manual switch (this one) to allow me to connect them together. Actually it'll do more than that, in that I can join both batteries, or select which battery powers the winch. To top it all off, the split charge relay can be manually switched via a Carling switch on the dash, and a voltmeter can monitor both batteries.

The two alternators option is there, but frankly to my mind it's mechanically complicated, and imposes additional load on the engine that will reduce power available to the gearbox. I think your typical alt requires about 2-3 HP to turn - so why have two alternators sapping power at half load all the time when you could have 1 alt sapping power at full load when required. Overly simplistic I know, but you get the point.

Which might sound ridiculous, as I've no intention of building a challenge truck (it's a 110, FFS!), but let's face it the 200 Tdi doesn't have that many HP to spare...your mileage and application may vary...

[zardos]

UdderlyOffroad sounds like you are going for the "best of both" solution I outlined in my first post (with some additional bells and whistles ) and I think is ideally suited to your needs

As for the second alternator option, Gwyn Lewis now does a kit for all LR engines making it mechanically simple to fit and an alternator requires very little power to turn when it is not supplying any current (barring a small amount of friction the HP required is related to the current provided, so 2 alternators producing 50A each is about the same as one alternator producing 100A)

[mahon257]

My home made (adapted from an IBS system and milkfloat parts) does everything... winching, car starting, runs a freezer etc... It is complicated, and has more points of failure that a standard system... but for me it was a bit of fun...

Here is the write up: http://forums.lr4x4.com/index.php?showtopic=58098

[Team Idris]

No Diode pack mentioned though? I've been very pleased with mine

The starter battery is in the engine circuit, the aux-bat is in the winch circuit, and as as far as they see it, each batterie has its own seperate charge from the diode pack. But in reality they both get the amps from the same alternator.

Whichever is flattest sucks the most power. Neither can flow back into the other and no contactors to burn out. I have anderson plug jumpers for emergencies. And theory and measurement say I need a higher voltage regulator to overcome the diodes, but it tests fine with the standard regulator. So far it has been one of the better bits I bought

[zardos]

A true diode pack, was discounted as nobody tends to use them nowadays as they usually have a large voltage drop of 0.8V - 1.2V.

But there are some modern "diode packs" that a really other clever and complicated electrical circuity to do the same work as a diode pack but without such a big voltage drop.

And even these get up to a 0.2v drop at 160A level.

[Igol]

I'm kicking around the idea of adding a second deep cycle battery to power a heating band on the fuel filter for the winter months when the old bus doesnt like eating veg oil.

And for the nay sayers; yes I know that using veg oil means that I will be condemned to hell and my car will turn into Christine and go on a killing spree that I'm responsible for.

As with previous poster I'm thinking an isolator to prevent the battery charging when the band wont be in use and a switch to turn it on 10/15 mins before I need to go anywhere.

[Team Idris]

Marine Split Charge; The split charge diode is the common item on canal boats, where there is one starter battery and four domestic batteries (Deep Cycle). The operator could be just hiring, or an owner, but is usually no more technically minded than any car driver. The diode pack offers the installer a fit and forget solution that gets on with the job without service. As opposed to a realay which can connect one well charged starter battery to four very flat deep cycle batteries. These would typically be tractor size, so a 50 amp relay isn't going to last long. The split charge diode though, only see's the maximum output of the alternator. To get over the 1.2volt drop a higher volt regulator is fitted, but the batteries only see a normal charge voltage. In reality they throw the standard regulator and fit an external unit with a variable voltage. This allows for full charging of the batteries, which the standard regulator isn't so good at. I've took a leap and just fitted the diode pack, but the regulator change is on my list.

For systems where there is a risk of flattening the aux battery and a need to have it fully charged as quickly as possible the external regulator is a good idea. But any automatic split charge system isn't as cheap and simple as a red key you throw once the engine is running.

Personally I like a seperate winch circuit that leaves the starter battery well charged, as we have been left up a steep bank with a no power unable to do anything. Terry managed to get the free wheel out and I bumped started it on the way down so I had brakes. Exciting

[bushwhacker]

Excellent information zardos, and the others.

I'll need a few reads to take it all in but it's very helpful.

Thanks.