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1995-2002 Range Rover P38A
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Discussion Starter #1
Hi,

I need to increase the amperage for starting . I can't fit anything other than a 90amp battery with the available spsce & the p38 diesel needs about 110amps. If I fit another smaller battery , say 12v,30amp, behind the EAS valve block with it's +ve connected to starter supply and -ve to a suitable earth point, will it serve my purpose without issues( charging etc,...)?

rgds
 

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1970-1995 Range Rover Classic
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i think you will need atleast 900 CCA to start that. I have a 1000 CCA battery in my 4.6L V8
 

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1,340 Posts
First, we need to get the facts straight: a battery has several numbers to describe it's performance.
- the capacity of a battery is expressed in Ah (not amp), meaning it can store the energy required to provide a current of x A for y hours, giving x*y Ah. For a P38a the capacity is 70-95Ah, but you can fit up to 110Ah (as I have done), depending on the brand and type of battery.
- the maximum current a battery can provide, is the CCA or cold crancking amp, at 0°C. This should be at least 700CCA and determines the maximum power the battery can provide. This is more important for winching than for starting, as a winch can have a higher current draw than the starter motor.
- the actual current required by the starter motor will be 100-200A, depending on temperature and condition of starter motor, power cables and complete engine.

The 90Ah battery you mention should be plenty. Adding a second smaller battery will do little good, because of the losses when connecting 2 different batteries. You will also need a separate charging circuit for the second battery, simply putting them in parallel will lead to currents from one to the other, resulting in battery drain and after a while battery damage.

If you have problems starting, start by checking the power cable and earth to the starter motor. Also make sure your battery is still in good condition. You should have no need to upgrade your battery beyond 90Ah, unless you require extra capacity for a fridge or other gear when traveling/camping.

Filip
 

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1995-2002 Range Rover P38A
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973 Posts
Discussion Starter #4
It's a 90AH battery & does not say anything about CCA. The battery shop has only a 90AH battery that will go with the P38 battery compartment. The next size is 120AH and it's too big & cannot insert. I don't have a winch or fridge etc etc. Issue is that the manual says the p38 diesel should have a 110AH battery. That's what I'm trying to meet with the additional battery.
quote;

Adding a second smaller battery will do little good, because of the losses when connecting 2 different batteries. You will also need a separate charging circuit for the second battery, simply putting them in parallel will lead to currents from one to the other, resulting in battery drain and after a while battery damage.

unquote.

Pls explain me
1. how a current flow between batteries is possible when the volatge of both batteries equal (12v).
2. Since both are in the path of the alternator output, why the need of a seperate charging cct

rgds
 

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Normally every battery should have the CCA listed, but it doesn't really matter, so don't worry about it.
Over here most diesels use a 90Ah battery because that's what's readily available and fits. And they do just fine.

1. A battery never gives exactly 12V, it can be as much as 12.8V or a lot less if old/drained. Which also means 2 batteries will never be exactly at the same potential, hence currents will occur between them and in the end drain and damage the weakest one.
2. When I said you needed a different circuit, I did not mean a different alternator. But as you can't just put both batteries in parallel (see 1.), you'll need some sort of switching, either an intelligent charge circuit or at least an ignition controlled relay to isolate one battery when the alternator isn't charging.

Most important, you will have very little advantage from adding a second small battery, even with the above precautions. You do not need a bigger battery for starting, it only means you have some more capacity. So a good new one of 90Ah would already be better than an old 110Ah.
 

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I've recently installed Yuasa 100Ah 1000CCA battery. P38 diesel needs very good battery for starting on hot engine. Poor battery will cause long cranking before it starts.
Also earth leads needs replacing on theese vehicles due to big losses.
New 1000CCA battery and new engine earth lead fixed all my problems with starting, now it starts after half a turn of the crankshaft.
 

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1995-2002 Range Rover P38A
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973 Posts
Discussion Starter #7
I've recently installed Yuasa 100Ah 1000CCA battery. P38 diesel needs very good battery for starting on hot engine. Poor battery will cause long cranking before it starts.
Also earth leads needs replacing on theese vehicles due to big losses.
New 1000CCA battery and new engine earth lead fixed all my problems with starting, now it starts after half a turn of the crankshaft.
Hi,
What is the code for that battery? Was it an exact fit or you had to adjust the compartment?

rgds
 

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Yuasa cargo 640, it's exact fit.
It has central terminals, but battery leads are long enough to fit.
 
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