youmitegetian

youmitegetian

Active Member
As the title suggests, I’m interested in fitting a second battery as I do very short journeys and the battery doesn’t stay fully charged for long, it’s a new battery and the car doesn’t have a parasitic drain, I guess it’s because I’m usually driving when it’s dark and have the heaters and seats etc on.
 
youmitegetian said:
I guess it’s because I’m usually driving when it’s dark and have the heaters and seats etc on.
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Then a second battery is not going to help. All you're going to do is delay the inevitable.
Are you certain that the new battery is good, they can fail early.
And are you absolutely certain nothing is waking up and draining it.
Even with the seats lights etc etc on, the alternator should be able to cope.
What sort of time are we talking before it won't start?
 
I figure it’ll buy me enough time to charge it up maybe once a month,
I’ve got a pretty good drop tester so confident the battery is good,
And tested for a parasitic drain and all seems ok.
I had a new battery on my other rangie that’s only a year or so old, it’s still okish but weak hence why I’ve got another new one.
That car did the same thing.
Basically it still starts but can tell it’s getting low as the hdc inactive message comes up,
I wanted to start using the aux heater for the cold mornings but fear it will go to flat to start fairly quickly.
My commute is under 3 miles so only runs for about 5 minutes twice a day and other odd trips but I’m guessing it’s just not running long enough to put back in the power I’ve used on such short trips
 
Not sure what the alternator output is on yours but I'd be guessing at least 120 amps.
So, let's imagine a start is 350 amps for 5 seconds, that's 0.1ah gone so even at idle speed, that should easily be replenished in about 1 minute or less.
Now, let's guess at 250 Watts for lighting, that's about 20amps.
Heater uses very little (fan) so let's guess another 5 amps.
Heated seats, again, not sure but I can't see it being more than 30 amps.
Let's chuck in another 20amps for other ancillaries and we end up with a total demand of 75amps.
So you see that even with everything on, the alternator should be feeding everything and still have plenty spare capacity to be charging the battery.
I believe you would be better to find out why it doesn't cope rather than messing about with dual battery setup.
 
Hmm when you put it like that.....
I always thought it took a few minutes driving just to replenish what it took to start the car.
Battery voltage with the engine running is close to 14 which sounds about right to me but I could be wrong
 
The voltage isn't the only thing to consider. You need to check the current output of the alternator.
My math above is a bit of guesswork and there are lots of things that will affect it but no, the energy removed from a battery by a standard start should be replaced within a minute or two and the alternator should be capable of feeding all loads on the car with some in reserve for topping up the battery.
If you're absolutely convinced nothing is waking up then I'd be getting the alternator load tested.
 
Can I load test the alternator with a multimeter?
How would you go about testing for a drain?
I googled it and followed the instructions, can’t remember exactly now but it involved disconnecting the negative lead from the battery
 
Might be easier to get one of those solar trickle charger jobbers that plug into the cigarette lighter.
 
I did look at those but think from memory the output was poor unless you have a panel to put across the whole screen
 
youmitegetian said:
Can I load test the alternator with a multimeter?
How would you go about testing for a drain?
I googled it and followed the instructions, can’t remember exactly now but it involved disconnecting the negative lead from the battery
Click to expand...
No, you can' load test the alternator with a multimeter. The only certain way is to get it on an alternator tester (Generally off the car) that can vary the load and speed and see what the max output is from it.
I have, in the past, fitted a flat battery, jump started it and then put the clamp meter on to see what's being put into the battery. Theoretically, if all other electricals are off, the battery should receive the full output from the altermator until it approaches fully charged.

You can test for drain by putting a multimeter in series with the battery but unless you want to sit there for 24hrs watching it, you only know what it's doing when you test it. Some higher end multimeters have a max/min facility so that you can see what the maximum demand was. The problem is that if it's a heavy user that's waking up, it might be more than the meter can take. I personally don't like the series method as it's very possible to kill your meter. Much better with some non contact (Clamp meter type) measuring really.
There are a number of mobile phone/PC based 2 channel oscilloscopes on the market these days which with the right leads can be used to log currect and voltage at the same time and they're not silly money but probably beyond many home users and not worth it for a one off.
 
Marmaduke said:
Might be easier to get one of those solar trickle charger jobbers that plug into the cigarette lighter.
Click to expand...
Don't think they would work as the fag lighter needs to be a permanently live one. Also, i would guess the fag lighter on the L322 is fed via a mosfet device and bangine 12V in the other way is sure to screw things up.
And, yes, unless it's very sunny, it ain't going to do much.
 
Wazzajnr said:
Don't think they would work as the fag lighter needs to be a permanently live one. Also, i would guess the fag lighter on the L322 is fed via a mosfet device and bangine 12V in the other way is sure to screw things up.
And, yes, unless it's very sunny, it ain't going to do much.
Click to expand...
OK point taken, l'll climb back in me box
 
Marmaduke said:
OK point taken, l'll climb back in me box
Click to expand...
You could of course wire in the solar panel via a fuse and solar controller to the battery but again, there wouldn't be enough output to cope with even a sleeping range rover unless it was a fair size and we didn't live in UK!
 
@youmitegetian

Hi

don’t know how much they compare , just finished fitting a split charge system on mine , found a chart if it may be of any use to u regarding residual drain when it’s asleep

also spent ages testing everything , did follow a good link, maybe @Wazzajnr might be so kind plse to see if it’s any use to u , ( hope that’s ok in me asking plse )

mines power hungry and takes a while going through everything , had to make sure there was so untoward drain before fitting the second battery and the alternators ac side was ok , i sometimes leave mine standing for a good few weeks or short journeys

hope out of this u may find a little bit of useful info, just know what a pain it is having a flat battery , lol

https://www.disco3.co.uk/forum/robb...ent-drain-testing-119574.html?highlight=drain

https://www.landyzone.co.uk/land-rover/split-charge.324504/

B477B829-8E75-4D6A-A4F5-9FA505A50E6D.png
 
That’s useful thankyou, I might take it to my mate who runs a garage as he will have the correct equipment rather than risk frying my mulitimeter, but with that info he will know more about the sleep time etc,
 
youmitegetian said:
That’s useful thankyou, I might take it to my mate who runs a garage as he will have the correct equipment rather than risk frying my mulitimeter, but with that info he will know more about the sleep time etc,
Click to expand...

hopefully it will be of some use, i followed the link ref residual drain and tested everything myself, of course not as accurate as garages but i have got decent meters , maybe the info will be no good with the possibility of different systems , but at least the residual chart gives an idea of what the drain should be

did actually buy myself a volt meter that i plugged into my cig lighter , which at least gave me a rough indication what the volts where whilst driving , alas not 100% accurate as it’s not at the battery



39E874A4-8916-40BD-8B7E-BB361090E6F5.jpeg
 
Yep, all good info. Not sure about the voltage drop across the fuses as it's not guaranteed that they are all made the same so it will work to find stuff drawing amps or more but for mA ranges, I'm not convinced.
Apart from that, it's a very good write up.
 
Wazzajnr said:
Yep, all good info. Not sure about the voltage drop across the fuses as it's not guaranteed that they are all made the same so it will work to find stuff drawing amps or more but for mA ranges, I'm not convinced.
Apart from that, it's a very good write up.
Click to expand...

hi

knew from ur replies u knew what u was talking about , good that at least it gave the basic info regarding how to test for residual drainage, which hopefully will indicate of any untoward mv

these are the meters i’ve got, know there not a substitute for the ones used in garages , was worried at first my vdc went up to 15.6 volts but then found out my alternator is supposed to be ones of these smart monitoring and is normal , see there even more complicated on the D4s

also found the diagnostics reader i bought very useful when trying to see what the electrical side it doing

thks again

EAC01AAB-EB4D-4862-BD1F-1085ACBF9F0F.jpeg
46E16C9B-7E80-4923-892F-77B0AE520F98.jpeg
E50B4C4C-2789-4EEE-AF2A-81556FE478C2.png
 
youmitegetian said:
Interesting it shows 14.9 while running and at the cig lighter, mine shows less at the battery,
Click to expand...

mines will go up to around 15.6 volts but i believe the alternators are different

that’s why i didn’t wish in one way to try and confuse matters, lol

do u know what ur supposed to get with the engine running with everything then turned on

ie , start with the engine off see what the volts are at the battery

then engine running recheck volts

whilst engine running , turn everything on, lights etc and recheck again what the volts are

if unsure get ur mate to go through everything
 
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