Flat battery - dual battery system?

[p38arover]

I've been having problems lately with suffering a flat battery in the P38A if not driven for 2-3 days.

I tried disconnecting my dual battery system and the problem ceased.

I connected it back up, and I had a flat battery again today after not driving the Rangie since Sunday.

I now need to work out if it really is the dual battery system and, if so, why it's not disconnecting the second battery when the voltage drops. I need to contact the manufacturer for advice.

[mns488]

hope it doesn't end up in 'your ability to buy faulty' thread...;)

i have no idea about electrics:angel:

good luck with it.:)

[81stubee]

Ron,

Just before I took the motor out, I was having problems with the battery, until it went flat on me. I replaced with a new one and seemed fine... until the other day when I took the SC40 out of the range and put it into the BF Falcon RTV, so i could dual battery that for the fridge on our camping trip. Two days later the falcon had a flat battery and the aux battery was seemingly having trouble keeping up. Normally the fridge lasts at least two days.

So it may just be co-incidence but maybe mine was faulty all along too.

Stu

[p38arover]

Mine's an SC40 as well.

[100I]

I've just had battery issues over the New Year break too. It would not crank [was not early morning or cold]. On the first failure I put it down to earthing issues as I've had a problem before, so ran an extra earth to the block and took a long drive to charge up, yet still suffered a no start again the next day.
I did not have my multimeter with me to see what was going on. I left the fridge in the car when I got home but it started next morning no problem at 11.85 each battery. I'll check that again tonight.
Both batteries are as new [the auxilliary is brand new].
I have an SC40.

[Disco_owner]

Ron;

at a guess I would say , it sounds like you need to take your battery terminals off P38a and "Trickle charge" your battery with a battery charger , I did this to the Disco batteries as they were going flat regularly ,you're probably not doing long enough driving to fully recharge your battery.

[81stubee]

hmmmmm.... interesting.

Mine is all melted and sides have split, from the heat in the engine bay i guess, thats why i don't think it will be going back in. I don't have one here, but could you not put it on a variable power supply and see when the changeover occurs? This is how you were meant to test the dual battery kit from Jaycar that I built once upon a time. I was under the impression that they are a oneway flow (charging only).

Stu

[Nathan]

I've been having problems lately with suffering a flat battery in the P38A if not driven for 2-3 days.

I tried disconnecting my dual battery system and the problem ceased.

I connected it back up, and I had a flat battery again today after not driving the Rangie since Sunday.

I now need to work out if it really is the dual battery system and, if so, why it's not disconnecting the second battery when the voltage drops. I need to contact the manufacturer for advice.

Do you have a multi-meter? If so, leave both the batteries in and disconnect one of terminals from the auxillary battery and put your mm in line to test if there's any current draw when the vehicle is not running. You may have some sort of current leak...

Nathan

[drivesafe]

Hi Ron, how much driving time are you actually doing because it sounds more like a lack of charge in the first place, which is a very common problem.

The SC40 itself, while connecting the batteries together, will only draw about 130ma and less than 20ma once the batteries are isolated, so it’s not going to flatten your batteries if they fully charged in the first place.

If on the other hand, you have not been doing much driving then the batteries will self discharge very quickly.

[p38arover]

Hi Tim,

I drive only about 20 mins each way to/from work (Emu Plains-Springwood) plus any other miscellaneous running around. Being a shift worker, some of the travel is at night (lights on). As you know, the P38A is a pretty hefty electrical load and only has a 100 amp alternator on my model (should be big enough).

BTW, I've been working at Springwood Signal Box for the past 3 years.

This problem is recent, i.e., in the last month. I've had the SC40 fitted for over a year. The battery gets a periodical top-up with a 4-stage battery charger. Ditto for the sealed AGM battery in the spare wheel well. I want to check the voltage drop across the cable from the SC40 back to the second battery. It is possible the second battery is getting insufficient charge, too.

The thing I forgot to check this morning before disconnecting the SC40 was whether it had isolated the second battery. I'll reconnect it later this week - I'll be off for a week or so from Sunday (another eye operation on Monday).

I'm not blaming the SC40 - that's why I didn't mention the brand in the first post. I'm looking for ideas so I can investigate the problem. As you can well imagine, at the moment I cannot trust the car at all so I'm reluctant to drive it anywhere I can't get a jump start.

I had the calcium battery tested a few months back by the retailer, Alko Batteries, when I took the Disco in to have its 12 month old calcium battery replaced under warranty. They reckoned it was OK.

I'll go up to the local LR workshop tomorrow and borrow their battery tester and check both batteries - or go to Alko and have them test the calcium with their computerised tester. They might test the second battery for me.

Regards

Ron

[p38arover]

Do you have a multi-meter? If so, leave both the batteries in and disconnect one of terminals from the auxillary battery and put your mm in line to test if there's any current draw when the vehicle is not running. You may have some sort of current leak...

Nathan


Yep, got that sort of stuff - I'm an electronics tech. I've done that. The P38A draws quite a bit of current until the BECM goes to sleep, then drops back to about 50 mA. It is going to sleep as I've monitored it. Of course, it is possible that local RF interference is waking the BECM.

If needs be, I'll connect a data recorder across a current shunt and monitor the current draw over a 24 hour period. I've got both paper chart recorders and electronic data loggers that could do that.

I've also disconnected electrical ancillaries from the main battery to be sure they aren't causing the problem.

[p38arover]

hmmmmm.... interesting.

Mine is all melted and sides have split, from the heat in the engine bay i guess, thats why i don't think it will be going back in. I don't have one here, but could you not put it on a variable power supply and see when the changeover occurs? This is how you were meant to test the dual battery kit from Jaycar that I built once upon a time. I was under the impression that they are a oneway flow (charging only).

Stu

If needs be, I will. I have a variable power supply. I also built the Electronics Australia dual battery charger (the Jaycar kit to which you refer). It's on the shelf in my electronics workshop.

[drivesafe]

Hi Ron and thanks for not trying dump the SC40 it the #### but I don’t mind if people mention that they have my gear installed as it makes it easier to sort out the problem.

Because of where you are driving, I don’t think you are charging your batteries enough while driving.

That area is all 80kph between your place and Springwood so you may not be running at high enough revs, long enough to fully charge the batteries and slowly, over time, you are gradually discharging the batteries.

That’s my excuse and I’m sticking to it.

Seriously, I think your problem is the short drives. Try putting your battery charger on as much as possible, for a week and see if this solves the problem.

Also, see if your alternator is working properly, it just seems strange that everything worked well for a year and then you get a problem.

The SC40 is not going to cause the sort of problem you have and I would like to get your problem solved so keep me informed of any findings.

Cheers, Tim.

PS. your 100 amp Alternator is heaps big enough to run everything and charge your batteries.

[Mudsloth]

battery split and leaking? did it smell like seaweed? sounds like overcharging

[Nathan]

Hi Ron and thanks for not trying dump the SC40 it the #### but I don’t mind if people mention that they have my gear installed as it makes it easier to sort out the problem.

Because of where you are driving, I don’t think you are charging your batteries enough while driving.

That area is all 80kph between your place and Springwood so you may not be running at high enough revs, long enough to fully charge the batteries and slowly, over time, you are gradually discharging the batteries.


I think that was the problem I was having recently, just not driving enough (no SC40 involved) to fully charge the auxillary batteries. I've since got a CTEK charger and whack it on charge once a month overnight and it's never missed a beat.

Nathan

[p38arover]

battery split and leaking? did it smell like seaweed? sounds like overcharging

No, the battery is fine in that respect.


Hi Ron and thanks for not trying dump the SC40 it the #### but I don’t mind if people mention that they have my gear installed as it makes it easier to sort out the problem.

Because of where you are driving, I don’t think you are charging your batteries enough while driving.

Tim, I was thinking along the lines of the second battery not charging sufficiently owing to the long cable run and consequent voltage drop resulting in lower charge voltage at the battery terminals.

My thoughts are that with a lower terminal voltage on the second battery, perhaps it is draining the main battery. The second battery is an AGM and the main battery is a lead-calcium.

On one occasion about two weeks ago, I went out to the car 4 hours after driving home from Springwood (at 7am so the lights weren't on). When I turned the ignition on, there wasn't even enough power to operate the radio - it kept muting. It didn't dawn on me what the problem was until I turned the ignition to start the car. I thought it was the RDS system blanking the radio.

I think I'll double up on the supply cable. Also, I haven't done your other recommendation of running a separate negative cable. I've been slack and it might have now returned to bite me! I've been relying on the body to provide the return path. I think I had better run the negative cable at the same time.

It would be interesting to get a set of long leads for my DVM and check the potential difference between the negative terminals on each battery when the system is charging - and, in fact, the PD between the positive terminals.

These are the other reasons I haven't blamed the SC40. There are two many variables that need to be checked first. What are the voltages at which the SC40 connects and isolates the two batteries?

I assume that, when charging, there is a certain voltage that must be reached by the main battery before the second battery is connected. Equally, I assume that the second battery will be isolated once it falls below a certain terminal voltage. However, if the main battery falls below a certain voltage, are the batteries isolated?

Regards

[drivesafe]

Hi Ron, cut-in voltage is 13.2, so pretty well straight after you start the motor, the SC40 will cut in.

Cut-out is at 12.0 volts and in a normal situation, with two fully charged batteries, it will take anything up to a month or more before the batteries get down to 12.0 volts.

Although having a low Auxiliary battery will drain the cranking battery but this will take hours to days to pull the cranking battery down to the auxiliary battery’s voltage and if the auxiliary battery is below 12.0 volts, the SC40 will cut out when the cranking battery gets to 12.0 volts and at 12.0 volts, you should still have heaps of power left in the cranking battery to easily start the motor, even on the coldest morning.

I still suspect the continual short drives are the problem, this is what I call the Shopping Trolley Syndrome and is a common problem and one of the long term effects of Shopping Trolley Syndrome is that your cranking battery eventually holds less and less charge, which may explain why everything seemed to be working fine for a year and now the system is starting to show the results of Shopping Trolley Syndrome.

Again, try putting a battery charger on your batteries every opportunity you get for a week and see if this fixes the problem.

If your battery charger is big enough, ( 4 amps or more ) connect it to your cranking battery and it will eventually charge up both batteries, via the SC40.

Cheers and keep us informed, Tim.

[p38arover]

Thanks Tim.

My charger is a 16A 4-stage unit.

I've been thinking of adding an expanded scale voltmeter. Maybe I had better.

I'll keep you posted.

[waynep]

Interesting tale Ron.

I've run an SC40 in the Disco for about 3 years now - for weeks at a time the the wife just drives it about 5km to her work and back.
Never had a problem with a flat starting battery. Both batteries are Exide Extreme N55s - nothing flash.

The fact that the problem goes away when you disconnect the SC40 "circuit" seems to point to a problem on that side of things.

Have you tried leaving the SC40 connected to your main battery, but just disconnecting the second battery from the SC40 output ?
That would isolate it to being a problem with the SC40 itself or something with the second battery, or circuits running off it.

Mind you the SC40 seems pretty bulletproof so wouldn't expect an issue there.

[drivesafe]

Hi again Ron, I just read waynep’s post and that reminded me to ask you to check your voltage at the cranking battery after you have driven the RR for at least 15 minutes.

Say, next time you go to work, pull up and leave the motor running.

Pop the bonnet and see what voltage you have at the battery.

Measure at the battery terminals, not off an earth point in the engine bay.

Some of the Discos run at 14.7 volts and this really makes a difference at keeping the battery in a better state of charge.

Your RR may be running at a much lower voltage and this can easily cause the sort of problem you are having.

Just another suggestion.

[Pedro_The_Swift]

My charger is a 16A 4-stage unit.




but is it working?
:Rolling::wasntme::whistling:

[p38arover]

but is it working?
:Rolling::wasntme::whistling:

Bastard! :mad:

:D:D


The lights come on. :)

[p38arover]

Hi again Ron, I just read waynep’s post and that reminded me to ask you to check your voltage at the cranking battery after you have driven the RR for at least 15 minutes.

Say, next time you go to work, pull up and leave the motor running.

Pop the bonnet and see what voltage you have at the battery.

Measure at the battery terminals, not off an earth point in the engine bay.

Some of the Discos run at 14.7 volts and this really makes a difference at keeping the battery in a better state of charge.

Your RR may be running at a much lower voltage and this can easily cause the sort of problem you are having.

Just another suggestion.

Yes, I'll do that. The RR does a run a lower voltage than later cars designed for calcium batteries. This is the second or third calcium plus a new alternator in the RR (in nearly 7 years) - plus two in the Disco (in a year). I won't buy another calcium battery for the P38A.

[drivesafe]

I won't buy another.

You won’t buy another Alternator or another LR :confused:

[p38arover]

You won’t buy another Alternator or another LR :confused:

Calcium battery.

I checked the voltage at the battery terminals when I arrived at work - engine running 13.6 volts.

[drivesafe]

Hi mate and there is your problem.

At 13.6 volts, you are only ever recharging your batteries to about 75 to 80% each time you drive and your batteries are never fully charged, no matter how long you drive for.

This is a sure fire way to shorten any type of battery’s life.

13.8 volts is the absolute minimum voltage to be able to fully charge a battery and even then, it will take a lot of driving time to achieve a fully charged battery.

Before you do anything ( other than hooking up your battery charger whenever possible ) find out if you can get your regulator adjusted up to about 14.2.

14.2 volts is a good optimum level that will get your batteries fully charged in a reasonable time but will guaranty not to over charge them in hot weather.

Again, before you do anything, get your batteries on a charge. The sooner you do it the more chance you have of maintaining the batteries you have.

Again, keep us informed

[p38arover]

Are regulators adjustable these days?

[drivesafe]

Are regulators adjustable these days?

That one I can’t help you with!

[p38arover]

Oh, I forgot to mention the ambient temp was 36 deg C. Based on my hazy recollection of lead-acid battery charging, one should reduce the voltage as the temperature rises - negative temperature compensation.

I'll take another measurement after my run home after work about 11.30pm when it will be cooler.

[drivesafe]

Hi Ron, the temperature is not a factor in the voltage level of your alternator.

The voltage will be the same in the middle of summer and the dead of winter.

After 15 minutes of driving you will have the set output of your alternator and it’s too low.

Cheers, Tim.

[p38arover]

I checked when I got home from work last night, with the radio, interior lights, and park lights on - 13.78 volts. Whilst the ambient temp was only 25 deg, the underbonnet temp would have been much higher - if the alternator does have temp compensation.

I'm not sure that temp compensation would work in a dynamic environment like a car engine bay. We certainly used it at work when we had battery backup systems - and we had to take it into account when taking SG readings.

Silly me took the Mitchell's Pass route not the highway so I was down at 1000-1200 rpm for a bit of the trip.

I'll monitor the voltage over the next week.

[p38arover]

Curses! Whilst investigating the problems, and connecting up the charger to the second battery in the spare wheel well, I noticed a wet area around the battery tray. Hmmm.

I've just pulled the AGM battery out of the wheel well. It's leaked.

I thought they didn't leak and could be used in any position. It's a good thing mine was upright.

I've spent the last hour or so stripping it all out, neutralising the acid. wire brushing, hosing, and cleaning.

The LPG tank is in the wheel well, too, so it might need to come out for a check.

I think the AGM battery will have to go into the faulty goods thread.

[PaulP38a]

Hi Ron - I'd be very interested to hear how you got your 2nd battery installed in the spare wheel well, and any gotcha's. It's exactly what I want to do with all that useless space under the floor. Well that, and maybe a spare air compressor...

[Scouse]

Paul, now that you have a 4.0, you won't have a subwoofer in the N/S/R 1/4.
Years ago, we fitted 2 batteries in there (stacked) for a LR car on the 1996 Calvert trip.

[p38arover]

The battery is cracked on the bottom of the case. It looks like it only lekas when it is taking a high current charge.