T-MAX split charge system/Electrics advice

[cmcmill01]

Looking for some advice, I have a T-Max Dual battery system in the LC which seems to be connecting and then disconnecting a lot when I drive about.
When I accelerate or driving at a decent speed the system connects, but if I slow down or brake the system disconnects the 2 batteries.
At first I thought that it was only disconnecting when I applied the brakes but actually it could be also slowing down to a stop without any braking.

So questions:

• is it the main battery isn't holding its charge and therefore voltage level, how do I check to see if it knackered?
  • What is the best replacement battery, Odyssey or Optima and which type for a 12v Petrol 80, big question!!!!
• When does the alternator stop supplying charge to the battery, I thought it would be all the time even when coasting or stopped?
• Any top tips on how to test to see if it is the brake lights causing some kind of fault that drags the overall voltage level down?
• Any thing else or seen this before yourself??

Cheers for any info
Craig

 

[AndyCook]

I would check the voltage output from alternator with engine running
You can do this by measuring the main battery voltage obviously
Sounds like the alternator isn't generating enough charge on engine idle.

What is the cutoff voltage for the t max split charge system? And can it be adjusted


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[cmcmill01]

I would check the voltage output from alternator with engine running
You can do this by measuring the main battery voltage obviously
Sounds like the alternator isn't generating enough charge on engine idle.

What is the cutoff voltage for the t max split charge system? And can it be adjusted


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Will do, what is the correct Voltage output from the Alternator??
From the T-MAX spec's it says "Isolator Switch-on Threshold: 13.3V"

 

[Towpack]

14 - 15v @2000rpm and 25 degC or 13.5 - 14.3 @2000rpm and 115 degC. This is from the FSM for the diesel versions but can't see why the petrol's should be any different.

 

[cmcmill01]

Right been out with multimeter, sitting at idle the voltage across the main battery is 12.5v and under acceleration it goes to 13.9v's, so this is the reason why it is disconnecting.
So does this point at a dodgy alternator???


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[GeorgeG]

*As described it is most likely the main battery does not hold charge and the T-max recognizes it as a hazard and shuts.
*I bet it's not the alternator from what you're saying
* And it's less like the problem to be in the solenoid of the T-max
The easiest way to check the main battery if you dont have proper tools to do so is just switch places with the aux one.
Now about which battery to get..The petrol engines dont need as much starting power as diesel ones so you can get pretty much any.Fot the aux if you get Optima then you would need an alternator booster of some kind. The Optimas need 15+volts to charge properly( full capacity) as they are AGM.They will charge at 14.2 as well but not preperly and it's not only they will not perform as we want but they often just die within the firs year of use.
Hope I was of some help here

 

[Towpack]

Either the IC regulator or the alternator itself looks suspect.

 

[cmcmill01]

So went out again and got one of the kids to stand on the accelerator to keep it 2000 rpm, and the voltage at the battery terminals is 14.52, as soon as it goes into idle it drops to 12.39volts, so from that you would think the alternator looks OK as its stick out the correct voltage, but the battery isn't holding it????

If it is the battery then looking for a good replacement PDQ, as off to France skiing soon with the LC and don't want any trouble with the family being there as-well!!

 

[GeorgeG]

If the alternator was bad it wouldnt show 14,5 at all. Something else is wrong. My guess is eather the main battery or the T-max solenoid. It happens often do drop under 13v when idling. Check the cables just in case if something loose or may be some dirt deposits.

 

[Dave2000]

Sometimes a battery will not accept a charge and the alternator at idle simply does not have enough output to overcome this. Just for the moment I would borrow a couple of batteries and re test, itdoes sound like a battery issue though.

IMO if you go the Optima route you will not need to alter your alternator to charge at 15v, 14.4 is sufficient. It is true that to fully recover an Optima then 15+ is better but for general use I would not be too concerned in fact, I would be more worried about running different 'types' and sizes of batteries. As evidence I offer that I run two Yellow Optima's in a Discovery for years, they are dual purpose battery which to be fair is a compromise IMO but, they worked flawlessly for me and the new owner up until the last contact which would have made them around 5 years old? I did change the alternator from the original IIRC 65 amp to a 100 amp version on the LR as I also used to parallel the two for winching and competition use.

The only thing I would add is that when Optima's were taken over a few years ago there was a rumour that quality control was....er....a tad poor at best. This led to all manner of excuses why they failed early in life, everything from poor charging voltage to the wrong colour solar flare!

regards

Dave

 

[GeorgeG]

Dave, his 80 is petrol so only one battery is needed to check Symply take the aux and put it in place of the starting one.

 

[Dave2000]

Dave, his 80 is petrol so only one battery is needed to check Symply take the aux and put it in place of the starting one.

I do not think that is relevant, I am unsure how the T max works but if it does what pretty much most other devices do then it parallels the batteries? So assuming the aux battery is good enough and starts the car the alternator will still 'see' the same fault and this will affect voltage, and perhaps it is this voltage drop that is causing the T max to drop out? I would if possible do a cell gravity check, if not then a load test might be more appropriate?

regards

Dave

 

[cmcmill01]

Good point, so the voltages I see at 14.5 is across both batteries, then decreasing until the t-Max disconnects, at which point I am only reading the voltage across the starter battery. It's really starting to bug the sh*t out of me now as I can hear the t-Max click in and out all the time when driving. Suppose kwik-fit could do this type of battery check, or even the AA??


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[Chris]

I bought one of these testers. Unlike the electronic type analysers, it puts a poper load across the battery. If it's at all hooky, when you apply the load the battery voltage drops like a brick. It has an element in there that basically heats up with the current. It's a compact version of the old prong type testers. Seems to work very well.

http://www.ebay.co.uk/itm/HEAVY-DUT..._Measurement_Equipment_ET&hash=item43aafb0a74

 

[Dave2000]

Suppose kwik-fit could do this type of battery check, or even the AA??

If kwik fit have replaced all their staff since I was in the UK about 9 years back then yes it is possible . AA was pretty good with stuff like battery/alternator testing. Can you get access to the battery cells, are they wet cells with lift or screw off caps? If yes then purchase a gravity meter, a couple of quid and you might find the problem yourself? An alternative it to fully charge both batteries and then disconnecting EVERYTHING let them stand for about 12 hours and do a voltage check.

Keep in mind they are NOT 12 volt batteries, that is a nominal voltage. So left say overnight I would like to see from a healthy battery at least 12.6 volts, anything less then the battery is suspect. I have re-read your posts noting the voltages and they are waaaay off at idle. So before we run off and replace batteries and 'stuff' we need a little baseline to work from.

Engine at idle and all non essential electrical loads off then your voltage should be as near as dammit 13.8 after a few minutes running, please confirm that. Of note is that it is even possible your fan belts are slipping at idle and at revs they are pulling the alternator up to speed and hiding the problem. Another point about V belts is they could be really tight and still slip, they are tight at the bottom of the V but not actually gripping the sides of the pulleys. Also Typex a white line across your crank pulley and harmonic damper if you have one, the rubber bonding can fail and allow the outer pulley (drives alternator) to not keep pace with the crankshaft. Sounds like a lot of faffing about but it helps forum members get some clarification as to what is and is not working, this will help guide your fault finding process. Bad earths on cables, loose terminals, have a good route about and get back to the forum.

regards

Dave

 

[fridayman]

If you don't get 13.4 or 13.5v at idle, your alternator is more than likely faulty. If this has been going on for some time (months) there is a good chance the battery has built up sulfation (which coats the inside of the battery and prevents good contact and voltage). As suggested, remove the main battery altogether and put the 2nd battery in its place. Then check the voltage across the battery at idle - is it around 13.5v? Turn the lights on at idle - what is the voltage now?

BTW 15v+ will harm most agm batteries. They charge best at 14.4-14.7v. If you use a charger that charges over 15v, make sure it has a thermal sensor and cutout or you could get gassing which generally can't be fixed on sealed agms.

Regarding the battery itself, what voltage does it settle at with the car off and the lights on? I've recently been playing around with a desulfator that I bought from a guy in SA. I was very sceptical at first but it wasn't a lot of money and I have some very expensive batteries that had taken a bit of abuse. After having a suspect Odyssey PC1700 load tested with 2 different carbon pile testers, it was only holding about 60% charge. So I fully charged it with a Ctek MXS25 ( for 2 days) then disconnected the charger and put the desulfator on it for 6 weeks, checking the voltage weekly to make sure it didn't go too low (but the desulfator draws almost no power). Then took it back to have it tested again. This battery is now putting out 1000cca versus its rated CCA of 875! Result!

 

[fridayman]

Actually one correction to what I wrote... The alternator will eventually settle at around 13.5v, but initially in start-up it can show as high as 14.2v.

 

[cmcmill01]

Cheers folks thanks for the replies and info, back at work tomorrow so will have to find some time to do the battery swap as the first option. Although might do some other voltage readings before that.
Will also have a look at the belts.
cheers
Craig

 

[Dave2000]

I bought one of these testers. Unlike the electronic type analysers, it puts a poper load across the battery. If it's at all hooky, when you apply the load the battery voltage drops like a brick. It has an element in there that basically heats up with the current. It's a compact version of the old prong type testers. Seems to work very well.

http://www.ebay.co.uk/itm/HEAVY-DUT..._Measurement_Equipment_ET&hash=item43aafb0a74

I have a similar version Chris, but now around 20 years old? Still works perfect, nowadays there are more modern devices out there and are very good at testing batteries but, you have to know the exact type/amperage of the battery for the test to be accurate, not always possible on something that has been around for a few years and the spec unknown, IME there is nothing like sticking a 100+ amp load across the terminals for a few seconds as a test ....and yes they can get hot!

regards

Dave

 

[cmcmill01]

So went to local kwik-fit (was driving past!!!!) they put some fancy Bosch battery tester across the batteries and they look to be ok, so think this points to the alternator??


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