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Maintaining electrical charge


Paul64

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Hi,

Any ideas would be appreciated.

Driving back to Transylvania. All going well until I slept in the LR overnight in Hungary. In the morning starter clicking but not enough power to start. Lorry driver jump started me to get me back to Romania. Stopped and started engine 3 more times that day, no problem. Following morning same starting problem.

I have x2 batteries under the seat. They are not split charged but connected together. One mainly for the starter, the other for nearly everything else.

Only changes recently are upgrade to 100W headlight bulbs which were on all day in Hungary.

Anyway, I swapped one of the batteries to get LR started. Reading from both batteries with engine running was 12.8V (too low I know)

Earth lead from battery to chasis and chasis to gearbox cleaned. Charge went up to 13V with engine running.

Belt to alternator new and tensioned properly.

Local auto electrician changed x1 diode as faulty. However, no increase from 13V charge resulted.

Again this morning both batteries drained. When disconnected one read 9V and the other 5V. When connected 6.6V. However, before going to bed the night before both were just over 12V. Its as if something is draining the batteries overnight?

I had another alternator so swapped it over. Again only a 13V charge.

Am I missing something obvious?

Cheers, Paul

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Eliminate the batteries as causing the problem. Possibly one is draining the other. Separate them electrically before leaving the car. Then check them before starting the engine (trying to start the engine).

It's toss a coin whether you leave each battery connected to its' respective load after you separate them.

If you separate AND remove the loads, if one battery goes flat, the fault is obvious. If neither battery goes flat the fault is in one of the loads, but you don't know which one.

If you separate but DON'T remove the loads, and one battery goes flat, you don't know if it's the battery or a load fault (something draining the battery).

Good Luck

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Thanks for all the ideas.

The book says that the alternator output should be a minimum of 13.4V at 3000 revs, but I'm not getting higher than 13.1V with nearer 5000 revs. If one or both batteries were at fault surely that wouldn't make any difference to the alternator output?

I have been swapping the battery with easiest access with a new fully charged battery. If it is a battery at fault then it will be the other as the new battery is being discharged too. I also noticed on the unchanged battery a black oily film around the screw threads to the cells, which I have never seen before

I will separate the batteries as you suggest David and see if that makes a difference.

Nothing is left on at night and ignition keys are removed.

I have noticed that dash lights are working intermittently, so maybe a short somewhere or just a bad connection.

Cheers, Paul

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With the batteries charged, the belt tight and the engine running at 1500 revs or so, you should get 13.8v up to about 14.5v max when measured at the battery. Any less and you have a problem. Without looking I would be inclined to point the finger at the alternator but get the batteries checked first - what is Romanian for 'Drop test'? :) Any local garage will be able to check them for you but will need to charge them overnight.

Keeping batteries connected together is known to be bad for them, a split charge system should be used.

Chris

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With the batteries charged, the belt tight and the engine running at 1500 revs or so, you should get 13.8v up to about 14.5v max when measured at the battery. Any less and you have a problem. Without looking I would be inclined to point the finger at the alternator but get the batteries checked first - what is Romanian for 'Drop test'? :) Any local garage will be able to check them for you but will need to charge them overnight.

Keeping batteries connected together is known to be bad for them, a split charge system should be used.

Chris

Thanks Chris, but I changed the alternator this morning for a different one and the output was just as low?

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I have x2 batteries under the seat. They are not split charged but connected together. One mainly for the starter, the other for nearly everything else.

If they're connected together, with no split charge, split diodes etc, they both run everything, all the time.

Have you put an ammeter in either the negative or positive wires to the battery to see what current draw you have when the ignition is off?

(don't try measuring cranking current, most multimeters are only rated to 10A)

It does sound like you have at least one dead battery, which may well have taken the other down with it.

You need to charge, and test, each battery in isolation in order to determine their condition.

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If you are charging flat batteries, the alternator output will appear low due to the large current drain.

Check electrolyte levels, check for funny smells (smells like rotten eggs when one battery is cooked), and separate them - chances are only one has a problem and that is killing the second.

I had a boat this summer with a mysterious battery flattening problem - cured just by topping up the levels. Discovered this after swapping alternators, checking cut-off switches, and loads of time wasted.

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If you are charging flat batteries, the alternator output will appear low due to the large current drain.

Check electrolyte levels, check for funny smells (smells like rotten eggs when one battery is cooked), and separate them - chances are only one has a problem and that is killing the second.

I had a boat this summer with a mysterious battery flattening problem - cured just by topping up the levels. Discovered this after swapping alternators, checking cut-off switches, and loads of time wasted.

Yes, I have checked the electrolyte levels. One of the batteries needed topping up and has been charged up. No smells though.

I have a cut off switch for the winch attached to the front of the battery box. Why would you check that?

Thanks Paul

LandyManLuke - Have you put an ammeter in either the negative or positive wires to the battery to see what current draw you have when the ignition is off?

No I haven't. I am not too clever with the multimeter, so which setting should I put it on for this test, and what level of draw am i looking for?

Both batteries are disconnected for the night. It is cold outside with plenty of snow, so I'm looking forward to seeing what the readings are in the morning.

Thanks, Paul

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Your multimeter should have connections for the probes to measure current, start off using the 10A connections and set the dial to the 10A range too. Disconnect the ground/supply (which ever is easiest - ground if you have lots of +ve wires going all over) and put the meter in series with the battery and the removed lead.

With the ignition off, you should expect to see a few hundred milliamps, which will be the draw from things like the clock, stereo, alarm. Remember to turn the interior light off if the door is open!

Don't try and turn the key to pre-heat or start, as you'll pop the fuse in the meter.

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You should also check the voltage between alternator casing and battery negative post (the lead bit, not clamp) when engine running, and some load (eg headlights) and same for alternator positive to battery positive.

Doesn't matter which way you connect the leads (ie red to batt etc). Meter should be set to measure volts, with leads plugged in correct holes - check them! - if you've just been measuring amps, your meter won't last long!

Post up the readings on here. This will tell you if there are any poor connections along the way.

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I have a cut off switch for the winch attached to the front of the battery box. Why would you check that?

My discharge problem was on a boat - the cut off switches isolate engine and domestic batteries from each other and various electrical systems.

Your cut off switch won't have any bearing on batteries going flat. (Unless you have some strange drain in the winch...)

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Thanks for all the suggestions. I'm just downing a couple of coffees before I get started on the tests mentioned. It was well below zero last night and snow everywhere. Picture enclosed of the wood store to give you some idea of the cold!

DSC08837600x450.jpg

I disconnected the batteries last night and left them in the LR. The V readings were 12.24V and 12.52V disconnected. This morning they were 11.97V and 12.37V disconnected. When I connected them, I had a combined reading of 12.13V. When I started the engine I had a reading of 13.5V on idle.

I spoke to a local mechanic friend that has been helping me and mentioned the various tests discussed on the forum. He said he did one of them in a crude way to test for load draw when the ignition is off. Both negs connected then with internal light off touched pos leads to pos batteries posts to see if there was any spark. There was nothing which he said indicates no draw?

Cheers,

Paul

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Sounds like the one that dropped to 11.97v is knackered.

Connecting them the way you are doing isn't good for this reason. Now that one is lower, the other one has to charge it. They then balance out. But then the one that is knackered losses more charge and the other one has to charge it, so in turn it loses charge.

I was once told to only connect 2 batteries together as you are doing if they are identical, and even then they need to stay identical (ie if one starts to die they are not identical) You would be much better installing a split charge system.

Your other option would be to manually control it with a cut off switch, still not as good as the split charge. You would need a switch to separate the batteries. When you switch off seperate the batteries for the night, then start up and run for the first twenty mins or so on just the primary battery. Then introduce the secondary battery afterwards for extra capacity and to charge it. Not sure on the merits of this or if there would be any disadvantages but from a quick think it would be better than what you have got currently

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Well not the most successful morning of testing. The main problem being the leads on my multimeter being too short to do much in the engine bay and under the front passenger seat at the same time! I did manage to get the lead from the alternator body and then to the cable on the earth. With engine running and lights on it read -0.01V.

Not sure if I was doing something wrong with the amp test. I had it set on 10A, then both +ve leads connected with both -ve leads disconnected. Multimeter to +ve and disconnected -ve gave no reading. However, neither was the light on with the door open?

The 11.97 battery I changed for a spare fully charged battery. However, the resulting multimeter reading with engine running was still only 13.2V?

Cheers, Paul

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Not sure if I was doing something wrong with the amp test. I had it set on 10A, then both +ve leads connected with both -ve leads disconnected. Multimeter to +ve and disconnected -ve gave no reading. However, neither was the light on with the door open?

Apologies, i'm at work, so no pretty diagram, but you want something like this;

btw, sorry the compression is a mess. :(

post-84-1228831556_thumb.jpg

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Apologies, i'm at work, so no pretty diagram, but you want something like this;

btw, sorry the compression is a mess. :(

Thanks Luke, got that. I take it with 2 batteries, I would have to test one battery at a time, with other battery terminals removed?

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The main problem being the leads on my multimeter being too short to do much in the engine bay and under the front passenger seat at the same time!

I did manage to get the lead from the alternator body and then to the cable on the earth. With engine running and lights on it read -0.01V.

Ok, that seems good enough.

Now you need to test the volt drop on the positive lead (you have just tested the volt drop on the negative or earth path).

Take a red jump lead. Clamp one end onto a piece of 2" x 1" wood, or plastic water pipe, or anything that doesn't conduct electricity. Put this end on the ground, near the front wheel that is closest to the alternator. make absolutely certain that, whatever you do, this clamp NEVER touches the car or engine metalwork.

Clamp the other end of the cable onto the Positive terminal of the engine start battery. Wiggle it around to get the best possible connection. The clamp on the wood now becomes, for test purposes, the battery positive terminal. We have to make allowances for a possible iffy connection, but this is a start.

Put your meter to measure DC Volts, and connect it between the large positive (+ve) terminal on the alternator and the clamp-on-the-floor. It isn't critical which way round you connect the meter (for this test) but the alternator terminal should be more positive than the clamp, so put the positive meter lead to the alternator.

Engine running, lights on, as before, you are looking for a similar 0.01volt reading.

If it's significantly higher, wiggle the clamp on the battery terminal, to improve the connection, then test again.

If the reading stays high, then we have to test at intermediate points along the positive feed to see where the significant volt drop is occuring.

The 11.97 battery I changed for a spare fully charged battery. However, the resulting multimeter reading with engine running was still only 13.2V?

This is why we are checking the voltage drops.

As a matter of interest, I assume all these voltage readings you have taken while the engine is running have been at the battery. Yes?

Under the same conditions (engine running, lights on) check the voltage reading between the alternator case and the alternator positive terminal.

If the reading across the battery pos & neg is 13.2, and the reading across the alternator is 13.3, then there is nothing wrong with the wiring between the battery and the alternator.

Possibilities is that the battery is not fully charged, and pulling the alternator down, or the alternator is struggling for some other reason. I appreciate you have just changed it, I'm merely pointing out possibilities.

Good Luck.

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Thanks Luke, got that. I take it with 2 batteries, I would have to test one battery at a time, with other battery terminals removed?

Just in case Luke is in transit, and not available to answer ....

Yes, test one battery at a time.

As your batteries are connected in parallel, with no splitting, then Yes, disconnect one or both leads from the other battery.

In theory, as both batteries feed the same loads, you only need to test from one battery.

But, you are chasing a fault, so for the little time and effort it takes, you may as well repeat the test on the second battery, leaving the first disconnected. I'd expect the results to be identical, but we are here because of the unexpected !!

You are looking for 'something' that is drawing current all the time. Obviously switch off any interior lights that are normally on when you open the door(s), but also recall that clocks and radios-with-memory also take power all the time, so if you have those fitted, expect to see some current flowing.

Cheers.

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Hi, I did the tests yesterday and these are the results. I had to modify the 2nd test as I couldn't find jump lead. My local mechanic friend thinks that the original battery that I replaced was the main culprit and that my 2nd battery is only slightly better with the newest battery keeping things ticking over. He thinks the first alternator was damaged by the current from the 18 wheeler that jump started me in Hungary. Do you agree?

Alternator +ve to –ve was 14.2V

Then both +ve leads disconnected from batteries with engine running. Multimeter from +ve disconnected batteries to connected –ve leads read 14.2V

As soon as the +ve leads were replaced with engine running the combined V dropped to 13.3V. Battery readings separately were 13.7V for the new battery and 13.1V for the existing battery.

Cheers,

Paul

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Hi, I did the tests yesterday and this is what. I had to modify the 2nd test as I couldn't find jump lead. My local mechanic friend thinks that the original battery that I replaced was the main culprit and that my 2nd battery is only slightly better with the newest battery keeping things ticking over.
Quite possible. While you are testing the complete system, it seems to me that having two batteries is a distraction. As you don't have a split charge arrangement you can feed everything off one battery (until you get the system proved OK, or fixed). I said use a jump lead because I didn't envisage you being without one. I thought they would be a standard part of the vehicles inventory. For the tests I described, the lead isn't taking any current, so a bit of house flex would have done the job, just make sure the connection to the battery is good and tight, and at the other end of the flex make sure the test meter clip also has a good clean connection.
He thinks the first alternator was damaged by the current from the 18 wheeler that jump started me in Hungary. Do you agree?
Unlikely that there was excessive current draw EXCEPT that I'd expect an 18 wheeler to have a 24volt system. Did you get a boost from the full 24 volts, or did the driver pick a mid point connection on his battery pack, and only give you 12 volts? If you got the full 24volts I suspect there are two options; either you get away with it, OR the alternator dies completely. As yours is still working, to some extent at least, I'd say the jump start didn't alter the state of affairs.
Alternator +ve to –ve was 14.2V
In light of your later comment, was either of the batteries fully connected at this point?
Then both +ve leads disconnected from batteries with engine running. Multimeter from +ve disconnected batteries to connected –ve leads read 14.2V
This was risky, and in one way, a surprising result. You aren't supposed to run an alternator with the battery disconnected, as the alternator voltage 'normally' climbs too high, with damage to the regulator, and any load items (bulbs or ECUs) that happen to be switched on at the time. However, it's possible that modern alternators have an improved design to protect against this form of self destruction.
As soon as the +ve leads were replaced with engine running the combined V dropped to 13.3V. Battery readings separately were 13.7V for the new battery and 13.1V for the existing battery.
These voltages are lower than I would like to see, for fully charged batteries. When connected in this state, what was the reading across the alternator? 13.7, 14.2, or something else?

Cheers,

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Thanks David,

Yes, the alternator was running at 14.2V and combined batteries connected and running simultaneously at 13.3V. Interestingly when my foot goes on the accelerator the V drops to a combined 13.1V?

Jump leads are standard to my LR itinerary, but I now think they became part of the 18 wheelers! I had very little sleep that night and was convinced I had packed them back in my trunk. It is very hard to find good ones over here. Most have thick looking cables but are mainly insulation with a tiny core. I will have a look around for some cable to complete your suggested tests.

I did have a split charge system, but when my cousin tidied up the wiring found that it wasn't working so simply connected the batteries until I bought another one. As everything was working smoothly for several months I never got round to replacing it. I will try and look for one here or change to a single battery as you suggest until I get over to the UK next in March.

Would a reading from a single good battery of 13.7V be acceptable when the alternator reads 14.2V. When we tried this the V still dropped at the battery when the revs were increased?.

Cheers, Paul

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Jump leads ..... It is very hard to find good ones over here. Most have thick looking cables but are mainly insulation with a tiny core.
Time to try Britpart?
Would a reading from a single good battery of 13.7V be acceptable when the alternator reads 14.2V. When we tried this the V still dropped at the battery when the revs were increased?.
No. This is why we need to find where the voltage is being dropped. At 13.7 the battery is never getting a full charge. In your current weather conditions (your previous photo) I suggest putting the battery on charge every night (assuming you are using the vehicle during the day). Charge at a low current (if you have a choice) and make sure the battery is kept topped up with distilled water. Do this over several days (nights).

Voltage dropping as the revs increase is not something I recall coming across before. See if one of the others has anything to add.

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