Trickle Charger Problem? Help Please

eadmr04

eadmr04

Member
I went to use the P6 last week after it had been standing for a while but have always had it on charging with a trickle charger. When I tried it the battery was very very flat and it wouldn't turnover. I removed the battery and the levels where a bit low so I topped them up and charged it on a low charge for about 36 hours. Re-fitted the battery and all ok. I then left it in the garage for 3 days with trickle charger connected, went to use it this morning and dead again. Put it on a quick charge for 30 mins and it fired up (was on the way to a classic show). It started ok for the rest of the day but I'm wondering if my battery may now be past it or could it be the trickle charger may not be working properly. A green light comes on the charger when I connect it to the car connections. I have a test meter so is there any way I can check if I'm getting the correct sort of charge out of the charger and if so, how do I go about testing it and what readings should I be looking for? :D
 
If the battery has been left for a while, maybe the internal plates have started to 'go' (lead sulphate hardening on the plates, I think)

To test the battery, the best way is to ask someone with a high-discharge tester to put a heavy load on the battery and note the voltage (which should not dip below 9.5 - 10V, but that depends much on the tester itself (some are heavier loads than others for use with larger batteries)) and notice if any of the cells are rapidly bubbling up (which means dead cells!) This test is best if the battery gets an 80% charge

The other way I have seen to test the battery is to disconnect the coil wire (preferably the wire on the -ve (assuming -ve earth!)/CB side of the coil going to the dizzy (I think it's white with a black tracer, and possibly has a male spade on the wire (our series 2 2000Auto did))

Put a voltmeter across the battery, then have an assistant crank the engine over for about 10 seconds. The voltage during cranking should not dip below 9.5V (ideally not under 10V, but batteries that are 'nearing the end but are still serviceable for the time being' seem to go dip below 10V slightly.) It's likely any dead cells will rapidly bubble up, but is not always the case when using this 'voltage under cranking' test.

To test the charger:-

This is not a robust test as it only really picks up if the charger is pumping out a voltage, and is not really recommended:

You could put a voltmeter on the terminals while it is not connected to a battery (be careful the crocodile clips do not touch each other, of course!), but this does not always work as some chargers 'sniff' there is no current flow and so cut off the supply to the battery leads. (Quite sophisticated transistor switching!)

If you do go down that path, and there is a voltage on the clips when not under load (i.e. when not connected to a battery), the voltage should be in the region of 13.6-14.5 V (for a trickle charger), higher (15-15.5V) for a 'quick' charger. Different chargers have different off-load voltages, and are not easy to spot.

The better method would be:-

Take a voltage reading of the battery (which should not be less than about 12.0V). Record/remember that voltage. Put the battery charger clips on, but do not switch on the charger yet!. The voltage should be the almost the same as before. If it's significantly (> 0.5V) lower, it suggests the charger diodes are blown and are 'leaking'.

Now, turn on the charger, and notice the voltage reading. If the voltage reading is the same as the reading when the battery was not connected to the charger, it suggests that the charger is not pumping out any juice. If the reading shoots up to 13.6V - 14.5 V, the battery is not accepting any charge. For a trickle charger the reading I would think should be in the region of 12.3 - 13.0V for a flat (0%) - 25% charged battery, 13.0 - 14.0V for a 25 - 75%, 14.0 - 14.5V for a 75+%

It's no way an absolutely accurate guide, I hasten to add. Very many factors influence these tests!

[A general rule of thumb: Battery offline voltage = 12 + (0.6 x amount of charge)

Battery 25% charged, offline voltage = 12 + (0.6 x 0.25) = 12 + 0.15 = 12.15V

Battery 50% charged, offline voltage = 12 + (0.6 x 0.5) = 12 + 0.30 = 12.3V

Battery 75% charged, offline voltage = 12 + (0.6 x 0.75) = 12 + 0.45 = 12.45V

Battery 100% charged, offline voltage = 12 + (0.6 x 1.00) = 12 + 0.60 = 12.6V

Again, this is not totally accurate, merely a guide, I hasten to add!]
 
One of the symtoms of an aged and less effective battery is the level of current that the battery accepts at 13.8 Volts, a new battery when fully charged should consume no more than 100mA (milli amps) with a charger supplying 13.8 Volts, as the battery ages this level will increase to say 300 to 400 plus mA.
When the battery gets to this age/state your trickle charger may not have the capacity to keep your battery charged and all you are doing with it is slowing down its self discharge rate.
The soution I use in this circumstance is to use a standard "old school" high current 5 Amp Plus battery charger and put a voltage regulator on its output set at a minimum of 13.8 Volts but no more than 14.4 Volts. Whilst the battery may be getting old you can still get a few more years out of it.

Graeme
 
The only way to keep a battery in good condition is to use it regularely in the manner intended - ie drive the car. All other solutions have varying drawbacks which will write your battery off faster than if you had been regularely using the car. So put out of your mind now any thoughts along the lines of "but it's only 3 years old"!

That said a continuous trickle charge is a particularely bad solution to preserving your battery. As you've noted this will cause the battery liquid to bubble away until the plates are exposed and then damage starts to occour. If you stick with the trickle charge idea then perhaps do a 24 hr trickle once per week and check the levels after the charge.

The intended operating mode of the battery is to suffer a very heavy discharge at starting, followed by a very rapid recharge, followed by floating at approx 12V. Any attempt to preserve the battery should attempt to replicate this sequence. The heavy discharge has the effect of cleaning up the plates and preventing them "furring" up. The heavy charge ensures all areas of the plates get an equal pounding in the charge - trickle charging can tend to use some parts of the plates preferentially.

Every body has their own favourite solution from this point on. My own is a pulse charger, where the charger is quiescent until voltage drops by a set amount, then the charger delivers a high charge thump until the voltage recovers. Drawback is that the cleaning heavy discharge is absent.

If you are prepared to manually intervene then you can get quite close to normal duty. Eg you could give the car a start once per week, followed by 3 hrs or so of high charge.

I stand back and prepare to be abused on this one!

Chris
 
A trickle charger running at 13.8 Volts should consume the least water and preserve the battery charge, however batteries with a level of sulfation still can run into problems. One charging solution is to spike or pulse the charge current the sudden shock is said to reduce the effects of sulfation.

I would not recommend charging the battery once a week as this induces micro cycling which will reduce the battery life quite quickly. to put it simply you only get so many charge to discharge cycles out of a modern car start battery, by not charging it the battery is self discharging. This means that after a week of sitting idle the battery (say 6 days) if the battery was new it will be self discharging at a rate of 100mA this will equate to 14.4 amp hours of it total capacity and if the battery was a 50 Amp hour battery this would mean you had discharged it aprox 29% of its capacity (28.8%) then on the 7th day you recharged it, this is a large and significant battery cycle and will very quickly rob your new battery of its nameplate capacity. Lead acid battery do not like to cycle but if they must they must be shallow cycles, indeed do a deep cycle on a start battery and you will be lucky to see it last more than 5 or 6 cycles. Its a sliding scale the deeper the cycle the less life it will have.

Note 1: With the increase in mans technology you would expect the car battery to be better now than in any time in it's past and you would be dead wrong. The only winner is the battery manufacturer who has improved the tech so much that he can now make a battery that will last 25 months then fail one month outside of it's warrenty period thus ensuring you the consumer will buy another, gosh it a smart business to be in (sarcasm intended)

Note 2: cranking your car engine takes bugger all out of your batteries Amp hour rating less than 1% in many cases, and with newer geared starter motors even less, lower current draws and less depth of discharge cycle put a smile on your battery :)

Graeme
 
Thanks for all the excellent advice :D . Some of it's a bit over my head but I think after all, the battery has just about had it. Has anyone bought one recently that they can recommend for a 1968 P6b so it fits nicely with the correct configuration, if so where did you get it from?
 
A Chris says, the best way to keep the battery going is to use it as intended i.e. to start the car and then charge it (via the alternator)

Graeme is right overall for geared starters.. but I assume that the P6 in question has a 'normal' direct-drive (i.e. not geared) starter. I suggested 'ideally no less than 10V' for the cranking test, as this slightly higher than the 9.5+V 'pass mark' of a heavy-discharge test.

However, some geared motors have permanent magnets, these are lighter but tend to use MORE current! :-S

Of course, there is no real right answer, it's really a matter of judgement and 'feel' which experence teaches. The chemistry and processes in batteries are very non-linear!

[As an aside, I have seen a car (a Peugeot 305. [Sadly not a P6! :(] ) with a battery that dipped below 9.5V under the heavy-discharge test (no cells bubbling vigorously, though), yet started the car with just a barely perceptible 'strain' in the coldest of weather for approx 2.5 years. That car was used on long high-speed runs every day, though. Maybe that 'extended' the battery's life]
 
I picked up a Clarke booster/ charger on Ebay - Claimed 160 amp starting current
When on miminum charge setting it's putting out less than 12 volt , on max charge 16 or so volts
I'm a bit concerned how it can charge a battery at less than 12 volts - any thoughts ?

I normally use a Halfords charger I found in the eaves of my garage when I moved in 17 years ago. Looks about 1960's vintage but works a treat
 
Dont know the particular charger in question how ever many/most older traditional battery chargers just rectify the AC Voltage which gives you a lumpy output waveform which does not respond well to measuring with a digital voltmeter as it has a large componant of AC Voltage in the DC output, the upshot is that your DC digital voltmeter will read an average value rather than the correct value and it will always be a low reading aprox 11.5 to 12 volts would normally represent a value around 15 Volts :)

Graeme
 
eadmr04 said:
Has anyone bought one recently that they can recommend for a 1968 P6b so it fits nicely with the correct configuration, if so where did you get it from?
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I've bought batteries for our 110 & the Bruiser quite recently, both from our local factor. Not sure what make they are. I considered a Halfords item briefly as I read a couple of good things about them but on further reading found just as many bad things written of them too including more than one instant failure within warranty. The biggest downside though is the just shy of £200 purchase price for which you get a 4 year warranty. Our batteries have a 3 year warranty for a sub £60 price tag so even if they fail just after warranty expires the fact that we can buy 3 of the things for the price of one of the big name brands seems to spell out the value for money advantages quite well. They both start the Rovers fine.
 
I've got an optima redtop battery on my P6, seems to do the job ok, and fits into the battery box, I had it on my Mitsi diesel pickup truck. The beauty of these is that they don't get knackered by sulphating of the plates if not used for a while, and are gel filled, and can be used any way up. I got mine from These guys. It wasn't cheap, but this was the cheapest place I could find these. They deliver for free too. It certainly whips the old lump over quickly enough.. (815amps cold cranking current). I've also got a CTEK battery charger/conditioner. They're quite expensive, but can be left connected for months at a time, and are "intelligent", and only charge the battery when it drops by a certain amount, and will do "pulsing" too to help reduce sulphating. This is the one I've got, but I got mine for about £35 on Ebay. It also comes with a connector to go across your battery when fitted to the car, so you can quickly plug/unplug it
 
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