P38A Alternator upgrade 4.6 Gems

Datatek · Jul 11, 2022

P38 Monkey said:
I don't have a Diesel engine. I don't have EAS. I have a Marty RF Filter.
So my BeCM slumbers gently.
My battery fits neatly and my alternator is not stressed.
If I don't use my P38, I top the battery up using a Ctek smart charger plugged into a permanent connector once a week.
Landyzone info is key to my setup and I am as ever eternally grateful for the detail I have received, not least (in fact, most) from your good self..!!!
Horses for courses. I'll get my coat.

You still have the 30/35ma drain from the BECM and a lead calcium battery that is not kept fully charged will suffer premature failure. With the correct charging voltage which does not stress the alternator, even with your smaller battery for the petrol engine it should go 3 weeks without use and still start the car OK.

P38 Monkey · Jul 11, 2022

Datatek said:
You still have the 30/35ma drain from the BECM and a lead calcium battery that is not kept fully charged will suffer premature failure. With the correct charging voltage which does not stress the alternator, even with your smaller battery for the petrol engine it should go 3 weeks without use and still start the car OK.

Sure. My chums at Tayna Batteries say I have a lead-calcium battery and that my Ctek smart charger is set correctly for it.
Apparently, alternator output voltage should be 13.8 to 14.2 volts, and in fact my "13.8" MM alternator actually goes up to 14.1 volts in normal use. They say that anything much over 14.2 volts risks internal gassing on a long run with low electrical load.
My battery should be able to output 30 mA for around 3 months before being flat, so BeCM stand-by power usage is not an issue.
I keep my P38 garaged so do not need the rear window de-mister, which is just as well, given that it was supplied by Specialist Cars of York, and a largely defunct rear de-mister was one of the 72 (that's not a typo) faults with which it was delivered.
As ever, continuous care is the watchword for a 25-year-old Range Rover, and regular top-up charging is a simple and effective way of keeping the battery above 80% capacity.

kermit_rr · Jul 11, 2022

P38 Monkey said:
Sure. My chums at Tayna Batteries say I have a lead-calcium battery and that my Ctek smart charger is set correctly for it.
Apparently, alternator output voltage should be 13.8 to 14.2 volts, and in fact my "13.8" MM alternator actually goes up to 14.1 volts in normal use. They say that anything much over 14.2 volts risks internal gassing on a long run with low electrical load.
My battery should be able to output 30 mA for around 3 months before being flat, so BeCM stand-by power usage is not an issue.
I keep my P38 garaged so do not need the rear window de-mister, which is just as well, given that it was supplied by Specialist Cars of York, and a largely defunct rear de-mister was one of the 72 (that's not a typo) faults with which it was delivered.
As ever, continuous care is the watchword for a 25-year-old Range Rover, and regular top-up charging is a simple and effective way of keeping the battery above 80% capacity.

I used to like tayna really good and helpful. Then something changed

I don't agree with what they've told you and there is plenty of evidence from battery manufacturers and other reasonable sources that speak to the contrary.
Lead acid batteries had the calcium added to help prevent gassing, but as a result need a higher voltage (14.7-14.8) for the chemical processes to complete and the battery to fully charge. It's not just about the state of charge, but the chemical 'recombination' process.
My 14.7 alternator reduces it's output as capacity is reached and I'll see ~13.5 on a steady run

Datatek · Jul 11, 2022

P38 Monkey said:
Sure. My chums at Tayna Batteries say I have a lead-calcium battery and that my Ctek smart charger is set correctly for it.
Apparently, alternator output voltage should be 13.8 to 14.2 volts, and in fact my "13.8" MM alternator actually goes up to 14.1 volts in normal use. They say that anything much over 14.2 volts risks internal gassing on a long run with low electrical load.
My battery should be able to output 30 mA for around 3 months before being flat, so BeCM stand-by power usage is not an issue.
I keep my P38 garaged so do not need the rear window de-mister, which is just as well, given that it was supplied by Specialist Cars of York, and a largely defunct rear de-mister was one of the 72 (that's not a typo) faults with which it was delivered.
As ever, continuous care is the watchword for a 25-year-old Range Rover, and regular top-up charging is a simple and effective way of keeping the battery above 80% capacity.

Funny that almost all cars since the nighties have come with alternator set points of 14.7 volts, even my 1986 Toyota MR2 charges at 14.7 volts. as required by the higher internal resistance of lead calcium batteries. The Mobiltron regulator recommended on LZ does indeed fold back from 14.8 to 13.8 volts or a little less when the battery reaches 100%
As well as the BECM 30ma drain, batteries self discharge so don't count on 3 months.

P38 Monkey · Jul 12, 2022

Datatek said:
Funny that almost all cars since the nighties have come with alternator set points of 14.7 volts, even my 1986 Toyota MR2 charges at 14.7 volts. as required by the higher internal resistance of lead calcium batteries. The Mobiltron regulator recommended on LZ does indeed fold back from 14.8 to 13.8 volts or a little less when the battery reaches 100%
As well as the BECM 30ma drain, batteries self discharge so don't count on 3 months.

The fact that our batteries have evolved since our cars were designed is interesting. Doping the lead electrodes with various substances presumably increased with the introduction of stop-start technology, and it was interesting to hear that a side effect of calcium doping is the need for a higher charging voltage. My Enduroline 072 battery has "Ca+" on the label, but I am not certain if that makes it a lead-calcium battery or not - you think it would be simple to check, but...come on Tayna, tell me the truth.

My Ctek charger on "normal" charges at a nominal 14.3 volts, which seems to be an old-school simple lead-acid level below the "gassing voltage" of 14.4 volts. After charging fully, the battery drops back to 12.73 volts overnight presumably indicating that it did indeed get fully charged at 14.3 volts. The green indicator is on too.
The Ctek charger has an AGM setting which charges at 14.6 volts and although my battery is not AGM technology presumably that would be an appropriate setting for it, given that it has calcium in the electrodes? I have asked Ctek and am awaiting an answer.

On the alternator side, I thought that my MM standard unit would run asymptotically to 13.8 volts, but maybe newer rectifier / regulators are smart enough to charge at 14.7 volts then back off, to 13.6 volts? That latter voltage is the level at which my Ctek charger runs when it has finished the charging cycle.

kermit_rr · Jul 12, 2022

my ctek charges to 14.4, or 14.7 on 'agm' setting and also has a recondition setting which charges to 15.8 on both
i notice the 'normal' car setting says use for wet batteries, ca/ca, MF, GEL and many AGM batteries, then goes on to say the AGM setting is for most AGM batteries.
i honestly think the tech is outdated. yes you can still buy batteries that need topping up, ie charge at 14.4, but you wont find one on a main stream modern car

Datatek · Jul 12, 2022

P38 Monkey said:
The fact that our batteries have evolved since our cars were designed is interesting. Doping the lead electrodes with various substances presumably increased with the introduction of stop-start technology, and it was interesting to hear that a side effect of calcium doping is the need for a higher charging voltage. My Enduroline 072 battery has "Ca+" on the label, but I am not certain if that makes it a lead-calcium battery or not - you think it would be simple to check, but...come on Tayna, tell me the truth.

My Ctek charger on "normal" charges at a nominal 14.3 volts, which seems to be an old-school simple lead-acid level below the "gassing voltage" of 14.4 volts. After charging fully, the battery drops back to 12.73 volts overnight presumably indicating that it did indeed get fully charged at 14.3 volts. The green indicator is on too.
The Ctek charger has an AGM setting which charges at 14.6 volts and although my battery is not AGM technology presumably that would be an appropriate setting for it, given that it has calcium in the electrodes? I have asked Ctek and am awaiting an answer.

On the alternator side, I thought that my MM standard unit would run asymptotically to 13.8 volts, but maybe newer rectifier / regulators are smart enough to charge at 14.7 volts then back off, to 13.6 volts? That latter voltage is the level at which my Ctek charger runs when it has finished the charging cycle.

The new regulators are, as I said, smart enough to drop back to 13.5/13.8 when the battery is fully charged.
At 14.3 volts a lead calcium battery will charge, it just takes longer.
Many new cars start charging at 18 volts to cater for the school run.
Really old school batteries used to charge at 2.2 volts per cell.
I would guess that the Ca+ indicates a lead calcium battery of the latest generation with a high calcium content.
AGM batteries are not suitable for old cars without smart charging any more than GEL batteries are.

P38 Monkey · Jul 12, 2022

As always, am learning a huge amount from you guys - thanks. I’ll monitor this thread to see how Awkward Bob gets on with the upgrade…. Cheers everyone..

Grrrrrr · Jul 12, 2022

I think my replacement set point was either 14.3 or 14.5V. My alternator has the same number of coils though so no more power can be wring out of it and therefore I doubt gassing is a real risk. There are only so many electrons you can wring out of it!

P38 Monkey · Jul 12, 2022

I am getting a couple of different messages on lead-calcium: in summary it reduces gassing at higher voltages - a bit like Rennies for batteries (or Gaviscon for our Continental chums). It was discovered in the 1930s but only really introduced into standard car batteries when stop-start cars with high output alternators came in, enabling rapid re-charging of the battery. Never mind blasting along muddy tracks and fording mighty rivers - it's that challenging school-run scenario again.

The two contrasting messages I see are:
1) A lower charge voltage (13.8 - 14.2) will still fully-charge a lead-calcium battery, but naturally it takes longer.
OR
2) A lower charge voltage will never fully charge the lead-calcium battery as it needs a higher voltage (14.6 - 14.8) "to fully implement the recombination process".

My own observation is that a lower charging voltage (14.3 volts) still charges my lead-calcium battery to a resting >12.7 volts, with the little green charge-level indicator on.

Of course the answer is to have the alternator outputting 14.7 volts... the lead-calcium battery will get charged quickly and won't suffer any over-charging damage.

Datatek · Jul 12, 2022

Grrrrrr said:
I think my replacement set point was either 14.3 or 14.5V. My alternator has the same number of coils though so no more power can be wring out of it and therefore I doubt gassing is a real risk. There are only so many electrons you can wring out of it!

The amount of power coming out of the alternator is not the issue, it's the potential difference between the output voltage of the alternator and the voltage to which the battery can rise, no PD and there will be no current flow and therefore no charging. It's a bit more complicated than that and involves the internal resistance of the battery but that gives you a clue.
Car alternators rarely get close to full output as a result of the battery demands and then only immediately after cranking for a few seconds.

Datatek · Jul 12, 2022

P38 Monkey said:
I am getting a couple of different messages on lead-calcium: in summary it reduces gassing at higher voltages - a bit like Rennies for batteries (or Gaviscon for our Continental chums). It was discovered in the 1930s but only really introduced into standard car batteries when stop-start cars with high output alternators came in, enabling rapid re-charging of the battery. Never mind blasting along muddy tracks and fording mighty rivers - it's that challenging school-run scenario again.

The two contrasting messages I see are:
1) A lower charge voltage (13.8 - 14.2) will still fully-charge a lead-calcium battery, but naturally it takes longer.
OR
2) A lower charge voltage will never fully charge the lead-calcium battery as it needs a higher voltage (14.6 - 14.8) "to fully implement the recombination process".

My own observation is that a lower charging voltage (14.3 volts) still charges my lead-calcium battery to a resting >12.7 volts, with the little green charge-level indicator on.

Of course the answer is to have the alternator outputting 14.7 volts... the lead-calcium battery will get charged quickly and won't suffer any over-charging damage.

14.3volts will eventually, 13.8 volts or less will not in your lifetime but maybe in the afterlife

P38 Monkey · Jul 12, 2022

Datatek said:
14.3volts will eventually, 13.8 volts or less will not in your lifetime but maybe in the afterlife

Succint as ever ...! Point taken.

P38A Alternator upgrade 4.6 Gems

Datatek

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P38 Monkey

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kermit_rr

Very

Datatek

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P38 Monkey

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kermit_rr

Very

Datatek

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P38 Monkey

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Grrrrrr

Technician, Bodgit & Scarper Ltd

P38 Monkey

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Datatek

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Datatek

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P38 Monkey

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