Thread: Battery charge voltage info poll.

Originally Posted by p38arover

Jeez! I'm lucky to get two years out of a Delkor in the P38A! I think it's because the alternator doesn't charge at a high enough voltage for Lead Calcium batteries.

The trouble is that it's hard to buy a non-calcium battery.

I've had the car for just over 7 years and I'm on my 4th (or is it 5th?) battery (including one red-top Optima). Yes, the alternator has been changed (to another standard item). The one in the Disco only lasted 12 months and it was replaced under warranty.

Ron , I too got tired of buying new batteries , so I bought a battery charger with 12V rapid or Trickle charge function , so Now I regularly take both batteries out and charge them until they reached their FULL charge state , well that's according to the Battery charger anyway , hopefully this will prolong the life of my batteries

Answers in italics

1 ) What is the voltage at the cranking battery’s terminals. 12.63 (36 hrs after 100 Km run Temp 15 deg C after 8.7 deg overnight)

2 ) Type of vehicle. Defender TD5 reg Aug 2004

3 ) What make and type of battery ( a model number will do ) Supercharge MF31-931 5 years old! (no 2nd battery)

4 ) When was the last time the vehicle was driven. Saturday 19th

5 ) How long was the last drive 100 Km approx

6 ) Is this your day to day drive or a once a week vehicle Used every 2 to 3 days on average

7 ) Alternator size 120A

8 ) Is this your tow vehicle or other. No towing done recently

If you can, the following info would also be of interest.

9 ) What is the voltage at the cranking battery when you first start your vehicle ( cold start ) 12.63v after opening door, 14.55v after engine running

10 ) With the motor still running, what is the voltage at your cranking battery after a 30 minute drive. 14.32v

Cheers,

Lionel

Hi folks and thanks to all who replied.

I was trying to get 20 maybe 25 replies from all the forums I posted the poll on and as 15:00 this afternoon, I have 51 replies.

I’m now going to have to put a spreadsheet together to process all the info.

Once done, I’ll post up the results, but any one still wants to reply to the poll, I’m leaving it running.

Again thanks and BTW this site posted the most replies by a factor of 2:1 compered to the next largest site count.

Thanks to those who took part in the poll and I am not going to post up any opinions on the results, people can come to their own conclusions.

Anyway here is the initial results from 52 replies of the Cranking Battery Voltage reading are as follows :-

95% ( 12.6 ) or higher = 25

90% ( 12.5 ) or higher = 13

80% ( 12.42 ) or higher = 4

70% ( 12.32 ) or higher = 2

Lower than 70% ( 12.32 ) = 8

There is a lot more data to be sorted yet but this was the main aim of the poll.

The Highest reading was 12.95v and the lowest was 11.83v

A small number of the reading were taken less than 12 hours from the last time the motor was run so I will have to do some calibrating.

Again Thank you to all those who contributed.

So:
~ 48% of batteries charged to >95%
~ 73% of batteries charged to >90%

Sorry I haven't posted results yet.
So far I have:
12.73V after 6 hrs standing.
EXIDE N70EX in a IIA diesel with 40A Lucas Alt. (only battery)
Daily driver atm. No towing.
Will have more data from the IIA and the 110 after the weekend.

Thanks Ben and post up when your ready as I’m going to keep the poll running and just update it every so often.

Cheers

Here are my results with the auxiliary battery isolated. I will collect the data again on Friday with both batteries charging.

1 ) What is the voltage at the cranking battery’s terminals. 12.22V

2 ) Type of vehicle. 94 Disco Tdi

3 ) What make and type of battery ( a model number will do ) SuperCharge (?? Forgot to get the model number - will update)

4 ) When was the last time the vehicle was driven. 36hrs prior

5 ) How long was the last drive 25km

6 ) Is this your day to day drive or a once a week vehicle Daily driver

7 ) Alternator size 100A

8 ) Is this your tow vehicle or other. It's my tow vehicle, tractor, adventure bus and anything else you can think of.

9 ) What is the voltage at the cranking battery when you first start your vehicle ( cold start ) 13.7V

10 ) With the motor still running, what is the voltage at your cranking battery after a 30 minute drive. 14.15V (at idle)

Some more info from the poll, and there are still replies coming in.

Most but not all replies included the operating voltage, of the info supplied, only 6 had 14.5v or higher, nearly half the vehicles ( 23 ) were between 14 and 14.4v but more interestingly though, 21 were under 14v but most had a cranking battery SoC of higher than 90%.

Some additional info, and this was to be expected, 6 of the vehicles with cranking battery SoC of less than 80% were pre 2001, 2 were 2001 Jeeps and these also had operating voltages of just 13.9 Max, 1 vehicle was 2003 and the last was 2006.

Of the vehicle with 90% or better cranking battery SoC, 14 were 2002 or later, but 13 were pre 1999 and of these 4 were pre 1990.

This well and truly makes a mockery of the myth that you can’t charge a cranking battery over 70-75% SoC and it shows that the alleged problem probably never existed.

BTW, most of the vehicles with low cranking battery SoC were Landies