geoff edwards · Jan 2, 2021

Hi I bought a new battery last year 2020. I do not use the car much and particularly with Covid-19 regulations. The car has been used about once a fortnight. I disconnect the battery, so I expect that it will hardly need charging. However today I was unable to get the car started.The car was almost unable to crank. Voltage was 12.39v. I have a Bergan battery checker and found that the battery underload was poor. I was quite surprised as I would have thought that the battery would hold a charge longer. I am hoping that the car will start when the battery is fully charged. There is a slight complication in that I had disconnected the ECU as it was getting oiled up. In doing so the body of the ECU touched the negative pole of the battery.

discool · Jan 3, 2021

Ok, your battery holding 12.39 should crank your engine with ease, a battery with 12.4v is 75% charged.
I you haven't already, put battery on charge overnight, or until it reads 12.60v that voltage will indicate the battery is fully charged, thats the voltage with the charger removed or of course take it for a 30 mile drive.

Im not familiar with your battery tester so i’ll assume that under load means ‘cranking voltage test’ therefore if the voltage is higher than 9.60v, the battery is in a good condition, if below 9.60v, then that isn’t good and the battery should be checked out - replaced.

I know my D1s battery can just turn over and and start with a ‘cranking voltage’ of 9.10v thats from a fully charged 3-1/2 year old battery after 3 weeks of standing still, not an issue I just recharge the battery one way or another, been that way for the last 23 years and the three previous batteries its had ... thats old school for you.

As far as the ECU touching the negative poll the case won’t/shouldn’t be conducted positive voltage, and if any thing the case could be grounded, to reduce any interference.

sierrafery · Jan 3, 2021

On a D2 if the voltage drops below 10V while cranking it will not start even if it's happily spinning so the voltage is relevant only then.

geoff edwards · Jan 4, 2021

discool said:
Ok, your battery holding 12.39 should crank your engine with ease, a battery with 12.4v is 75% charged.
I you haven't already, put battery on charge overnight, or until it reads 12.60v that voltage will indicate the battery is fully charged, thats the voltage with the charger removed or of course take it for a 30 mile drive.

Im not familiar with your battery tester so i’ll assume that under load means ‘cranking voltage test’ therefore if the voltage is higher than 9.60v, the battery is in a good condition, if below 9.60v, then that isn’t good and the battery should be checked out - replaced.

I know my D1s battery can just turn over and and start with a ‘cranking voltage’ of 9.10v thats from a fully charged 3-1/2 year old battery after 3 weeks of standing still, not an issue I just recharge the battery one way or another, been that way for the last 23 years and the three previous batteries its had ... thats old school for you.

As far as the ECU touching the negative poll the case won’t/shouldn’t be conducted positive voltage, and if any thing the case could be grounded, to reduce any interference.

Thanks discool. I have charged the battery overnight and using the tester it is good. The tester has a switch to apply a starting load. It is held for 10 seconds and the measure checked. I am relieved to read that the accidental touching of the negative battery terminal would not have damaged the ECU. On the first attempt the car didn't start with the charged battery. On the next attept it started straight away. I did recheck the inertia switch though. Possibly the intertai switch is sticking. I'll buy one to rule it out. The injector loom needs replacing as oil is getting to the ECU. For the time being I intend to check the red plug for oil. I ma not sure how frequent I might need to check and clean the plug.

discool · Jan 4, 2021

sierrafery said:
On a D2 if the voltage drops below 10V while cranking it will not start even if it's happily spinning so the voltage is relevant only then.

Correct, My statement is irrelevant, it was based on my petrol engined D1 and its behaviour with a low cranking voltage, and although a 9.60v cranking voltage is a sign of a good battery, it was without any suggestion to a Discovery 2.
Message to my self “l must stay on topic”

discool · Jan 4, 2021

geoff edwards said:
Thanks discool. I have charged the battery overnight and using the tester it is good. The tester has a switch to apply a starting load. It is held for 10 seconds and the measure checked. I am relieved to read that the accidental touching of the negative battery terminal would not have damaged the ECU. On the first attempt the car didn't start with the charged battery. On the next attept it started straight away. I did recheck the inertia switch though. Possibly the intertai switch is sticking. I'll buy one to rule it out. The injector loom needs replacing as oil is getting to the ECU. For the time being I intend to check the red plug for oil. I ma not sure how frequent I might need to check and clean the plug.

Thanks for you thanks.

Glade to see u have the engine running. Possibly just iffy plug/socket connection at the inertia unit.
Its hard to comment on the frequency with checking the loom oil contamination issue, depends on how bad it is, so from every other day to every six months, how easy is it to check the plug?

sierrafery · Jan 4, 2021

discool said:
Correct, My statement is irrelevant, it was based on my petrol engined D1 and its behaviour with a low cranking voltage, and although a 9.60v cranking voltage is a sign of a good battery, it was without any suggestion to a Discovery 2.
Message to my self “l must stay on topic”

I can tell you that i've seen Td5 cranking as mad while the voltage on the battery then was down to 8V... at that voltage the ECM is ''dead'' for the injectors as it has an internal "inverter" which must deliver 85V sine wave for the injectors common PWM path, it's not stated anywhere but i made measurements with oscilloscope and below 10.5V feed the whole thing is mixed up and the injectors are staying closed

geoff edwards

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