Other Battery Question

Intestinalworm · Jan 2, 2021

Underestimated batteries until fairly recently - last couple of years I have had a run of battery issues with different vehicles. Was worthwhile re-investing in a DMM!

Okay, put a new battery in the D2 Td5 just several weeks ago! Perfect starts and no issues. However, I checked (just out of interest) the voltage output with my DMM today:
12.3V static and 13.9V engine running
Static voltage appears low!?
Should I charge the battery?
Thing is, my battery charger is a hand-me-down and it is very basic, it's what I now understand to be a trickle-charge battery; I understand these are not suitable for charging "flat" batteries.
Any thoughts?

Bantam1 · Jan 2, 2021

14v when running is usually the norm, that's the charge voltage most see and indicates a good alternator.
Anything at or slightly above 12v when not running sounds perfect for a 12v battery.
I was always told the slower you charge a battery the better. Trickle charging therefore seems to fit the bill.

When was your DMM last calibrated? Check it against another then you know whether your readings are accurate or not.

discool · Jan 2, 2021

Car batteries provide 12.6V DC (direct current) through six cells, producing 2.1V each.
~12.6V: fully charged
~12.4V: 75% charge
~12.2V: 50%
~12V: 25%
11.9V and below: effectively zero charge.

Therefore go for a half hour drive if you want a fully charged battery,
My disco is only used once weekends twice a month just to keep it in running order, so the battery is below 12v sometimes, but the engine turns over 4 times and starts ok, on my return, my ‘certified’ multimeter shows the battery at 12.6v, alternator charging between 14.1 - 14.5v when under load, so no issues there either.

If you thinking of getting a maintenance charger the have a look at C-tek’s products, never had any issues with my 20 year old C-tek XMS3600 which is connected most of the year to my classic car, and for other cars then the future proof XMS 5.0 is used, which I understand will recondition a very dead battery.

lynall · Jan 2, 2021

You need to leave the car standing overnight, then check battery voltage without unlocking the car, ie dont wake it up.

discool · Jan 2, 2021

lynall said:
You need to leave the car standing overnight, then check battery voltage without unlocking the car, ie dont wake it up.

So thats leave the bonnet part open then.

neilly · Jan 2, 2021

discool said:
So thats leave the bonnet part open then.

Or check the voltage through a 12S tow socket, if you have one fitted.

Cheers

discool · Jan 2, 2021

neilly said:
Or check the voltage through a 12S tow socket, if you have one fitted.

Cheers

Thanks, but I will always check battery voltage at the battery battery.

lynall · Jan 2, 2021

discool said:
So thats leave the bonnet part open then.

Not hard for any budding diy mech to check with car locked up.

kermit_rr · Jan 2, 2021

lynall said:
Not hard for any budding diy mech to check with car locked up.

Ok I'll bite.
How can you check the battery out the car it's locked and the bonnet is closed? Leaving the bonnet on the first catch seems easiest

discool · Jan 2, 2021

kermit_rr said:
Ok I'll bite.
How can you check the battery out the car it's locked and the bonnet is closed? Leaving the bonnet on the first catch seems easiest

You cant. But with can after installing a wire from each battery terminal out of the engine bay to a external weather proof remote socket. So when u need to test the battery just remove the protective cover to expose the remote pos & neg terminals. Install a suitable socket and charge the battery as well if required.
Similar in principle to the neilly suggestion with the S trailer socket in post #6.

Or use a gizmo from eBay to check via Bluetooth on your mobile.

lynall · Jan 2, 2021

Two bits of thin wire so no tit can cause a fire, two low amp fuses at battery end of wires, wires out front/side of bonnet, job done.
Or even simpler tape bonnet switch down?
Probably others, but i have used the first one before.

I have since gone one step further and fitted an anderson plug, again with a fuse in case someone tries to get cute by shorting the terminals together.

steve2286w · Jan 2, 2021

+1 on the mxs5
https://www.ctek.com/uk/products/car/mxs-5-0-uk
I had a golf layed up for 15 month , in that time as voltage dropped about 4 times I started up and ran for 30 mins at high tickover , it wasn’t enough to get a full charge back
I eventually let it go too flat and thought new battery was required , start stop AGM batteries very exp
So bought the CTEK , it has recondition modes to desulphate the lead plates , car on road now and batt seems fine
12.3 is low so fully charge up and see if it holds charge as said above,

Stanleysteamer · Jan 2, 2021

discool said:
You cant. But with can after installing a wire from each battery terminal out of the engine bay to a external weather proof remote socket. So when u need to test the battery just remove the protective cover to expose the remote pos & neg terminals. Install a suitable socket and charge the battery as well if required.
Similar in principle to the neilly suggestion with the S trailer socket in post #6.

Or use a gizmo from eBay to check via Bluetooth on your mobile.

Yeah yeah, blah blah, "just fit this flipping gizmo".

Just leave the bonnet up with a weight holding the bonnet switch down.

Stanleysteamer · Jan 2, 2021

lynall said:
Or even simpler tape bonnet switch down?

ABSOLUTELY, why over complicate stuff. He wants to get his car going, not frig around with it while it still isn't going?
Or, guess what, take the batt, off the car, charge it than test it properly.
It ain't rocket science!!!

lynall · Jan 3, 2021

Stanleysteamer said:
ABSOLUTELY, why over complicate stuff. He wants to get his car going, not frig around with it while it still isn't going?
Or, guess what, take the batt, off the car, charge it than test it properly.
It ain't rocket science!!!

Could be an issues if car is left roadside, sadly not everyone has off road parking.

kermit_rr · Jan 3, 2021

You can still lock it with the key once the battery is off though

lynall · Jan 3, 2021

kermit_rr said:
You can still lock it with the key once the battery is off though

Yes but that means the thief will have to bring his own battery, against his human rights dont you know

sierrafery · Jan 3, 2021

kermit_rr said:
You can still lock it with the key once the battery is off though

that's valid for the driver's door only

kermit_rr · Jan 3, 2021

lynall said:
Yes but that means the thief will have to bring his own battery, against his human rights dont you know

Leave bump start instructions on the dash

steve2286w · Jan 3, 2021

there’s no criminals in Australia

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