Car radio looses memory while cranking

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mb82

223 posts

Master Geek

#258601 11-Oct-2019 22:50

The radio in my hiace annoyingly wipes the settings every time I turn it over. The memory/battery wires are around the right way, turning accessory on / off does not wipe the memory, only cranking does. Cranking voltage is about 8.5 volts which seems low but a brand new battery produces the same result, I did go for the lower CCA option when I got another battery (600cca vs 750) but it is still suitable for the vehicle, I am not convinced that is the issue. Maybe the radio which I pulled out of a newer toyota echo is not built for the same voltage drop the van produces?

Any ideas ?

K8Toledo

1014 posts

Uber Geek

#2335813 11-Oct-2019 23:15

CCA dosn't affect voltage. CCA is amps. A 12v battery should maintain ~12v at all times no matter the size . 8.5v is very, very low - that and/or the fluctuation is wiping NVRAM is my guess....

Did you test the output from the replacement battery?

Edit: does your A/C work?

SATTV

1648 posts

Uber Geek

ID Verified

#2335815 11-Oct-2019 23:28

My guess is that you have another issue. possibly earthing.

Get a set of jumper leads and put one end on the ground of the batter and the other on the block ( I used to use a pulley arm or something like that, start you van and see if you get a large dip or remains about 12V

The other thing could be your starter motor wearing out, sometimes when they are failing they can draw more current than they should. Diesel engines require bigger starters due to the higher compression, so if you van is a diesel and smaller battery is not a good idea.

An auto electrician should be able to sort it fairly quickly.

John

I know enough to be dangerous

RunningMan

8953 posts

Uber Geek

#2335869 12-Oct-2019 08:23

K8Toledo:[snip]

CCA dosn't affect voltage. CCA is amps. A 12v battery should maintain ~12v at all times no matter the size . 8.5v is very, very low - that and/or the fluctuation is wiping NVRAM is my guess....

I don't think this is correct. CCA is related to the internal resistance of the battery. The more current you draw from any battery, the lower the voltage will go.

As I understand it, CCA is defined as the current that can be continuously drawn for a 30 second period maintaining a minimum voltage of 7.2v at an ambient temperature of -18 c. 8.5v is well above 7.2v, however may well be too low for the radio.

A battery with a higher CCA will have a lower internal resistance so will probably maintain a higher voltage under the same current draw.

Having said that, check for voltage drop across the earth strap(s), and compare the radio ground to battery ground voltage while cranking - that should tell you if it is a grounding issue.

Could just be a faulty starter that is drawing too much current.

k1w1k1d

1519 posts

Uber Geek

#2335872 12-Oct-2019 09:25

CCA is Cold Cranking Amps, -18C, 7.2V, 30 seconds.

Assume you have a diesel to need 750CCA battery. Guess it is a N70ZZ type. Fitting a 600CCA battery is asking for trouble.

Is 8.5v measured at the battery terminals?

Tests to do while cranking.

What is the voltage at the radio memory wire to chassis?

What is the voltage drop between the battery negative terminal and the engine block?

What is the voltage drop between the battery negative terminal and the chassis?

What is the voltage drop between the battery positive terminal and the starter positive stud?

What does cranking speed sound like, eg does it sound like it is labouring?

Do the glow plugs operate correctly?

As already suggested, a tired starter will draw more amps from the battery, causing a reduced voltage.
This extra current loads up the leads and voltage drops will increase.
Reduced battery CCA will also make the problem worse.

mb82

223 posts

Master Geek

#2335945 12-Oct-2019 13:10

Cable between battery negative and engine block did not make a difference.

It is diesel, ignition on drops voltage at terminals to 11.5 (while glow plugs heat).

If battery was weak, even with the current and new battery wired in parallel it does not change.

Voltage at radio harness is same as battery terminal whether it is grounded to radio harness or frame.

I do have a pretty decent multimeter true rms etc 8.5 volts, was measured by the 'minnimum record function' i put my cheap multimeter on which has no minimun voltage recorded function and it looks like it cranks at late 9's / early 10's.

Sounds ok while cranking, fires reasonably quickly.

Have not measured between bat -ve and chassis or bat +ve while cranking yet didn't want to keep running the starter but there is no drop with ignition off

SATTV

1648 posts

Uber Geek

ID Verified

#2336044 12-Oct-2019 18:59

mb82:

Have not measured between bat -ve and chassis or bat +ve while cranking yet didn't want to keep running the starter but there is no drop with ignition off

To do that you are better off with analogue meter, you can see the needle move rather than waiting for digits to do something.

John

I know enough to be dangerous

Technofreak

6530 posts

Uber Geek

Trusted

#2336110 12-Oct-2019 20:54

The radio likely has some form of battery for the memory to allow for drops in battery voltage like when starting or where the battery is disconnected for some reason. It may be a capacitor or button style battery and it's my guess this needs replacing.

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mb82

223 posts

Master Geek

#2336122 12-Oct-2019 21:47

Bat -ve to chassis was 395mv drop, bat +ve to starter stud was about 1mv.

Not many options left, maybe the radio is faulty.
I would have thought if the battery is weak / too small or the starter is pulling too much current, surely the problem would not remain when I have two 600cca batteries wired in parallel?

insane

3236 posts

Uber Geek

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#2336148 13-Oct-2019 00:27

I had a similar issue recently, but in reverse, where I needed to add a voltage regulator so that my reversing camera would work when the engine ran. (Worked fine on acc)

Perhaps you could install a big fat capacitor to smooth out the dip?

Mattmannz

471 posts

Ultimate Geek

#2336507 14-Oct-2019 08:33

What is the voltage reading at the memory wire whilst cranking?