Where has my volt gone? Logic please!

[Jabstatt]

Victron MPPT on a 120W panel charging the truck battery only.
Battery fully charged, 12.8v at the battery.
Zero current from the MPPT to the battery.
Voltage at the MPPT Battery connection is 13.9 in brilliant sunshine.

I don't understand since there is no current flowing in the circuit.

Much appreciate any input, please!


Thanks
Tony

 

[Lenny HB]

How are you measuring the current?
I would put a clamp meter on the cable to check.

 

[Jabstatt]

Measuring it at the MPPT and with a DC Clamp meter!

Its magic!

Tony

 

[Mike800966]

I would check it with an analogue meter!
Also put that meter between the same wires from source and battery on a low range, you should see the voltage difference between the ends.
Mike

 

[Jabstatt]

Yes, I think the next action is to use my Avo 8 and measure each individual cable drop.

My multimeter is a Fluke and is not many years out of Cal. If only I was still working….

It is defying logic.

Thank you.
Tony

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[Figaro]

Victron MPPT on a 120W panel charging the truck battery only.
Battery fully charged, 12.8v at the battery.
Zero current from the MPPT to the battery.
Voltage at the MPPT Battery connection is 13.9 in brilliant sunshine.

I don't understand since there is no current flowing in the circuit.

Much appreciate any input, please!


Thanks
Tony

Surely if the battery is fully charged the solar controller will shut down until it detects a drain on the battery ?

Or maybe I've misunderstood your problem

 

[Kannon Fodda]

If the battery is fully charged surely there will be no current into it as it can't accept any? Thus the mppt has shut off?

 

[Affinite]

I would have thought that once the MPPT thinks the battery is fully charged, it will go into float mode and maintain a steady voltage of around 13.6V. If there is a difference in voltage between MPPT battery terminals and the battery itself, it must be a broken connection somewhere between charger and battery. (Unless your measurements are incorrect.)

 

[donkey]

I think your battery is not actually connected to your MPPT controller. possibly a bad connection or a blown fuse in the circuit.

Geoff

 

[Jabstatt]

I think your battery is not actually connected to your MPPT controller. possibly a bad connection or a blown fuse in the circuit.

Geoff

That is what I’m beginning to think but the van sits in storage then starts really easily!

Thanks.

More dismantling called for. Why is life never simple. I think ill run a new cable through anyway.

Tony

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[Figaro]

That is what I’m beginning to think but the van sits in storage then starts really easily!

Thanks.

More dismantling called for. Why is life never simple. I think ill run a new cable through anyway.

Tony

It should be quite easy to identify the problem if you have a multimeter.
Test voltage on solar controller panel input, then output , then leisure battery terminals.

The readings should give you enough information.
If all looks good but no output from controller then switch on all the habitation lights and see if the controller comes to life.

Full disclosure: no expert, just what I've learnt from being on here

 

[Jabstatt]

The point is dropping a volt in a cable with no current flowing.

Breaks the laws of physics!

It’s the starter battery not habitation!

Tony

 

[autorouter]

Is it a dual output MPPT? If so, what is the other output showing?

 

[Jabstatt]

Single MPPT!
Simple circuit, deliberately designed to stand alone.

Tony

 

[pappajohn]

Does it really matter as long as the battery is kept charged and not overcharged.

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[Affinite]

The point is dropping a volt in a cable with no current flowing.

Breaks the laws of physics!

It’s the starter battery not habitation!

Tony

Not if the battery is happy sitting at 12.8V and the MPPT is happily putting out 13.9V but there is no electrical connection between the two. eg a fuse has blown

 

[autorouter]

The point is dropping a volt in a cable with no current flowing.

Breaks the laws of physics!

There are several loopholes in the standard laws that those pesky electrons can exploit. If there's any corrosion on a fuse or any joint, the corrosion products (oxides etc) can drop voltages without passing a current, acting a bit like a diode does. Older funsters may possibly remember selenium oxide rectifier diodes that were used on motorbike dynamos before cheaper better silicon diodes became widespread. Oxide layers can act like those.

If one of those corrosion products acts a bit like a semiconductor material, then the interface with the metal wire can act like a diode too - similar to Schottky diodes which are metal/semiconductor devices. Some wicked electrons can even sneak through an insulating barrier by quantum mechanical tunnelling, like they do in a Zener diode.

But more likely there's a break in the wire somewhere.

 

[DBK]

Do you know if there is a Battery Master or something similar fitted? 12.8 volts is at the upper end of the resting voltage for a lead acid battery. I would have expected something nearer 12.6 but perhaps you have an AGM battery which I understand does have a higher voltage.