voltage fluctuations while using laptop

[Blue Fox]

When I connect my laptop to the boardnet my voltmeter shows strong fluctuations: between 11 and 13 volt. It can be so extreme that for instance the gps is (temporarily) turning off. It disappears if I run the laptop without battery.
I have 210 Ah batterycapacity - should be more than enough. Could this be caused by the 'express' charging that my (Dell) 12V adaptor is trying to do?

 

[cliff]

I am only guessing here so am probably way off course but I am guessing you have a take-off point beside the nav table and that is where your instruments are. One feed cable coming from the switch panel feeding the instruments (and laptop charger). Voltage drop straightaway. I have/had a similar problem when I switch(ed) on the plotter, voltage at the nav table dropped to 11v or less as measured by the multi repeater on the nav table while the battery meter (connected at the switch/distribution panel) still showed 12.4v. Sorted by running two new heavier gauge cables from the switch/distribution panel to the nav table, one for the plotter and one for the remaining instruments.

Try connecting your laptop charger directly across the battery and see what happens.
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"Artificial intelligence is no match for natural stupidity"

 

[steverow]

This could be a couple of things.
Could be voltage drop between the battery and the point at which your laptop takes the power, usually caused by the cable being of insufficient capacity (thickness).
Could be the batteries themselves either insufficiently charged or maybe you have a failing cell in one of the banks.
First check should be of the batteries with a hygrometer (glass bulb siphon) to check the specific gravity of each cell.
Once that is done I would then start to look for other issues such as cabling problems.

You can get a battery hygrometer at most car accessory shops.

Most laptops will draw about 2.5 to 3 amps at their rated input voltage.

How are you actually connecting the laptop to the ships supply...??via a voltage converter??


Hope this helps

Steve

 

[Blue Fox]

My batteries are nearly new and fully charged. I am using the official 12 - 19.5 volt adaptor from Dell. I have two sockets - both give the same characteristics. But of course it could be that the cabling is too thin, although I never had problems with f.i. the loose Waeco icebox I sometimes connect. But even if the cabling is inadequate - why the fluctuations?

 

[cliff]

The Dell batteries have built-in charge control circuitry - I opened one once hoping to change the cells - mistake - the internals are rather complex complete with circuit boards and IC's. Fluctuations would be due to the battery's charging cycle which is controlled by the battery itself not by the power supply.
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"Artificial intelligence is no match for natural stupidity"

 

[andy_wilson]

All LiIon batteries charge by a pulse method. It may diminish as the battery reaches full charge, so the answer may be to keep it toppped up.

 

[Rivers & creeks]

I had a similar problem until I took the power straight from the battery terminals (in-line fused of course). As long as it was going through the switch panel it was affecting other instruments. This was the case either for DC power or via an inverter.