laptop computer charger >>solar charge controller >>battery?

[John61CT]

Bear Stanley cooked some righteous windowpane back in the day.

Yes helped open our inner eyes

but lots of collateral damage there when gentler organics were available.

Look up Fleetwood Mac co-founder Peter Green's party at the Highfisch-Kommune in Munich.

Wasn't all rainbows and patchouli, God lost a lot of angels

[tony.latham]

Bear Stanley cooked...

Wrong forum maybe?

T

[Tom&Shelly]

Bear Stanley cooked...

Wrong forum maybe?

T

Might be more appropriate in the "trips" folder.

Tom

[Bob Hammond]

I see that a misunderstanding has occurred in the course the discussion. This is >not< about charging a laptop.

It is about charging the 12VDC SLA/AGM battery in the trailer with a surplus laptop charger that is rated 3.4A @19VDC. The idea is to use the solar charge controller to regulate the charger's output so as to charge the trailer battery and then keep a float charge going. The advantage would be having a very small, shore powered charger permanently in the trailer for cloudy days, instead of carrying a large automotive-type charger.

To that end, I checked the output waveform of the laptop charger on my oscilloscope and checked the DC output voltage. The output is very clean - no spikes or ripples and 19.9VDC. In daylight my 100W solar panel output varies from about 15 to 21VDC, depending on the amount of light on the panel.

[Bob Hammond]

I see that a misunderstanding has occurred in the course the discussion. This is >not< about charging a laptop.

It is about charging the 12VDC SLA/AGM battery in the trailer with a surplus laptop charger that is rated 3.4A @19VDC. The idea is to use the solar charge controller to regulate the charger's output so as to charge the trailer battery and then keep a float charge going. The advantage would be having a very small, shore powered charger permanently in the trailer for cloudy days, instead of carrying a large automotive-type charger.

To that end, I checked the output waveform of the laptop charger on my oscilloscope and checked the DC output voltage. The output is very clean - no spikes or ripples and 19.9VDC. In daylight my 100W solar panel output varies from about 15 to 21VDC, depending on the amount of light on the panel.

[pchast]

I'm guessing but it sounds like it should work well........

[Bob Hammond]

Some weeks ago, I theorized that a computer laptop charger could be used to power my trailer's devices and charge the battery on cloudy days when shorepower is available. Most people seemed to think that idea was 'out there'.

Well, I got around to connecting up the laptop charger to the PWM solar controller today, in place of the solar panel.

>>>>A word of caution here:
My solar controller is a PWM 'Moohoo' 30A brand. I can't say that it will work with other PWM chargers or with MPPT chargers. I was thinking that if I destroyed the charger or controller, that the charger would be no loss, and I was planning to upgrade the controller to a MPPT type anyway.

You're on your own about that.<<<<<

It works.

1. The no-load output voltage/amps of the laptop charger is 19.1 VDC (@ 3.4A), which is the same voltage as my 100W solar panel in full sunlight.
2. After connecting the charger in place of the solar panel, the solar controller reads the voltage from the laptop charger at 12.7V DC.
3. I turned on all the power consuming devices (lights, fans, USB) in the trailer with the exception of the CPAP machine, drawing about 23 watts.
4. The solar controller held the voltage at ~12.4VDC, supplying about 2.3A from the laptop charger, but not sending any current to the trailer battery (it's charged at ~13.3V).
5. At the connection of the laptop charger to the solar controller, the voltage oscillated between 12.9V and 11.4V

Since the trailer battery is charged at ~13.3V, the solar controller is not charging the trailer battery, but it is supplying current at 12.7V to all of devices that are drawing power. The next test, is to draw the trailer battery down to 12-12.4V, and then see if the laptop charger can charge the trailer battery through the solar controller.

So for today, I'll call this experiment a success. Instead of taking along a heavy/bulky full-sized auto battery charger in case of a cloudy day (and where shore power is available), I can charge the trailer battery or operate the trailers electrical accessories from the laptop charger. During times when the trailer is unused, I can use the laptop charger to keep the battery topped up.

[featherliteCT1]

Bob,

Thanks for posting ... that is some very good data.

[Bob Hammond]

Here's a pic of the charger with a SAE DC power connector grafted on to it. The charger is connected when the solar panel is disconnected. While it is possible to wire the charger directly to the controller's terminals for the solar panel, I think it might be better to do it with a connector so that it's not possible to have both the charger and the solar panel connected simultaneously.

[Bob Hammond]

Update

It did not work as well as I wished. But it did not damage the solar charge controller.