Camper (Self-Build) Electrical Query - Laptop Charging

D_M_A · 17-08-2023 10:02am #1

Hi all, hoping to get some suggestions on the following.

I have a 12v electrical system in my self-build camper. I intentionally avoided installing a 230v system/inverter as I have no previous experience with electrics and I was learning as I go. I figured 12v would be sufficient for what I needed - lights, USB charger, 12v fridge, that's about it.

That being said, I thought it might be useful if I was able to charge my laptop in the van and possibly work while I travel. So I bought a small 150w inverter with the intention of charging the laptop on occasion. (Pics attached)

The problem is the laptop won't charge off the electrical system. Any ideas, based on the simple electrical diagram attached, why the laptop won't charge? Is it a case of the 150w inverter being too small? Should I upgrade to a larger one?

Or is the electrical system (usually delivering a constant 12.8v DC) not up to it?

When I plug the inverter + laptop into the cigarette socket in the cab (running off the starter battery) it charges fine, albeit slow.

Any suggestions?

Cheers

10-10-20 · 17-08-2023 10:17am

If it works off the starter 12v battery then it should really work fine off a healthy 12v AGM battery too! Does the laptop PSU and inverter come on while plugged in without the laptop attached, to the AGM battery or not?

We had this discussion recently which reminds me of this question:

https://www.boards.ie/discussion/2058308800/inverter-issue

I'd stick a DMM onto the AGM battery and measure the voltage while the laptop is plugged in. It should remain well over 12v.

Also can you hard-wire the inverter instead of using a cig-socket? Those often have contract resistance issues and start to overheat, especially with ~10a loads.

D_M_A · 17-08-2023 11:19am

https://www.boards.ie/discussion/comment/120989774#Comment_120989774

Thanks for the input 10-10-20.

When I plug the inverter in it powers up, fan starts running, and a solid green light is displayed. The voltage reading on the electrical panel reads 12.7v. Once I plug the laptop charger into it, the solid green light becomes a slow flashing green light. The laptop remains uncharged and the 12.7v reading remains the same.

I'm guessing the inverter isn't sufficient enough to provide power to the laptop charger so it's not drawing anything at all?

By my calcs, based on info below, the inverter is providing 120w / 230v = 0.52A to the laptop when it requires 1.9A?

Laptop Input;

100-240v ~ 1.9A

Inverter Spec;

Max Power Rating: 150w (4 Mins)

Continuous Power Rating: 120w (4 Hours)

Output Voltage: 230v +-10v

Input Voltage: 10-15v DC

10-10-20 · 17-08-2023 11:32am

That's odd if it works off the starter battery though. Was the vehicle running when you tested it? I'm thinking that maybe 12.7v is too low for 120w output and maybe if the vehicle was running the supply voltage was 13.8v? There is no documentation on the Ring site for that inverter unfortunately.

The other cause could be the surge current on some of those devices, it might be bringing the voltage down too far.

What happens if you unplug the laptop off the inverter when it's slow flashing green? Does it return to normal status? And what if you replug the laptop back in again, does it always go to slow flashing green again?

10-10-20 · 17-08-2023 11:35am

Hmmm - just reading some of the reviews on Amazon for that RINVU150... it's looking like it's a bit weak and the output AC voltage drops off quite a bit.

D_M_A · 17-08-2023 12:23pm

https://www.boards.ie/discussion/comment/120990102#Comment_120990102

Thanks 10-10-20

When charging off the starter battery I'd have the engine running. I'd be wary of the effects of charging a laptop for too long off this battery.

Yep, flashing green light when laptop is plugged in, and solid green when plugged out again.

Yea it's a relatively cheap product so may have to go for something a bit more substantial.

17-08-2023 3:05pm

The inverter should be able to supply the full 120W to your laptop charger - what is the stated charge rate of the block you are using, I can't imagine it is drawing a 120W. My dell charger is rated at 90W. If its a fairly cheap inverter sometimes the lack of pure sign wave upsets the charger.

D_M_A · 17-08-2023 4:21pm

https://www.boards.ie/discussion/comment/120991368#Comment_120991368

Thanks Shoog,

I'm not 100% on what your referring to when you say block. If you mean the laptop charger, the image below references 120.0W? This is the only wattage I can see indicated on the charger.

So maybe the charger is trying to draw 120w which the inverter should be (just about) able to provide but with drop-off or inefficiencies it's providing slightly less and therefore not providing the required charge?

17-08-2023 4:24pm

https://www.boards.ie/discussion/comment/120991694#Comment_120991694

That would be my guess. Can you get a slightly lower power charger for this application ?

Alternatively simply up inverter so that it has at least 50% margin - something like a 200-300W model.

10-10-20 · 17-08-2023 4:34pm

Another test:

Connect the laptop PSU to the laptop when it's powered off. See does it charge (it should). Then power on the laptop and see if it's drops off at that point?

spaceHopper · 18-08-2023 11:28am

My reading of the specs are that the laptop power brick outputs 120W to charge the laptop but it draws 190W (100V x 1.9A) and your invertor can't handle it. When the engine is running it might be able to do it as it's getting power from the alternator. Also if the picture of is of your wiring, I think it's to light and you need to beef it up.

120W from 12V is about 12.5A. You'd want deaccent wire between the battery and power board or 12V socket. Something like this 65W USB C charger might work all be it a bit slower

https://www.lenovo.com/gb/en/p/accessories-and-software/chargers-and-batteries/chargers/40ak0065ww?cid=uk:sem:am7ugn&gclid=Cj0KCQjwrfymBhCTARIsADXTabk9axUm9xnmL7U055gnKncfL6OuCpna0RMW2uEwQTZaT5ue3NoQENYaAqGwEALw_wcB&gclsrc=aw.ds

D_M_A · 18-08-2023 4:42pm

https://www.boards.ie/discussion/comment/120991759#Comment_120991759

So I tried this;

Plugged in the 150w Inverter - Fan starts up + solid green light comes on. Plugged the laptop charger into inverter (without laptop connected) - Solid green light turns to flashing green light. Connected laptop charger to laptop - Flashing green light remains, no power to laptop.

Interestingly, I tried the same thing with a phone charger;

Plugged in the 150w Inverter - Fan starts up + solid green light comes on. Plugged the phone charger into inverter (without phone connected) - Solid green light remains. Connected phone charger to phone - Solid green light remains, and phone begins to charge.

D_M_A · 18-08-2023 4:50pm

https://www.boards.ie/discussion/comment/120994991#Comment_120994991

Thanks for the input SpaceHopper - the wiring from the battery to the fuse board is a standard battery cable, and from the fuseboard to the 12v socket/cig port is 1.5mm 2-core cable so should be okay as far as I'm aware. Although, I must actually check the capacity of the 12v socket/cig port as that may not be up to it.

spaceHopper · 20-08-2023 9:27am

https://www.boards.ie/discussion/comment/120996991#Comment_120996991

"For instance, a 1.5mm2 wire has a standard current capacity rating of 10 amps (but it can carry up to 20 amps). It is, therefore, used primarily in lighting systems because most of them demand up to 7 amps, which falls within the “safe zone.”"

https://cablepro.net.au/wire-size-ampacity-and-circuit-breaker-current-ratings/#:~:text=For%20instance%2C%20a%201.5mm,within%20the%20%E2%80%9Csafe%20zone.%E2%80%9D

The wire is far to light, you should be looking at something much bigger. I'd look at a 12V charger you don't have losses in the DC-AC and in the AC to DC. You will have looses in the DC-DC but it will be less.

You also have to keep in mind that V= I * R so if you have 10 Amps through a 0.1Ohm wire you will see 1V across the wire and the appliance will see 11.7V. Even with a 0.05 Ohm wire you lose half a volt so it see 12.2V and will think the battery is near flat. It might work with the engine running because your alternator is generating over 13V

Calahonda52 · 21-08-2023 3:14pm

I have the same inverter and it only charged the laptop when engine running, its fine for phone charging

one advantage of a bigger inverter is that at low power requirement the fan stays off so I can charge my hearing aids at night without the fan running

CelticRambler · 25-09-2023 6:51pm

A bit late to this particular party, but I charge my laptops directly from the 12V output using this (specific model no longer available, but similar are):

https://www.trust.com/fr/product/18507-90w-plug-go-micro-laptop-charger-for-car-use-black

It obviously works best when the batteries are being charged from the alternator, but I'd regularly leave one or other laptop on charge in the middle of the day while there's enough light hitting the relevant solar panel and come back to fully-charged laptop and leisue batteries. Up-scaling 12V to 230V only to immediately convert it down to 19V is a waste of electrons!

Alkers · 22-10-2023 10:45pm

Rewire the 12v sockets with bigger cable.

What's the run length to the socket?

Camper (Self-Build) Electrical Query - Laptop Charging

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