UKH

Once you are driving can you have too many "things" plugged in to your car's electrical system?

Off on a family holiday soon, 5 people in the car - 4 of whom are old enough to have 'gadgets' that they get worried about when they don't have power in them. Additionally we have a cold box that can plug in to the 12v plug in the boot of the car.

My knowledge of the car electrical system is pretty limited, I know the battery is recharged from the alternator as you drive and have never had problems (except once in Sweden when I forgot to unplug the cold box when we had stopped and camped and needed to jump start the car the next morning from our friendly French campsite neighbours!). But could four phones, a gps, a Switch and cold box (it says 4 amps on its label), the car headlights, radio and a/c (is that electrical in part?) draw more power from the battery than the alternator is recharging?

Cheers all.

In reply to TobyA:

It’s very car dependant but a rough guide is below 3 litres the alternator can sustain 50 Amps.  I can’t see kid’s gadgets taking more than 1-2 Amps each.  Your load sounds fine.  Grab a cigar lighter voltmeter and keep half an eye on the voltage - as long as it stays above 13.5 volts you don’t need to worry.

Except in electric cars, aircon is almost always mechanical power.

Maybe make sure you know where the fuse box is, have a fuse extractor tool and some spares...

In reply to TobyA:

The gadgets shouldn't draw much (if any) power if they're fully charged so make sure they are before you leave and turn off wifi and bluetooth and the screen brightness down so that even less energy is used. 

In reply to TobyA:

I was on a desert drive in Namibia in a LWB Landrover where we had the A/C running and 5 phones being charged all at the same time. This caused the A/C to stop, and it only resumed once the phones had been unplugged and the battery got some recharging.

In reply to wintertree:

Thanks. Fortunately I do know where the fuses are and have some spare ones! in the past on old cars I have actually done things like change alternators and replace broken alternator brackets, so have had a car drain the battery whilst driving with the headlights on, so I do have a rough idea what is going on but my GCSE physics is so long ago I can never work out whether it's amps or volts or whatever that I need to be worried about! 😀

In reply to TobyA:

It’s watts you need to worry about. Most devices are now USB which is 5v so work out the current draw at 5v for the power rating of the device. I think an iPhone is about 0.5A on normal charge. That’s 2.5W. Which means 0.2A at 12 volts. 

The fridge will take a chunk but will have a thermostat so as long as it’s kept shut it shouldn’t use any current at all once it’s cold. Pre cool it before the journey and keep the door shut.

In reply to TobyA:

The days of 50A alternators were gone when I left school! A typical modern heap like my Ford Galaxy is 140A.

Normal drain is like dipped halogen lights 10A, fuel pump 4A, ignition system 6A, general crap 6A. The aircon itself is 4A for the clutch, 5A for the blower and 5-20A for the condensor fan or radiator fan if they aren't seperated. A few i-phones are of no  interest. The accessory circuit is normalky fused to 10A anyway.

In reply to TobyA:

Yes, but you'd be hard pressed to do it with phones, on a healthy car.

The two cigarette lighters in your car are likely to be separately fused at 10A each.

In reply to jimtitt:

I could have been clearer - I mean they can sustain 50 A above the car’s normal running load.

140 A is quite high I think; my Hilux is 105 A and my 325D is 90 A, although both of these are from the pre-infotainment/GPS era.  I seem to be crap out of luck looking for a replacement without an awful, low quality monitor shoehorned into and dominating the console.  Even the new MX-5 fastback has one.  It’s my most hated feature in our Leaf.  

In reply to wintertree:

The  Galaxy is designed as a family coach so two heaters and other stuff and primarily short runs, the alternator is either 120 or 140A depending on whether it has heated seats and other stuff.

My wife has a Subaru Forester and in the winter regularly (every 2 weeks) needs the battery charging, with all the junk turned ob it pulls a measured 112A out and the alternator is 110A, lucky if it puts out 50A going to work though!

In reply to TobyA:

I wouldn't worry about it. My van typically has 2 gas detectors on charge, 1 if not 2 mobile phones,a tablet, the lads E cig and a 500w inverter in the back charging a drill battery. The air con is never turned off summer or winter, even if I have the heat on in winter the air con is on because it dehumidifies and stops the inside of the screen being frozen.

Never had a charging problem on the battery. 

In reply to Dax H:

Cheers Dax. We did a big drive across Europe last summer when it was hot, so AC was on all the time, lights had to be on and various phones and games devices and GPS all plugged in with no problems, but its interesting to see the figures above - as I didn't really have any idea on how much power is going in and out of the battery.

Do you find the inverter works well? I bought one years ago in order to charge a laptop when we were doing big drives but it seemed not to produce enough power to really do it, maybe the battery would increase by a couple of percent over hours of driving. Maybe I bought a rubbish one, or they have improved in quality since then.

In reply to TobyA:

Some laptop chargers don’t get on with “modified sine wave” (cheap) inverters and need a decent pure sine wave inverter.  

In reply to wintertree:

The 12v fag-lighter socket will be fused at a fairly conservative limit (15-30A).  You'll blow this long before the load causes a problem for your car. I was reminded on this because I blew the fuse in my old van and replaced it with tin foil - if you're going to stack a lot of devices you may want to get some spare fuses before you go!

I can confirm that cheap square wave inverters do not work with neat little laptop power supplies - you do need a sine-wave inverter or better still get a 12v charger - I think I got a cheap 3rd party one for my laptop at a fraction of the cost of an inverter.

I'd also recommend using a USB charger powerbank to provide spare juice when the engine is off - this is far more convenient than running down the main battery and needing a jump start. Netter still get one of those dual purpose powerbanks that will jump start your car as well (they do work).

A cool box left on when the car engine is off will flatten your battery quite quickly.

In reply to TobyA: Going off on a tangent, It can put more load on the drive train I've been told (something to do with higher torque in the reverse and lower gears), but a family friend and I hit upon bump starting his van backwards recently, after his van battery randomly went flat. I don't know if he's pondered why, since.

In reply to TobyA:

I find the inverter excelent. My last one was 300w and wired direct to the battery. I run 2 batteries in my drill and impact driver, mainly the driver gets used. Battery goes I get the spare and put the dud on charge. Next morning it's good to go again. That inverter burned out after 5 years though so this time it's 500w to a switched live socket in the back. I'm hoping that because I drive between sites a lot the battery will charge okay then but if not I will run a separate live to it again. 

In reply to TobyA:

As wintertree said. It won't be the power output it'll be the poor AC sine wave. You need to get one with a better sine wave output or get a DC laptop charger. Most laptop chargers are doing 230V AC to 19V DC, so with the inverter you're going 12V DC to 230V AC to 19V DC. It's more efficient with a DC charger as it's just 12V DC to 19V DC.

In reply to TobyA:

Back in t'day, the only worries we nippers had was if Mum had packed enough sarnies and remembered the I-Spy books ...

(sorry, but some old git had to say it! )

In reply to McHeath:

Yes and no seatbelts so you could lie down or fight your brother (literally anywhere in the back area of the car) when bored

In reply to McHeath:

I find it really distracting when someone has a tv on the head restraint, find out hard to avoid tailgating as I try to see what they are watching. 

Oh and yes don't don't kids get carsick these days? Watching a screen is guaranteed to leave me getting queesy. 

In reply to mountainbagger:

not to mention shiny sticky seats in hot weather

In reply to mountainbagger:

Lying on the floor watching the tarmac going past through the gaps under the doors!