Charging batteries via the Car

[wozza]

Hey guys,

Any experience with charging batteries using the car's battery?

Want to take my Pro-peak to the weekender and connect it via the crock clips. Will this drain my car's battery or do they not take much out of them?

Or is it best to leave the car running whilst charging?

Cheers.

[windywindmill]

Re: Charging batteries via the Car

There's a video guide on there for hooking chargers up to the car on YouTube, sure it was done by richardy. You'd get away with hooking it up for half hour - an hour then I'd put the engine on for ten mins

[wozza]

Re: Charging batteries via the Car

Cheers bud, I imagine that there will be a few flat cars come sunday evening, got my jump leads just in case.

[windywindmill]

Re: Charging batteries via the Car

Yeah I'm going off the car now, was trying to borrow a generator but it fell through.

[S3V3R]

Re: Charging batteries via the Car

Try a 12v inverter as well. You can buy main sockets that plug into the cigarette lighter socket and step up to 240 volts.

Be very careful when connecting up directly to the car battery. Lots can go wrong if you're careless!

[Boo-Sabum Ben]

Re: Charging batteries via the Car

Doesnt the car have to be moving for the battery to be charged? I thought if you left the car standing still with the engine running, itd still be empty next time

[wozza]

Re: Charging batteries via the Car

The alternator will still be running on tick-over to charge the battery.

I believe to charge the battery quicker you take it for a run to increase the revs and hence the charge rate.

[JOE90]

Re: Charging batteries via the Car

Doesnt the car have to be moving for the battery to be charged? I thought if you left the car standing still with the engine running, itd still be empty next time

As long as its running then the alternater is charging the battery

[thekonassure]

Re: Charging batteries via the Car

To use the fast charge on a pro-peaks you need to give it an AC supply I think or at-least you do to run it at 9.6v so you will need an inverter.

Best thing is to fast charge a battery will only take around 10 to 15mins so you wont have to leave your car running long better then taking hours over it.

[Sam_s.o]

Re: Charging batteries via the Car

A car battery (lead acid thin plate engine starting) will crank most petrol engines when it is at 12.1v which is around 50% state of charge so If you have a 86ah battery you can dis harge it by 43ah before you won't be able to start your engine so say you have a 5amP charger and at worst it has an efficientcy of 0.5 then it would take 4 hours of discharge before you couldn't start your car. So unless u struggle to start your car after it has been stood don't worry about starting it.

[thekonassure]

Re: Charging batteries via the Car

True but if he uses an inverter it will take more power.

Also I`m sure there will be loads of people there so you should be able to get a jump easy just leave the lights on lol

[S3V3R]

Re: Charging batteries via the Car

Surely if you leave the car engine on whilst using an inverter it will be alright? Fast charge for 10 minutes, then leave the engine on for another 10 minutes to make sure the battery has enough charge to turn the car on again?
Also, the inverter I have has a max of 75W @240V I doubt in a 10-30minute charge you would discharge the battery?

But as you said Konassure, worse comes to worse, there are 1600 people there, someone is bound to have jump leads!

[thekonassure]

Re: Charging batteries via the Car

yeah it will be fine a car alternator can put out between 30 and 60 amps depending on the model maybe more, there`s no way your going to drain that much you`d blow the 10amp fuse in the pro-peaks

You do get what mechanics call a "lazy" alternator they provide less then the amount of power needed on tick over to charge the battery and if left running for anything from 1 to 6 hours with no rev`s the bat dies but that`s really not an issue on more modern cars. The ecu will monitor the output of the alternator and up the tick over rev`s a bit if needed.

Still old school people like to give the accelerator a little poke every now and then.

[Sam_s.o]

Re: Charging batteries via the Car

even if you have a quasi sign wave (cheap) inverter it will have a 0.8 to 0.9 efficientcy rating so if your charger draws 10amps at 12v wich is 120W (unlikely but hey) at 230 it will draw 0.5 amps at 230v so the inverter will draw 0.5 divide that by 0.8 (efficiency rating) = 0.625a at 230v so 143.75W = 11.98A at 12v so you can still run it for almost 4 hours without the alternator.


Car alternators are odd things.
most cars have whats known as mechanically sensing meaning they are timed they will charge at bulk (as high output as it can rev dependent) this is normally between 20mins and an hour and is at between 13.9-15 volts dependant on the battery type model ect. It will then go into float or trickle charge this is normally at 13.7v and at between .5a - 15a as the idea is not to over charge the battery and have it vent or go into thermal run away.

again if you rev your engine as said above the alternatator is capable of producing more energy but if it is in float it will only produce a limited output at a voltage which will not encourage recharge if the battery is below 80% so it will only carry any loads you have on at this time and not fully recharge.

Basically in short u can run the charger from the battery and not worry if you run it from the alternator there will be little to no point runing it for more than an hour if the engine is sat at idel.

[thekonassure]

Re: Charging batteries via the Car

oh sam you did full time collage did`nt you not just that 1 day a week work in the garage the rest of the time "apprenticeship" ? lol

Still great if you can remember all of your theory to that level of detail, was never big on electric`s myself I like the stuff I could hit lol