How long to charge a 2nd battery jumpered to a running car

worded

I’ve a spare car battery I want to bring camping close to my car

The spare battery will be hooked up to a fan assisted cool box for food

If it runs out of power I can disconnect it from the cool box and jumper it to my running car just to charge it of it doesn’t take too long. Approx how long will it take to charge?

TomOnBoard

worded wrote: »

I’ve a spare car battery I want to bring camping close to my car

The spare battery will be hooked up to a fan assisted cool box for food

If it runs out of power I can disconnect it from the cool box and jumper it to my running car just to charge it of it doesn’t take too long. Approx how long will it take to charge?

Too many variables; too little data... For example, what are:

Alternator output
Car battery capacity
Spare battery capacity

It's not going to be as simple as just jumpering. You will need some kind of split charging circuit to ensure one battery wont mess with the other and/or strain the Alternator.

Jump starting a car in a grassy campsite ain't fun...

worded

TomOnBoard wrote: »

Too many variables; too little data... For example, what are:

Alternator output
Car battery capacity
Spare battery capacity

It's not going to be as simple as just jumpering. You will need some kind of split charging circuit to ensure one battery wont mess with the other and/or strain the Alternator.

Ok so I need a car battery charger ideally really. I risk my car electronics charging the second battery fully

Or

I can swap out the batteries beofre I go and make sure the spare is fully charged

Tonight I’m testing the spare battery hooked up to the cool box to see how long it will last, if even 12 hours

It’s a crazy plan but it just might work ... for a few hours :-)

_Brian

Could you not camp at a site with EHU ?

It would save a huge amount of arsing about.

worded

_Brian wrote: »

Could you not camp at a site with EHU ?

It would save a huge amount of arsing about.

It will be at a festival so it won’t be that organised for
Electricity

biko

An idling car will charge the external battery, but very slowly.
A car needs to be driving to charge properly.
The alternator is not producing enough current to charge car's internal battery, and also the external battery.
It's a possibility that you actually drain the internal battery.

Yeah, just test it out and see how much you get.

Uncharted

Buy a 12v cooler box. You obviously have a vehicle to charge from so keep it on a trickle charge for the festival. Best solution all round.

iamtony

biko wrote: »

An idling car will charge the external battery, but very slowly.
A car needs to be driving to charge properly.
The alternator is not producing enough current to charge car's internal battery, and also the external battery.
It's a possibility that you actually drain the internal battery.

Yeah, just test it out and see how much you get.

Biko, I'm guessing your pretty old and learned about alternators back in the day but alternators these days will charge a battery at near full capacity on idle.
Op you'll need to leave the battery charging for a couple of hours to get a decent charge.

iamtony

Uncharted wrote: »

Buy a 12v cooler box. You obviously have a vehicle to charge from so keep it on a trickle charge for the festival. Best solution all round.

Unless he's willing to leave the engine running a 12v cooler will leave his car battery flat in a very short space of time, they use a lot of juice.

iamtony

worded wrote: »

I’ve a spare car battery I want to bring camping close to my car

The spare battery will be hooked up to a fan assisted cool box for food

If it runs out of power I can disconnect it from the cool box and jumper it to my running car just to charge it of it doesn’t take too long. Approx how long will it take to charge?

How long is the festival and what are you keeping cool? If its only a day or two and they sell ice I'd just fill the cooler with ice a couple of times a day.

_Brian

Uncharted wrote: »

Buy a 12v cooler box. You obviously have a vehicle to charge from so keep it on a trickle charge for the festival. Best solution all round.

Most cars now stop the aux socket with the ignition or cut off everything when battery power dropped a bit and the engine not running.

Charge the battery before you go and see how it goes. It’s a festival not a 5* hotel. What do you need a cooler for?

ED E

Get yourself a lipo bank, one of the survivalist units for example, significantly more capacity for less weight.

iamtony

_Brian wrote: »

Most cars now stop the aux socket with the ignition or cut off everything when battery power dropped a bit and the engine not running.

Charge the battery before you go and see how it goes. It’s a festival not a 5* hotel. What do you need a cooler for?

If the car has more the one 12v socket it's not unusual for power to be constantly supplied to the one in the boot for instance.

evolving_doors

iamtony wrote: »

Biko, I'm guessing your pretty old and learned about alternators back in the day but alternators these days will charge a battery at near full capacity on idle.
Op you'll need to leave the battery charging for a couple of hours to get a decent charge.

iamtony

evolving_doors wrote: »

Reading it back looks bad! In my head it sounded so much more lighthearted. I've got posters remorse now:)

Uncharted

iamtony wrote: »

Unless he's willing to leave the engine running a 12v cooler will leave his car battery flat in a very short space of time, they use a lot of juice.

Perhas I wasn't clear enough. Im suggesting it being fully charged upon arrival. That will remain cold all day.

The following day,run the car for a half hour to boost it a little.

iamtony

Uncharted wrote: »

Perhas I wasn't clear enough. Im suggesting it being fully charged upon arrival. That will remain cold all day.

The following day,run the car for a half hour to boost it a little.

Pretty easy to figure out if you find out how many amps the cooler uses and the capacity of the battery.

Uncharted

On second thoughts OP,man up and just go with the flow. It's a festival. You're not supposed to have any creature comforts :pac:

_Brian

Also a regular battery willl be ruined running it flat and recharging.

You need a specific leisure battery for that application.

Toyotafanboi

iamtony wrote: »

Reading it back looks bad! In my head it sounded so much more lighthearted. I've got posters remorse now:)

Banned!

Henry Ford III

Decent battery charger. 24 hours. Sorted.

worded

Im bringing kids with me and was hoping to cook breakfast on morn 1 morn 2.
May just have breakfast on morning 1.

Being able to keep the raw food cold and have some milk for coffee / porridge would be really great.

Bringing some UHT milk anyway for coffee.

Also to keep beers cooler than luke warm would be good.

biko

Hmm, old eh?

Anyway, OP do you really want to leave car idling for as long as it will take to charge up a battery? 2 hours?
Besides fuel costs it may not be popular with other people around, noise and smell of exhaust etc

TomOnBoard

Uncharted wrote: »

On second thoughts OP,man up and just go with the flow. It's a festival. You're not supposed to have any creature comforts :pac:

Yeah, after day 1, loo roll will be a pure luxury!

TomOnBoard

Henry Ford III wrote: »

Decent battery charger. 24 hours. Sorted.

Ahem! Using what exactly to power the charger?

JohnBoy26

Just a thought but a gel battery would be a good bet. A gel battery ain't cheap but fully charged they last much longer than a regular battery.

On jump leads it will take an age for a battery to charge sufficiently.