Field charging lipos using car battery

[Kwaz]

Hi,

Can anyone tell me how many 3S 2200mah batteries I could charge safely from my car battery? (without running the car engine in between charges)

I am using the new hyperion G3 batteries and charge at 6A - one battery takes around 20 mins to charge.

Would like the option to charge from my car battery but worried I might drain the car battery very quickly pulling 6A, and I won't have enough juice to re-start the car!!

Anyone know?

[zxyong]

That will depend on the capacity of the car battery

[flightsimmer]

what kind of batt you using? How come can charge 6a? I thought 2200ma safe is 2.2a?

[Kwaz]

@zxyong - I appreciate it will depend on my car battery capacity. But if we say my car battery capacity is 'X' then what is the relationship between 'X' and the requirements outlined about


@flightsimmer - these are the new hyperion G3 lipo batteries. You can buy them from SkyHobbies. The manufacturer states they are safe to charge at 5C. So actually I could charge them at 5 x 2.2 = 11A (!) But my charger only goes up to 6A

[zxyong]

Lets assume your car battery is 6600mah, theorecitcally you can charge 3 x 2200mah batteries, but there will be some loss somewhere so end up some capacity will be wasted. So practically, you can fully charge less than 3 2200mah lipo with a 6600mah car battery.

Pulling out how much amp at a time does not have a direct impact, it just charge faster, but it might create more heat though... Theorectically charging at 6A is the same as charging at 2A, just that its 3 times faster.

This is from electrical point of view, i havent tried charging that way before. Maybe some experience guys can advise more on this.

[Kwaz]

Lets assume your car battery is 6600mah, theorecitcally you can charge 3 x 2200mah batteries, but there will be some loss somewhere so end up some capacity will be wasted. So practically, you can fully charge less than 3 2200mah lipo with a 6600mah car battery.

Pulling out how much amp at a time does not have a direct impact, it just charge faster, but it might create more heat though... Theorectically charging at 6A is the same as charging at 2A, just that its 3 times faster.

This is from electrical point of view, i havent tried charging that way before. Maybe some experience guys can advise more on this.

makes sens thanks. I have no idea what mah my car battery is though or even what the average is for most vehicles. Maybe it's written on the car battery somewhere.

[Sunstorm]

IIRC Car battery is 30Amp hours.

Some of the bros just let their car engine run idle.

[blueangel]

30 amp-hours can charge at least 10 X 2200mAh packs.
3 packs should be safe.

Product of any combination ( hours, amperage ) should not exceed 30 amp-hours, technically.

But give and take 20% losses due to heat and electrical losses.

[Kwaz]

Thanks everyone!

[jansonfinn]

30 amp-hours can charge at least 10 X 2200mAh packs.
3 packs should be safe.

Product of any combination ( hours, amperage ) should not exceed 30 amp-hours, technically.

But give and take 20% losses due to heat and electrical losses.

n the loss due to the powering of the charger as well

[etman]

Bro, IMHO, you run the risk of your car battery dying. Also waste fuel running at idle. Better get a spare battery put in your boot and charge it from home.
Or get more Lipos...

[Sunstorm]

Some of the other guys do use lead acid batteries to field charge their lipos, but they sure are heavy things to lug around.

It's up to you what you wish to use.

I won't want to charge lipos in my car as I'm paranoid about catching fires and stuff. Hence I use only what lipos I have. Anyway not all the time spent at FF is about flying, you also chit chat with the other bros, ogle other ppl's planes, field repairs etc.

[blueangel]

n the loss due to the powering of the charger as well

That is electrical and heat losses as well right bro ? You confusing me..

Anyway I would prefer to do all the dirty jobs at home by charging all the Lipos up over the non-flying weekdays and then once hit weekend, bring all the batteries to the field and fly until either the batteries are used up, plane wreck-up or sky black out..

[Sunstorm]

Well with some of the bros on 5C chargeable batteries, it's possible now to charge batts in between flights. 5C means can full charge in 12 mins.

Anyway we don't use up the batts to their full capacity, normally we pump back about 50-75% of their capacity.