Hi guys,

Can you pls highlight the danger of charging LiPo on car battery as we keep the battery on car bonnet which is metal.  Can an short circuit in Lipo charger cause any problem with car's electrical system and cause a major fire in the vehicle?

This is one of the concerns about charging directly from the car batteries.  Please see this discussion (especially the links in the second page).

http://www.rcindia.org/batteries-and-chargers/charging-a-battery-on-the-go/

i suggest u buy a 500rs sla ups type battery.! i bought one and it works great and u can charge 3-4 times on the field!

Yep, that is one thing that seems unanimous !  Buy a deep discharge battery meant for inverters / UPS, that is a safer option.

Quote from: amulu10 on January 10, 2010, 08:49:49 AM
i suggest u buy a 500rs sla ups type battery.! i bought one and it works great and u can charge 10 + times on the field!

Depending on what size lipoly you can charge. Considering its not a good idea to discharge a lead acid battery below 50%, a 7AH 12 volts battery should not be used to charge a 3S1P 2.2 AH lipo twice, considering some efficiency loss and the current used by the chargers LCD.

If I were to buy a battery for this purpose then I would have got an AMARON QUANTA UPS battery 40 AH, rather than using a car battery or a 500 rs battery.

http://www.amararaja.co.in/quanta.asp
http://www.amararaja.co.in/pdf/Quanta.pdf

Again depends on how much you use. Its worth the investment if you fly electric a lot. I use 2 X 65 AH with my APC UPS and they ROCK. the best batteries money can buy in my opinion and recommended by APC.

Quote from: vinay on January 10, 2010, 09:52:03 AM
Depending on what size lipoly you can charge. Considering its not a good idea to discharge a lead acid battery below 50%, a 7AH 12 volts battery should not be used to charge a 3S1P 2.2 AH lipo twice, considering some efficiency loss and the current used by the chargers LCD.

ya u are right ! my bad ,u cant charge a 3s 2.2 with 7ah batteries. i was talking about 7.2 v /11.1 800mah batteries i use! 

I charged my 3s-4s LiPo's using my Car Battery all my life.. I never had any problems... My car battery is still going strong.

Quote from: jerryazhakathu on January 10, 2010, 01:06:57 PM
I charged my 3s-4s LiPo's using my Car Battery all my life.. I never had any problems... My car battery is still going strong.

Agreed, depending on how much you charge, they are not designed for deep discharging. Also its not safe to charge inside a car, or with the bonnet open.

Though accidents RARELY happens, they still happen. Its ok for light recharging, but not recommended if you drive the cars only on weekends that too for shorter distance.

hi,

I still feel the car battery will give a high charging current if you connect the batteries together without any balance charger in between.

QuoteI still feel the car battery will give a high charging current if you connect the batteries together without any balance charger in between

I am not able to understand what you mean. If you are referring to "connecting the batteries together" as putting them in "parallel" then you are asking for big trouble!

I think you mean that the battery should go through a charger to control/limit the current. The balancing aspect is a separate issue.

And I repeat, several fliers at our field use the car battery for charging. With 3S 2-3 A batteries there is no problem for 2-3  charges - which  is typical and more than adequate for a flying session. Most have one extra battery, anyway.