9 volt batteries

[Big Rig Crawler]

This may be a really weird question but could a custom battery be made out of 9 volt rechargeable batteries?

 

[ultimate_monkey]

sure, but it wont work for a crawler, the discharge rate, mah ratesing would be way to low youd need a sh!t load of batteries wired in paralelle to get any sort of run time, and even at that the preformance would be uber lame

 

[Big Rig Crawler]

Okay Thanks, just one of my crazy ideas.

 

[Lorents]

:mrgreen: I guess its possible to run a 12V charger off 9V batteries... You would probably have to run two in series giving 18V and find a way to regulate that down to 12ish volts (unless you find a charger that runs of 12-24V or something like that). Each 9V battery typically have a capacity of 500 mAh.

So to charge a 2S (8.4V) 1500 mAh lipo you would in theory need 12.6 Wh (V x mAh / 1000). Running the 9V batteries in a 2S2P (4 batteries) configuration should give 18 Wh which in theory should be enough - BUT there are lots of other factors like heat and inefficiency during charging which you have to compensate for so you probably need 6 x 9V batteries so charge your battery once...

I think a 9V battery roughly have a 2C dischage rate giving 2A at 18V in 2S2P, 3A in a 2S3P which should be enough to charge your battery at 1C.

I based this on some 9V battery specs that I found on wikipedia. The batteries that you get could be better or worse than these specs so these calculations are probably inaccurate - but you get the idea

 

[Failedabortion]

:mrgreen: I guess its possible to run a 12V charger off 9V batteries... You would probably have to run two in series giving 18V and find a way to regulate that down to 12ish volts (unless you find a charger that runs of 12-24V or something like that). Each 9V battery typically have a capacity of 500 mAh.

So to charge a 2S (8.4V) 1500 mAh battery you would in theory need 12.6 Wh (V x mAh / 1000). Running the 9V batteries in a 2S2P (4 batteries) configuration should give 18 Wh which in theory should be enough - BUT there are lots of other factors like heat and inefficiency during charging which you have to compensate for so you probably need 6 x 9V batteries so charge your battery once...

I think a 9V battery roughly have a 2C dischage rate giving 2A at 18V in 2S2P, 3A in a 2S3P which should be enough to charge your battery at 1C.

I based this on some 9V battery specs that I found on wikipedia. The batteries that you get could be better or worse than these specs so these calculations are probably inaccurate - but you get the idea

Or you could pick up a cheap 4s pack like this for field charging...

http://hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9177

 

[Lorents]

... or something like this:

http://cgi.ebay.com/12V-7AH-12-Volt...emQQptZLH_DefaultDomain_0?hash=item3ef3180c70

 

[silentcircus]

... or something like this:

http://cgi.ebay.com/12V-7AH-12-Volt...emQQptZLH_DefaultDomain_0?hash=item3ef3180c70

Basically what I use, except for the brand of battery. Works perfectly.

 

[Failedabortion]

... or something like this:

http://cgi.ebay.com/12V-7AH-12-Volt...emQQptZLH_DefaultDomain_0?hash=item3ef3180c70

Wonder how long that batt would last at charging batts at 5a...?