what is mAh? can i use a higher mAh? - RC Groups
Oct 16, 2005, 06:59 PM
Registered User

# what is mAh? can i use a higher mAh?

hey
another total newb question from me I have a 7.2V 1700mAh battery for my electric r/c car. If i were to buy a battery, would it have to be a 7.2V 1700mAh battery, or can I go for a 7.2V 3000mAh battery!? tahnks again guys
 Oct 16, 2005, 07:01 PM Jim Yep. Go for the 3000mah. Just means a longer run.
 Oct 16, 2005, 07:02 PM Suspended Account "mAh" is the capacity of the battery. Silent
 Oct 16, 2005, 07:04 PM Registered User thanks guys really do appreciate it
 Oct 16, 2005, 07:04 PM Power in the hands of few The issues are size & weight. Go as big as you can, but not so big or heavy as to not fit in the car.
 Oct 16, 2005, 08:28 PM Registered User so if a car comes with 7.2V 1200mAh, it wont do any damage to the car or motor because a newer battery is 7.2V 3000mAh?
 Oct 16, 2005, 08:47 PM Registered User I had the same question before, my freind explained it to me like having a bigger gas tank in your car. Lexi
 Oct 16, 2005, 11:55 PM Registered User The mah rating on the battery is like the size of the gas tank on a car like Lexi mentioned. Here is one way to look at it. Someone please correct me if I'm wrong. A battery's capacity is rated in mah or milliamp hours. A 1700 mah battery is rated to deliver 1700 mah (or 1.7 amps) per minute for one hour. So this battery will deliver 102,000 mah (or 102amps) in one hour. 1700 mah x 60 minutes = 102,000 mah. Now take the amp draw of your car motor. Let's just say it pulls 20 amps or 20,000 mah. Take the capacity of the battery which is 102,000 mah or 102 amps. Divide by 20,000 mah or 20 amps, which the motor is pulling and you get a total motor runtime of 5.1 min. i.e. (102,000 / 20,000) So a basic formula could be; total motor runtime = (battery mah capacity x 60) / motor amp draw for your 1700 mah battery; total motor runtime = (1700 mah x 60) / 20,000 total motor runtime = 102,000 / 20,000 total motor runtime = 5.10 min. for a 3000 mah battery; total motor runtime = (3000 mah x 60) / 20,000 total motor runtime = 180,000 / 20,000 total motor runtime = 9 min. So bigger battery = more gas in the tank to run your motor. There are other ways to calculate this as well. I hope this makes sense and helps a bit. Where you can get into trouble is if you have a motor that pulls a higher amp draw than the battery is designed to deliver. Pull 30 amps on a GP2200 battery and it will be no problem. This cell is designed for high amp draw applications. But pull 30 amps on a 2300 mah AA cell that is designed for digital cameras etc. and that cell will be toast. Last edited by kwilliby; Oct 17, 2005 at 12:02 AM.
 Oct 17, 2005, 12:15 AM CamLight Systems Another way to do it... Assume 20A motor load. 1700mAH cell = 1.7AH cell (1.7 ampere-hours) / (20 amperes) = .085 hours (0.085 hours) * 60 = 5.1 minutes 3000mAH cell = 3.0AH cell (3.0 ampere-hours) / (20 amperes) = 0.15 hours (0.15) hours * 60 = 9 minutes Notice that when you divide ampere-hours by hours that you're left with hours, i.e., your run time. Just convert the run time to whatever units you need (hours, minutes, seconds, etc.).
Oct 17, 2005, 02:43 AM
Registered User
Quote:
 Originally Posted by kwilliby Here is one way to look at it. Someone please correct me if I'm wrong. A battery's capacity is rated in mah or milliamp hours. A 1700 mah battery is rated to deliver 1700 mah (or 1.7 amps) per minute for one hour. So this battery will deliver 102,000 mah (or 102amps) in one hour. 1700 mah x 60 minutes = 102,000 mah.
Your conclusions are spot-on, but just one correction A 1700mAh battery is rated to deliver 1700mA (or 1.7 amps) for one hour: Not mah per minute for one hour

Once you get the units right, it all begins to make sense: 1700mAh (or 1.7Ah) divided by 20A leaves you with time (Ah/A = hours).
Oct 17, 2005, 10:07 AM
Registered User
Quote:
 Originally Posted by abenn Your conclusions are spot-on, but just one correction A 1700mAh battery is rated to deliver 1700mA (or 1.7 amps) for one hour: Not mah per minute for one hour Once you get the units right, it all begins to make sense: 1700mAh (or 1.7Ah) divided by 20A leaves you with time (Ah/A = hours).
thanks for the correction. guess i was up too late.
Oct 17, 2005, 10:26 AM
Registered User
Quote:
 Originally Posted by kwilliby thanks for the correction. guess i was up too late.
No problem Now you're up too early, aren't you?
Oct 17, 2005, 10:47 AM
Registered User
Quote:
 Originally Posted by abenn No problem Now you're up too early, aren't you?
no kidding. need to find more sleeping time. just can't get everything done. i understand the battery mah stuff, just don't do a good job of transfering it from my brain to words.

thanks again.
 Oct 17, 2005, 10:55 AM Registered User I know this may seem backwards but it is easier for me to calculate the motor amp draw per minute then divide battery capacity by the per minute draw. 20 amp draw / 60 min. = 333 mah per min. 1700 mah battery / 333 = 5.1 min. just another way to look at it i guess.