help sussing out batteries and charging times

[cnc_machinist_andy]

simple enough for most people. until i grasp fundamentals i go round in circles.
suppose 18v brushed electric drill motor.
how many amps does it need or draw ? wording may not be correct.
what about battery - lipos.... say 1x 3000aH 30c or 2x 3000ah 15c in parallel ?
or 6000aH 30 c?
what about recharge times of my examples above ?
sorry guys but i cant make sense of what i need to buy.

[maddox10]

First, avoid parallel charging for any kind of battery.

mAh, not Ah. 3000Ah is a VERY big battery

Drill motors are in most cases hot wound, meaning that they can draw more than enough amperes to melt anything inside them. That is a good reason to follow the FRA rule and install a fuse that is rated at the burst current of the battery. In your examples, and depending on brand/type of batteries it can go from 120A for the 3000mAh 30C (40C burst current) to 360A for the 6000mAh (60C)


Recharge times. Actualy, it's more the question of what your charger can do. But for the 3000mAh 15C or 30C batteries it's a safe bet it's a C1 max charge. Meaning you can set your balancing charger to 3A.
For the higher end batteries, with a higher C rating, you can think about C2 or even C5 charge cycles. But for the 6000mAh that would mean a 12 to 30A charge.

Time from almost flat to balanced depends also on the quality of the charger.
To 80% on a C1 rate will take about 45 minutes. Full balanced can take up to 90 minutes with a normal charger.
A charger that can handle C5 will charge to 80% in 10 minutes and full in 30 minutes.


What you need to buy. Depends on your application.
To give examples. Team RCC feather Hannibalito 3 drives on 4S 3000mAh 30C. Valkiri3 used 6S 3700mAh 65C.
Perun, our 6kg machine uses a 3S 4000mAh 30C, and can be used for 2 or even 3 full fights. Nebelwerfer 2, another 6 kg sucked a 3S 5000mah 30C dry in 1 fight.

Our heavy Bullfrog can do the job, on the edge, with 10S 5000mAh 35C.

[cnc_machinist_andy]

thanks maddox... yes i realise now its mAh....

thanks for helping me out with examples. the lipos in parallel would only be installed in the bot for upping the C rating
obviously not charged in parallel.

plenty of helpful info from you, many thanks.

[maddox10]

Paralleling batteries upps the mAh stored. The C rate doesn't change actually.

2x3000mAh 30C batteries in parallel will give you 6000mah 30C.

The amount of cells (the S value) will change the voltage. Putting those in series will add the cells together.
Standard LiPo's are 3.7V nominal per cell.
Mixing 2 different S packs isn't the best idea. But sometimes done to boost the voltage for a low power application.
For example, using a 4S main pack with a 2 or 3S smaller "booster" pack to power a 24V solenoid.

[cnc_machinist_andy]

ahh yes thats the one.
i knew series upped the voltage. got muddled up with parallel amps and c rate
cheers