If i made a battery pack of 13 batteries, each 3.7V 4000mAh in series, then i would get a battery pack output of 48.1V 4000mAh (assuming thats correct).my question is, how would i go about charging the pack? or bertter put, what kind of charger should i be looking for to safley charge the pack?im clueless on how to go about charging it, any advice would help, thanks.
Charging specifics depend on the chemistry of the battery. There are different approaches for lead-acid, NiCd, NiMH, LI-Ion
The charger will be related to the types of batteries. There are specific charges designed to work with individual battery types. The poor man's way of charging is to get a power supply that is capable of producing 60Vdc at at least 5A so you can dial in the voltage to what the batteries will take.
If you can add a balancing connector, that would be perfect. You would basically be able to charge each cell individually. (Note that all Li-Ion / Li-Po battery packs have this). I'm not familiar with this battery chemistry, but i suspect it charges in a similar manner to Li-Ion. Apply a constant current to the battery pack, while not allowing any cell to exceed 4.2V, until whole pack has 54.6V. Then apply a constant voltage of 4.2V to each cell until current decreases to your preset value. (you can adjust this . lower level higher capacity, higher level longer service life). Be careful as Lithium batteries can explode when overcharged.
I'm not sure either. A thermal cutoff is a good idea for lithium ion cells stops (or greatly reduces) the charging when the cells heat to 40 degrees c 104 f or there abouts. Tesla motor car has a separate fuse for each of the 8000 cells. A piece of fine wire about 1 centimeter long in series with each cell may be an adequate fuse. One fuse, 10 amp slow blow is likely ok as all your cells are in series. Likely 5 amps of charging current is ok up to 80% of full charge or when the first cell has a voltage of 5 volts, while charging. A fan to keep the cells cool will be helpful at high charging rates. A resistor that increases from 1/10 ohm to one ohm, when it heats to 110 f while touching each cell, might be ok. I think, the 50 volts at 400 milliamps is ok, if you don't mind 6 hours to half charge, and you remember to stop charging at 20 hours, or sooner. Unlike nicd, lithium ion cells are ok about partial charging, but deteriate or worse if over discharged, or over charged. Neil
Make a 50V rated 400mA DC power supply to charge it for 14 hours.
