Tuesday, October 29, 2013

Re: [Electric Boats] Battery Charging Basics - homebrew chargers

 


 
hard to get into trouble with a trickle charger.



On Tuesday, October 29, 2013 11:41 AM, oak <oak_box@yahoo.com> wrote:
 

I hope this will be both fun and educational....

I'm trying to build a small, home brew battery charger.   From what I see, it sounds like the primary difference between FLA, AGM, and Li batteries (from a CHARGING) perspective is the charging profile - notably, the voltage level of the charge.

Granted, if you're trying to do a FAST charge with lots of amps, there are a lot more details to worry about.   But given the limits of readily available parts, I'm looking at 1-2 amps charging current - so I think I can simplify things a LOT.

It sounds like building a "constant current supply", attaching it to the battery (at 1-2 amps), and monitor the battery till the battery voltage comes up to the prescribed level, then disconnecting the current source.

According to the Battery University (http://batteryuniversity.com/learn/article/charging_the_lead_acid_battery), it looks like I can use a constant current source for the primary charging (stage 1), then maybe connect to a regulated power supply for the topping charge (stage 2), and then use a small microcontroller (Arduino) to monitor the voltage over the next few days / months, and occasionally turn on the "float charge" voltage for a couple of hours.  (stage 3)

Does this sound reasonable?

For charging Lithium batteries, is there any difference, other than paying a LOT of attention to the voltage levels for the peak charge level? 

From the BatteryUniversity.com site, it sounds like charging Li batteries to 4.1V per cell, and stopping there will extend the life of the battery bank, and provide a bit more guardband to avoid problems.

Thoughts?

Thanks!
John



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