Arduino powered lead acid battery desulfator

Other Hardware General Electronics
1

So I started exploring the route or fixing an old lead acid batteries. I seem to have a number of them laying around :slight_smile:

The most complete article i can find http://homepower.com/view/?file=HP77_pg84_Couper partially describes the circuit design. Main article page ( http://homepower.com/article/?file=HP77_pg84_Couper ) In this instance the circuit is using a 555 timer but that would be replaces with an arduino and would also include battery monitoring etc.

I have a couple questions regarding the schematic, as I am looking to distill this down ...

  1. what is the purpose of L2?
  • it sounds like a resistor? or maybe a surge suppressor?
  1. what is the purpose of C4?
  • the collapsing field in L1 would induce a flyback voltage, wouldnt C4 slow down this change? or does it work to increase the current through L1?
2

I am sceptical about the claims made for that system - the stuff about the resonant frequency of the battery sound like snake oil to me - but I am no expert on lead-acid batteries.

C4 provides the return path for the current pulse that is injected into the battery, and L2 prevents C4 from absorbing the pulse itself. The idea seems to be to draw power from the battery at a steady rate (hence the L2-C4 decoupling circuit) and release it back to the battery in pulses.

[EDIT: if you want to redesign the circuit around an Arduino, I'd design it around an N-channel logic level mosfet, which means inverting the sense of the mosfet/L1/L2/C4 combo. The reason they used a P-channel mosfet is that the 555 produces negative-going pulses.]

3

I have a PIC-powered desulphator, built as a kit from Courtestown Marine. Works good and does indeed rescue sulphated batteries (but not ones in which the plates have warped). This design was from the desulphator forum (now linked from the Courtestown web site) and when I started with the design I had the source for the PIC. Somewhere I lost it. Courtestown then fell out with the designer and they lost it as well, but had a copy of the hex file so could continue producing them (I think that they have stopped that product now). Obviously they also blew the security fuses... So if anyone can find the source that is a good starting point. Porting to Arduino then a short step....

4

nick_theboatman:
So if anyone can find the source that is a good starting point. Porting to Arduino then a short step....

From reading through Couper's article it seems as if the 555 side of the circuit switches the FET on at 1 kHz for 50 us. Should be close to trivial to program this. I guess the battery monitoring can be done every couple of seconds/minutes by switching of the conditioning circuit to protect the ADC from inductive spikes.

Also noticed this erratum for the article: http://alton-moore.net/graphics/desulfator.pdf

5

I was under the assumption that high voltage broke down the sulphation build up... I've seen 120/240 capacitor fed supplies

The resonate frequency sounds made up, if I was going to build my own I think I'd try something in between like a 12v to /120/240v store it in a cap then discharge it across the dead battery, a small transformer or inductor not sure maybe I should build one see if it works!