Battery Reconditioning, Battery Desulfation

pplwizard

I purchased a Battery Reconditioning, Battery  Desulfation system from England called Battery Extra. It is supposed to desulfate my batteries without the use of a generator or grid based voltage supply... I am fully off grid.

I have yet to install the unit and I have a question the company technical support will not give me a straight answer about.  I am hoping someone here will be able to give me an answer I can understand. 

Here goes:... 

My situation is this, their product is not waterproof and my batteries are in a shielded outdoor environment. 

My inverter and solar charge controller are inside. A set (2)  2 guage wires runs from the battery Bank (which is outside) into the energy control room.  It would be much easier to connect their product to the inverter terminals given they run directly back to the batteries.

Despite the company recommended connection procedures, which is to connect directly to the batteries {their unit has 2, 12 guage wires) what is the technical downside to doing it my way, directly to the inverter terminals? 

Given that the six footlong 2 ought wire runs from the batteries to the inverter and the batteries to the solar charger controller any wires I connect directly to the batteries are going to be at the same point that inverter wire is connected as well the fact the farthest batteries are also about 6 feet away as well so what is to prevent any damage to the inverter or the solar controller from their product if they're being connected at the same point to the batteries with a wire for five times thicker than the one they are using so whatever signals they are sending to the batteries will also be sent to the inverter. 

The company says that I should connect directly to the batteries... When I asked them my question aside from the above this is what they said :

"There are very specific safety standards  that we have to comply with to be able to offer our products for sale.  All of our models have been tested and passed the EU  EMC safety standard. So you can be assured that you will have no problem with inference with your inverter or solar controller.  We have many thousands of Battery Extra units in use around the world on solar systems."

pplwizard 

mike95490

Most of the desulfators use a high frequency "pulse" to shake the crystals off the plates.  The impedance of the long cables regardless of the thickness, will inhibit the effectiveness of the unit.  you will have to figure a way to prevent water ingress to the desulfater.

BB.

Pplwizard,

Ohboy... Desulfator. One of the few times we have had to lock a thread or two here. There are folks that believe in them, and others that hate them, and others that don't believe they do much.

Be that as it may... This the sort of the theory that I understand how they are supposed to work (may be right, may be sort of right, may be off the wall/and there may be other desulf "operational theories out there").

Basically, when a lead acid battery discharges, it creates a fluffy gray/soft lead sulfide on the plates. And, if the battery is not actively cycling (sit for hours/days/weeks/etc.), the fluffy lead sulfate converts to a hard black lead sulfate crystal which is an "insulator" and no longer participates in the charging/discharging cycle. Basically causes loss cycles, plates that don't have as much active area, and stuff that falls to the bottom of the battery (storage area at base of cell to collect debris and reduce the chances of shorting plates together).

A "desulfator" is basically a switch that turns on and off very quickly and creates an "impulse" electrical waveform. The impulse travels from the black box, down the wiring, and into the plates of the battery. An "impulse" can be thought of as a mix of many different frequencies (from low to very high frequencies).

https://en.wikipedia.org/wiki/Pulse_wave (pulse train--general solution)

These impulses are intended to "vibrate the black sulfate crystals" and cause them to back into solution and "recover" the battery capacity.

Looking at sending the impulses from the black box to the battery--You want short, low impedance, wiring to carry all of the (especially high) frequency energy to the plates/crystals.

Anything you do that increases impedance ("complex" resistance--not only pure resistance, but capacitive and inductive effects)--Tends to filter out the higher frequencies and (probably) reduce the "desulfation" effects.

You have to think of sending Radio Frequency energy on your cables... Things to do include "twisting" the +/- cabling, using stranded cable vs solid, keep wiring short and help keep the wiring impedance "low".

Remember that inductive effects (inductance of the cabling) and the capacitive effects at the termination (plates of battery look like a "capacitor" and the DC input to the inverter has lots of filter capacitors). When you have inductive wiring and capacitors between +/-, you create a low pass filter -- So, running long wiring, and running the desulfator to the AC inverter DC input, instead of to the battery/battery bus directly, you (as I understand), run the risk of reducing the amount of high(er) frequency energy to the sulfate crystals.

Other issues that we have seen--A desulfator can create quite a bit of high frequency "noise" in the system (and could even cause wiring to "resonate" like a bell). In one installation, a good quality MPPT controller had significant reduction in daily harvest energy when the desulfator was running (something like 1/3rd less--as I recall). Turned off the desulfator, the harvest went back to normal (there was a second MPPT controller that was not affected to compare with).

A (dc powered) desulfator does discharge the battery a bit (usually very slowly)--So just keep an eye on the state of charge over the long term, and probably do not use a desulfator on a battery bank that is "in storage" not being actively charged.

-Bill

clean up sentences a bit... -Bill

pplwizard

Wow! Now thats an explanation I can live with... I will connect to the batteries directly. 

Thank you.