setting absorb and end amps ??

Re: setting absorb and end amps ??

Do you have the Wizbang Junior shunt kit for the Midnite charge controllers?

Anyway, the end current is going to be the point at which a battery charging at the correct absorb voltage (around 14.2 to 14.8 volts or so at ~77F and based on battery chemistry) when the falling charging current falls no more... Typically this can be 1% of the C₂₀ rate of charge... It can be as low as 0.1% for AGM/New flooded cell batteries... Or it can be as high as 2% for "old/about to fail" flooded cell fork lift type batteries.

Since you are getting reasonable S.G. readings--Let them tell you what is working. Start at 1% cutoff and see what happens. Personally, I do not like to "gas" a battery bank very much--Just enough to get some electrolyte stirring/clean out the pores on the plates, use enough water to need refilling every 2 months of so (when cycling).

And adjust/bracket the end amps as needed (less charging, go up to 1.5% cutoff. More charging, go to 0.5% end amps, etc...

From what one battery vendor said, and putting together various other rules of thumbs and practical limitations for a battery bank system--If your battery charging current never falls below 2% rate of charge--It is time to change out the bank.

On the practical side, you are losing too much energy to the failing battery bank. On the safety side, you could be looking at a cell/battery overheating and eventually catching fire.

Of cource, to measure the end amps, you either need an integrated battery shunt like the Wizbang Jr. (plus an external shunt) for the Midnite family (Outback may have their own product--I am not sure), or you need to know that you have no loads on the battery so the controller can measure "ending amps" correctly.

-Bill

Re: setting absorb and end amps ??

If you have loads--If they are steady state (say 5 amps), then you can add that to the ending amps.

But since you have a Midnite Classic 150--All you need is the Wizbang board, a shunt, and some wiring to do "accurate" end amp measurements. I believe it also gives a Battery Monitor function to the Classic controller too--Without buying a separate battery monitor.

-Bill

Re: setting absorb and end amps ??

It is a balancing game here... EA, Charging Voltage, Time, Temperature, Specific Gravity, etc...

In my humble opinion, don't try for 100% SOC everyday... >90% every few days is fine (every day is OK too). You don't want to over gas/over heat the batteries--Both are hard on the long term life.

There are other ways of doing charging too... Run ~50% to 80% SOC daily, and >90% (or ~100% if you want) every 7-10 days or so (I think it was Surrette that said you can even run a 28 Day cycle). My understanding is that as long as you are daily cycling the battery bank, they will not sulfate (or at least sulfate any faster) under normal use. Take them full every ~1 week to clean out the plates, mix the electrolyte. Do not store the batteries below ~75% SOC (sulfation). And cycling 50-80% is much more efficient charging (less gassing, less water use, cooler batteries, etc.).

Others here have their own "formula" that work well for them (Marc/Cariboocoot, likes 100% SOC charging as an end point--I think).

You read enough about lead acid batteries--And you will convince yourself they do not work for off grid solar... But they do (get the right brand/model for the job). The wrong Lead Acid batteries (non-deep cycle, some industrial duty batteries, GEL, and such), will not (usually) work well.

-Bill