Charge Conrollers not staying in Absorb cycle

It sounds to me like "Absorb End Amps" is stopping your absorb. I tried that setting for a couple days on my FM80 then disabled it because my SG also dropped, IIRC.

Anawa wrote: »

Benthere, the End Amps setting was at zero (disabled?) until I set it at 10 amps yesterday. Waiting to see what happens with absorb stage today. Right now, it's in bulk.

Go advanced and set the FX's absorb time to say 3 hrs. I think there may be a glitch even though you have set the Mate / FNdc to control the charge cycle and ending amps. I had the same problem and thats how I solved it, then the Mate settings worked.

Hi Paul,

Believe that the GB battery is a Forklift battery. These usually run 1.280, or even higher SG electrolyte. These batteries often like fairly high Vabs, in the range of about 60 volts, or so.

On the Outback Forum, there have been extended discussions of some of the issues with the way that the FNDC ends Absorb. You might want to review some of these comments:

http://www.outbackpower.com/forum/viewforum.php?f=28&sid=bdc510d6162e30935c0ab11e27044257

FWIW, Vic

Your DOD is small, so your absorbs wont be long however, the key thing is that the absorb stage completes properly. You dont really want to be guessing at these settings. Take a clamp meter and taking current readings every 20 minutes through absorb. From this curve you can see what your end amps figure should be. And whether its time or amps that the controller is triggering on.

You need to temporarily set the abosrb time to 10 hours for your test cycle. If need be disable the fndc, or set EA to a very low amount. You need to find out what it triggering absorb termination. Here our bank is lightly cycled like yours at least 3 out of 4 cycles. Absorb is around 2.5 hours. For deeper discharges is might run trhough 4 or 5 hours. Its very important that you complete absorb, as each cycle that doenst complete permanently locks up hard sulphate and the batterys capacity reduces by that amount. However if you run longer float times in the afternoon, that can make up for it to a fair extent.

Are you sure the end amps is actually running off the battery current? It might be that your loads are confusing it.

Anawa wrote: »

. My last (and only) equalization was on 4/21/2015.

With Fork lift type batteries you MUST equalize every 30 days and sometimes more often. So once you get the battery fully charged...

While there is some urgency to get the SG up, just remember to factor that some L16 form factor batteries are known to take a few dozen cycles to easily reach the full target SG. Rolls is one brand known to do this in quite a stuborn way. But you do need to perserve even if it means increasing the absorb setpoint and time a bit during this break in period.

What i was trying to explain was about how a battery charges. During bulk, the battery will take all you can throw at it, and the current is limited in practice by the Imp of the PV array that day. Once the absorb setpoint is reached things change, and the controller prevents the voltage rising, As it does this the current will begin to decrease in a concave manner. This is the classic charge acceptance taper. The only blackbox image that i can readily lay my hands on is at the bottom of this page: https://code.google.com/p/theblackboxproject/

The bottom graph blue curve is the actual battery current, and while it wasnt a clear blue day, eventually you see the taper take effect around 11.30. Because the weather was a bit frumpy the controller kicked in and out of absorb for a while which you can see on the top graph red curve. Its that battery current "charge acceptance" curve that i suggest is important to get to know, for your bank. It will follow this same curve each day, albeit sometimes longer sometimes shorter depending on the initial SOC. YOur battery documentatiion shoudl state a tpyical end amps figure, if not you will have to resort to average values for the battery type. For AGM, the typical figure is 0.5% of the bank capacity. So for example i have 400 Ah bank, 0.5% of 400 is 2Aamps. In practive i add 0.5 amp to this to give the controller some margin for waveform noise and set my end amps to 2.5 amps.

Now if the battery does not absorb, but goes straight to float, the charge acceptance taper still keeps tapering, just at a slower rate owing to the lower voltage setpoint. The critical thing is that (regardless of charge stage) the taper tapers until its flat. Thats the point when the battery accepts no more current, and is the point when the battery is fully charged. The actual process of absorb always has a higher voltage for several reasons. (such as electrolyte stirring, and speeding up the charge process with limited daylight etc) But the important thing is that the bank reaches that point of accepting no more current. If not daily then a couple of times a week.

With a clamp meter or as Vic said any other semi reliable method of measuring current (if you have a mate3, you oght to be able to get similar graphs to the blackbox ones) then by clamp metering the battery positive cable, you can monitor the charge acceptance amps in real time.

Remember that If you try to EQ before the taper has near completed you run the risk of creating high currents, and temps, as mentioned above.

Hi Paul,

BTW, Radio Shack has had a $50-ish DC Clamp On ammeter, if one near you is still in business... you might call a close on to check stock, if one is close. Their Clamp meter is pretty good, but most of these need to be re-zeroed several times per minute.

AND, why not try this;
Set the Float voltage on each FM CC to your desired Vabs? Would suggest somewhat more than your 57.XX, but even that for hours and hours would make use of free PV power, unless it is cloudy. You would need to monitor progress, as the CC should stay in Float for the entire day, after the usually short or nonexistent Absorb.

Believe that this has not been mentioned, but, also make certain that you use the Remote Temp Sensor/s on each charge source. Your system should be able to share on RTS, using the Hub, or something like that device.

No harm in trying the genset, but if there is good sun, why not try Absorbing, using Float stage with the Vfloat cranked up to your desired Vabs?

You have been bombarded with many thoughts, and am sure that it can be a bit to process. FWIW, Good Luck, Vic