I have the absorb voltage set at 14.4 but when checking the logs graph today it showed 14.5v for hours. Is there a reason the two don't match? I'm not trying to split hairs but I'm wondering why the two numbers don't match. If it matters I have the voltage offset set at +.1v. I haven't been paying attention to this so I'm not sure if it's always off or just today but I'll check it again tomorrow.
Oh and one other thing. A few times now I've noticed that when I shut off the battery breaker the voltage on the classic will read higher than the actual voltage for several seconds before the charge controller shuts off. In the beginning I believe the Classic display would go blank as soon as I flipped the breaker. Now I've seen the display stay on for several seconds and the last time it happened the voltage read 17v after I flipped the breaker off and there was a message on the screen about the battery voltage being too high. I don't remember the exact wording of the message. After a few seconds the Classic shuts off. Should I be concerned about this strange behavior? I've seen it at least 3 times now.
The voltage jumping up when you shut off the battery breaker is this happening with the controller running and pv input going to it? If so it will shoot up on the battery side before the Classic shuts off. The proper sequence to shut down a MPPT controller is PV input first and then Battery breaker.
On the 14.4 versus 14.5 is the battery temperature sensor plugged in? Could it be the Classic is compensating for the temperature of the batterys.
Ryan
No, no worries about seeing a high voltage when turning off the battery breaker when the Classic has been
putting out current. If it went much higher than 17V it would have shut off right away though.
Going from low impedance load (battery) to high impedance (no battery) by turning the breaker off
is too fast for it to respond. The Classic's battery side capacitor is charged up to that 17 volts and
the Classic will have to discharge it to bring the voltage back down again.
It is not a problem.
As for the battery voltage being 0.1 volt high, that is not a problem either but I would expect
it to be maybe 0.1 volt on the low side rather than on the high side. Voltage offset should
not affect what you see on the Classic's LCD for voltage reading.
Do you have a battery temperature sensor hooked up ?? If so, that is most likely the reason
for the 0.1 volt higher reading. Since the Absorb and Float voltage regulation kind of goes
up and down slightly, you may have just gotten "lucky" and logging may have just caught it
at 0.1 high during those 5 minute capture intervals.
boB
Sorry, I should have mentioned that I deactivated the temperature compensation because I don't have the manufacturers suggested charging information for the batteries. They are DieHard Platinum agm batteries which I think are made by Odyssey but Sears doesn't provide any charging information so I'm just trying to play it safe for now and keep voltages on the low side. I've read that the 100ah batteries are made by Odyssey but not sure about the 68ah batteries. But if being off by .1v is no big deal then I'm not worried about it. If anything I'll just reduce the charge voltage down to 14.3 and then if goes over by a little I'm still safe. Of course the DieHard Platinum charger when on the agm setting is charging at 14.7 according to my dad and his charger so I'm probably playing it really safe. As a side not the log was showing .1v high on all of the 5 minute readings that I saw as I was scrolling across the graph
Not sure if there was pv current coming in every time when I was shutting off the breaker and seeing the voltage increase but I think it was the last time it happened. From now on I'll be sure to shut off the pv breaker first.
Thank you for the information.
try page 6 of the manual,
http://odysseybatteries.com/files/US-ODY-OM-009_0611.pdf
they say between 14.1v and 14.7v which is quite a span. i would go right in the middle at 14.4v, but the 14.3v you've selected would be good too by their specs.
curious as to why you bought these over concorde or deka?
Thanks niel. As to why I chose these batteries the answer is because they were given me so it was an easy choice. :) My dad has been "collecting" these DieHard agm's for years and he decided to give me 2 of the small ones. These 2 have been pretty much sitting idle for about 3.5 years so I hope they are still in good condition. My dad always kept them charged so that's good. He has 6 of the 100ah batteries and then he just went out and bought 2 more of the 68ah's to replace the 2 he gave me. I think the reason he chose them is because it's easier to get your hands on a DieHard battery than the other brands based on how many Sears stores there are. Plus these are considered marine batteries and he used to be into boating. If he was buying them for solar things may have been different. Now that he's hooked up an inverter to his house I think he would like to do solar but he has way too many trees.
After seeing that 12.84v is what a 100% charged battery should read I do agree with you that's it's time to turn the temperature compensation back on. The batteries are sitting at about 55 degrees F. I wanted to see what the manufacturer said about tcomp. before doing anything but since it doesn't mention anything I'll just start out on the low and and see how it goes.
I just read in the manual that for cyclic applications the charge current must be a minimum of 40% of the 10 hr rating of the battery to get the full design life out of the batteries. I have 2 batteries so that means it wants 50 amps of charge current for both batteries in parallel. On a good day at high noon I'm putting out 18-19 amps. I guess it's time to disconnect the batteries and charge them one at a time and even then I'm coming up short. I guess now I know why my dad's charger which is made for these batteries defaults to 40 amps when he charges his 100amp hour batteries(92ah at 10hr rate). These babies want a lot of juice!
wxboy,
i guess you can't argue with free. ;)
i wouldn't worry too much about the heavy current requirement as concorde says similar things and my sunxtenders have done just fine without mega-amps going into them. agm batteries are more efficient too so they should do well to charge at your 18-19a.
i can't say what condition the batteries are in as that would depend on to what extent and how often your dad charged them.
at 55 degrees i would say you need some temp compensation. this is not something you can easily determine on your own and you don't want to compensate too much. my sunxtenders are at 4mv. if the 4mv is low it will not harm anything as you have a large span for your absorb charge and will most likely stay within specs at 4mv if you go straight for the middle at 14.4v for absorb. for the reason the batteries are cold i would not leave the absorb setting at 14.3v as cold batteries tend to want a bit higher on the voltage.