Classic Battery Monitor

[Tons001]

Thanks Vic.

[boB]

We have had a couple overcast days. My Trimetric is showing -80 cumulative amp hours total out of the bank. It is sunny today and I thought the Classic would have stayed in bulk longer than it did. I adjusted for a longer absorb in hopes to replace as many amps as possible but I doubt I will make it. My batteries ask for a 2 hour absorb which I have extended to 5 hours and set my end amps to 4. If I kept it at a 2 hour absorb, I would end up in float with a rather large amp hour deficit still in my back ... at least according to the Trimetric.

So my question is two part. First ... I am assuming the Whizbang Jr is the answer to fixing this because the Classic would then know exactly how much to replace? Second ... is there anything in the immediate I can do dump more current into the battery bank or was increasing the absorb time my best bet?

Or I guess a third question is am I complete idiot? 

Question on the Trimetric's accumulation of NET amp-hours...  How often does that reset ?

I would think that to keep a battery charged, that the amp-hours into the battery would just keep on
going up and up and up and so would have to be reset at least once in a while so that you're not
constantly looking at amp-hours gone by from a week or more ago.

It has been a while since I've used a Trimetric.

boB

[TomW]

boB;

How will this work with dual Classics, E-Panels and stacked Inverters like I have?

Both E-Panels have a shunt in the DC bus. Mine has a shunt in each negative line so it only sees the current in its' respective charging / inverter system.

Just something I wondered about.

Tom

[Tons001]

Question on the Trimetric's accumulation of NET amp-hours...  How often does that reset ?

I would think that to keep a battery charged, that the amp-hours into the battery would just keep on
going up and up and up and so would have to be reset at least once in a while so that you're not
constantly looking at amp-hours gone by from a week or more ago.

It has been a while since I've used a Trimetric.

boB
[/quote]

I have the trimetric set to reset when the voltage is above 28.3 for more than an hour AND the end amps is below 6. The classic is currently set to absorb at 28.6 for four hours with an end amp of 4. I am accounting for a known 2amp constant load on the battery. Even though the trimetric is set to auto reset when the charged values have been met, it never resets the cumulative amp hours but it will reset the days from charged to 0.

With no way to measure SG, I waited until the Classic hit and stayed in float for two days in a row then manual reset the Trimetric's net amp hours to zero. I also disconnected loads, waited a few hours and matched up the resting voltage of the bank and classic measured with a multimeter. The AH of my bank is programmed into the Trimetric.

My question is less about the Trimetric and more about whether the Whizbang Jr will have more active control of charging the bank. I know the Trimetric is just a monitoring tool to help gauge SOC but with AGM batteries it is really the only tool besides resting voltage. If I ever redo this, I'd probably go with FLA batteries to avoid the guessing game.

[Vic]

My question is less about the Trimetric and more about whether the Whizbang Jr will have more active control of charging the bank.

Tons ..,

As I read it,  at first release the WhizBang Jr.  WILL have the ability to terminate Absorption from the Classic,  based on an EA setting.  This EA setting will be the ACTUAL charge current into the battery bank,  not just based on  the Classic's output current.  So,  the WB Jr.  will have a control function based on the current INTO the battery bank.

It appears that the WB Jr.  is just over the horizon,  IMHO,    Reality may differ.    Vic

[zoneblue]

The diff betw the trimetric and the classic  is that the trimetric knows the true net balance into or out of the battery. The trimetric however doesnt know what the actual load is, or what the charge is, cant dinstinguish them apart.  OTOH the classic without WB Jr knows what the output is, but also, not what the loads are, or what the charge current is. So neither solution alone works. Using both combined and a bit of maths does however give  you the full picture. The other way around that is with the pentametric and multiple shunts.

The classic with WB Jr, will know the charge rate from its internal shunt, plus the net current into or out of the battery, via the WB jr, and hence by subtraction, it will also know the true charge rate, and the loads. Bring it on baby.

[Tons001]

Okay ... so after thinking about it for a week and researching online which this forum & NAWS is great for, I believe my issue is not enough panel for the size of my battery bank. I simply do not think I was dumping enough current into the bank. Luckily I have not yet bought inverter so rewiring from 24v to 12v was a 30 minute job. According to the Midnite sizing calculator, I should now be dumping 37.5 amps into the 12v/305ah bank vs. the 18 amps that was going into the previous 24v/305ah bank. Now to see how warm the Classic gets with the same size array but 12v bank......

Am I thinking about this correctly? I am relatively sure I was deficit charging. Luckily it was only for a couple weeks.

I want to eventually get back to the 24v system but I will have to add more panel.

[zoneblue]

I believe my issue is not enough panel for the size of my battery bank. I simply do not think I was dumping enough current into the bank. Luckily I have not yet bought inverter so rewiring from 24v to 12v was a 30 minute job....I am relatively sure I was deficit charging.

How did you arrive at that?  If by 'not enough panel', you mean not enough volts then reducing bank to 12 volts will help, but reconfiguring array would be better. However, if you mean not enough amps, what is the Wp of the PV compared to Ah of bank? Are you sure you arent inventing problems? What was your orig OP issue again? Reducing batt voltage doesnt sound like a step in the right direction.

[Tons001]

Currently have 540wp from the array and it was going to a bank of four 6v/305ah batteries. I live in a suburb of Chicago so my lot is only 1/4 acre and I can only fit so many panels. The max current I ever saw going to the batteries was 18a and when you subtract out the constant 2a load ... the batteries were getting 16a peak or 5.5% charge rate. I took two of the 6v batteries out which according to the Midnite string calculator will give me a peak of 37.5a minus the now 3a constant load should be 34 or so amps going to 305ah bank or 11% charge rate.

Or is my thinking wrong?

Everyday I watched the cumulative ah on the Trimetric get further and further away from 0 even when the Classic reached float. My only conclusion was that I am dumping enough current into my battery bank during the bulk stage. 

[Tons001]

I also currently don't have an inverter/charger so I was using a Mastervolt converter to go from 24v->12v to power the 12v equipment I currently have.

I also oversized my wiring when I did the install so 12v doesn't concern me at the moment. Array to the Classic via 4awg. Classic to bank via 4awg. Batteries currently using 4/0awg.

[Tons001]

See attached.

[zoneblue]

Edited mistakes:
Your panels: http://www.enfsolar.com/pv/panel-datasheet/Monocrystalline/90
Vp=18V, Ip=5.4A That would give you:

Code Select Expand


Ip Vp inStr nStr Vp Ip Wp
------------------------------------------------
5.4 18 6 1 108 5.4 583
5.4 18 2 3 36 16.2 583
5.4 18 3 2 54 10.8 583
5.4 18 1 6 18 32.4 583


54V is about right for 24v. You need about 2 times nominal. Available charge current is 583W/27v=21 amps, into 300 Ah is a tad low, but for agms will probably work. Your basic problem is not enough pv. Youre also barely giving the classic anything to do, so you had better turn it off at night, the tare losses will bite hard.

[Tons001]

You are dead on. I was uploading the pdfs when you were responding. The array was always in two parallel strings of three. I can't currently add panel so dropping the system voltage since I have yet to purchase an inverter seemed like the best option.

[Tons001]

And should have typed "battery voltage" not "System voltage".

[zoneblue]

Its not the battery voltage you need to reduce its the battery Wh.

You might have imcreased the controller output amps, but you just split that in half again to charge the cells in parellel, yeah?