trying to decode EA values for Deka solar batteries

mahendra

ok I just got my whiz bang jr. from ALte store. However as i previously stated in another thread .I have been playing around with various values to determine a suitable ending amps for my system. My absorb Amps seems to plateau to the 1% mark of the Battery bank amp hrs. But that does not seems to be a good EA value for my batteries,since they are being undercharged. The information given by Deka for their batteries is: "End Condition - Charge until change in current < 0.1A per Hr/Max Time:12hrs" .i do not grasp what they are trying to indicate from this instruction,Can someone please explain?
Modify message

stephendv

Re: trying to decode EA values for Deka solar batteries

They've giving you the slope of that "plateau" as 0.1A change in 1 hour. I.e. if you measure the amps with 1 hour spacings, then when the difference between readings is 0.1A or less then they're fully charged; and you can use the last reading as the EA.

mahendra

Re: trying to decode EA values for Deka solar batteries

Exactly how do i go about doing this?

mahendra

Re: trying to decode EA values for Deka solar batteries

Also looking back at my CC logs and recalling previous monitoring ,i don't recall seeing differences of 0.1 amps or less difference between two separate hour readings.Can i assume then that my batteries were never fully charged judging from this?

westbranch

Re: trying to decode EA values for Deka solar batteries

I suppose with very good equipment one could measure .1 Amp, but, say that is a 400Ahr battery, .1A is .0025% of the total Ahr's. Normally anything > 98% SoC is GOOD ENOUGH.... like Ivory soaps slogan goes 99.44% pure, the rest is in the water so to speak...
You are chasing a pipe dream IMHO

SolarMusher

Re: trying to decode EA values for Deka solar batteries

You will have to push three times the status button on your Classic MNGP to find the Whizbang display (assuming that you have the last firmware). On this display you will see real amps going to the batteries no matter what your loads are. When your end current will stop decrease that will be your EA value (add 1amps), you will have to set this value in the Advanced menu of your Classic. Is it what you want to know?
Erik

SolarMusher

Re: trying to decode EA values for Deka solar batteries

Eric, you're too fast

mahendra

Re: trying to decode EA values for Deka solar batteries

well yes i think , all i am trying to do is determine the Ea values for my battery banks but it has been hell to determine it.

Blackcherry04

Re: trying to decode EA values for Deka solar batteries

mahendra wrote: »

well yes i think , all i am trying to do is determine the Ea values for my battery banks but it has been hell to determine it.

Don't over think it, 1 to 2 % of Amp Hr capacity has always been the excepted value that keeps you from overcharging or undercharging your batteries. EA combined with SG readings will guide you.

stephendv

Re: trying to decode EA values for Deka solar batteries

Blackcherry04 wrote: »

Don't over think it, 1 to 2 % of Amp Hr capacity has always been the excepted value that keeps you from overcharging or undercharging your batteries. EA combined with SG readings will guide you.

I don't like this one-size fits all values, especially since we don't even know what batteries Mahendra has. They could he gel, agm or flooded, all we know is they're made by Deka.
My forklift batts are still accepting charge at 0.5% of Amp Hr capacity so if I stopped charging at 2%, they'd be chronically undercharged. The way that deka has specified the amps as a rate of change makes more sense than an absolute value, and I'd follow their method if you can't measure SG.
Any chance of providing us with a link to the technical doc where you got that info Mahendra?

Blackcherry04

Re: trying to decode EA values for Deka solar batteries

stephendv wrote: »

I don't like this one-size fits all values, especially since we don't even know what batteries Mahendra has. They could he gel, agm or flooded, all we know is they're made by Deka.
My forklift batts are still accepting charge at 0.5% of Amp Hr capacity so if I stopped charging at 2%, they'd be chronically undercharged. The way that deka has specified the amps as a rate of change makes more sense than an absolute value, and I'd follow their method if you can't measure SG.
Any chance of providing us with a link to the technical doc where you got that info Mahendra?

I can get my batteries to accept some amount amps until the melt, try it. keep on pumping it in hour after hour and see what you end up with. There is a Accepted limit as I said. No Rule fits every situation, LOADS are also a factor as is temperature and age of the Batteries and type of Battery.

mahendra

Re: trying to decode EA values for Deka solar batteries

they are AGM .Here is the link.
http://www.dekabatteries.com/assets/base/1913.pdf

stephendv

Re: trying to decode EA values for Deka solar batteries

mahendra wrote: »

they are AGM .Here is the link.
http://www.dekabatteries.com/assets/base/1913.pdf

So using their recommendation you'd just need to check that the rate of change of charging current is less than 0.1A over an hour, e.g.:
- When the current starts reaching the plateau, start taking current measurements every 20 minutes.
- Compare the most recent reading with the one taken 1 hour ago. If the difference is less than 0.1A, then the most recent reading is your EA value

stephendv

Re: trying to decode EA values for Deka solar batteries

...and you may need to take a more pragmatic approach to interpreting that 0.1A current based on the size of your batt and the accuracy of the measuring equipment. Measuring 0.1A from a 500A shunt isn't practically possible using the whizbang or any other RE battery monitory. Here's the charging current going into my batt, read from a 500A shunt:
Attachment not found.

That's an absorb which started at about 11:50, and then I started an EQ at 12:45. You can see that from about 14:30 there really wasn't any change in the current.

Here's the flat period in more detail:

Attachment not found.

During that "constant" period there are high readings of 13.2A and low readings of 12.3A; but there isn't a constant downward trend, so I'd ascribe those differences to the limits in the measuring equipment and the sample rate of one reading every 5 minutes.

If you're taking the readings manually, and you have a relatively large shunt, then perhaps it would be better to take 3 consecutive readings and log the average as the reading for that 20 minute period. (The 20 minute period is just a finger in the air to save you time, if you want to take readings every 5 or 10 minutes that'll work too)

mahendra

Re: trying to decode EA values for Deka solar batteries

thanks a lot Stephendv that helped but as you mentioned it is very difficult tom measure 0.1amp and like you i also haven't noticed that drop i should see. guess i would have to take the average time readings

Blackcherry04

Re: trying to decode EA values for Deka solar batteries

There is more than any one factor that goes into EA. When you are in absorb you are maintaining the battery at a over-voltage above nominal and pushing current into the battery at a level to maintain that Voltage and what the battery will accept. If the voltage is set to low it will not require as much current to maintain the voltage, if the voltage is set higher it will take more current. EA is a moving target, add a BTS / RTS and your chasing it. While the EA set point is fixed, getting there is anything but.

I believe you have a Deka 8G8DL Gel ?? They use a Absorb voltage of 2.35 - 2.40 vpc, I'd stay on the lower end @ 14.1 volts to start. I like my absorbs to last around 2 + hour range and a EA of 1%-2%. To achieve that I will adjust the Voltage up or down in .1 -.2 increments on the voltage limits until I can get within that time frame.

PNjunction

Re: trying to decode EA values for Deka solar batteries

mahendra wrote: »

Also looking back at my CC logs and recalling previous monitoring ,i don't recall seeing differences of 0.1 amps or less difference between two separate hour readings.Can i assume then that my batteries were never fully charged judging from this?

Correct, they are not fully charged. What this means is that once you reach the absorb voltage level, and the current starts tapering, once you get to a point that there is no further significant progress in the current tapering as measured on an hourly basis, (ie, say one hour you read 2.8a and the next hour you read 2.75a, (less than 0.1A difference) then you are fully charged. These values are just made up for example btw, but it is the difference that counts.

At this point in time, then you could consider 2.8a your EA. By relying on a <0.1A difference measured between consecutive hours, it takes into account battery aging/usage, and is more accurate than a mere percent-of-capacity calculation. The EA should be re-measured on a regular basis (yearly perhaps) as the battery ages, as the battery's internal impedance rises from use/age, and you would reset your EA in the controller accordingly.

If you don't re-measure your EA once in awhile and raise the amperage, you will remain at the absorb voltage longer than necessary as the internal impedance has risen over time, and will never reach your initial EA when you first set it up, and fall back to the 12-hour max safety override timeout you have hopefully set for absorb. So two settings really - one for EA remeasured on a regular basis, and the 12-hour max absorb timeout as a safety-fallback.

If you have a battery bank, rather than a single battery, then I'd set the bank EA to the weakest / oldest one in the group with the highest amperage measurement for EA. Thus one of the reasons not to get batteries in a bank that are too far apart in age from each other.

But is this practical from a solar standpoint? You may not have enough solar insolation to stay in absorb long enough to get to the "true" EA. And is it even necessary to be absolutely 100% charged? Perhaps not. I would however do this at least in the beginning with the aid of a charger once in awhile, not only to ensure that you have actually reached 100%, but also to give you an idea of your internal impedance over time, ie, if what used to take 3 hours to reach a <0.1A difference in consecutive hours now takes 6-8 hours or more with the aid of a charger, you know you have an internal impedance issue, or just batteries headed for the old-age home if they are not swollen or have dropped a cell already.