Suitable battery for offgrid?

[NEOH]

Well the specs show the "typical" battery life at 20% DOD at 3000 cycles but I would think that is at lab conditions. But if you are only doing an 8% DOD with those 330Ah batteries you may get a long life out of the Crown. Although 10 years may be a stretch unless you follow all of the maintenance procedures perfectly as well as perform an Equalization charge per recommended time frames.

Will Crown, or any manufacturer, ever tell us their exact Testing methodology to obtain 3,000 @ 20% DOD cycles?
1) C/4 or C/5 Discharge Amps ?
2) Using a Final Voltage or Amp-Hours to terminate the discharge test ?
3) Using a 3 Stage recharge?
4) Any periodic Equalizations?

To get 3,000 @ 20% DOD discharge - charge cycles, at a slow C/20 Rate, would take a like 4 years ???
I do not think that is happening.
So they must be discharging at a faster rate like C/4 or C/5 ?
Or are these "Cycles vs DOD" graphs just for Entertainment Purposes only?

Could they be using the BCI S-06 Cycle Test?

[SunEagle]

Will Crown, or any manufacturer, ever tell us their exact Testing methodology to obtain 3,000 @ 20% DOD cycles?
1) C/4 or C/5 Discharge Amps ?
2) Using a Final Voltage or Amp-Hours to terminate the discharge test ?
3) Using a 3 Stage recharge?
4) Any periodic Equalizations?

To get 3,000 @ 20% DOD discharge - charge cycles, at a slow C/20 Rate, would take a like 4 years ???
I do not think that is happening.
So they must be discharging at a faster rate like C/4 or C/5 ?
Or are these "Cycles vs DOD" graphs just for Entertainment Purposes only?

Could they be using the BCI S-06 Cycle Test?

I would imagine the testing procedure it probably something that is not available to the open public, but might be available to any Standardization authority.

IMO like most other industries there must be a way to use an accelerated testing procedure that simulates real time life cycles in some way to match their claim.

[NEOH]

Why do we allow the BCI, Battery Council International, to be so secretive about their BCI S-06 (Golf Cart Cycling and Repeat Reserve Capacity Cycling) Test, and their other battery test procedures? The "Cycles vs DOD" charts for many deep cycle batteries are "derived" from the BCI S-06 test. I think it would be highly informative to require the actual Amps and actual final discharge Voltage (definition of the Discharge Cycle) to be posted under the "Cycle vs DOD" graph. It is very inappropriate to disguise a "Marketing Hype" graph as a "Battery Specification'.
This issue reminds me of how the car manufacturers had previously manipulated their MPG ratings. We no longer tolerate false MPG ratings. VW has recently learned this lesson, the hard way. So, why do we continue to tolerate highly misleading "Cycles vs DOD" charts from the battery manufacturers? The BCI is the fox, guarding the hen house.
Maybe, this is a project for Consumer Reports ?

[PNjunction]

The charging instructions attached must be similar for other batteries people use in solar power system. How do you get on if there are days the array can't produce 40 amps? Say a week of rain when the batteries only charge up on say 10 amps?
Also, I guess the three phases are bulk, absorb, and float?
cheers,

Note that those instructions are for EV usage, where one typically very deeply discharges them, and has limited turn-around time (like maybe overnight at best) to put the vehicle back into service.

The 3 phases mentioned are the classic IUI protocol (current-voltage-current) for fast turnaround. Basically the first constant current stage is just the max current your charger can put out. In this case, they recommend anywhere from 40 to 100A. Once the battery reaches about 80% SOC, the "CV" constant-voltage stage is in effect, where the voltage is limited to 2.37v per cell. As the battery charges the terminal voltage rises to try and meet the charger voltage. The net result is that the *battery* is the one tapering the current, not the charger.

At this point, when current tapers off to about 15A, (or the time criteria where no further tapering occurs), ANOTHER constant current stage follows, not float.

This last stage of constant current is not voltage limited, and is an attempt to make up for the 12 hours of float one would need to TRULY charge the battery - but we don't have that kind of time in an EV (or solar!) situation.

The problem with solar controllers for daily cyclic users is that we don't have that much time available to us, as these instructions assume an ac charger. Also, no solar controller to my knowledge will do the fast-turnaround secondary constant-current finishing charge. Again, no time usually.

So this is just the very long way around to say that if you are doing cyclic duty, then the simplest answer is to just set your CV stage to 2.37v per cell, with no float (or set that to 2.37v as well). If you baby the battery in a cyclic duty situation, it will sulfate prematurely.

[John Galt 1]

Will Crown, or any manufacturer, ever tell us their exact Testing methodology to obtain 3,000 @ 20% DOD cycles?
1) C/4 or C/5 Discharge Amps ?
2) Using a Final Voltage or Amp-Hours to terminate the discharge test ?
3) Using a 3 Stage recharge?
4) Any periodic Equalizations?

To get 3,000 @ 20% DOD discharge - charge cycles, at a slow C/20 Rate, would take a like 4 years ???
I do not think that is happening.
So they must be discharging at a faster rate like C/4 or C/5 ?
Or are these "Cycles vs DOD" graphs just for Entertainment Purposes only?

Could they be using the BCI S-06 Cycle Test?

I spoke with Crown tech department. They discharge at a faster rate (I believe it was C/4) and keep the test batteries in a water bath to help keep them cool while charging. They do EQ some during testing but I don't know if they are using a 3 stage charge.

[John Galt 1]

I have been over this many times. Use your hydrometer to set the voltage. Solar is a piss poor source of power to charge batteries with. There are simply not enough hours in a day to go through any 3-Stage algorithm You want simple CC/CV charge. To make you Classic a CC/CV charger set Bulk = Absorb = Float. Use the hydrometer to find the right voltage. It is going to be from as low as 27 up to to 32 volts. Start at 30 volts

Agreed, When my Crown 6CRP525 batteries were about 6 months old I had gotten tired of fighting with super long absorb times at the Crown recommended 58.1v and gave Crown a call. Their techs kicked things around for a while and told me to try 51.5v absorb which helped but after playing with things a bit and researching what other battery manufactures were using for absorb voltage I'm now using a higher absorb voltage. If I don't the battery SG slowly falls over a few weeks until it was sometimes as low at 1.248 at the end of a 5 hr absorb and I'd fight to get them back up.

I want to see at least a 1.265 SG after a good sunny absorb session.

A good hydrometer is your friend, use it regularly. I have 3 hydrometers and prefer the HydroVolt but you must really rinse it out after each use or it will not turn smoothly.

[Jambonjoebob]

Don't get to wrapped up in charge rate and make yourself paralyzed. Following proper design guidelines takes care of most of that. Let me give you an example. lets say we want 2 Kwh per day, 24 volt battery, and shortest Winter Sun Hour day is 3 Hours.

Immediately we can find the right battery capacity without much thought AH = [Daily WH x 5] / Battery Voltage. So [2000 WH x 5] / 24 volts = 417 AH. So you go shopping for a 24 volt 400 AH battery. Sound familar? Don't even concern yourself with charge rates at this point.

Next is to find Panel Wattage. Super Easy to do. Using a MPPT Controller Panel Watts = [Daily Watt Hours x 1.5] / Sun Hours. So [2000 wh x 1.5/ / 3 h = 1000 watts. So go shopping for 1000 watts of panels.

Last we need a MPPT Charge Controller. To find the minimum size controller we need to know how much current are panels will produce at full power. Super Easy Amps = Panel Wattage / Battery Voltage. So 1000 watts / 24 volts = 40 amps

Why do you multiply by 5 to calculate the capacity?
why do you multiply by 1.5 in wattage?

[SunEagle]

Why do you multiply by 5 to calculate the capacity?
why do you multiply by 1.5 in wattage?

Sunking has not been around for a while so maybe I can answer your questions.

I believe he uses 5 to determine capacity because it allows you to use a 20% discharge amount on the battery.

The 1.5 value increases your watt hour usage based on efficiency of the system so you up-size the panel wattage to get what you need.

[Jambonjoebob]

Thanks a lot!