[RE-wrenches] 24V Rolls Charging Parameters?

[Bob-O Schultze]

Wayne,
In the first place, 4 parallel strings of anything is a very bad idea. Micro resistances in cabling and connections plus eddy currents and the like will, over time, inherently unbalance the pack. Doing frequent EQ charges will be required but will not overcome the inherently bad design of too many parallel strings. If you want to stay with Surrette, one string of 24  2-YS-31PS will give you about the same capacity in one tasty, electrically happy string. Lots more money, I get that, but that would be the ideal situation. As a fallback, do yourself a favor and spec out 12 of the 4KS-21PS so that you have just two parallel strings. Should even be a little less dough.
Jamie Surette (james at surrette.com) is  usually pretty good at returning emails and calls. His would be, without doubt, your best opinion as to a proper charge regime for his batts.
Good Luck. If you go with four strings, you'll need it.
bob-O


On Apr 29, 2013, at 2:15 PM, Wayne Irwin wrote:

Hello Wrenches,

Please provide your opinions on the proper charging voltages (e.g. bulk, float, eq,), and recommended durations.

The bank consists of 12 - Rolls 8CS25P (820AH @ 20hr rate) (4 strings of 3). Design based partly on budget limitations.

FYI. The system is off grid and consists of an 8KW array, 2 - OB VFX 3524 Inv's. and 5 - OB MX80 CC's.

I have general parameters programmed based on AH's but would like to have additional opinions/suggestions to compare and/or see if there is something that I have missed.

I have not yet received any feedback from Rolls tech support ..... James?

Thanks in advance for your help,


Wayne Irwin,
President
License #CVC56695 
State Licensed Solar Contractor
Pure Energy Solar International Inc. 
Wayne at PureEnergySolar.com 
http://PureEnergySolar.com 
352 377-6527 Office
352 336-3299 Fax


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