Back up controller?

[alyaz]

Okay I know this is a loaded question, kinda like asking what oil is best to use in my vehicle... 

Anyway, the neighbours have a midnite controller down and we are wondering, if it may be a good idea to have a backup controller that they and we have as a spare/at the ready should this happen again in the future.  Their arrays and our arrays are basically:

the largest array on one controller would be six 250 watt panels in two strings, 
the other arrays on one controller are four 250 watt panels in two strings.

So, question is ... are there any pwm controllers you guys think are pretty bullet proof that would be a worthwhile investment in having as a spare should a controller go down?  Or is it best to try and find a 150 lite or kid as a backup?  My thinking here is that a pwm is cheaper and sufficient for use while a classic is being repaired?

Thanks.

[Westbranch]

Unless the panel Vmp and the battery bank align, ie 12,24 or 48 volts you will have to go MPPT...  otherwise, with PWM,  you may not even be able to charge your bank...   or alternatively you will lose a lot of the PV output as the PWM can not send it to the battery... ssay they put out 40 volts into a24V bank the amount over the ~ 35V needed to charge is lost, that is the MPPT benefit especially important when using Grid tie PV panels... ie not 12, or 24V compatible pvs...

[Vic]

Hi Al,

Here,  have switched the two main systems from using the venerable OB MX-60 CC to two Classics on each system.   Have retained the MXes,  still mounted on the power wall,  and still wired for immediate use.   Most folks probably do not have this option.

Regarding Backup CCs,  you  will have few alternatives for the PV strings that can have String Vocs near or above 150 VDC,  without the prospect of needing to rewire those PVs for a lower voltage,  or just avoiding the use of the high voltage arrays.

On the PWM CC question,  PWM CCs operate just like an electronic switch.  When the switch if on,  the PVs are connected directly to the battery.   This means that there will be a large reduction in PV power production,  for PV arrays with higher string voltages,  and will cause a lot of heating in the PWM FET switches.  Also,  almost all PWM CCs have absolute maximum voltage limits  that could be too low for the PV strings that run on the Classic 150s.

So,  IMO,  PWM  CCs are happiest with PV String voltages only a few volts above the highest battery voltage (when temperature compensated) that will be seen.

My opinions,   FWIW.   Vic

[alyaz]

Copy guys.  Thanks!

"Here,  have switched the two main systems from using the venerable OB MX-60 CC to two Classics on each system.   Have retained the MXes,  still mounted on the power wall,  and still wired for immediate use.”

Wow, nice.  Sounds perfect!

[russ_drinkwater]

If you want a cheapy backup reg then there are units coming out out of taiwan which incorporate reg, charger for
probably $300 US $ or less. I will be getting one as a spare at some stage. Plug and play.
From what I have been told they are reliable and do the job without problems.

[TomW]

Or snag a relatively inexpensive refurbished Classic with full warranty over here:

http://kb1uas.com/mnsforum/index.php?topic=3164.msg25695;topicseen#new

Tom

[CDN-VT]

http://kb1uas.com/mnsforum/index.php?topic=3164.0;topicseen

YUP , hurry up B4 I du

VT