[RE-wrenches] Low output

bob at midnitesolar.com bob at midnitesolar.com
Wed Jun 20 12:08:52 EDT 2018 

All great questions.  Sounds like the battery voltage is below set-point 
(29V) using the heat gun

which is the thing to do to drag its V down.  The Kid should have gone 
back to MPPT (Bulk, Float or EQ) in a few moments

after doing that.

The sanity check for tracking is to note the Voc (105V), which you 
did...  Then note the PV input voltage

while the CC is in MPPT mode.  The input voltage should be somewhere 
between around 75% to 83%

of that Voc.  If it is higher than that (87V for 105V Voc)  then the CC 
is trying to reduce its output current

for some reason...  Either it thinks the battery voltage is above 
set-point voltage (battery temperature compensation?),

or is current limiting  (not in your case)...  OR, maybe the Kid is over 
temperature and is throttling back its output ?

You swapped in another Kid so that is probably not it.

If the input voltage is below the set-point voltage, (less than a out 77 
volts), then that is an indication of either

a shaded panel (not the issue it would seem) or maybe a bad panel or 
high resistance connection or something else.

If the PV input voltage is where it should be (between around 80 volts), 
then the array is putting out as much as it can

in the present conditions.  So if that is the case, or the PV voltage is 
below max power point (< ~77V), then I

would check for bad connections or current limiting from the PV array by 
short circuiting the PV array and measuring

the current with a clamp on meter or whatever you have.  Make sure to 
turn off or disconnect one of the PV wires

from the Kid input when doing that.  If you measure much lower than you 
expect for that array then you've more

than likely got a bad connection in the array or wiring down on the 
ground in the BOS box or PV breaker maybe.

Keep us posted.

Thanks,

boB Gudgel





On 6/20/2018 7:54 AM, Tump wrote:
> Are your batteries fully charged? FLA batts?, check w/ a refractometer 
> or set the Kid to EQ. T
> Also check/cycle the combiner box breakers to off then on as they are 
> center trip breakers and putting the cover on sometimes can trip them. 
> Also while in the combiner box check for individual polarity and V/I. T
>> On Jun 20, 2018, at 8:06 AM, glenn.burt at glbcc.com 
>> <mailto:glenn.burt at glbcc.com> wrote:
>>
>> Have you got another manufacturer's cc you could swap in temporarily?
>>
>> Do you have a load on the batteries?
>>
>> Sent from my 'smart' phone so please excuse spelling and typos.
>>
>> ------ Original message------
>> *From: *frenergy
>> *Date: *Wed, Jun 20, 2018 12:51 AM
>> *To: *re-wrenches at lists.re-wrenches.org 
>> <mailto:re-wrenches at lists.re-wrenches.org>;
>> *Cc: *
>> *Subject:*[RE-wrenches] Low output
>>
>> Off-gridders,
>>
>>               Small 24 volt off-grid install.....new installation, 3, 285
>> watt PVs in series, 4, L-16's in series, Midnight "Kid" CC.  Problem: I
>> cannot get more than about 200 watts (8-9 amps battery side) out of the
>> Kid display in full noon sun, clean PVs. Should be 700 watts plus and
>> about 28 amps.  Bulk/Absorb set at 29V, battery voltage at ~25 V (pulled
>> down with a heat gun).  I changed that Kid out for another new one> Same
>> issue!  I disconnected the PV wires where they land in the Kid and got
>> 9.3 amps short circuit, 105 volts oc  Called Midnight tech support but
>> we couldn't come up with a good solution.  Ideas?
>>
>> Thx,
>>
>> Bill
>>
>> Feather River Solar Electric
>> Bill Battagin, Owner
>> 4291 Nelson St.
>> Taylorsville, CA95983 530.284.7849 <tel:95983530.284.7849>
>> CA Lic 874049
>> www.frenergy.net <http://www.frenergy.net/>
>>
>>
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