c 60 xantrek with bts chargeing at 15.4 volts

solarsquirral · February 2015

hi guys
im chargeing 4 large 6 volt rolls surritee s 550 12 volt system
ive set the charge controller at 15volts per rolls recommendation
since installing a bts the charge voltage is 15.4

temp outside here is 70 degrees during day 40 at night
does this sound right??/
should i adjust the charge controller??

thanks for any info

BB. · February 2015

What is the battery bank actual temperature--If in basement/ground contact, the batteries may be cooler than 70F. If the battery box is in full sun during the day, they maybe higher (and batteries have pretty good thermal mass, so the average temperature may average low or higher depending on your setup).

The Rolls sometimes really like the higher voltages for charging (solar is time limited by sun--Too low of charging voltage can chronically undercharge your battery bank and limit its life/early sulfation)... I would start checking Specific Gravity and water usage with your present settings... If SG looks OK and water usage is not bad (say cells need water every ~2 months)--You most likely are doing OK.

-Bill

solarsquirral · February 2015

thanks for the reply bb
my batterys are in box i made from old refridgerator truck panels
five inch thick insulation elevated off the ground with venting
ive even gone so far as the wrap the bank with fiberglass insulation batts

the temps here can be anywhere from 0 degress in winter to 90+ in summer

water usage is very little maybe a few ounces every three month( 20-30%cycleing)

specific gravity in all cells is 1.265

BB. · February 2015

Few ounces per cell or for all batteries total?

Others with similar batteries will hopefully comment on water usage--Of course, this is during winter when you do not have a lot of sun/charging opportunities.

-Bill

solarsquirral · February 2015

few ounces total

got down to 32 degrees last night
checked it today and it was bulk chargeing at 15.6
then droped to 14.8 at float floated for a three hours
sun was going down and it dropped to 13.7

kinda worried about the high bulk and float charge seems like 15.6 would be practically an equalize charge

think im doing damage ???

westbranch · February 2015

Do you have a laser thermometer? If so take a temp reading on each cell for info and use the average temp to manually calculate and see just how much correction the CC will apply ....

SG gives you the best indication of how your charge parameters are working. Water usage should go up in summer....

BB. · February 2015

A few ounces total in a largish battery bank over a couple months--That is not a lot of water. It does not sound like your bank is being "over charged" at this time.

Rolls and Surrette's are known for "liking" higher charging voltages. Some have gone as high as ~16 volts (12 volt bank) for weeks/months of solar charging to get batteries to perform well.

What model of battery do you have--There may be differences in charging voltage between models (industrial/traction batteries seem to need higher charging voltage for Absorb--Especially with solar/wind power systems where you do not have utility power for 8-12 hours per day).

-Bill

solarsquirral · February 2015

thanks for the reply
the model is rolls s-550
this system is off grid so no utility power(backup genset)hardly used

i use a little more water in summer ,
i have an pro fill water system ,
i normally do an equalize charge every month or two and top off with water

good to know people have been known to charge at 16 volts cause that seem to be what my cc is doing

i dont have laser temp guage might be worth a thought

thanks guys

solarsquirral · February 2015

another weird thing was the meter says the array volts and its been all over the place
bettween 40 vdc and 5 vdc in the sun i have noticed it was higher when the battery was behing brought back up to bulk and lower while in float
is this cause the battery is full and the cc was lowering the voltage???

still havent figured this out cause i know these are 12 volt panel each wired induvidually into the combiner

stumped???

BB. · February 2015

If everything is working well--The Vmp-array for a PWM or MPPT controller should never fall below Battery Voltage (or Vbatt+1 to 2 volts).

The array voltage, with sun on it, should never fall to 5 volts.

40 Volts for a Voc~21 volt array--You could get inductive kickback--But it sounds a bit strange (DMM meters "sample" the voltage, so it is possible for a meter to "phase" on the data and give you some very strange results. Search on "Nyquist Theorem" if you want more information.

So--We are left with two or three possibilities...

1. You have a bad DMM... Go measure the votlage of your car's battery. Tap the leads fast and slow (0v/12v) etc... and see if the meter responds the way you think it should (assuming you are using a DMM you can move around with). Measure other voltages (like 120 VAC from your wall outlet). Check/change the meter battery.

We have a few times gone around bad electronic meters that seem to almost make sense.

2. Your system is really doing what you measure. If so, the high voltage would usually indicate two panels wire in series (somewhere) in the system. Disconnect one of the Vpanel wires (pull fuse/open breaker/etc.). Se what Voc really is. If you have several sets of panels, you can disconnect one set of panels at time and see what each one Voc is reading. Generally, they should all be very close (i.e., 21v, 22v, 20v, etc.). If you see one string with 40 volts--there is an issue.

And if your array really does read 5 volts at time--That sounds like a poor electrical connection somewhere--Or possibly a short (bad insulation, cut from sharp sheet metal, etc.).

3. The meter is "aliasing" against the PWM frequency... With PWM, the Vpanel-array will be something like 15 volts when the PWM is on, and 21 volts when PWM is off... If the meter is sampling against the PWM controller's frequency... The meter could be reading all peaks (21 volts), all valleys (15 volts) or slowly walk from 15 to 22 volts as the sampling frequency walks against the PWM frequency.

I don't remember if this the C60's meter, or a hand held DMM... But I would change the battery in the DMM if has been a few years since you last put a new battery in. For sanity's sake.

I am not sure what else it can be... If the panels and controller/battery system is wired correctly, and you have the right connections (i.e., measuring from +/- leads on the Panel Bus, and not from earth ground/green wire/sheet metal to + as an example)--I really have no explanation why you see 40 and 5 volts on the Array +/- , it just does not make a lot of sense.

-Bill

solarsquirral · February 2015

thanks for the update
still waiting for a dc clamp meter to come in the mail
all these reading are from my xantrex meter that i plugged into the c60 controller

so strange cause the first day i plugged it in everything was reading like normal 19 volts at array
checked the next day after running some large loads was reading 36-40volts at array battery was reading normal charge rate 15.5 at bulk hmmmm
checked the next day and was getting a 5 volt at array reading while bulk chargeing at 15.5 hmmmmm

the watt reading was higher while rechargeing
then as battery was fully charged the watt reading went down to 40 watts which was about the watts i was using at the time radio some led lights
im guessing this is because i couldnt put anymore into the bank

quite perplexed

Vic · February 2015

Hi solarsquirrl,

Yes, you need some additional ways to measure what your batteries are being exposed to;

Good Voltmeter
Good Hydrometer
a thermometer to measure battery or electrolyte temperature

You have mentioned that all cells read 1.265 SG. This is exactly what they should be when fully charged, at a nominal electrolyte temp of 25 C.

Having these four batteries use only "a few ounces every three months is very surprising to me, if these batteries are cycled much at all, and they are actually being fully recharged.

In my experience, Surrettes do NOT require abnormally high Absorb voltages -- although one member here needed high Vabs while the batteries were getting cycled-in. From that moment forward, one Advisor, here, adopted the idea that ALL Surrettes really did need this -- mine sure do not. Today am running in the center of the range recommended by Surrette -- 2.41 Vpc (about 14.47 V on a 12 V bank).

My opinions, FWIW. This is a bit frustrating for all involved ... you are our eyes and ears. Good Luck, Vic

BB. · February 2015

One other suggestion... Check your meter wiring/connections... Tug on the connections and see if the meter readings jump. It may be that simple.

-Bill

solarsquirral · February 2015

no loose connections
i called sneider tech support and they said it was fine for the c60 to handle up to 55vdc even while charging a 12 volt bank

i know the benifits of upgrade to a mppt but it seems this is working fine for me

folks on this forum told me this wasnt possible but the guys at scnieder said otherwise

c 60 xantrek with bts chargeing at 15.4 volts

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