RTS and FM60 charge controller configuration

reckless1

Good morning all,

As mentioned in a previous post i live in Kingston Jamaica where the average daily temperature is between 85-90 degrees F. I have two banks of rolls surette batteries (48vdc, 900AH) been charged by two FM60 charge controllers and 6000 watt of PV. When i spoke with rolls engineers a couple months ago they said to set the charge controllers to a MAX of 50AMPS, Absorb voltage at 57.6vdc(with RTS 58vdc), and absorb time at 6.3 hours. I recently got my two RTS sensors from outback and connected them but it affected my charge cycle in a weird way where the max voltage was 52.8vdc so the batteries never went to absorb.. i now realise that there are several setting to consider when using RTS like leaving the default WIDE setting in "Battery Temp Compensation" or setting to "Limited and adjusting voltages", END AMPS etc... can someone please guide me as to what my setup should be to make sure that on bright sunny days i charge my battery bank completely without overcharging\undercharging the bank. My battery banks normally deplete down to 65% DOD on a regular day (if it goes down to 50% the LVD disconnects the load until they charge back up).
sincerely,
Robin

BB.

Re: RTS and FM60 charge controller configuration

RL,

I setup your signature/location description--Hopefully that will help people like me who can't keep track everything among all the different posts/threads.

Please feel free to edit as needed (links should work for everyone):

http://forum.solar-electric.com/profile.php?do=editprofile
http://forum.solar-electric.com/profile.php?do=editsignature

Note that to get your signature to display--You must got to "Go Advanced" edit and below the edit window, check the "Show your signature" box (first time only--software will remember).

-Bill

Cariboocoot

Re: RTS and FM60 charge controller configuration

Well I'll start by arguing with Surrette's recommendations. If you've got 900 Amp hours of battery, why would you limit the maximum current to 50 Amps? That's going to take a long time to charge. Probably why they think Absorb time should be 6.3 hours. Sorry; no one has that much daylight. I have no faith in Surrette anymore; there have been too many problems and fairly bad response from the company.

You've got 6kW of array on a 48 Volt system. Crank it up to full current, which ought to be around 96 Amps between the two FM60's (which should be connected via HUB and MATE here I'd suggest).

Absorb Voltage ought to be 59.2. Do not worry about the changes the RTS makes to Voltage; it adjusts 'real' V to compensate for temperature.

You will need to watch the charging Amps to see where it plateaus near the end of charge. This is where you want your End Amps: it should be % of capacity (i.e. <27 Amps not including concurrent loads). You will need to divide this by the two controllers and set each. (NOTE: This is where MidNite Classics work better as the 'Follow Me' function co-ordinates multiple controllers easily.) This will also give you some estimate for maximum Absorb Time; just longer than it takes to achieve that End Amps.

The main purpose of the RTS is to adjust Voltage reading so that the charging parameters work with temperature variations. In your case it will be lowering Voltage to prevent overcharging due to higher temperatures. Whether you use the wide or limited setting will depend on performance evaluation. I suggest you get an IR thermometer to monitor battery temp while charging and try both settings to see which gives you the best performance. If the V is too high the temp will go higher. I suspect the 'wide' setting is best in your situation.

Vic

Re: RTS and FM60 charge controller configuration

reckless..,

It was my assumption, that EACH FM-60 CC was limited to 50 A, but this guess may not be the case.

Cycling your battery bank as deeply as you are, MIGHT mean that the Absorb voltage needs to be as high as 59.2. This voltage should be no higher than is necessary to recharge the battery in the average daily PV charge available, IMO.

Would leave the CCs on Wide if your Surrette batteries are Flooded types. Usually the Limits are used with Sealed batteries -- AGM or Gel.

For the Surrette flooded batteries in use here, with reasonable Absorb voltages (about 58 V), the correct EA setting on each of the two separate banks is just under 1% of actual 20 hour Capacity -- about 12 A per 1280 AH bank.

I do not know how well the FM-60s will share charge current during Absorb. They may coordinate, but that might require the FNDC/Mate-3 combination. Without this added hardware, it may be a bit of an issue getting each FM to carry its weight in Absorb, and use EA to end the Absorb stage ... I have no experience with FMs.

FWIW, Opinions, Good Luck, Vic

Cariboocoot

Re: RTS and FM60 charge controller configuration

Vic wrote: »

reckless..,

It was my assumption, that EACH FM-60 CC was limited to 50 A, but this guess may not be the case.

That would make more sense. Although with the limited PV it should not be an issue. If the combination of the two is limited to 50 total it's a big problem.

Cycling your battery bank as deeply as you are, MIGHT mean that the Absorb voltage needs to be as high as 59.2. This voltage should be no higher than is necessary to recharge the battery in the average daily PV charge available, IMO.

Absorb Voltage level remains the same regardless of DOD. Only the time changes. This is a problem with cheaper controllers that have fixed Absorb times and no End Amps function. But you must bring the batteries up to that Voltage level, even if they are only there for three minutes (so to speak) otherwise it is not being charged properly.

vtmaps

Re: RTS and FM60 charge controller configuration

Cariboocoot wrote: »

That would make more sense. Although with the limited PV it should not be an issue. If the combination of the two is limited to 50 total it's a big problem.

There is a way to limit the combined output of two Outback FM controllers... it requires the FNDC battery monitor and involves setting the "global amps" parameter.

--vtMaps

Vic

Re: RTS and FM60 charge controller configuration

Cariboocoot wrote: »

Absorb Voltage level remains the same regardless of DOD. Only the time changes. This is a problem with cheaper controllers that have fixed Absorb times and no End Amps function. But you must bring the batteries up to that Voltage level, even if they are only there for three minutes (so to speak) otherwise it is not being charged properly.

Actually, while this might be true if one is NOT expecting to FULLY recharge the battery on any given day, and also may depend upon the exact construction of the batteries. This factor is fairly small, and there many, many differing strategies in charging batteries. This reference was just based on what we see at this location, results under different situations will probably differ.

FWIW, Vic

Cariboocoot

Re: RTS and FM60 charge controller configuration

vtmaps wrote: »

There is a way to limit the combined output of two Outback FM controllers... it requires the FNDC battery monitor and involves setting the "global amps" parameter.

--vtMaps

Yes, but the FNDC is $275 so setting the FM controllers individually is the cheaper option.

If someone were starting out with this plan the cost of two FM80's plus one FNDC exceeds the cost of two Classics which can run together in harmony without external equipment. Plus you can add the WhizBang Jr shunt monitor and get even better results. But the Classics will not co-ordinate with an inverter's charger whereas the FNDC will.

Cariboocoot

Re: RTS and FM60 charge controller configuration

Vic wrote: »

Actually, while this might be true if one is NOT expecting to FULLY recharge the battery on any given day, and also may depend upon the exact construction of the batteries. This factor is fairly small, and there many, many differing strategies in charging batteries. This reference was just based on what we see at this location, results under different situations will probably differ.

FWIW, Vic

I know. A couple of us are researching FLA charging strategies right now in fact. The (short term) results have been interesting but not ready for public disclosure.

reckless1

Re: RTS and FM60 charge controller configuration

Thank you gentlemen, i will complete my signature this evening with all details. Surette had said to limit the charge current to 50 amps PER CONTROLLER as i would need about 90amps over four hours to completely recharge the batteries from a 50% DOD. Cariboocoot you are suggesting to increase the absorb setting on both flexmate 60 charge controllers to 59.2volts and set the ENDAMPS to roughly 13amps per controller (in your reply you mentioned to watch the charging amps close to the end of charge, is this close to the end of bulk charge???)... in the "Battery Temp Compensation" section should i set this to "WIDE" instead of "Limited" and what minimum and maximum voltages should i specify..

robin

Vic

Re: RTS and FM60 charge controller configuration

The FNDC, also REQUIRES the Mate-3 (as I read it), so this option seems even more expensive ...
EDIT: OOOpsss, looks like I am wrong on the need for the Mate-3, specs just says "Mate". But, still, for systems that have only FM CCs, and no OB inverters, the Mate might still add to the cost of the FNDC accessory ... dunno ...

The other major factor in noting that deeper discharges of Lead-Acid batteries requiring higher Vabs, is simply due to the solar day often being shorter than the time required for full recharge a fairly deeply discharged bank ... the old saw that Vabs needs to be set as high as needed to recharge the battery, at least every few days.

Have been trying avoiding fully recharging Flooded banks here every day -- Skip Bulk days with Classic CCs. This has resulted in one bank needing considerably more EQs and EQ time, and using more water. This bank needed a higher Vabs to fully recharge it on the non-Skip days. Have been rattling between just going for full-charge every day, and also using only one Skip day. This particular bank had been running three or four Skip days, and one full charge day ... seems not worth it for this lightly-cycled bank.

The other main bank of "identical" batteries is more deeply-cycled, and fares better with one Skip day, but, due to A/C loads, have returned this bank to fully recharge each day ... this bank also "needs" a lower Vabs when fully recharged each day.

FWIW, personal experience, that's all. YMMV. Vic

Cariboocoot

Re: RTS and FM60 charge controller configuration

reckless1 wrote: »

Thank you gentlemen, i will complete my signature this evening with all details. Surette had said to limit the charge current to 50 amps PER CONTROLLER as i would need about 90amps over four hours to completely recharge the batteries from a 50% DOD. Cariboocoot you are suggesting to increase the absorb setting on both flexmate 60 charge controllers to 59.2volts and set the ENDAMPS to roughly 13amps per controller (in your reply you mentioned to watch the charging amps close to the end of charge, is this close to the end of bulk charge???)... in the "Battery Temp Compensation" section should i set this to "WIDE" instead of "Limited" and what minimum and maximum voltages should i specify..

robin

Seriously I don't think there's a need to set a limit on the controllers with 3kW PV on each. Those batteries should be capable of handling 135 Amps total and that just is not going to come from a 6kW array.

But I would up the Absorb Voltage despite Surrette's recommendations. Check battery SOC with a hydrometer and beware of high water usage: too much water loss means the Absorb V is to high and/or Absorb time too long.

The End Amps is based on the current dropping off during Absorb. It gets to a point where it's a small percentage of the battery capacity + any load demands running (important to remember that part). 2% of 900 Amp hours is 18 Amps, 3% is 27 Amps. That would be in total. The End Amps is likely to be in that range (not knowing the load portion makes it impossible to predict in advance).

It appears the 'WIDE' on the FM series gives you the greatest variance in V per degree temperature change which is what we'd expect for flooded cells. You can't have that wide a variation on sealed batteries or they come unsealed.

Always check charging results with the hydrometer and adjust accordingly. You do not want high water usage or low SG and it may take some tweaking to get the best settings for your particular system.

reckless1

Re: RTS and FM60 charge controller configuration

Thanks Cariboocoot, used a infared thermometer this afternoon and at 1:30pm the battery housing was 96F, i upped the absorption set point to 59.2vdc (so it will stay in bulk till it reaches 59.2vdc) and i set the ENDAMPS on both charge controllers to 13 amps (26amps between the two). i also set the max charge amps back to 60amps (thats the max per controller). I also checked the stats for the last two weeks on the charge controllers and they average anywhere from between 2500-2800 watts max power per charge controller (multiply by two for total watts) so i am going to add another 800 watts of panels to the array this weekend which will allow me to generate more power sooner and later into the evening.. will continue to observe.. which hydrometer do you recomend as the little glass tube units never seem to give me a consistant reading....

robin

reckless1

Re: RTS and FM60 charge controller configuration

i also noticed that the charge controllers went into absorb at different times and one went back to bulk while the other remained in absorb, should i put both RTS sensoes on the same battery as now they are on seperate batteries (one per bank in the middle of the bank)..

robin

vtmaps

Re: RTS and FM60 charge controller configuration

reckless1 wrote: »

which hydrometer do you recommend as the little glass tube units never seem to give me a consistent reading....

No hydrometer will give a consistent reading if you don't know how to use it. They must be rinsed out with distilled water after each use. If they are not rinsed, the insides become sticky. Either small bubbles will stick to the float, or the float will stick to the sides of the main tube. Before I understood this I would just keep tapping the hydrometer until I got a reading that I liked

My favorite hydrometer is the hydrovolt, a european brand that you can buy in the US from Midnite Solar. Search this forum for "hydrovolt" to see some pictures and reviews.

--vtMaps

vtmaps

Re: RTS and FM60 charge controller configuration

reckless1 wrote: »

i also noticed that the charge controllers went into absorb at different times and one went back to bulk while the other remained in absorb, should i put both RTS sensoes on the same battery as now they are on seperate batteries (one per bank in the middle of the bank)..

That's inevitable unless the controllers have the ability to communicate and coordinate. Don't worry about it. It is difficult to get them exactly balanced. Once you reach absorb, the batteries cannot take the full potential current that your controllers can produce, so one or both controllers will provide less current... it doesn't really matter which one.

If your hydrometer says your batteries are getting charged, then everything is OK.

--vtMaps

BB.

Re: RTS and FM60 charge controller configuration

Hydrovolt:Attachment not found.

http://www.midnitesolar.com/productPhoto.php?product_ID=505&productCatName=Battery%20Accessories&productCat_ID=39&sortOrder=1&act=p

-Bill

Vic

Re: RTS and FM60 charge controller configuration

reck..,

Yes, place each RTS on the same battery in the center of the bank, right next to each other. They should be about half way down the side of the outer case.

Trying to get more than one Charge Controller to share Absorb (and EQ) stages in current at about the same time is a balancing act, and any balance that one feels that they have attained often changes as the charge progresses. Getting an FNDC may well be worth the cost if it makes this balancing act much easier for you ... believe that the FNDC allows multiple CCs to share the same stage, or at least both end Absorb at the same time.

Have recently been playing with two dissimilar CCs. And have been able to get good sharing of power delivered during Absorb, with a given load. But when doubling the load, this balance was almost impossible to attain, as each CC needed the other to maintain the Absorb charge.

More PV sounds like a good idea. Sometimes it can be good to have a Lead CC that has a larger array, and can generally maintain the Absorb charge, unless a large load demands power. This balancing act can take hours per day of monitoring, and changing settings, and more hours of watching ... if the FNDC can make this balancing of Absorb reliably automatic, it could easily be worth the added cost.

Your batteries are HOT, but realize that there is probably little that you can do about that, given your climate.

As Marc -- Cariboocoot -- mentioned, the Classic CCs from MidNite have the ability to communicate and coordinate charge stages. And, recently, all standard Classics ship with the battery charge current monitor, the WhizBang jr, included. The WBjr needs an added 500A 50 mV shunt to operate, but these Shunts are often installed in e-panels, etc. But know that you have two FMs ...

Will look forward to seeing the model number of your Surrettes, your inverter model, and other system details. Thanks. Good Luck, Vic

reckless1

Re: RTS and FM60 charge controller configuration

Thanks gentlemen for all your advice, i am learning as i go along...

sincerely,

robin

Vic

Re: RTS and FM60 charge controller configuration

Hi robin,

Thanks for the added detail in your Signature.

And, we ALL learning. Have Fun, Vic

SandyP

Re: RTS and FM60 charge controller configuration

reckless1 wrote: »

i also noticed that the charge controllers went into absorb at different times and one went back to bulk while the other remained in absorb,
robin

If you add an Outback Hub to your system I believe you can then use the MATE to set the charge controllers to coordinate the charge cycles.
On the Mate it is located in the menu : ADV/MATE/PG3/CC.
Note : I see this seems to coordinate Float charging with multiple Charge Controllers - not sure about other charging states.

The MATE manual on page 61 says :

Pressing the <CC> soft key enables charge controller
float state coordination. This means when
a charge controller finishes a bulk charge and
moves into float charge, the MATE directs any
other charge controllers into a float charge as well.

Cariboocoot

Re: RTS and FM60 charge controller configuration

SandyP wrote: »

If you add an Outback Hub to your system I believe you can then use the MATE to set the charge controllers to coordinate the charge cycles.
On the Mate it is located in the menu : ADV/MATE/PG3/CC.
Note : I see this seems to coordinate Float charging with multiple Charge Controllers - not sure about other charging states.

The MATE manual on page 61 says :

Pressing the <CC> soft key enables charge controller
float state coordination. This means when
a charge controller finishes a bulk charge and
moves into float charge, the MATE directs any
other charge controllers into a float charge as well.

Unless they've changed something the MATE will not program the charge controllers. It can poll it and read data and tell you what the settings are but they basically serve no purpose for operation of MX or FM controllers. They may co-ordinate Float but nothing else.

Keep in mind there are three different models of MATE (four if you count the marine version).

This is not nearly as good as MidNite's 'Follow Me' function.