Updating battery bank: should I get 2 more Crown 6CRP525's ???

Hi,

I will be updating my battery bank at the cabin since I will be adding a refrigerator/freezer which I did not have previously.

My system consists of 6 Kyocera KD185-GX LPU panels and an outback FM-80 charge controller with RTS sensor and Flexnet DC/Mate combo running a 12 volt battery bank.

I purchased 2 Crown 6CRP525 batteries (not installed yet) thinking they would be sufficiant for my loads, but I'm starting to wonder if I should buy 2 more.

Here is my dilemma:
I go to this cabin for week-ends only and spend 1-2 weeks on winter vacation (snow) and another 1-2 weeks in the summer. The refrigerator/freezer specs tell me consumption will be between 30 and 50 amps per day and if I calculate all my daily loads I come up to a total of about 1260 watts daily (kids watching TV, etc..)

If I lived there all the time, there is no doubt I would pick up 2 more Crown 6CRP525's but since I'm only there sporadically, I'm wondering if it would be worth it or not.

One more thing: In the winter, I only heat the basement at the cabin and the location where the fridge/freezer will be gets as cold as 20 degrees (F) but no less. My thinking is that while I'm away, the fridge will NOT consume much energy, as the temperature inside the cabin wil be roughly what it is in the fridge (or a bit less). So when I am at the cabin, I can make sure that no snow is on my panels and my system "should" be able to charge my batteries adequately and while I'm away there are no loads to worry about except for the couple of hours it will take for the cabin to cool down (thus "shutting off" fridge load). There are no other loads except the fridge when I leave.

So, what are your thoughts on this, should I buy 2 other batteries and pretty much be certain things will be ok or I could pull it off with only 2 batteries?

I must say I believe that my system is a bit big for such a small battery bank, but my location is not very sunny compared to Arizona!! My mentality is one of "do it once and do it right" (at least this is what I try to do...)

Any help is greatly appreciated!

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Let's see what you could expect.

    Six 185 Watt panels = 1110 Watt array = 71 Amps on a 12 Volt system.

    Crown 6CRP525 batteries are 395 Amp hours @ the 20 hour rate, so you have 18% peak charge rate - more than is needed even with reasonably large load allowance.

    But if you double them up you have 790 Amp hours and 9% peak charge rate - just under what you want (10% which the tall case batteries really want).

    If I were you I'd pick different batteries to optimize the charging. Four 6CRP435 for example. At 350 Amp hours they'd match up with the available charge current and the difference in available power is only 45 Amp hours (270 Watt hours @ 50% DOD).

    Of course I'd also make it a 24 Volt system instead, and use an FM60 rather than an FM80.

    And when you leave, don't leave the refrigerator on. It will consume around 1.2 kW hours daily itself, so if the 1260 estimate is without that you're looking at 2.4 kW hours. This is about what I use and on 232 Amp hours @ 24 Volts. Used to have only 700 Watts of panel, but I expanded that to start charging earlier in the day.
  • Mountain Don
    Mountain Don Solar Expert Posts: 494 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    I only heat the basement at the cabin and the location where the fridge/freezer will be gets as cold as 20 degrees (F) but no less. My thinking is that while I'm away, the fridge will NOT consume much energy,

    Not an expert on this, but I do know that standard refrigerators can have operational issues when placed in a space that is severely under the normal household room temperature. For one thing they may not run enough to actually keep food in the freezer frozen. There are other issues too, but like I stated, I am not an expert. I would do some more research on that before I'd spend the money knowing that it will be operating in temperatures outside the design envelope.

    I also know that there are special "garage refrigerators " that are made to run properly in cooler spaces. However, some of those cheat by using small heaters someplace. Not good for off grid.

    Check before leaping.
    Northern NM, 624 watts PV, The Kid CC, GC-2 batteries @ 24 VDC, Outback VFX3524M
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Hi Cariboocoot,
    The batteries are allready bought and the 1260 daily watts is INCLUDING the fridge. As I mentionned before, my main concerns are for winter when snow could cover my panels while I'm away, BUT I also believe that my only load when I leave (the fridge) will not operate (or very little) since the temperature inside the cabin in the winter when I'm away is roughly what it will be inside the fridge.
    Should I get 2 more of the 6CRP525's or not, in your opinion?
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Hi Mountain Don,

    I was planning on emptying the freezer part in the winter because, as you mentionned, it will thaw because the fridge part won't start as often. The adjustment in the "freezer" part is 95% of the time just a lever that changes the proportion of cold air going to the freezer itself. The true temperature sensor is in the refrigerator part. I don't plan on leaving too much "valuable" stuff in the fridge, so I guess I'll have to try it out and experiment on the first winter!
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Don't buy more batteries.

    395 Amp hours @ 25% DOD is 98.75 * 12 Volts = 1185 Watt hours. Therefor with the panels capable of 70 Amps you should have more than enough to supply 1260 Watt hours AC (conversion losses and inverter consumption included). But when those go dead it would be good to switch up to slightly more capacity.

    Pity about being stuck at 12 Volts. But I would suggest you program a current limit in to the FM80 so that the batteries aren't subject to such a high peak current potential. Really 50 Amps would be plenty. Really you could disconnect two of those panels.

    And I still think you should shut it down when not in use.
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    What would being in 24 volts change? Everything in the cabin works on 12 volts DC (Shurflo 9300, fridge and lighting) I use a 300 watt Morningstar Suresine 300 for the tv and receiver. I know that the Shurflo and fridge could be run on 24v with no mods, but I would need to change my inverter and lights.

    Apart from my wiring becoming twice as efficient, what advantage would going to 24v have?

    Am I not better off just buying the other 2 batteries instead of having all that spare charging capacity, so at least I can have a real good reserve?

    Is there any way I could put that spare capacity to good use, even if it ran a 100 watt heater in the basement or something? I want to make full use of the system, since it's there.

    So many questions!

    Oh yeah; I would also be pulling twice LESS amps, which I guess is where you're going with this, right?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Well with most of your loads at 12 VDC there's no reason to go to 24 VDC.

    But now about that refrigerator: 99% of them will not run off a 300 Watt inverter (someone has just found an inverter-refrigerator that will. Hurrah!) So I assume you are looking at a 12 Volt unit?

    Wherein we go back to the expense of buying 12 VDC equipment vs. the expense of using all 120 VAC stuff if you've got to have an inverter for any one item and the greater efficiency (lower current per Watt) of 24 Volts vs. 12 Volts.

    If two batteries can handle your power needs then stay with two batteries. But an 18% peak current rate is rather extreme and somewhat unhealthy for them. At that level quite a bit of the power (assuming all to charging) will be doing nothing more than heating the batteries, and batteries don't like heat. Deeper DOD + more heat on charging = shorter battery life.

    Coming up with an opportunity load to make use of 'surplus' PV power is something many off-gridders find themselves doing. I turn on the water pump and septic pump, run power tools or the vacuum - all manually. Making it automatic adds complexity to the system.

    Is there any reason to run a 100 Watt heater (i.e. light bulb) in the basement? No sense using power to do something unnecessary.
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Yes, the refrigerator is a 12v/24v DC unit.

    I would like to run a 100 watt heater in the basement so I could save (a bit!) on propane, as this is my main heating source in the basement. I keep the basement at 45 degrees (F) or 7 degrees (C). I have had no issues with humidity so I see no need to heat it more than that. I just need to prevent frost. Humidity is at 50% in the basement in winter which is good.

    I'll be working on a solar air heater to further reduce propane costs, but that's another story for another thread!

    Is running a (very) small heater possible with the excess capacity? Even if it's just when the sun is shining this would be GREAT!!
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    It's possible. You need not only a thermostat but also some method of preventing it from running when the power isn't available. In this case a relay on the FM80's AUX terminals to only allow power when in Float or possibly Absorb. Since neither of those two states can happen in darkness it should limit operation to daylight hours and relatively charged battery state. It will not prevent high current during Bulk however.
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Do you suggest I limit bulk charging at 50 amps? Even this seems high I think. I've read between C/8 and C/12 of 20A/H rating, is that correct? C/8 would be 49 amps.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???
    Do you suggest I limit bulk charging at 50 amps? Even this seems high I think. I've read between C/8 and C/12 of 20A/H rating, is that correct? C/8 would be 49 amps.

    49-50 Amps is about 12.5% or around C/8. It should be fine as a maximum. One Amp doesn't make much difference: 20 Amps does!
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Lol! Thanks, I knew that 1 amp wasn't going to fry the batteries, I said it more as "is C/8 too high to go" but I'll program the FM-80 to limit bulk at 50 amps. Please feel free to recommend me some other settings such as absorbtion and float settings, etc...
    Your advice is appreciated!
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Fortunately Crown batteries do not need high Voltage settings, so you can start with the default values and check the SG and see how they go. You probably will have to make some adjustments, especially for Absorb time.
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    I was going to set absorb time at 3 hours, does this seem reasonable?
    Other settings would be:
    Bulk charge: 2.46v/cell (14.76v)
    Absorbtion: 2.36v/cell (14.16v)
    Float charge: 2.26v/cell (13.56v)

    Also, shouldn't the RTS (remote temp sensor) tone back "abusive" settings if lets say a wrong setting was made, as it would send this info to the FM-80 signaling an anomaly, am I correct?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???
    I was going to set absorb time at 3 hours, does this seem reasonable?
    Other settings would be:
    Bulk charge: 2.46v/cell (14.76v)
    Absorbtion: 2.36v/cell (14.16v)
    Float charge: 2.26v/cell (13.56v)

    If you look at the FM manual you'll see there's no Bulk Voltage, only one for Absorb and one for Float. This is normal for RE systems. Absorb is usually 14.4 and Float can be 13.5 without any problem.

    Starting out with an Absorb time max of 3 hours is good. Watch the current and see how long it takes to 'plateau' and at what level. Those are keys to Absorb time max and End Amps. You may have to adjust this a bit as you use them to get settings which work best with "average" operations. Remote temperature sensor is a very good idea too (adjusts Voltage reading according to battery temp).

    That and the ever-important SG readings to make sure the numbers are working out right!
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Note: (I edited my last post and added info)

    About the RTS (which I have), is it correct to think it would prevent any abusive setting from damaging the batteries, and if so, why not just leave the settings at factory and let the RTS/FM-80 "do their thing"?

    Also, concerning the max 50A (limited) bulk charge, if my panels are giving me the max (limited) 50A, and I'm simultaneously using 20A (vacuum or whatever), will my shunt/Flexnet DC understand that it would be possible to charge the batteries at 50A AND offload the excess 20A to the vacuum or whatever I'm using at this specific time? (Will it bypass the "max 50amp" setting in this situation to use the full 70A my system can give.)
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???
    (Will it bypass the "max 50amp" setting in this situation to use the full 70A my system can give.)

    I cannot say for sure about the Outback, but the Midnite Solar CCs that accept input from the WhizBangJr. definitely do that. It is one of the many advantages of using a shunt. Another big one is to be able to set the End Amps for Absorb based on the actual battery bank charging current only.
    SMA SB 3000, old BP panels.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???
    Note: (I edited my last post and added info)

    About the RTS (which I have), is it correct to think it would prevent any abusive setting from damaging the batteries, and if so, why not just leave the settings at factory and let the RTS/FM-80 "do their thing"?

    No. The RTS has a limited adjustment range and no idea what the 'correct' Voltage should be. Basically it varies the settings from a baseline temperature (25C if I recall) value.
    Also, concerning the max 50A (limited) bulk charge, if my panels are giving me the max (limited) 50A, and I'm simultaneously using 20A (vacuum or whatever), will my shunt/Flexnet DC understand that it would be possible to charge the batteries at 50A AND offload the excess 20A to the vacuum or whatever I'm using at this specific time? (Will it bypass the "max 50amp" setting in this situation to use the full 70A my system can give.)

    You have the FNDC? That has a different bunch of programming available to co-ordinate its three shunts. You can also wire it in different ways, but usually it measures current out of the charge controller on one, current to the battery on another, and current to the inverter on the third. As such it can 'understand' the difference between current produced by the panels and what is actually going to the batteries.

    You'll have to read the manual carefully on that one: no one I know 'in real life' has one so I've had no opportunity to explore its possibilities. In theory it should be able to allow maximum charge controller output when loads require but restrict current to the battery to prevent it from exceeding maximum (it would do this by communicating with the controller and 'reprogramming on the fly' so to speak).
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    I was under the assumption that the whole setup of FM-80/Flexnet DC/Shunt/RTS would take the "guessing" out of the equation, meaning that they would all interact together and give the most efficient charging conditions in any situation, am I correct?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???
    I was under the assumption that the whole setup of FM-80/Flexnet DC/Shunt/RTS would take the "guessing" out of the equation, meaning that they would all interact together and give the most efficient charging conditions in any situation, am I correct?

    It certainly should.
    But it all has to be wired and programmed correctly.
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    What about limiting the bulk at 50A, considering I have the FNDC/Shunt, etc,.. Still better to limit it or the system will do it?

    I'm sorry but the Outback manuals are not very clear on what has priority on what, component-wise.....This is why I'm a bit confused! I bought this equipment so that any guesswork would be eliminated and to be able to use the system to its full potential, I just find it bizzare that I should have to tell it exactly what to do other than specify what A/H my battery bank is. I mean, that's IS what the add-ons were designed for, no? (AT LEAST the FM-80 can automatically detect what voltage your battery bank is, HOO-RAH!!)

    I would understand all the programming involved if I was only using an FM-80, but with the other components such as RTS, FNDC and SHUNT it just seems redundant. Maybe I'm misunderstanding their use.
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???
    What about limiting the bulk at 50A, considering I have the FNDC/Shunt, etc,.. Still better to limit it or the system will do it?

    With the FNDC you should be able to limit the current via its programming rather than the FM80's. The difference being if you limit the FM80 then the 50 Amps is its maximum output no matter where the current goes (loads and/or charging) whereas the FNDC should allow all the current the FM80 can supply (if needed) but limit the amount going to the batteries to 50 Amps. In other words you could have 70 Amps from the controller with 50 Amps to the batteries and 20 Amps to other DC loads.
    I'm sorry but the Outback manuals are not very clear on what has priority on what, component-wise.....This is why I'm a bit confused! I bought this equipment so that any guesswork would be eliminated and to be able to use the system to its full potential, I just find it bizzare that I should have to tell it exactly what to do other than specify what A/H my battery bank is. I mean, that's IS what the add-ons were designed for, no? (AT LEAST the FM-80 can automatically detect what voltage your battery bank is, HOO-RAH!!)

    The problem is the flexible applications of Outback equipment. There are many ways to wire up multiple inverters, for example. And lots of programming involved. When you gain complexity you lose clarity. It can detect system Voltage easily, but can't know Amp hour capacity or battery type or manufacturer's charging specifications. It just can't.
    I would understand all the programming involved if I was only using an FM-80, but with the other components such as RTS, FNDC and SHUNT it just seems redundant. Maybe I'm misunderstanding their use.

    Well the RTS adjusts Voltage values for the FM80. The shunts are part of the FNDC, which basically looks at what's going across them and logs info and such. The communications have to be active between the FNDC and the FM80, as well as any other OB components you have. This may require a HUB and MATE(1,2,3) to co-ordinate everything.

    Maybe you'd like to list all of the components you've got in your signature line?
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    As requested, I listed all of my components in my signature. Good idea, thanks!
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    Cariboocoot,
    I was wondering if my peak charge rate would somewhat be affected by the fact that I live in the Montreal, Quebec area.
    I don't know if that is what you factored in on your first post (where you calculated 18%). I believe that where I live the number could possibly be closer to 19.2% BUT I may be totally wrong, so please correct me if so.

    Let's say I'm right, and that my peak charge really could be 19.2%, could I then think about adding 2 more of the 6CRP525's ?
    Now would be the time to do so, as I've yet to use them in the system.

    What do you think?
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    No, unlike with everything else in Canada Quebec doesn't get a special deal on sunshine. :D

    There are geographic aspects which will increase or decrease maximum PV output. Being up a mountain will increase it. Being somewhere with less-than-clear air will decrease it. Cold temperatures will increase Voltage, hot temperatures will decrease Voltage. The temperature issue has a significant effect on array configuration up here where -40 happens!

    This is not the same as location effect on total Watt hour production, which varies according to not only peak/average output but also hours of equivalent good sun. This is why my array runs 82% efficient and can produce over 4 kW hours in Summer, but is only capable of maintenance once Winter shortens up the days (10 hour time difference).
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???
    As requested, I listed all of my components in my signature. Good idea, thanks!


    Who picked out that equipment? Let's say I would have done it differently for what the needs appear to be. The FNDC and MATE 2 add up to enough to buy a Classic 150 with WhizBang Jr which would eliminate them and the FM80 and be simpler to set up and use. Too late now.
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    The equipment was picked by me. It's a first kit and I started to buy it over a couple of years until it was complete for installation. The FM-80 was one of the first things I bought so I continued to work with that. I tried my best to plan the system with expansion in mind so that it would be easier to adapt it for changing needs if that was the case.

    I only go to the cabin on the week-end now, but one day I would like to live there full time and with 2 young children our energy needs will probably go up some over the years.

    This way, if the need for more power arises, I figure I'll just have to swap out my battery bank for (4) 6CRP435's as you suggested and be able to use the system's full potential.

    Meanwhile, the system should perform very well on cloudier days since it's much more than what my ACTUAL needs are.

    I'm not much of a "redo everything" kind of guy, I like to try to combine present and future needs and achieve something that can give me many years of service with (hopefully!) no headaches.
  • creeky
    creeky Banned Posts: 31
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???
    the fridge/freezer will be gets as cold as 20 degrees (F)

    Just wanted to check that you meant 20F. That's 12 degrees below freezing if I still remember my Fahrenheit correctly.
    Well. you won't have to empty your freezer anyway.

    My in-home fridge/freezer combo says in the manual "do not run below 50F." I think you might want to check the operating range on your fridge.

    I also have noted, using a kill-a-watt, that my winter draw on the fridge averages 500 watts per day. In the summer, it peaks at around 1kw a day.

    Just for reference. I have had six of those batteries in 3 12v strings for over 4 years now and still running fine.

    Hope this helps. Cheers.
  • inetdog
    inetdog Solar Expert Posts: 3,123 ✭✭✭✭
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???
    creeky wrote: »
    My in-home fridge/freezer combo says in the manual "do not run below 50F." I think you might want to check the operating range on your fridge.
    I assume that you (and the manual) are talking about the ambient air temperature outside the unit.
    With some designs there could be problems with refrigerant load, freezing up of components, etc. An absorption type fridge might not work in very cold temperatures since the heater could not reach a high enough temperature to boil the ammonia out of the water mixture.
    SMA SB 3000, old BP panels.
  • Mr.Cockburn
    Mr.Cockburn Solar Expert Posts: 34
    Re: Updating battery bank: should I get 2 more Crown 6CRP525's ???

    I believe manufacturers put these disclaimers because they know the units will operate erratically in colder temperatures due to the fact that the sensor is located in the "fridge" part. The freezer part usually has no sensor, but has an adjustment that simply changes the ratio of cold air going to either the fridge or freezer. The reason is not that the unit CAN'T operate in lower temps (in my case, "lower" meaning 22 (F) or -5.5 (C)) but it logically will mean that the fridge part won't need to start as often (or at all), thus potentially thawing-out the food in the freezer part if exterior temperatures are slightly below what the temp inside the fridge should be, but not cold enough for the freezer part, such as in my particular case.

    I don't think it will be a problem for the compressor, again, in my particular case, but I will empty the FREEZER part in the winter to make sure nothing thaws out. I don't really want to unplug the unit because the reason we bought a fridge in the first place is to stop having to bring a cooler with us every week-end, which we have been doing for the last 8 years, so that option is getting pretty old!

    The unit in question is not an absorbtion-type.