Proposed System - 1000W - Advice Needed!

treefort · January 2014

Hello,

I bought a cabin last year and am ready to give it power! I've been researching like crazy and think I'm about to build a properly sized off grid system. I don't want to spend a fortune at this time and don't really need it yet, so I've decided 1020 watts of panels, 1000 watt inverter, and 12 volt 400AH battery bank is good for now. I will have a sundanzer freezer, a propane on-demand water heater, shurflo water pump, some led lights, and the odd auxiliary item(laptop, cell phone). Hairdryer, etc we can use a generator. In the future, I plan on buying more panels, batteries, a nice big inverter, and generator. Then I will up the battery bank size from 12V to 24 and use only AC from the inverter. Sound good?

(I've already bought a nice prosine 12V 1000W inverter so hopefully you agree)

I've attached a wiring diagram of my proposed system, and have a few questions that one of you geniuses hopefully can help me out with.

1. I think the breaker sizes and the 10awg from the panels are correct, but if someone can correct me that'd be great.

2. Also, what wire size do I use from the charge controller to the batteries to the inverter? 1020W/12V=85A. I think the Midnite Classic only supports up to 4AWG which is only good for 60A. I would need 2AWG for up to 94A.

3. I see in the Midnite Classic manual they suggest using breakers only. But I read somewhere a breaker could be tripped so you should use a disconnect and a fuse. Maybe that was old news and breakers are now ok?

4. Do I need lightning arrestors? If so, can they wait until next year?

Thanks a lot, any and all recommendations are appreciated! Oh yeah, is this how you would wire everything?

vtmaps · January 2014

Re: Proposed System - 1000W - Advice Needed!

Welcome to the forum,

I find your drawing a bit confusing... I don't know what some of the numbered items are. Are you planning to use a Midnite ePanel? They have some excellent wiring diagrams. They also include a shunt, and a bypass switch for the inverter.

It looks like you are planning two 100 ft runs of #10 from the array to the controller. I suggest that you use a combiner box at the array. It will be useful for future expansion and is a great place to put a lightning arrester (you don't want to bring lightning into your home). You should also think about future expansion when you choose a cable from the array/combiner to the charge controller... it's a pain to dig up a cable and lay a new heavier cable.

I assume that you realize that your inverter will not support the 24 volt system upgrade that you mentioned.

--vtMaps.

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

Hi vtMaps, thanks for the reply and welcome. I was actually in the middle of editing the drawing when I seen your reply. Part of the schematic comes from the Midnite Classic manual. They had those numbers on the drawing and yet didn't even reference them elsewhere in the manual that I could find.

Yes, I want to use a Midnite ePanel. I looked at their site and it seems like they have about a million different ePanels. Which ePanel do I choose? Does my inverter have to have a built in transfer switch to utilize a bypass switch? I'm not sure my inverter has a transfer switch. I bought it off eBay and the manual said it is an extra thing you can request at time of purchase.

You have convinced me to use bigger wire from the array with a combiner box. Yes, I'm aware about the inverter and using 24. I plan on selling the inverter and buying a nice 4000W inverter/charger when the time comes.

This is the disconnect/breaker box I think I will use: MNDC250. The solar panels will be fused/disconnected with the din rail breakers, and the inverter with the main disconnect switch and an inline fuse. Sound good? Just now need to know what size wire to use from the midnite classic to the batteries and inverter. The inverter's manual says to use #4 for RVs or Marine but #1 for residential. Will the Midnite Classic 150 support #1 wire? Scratch that, I just looked in the manual and the DC terminal on the Midnite Classic only supports up to #4. Am I good with #4 then? I find it weird that a 96A controller only supports #4 wire..

Thanks again

vtmaps · January 2014

Re: Proposed System - 1000W - Advice Needed!

treefort wrote: »

Yes, I want to use a Midnite ePanel. I looked at their site and it seems like they have about a million different ePanels. Which ePanel do I choose? Does my inverter have to have a built in transfer switch to utilize a bypass switch? I'm not sure my inverter has a transfer switch.

The ePanels exist because they offer a better "all-in-one" solution then the inverter manufacturers do. For example, you can buy an outback inverter as a bare inverter. Outback will also sell you that inverter as part of their "flexware" package. But most installers would choose to buy that inverter as part of an ePanel kit. The Midnite kit is more flexible and customizable than the Outback package. All breakers, bypasses, busses, circuit breakers, lightning arresters, etc are included with the ePanel, everything is sized correctly and listed for that use.

So you bring up an interesting problem: is it worthwhile to use an ePanel with a temporary system? I'm really not sure... need to think more. The beauty of the ePanel kits is that each one is engineered for a particular inverter/charger with internal transfer switches.

Something that comes up often on this forum is system expansion. Many folks are surprised and disappointed to learn how little of their system is useable when they upgrade. I think that if I were you, I'd wait on the ePanel until you know what inverter/charger you want. Design your 24 volt system. Build a battery box for your future system. Install your combiner and cable for your future system. Your Classic will migrate nicely to the new system. Try to locate your conduits and Classic i such a way that an ePanel can be added later.

One other thought... visit the Midnite forum.

--vtMaps

halfcrazy · January 2014

Re: Proposed System - 1000W - Advice Needed!

#4 is fine for 100 amps. You can use the "In Free Space" or Open Air chart not the wire in conduit chart.

You could buy an E-Panel for the Inverter you plan to use when you go 24v and use it now. You would have to do a little fiddling on the AC wiring from your inverter and the 2 battery cables but that would get you a pc of gear that would not have to be swapped. I would also suggest buying the batteries in such a form that you can re configure them for 24v from 12v when the time comes

westbranch · January 2014

Re: Proposed System - 1000W - Advice Needed!

If you plan to upgrade later ( or sooner) I would do all my calculations for voltage loss based on 12 Volts as when you go to 24v there will be less loss, so no rewiring there. The inverter should be wired based on the highest amperage you will be pulling, that is usually 2 x its output rating. So you will need to make a decision now as to your future system capacity.
hth

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

Thanks for the input everyone. I will get a combiner box and think about the future upgrade when choosing wire sizes. And, I guess I won't worry about the #4 wire not being able to handle 100A.

I've been looking at epanels..their pricing, capabilities, etc. and comparing them to the MNDC while thinking about the future. The MNDC won't even work for this 1000W install because it only holds 3 panel mount breakers. I am forced to use panel mount breakers because of the 100A breaker requirement for the Midnite Classic to the batteries(1020W/12V=85A). I would then not have room for a GFP, which is code now for everyone to have, correct?

So, I'm thinking the best choice is to go with the MNDC Plus. It holds 10 din rail breakers or 6 panel mount breakers, has a couple more bus bars, and a bit more room than the MNDC. It is only ~$220 too where the epanel is $600+. Does anyone see a problem with using the MNDC Plus after the upgrade? ie. Upping the total wattage from 1kW to 4kW.

vtmaps · January 2014

Re: Proposed System - 1000W - Advice Needed!

treefort wrote: »

Does anyone see a problem with using the MNDC Plus after the upgrade? ie. Upping the total wattage from 1kW to 4kW.

The ePanel has a bypass switch, lightning arresters, a shunt, and has all the AC busses and circuit breakers you will need for an inverter/charger with a built-in transfer switch. The ePanel comes in two sizes... get the "stretch" version for easier access and for the lightning arresters.

The door to the ePanel is very strong and is designed to hold the weight of a large inverter/charger. That can really save on wall space.

--vtMaps

couchsachraga · January 2014

Re: Proposed System - 1000W - Advice Needed!

Here is something else to think about - does it make sense to keep part of your system 12v, and only use a (smaller) inverter when necessary? My setup is strikingly similar to yours - shurflo 12v pump, propane instant hot water heater (requires 110... hence my SureSine inverter), lights (a few LEDs, but mostly compact florescent and a few incandescents (being replaced by LEDs)), and a few other random draws (amp for cell phone, ham radio and GMRS radio). I increased my system to that size as I'll be adding a SunDanzer in the summer. My system size is 1080w (4x270), all on one string, in to a MorningStar classic 200. The specs would have that slightly over max, but I checked with our local installer (who did my main residence) who ran a more detailed analysis of the run and system and found it was well within safe limits. If your panels were more powerful it would be wise to do the same if you are thinking single string. I have 4 T1275's (600aH total) for my battery bank.

I looked at the ePanel, but decided that it was easier and cheaper for me to set up my own breaker box as I was not planning on a bigger inverter (no need... the only thing we need 110 for is the ignition for the Rheem propane on demand hot water (which doesn't take much) and when we want to charge up a drill battery, or other random 110. Our current freezer fridge, plus all the lights, ceiling fans, pump, cell charger and amp, and radios are all 12v DC...and many of them more efficient for it.

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

Hi couchsachraga,

The Midnite Classic 150 is good for 96 amps, where the Midnite Classic 200 is only good for 79. I think that's what you what you are talking about but I'm not sure what you mean by single string. I was thinking two strings to keep the voltage differential between the panels and batteries closer for the sake of the controller. When I up the battery voltage to 24 or 48 I can then up the panel voltage as well. I can add more panels and keep the same wire run as before.

You're right, I don't need to upgrade the system. But at one point I would like my family to be able to use a washer & dryer, toaster, coffee pot, blender, etc. as well as not have to worry about whether or not we need to go outside and charge the batteries with the little honda and charger.

It's a hard decision. I will let you all know what I end up with.

Thanks again.

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

Quick question, can I use these AGM batteries for the solar setup? I'm mainly concerned about the connectors on the Discovery battery. They say 4A max connectors.

Edit: Rereading the max 4A sticker...it says Max 4A per 1mm² Connector Diameter Area. So I should be good, right?

Thanks!

zoneblue · January 2014

Re: Proposed System - 1000W - Advice Needed!

treefort wrote: »

Thanks for the input everyone. I will get a combiner box and think about the future upgrade when choosing wire sizes. And, I guess I won't worry about the #4 wire not being able to handle 100A.

I understand where you are coming from, but theres mitigating factors: shortness of that cable, and the system doesnt often run at peak amps. Your calc (1020W/12V=85A), is optimistic. Rule of thumb controller/pv derating around here is 0.77 (eg see Bill, http://forum.solar-electric.com/showthread.php?22265-Testing-Panels-maybe-a-bad-panel&p=179904#post179904), so thats down to 65A. Then once your batterys are charged, if youve done your design right, then the current drops quickly back to a dribble.

I've been looking at epanels..their pricing, capabilities, etc. and comparing them to the MNDC while thinking about the future. The MNDC won't even work for this 1000W install because it only holds 3 panel mount breakers. I am forced to use panel mount breakers because of the 100A breaker requirement for the Midnite Classic to the batteries(1020W/12V=85A). I would then not have room for a GFP, which is code now for everyone to have, correct?

If you want to use GFP then midnite classic has one built in. However if youre off grid, and your PV is under a 125V, then i think the general advice is not to use GFP. You can search this forum for an extensive discussion on this, (actually its here: http://midniteforum.com/index.php?topic=142.0).

So, I'm thinking the best choice is to go with the MNDC Plus. It holds 10 din rail breakers or 6 panel mount breakers, has a couple more bus bars, and a bit more room than the MNDC. It is only ~$220 too where the epanel is $600+. Does anyone see a problem with using the MNDC Plus after the upgrade? ie. Upping the total wattage from 1kW to 4kW.

Hmm. Can you maybe get away with a big baby boxe setp for now? If you really plan on getting an Outback or similar inverter, having the right epanel as others have said is useful, and anything you do now is wasted. The problem you have is the 12/1kw inverter will need a bigger breaker. Maybe the real problem here is the 12v inverter. All the numbers become happy when you go up a voltage. 24v/1kw, is like a 60 amp inverter breaker, 80 amp controller breaker. Single baby box and youre done.

1kw is about right on the boundary for 12v systems. However if you are ultimately moving to 4kWp, then your headed to 48V system. So going 24v now is also going to be changed again too. Looks like you are going to have to bite the bullet and design build (and sell one) two seperate systems.

So that brings us back to what you have, the 12v inverter. That will need a breaker in the realm of 125A. (To be correct it would be
1kW / 85% eff / drop out voltage of 11v * 1.25 comfort factor =135A, but the next size up from there is 175A). And that puts you into carling, and rules out baby box/quad box. MNDC then, they are neat little cabinets, and well priced.

vtmaps · January 2014

Re: Proposed System - 1000W - Advice Needed!

treefort wrote: »

Quick question, can I use these AGM batteries for the solar setup?

Are you planning to put two different brands of battery in parallel? It's usually not a good idea to mix batteries of different ages and brands.

Also its not a good idea to have more than two or three batteries in parallel, even if they start out identical. AGM batteries, because of their very low internal resistance, are even more susceptible than flooded batteries to being unbalanced by the resistance in all the extra wires and connections that you will have in a parallel battery bank.

If you have four AGM batteries in parallel you should get a DC clamp ammeter and check that the four batteries are getting equal charging current.

--vtMaps

zoneblue · January 2014

Re: Proposed System - 1000W - Advice Needed!

treefort wrote: »

Quick question, can I use these AGM batteries for the solar setup? I'm mainly concerned about the connectors on the Discovery battery. They say 4A max connectors.

Edit: Rereading the max 4A sticker...it says Max 4A per 1mm² Connector Diameter Area. So I should be good, right?

Thanks!

Well the main question to be asking there is: will the batterys provide the 125 amp plus that the inverter needs? Im doubting it. They look small, and they look old. They appear to be AGM which are known for low internal resistance, so if they have some life in them... maybe... but youll need to parallel them and thats not going to be ideal.

You are discovering that batterys are now the crux of solar designs?

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

The batteries are the size of a typical car battery. They've actually never been used and have been sitting for maybe a year. I just checked their voltage and they're all dead

Too dead for my canadian tire smart charger to even detect. I just read that if you stick them in parallel with a good battery then the voltage from it will trick the charger into charging the dead AGMs. So, I'll try that then see if they still hold their charge. Obviously from what you guys are telling me, they're not ideal, but hopefully they're good enough for now..you guys are probably cringing..

Ok, so a 125A breaker/disconnect for the inverter. And a 100A breaker for the charger?

4v/1kw, is like a 60 amp inverter breaker, 80 amp controller breaker.

Zoneblue, why would the controller need a bigger breaker than the inverter if going 24V? Wouldn't they both need a 60A? (1020W/24V=42.5A)

Thanks, you guys are awesome.

Oh yeah, Midnite claims that GFP is required on all PV systems, but if you say a general rule of thumb is GFP is not required for anything under 125V , I won't worry about it. Thanks!

BB. · January 2014

Re: Proposed System - 1000W - Advice Needed!

treefort wrote: »

The batteries are the size of a typical car battery. They've actually never been used and have been sitting for maybe a year. I just checked their voltage and they're all dead Too dead for my canadian tire smart charger to even detect. I just read that if you stick them in parallel with a good battery then the voltage from it will trick the charger into charging the dead AGMs. So, I'll try that then see if they still hold their charge. Obviously from what you guys are telling me, they're not ideal, but hopefully they're good enough for now..you guys are probably cringing..

Trying to recover "dead batteries"--Likelihood is that they are not going to store a useful amount of energy--And worst case, they may be a fire hazard (shorted cell, electrolyze water into hydrogen+oxygen and/or vent gases around battery compartment while charging, etc.). Not something that you would like to leave unattended in your home/cabin (and old batteries that have gone bad are a risk that I would not do in a home/cabin/vehicle--Maybe on as a bench top experiment withing nothing flammable/I care about near by... Maybe...).

Ok, so a 125A breaker/disconnect for the inverter. And a 100A breaker for the charger?

Zoneblue, why would the controller need a bigger breaker than the inverter if going 24V? Wouldn't they both need a 60A? (1020W/12V=42.5A)

Thanks, you guys are awesome.

Oh yeah, Midnite claims that GFP is required on all PV systems, but if you say a general rule of thumb is GFP is not required for anything under 125V , I won't worry about it. Thanks!

You need to clearly define what your "needs are", then start the safety/loading calculations.

For example:

1,020 Watt AC max load * 1/0.85 inverter eff * 1/10.5 battery cutoff voltage * 1.25 NEC wiring+breaker+fuse safety factor = 143 amp @ 12 volt minimum wring+breaker branch circuit rating (round up to next standard size)

If you are going 24 volt, then the same calculation with new battery cutoff voltage:

1,020 Watt AC max load * 1/0.85 inverter eff * 1/21.0 battery cutoff voltage * 1.25 NEC wiring+breaker+fuse safety factor = 71.4 amp @ 24 volt minimum wring+breaker branch circuit rating (round up to next standard size)

It is ugly--But it is what happens with power systems... Something that "should" only take:

1,020 Watt Inverter AC load / 24 volt nominal battery bank = 42.5 amps DC input to inverter

And you got some unknown guy on the Internet telling you to wire it up for a stupid amount of current at 74.1 amps minimum instead.

If you wire it for ~40 amp circuit+breaker and never pull more than 500 watts or so (for more than a few minutes) will a full battery--Your system will work fine and that guy on the internet will have been wrong. :roll:

-Bill "been there, done that, will do it again someday" B.

BB. · January 2014

Re: Proposed System - 1000W - Advice Needed!

I should also add, it is surprisingly difficult to draw a constant 1,020 watts from an AC inverter with random loads around the home... A little more, and the inverter may fault... A little less, then the currents are lower and will not cause any problems.

So, while my answer may be "exact" (for sake of discussion/simplification), it may also not be really practical either for many people.

However, that is how codes are written and why safety factors are used--In that 1:100 case that somebody does actually pull the ratings from the inverter with a near dead battery on a hot day, and cooks the insulation on the wiring.

-Bill

vtmaps · January 2014

Re: Proposed System - 1000W - Advice Needed!

treefort wrote: »

Oh yeah, Midnite claims that GFP is required on all PV systems, but if you say a general rule of thumb is GFP is not required for anything under 125V , I won't worry about it. Thanks!

There's no rule of thumb on the NEC... either GFP is required or its not. I have only a rudimentary knowledge of the NEC. For what (little) its worth, my understanding is that GFP is required for roof-mounted arrays. If there is a short between the PV (+) up on the roof and ground, the GFP will disconnect the PV (+) from your controller and unbond your DC negative from ground. This may reduce the fault current and prevent a fire. Unfortunately there are other types of faults that may trip a GFP, and there are a couple of documented fires that have been exacerbated by a GFP.

The arc fault protection in the Classic will protect against some of the same faults that a GFP will protect you from. In the future I expect that arc fault will be required in the combiner box. That will protect against more types of fault than the arc fault detector in the classic.

--vtMaps

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

BB - Thank you for the formula and explanation. I only want to do things by code, so that's great. With the batteries being AGM, do the safety concerns still exist? If so, should I dump them or is there a way to tell if they are still good? Does the same inverter formula(different eff %) apply to charge controllers too? The biggest breaker I can get for the MNDC boxes is 100A.

vtMaps - that makes sense. I'm going to install GFP just to be safe.

couchsachraga · January 2014

Re: Proposed System - 1000W - Advice Needed!

FWIW my solution was to call our fine hosts (Northern Arizona Wind and Sun), walk them through my system, what I was thinking, and let me know what they thought.

In the end I have a "Big Baby" box with two breakers - a 300vDC / 15 amp for a panel disconnect and a 150vDC / 60 amp from the Midnite to the batteries in the box and a separate MRCB breaker specific to the batteries that disconnects them from everything.

There is also a separate breaker specific to my inverter that was recommended for that inverter (again, mine is much smaller - SureSine 300w continues / 600w peak)

BB. · January 2014

Re: Proposed System - 1000W - Advice Needed!

Dead Lead Acid Batteries, of any type, tend to stay dead.

And some of the failure mechanisms in Lead Acid Batteries tend to create safety concerns.

AGM's are sealed and have a small catalyst inside them to "recombine" the hydrogen and oxygen back into water. When the catalyst fails (and it will, they have a live of X,XXX AH of charging life--or something like that) -- The gases build up and will pop a pressure valve--venting hydrogen and electrolyte--Which is a mess and can be an explosion hazard (AGM batteries "don't gas"--True, properly working AGMs do not gas, but when the fail, they can gas just like any other lead acid battery).

You can have shorts between positive and negative plates--Which can melt down a cell or a battery wall, or spark of hydrogen gas. You can have lead frames that corrode and fail--High resistance point can start a fire, a failed frame can spark, etc...

As batteries age, the have more self discharge--Which typically goes into "heating" of the battery. One battery support company sets ~2% current during float as the "about to fail" point for batteries (including flaming failures).

In general, lead acid batteries are pretty safe if treated with respect. And a failed/dead lead acid battery has next to no hope of every being "recovered" at home. And the risks of running a "recovered" battery is that it will stop working in days or weeks... Or that it can/may (unlikely but still possible) fail in a dangerous manner.

Here are links to battery failures:

http://amertekspt.com/battery_services.php (bottom 1/2 of web page)

http://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery#Risk_of_explosion
Attachment not found.

Images for lead acid battery explosion (google image search)

Anyway--Not to beat a dead horse--Batteries should be treated with respect. And what we can get away with messing around with a 35 lbs car battery is not the same that you want to do with a 500 lbs lead acid battery bank.

There is a lot of energy (electrical) and pretty strong sulfuric acid (many gallons in bigger batteries).

AGMs are relatively "nice" compared to other battery types... But they still can bite.

Because we don't know the condition inside your batteries, we don't know what batter charger (or how large of battery charger) you are using, is this outside or inside under a bed, etc.... There is just no way I can tell you what "you" are doing is safe (or not). But, in my humble opinion, the risk is not worth the possible (remote) reward.

And have I messed around with car batteries as a kid and lit off the hydrogen gas, etc... Yep. And I still have all my eyes and fingers. And the family home is still standing (I still think it was neat to have my own 4' tall fireworks show when I lit off magnesium shavings on our concrete steps next to our wood sided home--And the concrete spalling sent little arcs of white hot magnesium through the air with me an a couple friends sitting half a foot away). Don't recommend doing that--But it was pretty.

-Bill "getting off high horse now" B.

zoneblue · January 2014

Re: Proposed System - 1000W - Advice Needed!

Zoneblue, why would the controller need a bigger breaker than the inverter if going 24V? Wouldn't they both need a 60A? (1020W/24V=42.5A)

Sorry, for 24v, a 50A breaker. My point was that higher battery voltage simplifies lots of things. And reduces cost.

Oh yeah, Midnite claims that GFP is required on all PV systems, but if you say a general rule of thumb is GFP is not required for anything under 125V , I won't worry about it. Thanks!

The GFP requirement is in the NEC, true, but it's intention is to mitigate high voltage grid tie array fires. In certain situations they can actually make an off grid setup more dangerous. But heck dont trust me, do the reading and decide for yourself. If you design and build a house sized system, you are assuming the role of the Electrician. Just because it isnt connected to the grid, doesnt mean that your power system wont kill you, or burn your house down. Off grid systems are equally capable of doing that, as Bill rightly points out, more so.

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

Thanks for clearing that up zoneblue. I hear ya, 24V would be the better decision. But I bought the inverter already, and 1000W 12V system is doable, right? I'm probably going to have to buy new batteries now too, and it seems 12V ones are not recommended(everyone seems to be using 2V or 6V ones, I'm guessing to eliminate unbalancing by wiring them in parallel). Meaning I'd have to buy 4 6V batteries instead of 2 for 12V.. And then the capacity and charge/discharge rate would go up and I would be wise to get more panels. My cabin is pretty small(800 sq. ft) so I don"t think running 14AWG should be a problem for my low power(<10W) 12V lighting either. Am I looking at this correctly?

Thanks couchsachraga, it's helpful knowing other people's set ups.

And thank you Bill for taking the time to write such detailed replies. The batteries are charging in my little carpentry shop next to the house with a 4-24A automatic MotoMaster Eliminator Intelligent Battery Charger. So, 24A max. I'm going to charge them, test them, if they look good then charge them again, let them sit for a couple weeks, then test them again. That should give me somewhat of an indication whether they are good, right? The batteries were never used before and I got them for free so it would be a big waste if they are bad, but c'est la vie. If they prove to be bad, would 2 Surrette 6v 400 Ah S530 batteries for $800 be a decent choice/deal?

Because you/I/us in general have to keep the inverter close to the battery bank, and it would be unwise to put the batteries outside the house and run the wires for the inverter/charger/disconnect into the house(which I imagine a lot of people do), do you recommend I mount everything in a vent ventilated outbuilding and run a couple big ac and dc wires into distribution panels inside the house? Is this what everyone does/should do? Running the ac with the dc will add noise onto the dc line, right? So, should I separate each run with a couple feet?

Thanks!

BB. · January 2014

Re: Proposed System - 1000W - Advice Needed!

Just watch the battery temperature... Don't let the batteries get above ~115 degree F (45C). Overheating batteries can be a sign of failure, or over voltage/over charging.

-Bill

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

Ok, will do. I will buy an infrared temp gun tomorrow and hand check them in a bit. Thanks Bill

vtmaps · January 2014

Re: Proposed System - 1000W - Advice Needed!

treefort wrote: »

do you recommend I mount everything in a ventilated outbuilding and run a couple big ac and dc wires into distribution panels inside the house? Is this what everyone does/should do? Running the ac with the dc will add noise onto the dc line, right? So, should I separate each run with a couple feet?

I prefer batteries and electronics be outside the house, but this is not always practical. My preference is based more noise, than on safety... the electronics make audible and RF noise which I find bothersome. Of course, I'm happy to have a safer system also.

Yes, the AC and the DC should be in separate conduits. If you have battery monitor or remote control of your system, those wires can run with the DC. If you do put your battery & electronics in an outbuilding, why would you want to bring DC into your house?

--vtMaps

zoneblue · January 2014

Re: Proposed System - 1000W - Advice Needed!

treefort wrote: »

I'm probably going to have to buy new batteries now too, and it seems 12V ones are not recommended(everyone seems to be using 2V or 6V ones, I'm guessing to eliminate unbalancing by wiring them in parallel). Meaning I'd have to buy 4 6V batteries instead of 2 for 12V.. And then the capacity and charge/discharge rate would go up and I would be wise to get more panels.

Well, you want:
- one string ideally, two only if you get boxed into a corner.
- a cell technology designed for true deep discharge
- about C10 charge rate.

Thus, do the math: 75A charge rate, means 750ish Ah @ 12v. For GC2 thats 3 parallel strings. But you should be able to find something in L16, 2 x 6V.

But your numbers still seem a bit shifty-around-y. The place to start is your expected load Wh/d. You do have to draw a line in the sand somewhere, and demand is where it starts. Demand dictates PV, PV dictates battery. Bill probably said all this already

The batteries are charging in my little carpentry shop next to the house with a 4-24A automatic MotoMaster Eliminator Intelligent Battery Charger. So, 24A max. I'm going to charge them, test them, if they look good then charge them again, let them sit for a couple weeks, then test them again. That should give me somewhat of an indication whether they are good, right? The batteries were never used before and I got them for free so it would be a big waste if they are bad, but c'est la vie. If they prove to be bad, would 2 Surrette 6v 400 Ah S530 batteries for $800 be a decent choice/deal?

AGM is quite tolerant of being left sitting. You may be lucky and they charge up ok, and you can find some other use for them.

Because you/I/us in general have to keep the inverter close to the battery bank, and it would be unwise to put the batteries outside the house and run the wires for the inverter/charger/disconnect into the house(which I imagine a lot of people do), do you recommend I mount everything in a vent ventilated outbuilding and run a couple big ac and dc wires into distribution panels inside the house? Is this what everyone does/should do? Running the ac with the dc will add noise onto the dc line, right? So, should I separate each run with a couple feet?
Thanks!

A shed, gargage etc if you have it, else build a lean-to shelter or some such if your climate is mild, or else inside the house is ok, so long as you vent the battery box to the outdoors. Other then keeping the temps happy, where ever they are, you obviously need to adequately protect the batterys from small children, pets, bystanders, idiots and other potential causes of accidental short circuits.

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

I don't like noise either, and I'd feel safer somewhat isolating the high current stuff from burning down the house. I will run the remote display cables with the DC into the house.

My prosine inverter is only 90% peak efficient so I was thinking I'd use DC battery power for everything possible. This was why I chose a 12V battery system; I wouldn't have to waste power inverting/stepping down the battery voltage. I see that AC LED lights are over twice as cheap as DC ones though with the same power and lumen rating. I need AC for the on demand Eccotemp LP water heater, and then whatever else. The Sundanzer fridges and freezers are all 12/24 volts as well. Do you know of any fridge/freezers that are 120V and the same/less power than the Sundanzers? It's around $1200 for an 8.1cuft 360WH/day Sundanzer. If you can convince me that I should use AC in my 1000W system, I'm all for it. The plan is to run 14/2 wire throughout the cabin for the future when I do run everything on AC after the upgrade, but was planning on bringing all those into a DC fuse/breaker panel for now.

treefort · January 2014

Re: Proposed System - 1000W - Advice Needed!

Hey zoneblue, thanks for all that info. Very helpful. Here is the load calc I did last week. I have since decided to get a bigger freeezer(50 more watts), but I've got more than 300W of required panels so I think I should still be good. This was also based on a minimum of 1 hr. of daylight.

Oh yeah, aren't flooded lead acid batteries only C2? That seems to be what the majority of people have, no? Would L16s be a better choice (cost and quality wise) over 6v 200AH Surrettes?

westbranch · January 2014

Re: Proposed System - 1000W - Advice Needed!

there are a lot of everyday fridges (Frigidaire, Whirlpool, etc)now that run on about 1 Kwh/day.
Here is one link, cant locate the others, look at the Gov Canada web sites for Energy consumption.
They are a lot cheaper than the Sundazer and other DC powered fridges, you will have to check around, but don't dismiss the one at, eg, Sears etc. For the price difference you can buy more PV , or an MPPT CC, or bigger batteries...

hth

BB. · January 2014

Re: Proposed System - 1000W - Advice Needed!

I will put my two cents in...

12 VDC is pretty difficult to send much power any distance... You end up with lots of expensive heavy gauge cable for even smallish loads.

For example, a 100 watt loads and a generic voltage drop calculator. ~4 volt drop on a 120 VAC circuit vs 0.5 volt drop on a 12 VDC circuit:

100 watts * 1/120 VAC = 0.83 amps
14 awg cable--How far with ~4 volt drop => 800 foot circuit length

100 watts * 1/12 VDC = 8.3 amps
10 awg cable--How far with ~0.5 volt drop => 25 foot circuit length

And remember to fuse/breaker each branch circuit leaving the Battery + bus (or the AC inverter--if needed).

And, there is the issue of a typical 12 volt device expecting a car circuit running 12.5 to 14.4 volts... A true deep cycle battery runs 10.5 to 15.0 (or even 16.0) volts. Many 12 volt devices don't really like that wide of range (and some devices, like many higher power HAM transceivers are designed for ~13.8 volt power to get rated transmitter output).

I really like a smaller (just big enough) AC inverter (usually TSW) that can power your critical loads. If you have occasional larger loads (tools, microwave oven, etc.), you can have a second larger AC inverter (perhaps MSW--cheaper) to run them when needed (or use a generator for those loads).

-Bill

Proposed System - 1000W - Advice Needed!

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