Wiring Schematic

[Feruko]

Hello everyone,

I'm new here, and I've become invested in the idea of becoming a vandweller. I've been doing weeks (hundred or so hours) of research on electrical works, interior design, plumbing, diy cooling systems, diy heating systems, compost toilets, vans, trailers, etc. etc. I fell in love with the idea of urban stealth camping, and being able to travel nationwide in a tiny house on wheels. I've been watching hundreds of YouTube videos, from how to's, to vlogs on vandwelling. I feel like this is what I am being called to do by my gut. 

I've started work on a crude electrical schematic that I intend to use when it comes time to wire my system to solar. 

I am curious if there is something I might be missing?

Do I need a fuse box for DC appliances? If I have 4 125AH batteries, what is the max Amp load I can run at any given time? Would I be correct in assuming that it is 500amps? I feel like this stuff is a no brainer but I like to ask.

I have no intention of having a 500amp load at one time, I'm just curious if I'm understanding loads and batteries. I feel like that doesn't make a whole lot of sense and is probably incorrect.

As I understand it, it would be 500AH, and that's over 20 hours. So 25amps per hour. How do I know how many amps per hour a single thing, like a water pump, uses?

So let's take an example. A 15w, 12v water pump uses 1.25 amps. Is that 1.25 amps per hour? Or is that 1.25 amps per second? Or what?

 

[highdesertranger]

a couple of things all circuits should be fused. what type of panels are you planning on, 12v or grid tie? why such a big invertor? do you need a 500ah battery bank? you cannot suck 500ah out of a 500ah battery bank. your diagram is hard to read I had to zoom in to read it. the way you hooked up the charge wires to the batteries is not optimal. but that's minor. here is how I recommend to figure it out.
1. add up you daily usage.
2. size your battery bank to your usage. remember you should only draw batteries down to 50% of their AH capacity better yet is 20-30%.
3. size your solar to your battery bank. more is never a problem less is.
so go though that and see how much battery you need. 12v deep cycle batteries are very expensive. I feel it's better to go with 6v true deep cycle batteries. highdesertranger

 

[Feruko]

►"a couple of things all circuits should be fused."

I put in a 40a fuse between the MPPT charger and the batteries. Are you saying I need one somewhere else? If my understanding of electricity is correct, it should be between the batteries and the appliance, right (before the switch panel)? I kinda thought that, but for whatever reason I removed it from the "schematic".

►"what type of panels are you planning on, 12v or grid tie?"

I've been looking at the 400w Renogy 12v solar panels.

►"why such a big invertor?"

My thinking on a big inverter is that it gives me plenty of head space should I want to add more solar watts with a parallel MPPT charge controller. Like having a portable system I lay outside when I'm out camping. My other thinking, and I could be wrong on this, is that having more wattage capability means the inverter isn't working hard do to keep up with my demand which will barely exceed 300w.

►"do you need a 500ah battery bank?"

I thought about that a lot, and I came up with a number around 350a, which would include a custom air conditioning system I've been designing. I might share it in another post.

►"you cannot suck 500ah out of a 500ah battery bank."

I didn't think so, because that would drain the batteries to zero, which basically destroys them.

►"your diagram is hard to read I had to zoom in to read it. "

It's pretty big, you should be able to open in a new tab and it will be much larger than it is in the forum here. Sorry about that.

Thanks

 

[AngryVanMan]

Generally, any wire that connects to a high-amp power source like a battery should be fused as close to the battery (source) as practical. In the event of wiring damage the idea is the fuse would blow, limiting the fire and damage potential. If the fuse is far from the battery, any of the wire before the fuse that is damaged and shorts out will have arcing potential until the wire burns in half or the battery is depleted. This is undesirable in most cases.

An example, a piece of 12 gauge copper wire will not melt until it passes somewhere over 160 amps of current. That's a pretty damn hot arc, about 2000 watts of energy dissipated into whatever items are nearby, flammable or otherwise. That's the equivalent of lighting up about 6 Bunsen burners and pointing them at whatever is nearby in the van.

 

[BradKW]

I have no intention of having a 500amp load at one time, I'm just curious if I'm understanding loads and batteries. I feel like that doesn't make a whole lot of sense and is probably incorrect.

As I understand it, it would be 500AH, and that's over 20 hours. So 25amps per hour. How do I know how many amps per hour a single thing, like a water pump, uses?

So let's take an example. A 15w, 12v water pump uses 1.25 amps. Is that 1.25 amps per hour? Or is that 1.25 amps per second? Or what?

Welcome to the forum Feruko!
A few things worth thinking about:
1) Unless you're spending the big bucks on high end AGMs such as Lifeline 8Ds, you will be much better served by building your bank from 6v "golf cart" batteries...especially if you plan to run high draw devices such as an AC.
2) There's this guy named Peukert and he's not your friend. His law stipulates that the greater the discharge rate of a battery, the lower the delivered capacity.  http://all-about-lead-acid-batterie...amentals/peukerts-law-and-exponent-explained/
3) Ideally you never drop your bank's charge below 50%...even more ideally you don't go lower than 70- 80% on regular basis. Proper battery charging and care is a science of it's own and there's ton's of information in this forum. Just do a search under Sternwake's name.
4) for a daily load of 350Ah, you'd want at least a 700Ah bank capacity. You'd need a lot of solar to keep a bank that size happy.
What are the specs for the custom AC you're planning?

 

[Feruko]

Hi thanks for the response!

►"Unless you're spending the big bucks on high end AGMs such as Lifeline 8Ds"

Those are the kind I was looking at. That and Vmax. Any opinion on VMAX? If I learned anything from vaping, you don't skimp on batteries. Go high-end, or don't go at all.

►"What are the specs for the custom AC you're planning?"

Well, it's going to run by using 3 different things. One is a 15w water pump @12v, another is a Wind Machine Fan (Lasko) running at 100w @120v, and a 90w Ice maker @120v.

If I calculated that correctly, the AC unit will use ~17.5A. So in all it would be about 350AH for that.

It's a system I found on YouTube and designed my own cooler version. You put ice in a 5 gallon round cooler (instead of a 5 gallon bucket), run a water line through some water, the water is pumped up and to the fan into a coil of copper tube and back into the cooler.

 

[Feruko]

I believe I made an error. So, for the 15w Water Pump at 12v, it's 0.8A, for the other to, I didn't convert back to DC. 9.11 amps in DC for the Ice Maker, and 7.59 amps for the fan. So in all, it comes to 17.5A

 

[highdesertranger]

I am so sorry I didn't realize that was your first post. so a belated welcome.
every circuit must be fused. you can piggy back some but it is best to fuse every circuit.
the problem with to much invertor is you are wasting precious energy. you wouldn't want to charge your phone or plug you lap top into a 2k invertor. better off with a 150w-300w invertor. actually it's better to charge these straight off 12v. size an invertor to what you actually need, with a little cushion of course. highdesertranger

 

[Feruko]

I found this:

https://www.amazon.com/Wagan-EL6224...qid=1467159094&sr=8-15&keywords=fridge+cooler

I can cut two holes in the top for a water line. It will be much more efficient than having an ice maker. I didn't think of this before!!

It is 3.3amp draw.

This will change my amp draw from 17.5 (actually 18 because of a math error) to 12.9. So let's call it 260AH.

 

[Feruko]

I am so sorry I didn't realize that was your first post.  so a belated welcome.
every circuit must be fused.  you can piggy back some but it is best to fuse every circuit.
the problem with to much invertor is you are wasting precious energy.  you wouldn't want to charge your phone or plug you lap top into a 2k invertor.  better off with a 150w-300w invertor.  actually it's better to charge these straight off 12v.  size an invertor to what you actually need,  with a little cushion of course.  highdesertranger

It's alright. Thanks for the warm welcome and the great advice!

300W Inverter should suffice!

https://www.amazon.com/Samlex-Solar-PST-300-12-Pure-Inverter/dp/B00H8N97E2

 

[highdesertranger]

dang I am going to be negative again. save your money those thing suck power they don't cycle like a refer. that one says it will lower the temp 36 degrees. so if it's 90 or above whatever is inside is going to be above 54 degrees, not safe for food storage. from my stint with these I found that as it got hotter their ability to cool got worse. so if it was 90 the inside would be like 65+. remember that 3.3 amp draw is 24/7 so that's over 75ah's a day. highdesertranger

 

[BradKW]

Well, whether AGMs are "best" depends on your usage and ability to keep them happy...fair to say that spending $800 on a battery that only gives good performance for a year because you're not set up for it, might make spending $300 on two 6v that give the same performance and last longer if abused, look like the better choice. There's a lot to understand about off-grid systems to avoid wasting a lot of money fast.

If you haven't encountered HandyBob yet, go ahead and do so: https://handybobsolar.wordpress.com/the-rv-battery-charging-puzzle-2/
He's a bit eccentric and not everything he says is gospel, but work your way through the entire site. As your link to a Peltier-based cooler shows, you're not quite asking the right questions yet. In my own experience, this forum has been of great help because I can go off and research stuff on the web and then come here and post my wonderful new insights, and then have people pick it apart. I've gotten way past feeling dumb about this stuff...the more I learn the more I realized every aspect of off-grid systems is worthy of entire books.,,

@2:12am 14.5v accepting 0.4 amps.

Double check IPN pro remote battery monitor with clamp on meter.......... 0.41 amps.

Reduce voltage to 13.6v, reset battery monitor.

So 3 hours 30 minutes to get from 80% charged to 100% charged, returning ~18AH.
This is as fast as this battery can possible be recharged in this range.

This is with a charging source capable of sustaining 40 amps and holding the proper absorption voltage required. Since 40 amps on initial application, only took 3 seconds to bring battery voltage to 14.5v, A more powerful charging source could NOT charge it any faster, unless voltage was allowed to go higher, beyond the manufacturer recommendations of maximum voltage.

I think the battery was closer to 19Ah from full when started as the battery monitor was obviously off. It took 1.5 more hours at 14.5v after the monitor indicated 100% and 0Ah from full for the battery to actually be full. Perhaps a trimetric or Victron or other AH counting battery monitor would be more accurate, IDK.

This particular Northstar AGM battery also needs the High amp recharge from a lower state of charge every so often, to perform well. This battery got a 40 amp recharge from 60% 2 nights ago, so that 3.5 hour figure is still accurate enough for this test.

This time of year, if Sunny, my 198 watts of solar has enough time to hold 14.5v until 0.4amps, but 4 or 5 cycles of solar only, lower and slower recharge, then battery performance tanks. Voltage held for the same Ah removed is noticeably lower and gets worse each cycle, until it gets that high amp recharge.

This AGM is NOT a good solar only recharge battery for this reason, but especially when discharged to the 50% range
regularly. Even if the solar can hold ABSV for long enough for amps to taper to 0.4v at 14.5, it is not enough to maintain peak performance. It simply needs the high amp recharge every so often to remain near its potential,.
Each low and slow solar only recharge, the time it takes for amps to taper to 0.4a at 14.5v increases.

I've seen it take 10 hours for amps to taper from 2 amps to 0.4 amps after 2 weeks of Solar only and incomplete charging.

SO, if you have an AGM, and do not have an Ammeter, you do not know when the battery is indeed fully charged, and it will suffer a shorter lifespan, more noticeable with deeper discharges.

If you have a flooded battery, the amps will not taper as much. When only 2 to 3 amps are required to hold the100AH capacity flooded deep cycle battery at manufacturer recommended absorption voltage, adjusted for battery temperature, then the battery is in the 99 to 100% charged range.

but, With a flooded battery, one can dip a hydrometer, compensate for electrolyte temperature and get a true reading as to state of charge.

The blinking green light on your solar controller or 'smart' charger, indicating full charge, is lying to you, unless you can verify it is not. If you cannot, then it mocks you, and your battery will not live as long as it could.

How much longer? Impossible to guess. Can you set the time at absorption voltage, or the amp threshold at which float voltage is triggered? If so, then do so, and use an Ammeter or a hydrometer to see how long this requires.

My point in this thread is to demonstrate just how long it takes to get from 80% to 100%, with a high quality and hard working, but well cared for AGM battery.

Flooded batteries will likely require longer times in to go from 80% to 100% than the northstar AGM battery used in this demonstration.

And all sulfated/aged/abused/chronically undercharged batteries, depending on the level of sulfation, will take significantly longer than this to reach 100% charged. They need more time held at absorption voltage.

And attaining a TRUE 100% charge regularly, often, is the key to maximizing Lead acid,( Flooded/AGM or GEL), battery longevity.
98% charged is not good enough to achieve ideal maximum potential lifespan, but 98% could yield an 'acceptable' lifespan.

'Acceptable' is subjective and different for everybody.
Ideal is pretty absolute.

Find your happy medium, armed with the knowledge of what ideal is.
Don't assume your charging sources know when the battery is full. They are guessing, and likely mocking you.

But they are only batteries, and only rented.

I remember  that thread but do not remember its title, I think AKrvbob posted the chart on what was expected from so much solar wattage and a consumption list of devices.

Since solar harvest will vary so widely depending on location/latitude/weather, and devices can draw different amounts brand to brand, and size of device, I'd feel uncomfortable trusting any such chart.

If you are getting 200 watts of solar, I'd not go for more than 232 AH of battery capacity.

232ah is the capacity of 2 gc-2 6 volt golf cart batteries.  This would not be enough solar for 50% discharges nightly, 200 watts is not going to return 115AH+10% more for losses+whatever the fridge and other draws consumes during sunup.

How much your dorm fridge actually consumes will make or break your system, but excessive laptop usage can also consume a lot of battery power.

Not only is a higher solar wattage/ capacity ratio needed just to return what is used overnight, but important that the max charge rate at noon can at least approach 5 amps per 100AH of capacity, but 10% would be way better.

It really depends on the depth of discharge.  the deeper one draws their batteries, the more important the charge rate becomes to overall battery health and longevity.


I have 200 watts on 90AH of  finicky AGM battery, and 50 or 100 more watts would be awesome.
I make regular use of alternator and plug in charging source to keep it as happy as can be with regular 50% discharges, this AGM can accept very high charge rates with ease, and it requires them every so many cycles when deeply discharged.

Flooded GC-2 batteries are much more tolerant of less than ideal recharging.

The Kill a watt p3 meter, used  on your dorm fridge in actual use, for a period of time(24 hours) will be enlightening.  it will give a KWH figure/  Divide this KWH figure by 12.2 for Amp hours, than add 20% more for inverter inefficiency.

http://www.amazon.com/P3-P4400-Elec...&sr=8-1&keywords=p3+international+kill+a+watt

If this number is much more than 55 AH, 200 watts is likely going to be borderline in less than ideal sunlight, and that does not include your other loads

Some dorm fridges are real power hogs, others not so much, but either will consume significantly more than a 12v compressor fridge that was built with efficiency in mind.

The 12v compressor fridge $ stickershock sends many down the path of dormfridge powered by inverter.  But usually this route requires 2x the battery capacity and 2x the recharge capacity(solar) so the savings is just not there once the first pair of batteries are cycled to their premature death.

 

[Spaceman Spiff]

I've started work on a crude electrical schematic that I intend to use when it comes time to wire my system to solar. 

I am curious if there is something I might be missing?

The feed from the solar controller to your batteries is incorrect:  The + and - should be wired to the batteries on the opposite ends of the bank.  This is so all batteries are charged (or discharged) at the same rate.

http://mellomikeadventures.us/rv-batteries-101/

Fuses:  
AYBC code specifies fuse less than 7" from battery, use largest size fuse for ampicity of wiring (to minimize voltage drop), ANL or Class T.
Your solar controller should specify what size fuse to use between controller and panels; ANL or Class T again.
You will want a way to disconnect your solar panels (I disconnect the ANL fuse on mine).
You need to fuse the 12 volt inverter wiring.

http://www.pbase.com/mainecruising/battery_fusing

I would add a Trimetric to monitor your system.

Do I need a fuse box for DC appliances?  Yes.  The fuses should be sized for the wires ampicity.

If I have 4 125AH batteries, what is the max Amp load I can run at any given time? Would I be correct in assuming that it is 500amps? I feel like this stuff is a no brainer but I like to ask.

Maximum amps is determined by battery plate's surface area and internal resistance; your bank can deliver very high amps in a short circuit. You could actually weld with your batteries for a short while.

I have no intention of having a 500amp load at one time, I'm just curious if I'm understanding loads and batteries. I feel like that doesn't make a whole lot of sense and is probably incorrect.

As I understand it, it would be 500AH, and that's over 20 hours. So 25amps per hour. How do I know how many amps per hour a single thing, like a water pump, uses?

With 500 AH batteries you have 250 AH (50%) usable over 20 hours (12.5 amps), any faster and you have less amp-hours to use (Peukert's law)

So let's take an example. A 15w, 12v water pump uses 1.25 amps. Is that 1.25 amps per hour? Or is that 1.25 amps per second? Or what?

If you run your water pump for 1 hour you are using 1.25 amp-hours from your battery, use it for 6 minutes you are using 0.125 amp-hours.  The pump uses 1.25 amps as long as it is on.

Welcome.  I hope I am not being too obtuse in my answers to your questions.

 -- Spiff

 

[Feruko]

dang I am going to be negative again.  save your money those thing suck power they don't cycle like a refer.  that one says it will lower the temp 36 degrees.  so if it's 90 or above whatever is inside is going to be above 54 degrees,  not safe for food storage

I don't know if I mentioned it, but that little cooler wouldn't be storing any food. It would only be storing water and a little ice to circulate through the custom AC unit I'm building for it.  And I would turn it off whenever I wasn't using it. Possible I could find a better one, but just letting you know. I plan to also have a propanefridge that can double on electric.

 

[Feruko]

Welcome.  I hope I am not being too obtuse in my answers to your questions.
 
 -- Spiff

Nope, not at all Spiff. That all made perfect sense. Thanks for catching my mistake on the battery wiring! 

So I should probably up it to 700AH battery bank? This would give me at max, 350AH, and a total of 17.5a per hour. Again this would be a maximum for me. I don't see myself using that kind of power daily. I'm a minimalist. The only thing that will really be sucking up power for my system would be the custom AC unit, and I wouldn't even run it all day. I'd probably only run it on hot Florida nights because I get night sweats. During the day the fan alone is enough for me.

 

[Feruko]

I hate how sometimes I feel really stupid. It's so simple on the face of it, but I struggle with execution sometimes. Here is my really bad schematic for the battery bank. 

It's 2 sets of 4 6v golf cart batteries wired in series, 225AH rated each. The 4 are parallel, the 2 sets of 4 are series. Did I seriously eff it up? Or am I on the right track? 

Also, now that I've done it, 4 golf cart batteries at 225AH seems high to me. That's 900AH? Maybe I can go a little less. Like 3 batteries in parallel in 2 sets.

Something in my gut tells me that one of you is going to tell me I'll end up welding my car to the ground if I follow that wiring schematic. lol

 

[Feruko]

I think when it comes time to actually do this, I'll just go to a professional and get it done. Or have one of my electrical engineering friends help me. But here's a redo of my probably wrong one from my previous reply.

I'm sorry for so many posts all at once folks. I'm just thorough. Also I have OCD and schizo, so I'm a little bit antsy if I don't correct myself all the time.

 

[BradKW]

You'll also need to consider balancing the bank...check this out: http://www.smartgauge.co.uk/batt_con.html

I work in construction, so fair to say I know a good many electricians, as well as some EE's too. Here's an interesting thing: after about a year of unfocused and often haphazard study of 12v systems, I know more than they do about putting together an off-grid solar system. Seriously. I realized quickly that there is surprisingly little in common with wiring a house or business, or designing how to power a new brewery, with building an RV system.

They are very helpful when I forget if "series" is + to -, how to protect solder unions from corrosion, or other specific questions...but if any of them were to put together a 12v solar system without taking an interest and researching it, I'd end up with a mess.

Just be patient...being OCD and willing to keep re-writing diagrams is actually a great fit for doing this...I wish I had more of that in me tbh. As far as being schizo, perhaps you could design a two bank system, one 12v and one 48v...

 

[Feruko]

You'll also need to consider balancing the bank...check this out: http://www.smartgauge.co.uk/batt_con.html

I work in construction, so fair to say I know a good many electricians, as well as some EE's too. Here's an interesting thing: after about a year of unfocused and often haphazard study of 12v systems, I know more than they do about putting together an off-grid solar system. Seriously. I realized quickly that there is surprisingly little in common with wiring a house or business, or designing how to power a new brewery, with building an RV system.

They are very helpful when I forget if "series" is + to -, how to protect solder unions from corrosion, or other specific questions...but if any of them were to put together a 12v solar system without taking an interest and researching it, I'd end up with a mess.

Just be patient...being OCD and willing to keep re-writing diagrams is actually a great fit for doing this...I wish I had more of that in me tbh.  As far as being schizo, perhaps you could design a two bank system, one 12v and one 48v...    

Thanks! This is like my 50th version for this diagram, and it certainly won't be my last.
 
I think I finally was able to wrap my head around wiring the batteries in series/parallel correctly.
... I think

 

[highdesertranger]

ok on the last diagram(post 19) the charge circuit is correct the way you have the positive at one end of the string and the negative at the other end. do the same with the 12v tap wires. have the + and - tap at opposite ends. highdesertranger