Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
First Build: (3) 7s16p (7s48p); design and planning
#11
>Shifting gears to solar, if I was to add 24V solar panels to my system, would I just home run those leads into a MPPT charge controller and then land the MPPT leads into the 24V bus bar?
Yes, Solar PV -> MPPT ---> bus.    The bus connects the charge controller, battery, inverter, and the 24vDC->12vDC step-down together.   There might be a shunt in there between the battery negative and the bus to measure amps going in/out of the battery.     You would fuse (or use circuit breakers) between the bus and the things connected + a fuse between PV and Charge Controller.    For inverter output and 12v output you do standard distribution box/fusing for 120v and 12v. 

Agree its fun!  My home is running smoothly now (on solar) so my next project is a cargo trailer conversion to a camper...   of course to include solar + 18650 battery bank!     In fact the plan is park the trailer next the house and tie it into the house battery bank under the house Smile     So I'm really interested to learn what you do and how it works for you.
Reply
#12
Ok, it turns out that I suck at drawing electrical diagrams. With that caveat, here is my electrical diagram.

I know that I have zero fusing or breakers or protection in here at all...largely because I'm not sure if the protection should be on the + or - side of the circuits. So I sure would appreciate any help anyone has for me.

Thanks!

I also have (4) digital shunt meters that I'd like to install to measure battery charging, battery discharging and the 12V load side. I'll reserve a 4th for the solar charging circuit when I add that. But I'm not real sure how to add these digital shunt meters to the circuit, either.
Reply
#13
Excellent diagram.  I've circled places for fusing / circuit breakers.   Typically, you have a central 'box' that contains the busbars / a lot of DC wiring converges - and this is a great place to put fusing.   Fuses protect against SHORTs!! (and overloads) so fire doesn't erupt.    You might do circuit breakers as they not only fuse - but give you on/off switches so you can isolate things to work on the system.    Not sure of your requirements but you might get by with a simple 12v(24v) fuse box (same as 12v power circuits) - and you can pull the fuses to turn things off.  

I would fuse/circuit-breaker the positive wires.     I've made some quick notes.   Again - you might get some additional help/comments here in case I missed somthing Smile
 

"ANL" fuses are true inline fuses and look like this (overview link on Amazon) - https://www.amazon.com/s?k=ANL+fuse&i=au..._sb_noss_2

Here are some cheap inline 'circuit breaker' type fuses - https://www.amazon.com/ANJOSHI-Holders-O...e35d7258cc    I found out that you can only turn these on/off maybe 50 times before they stop working - they are not ment as daily on/off switches.

Here are high quality DC circuit breakers (5, 10, 15, ... amp)  that mount on a DIN rail in the control box    https://www.amazon.com/MidNite-Solar-MNE...226&sr=1-2

This is DIN rail - for Midnite breakers and other things use this standard to mount things inside a control box - https://www.amazon.com/Pieces-Slotted-Aluminum-Inches-7-5mm/dp/B079TX7WDQ/ref=sxin_8_ac_d_pm?ac_md=1-0-VW5kZXIgJDEw-ac_d_pm&cv_ct_cx=DIN+rail&dchild=1&keywords=DIN+rail&pd_rd_i=B079TX7WDQ&pd_rd_r=342cfe49-dfe8-49f7-bdfd-bd82ced94d15&pd_rd_w=gJVRD&pd_rd_wg=X4P31&pf_rd_p=65218b5e-9d60-4e42-83ae-a40c4223301c&pf_rd_r=5PR3WJBBWR57WP6Q275H&psc=1&qid=1592948260&s=automotive&sr=1-1-22d05c05-1231-4126-b7c4-3e7a9c0027d0


For 120v output - you can use standard distribution box / with standard 120v circuit breakers (same as your house)

For 12v output - folks tend to use a 12v fuse box like this - https://www.amazon.com/WUPP-Blade-Warnin...ive&sr=1-8

All the above are examples, not pushing these exact products except for the DC Midnite Breakers (DIN rail mount) I use a lot and I also use Outback DC breakers as they mount to a metal box with on/off toggle sticking out (instead of DIN rail style being inside the box) - https://www.amazon.com/OutBack-AC-DC-Cir...ive&sr=1-3
aventeren likes this post
Reply
#14
Well that was an amazing post! Tons of info! Thanks!

Here is my updated Battery System Diagram with fusing shown, as well as showing the 12V and 110V fuse/breaker boxes and their loads.

I also took my best guess at how the ATS works--but I'm just not sure how it's wired until I get into it. It is my belief that it is integrated into the 12V camper panel/110V breaker panel because I know the camper currently knows what to do when it is given 110V and then what to do when the 110V is taken away. 

Thanks for the tip on the 12-24V fuse block. To accommodate future heater needs, I may need more than a 6-way blade unit--plus I think that I'm going to need more than 30A per circuit and 100A total. I found this 12-way unit, but still each circuit is limited to 30A and the overall limit is 100A--so again, unless I'm missing something, that isn't going to be enough. So the $25 solution appears to be lacking for my use case---unless I just bought several of these...and loaded each to below 100A with all of the attached circuits. But that seems weird. So I need to think on this for a bit. The Midnight stuff that you posted up is pricey. Damn. That appears to be the solution, but dang it those are expensive.

My MPPT solar charger is sounding like it will be either 45A or 60A.

The DC 29.2V charger is 10A

The 24-12V buck converter is 60A.

The battery has a C-Rate of 3.14 and a Max Continuous Discharge Current of 10.0A. Given my newness here, I'm not even sure how to determine the amp rating of that circuit.

The little PTC heaters I'm looking at are something like 10W, which would be 10W/24V = 0.42A--so not much on those--and I may have a few of them bussed together somehow depending on how many W it takes to keep the batteries above 50°F in the winter when charging.

I did read that my 18650 cells have a charge range of 10-45°C (50-113°F), discharge range of -20-60°C (-68-140°F) and storage range of -20-50°C (-68-122°F). So I should be ok from a discharge and storage temp perspective so long as I don't charge them when they are <50°F (hence the PTC heaters and insulated box).

I haven't looked at 24-110V inverters yet, but I have to think those are going to be in the range of 2000-4000W on the AC side--and I'm not sure on how that will translate to amps on the 24V...but a lot.

So I need to think a bit on the fusing plan. I could run with a mixture of 6- or 12-way blade types (keeping attached circuits to below 100A), and then some purpose driven in-line fuses for the larger loads (inverter, buck converter, MPPT, etc). This kind of makes me wish that I would have designed around a 48V battery now!
Reply
#15
Looks OK except the ATS.  The ATS (Automatic Transfer Switch) is 110v only ...   you have it 'connected' to 12v in the diagram.     For 12v - you indicate you have a manual switch, to switch between the vehicle 12v battery or the 12v from the 18650 battery system.    This manual switch (12v) would be completely unrelated to ATS (110v). 

An ATS is a "Y" device where one input is Shore(ExternalPower) 110v and the other input is Generator(Inverter) 110v and the box chooses one or the other - for a single 110v output.   The box has a pair of relays that are mechanically connected - e.g. when 1 turns 'on' the other turns 'off' and vice versa. 

The Generator(Inverter) input takes precedence.  If the ATS detects 110v from the inverter, the internal relays will click over to let the inverter 110v thru to the output.   If the Generator(Inverter) turns off, then the relays goes back to let Shore power thru to the output if Shore is energized.     If both the Shore and Inverter are 0v then things just stay as they are as there's no power to cause the pair of relays to switch.    When you power up next time - if its Shore, then the ATS will let it thru to the output.  If its Inverter, then that will go thru to the output.  If its both - then the Inverter will win and go thru to the output. 

The ATS typically has a 10-20sec declay on the Generator side - e.g. once it detects power on that input, it will delay switching to it for 10-20seconds...  to give the generator time to fully run it's motor.   This is nice for an Inverter when used instead of a generator - it give the inverter a few seconds to fully turn on/power up.    This also avoids a cascading relay switch back/forth in rapid succession...   so the system stays under control. 

FOR YOUR ATS - you should find in your box 2 inputs and 1 output.  So 1 set of 110v wires from shore going to a relay.   Another set of 110v wires that would come from the Inverter's output to another relay (right beside the 1st relay).  Then an output set of 110v wires - this is what goes to 110v sockets around in the camper to power things.     You may find a small circuit board nearby the relays - that does the 10-20sec delay.
Reply
#16
Ok, trying to get the fusing dialed in. I think that I am going to use these terminal post style in line fuses, which are available in 50A, 60A, 80A, 100A, 150A, 200A, 250A and 300A. I was curious if anyone could help me with what size fuses I need per circuit. Here are my questions:

1. My MPPT solar charger is sounding like it will be either 45A or 60A. So should I buy an in-line fuse rated at 50A (if 45A MPPT) or 60A (if 60A MPPT)--should I upsize the fuse and buy a higher amp rated fuse...and then if upsize, how much much upsized?


2. The DC 29.2V charger is 10A. So would buying a 50A fuse be overkill here? Should I be running this through a blade type 10A or upsized fuse?

3. The 24-12V buck converter is 60A. Again, do I run a fuse right at 60A or upsized?

4. The little PTC heaters I'm looking at are something like 10W, which would be 10W/24V = 0.42A--so not much on those--and I may have a few of them bussed together somehow depending on how many W it takes to keep the batteries above 50°F in the winter when charging. Should I just run these through a small fuse block--and then do I run 1A or upsized fuses per PTC heater circuit?

5. Inverter. I have not planned for an inverter at this point, but our microwave is 1,350W, so we would likely do either a 2,000W or 3,000W AC inverter. I Googled around, and found that these have an internal efficiency of something like 90%. So a 3000W inverter converting to 120V-AC would be 25A-AC at 100% efficiency and 22.5A-AC at 90% efficiency. On the DC side, 3000W at 25.2V-DV would be 119A-DC at 100%. A 4000W peak burst at 25.2V-DV would be 158A-DC. So how would I fuse this circuit? What is the rule of thumb here?


6. 24V battery to 24V busbar. The 18650 cells I bought have a C-Rate of 3.14 and Max Continuous Discharge Current of 10A. My battery is (3) 7s16p banks for a total of 7s48p with a nominal voltage of 25.2V and a max charge voltage of 29.4V--although the DC charger I bought is only rated at 29.2V and 10A. The cells have a Typical rating of 3.18Ah, which makes my 7s48p battery 152.6Ah. So how would I size this fuse based on the above 24V circuits? 

Thanks a ton. I REALLY appreciate your questions and comments.
Reply
#17
Let me try to move the conversation forward on fusing...   there are couple of reasons  to fuse:

1) No 1 is to protect the wire itself.   You don't want current to burn up the wire causing meltdown, shorts, fire etc.  So a fuse/circuit-breaker should 'pop' before the wire burns. 

2) Mo 2 is to protect a  devices.  A lot of devices (such as an inverter) will have their own protection built-in so you don't need to do anything, but some devices do not such as the DC-DC converter.   In this case, its OK to fuse the device as long as the fuse is <= what's needed to protect the wire.

3) Other - there are other reasons but the above is primarily what I use as guidance.


Let me try to give some guidance to your questions:

>1. My MPPT solar charger is sounding like it will be either 45A or 60A. So should I buy an in-line fuse rated at 50A (if 45A MPPT) or 60A (if 60A MPPT)--should I upsize the fuse and buy a higher amp rated fuse...and then if upsize, how much much upsized?

Solar panels 'max out' in the current they deliver - even if you short them.   So you don't have to worry (like you do with grid power or battery bank) about 'huge current inrush'  With proper size wire, it will never burn up - so fusing is not required.    I would get something to allow max amps to the Charge Controller (so you can add more panels later) but mainly its about on/off so you can disconnect the current flowing into the charge controller when you want to work on the wiring.
*Lightning surge - I don't have good data on this but a thread a while back indicated that one shouldn't worry about rubber tire vehicles with panels on top.


>2. The DC 29.2V charger is 10A. So would buying a 50A fuse be overkill here? Should I be running this through a blade type 10A or upsized fuse?

On the DC side, this is like the panels above - the DC going into the battery is 10a max - it won't surge to 100a if it shorts - so this is not needed as long as wire is big enough to handle 10a.   Its OK to put a 10a fuse on this in case the wire's short or the device shorts internally? - but this is not a high priority in my mind.  I don't fuse the output of my chargers.    On the 110v AC side - the 110v plug (the charger is plugged into) should have a circuit-breaker at the distribution box for the AC wiring.   


>4. The little PTC heaters I'm looking at are something like 10W, which would be 10W/24V = 0.42A--so not much on those--and I may have a few of them bussed together somehow depending on how many W it takes to keep the batteries above 50°F in the winter when charging. Should I just run these through a small fuse block--and then do I run 1A or upsized fuses per PTC heater circuit?

Sounds good.   In this case, my thought is you want to fuse the wire from the battery to buss (rather than each individual PTC) so that if any one of them 'short out' the fuse will pop before the wire burns up.  


>5. Inverter. I have not planned for an inverter at this point, but our microwave is 1,350W, so we would likely do either a 2,000W or 3,000W AC inverter. I Googled around, and found that these have an internal efficiency of something like 90%. So a 3000W inverter converting to 120V-AC would be 25A-AC at 100% efficiency and 22.5A-AC at 90% efficiency. On the DC side, 3000W at 25.2V-DV would be 119A-DC at 100%. A 4000W peak burst at 25.2V-DV would be 158A-DC. So how would I fuse this circuit? What is the rule of thumb here?

Make sure the wire from battery to the inverter is large enough - e.g. 3000w inverter / 24v battery = 125a could flow.  So 125a or 150a fuse with wiring to match.   The inverter itself should have internal fuse - so I wouldn't worry about the inverter.   This is a case of fusing the wire in case of a short - e.g. I've had an inverter cause a dead short when it blew up and trip the breaker between the battery and the inverter.  


>6 24V battery to 24V busbar. The 18650 cells I bought have a C-Rate of 3.14 and Max Continuous Discharge Current of 10A. My battery is (3) 7s16p banks for a total of 7s48p with a nominal voltage of 25.2V and a max charge voltage of 29.4V--although the DC charger I bought is only rated at 29.2V and 10A. The cells have a Typical rating of 3.18Ah, which makes my 7s48p battery 152.6Ah. So how would I size this fuse based on the above 24V circuits?

NOTE: When you say "....typical rating of 3.18ah...' your mixing capacity with amps.   Capacity is overall power in the cell.   The C rating is the spec that says how fast (how many amps) you can draw at any giving second.    A 1 C = 3.18a max draw/cell    A 2 C would be 6.36a max draw.     

Fuse to wire and max you want to draw out of the battery.    Let's say that 'in theory' you your battery could deliver 1.5C (4.77a/cell).  This would be 4.77a * 48cells = 229a @ 24v.    However...  unless these are high drain (high amp) cells - the voltage typically drops dramatically if you try to pull 4.77a/cell and you'll find the battery reaches 3.0vor 2.8v cut-off within a few minutes.    You should be prepared to do some tests.    I would go with 0.3C (1a/cell) or less a more realistic guide.   1a * 48cells = 48a @ 24v.      So might only need a 50a circuit breaker.    This would be 24v * 50a = 1200w inverter.  

You can wire for a 100a / 2400w inverter or  200a / 4800w inverter - no problem in terms of fusing/circuit-breaker.  But if you were to draw that much power from the battery it could exceed what you want it to handle.    

So just match things up  between  1) what the battery is capable of handling + 2) wire size to the inverter.    

FYI....
 In my home system, my battery 'could' deliver 1,500a - however I have it shunt-triped (fused) at 400a as this is the max the overall system (inverter discharge,  solar charging) need.  Its also the max the wiring can handle and its also the max I wanted to spend on a circuit breaker Smile
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)