In line fuse and wire size

mike95490 · October 2008

Re: In line fuse and wire size

Here's a great writeup on how to properly wire your battery bank (diagonally)
http://www.smartgauge.co.uk/batt_con.html
it explains why, and has several diagrams too.

niel · October 2008

Re: In line fuse and wire size

dd,
a 3ft run of wire is actually 6ft of wire, not 3ft, because you have 2 wires that are 3ft one being + and one being -.
the voltage drop calculator in the sticky will do all of that except take into account humidity.

Different Drummer · October 2008

Re: In line fuse and wire size

Thanks Mike,
A very informative site. But remember, I only have two batteries in Parallel. Not much choice in how I wire the batteries to each other.

mike90045 wrote: »

Here's a great writeup on how to properly wire your battery bank (diagonally)
http://www.smartgauge.co.uk/batt_con.html
it explains why, and has several diagrams too.

Different Drummer · October 2008

Re: In line fuse and wire size

Niel,
You must be up past your bed time.:roll: Review my post on the wiring.
I understand what you are saying, but my negative lead is not the same length as my positive lead. So my entire round trip does not equal 6 feet.
More like 3 feet, 6 inches when Pos. and Neg. length runs are added together.

niel wrote: »

dd,
a 3ft run of wire is actually 6ft of wire, not 3ft, because you have 2 wires that are 3ft one being + and one being -.
the voltage drop calculator in the sticky will do all of that except take into account humidity.

niel · October 2008

Re: In line fuse and wire size

sorry, as i overlooked that and i'm guessing i'm not alone. past my bedtime? no, i'm just up too early.:p

Different Drummer · October 2008

Re: In line fuse and wire size

I found the voltage drop calculator that was developed by Bocck.
I think I am doing everything correct in using it but it doesn't seem to supply the final figures for me. I substituted my information as directed. I put 0 values in the combiner box to breaker and breaker to controller columns.
AWG #10 and 30 feet in the panel one catagory. Placed 0 in the Amp column for #2 and #8 panel position. 0.92673 is the % drop I get. 0.39665 is the % drop for controller to battery. I notice that the latter figure is offset one column to the right. It does not align with the % column . Also it does not give me the total % loss as in brocks example. I guess I can just add them together for total % loss. N/A appears in the Comb. box to breaker and breaker to controller. I understand that this is because I added 0 to the input for these two values. But I am curious as to why the end % drop and the end V drop are not calculated and shown.
This brings me to another Question. "Combiner box to Breaker" on the spread sheet. Am I going to need to place a fuse in the line from the panel to the controller? I wasn't planning on it. So I am asking before it is too late!

Different Drummer · October 2008

Re: In line fuse and wire size

Different question on my system.
My MH system will be a hybrid, at least initially. There is an onboard propane fired 3600W generator. I also have a 40A Temp. compensating multistage smart charger. Initially I was thinking of running the Gen. in the evening for about an hour. This is when the SO likes to watch the local and national news. TV is 12V. That way the TV would be powered off the converter (as well as lights etc.) while the charger is charging the Batteries.
I thought that this would be an effecient use of the Gen. for an hour.
Howver, perhaps it would be better to run the Gen. in the morning using the 40A charger to rapidly do some bulk charging, then let the solar system finish the charging. The latter would seem the best approach. However, there is the point to consider that by running the Gen. in the evening some of it's output would be powering the TV and the lights.
Please offer Comments and opinions.

BB. · October 2008

Re: In line fuse and wire size

Regarding the generator--yes, the usual recommendation is to run the generator first thing in the morning to power the coffee maker and microwave, and bulk charge your batteries... And let the solar panels top off the batteries the rest of the day (if you need assisted charging).

Basically, most generators have their best efficiencies above 50% rated load--so heavily loading your generator in the morning with appliances and battery charging is usually most fuel efficient.

Below 50% electrical load, the average generator consumes about the same amount of fuel per hour as that to run with a ~50% load.

Even 40 amps at ~15 volts = 600-1,000 watts (depending on charger efficiencies). Your 3,600 watt generator will be most fuel efficient at ~1,800 watt load or more... You certainly don't want to (if you can avoid it) run it while just finish charging your batteries at 10-20 amps (300-600 watts) for hours on end--if you can avoid it.

You can test the efficiency of your genset by running some known loads (perhaps with a kill-a-watt meter or an AC amp meter) and--if possible--use a scale to weigh/estimate how many lbs of fuel per hour you are burning to run your various loads...

For example, a Honda eu2000i will generate around 5,000-5,500 Watt*Hours per gallon of gasoline (which weighs around 6 lbs per gallon) for ~25% to 100% rated load (1,600 watts is max continuous load--the eu2000i is one of the more efficient generators I have seen specs. for at 25% load).

Or, you may be able to find a fuel flow chart vs load for your genset.

Regarding a series fuse from the solar panel to the controller, reading the MorningStar MPPT Charge Controller manual, you do not need to install a series fuse between your solar panels and the charge controller... (at least they don't talk about one)... Generally, I avoid adding "extra" fuses and breakers if not needed as fuses/breakers are (by design because they have to "open" just above rated current) the more unreliable components in a system.

The following is the type of questions that we spent hours discussing/researching when trying to design for safety--Don't read the following if it makes you concerned--it is most likely way overkill in terms of discussion about your application.

Hmmm... We have a choice now--to believe MorningStar that no fuse is needed in the solar panel line, or not... If you are really paranoid about fire/shorts--then, in theory you should have a fuse that is rated for the max series current rating of the solar panel...

Series fuses in line with each solar panel is common in large solar systems... When you have three or more strings tied in series, it is possible to get a short in one panel and have the others feed current to that shorted panel. So, for panels intended for installing in larger arrays--you will see a series protection fuse called out (you will see a series fuse rating called out in the larger panel specification sheets used for grid tied system).

Your system is too small (and not enough parallel panels) to require a series protection fuse (not enough current from your array).

The other question is if the MorningStar controller could have an internal short from panel input to battery output--and, also get a shorted panel--and the battery feed too much current (for a 4.5 amp panel, maybe over 8 amps is the series current "safe" design limit) to the shorted panel and cause a fire.

So then, we have to go back to, in this case, MorningStar and understand if the controller can fail with an internal short from the panel input to the battery output--We, at this point, don't know the answer--that information would have to be supplied to us by MorningStar (and their UL/NRTL safety rating agency). Depending on their design, this (internal short) may not be a problem.

Many times, we default to asking the question about a single failure, and subsequent failures because of the initial failure.

So, in this case--if the solar controller failed shorted to the solar panel input--there is no other failure in the solar panels--so there is no problem.

If the solar panel failed (somebody dropped a wrench into the glass), there is not enough current in the single (or two parallel panel strings) to cause a fire in the solar panel or its wiring.

We do not need to consider the two independent failures (both the controller fails shorted, and there is also a wrench that broke the glass panel)...

How is that reading comprehension thing going???

I pulled out my share of hair over design problems like this...

-Bill

niel · October 2008

Re: In line fuse and wire size

Different Drummer wrote: »

I found the voltage drop calculator that was developed by Bocck.
I think I am doing everything correct in using it but it doesn't seem to supply the final figures for me. I substituted my information as directed. I put 0 values in the combiner box to breaker and breaker to controller columns.
AWG #10 and 30 feet in the panel one catagory. Placed 0 in the Amp column for #2 and #8 panel position. 0.92673 is the % drop I get. 0.39665 is the % drop for controller to battery. I notice that the latter figure is offset one column to the right. It does not align with the % column . Also it does not give me the total % loss as in brocks example. I guess I can just add them together for total % loss. N/A appears in the Comb. box to breaker and breaker to controller. I understand that this is because I added 0 to the input for these two values. But I am curious as to why the end % drop and the end V drop are not calculated and shown.
This brings me to another Question. "Combiner box to Breaker" on the spread sheet. Am I going to need to place a fuse in the line from the panel to the controller? I wasn't planning on it. So I am asking before it is too late!

not too sure what is going on with your using the calculator. i gave the formulas and the data for the calculator while another did the excel spreadsheet with some advice from crewzer thrown in too. brock only allows the spreadsheet to be accessable from his site (appreciated) and he didn't develope it. if you wish for me to calculate it out for you i will. give me all of the specs you wish to be entered as i am not going to reread all to retrieve that adding that sometimes people change them too. i like to do the individual parts and add it together myself just to better track what it is i'm doing and i used to do much of these calculations for people the hard way. this is why the calculator was created to make these confusing and complex calculations easier and less time consuming. i can't say it is as i'd want the calculator and i can't know all of the glitches or what to do about them as i don't do spreadsheets.

Different Drummer · October 2008

Re: In line fuse and wire size

Thanks guys,
BB,
Onan specs say the Gen. uses .6 Gal./Hr. at 1/2 load. I agree about the Honda 2000. I own one. Used it last winter in the desert as the sole source of power. It performed flawlessly and was very effecient. And, I was using the single stage converter that came with the MH to charge with. Not a very good charge method. Ran the Honda about 3 hours a day. I really would like to leave the Honda at home this year. The MH is small and has the onboard Onan. I would save space and weight as well as having to carry provisions for the additional fuel. MH is diesel. Also the Onan would be much more convenient. No moving the Honda in and out of the storage compartment and plugging in at every use. Cannot leave it outside as Honda generators are known to disappear in alarming numbers. My theory/plan is to allow the dedicated 40A charger to charge the batteries while at the same time the factory installed converter supplies the 12V needs of the MH. There is a Battery disconnect switch that will allow me to remove the batteries from the MH 12V circuit during the charging. Of course this year I will have the solar as well. I am hoping I will be way ahead of last years charging method.

Niel,
I am not up on who/where the voltage drop calculator originated from. I followed a link from another post to get to what I think is the one you are using. Maybe it is not the same. I thought I saw the Name "Brock" associated with it.
Anyway following are the Specs.
Advertised: Voc=27V
Vpm=21.5V
Isc=4.88A
Ipm=4.54
Panel to controller: 30 Ft round trip #10AWG wire
Would be nice to make te comparison to the same distance of # 14AWG wire.

Controller to Battery: 4 Ft round trip #10AWG wire
Got a link to the calculator you are using?

Incidently, I have replaced most lighting with LED's, have heat that does not require the central heating blower to run and we are extremely concsious of conservation. I have consented to the 12V TV use. Could get lonely for 5 months by myself. Unfortunately the 19" LCD TV and the antenna amplifier place a pretty stiff current draw on the system. I don't know exactly how much, but compared to our other draws I am pretty sure it is the greatest. This is why I was going to run the Gen. in the evening while the TV may be in use. I would prefer to run it in the AM, but I am afraid that the batteries may be drawn lower than I would like them to be in the evening, and then have to wait till morning to get a charge from the Gen./charger.
I will eventually get a battery monitor that will tell me Amp.Hr. removed and Amp.Hr. replaced. This will allow me to know where my battery status is at any given time.

System2 · October 2008

Re: In line fuse and wire size

I think that your idea of running the generator in the evening is sound because that may be when your largest daily load occurs. I use the technique for my off grid cabin regularly. About 50% of my daily load comes between 8PM and 10 PM. Running the generator during that time provides a good bulk charge and powers the lights at the same time. It really depends when your large loads occur. There may be other factors to consider like night time noise though.

Neil

Magnum MSAE4448, 390 Ahr AGM Batteries at 48V, 600 W PV, and Outback MX60.

Different Drummer · October 2008

Re: In line fuse and wire size

Thanks Neil,
Main draw on the Batteries will definately be in the evening. Noise in the desert is not a problem. We try to park remotely and would not run the Gen. past 9PM. I supose if the Gen. is putting a bulk charg in the Batteries at night, and then we hit the sack, it would be similair to doing the bulk charge in the AM. Once going to bed, battery draw would be near nothing.

ntracht wrote: »

I think that your idea of running the generator in the evening is sound because that may be when your largest daily load occurs. I use the technique for my off grid cabin regularly. About 50% of my daily load comes between 8PM and 10 PM. Running the generator during that time provides a good bulk charge and powers the lights at the same time. It really depends when your large loads occur. There may be other factors to consider like night time noise though.

Neil
Magnum MSAE4448, 390 Ahr AGM Batteries at 48V, 600 W PV, and Outback MX60.

niel · October 2008

Re: In line fuse and wire size

dd,
ok, understand only for the sake of knowing that the calculator brock has was uploaded to him by me.

now on to the business at hand. i noted the pv you have is a high enough voltage that i classified it as an 18v pv and used 18v as the array voltage. (using 12v will result in a higher %, but the actual voltage dropped will be constant) i used 30ft total of #10 at a panel amps of 4.88. this results in a voltage drop of .16922v and is .94013%.
for #14 that is .42776v and is 2.37644%. putting this to 12v would've resulted in .42776v/12v=3.56466% and you now see the advantage of higher input voltage as it changes the percentage.

now the controller being mppt will downconvert and recover a bit of lost power through that mppt action so i made the current to be 1.6 times as much as the pv's rated imp or 7.808a. now this will be at 12v for the nominal battery voltage. yes, this can be higher, but it can also be lower in the case of a badly discharged battery. this 12v nominal battery voltage will also err on the side of a larger percentage than say one floating at 13.5v or so. this gives .0361v dropped and a percentage of .30084%.
the voltage drop here be it in volts or percentages are additive to each other, but only when referenced to the same base voltage. the following is using all #10 wire at the prescribed lengths you just specified. due to the differing voltage referances it becomes necessary to add only the individual percentages together and go by that and it is .94013% + .30084% = 1.24097%. this figure is good and if you go to add say 1 more pv in parallel at the same specs as the first this will change things as doubled the current in the calculator will double the voltage drop and thusly the % on the voltage drop and become .33845vd and 1.88026%. this same doubling will occur on the cc to battery length and will now be .60168%. this is double the original % figure and is now totaling 2.48194%. not good for under a 2% goal, but excellent for under 3%.

does this help? or did i confuse you?

ps adding to say hi to another guy with the same name, but spelled differently.:D

Different Drummer · October 2008

Re: In line fuse and wire size

Thank you Niel,
I understand now why my crediting the voltage drop calculator to Brock caught your attention.

I am understanding what you are doing when I see it. It's just that I would not know how to do what you are doing. I have played around with the calculator and when I plug in the figures that you use I cannot obtain results that match yours. I am not going to give up, and will continue to play with the calculator.
However, two questions. Why did you use 18V for a one panel array instead of the 21.5V? Also you mention the voltage drop when adding another panel. But you also stated in parallel. When I add the second and final panel I was planning on running them in series. I thought that this would be to my advantage. Thus the voltage would be higher and the % of voltage drop would be even lower. Am I going astray somewhere?

Edit: Just returned from the calculator page. If I use 10AWG, 30 Ft. with 18V as array voltage, 12V as battery bank voltage and 4.88 as panel Amps. I get the following figures. Voltage drop= 0.14688
Voltage drop %=0.81599

niel · October 2008

Re: In line fuse and wire size

that's odd. is it at 60 degrees c? inputting only on panel 1 with all others resulting in 0vd and 0% except for the subtotal? after inputting are you clicking elsewhere in a blank area to implement that new data?
i didn't elect to use the vmp of the pvs as the voltage gets drawn down. it is usually at some value between 10.5v and possibly 15v depending on the battery and charge point. normally a non mppt pwm controller will charge a battery from a pv with the voltage differences between that of the pv(s) and the battery is usually wasted. an mppt controller will recover some of that wasted power. i suppose one could get more accurate with the voltages, but i like to err on the safe side of things and the differences won't be great.
i do hope nothing has gone wrong with the calculator i uploaded to brock or my calculator as i'd hate to have to do this by hand again.

sorry about the parallel pvs for the future as i had forgotten you wished to put them in series and i will go ahead and calculate for that. at least you'll see both options as to how they generally pan out.
ok 30ft of #10 with 4.88a and a seriesed voltage value set to 36v gives .16922v dropped for .47007%. this will then be added to the voltage drop percent obtained from the controller to the battery at 2x due to the controller outputting double the current when downconverting to 12v so .30084x2=.60168% + .47007% = 1.07175%.
now even dickering over differences you and i calculate, it will still show the difference between seriesed and paralleled pvs into an mppt controller.
look for a pm from me on a link to try the same calculator from another source.

Different Drummer · October 2008

Re: In line fuse and wire size

Hey folks,
Got my MODBUS adapter today.
My controller is mounted out of sight so I am planning on getting the remote monitor. But I would also like to do some logging with the computer. i.e. Amps in, Amps out. Does anyone know if I could use a Telephone line splitter to be able to connect the computer without crawling into where the controller is mounted to disconnect the remote meter and connect the line to the MODBUS? Or does perhaps the remote meter have a removable plug on the meter end that will plug into the MODBUS.
Also, can anyone tell me if a standard serial cable is wired corectly, or is there a need to start changing the wire locations on the serial connector end?
Could I use one left over from Packet days Niel?

Different Drummer · October 2008

Re: In line fuse and wire size

Niel,
Why would you ever use a voltage as low as 12V? That voltage would no be able to charge a 12V battery bank. Would it?
Perhaps you were doing that to show the loss of effeciency when you lower the voltage?

niel wrote: »

dd,

i noted the pv you have is a high enough voltage that i classified it as an 18v pv and used 18v as the array voltage. (using 12v will result in a higher %, but the actual voltage dropped will be constant) i used 30ft total of #10 at a panel amps of 4.88. this results in a voltage drop of .16922v and is .94013%.
for #14 that is .42776v and is 2.37644%. putting this to 12v would've resulted in .42776v/12v=3.56466% and you now see the advantage of higher input voltage as it changes the percentage.

niel · October 2008

Re: In line fuse and wire size

actually it could charge it. when a battery is lower than 12v, and they can go down to 10.5v before being considered dead, a voltage of 12v inputted to it will send current to the battery (charging it) and the voltage from the 12v charge source would appear lower until the battery reaches that 12v status from charging and at 12v all charging will stop. 12v is a nominal battery voltage. of course this would be a shallow charge only to 12v, but this is what is typically a rough bottom end voltage for many of us with batteries and is a rough worst case scenario for our normal operations, but as i said it can go lower. to use the highest voltage a system gets to is only a best case scenario that one does not want to use as it is rarely at that level and is only a way to fool yourself into thinking it's better than it is. my fully charged agm is at 12.7v at rest (no loads) put loads to it and it's downhill from there until 10.5v where it is considered dead, which none of us want it to go to the point of being dead as it shortens the battery lifespan. hence i implemented the nominal voltage of 12v or 24v etc..
keep in mind too that this really isn't about charging, but is about voltage drops in a system.

edit to add: sorry dd as i missed your question on the serial connection, but in any case i really wasn't much into packet so i couldn't say one way or the other.

wxh3 · October 2008

Re: In line fuse and wire size

Different Drummer wrote: »

Also, can anyone tell me if a standard serial cable is wired corectly, or is there a need to start changing the wire locations on the serial connector end?
Could I use one left over from Packet days Niel?

I use a standard telephone cable connected to the MODBUS adapter connected to a standard RS232 serial cable connected to an adapter connected to a USB cable connected to my laptop.

MSVIEW generally works fine for me on my Vista laptop. Biggest issue I have is that sometimes it hangs and cannot be killed. Laptop cannot even be shut down. Need to do a hard reboot of laptop via longpress of power key. (Edit: BTW, emailed Morningstar tech support about this and they said nobody else has reported this issue, so maybe it is something with my laptop.)

Another significant annoyance is that the daily stats get reset to zero when the sun goes down. I don't think that is MSVIEW though..that is the controller. I think they should get reset to zero when the sun goes up so you can check your previous day's daily stats in the evening.

Different Drummer · October 2008

Re: In line fuse and wire size

Wxh3,
Thanks for the info.
I am not sure why, but I thought that it would log continously and keep cumulative data. I was planning on having to reset it through user input. I was hoping that I could use it to track trends in Amp. hours used.
I run Vista on a laptop as well. Sounds like it resets approximately every 24 hours.

wxh3 wrote: »

I use a standard telephone cable connected to the MODBUS adapter connected to a standard RS232 serial cable connected to an adapter connected to a USB cable connected to my laptop.

MSVIEW generally works fine for me on my Vista laptop. Biggest issue I have is that sometimes it hangs and cannot be killed. Laptop cannot even be shut down. Need to do a hard reboot of laptop via longpress of power key. (Edit: BTW, emailed Morningstar tech support about this and they said nobody else has reported this issue, so maybe it is something with my laptop.)

Another significant annoyance is that the daily stats get reset to zero when the sun goes down. I don't think that is MSVIEW though..that is the controller. I think they should get reset to zero when the sun goes up so you can check your previous day's daily stats in the evening.

wxh3 · October 2008

Re: In line fuse and wire size

Different Drummer wrote: »

Wxh3,
Thanks for the info.
I am not sure why, but I thought that it would log continously and keep cumulative data. I was planning on having to reset it through user input. I was hoping that I could use it to track trends in Amp. hours used.
I run Vista on a laptop as well. Sounds like it resets approximately every 24 hours.

MSVIEW reports a bunch of parameters and you can choose which ones you want to see. These include various cumulative stats, daily stats, present readings, and settings. Also, should note that they don't have logging to file working yet. That is a feature that is supposedly coming in the future.

Also there is at least one 3rd party software available that also reports these parameters and (I think) does actually support file logging. It has been mentioned in other threads. I believe it was created by Solar Guppy that posts on this forum. Maybe there are others as well...

Different Drummer · November 2008

Re: In line fuse and wire size

Just wanted to thank everyone who rsponded to my questions.
I have been out of touch due to a pretty nasty computer virus.
Regards to all,
DD

In line fuse and wire size

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