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GlennWest

solar controller question

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Got some time on my hands now and researching. I have 3 battery paks lithium as many here know. Thinking on solar charging later. Would it be worth the cost to use 2 100 amp controllers vs one? A single 100  amp charger will supply 33 amps to each battery pak. Where as two could possibley supply 66 amps to each. That would cut charging time down considerably. Also add 1k to cost. My solar should be in 4000 watt range residential panels so high voltage. The batteries together can take 200 amps charging. This is the upper limint recommend

Edited by GlennWest

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Batteries are 48v typical. goes up to 58v. Not doing this now so panels are to be determined. With most I looked at I could easily get the volts for two. 

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Glenn, Just a quick glance it seems 4,000 watts will generate less than 100 amps at 48 volts.  I did it my head so check it.  4000 watts divided by 48 volts.  One 100 amp will easily handle all the panels can generate.

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Doubt you will ever get 4000 watts, but 4000 watts at 48 volts is only 83 amps. So your controller must handle that at what ever your input voltage is.. The midnite solar  250 will only handle 250 volts at 63 amps so I had to go with two.

Edited by jcussen

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   Glenn, lets work through the math: Ifffffffff you had 4000 watts of rooftop solar panels (per your post) configured at so called 48 volts (Vmp higher) and the sun was bright and direct overhead (yeah right how often does that happen subject to geographical location and time of year) the MAXIMUM current (roof down to charge controller) would be 4000/48 or 83 Amps.

  NOTE One (I would) may consider configuring your panels to produce 96 so called (Vmp higher) Volts to reduce current provided your controller can handle that. 4000/96 = 41.5 Amps down from panels to charge controller. Orrrrrrrr even higher volts subject to controllers max input voltage rating. The higher your net panel voltage (48 or 96 or 100+)  the less current down to your solar charge controller...

  Now CHARGING CURRENT to your battery bank::::: If you had 4000 Watts of solar power (less controller inefficiency) and were charging your 48 Volt battery bank at lets use 56 volts (NOT exact it varies) 4000/56 = 71MAX CHARGING AMPS (24 each to 3 banks, less due to inefficiency)

  THEREFORE a 100 Amp solar charge controller (48 or 96 or ?? Volts IN and up to 4000 max watts (less inefficiency) OUT ) will handle all your 4000 rooftop solar watts can deliver and three perfect equal balanced 48 volt battery banks would each receive 1/3 of the total available charging amps.

 NOTE when you state two controllers will provide twice the charging amps DONT FORGET a solar charge controller cant deliver more power then the solar panels can provide. If you have 4000 solar watts you cant deliver more then 4000 watts to charge your batteries !!!!  and 4000 watts at 56 charging Volts only equals 71 charging current amps !!!!!!!!!!!!    

NOTE this is based on YOUR 4000 solar watts and YOUR 48 volt battery bank and solar charge controller post NOT any shore powered charger 

 BOTTOM LINE a 100 Volts in 100 amp at 56 charging volts output rated solar charge controller can handle your 4000 watts of solar panels  AND TWO CONTROLERS are nottttttttttttttttt required NOR will the use of two provide more charging current, ONE is plenty to handle 4000 solar watts of power.   

 When the sun shines bright and is overhead (still subject to suns angle in sky and intensity) if you were harvesting say 3000 watts that will provide a lot of power maybe enough to keep batteries near 100% SOC and you wont require much charging??  

 Got it ??? What you think ?? Any more questions ??

DISCLAIMER Im NOTTTTTTTT any solar expert so take this with a grain of salt, but I do know you cant get any more power to charge your batteries then your panels can deliver regardless how may controllers you use

 

  John T  Live from The Florida Flywheelers antique tractor show in hot n sunny Fort Meade Florida 

 

Edited by oldjohnt

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Your Charge Controller must be sized for the max voltage from the panels. If your household panels have too high a voltage, You could divide your panels and have two controllers with a split battery bank. But with limited solar watts, there is maybe no need. As pointed above. 

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1 hour ago, GlennWest said:

Thanks John. Got it

Welcome, by the way I wouldn't be discouraged, your proposed 4000 watts of solar may be above and beyond what you will ever require in reality. When researching I'm sure you will find Solar Charge Controllers rated at 100 or more charging amps at sufficient voltage output and up to a hundred Volts or more input suitable for charging your Lithium based battery pack. MAY NOT BE CHEAP however lol.  Matching the controllers charging output parameters to what's recommended for your batteries is important, but you already know that...……...

John T

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Pretty much decided on the Magnum PT-100. Throw all the power in I can into it to get as much charging as possible. Although a Victron 150/85 would handle it as well. A few hundred less too.Am I correct in that since I am liminted to 70ish amps, there is no benefit for a 100 amp charger? 

Edited by GlennWest

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It will depend on the panels and wiring. the PT-100 will accept up to 248 volt input, while the Victron, 150 volts. Running 96 cell panels will give you 60 volts per panel,  72 cell will be about 48 volts. So running series/parallel is your best bet to avoid a lot of heavy gauge wires. I am running two 2600 watt strings in series parallel at 240 volts, so can get by with 8 gauge from each string. Lower voltages will require bigger wire.

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14 minutes ago, jcussen said:

It will depend on the panels and wiring. the PT-100 will accept up to 248 volt input, while the Victron, 150 volts. Running 96 cell panels will give you 60 volts per panel,  72 cell will be about 48 volts. So running series/parallel is your best bet to avoid a lot of heavy gauge wires. I am running two 2600 watt strings in series parallel at 240 volts, so can get by with 8 gauge from each string. Lower voltages will require bigger wire.

Understand this. Aside from smaller wire is there a performance benefit to a 250v controller vs a 150v controller? While I do like the smaller wire, the price  goes up hundreds on inverters. Got the money but don't want ot buy more with no benefit

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3 minutes ago, GlennWest said:

Understand this. Aside from smaller wire is there a performance benefit to a 250v controller vs a 150v controller? While I do like the smaller wire, the price  goes up hundreds on inverters. Got the money but don't want ot buy more with no benefit

Don't know if there is any difference in performance between the two. I went the high voltage route because my panels are on the roof of my S&B, so a long run of wire was necessary. I bought two Midnite Solar 250 volt charge controllers for $350 ea, for redundancy, and in case I wanted to expand in the future.

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3 minutes ago, jcussen said:

Don't know if there is any difference in performance between the two. I went the high voltage route because my panels are on the roof of my S&B, so a long run of wire was necessary. I bought two Midnite Solar 250 volt charge controllers for $350 ea, for redundancy, and in case I wanted to expand in the future.

yes, i am liminted on charging amps due to physical size of roof. I can wire for higher volts. But as i understand 150 volts or 250 volts is going to put out same charge rate due to my wattage solar output. If i am wrong would like to know

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12 minutes ago, GlennWest said:

Just found out Victron software works on Chromebook. Was wondering so downloaded and worked. 

Good to know,  have the Victron controllers and inverter in the coach,  the bluetooth feature is great.

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1 hour ago, GlennWest said:

Am I correct in that since I am liminted to 70ish amps, there is no benefit for a 100 amp charger? 

Even if your current plan limits you to 70 amps, if a 100 amp charger is available and even if there were  no other benefits, Id still opt for a 100 amp (versus say a 70) to allow for expansion and so as to NOT being on the very limit of a lower rated charger. 

NOTE again the higher net voltage you configure your solar panels, series or series parallell etc,, the less amps you have to carry from rooftop down to your solar charge controller, which can mean smaller wire and potentially less line voltage drop.

NOTE in order to decide on a solar charge controller you need to first decide on how you configure your panels and at what net voltage. Does the controller accept say 100 volts or 200 or more input ???? and what current can it deliver.   NOT knowing your solar arrangement Id still guess some sort of a series/parallel configuration and Id expect maybe a minimum of 96 volts up to 150 or more would be the way to go...……..

 As far as charging current ratings, since your batteries are 48 volt you have to charge at that rate which is likely in the 52 to 56+ volt range.

 Decide on your panel configuration and consider a higher net voltage, then choose a controller that will handle your voltage and can deliver all the charging amps your solar power can supply...... 

Im confident you will get this...….

John T   NOT any solar expert so consult with the more experienced gents here

 

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17 minutes ago, GlennWest said:

But as i understand 150 volts or 250 volts is going to put out same charge rate due to my wattage solar output. If i am wrong would like to know

Glenn, YOURE RIGHT           The higher voltages reduce current from panels to controller, but how many charging amps you can pump into your battery bank is not dependent on the controllers input voltage (be it 48 or 96 or 200) but rather how much solar power you have...

 John T  

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22 minutes ago, oldjohnt said:

Even if your current plan limits you to 70 amps, if a 100 amp charger is available and even if there were  no other benefits, Id still opt for a 100 amp (versus say a 70) to allow for expansion and so as to NOT being on the very limit of a lower rated charger. 

NOTE again the higher net voltage you configure your solar panels, series or series parallell etc,, the less amps you have to carry from rooftop down to your solar charge controller, which can mean smaller wire and potentially less line voltage drop.

NOTE in order to decide on a solar charge controller you need to first decide on how you configure your panels and at what net voltage. Does the controller accept say 100 volts or 200 or more input ???? and what current can it deliver.   NOT knowing your solar arrangement Id still guess some sort of a series/parallel configuration and Id expect maybe a minimum of 96 volts up to 150 or more would be the way to go...……..

 As far as charging current ratings, since your batteries are 48 volt you have to charge at that rate which is likely in the 52 to 56+ volt range.

 Decide on your panel configuration and consider a higher net voltage, then choose a controller that will handle your voltage and can deliver all the charging amps your solar power can supply...... 

Im confident you will get this...….

John T   NOT any solar expert so consult with the more experienced gents here

 

Only way I could upgrade would be hang panels on the side like an awning.  I was caculating all the space being used on top. 

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Putting 4000 watts on the roof is going to cover nearly everything.  There are some 400 watt panels that are about the same size as 330 watt panels but still that many panels will cover the vents and most anything else on the roof.  Not much room for anymore up there.

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Nothing up there but vents and antenna. My short box that my cassette resides in I will arch up and level off and they slope down to normal level, likely enough to clear vents. May shorten vents also. The antenna has not been used in years. It may go away.

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17 hours ago, Randyretired said:

Putting 4000 watts on the roof is going to cover nearly everything.  There are some 400 watt panels that are about the same size as 330 watt panels but still that many panels will cover the vents and most anything else on the roof.  Not much room for anymore up there.

May need to look more. All I seem in 400 watt were so longer. I can get 5 of those on each side. shorter panels, high efficiency, 350ish,I can fit 6 on each side. So either way 4kish.

Edited by GlennWest

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21 hours ago, GlennWest said:

Only way I could upgrade would be hang panels on the side like an awning.  I was caculating all the space being used on top. 

I decided to hang 2 panels on the side as you suggest to free up my roof for 9 panels in the 39" x 66" format. This will take up a little over 29 ft of roof length leaving enough room for a walkway to service the panels.

https://lh3.googleusercontent.com/IUMiUb5rFDH4wdqL7cQWkJ_GOqWlJY0len5X5KXT8eWsBbl9Rs6r1RZW5SOdH3M7hfXKPg2uiCBOjdyf-_Gx6zx6KCfIDIQjmjUuRysaTKWTrIy17Ldz96D35-g9oWwLKQlQ_TWCv3PzEG1Ut8vS0RmuTV5pxtH2b5_kc3jdllWdrZkdn2x3l6sw98fT9i8OfqdjWqTWPe-ushiAvB6W85uUTu7iGa7bRt-2Uk8y_VGkaO9CPawhSG94FC_H1-HJN-3hUiYdatgLrh-iwa5M_uYpeqzmEN3VwBU4B-WVo9iKuUrC61zxNaKM0sZK06v_JmsJ3mVKstYFd-r2_RUjHTcfxYOeBj8f5V05q_akSCRdStN55C33O4cNL4ym72SjAeShL2FzB1ICzMizcNacFM1wEoCHuFWNbM7WkhREgQ9Y0vMYfxeKm2eGpGcAsnraIItVk7Bxam-X-GN4r9JVh_FVRZ3DMIo0l7dVbV7BQ1NFTMIlTnOfAjfTe0k9ZcgYLyxEs4IiFjgGY18R6o5UztOD33uypBObuRwAg2QKUO5XTziI6-pZ1-7ovto8wyZygCRYSPKDDdG0PQtXG-dfch6ZmJw6eoPaoSPN9pCEg77C2y9BXNrT5f3JdK9gbzciL1aJHuwwY5SMZfe4nV0HXn9UYYi7YIjNqany0rX45m8KBQ31vERCMA=w640-h480-no

I would go with a cheaper controller like this: https://www.amazon.com/Controller-Regulator-1100W-4500W-Lead-Acid-Communication/dp/B07SVRLMBG/ref=sr_1_3?keywords=mppt%2Bsolar%2Bcharge%2Bcontroller%2Bfor%2Blithium%2B80%2Bamp&qid=1579360650&sr=8-3&th=1

The 80 amp controller I linked to is rated to 4540 watts, ( a little over 80 a) but with 4,000 watts of flat mounted panels you will never see over 4,000 watts of production. I would expect between 2,500 and 3,500 watts of real world output (depending on latitude and season). I would caution about wiring too many panels in series, running the voltage up too high, for the sake of safety. High voltage DC will arc (in fact you can weld with it) and it can be deadly. Please be very careful when installing, covering the panels and keeping the breakers off until you have the connections made.

I went with an Epever 50 amp MPPT for my 2 side panels (620 watts), giving me plenty of headroom in case I want ti upgrade my 12v batteries. I am very happy with its performance so far, but I do not recommend this controller for lithium batteries as there is no programmed setting for them. You can manually set it for lithiums, however, if you know what you're doing.

Chip

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