# charge controler mppt bluesolar 150/70?

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## Comments

20✭thank you for your precious information

if i understand ,

that measn if i have a 250Ah of battery and a charge controler give me 40A at a moment ,then the 40A will not go to the battery ,only (10% of 250AH =25A)?

17,615✭✭No.

The current rating of the charge controller is the maximum it can handle: 60 Amps for a 60 Amp controller.

If there is enough PV and light to output 40 Amps then 40 Amps is what is going to the battery. If there are load detracting from that output then what is going to the battery is the controller's output minus the current going to the loads.

The 10% is the 'target' for peak charge current:

You have 250 Amp hours so you want to be able to supply 25 Amps for charging.

On a 12 Volt system with an MPPT charge controller this requires (25 Amps * 12 Volts / 0.77 efficiency) 389 Watts of solar panels (and good insolation).

It would be okay to go as high as 37.5 Amps (15%) to the batteries (584 Watts of panel to supply it).

Minimal charge rate of 5% would be 12.5 Amps and would require 194 Watts of panel.

These are not constants. Actually current varies with the State Of Charge of the battery, any loads on, and available sun. There is a range that will work, and usually if you try for that 10% peak current all will be well. Adjustments need to be made for unusually heavy loads (enough that will pull the current to the battery below 5%) or poor sun conditions.

As a rule it is better to err on the side of caution: round up battery bank capacity requirements to the nearest available. Round up solar panel Watts to the nearest available. As in the first example you probably won't find panels that add up to exactly 389 Watts, but you can buy two 220 Watt panels and have 440 Watts with a resulting peak current of 28 Amps which the batteries can take without issue.

20✭thank you again

sorry but i still not understand this 10%peak charge current

since if i have 250Ah capacity of battery,if the charge controler like blue solar mppt150/70 can give me 70A at this moment of day ,and i have a panels that can give me this 70A ,than all this 70A will go to the battery,or if it will give me 10Ah than it will go to the battery too,why i should care on this 10% of 250Ah.

than if i have 1000w of panel and 4 equivalent hours of sun ,means 4000wh/day withe 24v then my battery will be c=166Ah *2(50% dicharge)=320Ah that it's

is this correct ?

17,615✭✭When you design a system you use the 10% rule-of-thumb to make sure you get enough charging for the battery. You do not have to limit it to that, but there is a problem with going too high in current to the battery.

If there's enough panel to supply 70 Amps to your 250 Amp hour battery that would be a 28% charge rate. For flooded cells that is very high and will result in a lot of heating of the battery during charging. This will shorten the lifespan and could even cause sudden failure. AGM's can take higher currents; check the makers specifications for those.

Do not confuse Amp hours with Amps: Amp hours (at a given Voltage) is a capacity, Amps is a rate. The battery charging rate (Amps) is based on a percentage of the capacity (Amp hours).

To get 70 Amps peak current on a 12 Volt system you'd need about 1090 Watts of PV and a charge controller capable of handling 80 Amps. Do not confuse the controller's maximum output capacity with the actual current that will flow: if there's not enough PV and/or sun to provide the current or not enough demand for it you will not see the maximum current. In other words if you have 400 Watts of PV on an 80 Amp charge controller you will never see 80 Amps from it because there is not enough power available from the solar panels to generate that much current.

1000 Watts of panel over 4 hours of equivalent good sun will actually generate about 3 kW hours DC. Less when converted to AC and even less if it all has to go in and out of batteries (end-to-end efficiency is then down around 52%).

1000 Watts of panel on a 24 Volt system can generate about 32 Amps peak charging current, which would normally be enough for a 320 Amp hour battery bank. Said bank at 25% DOD would supply (320 Amp hours * 0.25 / 24 Volts) 1920 Watt hours DC. At 50% DOD it would be double that: 3840 Watt hours.

Again these are 'ballpark' calculations used for the basic design; quite a few factors may make your system more or less efficient. For example I am at higher elevation so my panels receive more than the average amount of light and actually run at 82% efficiency on average rather than 77%.

20✭thank you again

ok it begin to be clair for me this 10% charge rate

so since i have a 250Ah of battery,and i use a charge controler that can give me (70A max outpout),and i have a 1000w of panel at 24v and i use an mppt charge controler (assume that is not loss in the system and the power in is equal to the power out) i can have from this 1000w at 24v like 41A(1000/24),so this 40A can go totaly to the battery ,but this is not healthy to the battery .

so for this i schould respect this rule of 10% charge rate ,so if i respect this rule ,i have to design my system to have 10% of 250Ah =25A going to my battery that means i have to design a system that can give me maximum 25A from panel .

and this is depending on battery (flooded cell(10% recomended chareg current) ,or AGM(can take higher current)

is this correct.

32,026adminPretty much... The typical maximum charge rate for a flooded cell battery is around C/8 = 0.125 ~0.13 = 13%

You can go higher rates of charge--Upwards 20-25%. However, with higher rates of charges, it is possible to "over heat" the battery bank. So, many higher end charge controllers have a Remote Battery Temperature Sensor (usually an optional component) that is installed onto the battery bank case (or sometimes bolted to one of the terminals).

The problem is that as lead acid batteries get hot, their charging voltage falls--And the charge controller may try to supply more charging current (and temperature rises more, and battery voltage falls--Possible thermal run away).

In real life, we do have losses... For charging current:

77% = 0.77 = 0.81 solar panel derating * 0.95 charge controller efficiency

So, for a 1,000 Watt array, the typical warm weather/clear day maximum current you would get from an MPPT type charge controller is:

1,000 Watts * 0.77 derating * 1/29 volts charging = 26.6 amps maximum (typical) at least a few times a year around noon

See I am using 29 Volts for battery charging voltage (absorb voltage check point). When the battery bank is less than ~80-90% charged, it will be at less than 29 volts (maybe 24-28 volts)--So, you will get more current in those conditions.

Because of temperature, clarity of day, seasonal elevation of sun, altitude of site, etc. -- These are very rough numbers. You may do better, or you may do a bit worse. Note that if you have a large enough array to hit the charge controller's current limit, the MPPT charge controller will not pass any more than the current limit (safely and reliably).

Note, for PWM type charge controllers the derating works out to be roughly 77%, but the math/reasons behind the derating is different (and PWM charge controllers cannot directly/efficiently limit current, so they have a "hard limit" on array current rating).

-Bill

20✭ok, thank you all for your response

special thanks to "BB" and "Cariboocoot"