question

robertfry avatar image

mppt panel and battery setting

help please :)

My solar panels are only producing 16amp at peak

I've left the charge setting at max on the battery tab of MPPT setting (70amp)

but the battery info at bottom says charging at 70amp.

how can the battery be charging at greater than panels are producing.

Mppt is red hot and alarm buzzer on multiplus for over temperature

robert



MPPT - Solar Charge Controller
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ok thanks @WKirby , @DafyddHirst


now understanding the kw, v, Amp and battery current a bit more than before, i guess i asked the wrong question.

the MPPT 150/70 is getting too hot to touch on hot days, and the alarm is sounding overheat on the multiplus.

how hot is it safe to run the MPPT. when i restrict the charging current to 40amp on mppt / battery settings tab, the MPPT is less hot, but still quite hot.

is this setting irrelevant and i should change it back to the max 70AMP charging current to allow max amps when the solar panels produce enough, or is it causing the overheating of the MPPT.

if so, is there a rule of thumb to say only set the max charge current to x %age of the max MPPT, in this case 70amp mppt x say 90% so set at 63 amp max charging current?


2 Answers
wkirby avatar image
wkirby answered ·

That is the beauty of MPPT controllers, they convert the power in to the output.
You can't think exclusively about the current becuase that is only half of the equasion. Voltage is the other half of the equasion. The product of these two ammounts to power in Watts.

You did nt mention anything about your array Voltage or power or your battery Voltage, so I'll need to make some assumptions in order to explain. I'm going to assume your battery Voltage is 12V.
I asume your controller is a MPPT 150/70?

So with a 12V battery charging at 70A, the battery is charging at 840W.
If your array current is 16A, then your array Voltage must be about 52V, because the array is producing around about 840W to charge the battery with same amount of power excluding conversion losses.

the 150/70 has an efficiency of about 98%, so 2% is lost as heat.
2% of 840W is about 17W of heat to be dissipated at 12V system Voltage. More energy will be lost as heat if the system Voltage is 24V or 48V.

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@wkirby


wkirby


sorry, hadnt realised i needed to offer more info.

at 16 amp max, the panels are around 125v, 2.3 kw max

24v system using 2 rolls 5000 series batteries, 479AH

sorry MPPT is 150/70 yes.

its overcast today and for the next week. otherwise i would screenshot the mppt settings showing the battery current at 70amp and the solar current at 16A.

might be being stupid, sorry if i am, but why does it show such high amp on the battery current when the panels are only producing much lower mppt-scrren-shot-2507.jpg

So 125V@16A = 2KW

2KW @24V = 83A

Hence you are maxing out your MPPT


dafyddhirst avatar image
dafyddhirst answered ·

Your panels are producing 16A at Voltage X which is not your battery voltage.

Assuming you have a solar voltage of 200V


16A @ 200V = 3200 W so if your system voltage is 24V the current would be 133 A


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wow, thanks for that. @dafyddhirst

so today i'm 130v @ 10amps =1.3kw. / 24v = 54 amps going into battery.

by limiting the charge amount down from max at 70amps, to say 40amps, will that stop the unit getting so hot when i'm over producing on the solar panels. i dont want to remove panels from the setup as on days like today its working fine, otherwise would lose the amount of electric generated