bushbloke avatar image
bushbloke asked

2 Smart Controllers 100/30 - 1 being limited.

I have 2x 250 watt panels wired in series going into a 100/30 controller - this connects to a battery bank consisting of 2 x 12 volt 140ah batteries.

I have a 2nd 100/30 controller with 2 more panels exactly the same...... both seem fine individually, and work well.


as soon as I connect both to the battery bank, one controller drops from its normal wattage to around 70-80 watts. (I also notice while the volts stay the same, the Amps also drop way down to around 0.5-0.8)

Why does this happen ?

is it normal ?

thanks for your help.

victron products
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3 Answers
ejrossouw avatar image
ejrossouw answered ·

@BushBloke If you do a quick search, you will find the topic has been covered before in the forum. While it will work, these units don't sync to each other, therefore if the the second unit reads a higher voltage for example at the battery terminal due the impact of the first charger, it will adjust accordingly and lower it's output. Look at the new Ve.Can range which offers synchronised charging.

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Martin avatar image Martin commented ·

This answer describes exactly what I feared before I bought two controllers - that is the output voltage from the controllers would interfere with each other. I asked Victron directly who passed me on to a Victron supplier who told me that two separate controllers was a better option because one of my panels points in a different direction to the other. I think I should has stuck to one big controller rather than two smaller ones.

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klim8skeptic avatar image klim8skeptic ♦ Martin commented ·

You have not said what states the charge controllers were in.

If it was absorb or float, one (or both) mppt would normally reduce output to keep the batts at the target voltage.

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Martin avatar image Martin klim8skeptic ♦ commented ·

Both chargers happily produce bulk charge together but one always switches to absorbtion before the other and then to float way before the other. I can understand that not all the available amps are needed in absorbtion and float but when they are in two different states the voltage at the battery appears to be in between the two states - that is: neither absorbtion or float. Surely that's not right!

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ejrossouw avatar image ejrossouw Martin commented ·

@martin For such a relatively small system I'd simply have connected the two strings in parallel to reduce shading impact, but understand their logic although question if the the overall gain is worthy the investment.

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bushbloke avatar image
bushbloke answered ·

@ejrossouw Thanks for your answer.

As I have an almost identical system functioning perfectly, I can only assume one of the new 100/30 controllers must not be from the Ve.Can range.

As they all look identical, and are running the same firmware, Is there a way I can tell which one is not a Ve.Can ?

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JohnC avatar image JohnC ♦ commented ·

There are no VE.Can 100/30 mppt's. Only some /70 and /85's. And they'll have a CAN port.

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bushbloke avatar image bushbloke JohnC ♦ commented ·


thanks, but now I'm even more confused. Why do 2 work perfectly together and the other 2 not ?

the only diference I can see, is one has 5x 12v x 135ah batteries, and the other has 2x 12v 140ah batteries.

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @BushBloke

You don't provide any information about voltage etc. so I'll be guessing:

-target voltage is reached for the battery (absorption voltage), so only one controller is needed to maintain this voltage.

Try putting a load on the system, to drop the voltage, and both mppt's should start to produce (if correctly configured)

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bushbloke avatar image bushbloke commented ·

HI @Daniël Boekel (Victron Energy Staff)

Thanks for your help..

I have been monitoring and this happens also in Bulk mode, but I think when the battery levels are high.

Voltages ... 2 x 12volt x 140ah batteries

2 x 100/30 Bluetooth smart controllers, each with 2 x (250 W pmax, 37.5V Voc, 8.74 A Isc Wired in Series)

currently running water pump drawing 6-8 amp 24/7

I will add a 2nd pump when this system works correctly.

this is a 12 Volt system

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JohnC avatar image JohnC ♦ bushbloke commented ·

Hi BB. Your system may well be working fine. Daniel has suggested a test method, and another would be to switch off the pv of the mppt that's doing all the work. Then see if the 'lazy' one picks up the slack. If it does, all is well.

I'd perhaps be more concerned about that 2nd pump and reconsider if there's enough batt capacity to operate both through a long 'solar night' in winter. If you want the batts to last..

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