usinworld avatar image
usinworld asked

BlueSolar 75/15 load voltage swings with >1amp load

Hi All

Been in contact with the place I bought my BlueSolar 75/15 and Bluetooth dongle and want to hear if someone experienced similar

Its installed in a 4x4 with 100+80w solar panels in series (lots of cloudy days in scotland) It feeds a 12v 90ah deep.cycle battery which mainly runs LED lights and a fridge. Battery is connected to started battery via a Victron Cyrix battery combiner.

Been working well for 2 years and then other day noticed when turning rear LED worklight an approx 1amp load the light output is low and constantly fluctuating. Measured load terminals on the Charge controller and it swings from 5 to 11 volts. The battery voltage is stable at 12.50v at same time. Day was sunny and 34v from the panels and charging state float. When turning on more lights the load voltage drops to 0v and at somepoint it came up with battery overvoltage 23v alarm. Switched loads off and voltage dropped slowly to approx 12v. When disconnecting solar panels and in evenings the unit turns fully off, no light in diodes and not visible via bluetooth

When the engine is running and battery combiner is active both batteries are 14.2 volts. Battery terminal of charge controller is stable at 14.2v Thou when load above 1Amp is applied the same voltage fluctuation in the victron app occurs and lights goes dim and bright randomly

Tried disconnecting the main battery and no change in behaviour. Tried another LED light with approx 1.5amp load and same story.

Is it a faulty unit or is there something else that needs to be looked at? The battery overvoltage error really puzzles me as no changes to wiring and then appears normal again.



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1 Answer
JohnC avatar image
JohnC answered ·

Hi Us. The LOAD terminals are really intended for very simple resistive loads. Some people can get away with it, others not. And they don't even exist on Victron's larger mppts.

Try running your loads direct from the batts, and if you wish to retain the 'batt protection' feature you could do that through a relay driven from the LOAD terminals.

You *may* be able to get away with a light circuit off the load terminals, and that would give you a visual warning of batt depletion.

See how you go..

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usinworld avatar image usinworld commented ·

Thanks for the reply JohnC

I see what your saying re light circuit from the load terminals as per design. Would have been usefull if such restriction on use of load terminal was described in manual.

Thou surely the internal fuse of 15Amp should have prevented any overload of the unit. While in use I never seen a load measured by the controller above 5Amps

My question re why the unit swithes off during nighttime or with disconnected solar input still stands. Its a fault is just developed and the battery voltage is stable, shouldn't be affected by the LOAD as nothing is on?

The question that I'll try to find out with more measurements today is if the battery terminal/connection on the unit is dodgy and only allows a small amount of current or none. Thou unit software and direct measurememt with a DVM om the battery terminals shows the voltage thou as soon as any load not matched by the solar output occurs the unit load voltage starts fluctuating. This would explain the off a night/disconnected solar switch off of unit

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markvanloon avatar image markvanloon commented ·

Hi John, Indeed, when I connect a simple led lamp (0,3 A) no problem. Connecting a 12>220 inverter, the load is switching On & Off and back. Even without any load at the inverter. So the load is just for simple circuits? Max ampere via load =... ?

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wkirby avatar image wkirby ♦♦ markvanloon commented ·

I wonder if the fuse in the MPPT is OK. It may look OK, but is not making good connection. At least removing it and replacing it again may help, but if you can replace it with a new one that would rule that problem out.

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JohnC avatar image JohnC ♦ markvanloon commented ·

Hi Mark. Please note that Victron say NOT to run inverters from the load terminals. I'd have trouble finding a link to that - trust me? :).

The reason wasn't specified, but I strongly suspect that it's because of the current surge to fill the caps'n'coils within, overloading the protective function in the mppt.

To qualify that for yourself you could touch your inverter input terminals over a battery post and probably see a spark. Some makers (well I've seen one) will warn of that. I don't think Victron warn, but if you try that with (say) a Multi 48/5000, you *will* remember the experience. And never do it again..

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markvanloon avatar image markvanloon JohnC ♦ commented ·

Thanks guys. I found also this:

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