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Todd Wallace avatar image
Todd Wallace asked

SmartSolar MPPT 100/30 + BMV - Voltage spikes during charging

Is there a way to configure a high voltage cutoff the Smart MPPT 100/30 uses to prevent surges from causing charging voltages beyond specs of battery? I recently got a Gel battery and they are sensitive to high voltages. My charger gets voltage/temp from my BMV battery monitor, however sometimes it misses bluetooth voltage update packets, and on intermittent cloudy days, there can be sudden surges in output current, but if the battery is mostly full already, the voltage will jump as high as 14.85 volts before the MPPT finds out and can back the current off to maintain the 14.2v it should be. Is there some kind of protection setting that can prevent this? This was an expensive battery and I dont want to damage it,

MPPT ControllersBMV Battery Monitor
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klim8skeptic avatar image klim8skeptic ♦ commented ·

Have you updated the firmware to v1.42?

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svtti123 answered ·

Use a high accuracy voltmeter with data logging its most likely insignificant and to short of duration to be meaningful and not happening at the battery but at the mppt terminals. I have noticed the same but measured at the battery term terminals its fine.

So measured at mppt you may see that but data logged at battery i have never seen it. Had me concerned also.

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Todd Wallace avatar image Todd Wallace commented ·

Well part of my question involves my MPPT being linked to my Victron battery monitor via their VE.Smart bluetooth. When that is enabled, the MPPT uses the actual battery voltage as measured by the battery monitor (which is pretty accurate) to adjust the charging cycle. That's normally a good thing, as it seems the voltage/temp readings get updated once a second. But sometimes it misses those voltage readings for whatever reason from the bluetooth, and on intermittently cloudy days, 5 seconds without information about the battery voltage can result in spikes. Now granted, it only gets up to 14.85 volts for 3 or 4 seconds before it realizes its too high and backs it off, but since this is a brand new Gel battery, I worry about damaging it as Gel batteries are more sensitive to high voltage (normal charging is 14.2 max). Do you think intermittent bursts of 14.85v volts of 4 or 5 seconds is bad for the battery?

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Mark avatar image
Mark answered ·

Are you able to provide some more information about your setup and the usage conditions to potentially help diagnose?

Such as; battery capacity, PV power connected, charge voltage set-points, charge and load conditions when the issue occurs, if you are using a BMV with temperature sensor, battery temperature reported when the issue occurs, how far away the BMV is from the MPPT & anything else that might be of interest.

The more that I think about it, you may have an intermittent bad connection somewhere. I would recommend to go through every joint and terminal in your system, ensuring that everything is neatly and securely connected.

Even if you had momentary loss of Bluetooth connection for a few seconds it should not cause the behavior you described as it would continue to use existing data for a short period then revert back to working as a stand alone unit (typically resulting in a decreased charge voltage).

It also does not seam realistic for your batteries to increase so much in voltage within just a few seconds, even if the MPPT was operating at full power.

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Todd Wallace avatar image Todd Wallace commented ·

Sure I can give the specifics if it will help. It is a 12 volt 200Ah Gel battery with a spec of 14.2 volts absorption, and 13.5 float. MPPT is configured for 14.2 volts absorption and 6 hours max time limit. I have a temperature sensor installed on the BMV and the voltage compensation set according to battery spec sheet (-24 mV/C). The reported temperature never goes below 24C or above 26C that ive observed so that shouldnt be a factor. The BMV head unit is maybe 10 feet or so from the MPPT Smart 100/30 controller. Also I have tried removing/deleting the network and resyncing. Doesn't really help. I have 3x100 watt 18.9v nominal solar panels connected in series for total of 300 watts output. Load conditions vary alot based on daily usage, but the average load is maybe 3 to 6 amps at any given time. The loads are usually pretty steady though. I have 12v radios and a small inverter connected properly and securely. The BMV is actively sharing both voltage and temp to the MPPT via VE.Smart. The following situation is what causes these momentary spikes:

1) The sun is out. Panels/MPPT are capable of delivering 15 amps or so to the 12v battery

2) The battery is mostly full and partly through absorption phase. Perhaps -15 amp-hours still need to be put in. WIth sun out, battery may be accepting 5 or 6 amps of current (as measured through the BMV)

3) Intermittent cloud cover shows up

Under normal conditions, a cloud shows up, output drops to only 1 or 2 amps total 12v solar output. Voltage drops maybe 13.8 volt range or someting. Sun comes back, and suddenly the panels are delivering full power again. There is a momentary surge of current, and MPPT sees the voltage jump up and compensates. All is well and we are back to 14.2 volts.

The problem is when this occurs, and the MPPT misses a few voltage updates from the BMV at the wrong moment. Clouds cause drop to 13.8v and 2 amp solar output, sun comes back and suddenly 15 amps is going into the battery, but the MPPT doesnt know it yet. Voltage quickly spikes passed 14.2 volts since the battery is almost full and there are only small loads on the system at the time. It gets as high as 14.85 volts or something and then finally sees the BMV voltage and backs it down like normal. It is usually only spiked to 14.85 for 4 or 5 seconds at the most before it gets an update so its not the end of the world. But I'm still concerned about hurting my new battery. Hope this clarifies my question.

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Mark avatar image Mark ♦♦ Todd Wallace commented ·

Thanks for the info, it helps a little - even to rule out certain things.

I'm a little bit suspicious that your battery (which is a decent size) can be increased in voltage so rapidly - regardless of the cause.

So I'm even thinking that it may even be an issue with the BMV wiring/connections somewhere. To rule this out could you possible monitor the battery voltage DIRECTLY at the battery terminals during this event with am independent multi-meter?

Can you also confirm exactly what the PV voltage drops to during these events? (As the MPPT will turn OFF if the PV voltage drops below battery voltage +1v and then needs the PV voltage to increase to battery voltage +5v to turn ON again).

Is your system possibly on VRM? If so could you provide the url.

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