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shredderf16 avatar image
shredderf16 asked

Solar Controllers and when BMS Disconnects Battery

I've got a Smart 150/45 Solar controller. My BMS on my battery disconnects every day as the battery approaches full charge (due to a cell overvoltage). This lasts about 5 minutes until the cell voltage drops. This bank is balanced as well as I can get it in the field without taking it offline for a week to balance it. So I don't want to do that until a future time. I haven't put the new Victron controller on yet, but the old other brand controller I have on now stops charging for the rest of the day once the BMS disconnects the first time. The result is at sundown I've already burned through 2 KWH of juice.

My main question is will the Victron be damaged by momentarily being disconnected from the battery while still receiving full solar power? It looks like from other answers no, but I would like to be sure before I put it on the bank. I'm also wondering whether it will reconnect automatically once the BMS allows it to charge the battery.

I'm going to look up the Battery Smart Sense device, is there another device that is suited to keep the cycling down between the BMS and Solar controller?

Thanks,

Jerry Barth

smart solar charging behaviour
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4 Answers
seb71 avatar image
seb71 answered ·

will the Victron be damaged by momentarily being disconnected from the battery while still receiving full solar power?

It could be damaged, so better to avoid this.


You should lower the charging voltage and maybe the charging current, until the BMS manages to bring all cells to closer voltages.


I'm going to look up the Battery Smart Sense device, is there another device that is suited to keep the cycling down between the BMS and Solar controller?

The SmartSolar 150/45 has a Remote Off capability, but unlike the larger models, it needs a special VE.Direct adapter. Maybe you can somehow get a signal from the BMS to also turn off the MPPT using this Remote Off capability.

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jc2010 avatar image
jc2010 answered ·

In these circumstances it is better to get a BMS that can talk to a GX device and tell it to limit output from the MPPT.

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seb71 avatar image seb71 commented ·
He does not mention any GX device.
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jc2010 avatar image jc2010 seb71 commented ·

He doesn't mention he has a special VE.Direct adapter either, but that is beside the point as he states "is there another device that is suited to keep the cycling down between the BMS and Solar controller". Nothing precludes from adding either.

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seb71 avatar image seb71 jc2010 commented ·
I did not say he has a special VE.Direct adapter.
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shredderf16 avatar image
shredderf16 answered ·

Thanks Guys! The perfect thing would be a link to the MPPT that takes input from the Victron battery monitor and cuts off charging at 1% of battery being full. The wild cell voltage (only one cell in the middle of the pack, I think from tinkering it's more about the cell position vs state of charge or cell resistance) only occurs for a couple of minutes at the very end of cycle. Victron engineers, it might be useful to incorparate this kind of link so that we can run a max charge state (say 90%) to prolong the life of the Lifepo4 batteries. Also, according to my Tech Son, Android is designed to prohibit remote access through bluetooth. Since the BMS and all the Victron devices communicate through Bluetooth I need a way to at least monitor (and preferably control) all of these devices remotely so I don't show up to the house with no power because a solar array fuse blew. If I'd had an alert I could have told the BMS to shut down all power going out. I lost one cell last time due to too low a voltage to recover by the time I discovered the situation. The ANT BMS I'm using uses a very small amount of power so by the time it shut completely shut down due to the solar fuse blowing I lost one cell).

Thanks,

Jerry Barth

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seb71 avatar image seb71 commented ·
That way to control the system remotely is a GX device, such as Cerbo GX (and an Internet connection). But basically you also need Victron only components (MPPT, inverter, etc.). Those components are connected with Cerbo GX with cables (VE.Direct, VE.Can, etc.).
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thanar avatar image
thanar answered ·

Why don't you discharge that one cell that's giving you the issues, when the battery is full, and bring it down, along with the others? You don't have to take down the battery to do this, just access the cells and use a light bulb to discharge that one cell a bit.

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