Basic amps question

[SupraSPL]

Why is the charge rate .63c on these batteries normally .5c is what I thought was common and for longer life .2 to .3c was better?

They are 12V 230Ah so 63 amps is .27C.

The 100 amp figure we were talking about is the BMS limit.

 

[mikefitz]

1. It is possible to over feed my batteries based on the charge controller amp rating.

According to the battery manual if the charge current exceeds 100 amps the internal control circuits drop the charge current to 20 amps.
The MPPT chargers will have charge profiles and terminate charge based on voltage and/ or tail current.
Thus its possible to charge over the 63 amp limit but the charge will not allowed to exceed 100 amps and will be terminated by charger settings.

 

[rodrick]

I thought they were 48 volt 100 amp hour rack batteries

 

[Bluedog225]

Yes. Four 48 volt, 100 amp SOK rack batteries.

 

[SupraSPL]

I thought they were 48 volt 100 amp hour rack batteries

Oops wrong thread. In that case the 63 amp figure is kind of arbitrary.

 

[rodrick]

Oops wrong thread

Well you had me confused as hell I was trying to figure out where the 2:30 come from

 

[SupraSPL]

According to the battery manual if the charge current exceeds 100 amps the internal control circuits drop the charge current to 20 amps.

From manual:​

​

Charge Current Limiter​

The built in charge limiting circuit is a part of the battery management system (BMS). The charge limiting circuit prevents excessive charge current from causing a complete shutdown of the battery module, by using active electronics to reduce the incoming charge current to a safe level. The charge limiting circuit is automatically activated when charge current exceeds 100A. When active, the charge limiting circuit reduces the charge current to 20 amps and stays active until the current falls below 20A, at which point the limiter automatically deactivates.

The charge limiting circuit is truly revolutionary, as most competing batteries will block all charging when the over-current threshold has been reached

Awesome feature

 

[Pi Curio]

Good morning,

I’m getting to the stage that I need to build out my solar array and had a really basic question.

Victron system with SOK 48 volt rack batteries.

I’ve got a variety of small-medium MPPT controllers and may get a couple of larger controllers.

I vaguely understand over-paneling and the potential for clipping. And I understand temperature compensated voltage limitations.

On a quality SCC such as Victron, you can over-panel as much you want as long you respect the SCC's Voc and Isc ratings.

With an emphasis on taking care that the PV Voc during low temperatures in your area doesn't get above the SCC's Voc rating.

At the same time, over-paneling can be a very useful tool for achieving a prolonged period of the SCC's peak production during the day, and not just for compensating up to 30% Delta between the STC and the real-world panel performance.

What I don’t quite get yet is the significance of putting too many amps on the bus bar that feeds the batteries.

That is, the SOK battery charging limit is 100 amps. What happens if there are three (or more) 50 amp MPPT controllers all putting full power onto the bus bar with a single battery?

If it gets above the battery BMS rating the battery will cut off, the BMS is there to protect the cells and the wires of the battery.

The battery is a load, the SCC can only provide the power the load requires.

For example, if a 48V 100Ah battery is full, you could have 500A SCC with enough PV ready to go full blast but your battery would not see a single A going in.

Since there are 4 SOK batteries in parallel, does that increase the charge capacity to 400 amps?

There's also a question if the BMS can run at 100A continuously on individual batteries, but for easier understanding, Yes. That's how it works. As long the manufacturer specifications say up to 1C charging.

But I still have the same question, what if more amps are available?

Do the batteries self limit their input?

What’s the electrical principal here?

Thanks

Batteries take as much as you can give them within their BMS max continuous rating depending on their SOC.

Hope it helps

 

[SupraSPL]

The battery is a load, the SCC can only provide the power the load requires.

For example, if a 48V 100Ah battery is full, you could have 500A SCC with enough PV ready to go full blast but your battery would not see a single A going in.

But before the SCC cuts of at it's voltage limit, that 500A would go into the battery at 5C, triggering the 100A BMS protection.

Normally that's not a problem because with a charge that big coming in, there's usually an equally large battery to take it in.

 

[Bluedog225]

The battery is a load, the SCC can only provide the power the load requires.

For example, if a 48V 100Ah battery is full, you could have 500A SCC with enough PV ready to go full blast but your battery would not see a single A going in.

A water bottle can only take the amount of water it can store. That's the simplest way I can think of how to make it a bit more tangible.

Hope it helps

Thanks. I thought if you kept charging a battery, you could cook it. But for the protection of the mppt and/or bms

 

[Pi Curio]

But before the SCC cuts of at it's voltage limit, that 500A would go into the battery at 5C, triggering the 100A BMS protection.

Normally that's not a problem because with a charge that big coming in, there's usually an equally large battery to take it in.

You are absolutely correct, thanks for chiming in!

Past midnight here, and my brain just went poof on that one

@Bluedog225


Edited the post.

 

[Mattb4]

From manual:​

​

Charge Current Limiter​

The built in charge limiting circuit is a part of the battery management system (BMS). The charge limiting circuit prevents excessive charge current from causing a complete shutdown of the battery module, by using active electronics to reduce the incoming charge current to a safe level. The charge limiting circuit is automatically activated when charge current exceeds 100A. When active, the charge limiting circuit reduces the charge current to 20 amps and stays active until the current falls below 20A, at which point the limiter automatically deactivates.

The charge limiting circuit is truly revolutionary, as most competing batteries will block all charging when the over-current threshold has been reached

Awesome feature

Thanks for that. Much better and politer response than the rather rude one earlier (Not from you but another poster). Not having manuals for every BMS in front of me I did not know about the 20a charge limiting of this one.