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REC and WS500 User Forum

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Regarding CAN bus regulated charging.

When running CAN bus regulated charging the A-BMS starts to reduce the max-discharge allowed in the system when the first cell reaches "Balance voltage Start". When running solar this runs smooth and gradually the current will lower until its 1.1A and then to 0A.  But when charging high currents this phase leads to oscillating current.

Lets say you are charging an 12V system with 300A or even 400A and the BMS suddenly reduces max current to 50A or even 10A.

Then voltage will drop, and BMS goes back to 400A. And so it goes on for some time.

This is not unique for WS500, it only does what it is told by the BMS. I have seen this in other solutions where charging sources are large compared to the battery.

What I would like is an more smooth volt/current transaction from bulk to float.

Any thoughts on this?

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Trond,

This makes sense, when you are dealing with large charge parameters the PID can get a little twitchy.  It sounds like you may need to increase your Proportional and reduce your Integral and Derivative for your application and this would likely require a firmware update.  By way of this reply I have linked you to Al at Wakespeed to see if he has any ideas for you.

Rick OGSS

@al-thomason

I have seen this before while working with BMS manufactures in proofing reliable Alternator based charging systems; the 'Twitchiness' I call it seems not much of an issue with pure electronic charging sources (Solar, AC chargers, etc); but toss in the inductive / mechanical nature of Alternators - and it results in the behavior you noted. I am also noting your comment of seeing this with other (non alternator?) high power charging sources - interesting.

We have worked with BMS manufactures on this in some cases, and the need is for the BMS to be more paced with its changes.  To allow time for the alternator to fully respond.

I do not know much about the 'A-BMS', though seem to recall hearing of it.  Trying to google it was pointless, as all I could find was articles about "A BMS"  as in "A BMS is a nice thing..."  And yes, the WS500 does respond to these changes, even if fast paced, as we dearly want to avoid tripping a BMS in a disconnect, perhaps due to battery current exceeding requested limit.

BTW, you have touched upon some of the work we do when 'proofing' BMS's - not just that it works, but what happens at EOC, what happens in Warning and Alarm phases.  What happens when loads are added and removed.  All critical to a well preforming, safe and reliable system design.

-al-

 

 

 

Hello Trond,

Can you post your settings from the REC ABMS?

How big is your battery bank?

Maybe I have some suggestions if you give more information.

For example it could be that your balance start is set to low.

ONE practical example I notice with high current alternators is you can not set the charge Bulk voltage to low.

Many users say if you charge lifepo4 only to 13.9V/or 14V  they are full when 13.9V is reached. My testing shows this statement is true if charge with LOW amps.  If charging with high amps, in my test 120amp, I need to set 14.2V.  Than when 14.2 V is reached, amps will quickly go down, what means the batteries are full.

With high amps, always the voltage goes down, if the charge is removed. I see this with any other charge source, not only with alternators.

You could try to do a test, make start balance 3.55,  end balance 3.6

 

With the WS500 and the REC ABMS you have 2 possibilities.

-1  the REC gives the charge instructions, which are different as the internal charge profile from the WS500 themself.

-2  use the internal charge profile from the WS500. Disconnect the Can-bus for a test. Set WS500 to lifepo4 profile.  The internal charge algorithm from the WS500 has plenty off possibilities to fine tune your favorite charge profile.

You can use bulk charge up to 13.9 or 14V with full 300 amps, and then the last bit off charge with lower amps, like 50amps. Look at overcharge $CPO: in the manual. It is all programmable.

With 2, you miss the nice feature from the low amps when balancing start. But probably you have solar in the system as well and the final balancing will be done through low amps from the solar.  AND probably if you have good quality cells, your cells don't need any balancing.

With 2 you can wire the ""stopcharge"" relay from the bms to the ""feature in"" from the WS500, this to disconnect the alternator from charge if one cell is too high.  With feature in you can tell the regulator to go to float.

In this float function, alternator will still deliver all  amps for the load, but will not charge the battery.

Let me know off this is usefully

Ben

 

 

 

 

A quick follow up,  we have verified this behaviors with one of our Beta testers and I have an Email out to REC -- REC and Wakespeed to work to improve the EOC handling.

 

And noting also, did not make the connection above of A-BMS to the ABMS from REC, sorry : - )

 

-al-

 

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