Valence U27-12XP 2S 3P BMS?

[me72]

Anyone know how to safely use six Valence U27-12XP in 2S 3P (24v nom)? They all have internal BMS so evidently none of them can ever go overcharge or undercharge unless a BMS or hardware failure happens.

I'm assuming that somehow connecting the existing Valence BMS cables to each other from battery to battery in some arrangement does nothing without the Valence BMS system.

Do I need to go out and find the full Valance BMS system to run safely in 2S 3P?

Would running a Victron Battery Balancer between the parallel sides and to the midpoint be sufficient?

What about paralleling all the midpoints? The Victron Balancer calls for paralleling the mid points but I have heard some say they don't like doing that and to just run separate strings as far as the mid point goes.

To try to stay in range and to try to increase cycle life some;
I set my inverter to cut off at 25 volts. (~14% SoC)
I set my charger absorption charge at 28 volts and storage charge at 26.6 volts. (~90% SoC)

This on 2S. I haven't tried 2S 3P yet.

Here is a pic.


Thanks in advance,
-Me72

 

[mvhw]

I'm looking into a similar 24v configuration but with more capacity, say 2s7p for around 25kW.

I see that Muller Industries USA offers a BMS but I'm not sure how to configure it for the right mix of series/parallel modules.

Battery Management System MIUSA-BMSLV

MIUSA-BMSLV Battery Management Systems are designed to enable multiple system implementation options and advanced command and control ability. MIUSA-BMSLV is compatible with U27-12XP battery modules Features - Monitoring, temperature, voltage, current, SOC status - MIUSA-BMSLV can manage...

www.mullerindustriesusa.com

This nice YouTube video also goes over the pieces and parts of a similar but larger 48v system recently installed on a motor yacht...

-Steve

 

[villagepowerdesign]

Hey there Me72 - I am considering buying 6 U27-12XPs for the same 2S 3P 24V config. I'd love to hear what you learned? Same questions as everyone has - do I need to worry about external BMS and if so what exactly? Were you able to get all your questions above answered anywhere? It would save me a lot of research if you could share what you found. Thanks!!! Jeff

 

[mvhw]

Hey there Me72 - I am considering buying 6 U27-12XPs for the same 2S 3P 24V config. I'd love to hear what you learned? Same questions as everyone has - do I need to worry about external BMS and if so what exactly? Were you able to get all your questions above answered anywhere? It would save me a lot of research if you could share what you found. Thanks!!! Jeff

I’m still in early stages of purchase and research myself, but here are a few bits of random info I’ve learned...

- Muller Industries USA website is down for the Holidays while they refresh the site and improve things, according to a rep from their company. But they are still very much in business and provide a BMS that should work for these types of 24v and 48v banks

- The Muller BMS talks to your entire bank of batteries across the comms cables, and I believe it provides the necessary “wake up” voltage and commands overs the comms cables to force the batteries to internally balance the cells, while also telling individual batteries to turn on their resistors to allow other batteries in your bank with a slightly lower state of charge (SOC) to charge and catch up. I believe that without the “wake up” voltage/signals, the Valence XPs do NOT perform internal cell balancing. So these two functions of the Muller BMS are critical to long-term health of your bank

 

[villagepowerdesign]

Hey Thanks for the reply! Great info - so I'm curious if the setup with the Muller needs contactors to be installed as well. The XP spec sheet refers to them with the Valence external BMS and I've seen them on many high voltage setups on u-tube - not sure if needed for 2s 3p at 24V. I've attached the spec sheet in case you didn't have - 2nd page contactor reference. . . I'll see if I can call Muller tomorrow and get some answers that I'll be glad to share.

 

[villagepowerdesign]

And does the Muller have a low temperature disconnect?

 

[mvhw]

And does the Muller have a low temperature disconnect?

Hey, thanks for that attachment. I’ll have to review it. I got as far with Muller folks as discussing contactors needed for their BMS solution, yes. They were going to recommend a particular brand/model of contractor for me for my 24v 2s8p bank of batteries, based on anticipated amp draw. But I think they went on Holiday break before I could get the recommendation from them on contactors.

My application is a boat with an AC electrical system that runs on 2 x 50A shore power cables, and my battery bank and inverter are intended to stand in while at anchor.

I’m unsure about the low temp disconnect feature.

Very happy to compare notes and share research. Thanks.

 

[mvhw]

Hey, thanks for that attachment. I’ll have to review it. I got as far with Muller folks as discussing contactors needed for their BMS solution, yes. They were going to recommend a particular brand/model of contractor for me for my 24v 2s8p bank of batteries, based on anticipated amp draw. But I think they went on Holiday break before I could get the recommendation from them on contactors.

My application is a boat with an AC electrical system that runs on 2 x 50A shore power cables, and my battery bank and inverter are intended to stand in while at anchor.

I’m unsure about the low temp disconnect feature.

Very happy to compare notes and share research. Thanks.

So it looks like you only need contactors with the Muller BMS if: (1) You do strictly AC loads via an inverter and you can’t or won’t handle under voltage with your inverter itself, say, a Victron, or (2) I *think* if you have DC loads that you want the Muller BMS to disconnect upon under voltage condition (whatever low SOC you set) you’d want the Muller BMS to operate the contactor(s)

 

[ericgrand]

Anyone know how to safely use six Valence U27-12XP in 2S 3P (24v nom)? They all have internal BMS so evidently none of them can ever go overcharge or undercharge unless a BMS or hardware failure happens.

Be careful, internal BMS of each battery does not prevent anything, unless it is connected to a Valence BMS properly setup. Internal BMS only provide light balancing of the internal cells if connected to an an RS485 device.
If not plugged, the internal BMS do nothing...
There is no FET or relay inside the battery to switch off the power.
So you can easily over charge or discharge the battery...
Take care also that battery stored for a long time may present an internal inbalance of the cells, which will reaquires a very long time to balance again...

 

[Travis]

I can hook you up with a Valence BMS configured for your needs.

 

[RLloyd]

I can hook you up with a Valence BMS configured for your needs.

I have 2 of these batteries that I want to put in series. Do you know what I can do to install an external bms? I would think I could just install a common bms and attach it to the balance wires in the valence. I have not seen what is behind the valence cover yet.

 

[RLloyd]

I think I might use thunderstruck, Has anyone had good experience with that type? I realize that I will need to balance battery to battery from time to time as the thunderstruck will not do this.

 

[ericgrand]

If you don't mind voiding warranty, you can open the cover and remove Valence BMS borad. You have a plug with 5 wores connected to each cell. You can easily connect any BMS you want!

 

[RLloyd]

Is that 4+ and 1-

 

[Travis]

I think I might use thunderstruck, Has anyone had good experience with that type? I realize that I will need to balance battery to battery from time to time as the thunderstruck will not do this.

In your case it would be best to use a thunderstruck. A lot easier than opening the cover and messing with all the wires. You need to balance The 2 that are in series Anytime you want to charge over 95%. It's best to use one of these Chinese balancers In addition to the thunderstruck but warning they will draw your battery's down if you let them sit So remember anytime you let them sit for a long time disconnect the balancer 1st. https://www.amazon.com/dp/B07L8XKZ71/ref=cm_sw_em_r_mt_dp_5DBVFNJZ9T01WDKXVH89?_encoding=UTF8&psc=1

 

[RLloyd]

I was concerned that the 2 valence batteries may have been discharged to a critical low voltage but I think a may have worried for no reason. The valence program shows low voltage history of a cell at 2.3 volts. is that normal for a reading in the valence history log?

 

[ericgrand]

Is that 4+ and 1-

Not exactly...as the positive of a cell is the negative of the next one...
The wires are connected like this:
-negative of battery which is also negative of cell 1
-positive cell 1which is also negative cell 2
-positive cell2 which is also negative cell 3
-positive cell 3which is also negative cell 4
-positive cell 4 which is also positive of battery

Not sure if it is counted this way or the opposite, but this is the general idea...

 

[Ryantech]

So what exactly does thunderstruck do and can't do that the internal "bms" can't do balancing wise?

 

[Travis]

So what exactly does thunderstruck do and can't do that the internal "bms" can't do balancing wise?

It can control a relay to disconnect the battery's when necessary. Like one of the main reasons because of voltage to high or low at the cell level.

 

[Ryantech]

It can control a relay to disconnect the battery's when necessary. Like one of the main reasons because of voltage to high or low at the cell level.

It is able to send the balance signal to all of the slaves correct? That is my only reason for buying one a few days ago. High and low voltage cutoffs are a secondary thought as they'll be sitting most of the year and when used 3 batteries will see at most 250 amps. My monitoring set up will alert me with low temps, high temps, and high voltage.

Only reason I say secondary is I'm not having a contactor engaged year round. Kinda screams failure point. I've been looking for a 400 to 500 amp normally closed contactor but no success yet. The contactor will be run off of an isolated low AH lifepo4 battery. More complex yes but the failure likleyhood with a NC contactor would be so unlikely.