Valence XP Super Thread

Travis said:

If you're looking for more batteries give Glenn a call and be sure to tell him <<<Travis from Hawaii in the Valence Super Thread sent you.>>>
That way they know you are educated and you'll get better service. These guys like selling batteries to the people who know how to take care of them.

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noblesin said:

Hello, I'm interested in purchasing two of the U27-12XP to replace the batteries on my Travel Trailer and hook them up in parallel for a 200AH System. Is the $599 BMS still required for my setup or are there any cheaper alternatives? Do any of the folks here have them in stock to ship to CA? Thank you for any feedback!

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noblesin said:

Hello, I'm interested in purchasing two of the U27-12XP to replace the batteries on my Travel Trailer and hook them up in parallel for a 200AH System. Is the $599 BMS still required for my setup or are there any cheaper alternatives? Do any of the folks here have them in stock to ship to CA? Thank you for any feedback!

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Travis said:

Travel trailers pull power out of the batteries 24/7 and you'll likely end up draining yours to a dangerously low level and ruining them. Because you don't have any batteries in series you can go with the thunderstruck. It will protect from low voltage if you get a contactor to go with it. I can sell you a BMS with contactor programmed for what you need but it'll cost more than the thunderstruck. If you ever find your batteries in freezing conditions & trying to charge that will ruin them and that might be one reason to go with the real BMS instead of the thunderstruck. But I haven't verified the real BMS's ability to protect against charging while freezing and the valence manual doesn't mention it. I hope to have an answer about that soon.

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jeremyjeremy said:

Hi All,

I have 2 of the U27-12XP batteries on the way for my travel trailer.

I do not have a DC powered inverter in this trailer. A/C is only available on shore/generator power. Future upgrades include an EasySolar. I use small 12v plug-in inverters for cell charging etc.

I plan to run the batteries in parallel for the time being since I only have 2x 100w panels on the roof. The charger is a Victron 150/15 currently connected to the DC bus bar.

I've read the whole thread, and it seems like I would be fine with the Thunderstruck BMS and a contactor between the batteries and the RV's DC bus bar. The charger will be moved from the bus bar where it is now, to a spot before the contactor on the battery side. Am I ok to rely on the Victron to not overcharge the batteries?

Will the Victron Battery Protector work with this BMS?

I plan to add more solar/batteries and switch to 24v in the future but this setup seems like it would be fine for now? During winter the batteries will be removed and stored at home so there is no risk of low temp charging.

edit: I just realized I would also have to move the shore power charger and the vehicle charge circuit to the battery side as well, and would need another contactor to prevent those from overcharging the batteries.

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Travis said:

Generally if your chargers Max voltage output is under 14.6 volts then it will not overcharge the battery provided it is properly balanced. If it's not properly balanced then one or two cells would go over voltage when nearing 13.8 volts. So basically as long as you make sure they are completely top balanced then in the future because you have a thunderstruck keeping them balanced you should never have a problem with anyone cell going over 3.8 volts. So you shouldn't really need a contactor between the panels and the charger. relying on a quality charge controller to stop at a certain voltage is very reliable.
I know some people have got the victron system to actually communicate with the valence uBMS but you would be using a thunderstruck. Thunderstruck has plans of more complex communication abilities. Such communications are really unnecessary anyway.
There's a lot of benefits to sticking with 12 volts when you're dealing with an RV and someone with a system in an RV might find themselves having eight or more batteries we're having a very large RV with huge power demands before they are encouraged to graduate to a higher voltage setup.

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Travis said:

Travel trailers pull power out of the batteries 24/7 and you'll likely end up draining yours to a dangerously low level and ruining them. Because you don't have any batteries in series you can go with the thunderstruck. It will protect from low voltage if you get a contactor to go with it. I can sell you a BMS with contactor programmed for what you need but it'll cost more than the thunderstruck. If you ever find your batteries in freezing conditions & trying to charge that will ruin them and that might be one reason to go with the real BMS instead of the thunderstruck. But I haven't verified the real BMS's ability to protect against charging while freezing and the valence manual doesn't mention it. I hope to have an answer about that soon.

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jeremyjeremy said:

Thanks for the quick reply! I'll double-check the shore power charge output and the tow vehicle, but that's a late model truck so I can't imagine it's a problem.

One reason I thought going 24v might be a benefit in the trailer is the lack of voltage sag when various loads are switched on and off. I get that now with the cheapo marine deep cycles, not sure if that would be the same with these XP's. I don't see switching until I move up to a bigger trailer and more batteries though.

I have an somewhat light duty EV conversion project coming up that'll need a better BMS. These batteries seem like a good option for that.

Thanks again for all the info! Great thread.

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GitHub - seb303/Arduino-XP-BMS: A BMS for Valence XP batteries, designed to run on Arduino or similar hardware.

A BMS for Valence XP batteries, designed to run on Arduino or similar hardware. - seb303/Arduino-XP-BMS

github.com

• Keep the Valence internal BMS awake so the intra-module balancing is active.
• Provide a signal to a charge controller to disable charging in case of individual cell over-voltage or over-temperature.
• Provide a signal to a load disconnect relay in case of individual cell under-voltage or over-temperature.
• Provide warning and shutdown status outputs for over-temperature, over-voltage, under-voltage and communication error.
• Provide basic event logging (can be accessed via a laptop).
• Have a mode for long term storage / not in use, where it will let the batteries rest at a lower SOC.

seb303 said:

Been loving this thread, so much useful information about the XP batteries

The guy I bought my batteries from said they only needed 5V on the RS485 connector to keep the internal BMS alive. As pointed out here, this isn't actually the case. Since I only have 2 parallel batteries in a campervan it seemed overkill to spend a lot of money on a BMS, and I didn't want to keep plugging in a laptop regularly, so ended up coding my own solution which runs on £20 hardware...

GitHub - seb303/Arduino-XP-BMS: A BMS for Valence XP batteries, designed to run on Arduino or similar hardware.

A BMS for Valence XP batteries, designed to run on Arduino or similar hardware. - seb303/Arduino-XP-BMS

github.com

My goals with this were to:

• Keep the Valence internal BMS awake so the intra-module balancing is active.
• Provide a signal to a charge controller to disable charging in case of individual cell over-voltage or over-temperature.
• Provide a signal to a load disconnect relay in case of individual cell under-voltage or over-temperature.
• Provide warning and shutdown status outputs for over-temperature, over-voltage, under-voltage and communication error.
• Provide basic event logging (can be accessed via a laptop).
• Have a mode for long term storage / not in use, where it will let the batteries rest at a lower SOC.

If anyone needs some help to get it up and running, feel free to give me a shout.

Also, I am interested in some feedback on my choice of thresholds for warning and shutdown. The values used by the Valance U-BMS (according to the Valence User Manual) seem quite extreme, I guess spec'ed for maximum battery capacity, fast charging and heavy usage. I would rather aim for maximum battery life. These are the values I settled on:

Over voltage warning: 3.6V (Valence U-BMS value = 3.9V)
Over voltage shutdown: 3.8V (Valence U-BMS value = 4.0V)
Hysteresis: 0.2V (i.e. voltage must drop by this amount before the warning or shutdown is cancelled.

Under voltage warning: 3.0V (Valence U-BMS value = 2.8V)
Under voltage shutdown: 2.7V (Valence U-BMS value = 2.3V)
Hysteresis: 0.2V

Over temperature warning: 55C (Valence U-BMS value = 60C)
Over temperature shutdown: 60C (Valence U-BMS value = 65C)
Hysteresis: 2C

Long term storage mode allows a battery to drop to 50% SOC (which will probably never happen as they seem to drop so slowly), then charge back up to 80%. (SOC according to the internal SOC value read from the batteries.)

I have in any case set my charge controller to quite a conservative voltage in the first place: 13.9V, with 13.5V float. The batteries seemed to reach 100% SOC ok,. I'm not sure if I would gain much more capacity by charging to a higher voltage? I only have 320W of solar to charge 276Ah of batteries, so charging doesn't need to happen very fast (although I guess this isn't so true when charging from the vehicle while driving - in this case the charge controller can put out 700W / 63A).

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Travis said:

Id make the under voltage shutdown 2.75 or even 2.8v. and it kind of depends on whether or not you have any loads at all connected to the batteries or how long you will be absent. There's not much power left in these batteries below 12 volts anyway. and if it has a low voltage shutdown and you are gone for a few months you don't want it going critically under because of regular self-discharge. And certainly wire it up so that absolutely NOTHING is connected to the batteries after the BMS has shut it down.

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Travis said:

Id make the under voltage shutdown 2.75 or even 2.8v. and it kind of depends on whether or not you have any loads at all connected to the batteries or how long you will be absent. There's not much power left in these batteries below 12 volts anyway. and if it has a low voltage shutdown and you are gone for a few months you don't want it going critically under because of regular self-discharge. And certainly wire it up so that absolutely NOTHING is connected to the batteries after the BMS has shut it down.

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jeremyjeremy said:

I may have missed it in the thread. If the BMS is powered from the batteries, and the BMS disconnects the loads via contactor, wouldn't the BMS still draw power from the batteries? Does it need to be on an independent battery that is also disconnected via contactor when it trips so it can stay powered waiting for the voltage to come back up?

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Travis said:

I would change the over voltage warning to at least 3.7. it all depends because on the initial balance when you get your batteries. it'll be hard to keep it under 3.8 the first time you balance but after it's all balanced and if you balance often enough 3.6 or 3.7 would both be acceptable.

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Travis said:

Id make the under voltage shutdown 2.75 or even 2.8v. and it kind of depends on whether or not you have any loads at all connected to the batteries or how long you will be absent. There's not much power left in these batteries below 12 volts anyway. and if it has a low voltage shutdown and you are gone for a few months you don't want it going critically under because of regular self-discharge. And certainly wire it up so that absolutely NOTHING is connected to the batteries after the BMS has shut it down.

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seb303 said:

Thanks for the advice. I'll change my shutdown threshold to 3.9V, as I wouldn't want it to shut down the charger during the process of cell balancing. The warning is only an indicator, so I'll probably leave at 3.6V for now, just out of interest to see whether it hits this level with normal (moderate) charging.

My charge controller has 4 settings for LiFePO4, the highest being 14.6V, so in theory the cells, once balanced, shouldn't be pushed much beyond about 3.65V. I just want to cover the situation where there may be a weak cell and avoid the others going dangerously over voltage as a result.

On the subject of an initial balance: do you consider it necessary to do this? Currently I have my charge controller set at 13.9V (13.5V float), and with the batteries not really being used, they are sitting at 100% SOC. I notice that if I turn up the charge voltage then the cell voltages almost immediately go out of balance, which suggests to me that there is some remaining uncharged capacity in some of the cells. But does this actually matter?

They are 2nd hand batteries, so they must have been balanced at some point, although have not had much use: Charge/Discharge Cycle Cnt = 2, WH Dschg = 535/540 KWH respectively.

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jeremyjeremy said:

I may have missed it in the thread. If the BMS is powered from the batteries, and the BMS disconnects the loads via contactor, wouldn't the BMS still draw power from the batteries? Does it need to be on an independent battery that is also disconnected via contactor when it trips so it can stay powered waiting for the voltage to come back up?

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