Valence U27-12XP 24v - Starter question

[SlowCredit]

Came across 2 Valence U27-12XP batteries relatively cheap for my travel trailer project. Would like to use them in series. Spent the weekend looking through all the various threads and still not sure on best way forward for a BMS solution for the 2 batteries. The Thuderstruck seems pricey for just 2 batteries - but if it's plug/play maybe worth it?

Looking for advice/opinions/options on what I should buy/build/order today to balance these 2 batteries (Preferably options that are in-stock from US sellers).

Made an rs-485 adapter and downloaded the valence software, so I can see the battery info for both batteries.

Many thanks!

Slow

 

[Samsonite801]

It seems the solution of a Thunderstruck is just to have a master BMS (as the batteries themselves have the slave BMSs, like the master is optional?).. It seems like on the 2s they shouldn't drift off balance if you top balance the pair in parallel prior to hooking them up in series.

This guy seems to give some info about the Thunderstruck, indicating that even with it, you still need a balancing solution to go between your 2s modules:

Muller Industries - BMS for Valence U27-12XP

FYI, new product on market, a BMS for the Valence U27-12XP batteries Much less cost that Valence (hard to find) units, can program yourself easily. Tradeoffs, less overall features, but will probably handle 80% of users out there. https://www.thunderstruck-ev.com/valence-battery-bms.html Many...

diysolarforum.com

Or you could monitor them with your laptop to see if they ever did drift, and add in a master BMS later if you needed to.

The question I'm not clear about, it seems on that thread they might be indicating that the internal cell balancing feature (within a battery module) is not activated without either a master BMS connected or a laptop connected to the Valence com port and app running? Maybe it needs the master for that feature to work (to 'wake' up the slave BMS's and allow its features to work).

Yeah, and it might also need the master BMS for the safety cutoff relay, and do the slave BMS's operate the low/high temp/voltage cutoffs if no master is present, if they are not woken up?...

Did you read both of these threads? The one above, and this one:

Valence XP Super Thread

#1: I'll try and keep this organized. We're limited to 10,000 characters so this will be a multi part post. If you have an XP battery or a bunch of them this will be a good thread for information on how to treat them properly. We'll discuss what the Valence Brand U-BMS actually does and how to...

diysolarforum.com

Still trying to learn about it, but if I had a battery system where it was designed to have a master BMS to control slave BMS's, I would want to try and make that operational... And then it seems you might still need a balancer solution to go between the 2s on top of that (if you started to notice drift)...

 

[SlowCredit]

Yeah think I've read most of what is out there - would love to have some sort of turnkey/plug-play solution, but that just doesn't seem possible - especially with series connected batteries. The Muller BMS costs about what I spent on both batteries, so that just doesn't make $$$ sense.

No experience building Arduino devices - can manage the python and c - so that might be a way to go. Have a couple raspberry pi devices, so might look at loading one up with win10 and seeing if keeping the valence software running/connected keeps the 2 batteries balanced as a quick and dirty first pass..

Guess the next affordable option would be to investigate building my own - not opposed to some experimenting/learning.


Think there are a bunch of us that were hooked by the good high level reviews of these batteries and thoughts of "built-in BMS", only to be surprised when we realize we didn't read the fine print. . .

 

[Samsonite801]

Well live and learn... That's the problem with the black box 'enterprise' solutions (proprietary technology), is you have to reverse engineer them in order to use them effectively (since they have pay-for support contracts and won't help DIY guy), I like to stick with open-source where possible/practical, open to the DIY community.

That's also the reason I'm not a big fan of ready-made batteries in general, is they are black box, they often times don't give much detail in the sales literature about to what level the BMS is protecting things, and I don't mind on a 10-year warranty battery, because black box is ok then... But if it has a 1-year warranty and it fails somehow after a year, then you gotta whip out the die-grinder with a carbide wheel and do the other 9-years of warranty servicing on your own...

Whispering really quietly (SELL, SELL, SELL!!!)

No seriously, if you do keep the Valence setup, you'll probably wind up being an expert at how they work... It sounds like a cool and advanced system if you have it all set up the way the factory intended for it to work, I mean, they designed it for the quality and reliability requirement of the medical industry...

 

[TheRiguy]

Hello folks....newbee here to the DIY solar RV set ups. I got my hands on one of these 12XP-138Ah batteries for my small RV. If I am reading this right I need to get an external BMS for this battery???? Is that true even if I am just running one of these batteries??? I do not have the need or space for any more then one.

 

[Travis]

Everything above is true. If using thunderstruck you also need an additional series balancer and yes the muler BMS is expensive but not obtainable any longer and honestly was a piece of junk.

It would be a very very bad idea to use these batteries without having the internal balancing board awake.

I sell a plug and play box but it's not cheap enough for people with only a few batteries. The valance system is really only beneficial for people with large battery Banks.






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