#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 get around needing one. I have recently acquired 220 kilowatt hours of valence batteries so this is kind of like my diary for what I've learned and am continuing to learn about them. I have a huge investment here and I'm really trying my best to treat them right.
Advice here is by no means correct. I'm still reading through the attached 60-page user manual and doing real world testing and lots of manual monitoring so that I may better understand what's going on. Take what is said here with a grain of salt and compare it with the user manual. Decide for yourself what tactic you want to choose when caring for your battery bank. If it's over your head have your trusted solar installer set it up for you. But be warned most of them don't know what they're doing.
One thing I want to bring attention to is most people think the internal cell balancer will do its job when in fact it won't unless it has 4 volts coming in on the communication wire and it's also communicating with a Laptop or BMS.
#2: When good information appears in the thread I'll attach it here below in the first post, put a brief description about it in number threes changelog and reference the post number it came from.
#3: Change log.
3-21-2020
Added a paragraph called installation U27-12XP with some tips that you need to know.
Added a paragraph & link to the wire size voltage drop calculator.
Added a paragraph about proper battery bank wiring.
Added paragraph and link about a do-it-yourself BMS for programmers that approaches the topic valence style using the rs-485 communication.
Added a paragraph called OVER DISCHARGED?
Added Links at the bottom for:
Do-it-yourself Kick-Ass battery charger.
Converting my Prius to charge my house battery.
#4 INSTALLATION:
With the u27-12xp When you're tightening down the lugs on top of the battery be aware that the negative hole is not as deep as the positive hole. This will cause the post to bottom out before it clamps tight on your wires lug. You'll need to figure out what thickness of washer to put in there as a spacer. Definitely use stainless steel or brass washer.
The lugs are stainless steel which is known for maring and getting stuck and breaking off in the hole. I'm not saying these batteries are known for that I'm saying that's just an inherit trait of stainless steel so make sure you clean all of the loctite out of the threads. I had to literally scrape around the threads with a razor knife. It took a long time and then after when I screwed the post into the battery it turns out there was more loctite that fell off of the threads and got in between the battery lug and the top of the batteries mating surface. This is not a good thing because we need this area to conduct electricity without loctite residue being in between. I'm going to purchase a m8 by 1.25 tap and die set to clean these threads before I do my own installation.
And before you purchase wires you should read everything below especially the part about wire length and avoiding destroying your batteries with unequal wire lengths in parallel setups. At some point I'll have some of those high current relays for sale and the interconnecting wires that Mueller industries has for sale which are really nice for these because they're so dang thick you won't have the negative terminal problem previously mentioned.
#5 BALANCING BATTERIES:
Now I want to talk about keeping the 12 volt batteries all at the same voltage as each other. this is very important then I have personally seen these valence batteries in series very greatly in voltage when one reaches full before the other. This will cause the one that reach his full first to be damagingly high in voltage. I'll call each 12 volt battery a battery. I'll call the 4 cells inside it cells. So it takes 4 lithium iron phosphate cells in series to make one 12.8 volt battery. The internet likes to call these batteries modules. So you might see them called modules elsewhere including in the valence software. Throughout the charge and discharge cycle let's say between 20% and 90% state of charge (12.8-13.8) the batteries & their cells will probably stay exactly the same voltage all on their own even if their state of charge it's not quite the same. That's why it's so hard to balance the cells to each other in this range. But when the voltage falls low & the state of charge goes down & your approaching 0% they will start to wonder away from each other in voltage. So let's say you have 4 batteries in series for a 48 volt setup. And you are draining the batteries because the sun went down. The battery that goes dead first will suddenly and rapidly drop in voltage from 12 volts down leaving the other batteries behind as if it were suddenly racing to 0. It will likely shoot down so fast it will catch you off-guard and it will drop below the low voltage recommendation of 10.5 volts. This will damage the battery. No joke DO NOT let this happen!
It's a similar story when you're approaching full charge as well. The battery and or cell that reaches full charge first will rapidly rise and the voltage will shoot above the recommended 14.6 volt upper limit. They can handle higher voltage better than under voltage so they won't get damaged so quickly up there if the battery reaches 15 volts. But it's still not good for the battery and the batteries onboard computer will likely record the over-voltage strike in it's permanent history. That is if the computer has a 5 volt power source and is woke up meaning in communication with the laptop or BMS.
Now let's say you have a 12-volt system and all your batteries are wired in parallel. In this case you will not need a device to balance the batteries to each other because they're literally connected to each other and they will naturally force each other to be the same voltage. They will work in harmony together. Make sure before you connect them together that they are already at the same voltage. It's okay if they vary a bit in voltage if they are over 14 volts or under 11.5v when you connect them together. If you're in doubt it's best to fully charge them all one at a time before you connect them together. However you will need some sort of safety device to disconnect the batteries from the load and or charge if they approach the over voltage or under voltage condition. Your inverter might be set to shut down at 10.5 volts and it's likely you can adjust that number in the inverters menu and if you trust that inverter then I suppose that would work. You would also have to trust that your charge controller didn't have an error and decide to push the voltage higher than it's supposed to. Be careful that you read your manuals for your inverter and charger. By default they'll be set up for lead batteries. They will adjust there voltage drastically according to temperature as if you had a lead battery. You'll need to disable temperature compensation related voltage adjustments or change their settings to be correct for lithium. These are very nice and expensive batteries so it wouldn't hurt to have an extra safety mechanism in place to disconnect if things got out of hand.
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 get around needing one. I have recently acquired 220 kilowatt hours of valence batteries so this is kind of like my diary for what I've learned and am continuing to learn about them. I have a huge investment here and I'm really trying my best to treat them right.
Advice here is by no means correct. I'm still reading through the attached 60-page user manual and doing real world testing and lots of manual monitoring so that I may better understand what's going on. Take what is said here with a grain of salt and compare it with the user manual. Decide for yourself what tactic you want to choose when caring for your battery bank. If it's over your head have your trusted solar installer set it up for you. But be warned most of them don't know what they're doing.
One thing I want to bring attention to is most people think the internal cell balancer will do its job when in fact it won't unless it has 4 volts coming in on the communication wire and it's also communicating with a Laptop or BMS.
#2: When good information appears in the thread I'll attach it here below in the first post, put a brief description about it in number threes changelog and reference the post number it came from.
#3: Change log.
3-21-2020
Added a paragraph called installation U27-12XP with some tips that you need to know.
Added a paragraph & link to the wire size voltage drop calculator.
Added a paragraph about proper battery bank wiring.
Added paragraph and link about a do-it-yourself BMS for programmers that approaches the topic valence style using the rs-485 communication.
Added a paragraph called OVER DISCHARGED?
Added Links at the bottom for:
Do-it-yourself Kick-Ass battery charger.
Converting my Prius to charge my house battery.
#4 INSTALLATION:
With the u27-12xp When you're tightening down the lugs on top of the battery be aware that the negative hole is not as deep as the positive hole. This will cause the post to bottom out before it clamps tight on your wires lug. You'll need to figure out what thickness of washer to put in there as a spacer. Definitely use stainless steel or brass washer.
The lugs are stainless steel which is known for maring and getting stuck and breaking off in the hole. I'm not saying these batteries are known for that I'm saying that's just an inherit trait of stainless steel so make sure you clean all of the loctite out of the threads. I had to literally scrape around the threads with a razor knife. It took a long time and then after when I screwed the post into the battery it turns out there was more loctite that fell off of the threads and got in between the battery lug and the top of the batteries mating surface. This is not a good thing because we need this area to conduct electricity without loctite residue being in between. I'm going to purchase a m8 by 1.25 tap and die set to clean these threads before I do my own installation.
And before you purchase wires you should read everything below especially the part about wire length and avoiding destroying your batteries with unequal wire lengths in parallel setups. At some point I'll have some of those high current relays for sale and the interconnecting wires that Mueller industries has for sale which are really nice for these because they're so dang thick you won't have the negative terminal problem previously mentioned.
#5 BALANCING BATTERIES:
Now I want to talk about keeping the 12 volt batteries all at the same voltage as each other. this is very important then I have personally seen these valence batteries in series very greatly in voltage when one reaches full before the other. This will cause the one that reach his full first to be damagingly high in voltage. I'll call each 12 volt battery a battery. I'll call the 4 cells inside it cells. So it takes 4 lithium iron phosphate cells in series to make one 12.8 volt battery. The internet likes to call these batteries modules. So you might see them called modules elsewhere including in the valence software. Throughout the charge and discharge cycle let's say between 20% and 90% state of charge (12.8-13.8) the batteries & their cells will probably stay exactly the same voltage all on their own even if their state of charge it's not quite the same. That's why it's so hard to balance the cells to each other in this range. But when the voltage falls low & the state of charge goes down & your approaching 0% they will start to wonder away from each other in voltage. So let's say you have 4 batteries in series for a 48 volt setup. And you are draining the batteries because the sun went down. The battery that goes dead first will suddenly and rapidly drop in voltage from 12 volts down leaving the other batteries behind as if it were suddenly racing to 0. It will likely shoot down so fast it will catch you off-guard and it will drop below the low voltage recommendation of 10.5 volts. This will damage the battery. No joke DO NOT let this happen!
It's a similar story when you're approaching full charge as well. The battery and or cell that reaches full charge first will rapidly rise and the voltage will shoot above the recommended 14.6 volt upper limit. They can handle higher voltage better than under voltage so they won't get damaged so quickly up there if the battery reaches 15 volts. But it's still not good for the battery and the batteries onboard computer will likely record the over-voltage strike in it's permanent history. That is if the computer has a 5 volt power source and is woke up meaning in communication with the laptop or BMS.
Now let's say you have a 12-volt system and all your batteries are wired in parallel. In this case you will not need a device to balance the batteries to each other because they're literally connected to each other and they will naturally force each other to be the same voltage. They will work in harmony together. Make sure before you connect them together that they are already at the same voltage. It's okay if they vary a bit in voltage if they are over 14 volts or under 11.5v when you connect them together. If you're in doubt it's best to fully charge them all one at a time before you connect them together. However you will need some sort of safety device to disconnect the batteries from the load and or charge if they approach the over voltage or under voltage condition. Your inverter might be set to shut down at 10.5 volts and it's likely you can adjust that number in the inverters menu and if you trust that inverter then I suppose that would work. You would also have to trust that your charge controller didn't have an error and decide to push the voltage higher than it's supposed to. Be careful that you read your manuals for your inverter and charger. By default they'll be set up for lead batteries. They will adjust there voltage drastically according to temperature as if you had a lead battery. You'll need to disable temperature compensation related voltage adjustments or change their settings to be correct for lithium. These are very nice and expensive batteries so it wouldn't hurt to have an extra safety mechanism in place to disconnect if things got out of hand.
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