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paulz
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# Posted: 29 Sep 2019 03:46pm
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My new (to me) Valence U27-12XP 138AH lifepo battery has arrived. I figured out how they sell these used so cheap, they gut 'em and put a lead battery inside.  Just kidding, but it weighs as much as a regular car battery, I was expecting much lighter.
With the amount of these being sold on the used market you'd think there would be more info out there on caring for them. What I have gleaned so far is: they come with some BMS circuitry inside but you need software and special cable to use it. Not everyone does this. There is a blinking light on top, mine is blinking green right now. Some say just charge it to a lower voltage (under 14) and don't let it run too low and it's fine, the internal bms won't allow overcharge. Others say charge to 14.6. No float charging. Cell balancing? Don't know. Charge amperage? Don't know. Recharge voltage, don't know. I have a charger with an 'equalizer' setting but says it's for flooded batteries only.
This is a bit like having a new car in the driveway and no keys. If anyone comes across a good web site explaining these please let me know.
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ICC
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# Posted: 29 Sep 2019 04:28pm
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It is heavy because inside the box will be several hundred small steel cased cylindrical cells. Each one something like 18 mm x 65 mm. Maybe 400 or so.
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ICC
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# Posted: 29 Sep 2019 04:40pm - Edited by: ICC
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The BMS circuitry inside the box may be useless without the external plugin pieces. Just a guess. The main thing that will kill those cells is charging to too high a voltage. Discharging too low is also bad. That is the job of the BMS.
Too high a voltage is a very fast kill.
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paulz
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# Posted: 29 Sep 2019 08:50pm
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Thanks ICC. I have it on a 2 amp manual charger now. We'll see how high it goes, I'll probably chicken out and unplug it before I go to bed.
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ICC
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# Posted: 29 Sep 2019 09:59pm
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Do a search on charging lifepo4 cells without using a BMS.
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Steve_S
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# Posted: 30 Sep 2019 06:08am
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Valence LiFePo04 battery info here:
https://lithiumwerks.com/valence-batteries/
https://lithiumwerks.com/wp-content/uploads/2017/02/Valence-Module-Range-071717.pdf
Did you buy new batteries or some of the used ones ? I just saw that used ones are available on ebay & amazon and some retail shops too...
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paulz
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# Posted: 30 Sep 2019 09:52am
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I bought a used one. Been watching them on Ebay, then Ebay sent me a 10% off coupon, why I don't know but it tipped me over the edge. Sure looks new though. Seems to be a flood of these things becoming available, and selling pretty well too.
Thanks for the links Steve. Been reading all I can, nothing like the potential to ruin a $350 battery to make you bone up. Still a bit of mystery surrounding the circuitry inside. It does have an LED outside, green for good,yellow for charge and red for dead, that apparently functions without their BMS, and the cell balancing might too. It has 5 pin com cables for their BMS (and to daisy chain batteries), I thought I could measure each cell voltage there but tried last night with a DVM and got nothing. One guy on youtube was able to connect an inexpensive cell meter, I have one coming. I'm not in a hurry to use it, outside curiosity, my lead batteries are still hanging in there.
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ICC
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# Posted: 30 Sep 2019 03:38pm - Edited by: ICC
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The data sheet states the Valence U27-12XP uses an external BMS. If that is the situation then inside the case will be some temperature sensors and some wiring.
Can you find any info on how the hundreds of cells inside the box are configured? The number of parallel and series strings of cells for example, and the number of cells per parallel and series string? I see no such info on a quickish looksee. That can help you sort out whether or not some other BMS may be usable.
IMO, using and charging a battery like that, without a BMS, can lead to trouble.
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paulz
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# Posted: 30 Sep 2019 04:51pm
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The cells are grouped into 4 strings, each 3.65 volts at full charge, not supposed to drop under 2.2. I've had it on a 2 amp charge today, it's at 13.3, or 3.325 per assuming they are close to balanced. I should have the cell meter later this week so I'm not going to use it until I see if I can get that to work.
The Valence BMS doesn't seem to be easily available to us second handers, I haven't read of anyone who had gotten one, and other brands I think require opening up the battery and removing the Valence circuits.
Some guys I believe use a clamp on meter you may have mentioned to monitor state of charge by kwh.
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ICC
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# Posted: 30 Sep 2019 06:03pm
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OK, 4 parallel groups. Cells in parallel keep each other at the same voltage. Those are connected in series. If each is fully charged at 3.65 volts you should have 4 x 3.65 volts = 14.6 volts at the meter, no load. If you cut the maximum voltage back to 14.0 to 14.2 volts, that gives you a little insurance against imbalance overcharge and will increase the lifespan of the battery a little. You give away a little usable capacity for extra life.
I do a similar thing with my prismatic LFP cells in the off grid system I have. In 12 volt terms the maximum voltage I use is 14.2.
The minimum voltage of 2.2 per parallel pack seems much too low. My system will shut down if 2.5 volts per cell is reached for 30 seconds. I get an alarm if 2.8 volts per cell is hit, plus a text message if that happens. That has only happened the one time I tested the system when it was new.
A clamp meter is just an easy way to measure the current flow at that point in time without having to disconnect wires. You clamp it around a single pos or neg wire, or the hot or neutral wire in AC circuits, and it gives you the amps flowing.
There are meters that are wired into the system with a thing called a shunt. The meter can be an instant read ammeter or can be a cumulative meter. They can handle very high currents depending on the shunt used. It measures energy into ans energy out of the battery. With lithium batteries being so efficient in charging and discharging one of those can give a very accurate state of charge reading.
Example of the type....
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paulz
Member
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# Posted: 30 Sep 2019 10:40pm
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So say there are 100 individual cells that make up one of the 3.65 volt groups, 4 of which are wired in series to get to 14.6 volts. If any one of those is at 3.2 volts for instance, the other 3 will be the same, correct? What does balancing actually do then?
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ICC
Member
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# Posted: 30 Sep 2019 11:38pm
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A large group of 100 cells in parallel will remain quite stable over time, especially when high quality cells are used. Like Tesla uses Panasonic cells. But all cells can have small differences and over time those differences can become greater with use. With a large parallel pack if one cell dies there will be not much noticable difference, but it will be there.
The imbalance comes in as one group may decrease in capacity faster than the others. The extreme example of that would be a series string of single cells. If one cell has a drop in capacity the voltage will drop faster in it than in the other cells. That low cell can then cause the other cells to be overcharged and hasten their failure. That is because the charger measures the total voltage of the string. Say we have 3.4 + 3.4 + 3.2 + 3.4. If everything charges evenly when the 3.4 cells reach 3.65 the system sees the voltage still has a ways to go to reach 4 x 3.65 and keeps charging. The result is 3 cells get to high a voltage by the time the low cell reaches 3.65 volts.
Having large parallel groups helps slow down that imbalancing process.
With an balancing BMS on a system like mine using large individual cells, that system will actually shunt current away from the full cells into the lower cells.
When there are cell groups of many smaller cells, like the Valence battery, I am not actually sure of what happens. But cells that go dead will drag down that group. I think they figure the change between groups will be relatively small and use the BMS to balance the parallel groups to each other. The battery capacity slowly decreases. If the parallel cell packs are not balanced the differences between high and low will increase over time. Over timethere will be one or two groups that receive more and more overcharge hastening their demise. If a BMS was not needed the manufacturer would not spend the money on using them.
I have a friend who does manual balancing on his large prismatic cell CALB cells. But he only has 8 cells in series. He also never brings the cells above 3.5 volts and never drops below 3.0 volts. Once a month or so he measures each cell. If they still are close in voltage he does not bother doing anything. In the 18 months or so that he has had them he has done a manual balance once. I just talked to him and he figures that he'll do another manual balance around Thanksgiving.
A manual balance is done by disconnecting all the cells. Then each cell is charge to the same voltage measuring with a precision charger meter to within 0.01 volt. All cells are then connected in parallel and either left connected with no charge or discharge or perhaps a very slow charge until the target voltage is reached. Then the cells are reassembled in series.
That manual balance can be done with 8 cells without too much bother. But impossible with an assembled battery of hundreds of small cells. So he has a little bother once a year or so but has saved the expense of a BMS. He likes to tinker more than I do, so that helps too.
I see Valence batteries have been available in large used quantities both here and in Europe for several years. They all seem to be advertised as having been used for only a few hundred cycles out of the thousands life that is claimed. I have to wonder why there are so many available?
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paulz
Member
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# Posted: 1 Oct 2019 07:10am
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Thanks ICC, that helps to understand.
Yes I too noticed the abundance of Valence batteries that seem to have hit the used market recently. Being used in trucking fleets, heavy equipment etc. there is bound to be accidents, machines wearing out, equipment upgrades but are those the only reasons or is it related to the batteries? No idea. Haven't read of anyone who has been disappointed.
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Brettny
Member
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# Posted: 1 Oct 2019 08:06am
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I thought they where used in medical equipment but i also know there used in industrial trucks. I think the big benifit of a BMS is that in its former life it used one thus making there life longer.
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paulz
Member
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# Posted: 1 Oct 2019 08:43am - Edited by: paulz
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Yes, looks like at least the smaller 40ah units are used in medical devices, as this enthusiastic young man mentions in his video on Valence/solar hookup and test. He also mentions internal overcurrent protection built in, without external BMS.
https://www.youtube.com/watch?v=L43bArxyszU
Medical batteries might get changed on a routine basis regardless of condition, at least that's the way on lead bats.
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ICC
Member
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# Posted: 1 Oct 2019 09:51am - Edited by: ICC
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Quoting: paulz He also mentions internal overcurrent protection built in, without external BMS.
I saw a data sheet that listed maybe a dozen different Valence batteries/ Most were in a group that were stated to use external BMS and a few were in a smaller group that had internal BMS. The part number you bought is listed in the NO BMS included list. No idea anymore just where I found that though.
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creeky
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# Posted: 2 Oct 2019 10:10am
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A good BMS isn't that expensive anymore. I would put a BMS on them.
You should be able to read the pins. The trick is to find the "neg" and then read the cells. If you have 5 pins coming out one should be the neg and the others should be the pos for each cell. (I'm simplifying).
If there's no signal somethings wrong with the plug.
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paulz
Member
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# Posted: 2 Oct 2019 01:34pm
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Yes 5 pin and the ground is supposed to be at one end. I tried every combination on both the in and out cables. Nothing. It has that LED that's flashing green and I think there is a circuit board inside. I have read that in order to use another BMS you have to open it up and remove that board. But yes there are several models, RT, XT like mine that differ so not sure.
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paulz
Member
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# Posted: 3 Oct 2019 12:01pm - Edited by: paulz
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Found more info that indicates the XP batteries have internal monitor and balancing:
"Valence integrates battery management throughout the U-Charge® product line. Each U-Charge®
battery contains internal circuitry to monitor and balance each cell. Through built-in communication
cables, the modules are able to communicate to the U-Charge® Battery Management System (BMS),
which monitors the system as a whole. The BMS initiates module-to-module balancing, as well as
controls opening and closing the contactors. The BMS asserts warnings and alarms, and outputs data via
digital and analog outputs. The BMS is small and compact, and can be mounted in the battery pack or
remotely. It uses CANbus to communicate with other equipment and can control such items as chargers
and fuel cells. The BMS can also connect to a PC/Laptop via the CANbus Monitoring Kit, for easy
configuration, monitoring, or recording.
Models: U1-12XP, U24-12XP, U27-12XP, UEV-18XP, U24-24XP, U27-24XP, U27-36XP
Link:
https://2n1s7w3qw84d2ysnx3ia2bct-wpengine.netdna-ssl.com/wp-content/uploads/2019/03/m orningstar-lithiumwerks-compatibilty-technote.pdf
The external BMS may be for multiple batteries, or as they call it modules, which may also be the 4-3.65 groups in each battery, I'm not sure.
I'm back at my house on the grid today, hope to test it out tomorrow back at the cabin. Going to try and get it up around 14 volts first.
Got my little cheapo tester in the mail but it does nothing since I don't get any voltage out of the com cables on the battery.
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ICC
Member
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# Posted: 3 Oct 2019 03:38pm - Edited by: ICC
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Well, that can also be interpretted to mean that each battery has some circuitry built in. That circuitry is used by the BMS.
Note the sentence,"The BMS is small and compact, and can be mounted in the battery pack or remotely. " Sounds to me, like a separate device that connects to each battery to become a full BMS system.
A document linked to in that Morningstar page contains the chart I had seen where the XP series is listed as, "Valence U-Charge® XP Modules with External BMS".
???
As for the lack of voltage at the plugs... we're guessing at things. Those could be purely data connections for signals between what is in the box and what is external. Note the phrase, "Through built-in communication cables, the modules are able to communicate to the U-Charge® Battery Management System (BMS),..."
There is not enough info available for the system in question. Probably by design so they can protect their proprietary BMS system and profit from the exclusivity.
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paulz
Member
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# Posted: 3 Oct 2019 03:57pm
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Quoting: ICC There is not enough info available for the system in question. Probably by design so they can protect their proprietary BMS system and profit from the exclusivity.
Yep, that's what I've been guessing. Whatever the case, I am going to try and use it tomorrow at the cabin. However, I have tried a couple of my standard battery charges on it and it's not climbing about 13.5, even though the charger says it charging at 4 amps. Perhaps these chargers don't put out any more voltage and I need to get a 14+ charger? I could hook it up to my truck, I know that charges higher, with a 20 amp fuse in line, but I'm trying to take it slow with this thing,
Thanks Creeky and ICC for the help.
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ICC
Member
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# Posted: 3 Oct 2019 06:14pm - Edited by: ICC
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Do you know what the maximum voltage your charger is capable of? If it can not produce 14.6 (3.65 x 4 = 14.6) the battery will never reach full charge. The battery can not get to 14.6 if the voltage going into the battery is lower.
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paulz
Member
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# Posted: 4 Oct 2019 09:12am
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The car battery chargers I have all just say 12 volt, I think they top out at 13.5. What about charger for 14.4 volt power tools? Unfortunately I don't have one here at the moment. Too small or would it just take longer?
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ICC
Member
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# Posted: 4 Oct 2019 02:39pm - Edited by: ICC
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What is the maximum voltage a 14.4 v tool charger puts out ??? Likely more than 14.4 just as the charger input to the Valence battery is 14.6 for what they call a 12 volt battery.
Before trying a charger it would be advisable to know precisely what voltage it puts out at maximum as going higher than 3.65 volts on any cell can damage the cells.
I have a DC power supply I use when experimenting or whatever you want to call it. It provides separately controlled regulated voltage and current (CC,CV). (a great deal as gov surplus years ago.
Off hand I'm not sure what else to suggest...
This video shows the cables that hang out of each battery are used to daisy chain one to the other. Have you seen it? That then has their BMS unit connected at one end. That makes me believe those cables are only sending data back and forth. In fact the video states that temperature is one of the pieces of info transmitted to the BMS box. At one point they call those cables a communication loop. The separate BMS box tells each batteries own board what to do as far as balancing the parallel cell packs within each battery box. Not exactly sure how that works with a bunch of series connected battery modules. So I don't know if it would be possible to get cell pack voltage readings directly with just a multimeter. Just thinking and guessing.
I would do my utmost to avoid over-volting the cell packs. Just not sure how with what you have. There is a fine line between fully charging a lithium battery and overcharging and damaging a cell. On the good side... LiFePO4 cells have a greater tolerance for over-voltage than do lithium-ion cells.
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ICC
Member
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# Posted: 4 Oct 2019 02:45pm
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Maybe some help may be derived from this page
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paulz
Member
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# Posted: 4 Oct 2019 05:11pm
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I'm guessing the 14.4 volt lithium tools have the same 4 series setup as me. And I agree on the cables, the Valence BMS is probably what it needed to communicate with the electronics inside the battery. There is one video where the guy opens his up and removes the board to install his own BMS. I did check out that charging link before but hadn't paid much attention, need to study it more.
Meanwhile another snafu has crept up. I'm at my cabin today, brought the Valence. Plugged it into my cabin wiring, wow, 13 volts on the meter! Then I looked over at my wifi router booting up, all the normally green lights were red, and no wifi. The router normally runs off a 12v wall wort, I run it off my 12v deep cycle batteries (along with everything else). I unplugged the Valence, plugged in my usual batteries and it's working. So I guess the Valence voltage is too high. I'm going to have to find a way to reduce it down. I hadn't turned on any lights yet, or the water pump or anything else so hopefully those are all OK.
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ICC
Member
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# Posted: 4 Oct 2019 05:16pm
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What did the blinking green light on the Valence do when it was connected to the cabin?
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ICC
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# Posted: 4 Oct 2019 05:25pm
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Quoting: paulz wow, 13 volts on the meter! Then I looked over at my wifi router booting up, all the normally green lights were red, and no wifi. The router normally runs off a 12v wall wort, I run it off my 12v deep cycle batteries (along with everything else).
Something odd going on... A fully charged lead acid is 12.7 to 12.9 volts. I see higher voltages on the voltmeter in the RV while charging and all the electronics in the RV still work. My 12 volt inverter in the RV accepts up to 16.5 volts input. ???
Do you have a 12 vdc inverter? Check the specs, it can likely take at least 15 VDC input. Try it on the Valence.
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ICC
Member
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# Posted: 4 Oct 2019 05:34pm - Edited by: ICC
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Power light was red/amber too?
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ICC
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# Posted: 4 Oct 2019 05:50pm
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Quoting: paulz So I guess the Valence voltage is too high.
Can you meter the voltage when you apply a small to medium load to the Valence? The voltage should not sag much on a battery that is good. Sorta like how they test a car battery with a load meter.
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