# Valence P30-36c Batteries



## DaveBlack (Oct 31, 2018)

Slight change...its not holding charge! held 30v for an hour or so but is slowly dropping now.

Probably as I think it will need at least 3.1v per cell to activate the chemistry and thats when ill know.

I hope, no idea really - winging it as ever!

Dave


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## john61ct (Feb 25, 2017)

Do a proper capacity load test on the ones that appear to recover, .2-.5C rate, stop at 2.99V as 0%

Just brace for the fact they may be scrap.

I use 3.65V for load testing 100% and if top balancing.

In production cycling 3.45V as 100% will be easier on longevity, fewer balance issues ongoing.


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## DaveBlack (Oct 31, 2018)

HI John - thanks for that, I was really focusing on the batteries being able to be charged from a Lead Acid charger rather than the fact they are potentially dead.

Is that true?

Thanks

Dave


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## brian_ (Feb 7, 2017)

DaveBlack said:


> But my testing kinda says thats right - currently I am just pumping 30V into one (max of my Variable voltage Dc output!). I can vary the Amperage and slowly increased this over a couple of hours, I left it at 1Amp. Eventually when the battery Voltage reached 30V then Amperage slowly lowered down until it cut off.
> 
> My DC bench output does not have that kind of smart ability - I just set an output voltage and current and off you go. But the battery seems to be manipulating the current it draws and the voltage.
> 
> That seems pretty bloody clever and if true AWESOME!


There's no intelligence in the battery, and any battery will do that. If you apply a constant voltage, the current which flows depends on

the voltage of the cells due to their state of charge, and
the internal resistance of the battery.
As they charge up, the cell voltage rises. The difference between the sum of the cell voltages and the charging voltage is what pushes current through the battery; the internal resistance is what determines how much current will flow for a given voltage.

So, if each cell is at (for instance) only 2.0 V , and there are 12 in series for a total of 24 V, and you apply 30 V then 6 V is left to push the current. As the cell voltage rises, less voltage is available to push current through the same resistance, so current drops. When the cell voltage equals the charging voltage, no current can flow.


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## brian_ (Feb 7, 2017)

DaveBlack said:


> My query is that on Valence's website for the 'newer' version of this battery the 'U-Charge' version. They say you can charge it with a standard Lead Acid battery charger.
> 
> Really???





DaveBlack said:


> ... I was really focusing on the batteries being able to be charged from a Lead Acid charger rather than the fact they are potentially dead.
> 
> Is that true?


Why not? The charger doesn't know anything about battery chemistry, or what is going on in the battery. It is just programmed in stages (maybe only two stages) for combinations of current and voltage limits. If the voltage suitable for charging a stack of lithium cells happens to match the voltage suitable for charging a stack (of a different number) of lead-acid cells, it can work. Some stages of common lead-acid chargers are not at suitable levels for lithium batteries; one supplier of chargers mostly for recreational vehicles sells a "lithium" version, which is just their regular product with all the extra stages turned off and a higher voltage set for the remaining stage.

43.8 V would correspond to 2.43 volts per cell for a 18-cell lead-acid battery (36 volts nominal), which is a little high but not unreasonable for lead-acid. A charger configured for lead-acid would probably limit to bit lower voltage, which would still work for a dozen LiFePO4 cells.

The Valence modules (or batteries) are configured with a number of cells intended to match them to common nominal voltage of lead-acid batteries - multiples of 12 volts. Stack a different number of cells and a "lead-acid charger" wouldn't be suitable.

Lithium batteries are generally assumed to need more sophisticated management of maximum charging voltage and minimum voltage when discharging than lead-acid, but that's what the BMS is for.


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## brian_ (Feb 7, 2017)

DaveBlack said:


> Before anyone spots the 'why are you charging below the lowest voltage the battery should hold' It is because ALL the batteries are at zero V - no idea why, perhaps a short when the bus crashed or something that was done to make the pack safe?


It would not make any sense to bring the cell voltage below the rated minimum - or even down to that level - for shipping or storage. If they were fully discharged to make them safe, it would be for disposal... having been assessed as trash. Even if they were perfectly good before "making them safe", they would presumably be destroyed by this process.

Perhaps you're lucky and this isn't what has been done.


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## DaveBlack (Oct 31, 2018)

Thanks Brian

So, my 43.8v dc supply (variable A and V settings) that comes tomorrow will act nicely as a test charger to see if I can resurrect one of these lumps. I felt the dropping off of the current was an aspect of the charger - but from what you are saying it is actually as a result of the lowering difference in charger and battery voltages.

Neat

I will do a discharge test after a charge to see what has actually been stored. even if they are 50% good I will be happy for V1 of my car. For free these are both spending the time on and a little bit of money on.

If they are totally dead I may look at the individual cells... but with over 4000 of them, maybe not!!!

Cheers.


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## brian_ (Feb 7, 2017)

DaveBlack said:


> If they are totally dead I may look at the individual cells... but with over 4000 of them, maybe not!!!


If a complete 144-cell module (battery) isn't up to the fully-charged voltage, that can mean that some parallel sets of cells within it are dead and others are fine, so the total is less than it would be if they were all good. I don't think there's any way around checking voltages at least at this group-of-cells level to assess condition.


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## DaveBlack (Oct 31, 2018)

brian_ said:


> If a complete 144-cell module (battery) isn't up to the fully-charged voltage, that can mean that some parallel sets of cells within it are dead and others are fine, so the total is less than it would be if they were all good. I don't think there's any way around checking voltages at least at this group-of-cells level to assess condition.


Yeah, if one battery is not able to get to / hold full voltage then I can strip it down into its 12 groups of 12 cells. If a series of 12 has the same issue then do the same down to the cell level.

Im sure from the 4000+ cells I should have enough to produce 'some' working battery packs...or create a massive battery just from the cells - ooohh thats a nice idea, can be any shape I want then.

I can see inside the unit and there is no evidence of any cells having puffed up. Not that shows everything - but from my quad copter flying, the batteries tended to give up around the time they got fat ;o) 

Well that and when you hit a tree and the thing catches fire - but thats another story!

Cheers

Dave


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## pdove (Jan 9, 2012)

If the battery reads 0V then it is dead and will never come back.


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## john61ct (Feb 25, 2017)

And when flat-murdered, no swelling


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## pdove (Jan 9, 2012)

john61ct said:


> And when flat-murdered, no swelling


LiFePO4 cells usually don't swell.


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## DaveBlack (Oct 31, 2018)

pdove said:


> If the battery reads 0V then it is dead and will never come back.


ohhh I sense a challenge - seems a lot of people online disagree but results are mixed. Ill keep you updated!

Dave


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## john61ct (Feb 25, 2017)

pdove said:


> LiFePO4 cells usually don't swell.


Yah right.

Seen literally hundreds do it.

Pretty silly not to include straps and plates into your build.

Certainly every systems vendor does.


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## brian_ (Feb 7, 2017)

DaveBlack said:


> I can see inside the unit and there is no evidence of any cells having puffed up. Not that shows everything - but from my quad copter flying, the batteries tended to give up around the time they got fat ;o)





john61ct said:


> And when flat-murdered, no swelling





pdove said:


> LiFePO4 cells usually don't swell.


The bulging may be more typical of polymer-electrolyte cells (regardless of electrode materials) than of these ones.


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## brian_ (Feb 7, 2017)

DaveBlack said:


> Yeah, if one battery is not able to get to / hold full voltage then I can strip it down into its 12 groups of 12 cells. If a series of 12 has the same issue then do the same down to the cell level.


Are they really assembled into strings of 12, then 12 strings in parallel? It would be more typical to put 12 cells in parallel, the 12 of those sets in series.


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## brian_ (Feb 7, 2017)

DaveBlack said:


> Yeah, if one battery is not able to get to / hold full voltage then I can strip it down...


Even if a battery does get to your target voltage, that may only mean that most of the cells are overcharged, and some others are dead. Presumably you can get to the cell level via the BMS wiring, so you could check before pushing the whole battery all the way to the target "fully charged" voltage.


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## pdove (Jan 9, 2012)

DaveBlack said:


> ohhh I sense a challenge - seems a lot of people online disagree but results are mixed. Ill keep you updated!
> 
> Dave


I don't put much stock in what people online say..... unless they have personal experience and seem credible. I have spent considerable time playing with LiFePO4 cells and every cell that went to zero could not hold a charge. The voltage rises during charging but as soon as it cuts off it drops back to zero.


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## pdove (Jan 9, 2012)

brian_ said:


> The bulging may be more typical of polymer-electrolyte cells (regardless of electrode materials) than of these ones.


The CALB cells I have didn't swell at all. The Bestco cells I tested did swell when shorted slightly and I also had a Hipower cell that swelled but it wasn't zero but had a reduced capacity. So I guess I shouldn't say my experience is varied on this topic. I never played with a Valence cell they look pretty sturdy.


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## pdove (Jan 9, 2012)

john61ct said:


> Yah right.
> 
> Seen literally hundreds do it.
> 
> ...


Some vendors do but not all. CALB cells seem to be contained by the casing so they don't swell.... at least the one I have that failed didn't. Of course, that is only a data point of one.


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## DaveBlack (Oct 31, 2018)

Seems my post about using a Lead Acid Charger has gone a little off topic, but after a bit more research...

Yes a Lead Acid charger is fine for LifePo4 batteries - mainly as they are much happier with an over charge voltage that the Lead Acid battery charger will generally supply. Valence themselves say you can charge these with a Lead Acid Charger.

I have been charging the one battery today, just at 40.4v of the 43.8v optimal charging value.

Started slow, and risen to 3a now (about as much as my new supply can give out). Battery has risen to 39.8v and still rising but really slowly now as expected.

Ive taken a reading from all 12 strings, 3.2-3.4 is the range. Nearly all are 3.3v

Unsure if the balancer is trying to balance them already - and the spare capacity in the cells are making up for the fact some are dead. So could in reality have single cells at 0v and others at 4v - no way of knowing without checking every one of the 144 (I might spot check a few that I can reach with my multimeter from the side).

Also no idea if this is going to hold a charge - I will stop charging at bed and see how it is in the morning.

Final note - Valence actually have instructions on what to do and how to charge a totally flat battery. Basically start off slow and ramp it up - I have even reset the balancer and that is showing a green light! But yes I appreciate that is likely just green for a good voltage and my Power supply is doing that. Seems odd Valence would give instructions on charging from 0v if at least something could work?

Will update in the morning, get your predictions in - what voltage?

Cheers

Dave


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## DaveBlack (Oct 31, 2018)

Lol, cant check any cells can I! DOH they are in parallel with the rest of the string so I just get the string voltage that I have already!

ah well.

Dave


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## john61ct (Feb 25, 2017)

DaveBlack said:


> HI John - thanks for that, I was really focusing on the batteries being able to be charged from a Lead Acid charger rather than the fact they are potentially dead.
> 
> Is that true?


Yes. There in fact is no such thing as a charger for a particular chemistry.

As long as the current amps are appropriate, say between .1C and .5C,

and voltage is adjustable, maybe overcurrent protection is important in some cases,

any old power supply will do, you can make it work manually regulating.

Of course if the bank survived, once "in production" you may want to automate the charging process, but that's a different issue.

And again, only a load test will show State of Health, the residual Ah / kWh capacity compared to their original rating when new.

Multiply the voltages I gave you for 0% and 100% SoC times the cells per string, and set up a .2C load compared to their AH rating. 

The percentage of time compared to 5 hours it takes that load to drop the bank / string / block / cell from 100% to 0% SoC is your SoH.


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## MattsAwesomeStuff (Aug 10, 2017)

> I have spent considerable time playing with LiFePO4 cells and every cell that went to zero could not hold a charge. The voltage rises during charging but as soon as it cuts off it drops back to zero.


Big Clive on Youtube did a bit or research on actual peer-reviewed papers on this a while ago.

https://youtu.be/sRwoYJyjZNo?t=132

https://www.nature.com/articles/srep30248

The conclusion of the papers is if the cells is reverse-charged more than 15% of its capacity, that's when the irreversible damage occurs. Until then, it should recover quite well.

Of course, a reverse-charged cell will re-settle to zero volts, so you have no idea whether it returned to zero after being reversed charged (part of a series pack where it was the weak cell), or just discharged to zero (for example, with a small load that was left on).

In my experience, I'd say probably 3/4 of cells I've attempted to recover from 0v are operating as good as any others in their pack. The other 1/4 take forever to charge, get scalding hot, and quickly self-discharge back to low voltages when removed (huge internal shorts).


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## rmay635703 (Oct 23, 2008)

If he wants to have any hope of recovery he needs to cycle at the 3.2 volt individual cell level,

Bulk charging flat 36 volt packs is a total waste of effort and likely will damage any functional cells in the mean time


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## DaveBlack (Oct 31, 2018)

So, charged at 3.4v (optimal max 3.65v I know)

Initial drop when I stopped charging to 3.3v (slowly) and has held solid over night.

I would estimate (very roughly) from the time charging, at increasing Amperage, the battery had about 20Ah thrown at it. It has a capacity of 30Ah.

Gonna try to rig up a discharge test as the ultimate 'lets see' what capacity it holds down to about 2.8v per string.

Dave


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## john61ct (Feb 25, 2017)

DaveBlack said:


> So, charged at 3.4v (optimal max 3.65v I know)
> 
> Initial drop when I stopped charging to 3.3v (slowly) and has held solid over night.
> 
> ...


3.45V is the highest you need to go for regular cycling.

allowing amps to taper down to below .03C or so will get you within 2-3% of 3.65V 

but without all the stress, much greater longevity. When top cell balancing OK, but that is very rarely needed if you avoid the shoulders.

3.3V resting is good, you might have gotten lucky!

likely has some surface charge, remove a fraction of an AH and you should see ~3.2V

Do not (ever) let them drop below 2.99V if you can help it, again for longevity.


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## pdove (Jan 9, 2012)

DaveBlack said:


> Seems my post about using a Lead Acid Charger has gone a little off topic, but after a bit more research...
> 
> Yes a Lead Acid charger is fine for LifePo4 batteries - mainly as they are much happier with an over charge voltage that the Lead Acid battery charger will generally supply. Valence themselves say you can charge these with a Lead Acid Charger.
> 
> ...


Sorry Dave, I missed your question completely but looks like you found answers. All chargers are just power supplies some more complex than others. Also, voltage is not important as long as it is above the natural voltage of the battery. LiFePO4 cells have a resting voltage of 3.38 volts. So your 40.4 would be 3.3666 volts per cell. It would take a long time at that voltage to finish the charge that is why most manufacturers use 3.65 volts per cell when in Constant Voltage mode (CV). Constant voltage mode is where the power supply holds the voltage constant by lowering the current as the cell voltage rises. Most automated Lithium battery chargers us CC/CV to charge a cell. In constant current mode they control the current and ignore the voltage then when the cell reaches the desired voltage they switch to CV mode until the current falls below the desired point, usually C/20 to C/5. The issue with a lead acid battery charger is that it may not have the CV mode. However, in reading about these Valence batteries this is controlled by the BMS in the battery. The BMS may also explain the zero volts reading. It is possible it shuts off the output when the cell drops below a certain point. Also, may explain their zero volt procedure. I have played with a few laptop batteries and drill batteries and some manufactures turn the cells off with their BMS when they see an issue. One laptop battery I opened had a bad cell. I put all new cells in it and it still wouldn't work in the laptop. The BMS had marked it bad permanently. 

Please post back your final findings because I have always been interested in Valence batteries.


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## pdove (Jan 9, 2012)

pdove said:


> ..... However, in reading about these Valence batteries this is controlled by the BMS in the battery. The BMS may also explain the zero volts reading. It is possible it shuts off the output when the cell drops below a certain point. Also, may explain their zero volt procedure. I have played with a few laptop batteries and drill batteries and some manufactures turn the cells off with their BMS when they see an issue. One laptop battery I opened had a bad cell. I put all new cells in it and it still wouldn't work in the laptop. The BMS had marked it bad permanently.


Turns out I was right. Here is what is in their user manual:

7.1 Discharge Control 
When the modules are discharged to the point where any single cell block reaches its minimum value, 2.45V, the battery will interrupt discharge.

  The battery will appear to have 0V (or evennegative voltage) across the terminals. No current will flow. However, the battery will accept charge. 

https://mrbill.homeip.net/downloads/userGuideValenceRT.pdf


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## DaveBlack (Oct 31, 2018)

pdove said:


> Turns out I was right. Here is what is in their user manual:
> 
> 7.1 Discharge Control
> When the modules are discharged to the point where any single cell block reaches its minimum value, 2.45V, the battery will interrupt discharge.
> ...


Wow good find, although how on earth does it do that? The BMS on top has 25 wires going into. 12 I have verified are the balancing wires, with an earth at the end (so 13). The other 12 I think are temperature sensors hanging in the chassis. 

The BMS was Off aswell - and did not turn back on until I got the Voltage to 5v across the pack. At which point it started flashing red. Once I got above 30v I unplugged restarted the BMS and it now flashes Green ;o)

Ive just gone through the same process with a second one of these. I have 27 of them!

Wouldnt the BMS have to be in series with the actual input / output of the battery to affect flow? The circuitry does not look up to passing 36C !
Good find though what do you think based on the above?

Dave


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## DaveBlack (Oct 31, 2018)

I guess it is this internal disconnect below.

When the modules are charged to the point where any single cell block reaches its maximum
value, 3.9V, the battery will prohibit further charging by opening up an internal disconnect.
When the voltage of the cell returns to a value less than 3.7V, its internal disconnects will
automatically reset. 

It also says about these being 'put to sleep' which turns off the BMS to conserve battery. I bet they had been put to sleep which is why they were off and the disconnect was active hence seeing no volts?

God knows, need to rig up a drain to measure capacity - but these might just well be a bloody grand find!

Dave


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## pdove (Jan 9, 2012)

DaveBlack said:


> Wow good find, although how on earth does it do that? The BMS on top has 25 wires going into. 12 I have verified are the balancing wires, with an earth at the end (so 13). The other 12 I think are temperature sensors hanging in the chassis.
> 
> The BMS was Off aswell - and did not turn back on until I got the Voltage to 5v across the pack. At which point it started flashing red. Once I got above 30v I unplugged restarted the BMS and it now flashes Green ;o)
> 
> ...


 From the manual:

If the LED indicator blinks RED, one of the following has occurred: 
• Cell voltage is < 2.45V even after 1 minute of charging. 
• Internal electronics’ temperature is between 85 and 100 °C. 
• If it’s red due to an over discharge or self discharge condition and the LED is blinking 
slowly (on for 2 seconds, off for 3 seconds)

A green blinking LED indicator on the lid of the battery is used to indicate the working status. It will blink once every 20 seconds when in park and shelf mode, and once every 5 seconds when it is awake and active. 

For normal charging, use a battery charger that has an output of 20A or less until the Voltage reaches Recommended Charge Voltage and then automatically tapers the current down to maintain a constant Optimum Float Voltage (CC-CV-CV). Charging is considered complete when the current is less than C/20 for the system. However, leaving 
the batteries on float (between 13.8V-14.6V per battery) will continue to balance the cells and will not harm the batteries in any way. For normal charges, the battery temperature should be between 0 and 45°C (32 and 113°F). Internal resistance of the battery is higher at colder temperatures. Thus, the charge acceptance of the battery will be less when the temperature is less than 0°C (32°F). This may increase the charge time. The value of the charger’s voltage limit is calculated by multiplying the number of batteries that are connected in series by 14.6V. 

Example for charging 4 U-Charge® batteries: 
•Charge to 58.4V = (14.6V x 4 batteries in series) and hold. 
•When voltage reaches 58.4, the battery is approximately 90% charged. 
•Allow the current to naturally decay when voltage is reached. 
•When the current drops below 2A for U1, 5A for U24, and 6A for U27, the battery is considered 100% charged. 
•Continue to float charge at 58.4V. 
•It will not hurt the battery if the voltage is continuously present, even after 100% SOC is reached. This will aid in balancing. 

If a U-BDI is attached, the 10 bar LEDs will light up according to 
the system’s state of charge. Once any cell has reached 3.65V, the yellow LED will illuminate. This is normal and is just telling the user that balancing has started to occur.

When the battery has a GREEN LED status indication, it can be discharged in a normal manner. If the LED is YELLOW, the battery is either nearing a thermal limit or the capacity is less than 20% SOC. If any battery has a RED LED status indication, it will stop discharging. A battery will also stop discharging once it has exhausted capacity. In this case, it will return to normal (GREEN LED) once the cell voltage increases over 2.7V during charge.


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## pdove (Jan 9, 2012)

DaveBlack said:


> I guess it is this internal disconnect below.
> 
> When the modules are charged to the point where any single cell block reaches its maximum
> value, 3.9V, the battery will prohibit further charging by opening up an internal disconnect.
> ...


It says the BMS will calculate capacity.


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## DaveBlack (Oct 31, 2018)

Just a quick update...

I have now 'charged' 9 of these to 40.4v (3.36ish per S)

They have all settled to between 39.6-39.8 after around 24 hours. 

I have purchased a 20a discharger that will log the output - hopefully this will come tomorrow and I can see how much charge is in one of these.

Ill then do a max charge on one and see what the output is after.

Resetting all the BMS's once the voltage is +30v is giving me green lights across all of them so far. I don't have the right gear to interact with the battery, so cannot see if the batteries are complaining about S's being out of balance.

On a final note - what do you think these are worth each? Say even at 50% capacity working or more (which I am leaning towards these being pretty high from everything I have seen / read)

Dave


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## pdove (Jan 9, 2012)

LiFePO4 cells do experience capacity fade when they sit for a long time but it should be fully recoverable. You may have to charge and discharge them several times to recover full capacity depending on how long they have sat unused. I let some 100Ah cells sit for 1.5 years and when I discharged them I got 45Ah. The second time I cycled them I got 65 Ah and by the fifth time I got exactly what the manufacturer claimed they had when new.

Based on the part number they are 30Ah cells. With 4 cells per battery so 120 30Ah cells. You can buy LiFePO4 cells brand new for $1 an Ah. so 30 times 120 = $3600. You can't get that used but you might get half.


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## DaveBlack (Oct 31, 2018)

Thanks Pdove - any idea what these are worth? I have 27 of them! 

Thinking of using 12 in the car which leaves 15. Might do another project I guess - Or actually thinking of wiring them into my solar panels with a switch to run on batteries over night...

Dave


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## pdove (Jan 9, 2012)

Based on the part number they are 30Ah cells. With 4 cells per battery so 120 30Ah cells. You can buy LiFePO4 cells brand new for $1 an Ah. so 30 times 120 = $3600. You can't get that used but you might get half.


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## DaveBlack (Oct 31, 2018)

pdove said:


> Based on the part number they are 30Ah cells. With 4 cells per battery so 120 30Ah cells. You can buy LiFePO4 cells brand new for $1 an Ah. so 30 times 120 = $3600. You can't get that used but you might get half.


Hay - what do you mean by 4 cells per battery? Each one has 144 individual cells in. (12 series of 12 cells, giving 38.4v per battery with 30AH)

Interesting the $1 per AH price - there must be a difference between 1AH @ 12v compared to 1AH @ 36v?

Unless you mean $1 per AH for a single 3.3v LifePo4 cell on its own?

Sorry if I missed the obvious!!!

Dave


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## brian_ (Feb 7, 2017)

pdove said:


> Based on the part number they are 30Ah cells. With 4 cells per battery so 120 30Ah cells.


That's 30 Ah for the whole battery, so the capacity of the battery is the same as four cells in series, each of 30 Ah capacity.



DaveBlack said:


> ... what do you mean by 4 cells per battery? Each one has 144 individual cells in. (12 series of 12 cells, giving 38.4v per battery with 30AH)


Yes, these batteries appear to be built of small cells, so 12 cells are required for 30 Ah of capacity... 2.5 Ah per cell. Are these Valence batteries built of small cylindrical cells (maybe 26650)?



DaveBlack said:


> Interesting the $1 per AH price - there must be a difference between 1AH @ 12v compared to 1AH @ 36v?
> 
> Unless you mean $1 per AH for a single 3.3v LifePo4 cell on its own?


I'm sure that's what he meant: individual LiFePO4 cells cost about $1 per Ah. 1 Ah @ about 12 V would then be $4 (4 cells in series), and 1 Ah @ about 36 V would then be $12 (12 cells in series).


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## pdove (Jan 9, 2012)

DaveBlack said:


> Hay - what do you mean by 4 cells per battery? Each one has 144 individual cells in. (12 series of 12 cells, giving 38.4v per battery with 30AH)
> 
> Interesting the $1 per AH price - there must be a difference between 1AH @ 12v compared to 1AH @ 36v?
> 
> ...


Sorry I wasn't clear! Perhaps I made a mistake. If the battery is 12 volts then you need 4 cells at 3.4 volts to give you 13.6 volts 12 cells would give you 40.8 Volts. Don't count the ones in parallel since they only add to the Ah capacity. 12 cell per battery X 30 batteries = 360 cells at 30 Ah each. So, seems I was wrong the first time. $30 times 360 cells = $10,800. Another way to calculate it would be in Wh. 40.8 V X 30Ah X 30 batteries = 36Kw or about $0.30 a Kwh


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## john61ct (Feb 25, 2017)

Yes 4S is just used in a 12V context, as in House or ICE Starter usage.

Not relevant to EVs.


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## DaveBlack (Oct 31, 2018)

Quick update.... 

My battery discharger arrived so I can see how much charge these batteries are holding.

I have been charging them with 40.4v (about 3.36v per s)

The battery I chose to test had settled at 39.7v (3.3v per s)

I discharged to about 2.5v per s, with 18AH / 631WH of power given.

Pretty happy with that as a first test - going to now charge the same battery to 3.6v per s (43.2v total input). Will do another discharge and see what we get!

I will probably do two or three more cycles on this one battery then spot check a couple of others. If they show consistent results then im well chuffed!

Dave


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## john61ct (Feb 25, 2017)

Discharging to 2.99Vpc rather than lower won't make much difference, more realistic and lots less stressful.

I personally would usually only go above 3.45Vpc when top balancing, but 3.60 isn't too bad if you want the extra 3% or so, just start discharging soon after.


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## DaveBlack (Oct 31, 2018)

Cheers John - yeah I agree, when in production ill be a lot leaner top and bottom.

Just testing at the moment how good these batteries are after being left in a dump for 6 months @ 0v!

Dave


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## john61ct (Feb 25, 2017)

My point is you really don't gain anything pushing the shoulders, so why do it at all?


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## DaveBlack (Oct 31, 2018)

Because I am testing ;o)

Next update is not great.... the discharger I purchased ignored the low V setting of 36v (3v per cell * 12). Not only did it completely flatten the battery to 0v - it caught fire in the process!

I mean proper fire, I can only assume it caught fire and perhaps then shorted the battery killing it. All the batteries so far have taken charge and the BMS's are flashing green. However this one battery is now RED and checking the strings one of them is 0v against the others with V.

I think one of the cells has failed - probably due to the discharger failure. But until I test more I guess I might find out all these batteries will have cell failures due to the condition they were left in. 

Who knows, new discharger on the way!

Dave

p.s. I didnt leave it unattended - but was not monitoring the Voltage. First I knew was smoke and fire and a dead battery.


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## boekel (Nov 10, 2010)

Green light is good! seems like the batteries van disconnected internally?

if it has been discharged too deep, the light flashes red.


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## DaveBlack (Oct 31, 2018)

boekel said:


> Green light is good! seems like the batteries van disconnected internally?
> 
> if it has been discharged too deep, the light flashes red.


Yeah does appear so - I think the light is flashing red due to one string reading 0v even after charging.

;o( But 29 batteries with green lights is still good! (at the moment lol)

Dave


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## DaveBlack (Oct 31, 2018)

Sorry for the delay in updating, fun and games getting another battery discharger...

So have tested multiple times one battery, charging @ 3.65v per s until current drops to below 0.1c.

Discharging to 3v per s, is generating about 400wh of power - these are rated at 1151wh.

So clearly this one is not happy and has degraded significantly.

Might sound obvious - but it is giving out as much power as it is taking to charge. it is not as if it is taking a normal amount of time to charge (10 hours @ 3amp) and losing that - it simply has reduced capacity.

I have just finished charging this one at 3.9v per s - the BMS seems happy. Ill see if that generates any more storage, probably not.

Ill have to test all of these to see what status they all are. Id like at worst 50% from them, otherwise they are not that much greater than lead acid and are going to be a headache to balance!

Dave


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## DaveBlack (Oct 31, 2018)

I think these batteries are going to be the death of me.

So battery discharger number two worked long enough to discharge a couple more batteries. Then caught fire again, cheap china cr*p is plain dangerous.

Has anyone got any decent products that can discharge and record the energy for around 40v @ 3a or more? 

Battery number 2 and 3 had about 60% capacity, which rose slightly when recharged and tried again. But then was pretty stable.

With 30 of these I am going to be here all year working out which ones (if any) I can use!!!!


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## pdove (Jan 9, 2012)

DaveBlack said:


> Has anyone got any decent products that can discharge and record the energy for around 40v @ 3a or more?



http://store.evtv.me/proddetail.php?prod=revolextrix

http://store.evtv.me/proddetail.php?prod=250wresistor


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## DaveBlack (Oct 31, 2018)

Not high enough voltage unless I am reading wrong?

Dave


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## pdove (Jan 9, 2012)

DaveBlack said:


> Not high enough voltage unless I am reading wrong?
> 
> Dave



Input voltage: 10-32VDC,


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## DaveBlack (Oct 31, 2018)

My lifePo's are 12s - 36v is pretty much empty. They operate between 36v-40v

Dave


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## [email protected] (Nov 1, 2018)

Hello every 1 hope ye all doing good and achieving your projects. I am in need of U-Bms-LV for my U27-12XP Valence batteries any 1 selling would be great 
Thanking you.
Usman.


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