Have you measured the voltage of your lifepo4 battery fully charged ??? Please read
01-05-11, 09:18 PM
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Have you measured the voltage of your lifepo4 battery fully charged ??? Please read
Has anyone here checked their lifepo4 battery voltage IMMEDIATLEY after your charger says its fully charged ?
Im wondering what voltages you are getting out of a fully charged lifepo4 battery for a 36 volt and 48 volt setup...
It seems like there is alot of opinions on the amount of volts per cell to put into them...the safe range seems to be between 3.6 V - 4.1 V per cell...
if 4.1 V per cell is acceptable, then I would think it is important to have a charger that can pump 4.1 Volts into each cell......if the charger can only charge the lifepo4 to 3.6 - 3.7 per cell...then one would be losing a fair amount of capacity...
.5 less per cell...in a battery that has 16 cells....is another 8 FULL volts
so we can see the huge advantage of having a charging system that equally and consistently will put a full charge of 4.1 Volts per cell...instead of 3.6 Volts per cell.
here is a vendor selling a lifepo4 charger for a 48 volt lifepod battery pack..
https://cgi.ebay.com/Intelligent-2A-C...item4ce9222160
Now, notice the max charging voltage is 58.2 volts...
If we are supposed to be able to put 4.1 Volts in each cell without any fear of damaging the cells , and to get the most capacity ...then this charger needs to be able to put out at least 65.6 Volts...{ 16 cells x 4.1 volts **
so we can see theres a substantial difference here..if one is trying to achieve most capacity on a full charge , without damaging the lifepo4 battery....
from some of the articles im reading...a fully charged lifepo4 battery , right off the charger should read 65.6 Volts....so if the charger can only get the battery to a total capacity of 58.2 volts...we arent getting the most out of our lifepo4 batterys ...correct ?
Does anyone know of a vendor selling a charger that will fully and safely charge and equalize a 48 volt lifepo4 battery ?
Im wondering what voltages you are getting out of a fully charged lifepo4 battery for a 36 volt and 48 volt setup...
It seems like there is alot of opinions on the amount of volts per cell to put into them...the safe range seems to be between 3.6 V - 4.1 V per cell...
if 4.1 V per cell is acceptable, then I would think it is important to have a charger that can pump 4.1 Volts into each cell......if the charger can only charge the lifepo4 to 3.6 - 3.7 per cell...then one would be losing a fair amount of capacity...
.5 less per cell...in a battery that has 16 cells....is another 8 FULL volts
so we can see the huge advantage of having a charging system that equally and consistently will put a full charge of 4.1 Volts per cell...instead of 3.6 Volts per cell.
here is a vendor selling a lifepo4 charger for a 48 volt lifepod battery pack..
https://cgi.ebay.com/Intelligent-2A-C...item4ce9222160
Now, notice the max charging voltage is 58.2 volts...
If we are supposed to be able to put 4.1 Volts in each cell without any fear of damaging the cells , and to get the most capacity ...then this charger needs to be able to put out at least 65.6 Volts...{ 16 cells x 4.1 volts **
so we can see theres a substantial difference here..if one is trying to achieve most capacity on a full charge , without damaging the lifepo4 battery....
from some of the articles im reading...a fully charged lifepo4 battery , right off the charger should read 65.6 Volts....so if the charger can only get the battery to a total capacity of 58.2 volts...we arent getting the most out of our lifepo4 batterys ...correct ?
Does anyone know of a vendor selling a charger that will fully and safely charge and equalize a 48 volt lifepo4 battery ?
01-05-11, 09:28 PM
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My V1 Ping Battery Charger will bring a 16 pouch cell Ping battery to 60.5 volts. 3.78 per cell.
My V2 Ping Battery Charger with the V2 BMS will bring a 16 pouch cell Ping battery to 58.7 volts. 3.66 volts per cell. With all LEDS lit up.
Both of these levels represent some degree of extraneous "surface charge" which is quickly dissipated when the batteries are plugged in, whence the operating voltage in both cases drops to about 53.4 volts.
These are nominal 48 volt battery packs.
I believe the lower level in V2 is more close to "as high as necessary". 4.1 volts is generally too high for a LiFP04 cell. I believe this 4.1 level is the upper safe level for a LiPO battery.
The V2 ping batteries are definitely "fully and safely charged and equalized" at 58.7 volts after the all the LEDs light up.
I believe that ebay charger is probably rather high for a 15 cell LiFP04 cell pack. (3.88 per cell). But not extremely too high.
My V2 Ping Battery Charger with the V2 BMS will bring a 16 pouch cell Ping battery to 58.7 volts. 3.66 volts per cell. With all LEDS lit up.
Both of these levels represent some degree of extraneous "surface charge" which is quickly dissipated when the batteries are plugged in, whence the operating voltage in both cases drops to about 53.4 volts.
These are nominal 48 volt battery packs.
I believe the lower level in V2 is more close to "as high as necessary". 4.1 volts is generally too high for a LiFP04 cell. I believe this 4.1 level is the upper safe level for a LiPO battery.
The V2 ping batteries are definitely "fully and safely charged and equalized" at 58.7 volts after the all the LEDs light up.
I believe that ebay charger is probably rather high for a 15 cell LiFP04 cell pack. (3.88 per cell). But not extremely too high.
Last edited by chvid; 01-05-11 at 09:33 PM.
01-05-11, 09:35 PM
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Min/Max Voltage
LiFePo4 chemistry appears to have an absolute minimum voltage of 2.0V per cell and a maximum of 4.3V per cell. Moving outside these limits won't just shorten cell life - it's likely to cause immediate damage.
Maximum Cell Voltage... While the upper limit of the chemistry appears to be 4.3V per cell, manufacturers agree that reducing that limit will add cell life. Thunder Sky recommends charging to 4.25V to 4.3V per cell for a 2000 charge-cycle life.
im just sharing this info I found, which is from a very well know manufacturer of lipo/lifepo4 batterys...this company has been around for many years and is well known on the R/C circuit...the company name is Thunder Sky.
If we take the info being presented by this well known and respected battery manufacturer...they suggest 4.25 volts per cell for 2000 cycles....so 4.1 volts per cell should be quite safe to do..while allowing most capacity from the lifepo4 cells....3.6-3.7 volts per cell would now seem to be much lower useable capacity if one has a 36-48 volt battery with 12-16 total cells.
LiFePo4 chemistry appears to have an absolute minimum voltage of 2.0V per cell and a maximum of 4.3V per cell. Moving outside these limits won't just shorten cell life - it's likely to cause immediate damage.
Maximum Cell Voltage... While the upper limit of the chemistry appears to be 4.3V per cell, manufacturers agree that reducing that limit will add cell life. Thunder Sky recommends charging to 4.25V to 4.3V per cell for a 2000 charge-cycle life.
im just sharing this info I found, which is from a very well know manufacturer of lipo/lifepo4 batterys...this company has been around for many years and is well known on the R/C circuit...the company name is Thunder Sky.
If we take the info being presented by this well known and respected battery manufacturer...they suggest 4.25 volts per cell for 2000 cycles....so 4.1 volts per cell should be quite safe to do..while allowing most capacity from the lifepo4 cells....3.6-3.7 volts per cell would now seem to be much lower useable capacity if one has a 36-48 volt battery with 12-16 total cells.
Last edited by sunnyday; 01-05-11 at 09:47 PM.
01-05-11, 09:47 PM
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So is any manufacturer making a lifepo4 battery charger that will equalize and fully charge a
48 volt - 16 cell lifepo4 battery to 65.6 Volts at which point the charger then shuts off ?
48 volt - 16 cell lifepo4 battery to 65.6 Volts at which point the charger then shuts off ?
Last edited by sunnyday; 01-05-11 at 09:53 PM.
01-05-11, 09:52 PM
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My V1 Ping Battery Charger will bring a 16 pouch cell Ping battery to 60.5 volts. 3.78 per cell.
My V2 Ping Battery Charger with the V2 BMS will bring a 16 pouch cell Ping battery to 58.7 volts. 3.66 volts per cell. With all LEDS lit up.
Both of these levels represent some degree of extraneous "surface charge" which is quickly dissipated when the batteries are plugged in, whence the operating voltage in both cases drops to about 53.4 volts.
These are nominal 48 volt battery packs.
I believe the lower level in V2 is more close to "as high as necessary". 4.1 volts is generally too high for a LiFP04 cell. I believe this 4.1 level is the upper safe level for a LiPO battery.
The V2 ping batteries are definitely "fully and safely charged and equalized" at 58.7 volts after the all the LEDs light up.
I believe that ebay charger is probably rather high for a 15 cell LiFP04 cell pack. (3.88 per cell). But not extremely too high.
My V2 Ping Battery Charger with the V2 BMS will bring a 16 pouch cell Ping battery to 58.7 volts. 3.66 volts per cell. With all LEDS lit up.
Both of these levels represent some degree of extraneous "surface charge" which is quickly dissipated when the batteries are plugged in, whence the operating voltage in both cases drops to about 53.4 volts.
These are nominal 48 volt battery packs.
I believe the lower level in V2 is more close to "as high as necessary". 4.1 volts is generally too high for a LiFP04 cell. I believe this 4.1 level is the upper safe level for a LiPO battery.
The V2 ping batteries are definitely "fully and safely charged and equalized" at 58.7 volts after the all the LEDs light up.
I believe that ebay charger is probably rather high for a 15 cell LiFP04 cell pack. (3.88 per cell). But not extremely too high.
thanks for your reply...
according to Thunder Sky battery manufacturer, you are not getting a full charge on your lifepo4 cells. ..they claim 4.1- 4.25 volts per cell is safe and allows the most capacity to be delivered.
01-05-11, 10:05 PM
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look at this link : and scroll down to the bottom
https://www.electricmotorsport.com/st...zivan_ng-1.php
see the chart that says 48 volt
now look at the rated output of that charger....it will put out 67 volts...which would fully charge a 16 cell lifepo4 battery....
now , the price is $550....but maybe to get full benefit of these lifepo4 batterys, we need a hi grade charger, instead of the cheapy chinese ones that only charge the lifepo4 cells to 3.6 volts each ?
A good charger that will fully and safely charge your battery , and equalize all the cells properly, is VERY important....its one area where I expect to pay more for...to achieve best results.
https://www.electricmotorsport.com/st...zivan_ng-1.php
see the chart that says 48 volt
now look at the rated output of that charger....it will put out 67 volts...which would fully charge a 16 cell lifepo4 battery....
now , the price is $550....but maybe to get full benefit of these lifepo4 batterys, we need a hi grade charger, instead of the cheapy chinese ones that only charge the lifepo4 cells to 3.6 volts each ?
A good charger that will fully and safely charge your battery , and equalize all the cells properly, is VERY important....its one area where I expect to pay more for...to achieve best results.
Last edited by sunnyday; 01-05-11 at 10:08 PM.
01-05-11, 10:31 PM
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I've always charged my regular LiFePo4 batteries to 3.6 to 3.7 per cell.
I've always gotten the full AH rating of the batteries when doing that.
I've never needed to change the voltage higher or lower since it works so well.
I also always charged at a c/3 rate and discharge at a 1c rate. In 18 months of use, I still have 95% capacity of my two batteries.
My thundersky pack I always charge to 4v per cell and the same charge/discharge rate mentioned above with the same results.
I've always gotten the full AH rating of the batteries when doing that.
I've never needed to change the voltage higher or lower since it works so well.
I also always charged at a c/3 rate and discharge at a 1c rate. In 18 months of use, I still have 95% capacity of my two batteries.
My thundersky pack I always charge to 4v per cell and the same charge/discharge rate mentioned above with the same results.
01-05-11, 10:38 PM
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I've always charged my regular LiFePo4 batteries to 3.6 to 3.7 per cell.
I've always gotten the full AH rating of the batteries when doing that.
I've never needed to change the voltage higher or lower since it works so well.
I also always charged at a c/3 rate and discharge at a 1c rate. In 18 months of use, I still have 95% capacity of my two batteries.
My thundersky pack I always charge to 4v per cell and the same charge/discharge rate mentioned above with the same results.
I've always gotten the full AH rating of the batteries when doing that.
I've never needed to change the voltage higher or lower since it works so well.
I also always charged at a c/3 rate and discharge at a 1c rate. In 18 months of use, I still have 95% capacity of my two batteries.
My thundersky pack I always charge to 4v per cell and the same charge/discharge rate mentioned above with the same results.
from what ive read, thunder sky recomeends charging their lifepo4 batterys to 4.2 volts each.....so only charging them to 3.6 volts each should mean they are not being fully charged and capacity is being lost...ecspecially if you have 12-16 indiivdual cells
01-05-11, 10:57 PM
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Im sending out some emails...to try and find out the facts about this ....if each of the lifepo4 cells can be safely charged to 4.1-4.2 volts, then I would think it is advantageous to do that...unless its possible that charging them to 4.1 volts each cell , only results in each cell quickly discharging , in a matter of minutes, to 3.6 volts....and the 4.1 reading is just a float charge reading that quickly loses .5 volts each cell once it is taken off charge.
01-05-11, 11:01 PM
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Thunderskys are LiFePo4.
They are prismatic. They have a slightly lower energy density then regular LiFePo4 cells, hence the manufacturer usually says to charge to a little bit higher voltage which will only lower it's best case scenario of cycles by a little bit.
My "regular" LiFePo4 batteries are cylindrical. When I need to balance them, this is my usual process.....
I charge to 3.7 on a per cell basis, then wait a couple of hours and then charge to 3.6, once they hit 3.6 per cell, my "BMS/Charger" keeps the voltage at 3.6v and only puts out 300mA.
I won't bore you with the specific details but that's about it.
I always follow the manufacturer's recommendation and then charge to ~.1 below that.
They are prismatic. They have a slightly lower energy density then regular LiFePo4 cells, hence the manufacturer usually says to charge to a little bit higher voltage which will only lower it's best case scenario of cycles by a little bit.
My "regular" LiFePo4 batteries are cylindrical. When I need to balance them, this is my usual process.....
I charge to 3.7 on a per cell basis, then wait a couple of hours and then charge to 3.6, once they hit 3.6 per cell, my "BMS/Charger" keeps the voltage at 3.6v and only puts out 300mA.
I won't bore you with the specific details but that's about it.
I always follow the manufacturer's recommendation and then charge to ~.1 below that.
Last edited by Sangesf; 01-05-11 at 11:13 PM.
01-05-11, 11:05 PM
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so I would assume charging them to only 3.6 volts each cell, is undercharging them siginificantly ? and then if you have 16 cells in series for a 48 volts system...only charging them to 3.6 volts each cell should be a noticeable amount of capacity being unused.
01-05-11, 11:07 PM
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Sangesf...can you provide me a link to the lifepo4 charger you are using for your thundersky lifepo4 pack ? If you have a manufacturers link for here in the U.S. ...id like to see the price of their 48 volt lifepo4 charger....
01-05-11, 11:25 PM
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okay...then that coincides with the info I read by thundersky claiming the lifepo4 batterys can be charged to 4.25 volts each cell....
so I would assume charging them to only 3.6 volts each cell, is undercharging them siginificantly ? and then if you have 16 cells in series for a 48 volts system...only charging them to 3.6 volts each cell should be a noticeable amount of capacity being unused.
so I would assume charging them to only 3.6 volts each cell, is undercharging them siginificantly ? and then if you have 16 cells in series for a 48 volts system...only charging them to 3.6 volts each cell should be a noticeable amount of capacity being unused.
Not really. Did you see the graph yopappamon posted in your other thread? Almost all of the capacity of a LiFePO4 is between about 3.2v and 3.4v. The voltage is nearly flat from full charge to empty. That is part of why they are so desirable over lead acid. You might gain .05 ah by going to 4.2v but you shorten the life of the battery significantly.
01-05-11, 11:28 PM
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The charger I'm using was given to me by an electrical engineer friend of mine who "set it" to put out CC/CV of 47v/12a which is ~3.91v per cell.
When I need to balance the cells (about once a month) I use a single cell LiPo charger to charge to 4.2v each.
FYI mine are the 60AH cells.
I rarely go above 30ah usage in a day, and mostly about 15-20ah.. Once a week I do a 70 mile round trip and use up about 50ah.
When I need to balance the cells (about once a month) I use a single cell LiPo charger to charge to 4.2v each.
FYI mine are the 60AH cells.
I rarely go above 30ah usage in a day, and mostly about 15-20ah.. Once a week I do a 70 mile round trip and use up about 50ah.
01-05-11, 11:35 PM
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Not really. Did you see the graph yopappamon posted in your other thread? Almost all of the capacity of a LiFePO4 is between about 3.2v and 3.4v. The voltage is nearly flat from full charge to empty. That is part of why they are so desirable over lead acid. You might gain .05 ah by going to 4.2v but you shorten the life of the battery significantly.
so you think each cell should never be charged more then 3.6 volts ?
01-05-11, 11:36 PM
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Not really. Did you see the graph yopappamon posted in your other thread? Almost all of the capacity of a LiFePO4 is between about 3.2v and 3.4v. The voltage is nearly flat from full charge to empty. That is part of why they are so desirable over lead acid. You might gain .05 ah by going to 4.2v but you shorten the life of the battery significantly.
I charge to 3.91 max. TS says 4.0 And can safely do up to 4.2.
LiFePo4 large capacity (20ah and up) prismatic cells can be charged to a slightly higher voltage (4.0v as compared to 3.65 for smaller ~1.1ah-2.2ah cylindrical ones) for various technical reasons, which I won't get into.
It can't hurt to only charge small ones to 3.65 and large ones to 3.9.
01-05-11, 11:40 PM
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Sangesf..I sent you a private message...
it seems like there is alot of conflicting opinions about this subject....
but one thing is for sure, I gotta get me a new 48 volt battery charger...and I want one that fully charges and equalizes my lifepo4 pack for optimum performance,.
it seems like there is alot of conflicting opinions about this subject....
but one thing is for sure, I gotta get me a new 48 volt battery charger...and I want one that fully charges and equalizes my lifepo4 pack for optimum performance,.
01-05-11, 11:44 PM
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Sunny was worried he wasn't going to get full capacity without going to 4.2v, so I would assume he's talking about doing it more than once a month.
Not if you do it only once a month.
I charge to 3.91 max. TS says 4.0 And can safely do up to 4.2.
LiFePo4 large capacity (20ah and up) prismatic cells can be charged to a slightly higher voltage (4.0v as compared to 3.65 for smaller ~1.1ah-2.2ah cylindrical ones) for various technical reasons, which I won't get into.
It can't hurt to only charge small ones to 3.65 and large ones to 3.9.
I charge to 3.91 max. TS says 4.0 And can safely do up to 4.2.
LiFePo4 large capacity (20ah and up) prismatic cells can be charged to a slightly higher voltage (4.0v as compared to 3.65 for smaller ~1.1ah-2.2ah cylindrical ones) for various technical reasons, which I won't get into.
It can't hurt to only charge small ones to 3.65 and large ones to 3.9.
01-05-11, 11:57 PM
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Sunny isn't using TS prismatic cells / battery.
So the 4.0-4.2v once a month part was not meant for him but a generalization for large capacity prismatic cells.
He's using a duct tape / cylindrical pack battery.
He should only charge to 3.65 per.. That was my recommendation.
If you read, I stated the difference between TS and Cylindricals.
P.S. All cells on all my batteries have been specifically tested and used because they all have voltages in the 3.25v - 3.30v range during 85%-90% of full capacity usage mainly because I only pull 1C continuous max.
(e.g. When I do my 70 mile trip, from 5 minutes into riding until the end of my run, my battery shows a voltage of 39.0v-39.6v [36v Battery])
So the 4.0-4.2v once a month part was not meant for him but a generalization for large capacity prismatic cells.
He's using a duct tape / cylindrical pack battery.
He should only charge to 3.65 per.. That was my recommendation.
If you read, I stated the difference between TS and Cylindricals.
P.S. All cells on all my batteries have been specifically tested and used because they all have voltages in the 3.25v - 3.30v range during 85%-90% of full capacity usage mainly because I only pull 1C continuous max.
(e.g. When I do my 70 mile trip, from 5 minutes into riding until the end of my run, my battery shows a voltage of 39.0v-39.6v [36v Battery])
Last edited by Sangesf; 01-06-11 at 12:11 AM.
01-06-11, 12:58 AM
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I agree with your recommendation Sangesf, cylindrical LiFePO4 cells should be charged to 3.65V +/- .05V to ensure the life cycle expectancy of the cells. Although the same basic chemistry of the cells is the same between cylindrical and prismatic cells, the slight differences in the percentages of the cathode composition results in the differences between the two manufacturers recommended charging voltages, 4.2 vs. 3.6
For what it is worth, the basic chemistry make-up is designed to take the 3.65V charge through the 3 phase CC/CV charging method.
For what it is worth, the basic chemistry make-up is designed to take the 3.65V charge through the 3 phase CC/CV charging method.
01-06-11, 07:37 AM
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Okay...so for these chinese duct tape lifepo4 packs...3.65 is the max each cell should read, hot off the charger......
appreciate the info.
appreciate the info.
01-06-11, 08:45 AM
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anyone ever buy one of these chargers :
https://www.cycle9.com/c9store/electr...atteries-p-258
if you read the info on that charger, it claims that the charger is specifically made to work with the BMS and ensure all cells in the lifepo4 battery get a full charge....
and then it claims that most other chargers do not have the ability to do this because the other chargers will shutoff when it gets a signal from the BMS , and this is how some cells do not get charged to full capacity..
I dont know if their claims are bullcrap or not...LOL...
I noticed they dont list the max voltage output of the charger....
https://www.cycle9.com/c9store/electr...atteries-p-258
if you read the info on that charger, it claims that the charger is specifically made to work with the BMS and ensure all cells in the lifepo4 battery get a full charge....
and then it claims that most other chargers do not have the ability to do this because the other chargers will shutoff when it gets a signal from the BMS , and this is how some cells do not get charged to full capacity..
I dont know if their claims are bullcrap or not...LOL...
I noticed they dont list the max voltage output of the charger....
01-06-11, 02:40 PM
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Sure thing, glad to help! ;-)
Interesting claim about the charger, I cannot comment one way or the other, but personally in the BMS vs No BMS controversy that many are involved in in the EV arena, I am a believer in having a quality BMS so that the cells will be protected with either a frugal charger purchase or a high priced charger purchase.
In the picture of the charger that they provide, it is difficult to make out the DC output voltage, but it appears to be somewhere between 42.?/58.?V, but is a little blurry to actually see the numbers.
01-06-11, 10:12 PM
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A charger with a selector switch for 36V or 48V for $99 with the other amenities and features it has is a pretty good deal IMHO! Looking forward to see what you find our Sangesf!
sunnyday, on the other thread you mention which would be the best output for amps for the charger. I am posting here instead of there because this thread is dealing mostly with charging and energy of a pack and didn't want to get similar threads going here! That being said, there are a few things to consider when choosing a charger.
* Be sure to know, or at least try and find the battery charge rate, either actual max amps for charge or the C rating for charging the pack it will determine how much of a fast charge the cells are designed to take.
* Without knowing your actual set-up, a good rule of thumb to follow for LiFePO4 is 1.4 * Pack Ah / Output Amp of charger = time in hours to completely charge a battery pack that is 80-90% discharged.
sunnyday, on the other thread you mention which would be the best output for amps for the charger. I am posting here instead of there because this thread is dealing mostly with charging and energy of a pack and didn't want to get similar threads going here! That being said, there are a few things to consider when choosing a charger.
* Be sure to know, or at least try and find the battery charge rate, either actual max amps for charge or the C rating for charging the pack it will determine how much of a fast charge the cells are designed to take.
* Without knowing your actual set-up, a good rule of thumb to follow for LiFePO4 is 1.4 * Pack Ah / Output Amp of charger = time in hours to completely charge a battery pack that is 80-90% discharged.