Question Re: Charger Voltage Falling From 42.5 to 16 Volts

[WonderProfessor]

Greetings, Friends. Once again, we come for succor and aid in time of need. This question concerns a battery and charger combination. The battery is a 36-volt, 20-amp, 3C, lithium-iron-phosphate battery and seems to be working fine. It is the charger that is giving me fits and thoroughly confusing me. The chargers says that it should be producing 42.5 volts and that is what is does ... sometimes. Other times, it produces 16 volts and on one occasion, it was producing 20 volts. Allow me to elaborate:

This battery does not have a visible BMS as does my other battery (a Ping 36-volt, 20-amp hour 1C lithium-iron-phosphate battery) so you do not know if it is at full capacity or not just by looking at it. After a ride, when you are sure that the battery is not completely filled, you plug in the charger. The charging light is supposed to go from green to red and that signals that the charger is charging the battery. Usually, it does not go from green to red and then you have to unplug the power cord to the charger, wait a few moments for the green light to completely go dark, and then re-plug the power cord into the charger. The green light goes from green to red and the charger starts then charging the battery. I thought to myself that something is definitely weird here. We need to investigate further.

I took out the multi-meter and started doing some measurements. After the charging light had gone from red to green, signaling that the battery was at full capacity, the voltage read 16 volts. (This was very confusing to me as I thought that the charging voltage always remained the same and that it was the amperage that changed when the battery was filled to capacity.) I did the same procedure discussed above to get the charger charging again, namely, I unplugged power cord to the charger, waited until the green charging light went dark, and then re-inserted the power plug to the charger. The green light came back on and this time, the voltage now read 42.5 volts. I plugged the charger into the battery and the charging light went from green to red, signaling that the charger was charging the battery. I let it charge for a couple of hours and returned. The charging light had gone from red back to green, signaling that the battery was at capacity (or, at least, the charger believed that the battery was at capacity). I measured the voltage and again, the voltage from the charger had again fallen to 16 volts. Again, I unplugged the power cord to the charger, waited until the green light had gone dark, and then re-inserted the power cord to the charger, and again, the voltage from the charger read 42.5 volts.

My question is: Is this normal? Is this the way some battery chargers work? Or is the charger faulty? Could I use my other charger that I use for my 36-volt, 20-amp hour, 1C Ping lithium-iron-phosphate battery? It produces 45.2 volts. (And it has never seemed to produce anything other than 45.2 / 45.3 volts.) Since this charger that came with the bike produces 42.5 volts (when it is working) and the other charger produces 45.2 volts, are they incompatible? Will 45.2 volts be too much voltage for the battery?

Some background: I purchased this bike used just a few weeks ago. It is a real gem. It is a Vision R30 recumbent with a bitchin' full-length Zipper fairing. (Vision is out of business but they made some very nice ‘bents. This was one of their lesser popular models but I think it was one of their best. For a recumbent, it is very light and has a comfortable and stable ride.) It has an Ecospeed Electric Mid Drive (EMD) Unit and is very, very fast. The battery is a Point 1 Tech, 36-volt, 20-amp hour, 3C lithium-iron-phosphate battery. There are no identifying markings on the charger except for a model number, KP4502JL, which does not bring anything up in either Google or Yahoo. Aside from the charger strangeness, I really feel that I got a helluva' deal since the Ecospeed EMD alone would cost far more than what I spent for the entire bike. And I knew it was only a matter of time before I wanted something far more powerful than my current e-bike. (http://endless-sphere.com/forums/viewtopic.php?f=4&t=11339)

Many thanks for in advance any and all ideas, comments, suggestions, etc.

Respectfully submitted,

Frank Paiano
San Diego, California, USA
http://www.wonderprofessor.com

 

[theRealFury]

Well the most important thing that you are not measuring or telling us about is what voltage the pack is at when it stops charging. When the red light goes to green it doesn’t really matter what voltage you see from the charger any more (an easy way to stop a battery from charging is to deduce the supply voltage below the battery voltage so no current can flow any more so it may be exactly what the charger is doing). You need to measure your battery, if it’s a 36v battery then fully charged you should see 41.8-42v hot off the charger (my 36v reads 41.96 when unplugged).

If your battery is showing much less than that then you have a problem. If your battery is fully charged then I wouldn’t worry about the voltage read from the charger after it’s knocked off.

On the subject of cycling the power and the charger restarting again that is easily explainable as long as you can confirm that the battery is indeed fully charged when it switches off. Basically you may have just a small circuit BMS in the battery that shuts off the charge when the voltage hits the preset HVC. Once it triggers the cut-off from the charger the battery voltage will start to slide down again towards ~41.6v. when you cycle the power to the charger it again reads the battery voltage and notices that it is below the charging termination voltage so starts to charge again, albeit very slowly because the two voltages are almost the same.. This can go on for 5-10 minutes before it again triggers the HVC and terminates the charge.

So, enough of my rambling: lol:, when the charger turns off, measure the battery voltage and if it’s much less than 42v then update the thread and we can begin troubleshooting the BMS/Charger :wink:

I hope that helps.

 

[WonderProfessor]

Thanks, RF. Ya' know, I did measure the voltage from the battery and it was 42 volts on the dot when the charger stopped charging. Sorry about not reporting that crucial information. So if I understand you correctly, it sounds as though it may be working just fine even though you have to unplug the power cord from the charger and the reinsert the power cord to the charger whenever you want to recharge the battery.

Thanks, again!

 

[theRealFury]

Thanks, RF. Ya' know, I did measure the voltage from the battery and it was 42 volts on the dot when the charger stopped charging. Sorry about not reporting that crucial information. So if I understand you correctly, it sounds as though it may be working just fine even though you have to unplug the power cord from the charger and the reinsert the power cord to the charger whenever you want to recharge the battery.

Thanks, again!

Ahh ok well in that case then everything sounds good. Sounds like your charger is similar to mine. Once it triggers HVC you have to cycle the power to it in order to get it to charge again. Doesnt usually pose a problem for me as i dont like to leave my charger plugged in when its not charging.

 

[dnmun]

there is not much info to work from. what are the cell voltages when it is charging? which cell is the high one? what charger are you using and does it actually shut off or is there something else happening? are there any pictures? what does the BMS look like and what voltage does it shut off at for the single cell HVC? what voltage does the high cell drop to before the BMS turns on the charging FET again? 42V is not charged.

 

[theRealFury]

42V is not charged.

Doh, the penny just dropped, its a LiFePo4 battery not Lithium Ion.... my mistake. so im guessing its a 12cell in series battery and if so this should have a fully charged voltage of 43.2v right? If the charger is terminating at exactly 42v and only putting out 42.5v when tested then could it be possible that its a li-ion charger and not a lifepo4 charger? Im sure it wouldnt damage the battery but would be slightly undercharging the battery and possibly not allowing balancing if thats the case right?

 

[WonderProfessor]

Many Thanks For Your Responses. I am beginning to get a clearer understanding. Attached is a photo of the charger. It is a bit confusing. On the far left side of the charger it boldly proclaims "LI Iron / LI Polymer" underneath the generic title of "BATTERY CHARGER." Next to this is given the model number KP4502JL and the specifications which are 100-120 VAC AC Input, 42.6 Vdc DC Output, 2 amps. Continuing to the right are the descriptions for the lights: LED 1 is only red and signals that the power is on. LED 2 is red when charging and green when the battery is charged. Below that is the description for the output wires. Now here is where the plot thickens. On the far right are three cautions. One of the cautions reads, "Charge only lead-acid type rechargeable batteries. Other types of batteries may burst Causing [sic] personal injury and damage." Hmmm. Obviously, someone did not proofread the labeling. Also, this makes me think that this charger was originally designed for lead-acid batteries and then simply labeled for lithium iron phosphate and lithium polymer batteries when really it may not be appropriate for lithium batteries with a BMS. (Pure speculation on my part given my level of expertise.)

I will try to answer the questions from dnmun to the best of my abilities:
What are the cell voltages when it is charging? Hell if I know!
Which cell is the high one? Hell if I know!
What charger are you using ... Model number KP4502JL and I can't find any documentation on the web regarding this charger.
...and does it actually shut off or is there something else happening? No, it does not shut off. The voltage goes from 42.5 down to 16 when the battery hits 42.0 volts.
Are there any pictures? Attached.
What does the BMS look like ... I do not see a BMS such as the one on my Ping battery. I assume it is inside the battery?
... and what voltage does it shut off at for the single cell HVC? Hell if I know!
What voltage does the high cell drop to before the BMS turns on the charging FET again? Hell if I know!

Note: The Hell-if-I-know!'s designate an area of expertise that is significantly higher than the abilities of Your Humble Servant.

From what I can glean, this charger really not might be appropriate for this battery. Can I use the 45.3 volt charger that came with my 36-volt, 20-amp-hour, 1C Ping battery? I have had it for almost 2 years now and it has been a real trooper. I have over 3,500 miles on my first e-bike and the battery has never given me any problems.

Again, Thank You All For Your Tremendously Helpful Responses! Together, we can help reduce our foolish reliance on fossil fuels. (In my case, it takes about 3/4 of a kilowatt of electricity for me to get to and from work instead of almost 2 gallons of gasoline.)

 

[docnjoj]

Hey Professor
You really need to find out if that battery has a BMS! Is this wonky charger the one that came with it? I use my Ping charger which is set about 45.6 volts and it seems to work fine on both 36 volt Pings we own. Also practice a bit with that multimeter since the experts here really need the info to diagnose correctly. I'm a doctor, not an electronics tech and even I know how to do some of this stuff! 8)
otherDoc

 

[theRealFury]

Right ok Professor,

In my eyes there are two senarios i can see that will help solve the riddle.

1) The battery is indeed LiFePo4 (the chemical name for Lithium Iron Phosphate) but the charger that has been supplied with it is a lithium-ion and lithium polymer battery charger (these batteries have a higher cell voltage than LiFePo4) and as such the battery is not getting a full charge.

2) The battery is infact a lithium ion / lithium magneese / lithium polymer battery with a charge termination voltage of 42v and as such the charger is doing its job correctly and everything is working fine.

The only easy way i can think of to find out what chemistry of battery you have is to run arround the block until you hit the low voltage cutoff on the batteries BMS and then once you do that stop and then check the battery voltage, if it reads 0 on the discharge leads then try to check the voltage at the charge port. if still nothing then plug the charger in and turn it on for just a few seconds then turn it off again and now you should be able to measure the voltage. I think it depends on BMS but if its somewhere round 35v then your probably looking at li-ion or li-polymer but if the termination voltage is around 30-32v then its more likely to be LiFePo4 i believe.

Unfortunately im no expert when it comes to batteries so hopefully someone with some solid battery knowledge can chime in on here and help you out some more but failing any imput from the gurus on here, i would do what i just suggested.

 

[WonderProfessor]

Thanks, Folks. The Saga Continues. I am fairly certain that the battery is a lithium-iron-phosphate battery because it says so right on the battery case. (Of course, it may be false advertising but I do not think so.) Therefore, given your information and explanations, the charger is probably the wrong charger for this battery! Aha!

Yours Truly is very apprehensive about actually opening the battery case. But if I did get up the nerve to do so, would I be able to determine if there is a BMS inside the battery? Would it say something like "BMS" on the BMS? (The Ping battery has a printed circuit board on the outside of the battery that lights up like a Christmas tree when the battery is completely charged. It is my understanding that this is the BMS.)

If the battery does not have a BMS and I continue to use the charger that was supplied with the battery, do I run the risk of ruining the battery?

If the battery does not have a BMS and I start using the 45.3 volt charger that came with the Ping battery, do I run the risk of ruining the battery?

If I get up the nerve to open the battery, what is the probability of me A) ruining the battery; B) actually knowing what I am looking at once I do manage to open it, and C) electrocuting myself?

(Don't worry about me. I am just brain-storming and typing whatever comes into my mind. During my next session with the psychiatrist, I will be sure to tell him all about it and ask about appropriate medications.)

Thanks, Again, Everyone!

 

[theRealFury]

Yours Truly is very apprehensive about actually opening the battery case. But if I did get up the nerve to do so, would I be able to determine if there is a BMS inside the battery? Would it say something like "BMS" on the BMS? (The Ping battery has a printed circuit board on the outside of the battery that lights up like a Christmas tree when the battery is completely charged. It is my understanding that this is the BMS.)

If you did open up the battery it should be fairly easy to see if there is a BMS and most boxed batteries have a BMS in there somewhere... basically if there is a circuit board in there then it is most likely a BMS, especially if it has rows of resistors or LED's (not all BMS's have lights to show that cell groups are fully charged as most of the BMS's are not meant to be seen). If all else fails just take some pics of the battery once you open it up and post on here for the tech guys to take a peek at.

If the battery does not have a BMS and I continue to use the charger that was supplied with the battery, do I run the risk of ruining the battery?

No, if you continue to use the current charger and your battery is a LiFePo4 battery then you are slightly undercharging it so the worst it will do is not allow a BMS to balance the cells so will lead to less capacity before the pack trips the LVC and turns off.

If the battery does not have a BMS and I start using the 45.3 volt charger that came with the Ping battery, do I run the risk of ruining the battery?

If the battery does not have a BMS, which is very unlikely and you do change to your ping charger there is a chance that you can damage te cells. I beleive ping adds an extra cell in series on his batteries compared to some of the competition so if your battery is either not the chemistry yo think it is or if there are less cells in series then you could overcharge the battery and damage some cells doing so.

If I get up the nerve to open the battery, what is the probability of me A) ruining the battery; B) actually knowing what I am looking at once I do manage to open it, and C) electrocuting myself?

A) Possible but not likely unless you go about it like a bull in a china shop :lol:
B) thats the hard part, if the BMS is clearly visible then you should be able to identify it without issue but if its hidden within the pack or covered in shrinkwrap or something then it might be harder to locate.
C) Well as much as i would love to say it wont happen you are dealing with a battery that is very powerfull so you will have to be carefull not to touch metal parts or bare sloder spots and things as it may lead to a shock. When i opened up my battery it was encased in plastic sheet on the 4 sides but teh ends were open and ware metal cells were visible so you just have to be carefull where you hold thats all. I wonder if a pair of marigolds will give you some protection haha

I say go for it, have a look inside and if any doubt take lots of pics and post on here so we can all have a look at what you got.

 

[docnjoj]

Yep! What he said!
otherDoc

 

[dnmun]

nothing to do for him until he can measure the cell voltages. BOL, pictures are really needed also.

 

[WonderProfessor]

Many, many thanks for all your help. I finally summed enough nerve to begin the process of opening the battery. After removing the cloth case, I took a couple of pictures (included). The battery is completely sealed. Imagine my relief! I am off the hook. I have no intention of trying to unseal the battery. Therefore, whether or not there is a BMS or what the high voltage on the HCV is or whether the FET is charging again after the FBI arrests the CIA for spying on the IRS, etc., etc., etc. will forever remain a secret (at least for the time being). Now that I know (1) the current charger should not harm the battery and (2) all I have to do is unplug the power cord to the charger and plug it back in again to get the battery to charge, I am happy.

And for that, Dear Friends, you have my eternal gratitude!

P.S. I had the bike up to 34 mph (55 kph) yesterday morning. It was great fun and it should reduce my 20-mile (32-kilometer) commute from 1 hour 20 minutes to around an hour or so.