Charger voltage too high for battery pack w/bms?...help

[scoot-e]

Ok, maybe a dumb question but...if I were to charge a batt pack with a charger that is higher voltage than the pack would the bms manage the higher voltage and limit it or would it wreck the bms and/or batteries?

1) I bought a 12s5p (2ah 3.7v nominal cells at 44.4v nom / 50.4v max charge) lithium ion pack and a compatible 45a bms and a charger
Problem is the charger I received states 48v on a small sticker on the front of the charger that seems like it was slapped on after the fact (but if correct the voltage would already be too high potentially for my pack as it would be a 13s charger with a 12s pack) but the "official" specs sticker on the back of the charger reads "output: 57.6v dc 3a"...

Normally I would assume if I didnt have a bms and was simply charging a battery pack directly that the charger should match as closely as possible to the batt specs but since I have a bms attached I was sure how it affected the scenario if at all...

 

[999zip999]

I wouldn't use that charger. Did you check it with a voltmeter ? 12X4.2v - 50.4v no magic. It will over charge your battery.
That charger might be for 14s lipo or 16s lifepo4. Need more info. Where you get it and what is it for ?

 

[NeilP]

It will over charge your battery.

if the battery has a BMS, then it can't overcharged the battery, since as soon as a cell reaches a critical voltage then the BMS will 'disconnect' the charger from the pack.

I can't say it is advisable, in case the BMS fails, but I regularly charge my 20s pack with a CC charger that has an open circuit voltage of 100 volts. You just need to monitor the output voltage very carefully, cell voltages too. As it is a CC charger, mine will only output the set current, so 20 amps...but it will not cut out at my 20 s pack required voltage, it will keep going to 100 volts. SO need to monitor.

Depending on your charger and BMS you will probably be just fine as long as you stay with it and monitor pack and cell voltages But more info needed to be sure.

 

[tmho]

I will be interested in that charger if you do not want it and would like to sell it cheap.

 

[dogman dan]

Find out what voltage the charger is actually putting out. Get a voltmeter if you don't have one.

Yeah, it will certainly try to overcharge your battery. And the bms should stop it.

But it might charge faster than it should at the end, causing the bms to allow some overshoot. Then the bms will bring the voltage back to what it's set for.

I'd say you could use it carefully for a very short time, watching what happens at the end with a voltmeter.

For damn sure, get a properly set charger ASAP. It might be possible to adjust it, and if so, it may have been adjusted regardless of what is written on it. So check it, and find out what voltage the charger is actually putting out.

 

[dnmun]

57.6V is the correct voltage for a 16S lifepo4 pack with a BMS using 3.60V as the balancing voltage which is now the standard balancing voltage for lifepo4.

there is no way to answer your questions without real info and there are no pictures to try to figure out what you have. we do not even have the actual output voltage of the charger. you need to buy a voltmeter from harbor freight or someone else cheap.

do you have a data sheet for the BMS? do you know for certain that it is 12S?

 

[friendly1uk]

What bms?
Mine wouldn't like it. It would charge to fast at the end of the cycle giving little time for balancing. If the balance currant is low and pack comparatively large, then limiting balance time would be bad. Charging would always end with a hvc situation, following which my bms will shut down and won't balance in that ov idle state.

The charger is most likely adjustable. Any electrical repair shop should be able to do it. That is why it has two ratings. A maximum and the additional sticker stating the actual. 12s is odd though, they might not of carried a 44.4v sticker so it got the 48v one regardless. It could test fine. Anyone that can work a voltmeter could check that.

 

[999zip999]

Yes it's not good. You might think on paper it would work.over time, thinking the cheap bms that comes with the battery. You will be buying a new battery. One cell will be 4.35v and one cell will be 3.85v. It will be charging to fast at to high a rate for the cells and bms. It would get so far out of balalnce after time. Try it and see what your battery balance would be after a month of use. Who wants a 2 month battery.
A 50v charger would give peace of mind. What charger do you have ? Is it adjustable ( inside ? ). Do you have a voltmeter ? Important question.

 

[scoot-e]

Thanks all! I will post pics shortly as well as test the charger with a voltmeter...duh, should have tried that first to confirm...

So the consensus is basically that it might work only because the BMS might limit the voltage in but it might be hairy to do so for various reasons including BMS failure or might provide a little too much juice and over time cause imbalance issues. Fair enough, I haven't and don't plan to use that charger with it anyway but was just curious as I'm not an expert with packs that contain BMS units.

It's a no name black plastic charger and attached metal 3 prong XLR standard connector and only has the specs I provided - it's not a greentime aluminum shell style though, it's just a small squarish/rectangular black plastic charger. I believe it probably is for a 16s based on the rear sticker and the company was a fly by night ebay seller that no longer exists and I bought as part of several different packs to test out.

Although I know the batts from a spec sheet (by the way, has anyone heard of "LGDAMF11865" cells before?? I couldn't find them on any online searches or the batt test charts people have linked to here or on any LG sites. The spec sheet seems authentic but I'm sure it's easy to forge or to manipulate in photoshop but I'm reading the label printed right on the cells themselves in the pack - let me know if anyone knows anything about these. They are listed as lithium ion 18650 cells at 2,150ah each and standard 3.7v or so ) they didn't have or send any bms spec sheet/instruction sheet and the only writing on it states "45a and some Chinese writing and a "10a", "RoHS" which is standard, and a "12" which I assume is the 12s but those are the only writing in English on the bms... so at least that seems in the range as I'm only pulling 35a at max hill climbs. But like I said the bms and batts seem to charge fine with my Supower greentime style 12s 4a charger so at least that is working out. The bms doesn't look like the Supower style bms units so I have no idea where it's from or anything else about it. It does have an aluminum shield/plate that's cut out to the same size as the bms circuit board, and it covers the top of the bms and then the shrink wrap (which I peeled back to have a look) it covering the plate.

I haven't used the charger with this pack yet, but I do have another pack that came with a greentime style aluminum shell with internal fan (from Supower) and is a 12s and 50.4v max charger which I did use with this pack and attached bms and it's working just fine. I peeled off the blue shrink wrap on the 18650 pack and confirmed there are 60 cells (12s x 5p = 60 cells) so it's def 12s5p or 44.4v nominal (and of course tested with an rc style watt meter as well to confirm.)

Thanks again for the feedback and yes the charger is for sale TMHO if you want it pm me and we can work out the deets

 

[999zip999]

Good luck.

 

[NeilP]

Just adjust the voltage down a bit, should not be difficult, probably 2, maybe 3 pots inside,

Mark them first, and wind them all the way one way, counting the turns or proportion of turns, so you can reset to same position. Do this when POWERED OFF, make notes of original positions, then return before powering on.


Regarding using it as is. Dogman pretty much has it exactly as I was saying. Try it carefully.

But go and get yourself a cheap meter if you are tight for cash. Or if you like good tools and want accurate quality, go for an expensive Fluke 87 III meter. They come up on e-bay.
I have both, a good Fluke and a pile of cheapo meters, again, e-bay. They sell from China, for less than the 9v batteries cost to power them.



The cells you talk of sound like standard no name 18650's . Nothing special about them, easily available, various qualities like any cells.

 

[dogman dan]

Yup, check what voltage you have, then if too high, see if the charger has adjustable voltage or not. Really cheap chargers won't have the pot. It's quite possible you got sent a lifepo4 charger, based on the voltage written on the box.

Look for a tiny screw on top of a part, right by the wires that go to the battery on the chargers board. That will be the V adjust pot if you have one.

 

[NeilP]

Meters

If you have the money, got for one like this:

http://www.tester.co.uk/fluke-87-5-eur-digital-multimeter

http://www.ebay.co.uk/itm/Fluke-87-111-true-rms-multimeter-/301327803929?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item4628896619



Otherwise, the other end of the scale:

http://www.ebay.co.uk/itm/DIGITAL-LCD-MULTIMETER-VOLTMETER-AMMETER-VOLT-OHM-METER-VOLTAGE-TESTER/231342916478?_trksid=p2047675.c100011.m1850&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D25401%26meid%3D59b0e0d2a06b4e098b2ab73083428412%26pid%3D100011%26prg%3D10670%26rk%3D5%26rkt%3D10%26sd%3D320715786271


I bought 10 like the cheap ones, all work, all accurate enough. I keep one in each car, one at home, one at Dads, One under the bed..and dotted around the workshop. just order 10

 

[dnmun]

if it is lithium ion or lipo then you need to find out how many cells in series and then calculate the charging voltage. do you have a picture and can you post up a picture of the BMS and the pack?

 

[made_in_the_alps_legacy]

Hi, you are for sure in good hands following dogman and dnmun advices: they really guided me with great help along a similar issue :
http://endless-sphere.com/forums/viewtopic.php?f=14&t=63055
(mine was initially undervolted, then overvolted manually and the BMS kicked in to protect the battery, then tuned right to 54.6V for a 13s Li Ion, which was initially sold to me as a LiPo)
I also learned a lot along the endless sphere wiki.

good luck

 

[tmho]

I have pm you yesterday. The pm is now in the "Outbox" but not in the "Sent messages". I am not sure whether the pm has reached you or not.

 

[NeilP]

It stays in Outbox till they are read.

 

[scoot-e]

Ok, finally had a chance to take pics and do some tests with the charger (and some others I have.)

I bought this cheap Harbor Freight volt meter for $6:
http://www.harborfreight.com/7-function-multimeter-98025.html

The bms (12s 60a max) is from Supower:
http://www.batterysupports.com/44v-48v-504v-12s-60a-12x-36v-lithium-ion-lipolymer-battery-bms-p-270.html

The batts are cheap Turnigy lipos, 8 packs of 3s 5ah 20c from Hobbyking (4 packs in series and connected in parallel to another 4 packs in series to get the total 10ah):
http://www.hobbyking.com/hobbyking/store/__9184__Turnigy_5000mAh_3S_20C_Lipo_Pack.html

 

[NeilP]

110 V !!!!!!
Are you sure you are measuring the output !!!

I can see a fire happening soon if that is true.


A proper LiPo charger when open circuit not put out more than pack final voltage.

If that is true, don't use any of them again


Test your voltmeter too. Measure the voltage aid a few standard AA 1.5volt and PP3 9volt batteries , check car battery for about 12 volts

Be very careful and try testing mains voltage with the meter set to AC and see if that reads corrrctly.
If you have 3 chargers and they all read that high, then they are either all faulty or it is a meter issue,

 

[999zip999]

K.I.S.S is as clear as it gets. You need a charger that stops at about 50.4volts depending on your B.M.S. Don't think about getting away with these tomorrow or today. Becareful.
A barbeque or brick charging station with smoke vent. As this charging method will need it.
Use simple math 12x4.2=50.4v maybe a little more to trip B.M.S.

 

[dnmun]

something is so wrong here this guy has to stop before he screws up major.

you need to post up a picture of the charger and where you measured the voltage. do not try to charge with these chargers until it is clear what happened and we can look at the pictures you produce.

 

[scoot-e]

Realized I was an idiot and measured on the wrong setting...wasn't using the dc setting on the volt meter
Will retest and take pics...uggh
Two of the 3 chargers (rated for 48v) showed 49v and 54v respectively...at least much closer to expected

 

[999zip999]

Charge to 50.4 maybe charger at 51v to trip bms. Just quessing on bms for tripping max. voltage. I wouldn't use 54 volt charger. Maybe charger has an adjustment inside ?

 

[dnmun]

what is tripping of a BMS?

 

[scoot-e]

Ok, here's pics of 2 of the chargers - the greentime style (silver rectangular shape) that is 4a and when tested with the voltmeter shows 49v dead on for my 12s pack (44.4v nominal charge / 50.4v fully charged).

The 2nd charger is a generic black plastic charger listed as 48v and 2.5a (which I opened up - 4 easy screws) and I do not observe any pots/adjustable settings. The voltmeter shows 54v dead on when plugged into the wall.

Little concerned about the 54v (which is sold as a 12s charger) because 50.4 is all the batteries should be at max (4.2v per cell) and when I use my Hobbying RC wattmeter immediately after unplugging the battery pack when finished from it's 2 hr charge it reads 54v and then quickly, like within 3 seconds, floats back to 50v and stays there so maybe the bms is controlling the overage from affecting the pack but I'm afraid to leave the charger connected for longer than 2 hrs and leave the house in case it actually over charges the pack, (as opposed to the 49v silver greentime charger which is right on and doesn't seem to have any issues) - the black charger on the back label says:
Output voltage rated dc - 48v
qual charging voltage - 59v
floating charge voltage - 55v
Output current 2.5a