55V charger safe for 13s 54.6v operation?

I just got a charger off eBay for 13s 48v li-ion cylindricals. The seller (victor studios) told me it was 54.6v output but the charger back label is telling me that it is 55V output 2.0A. I'm not sure if it is just rounding up or not.

But anyways, I wonder if it will be safe for use with Samsung 13s (18650-25Rs) which are rated at 4.2V fully charged = 4.2V x 13 = 54.6V. I mean, I wonder if that extra 0.4V overcharge could screw things up...


here's the charger: http://www.ebay.com/itm/Universal-Smart-2A-Charger-for-48V-13S-Li-ion-Lithium-Polymer-Battery-Pack-NEW-/300941980639?pt=Battery_Chargers&hash=item46118a33df

About Universal Smart 2A Charger for 48V(13S) Li-ion Lithium Polymer Battery Pack-New:

Describe

Intelligent charger designed for 48V (13 cells) Li-Ion Battery packs including Polymer Li-Ion and Cylindrical Li-Ion.
Worldwide input AC power from 100V - 240VAC.
Charging Current: 2000 mA (2.0 A).
Charging time = ( Ah rate of the pack x 1.5 ) / 2A charging current.
Built in IC to cut off power automatically when battery is fully charge.
Red LED show Battery charging and Green LED shows full.
one LED is always Green (battery symbol) indicate has AC power (also fan is running).
the LED with Sine wave symbol will turn RED indicating charging battery (Green = battery is fully charged).
Charging terminal : Standard Male DC Barrel Connecotr(OD: 5.5mm, ID: 2.1mm).
Dimension (LxWxH): 6.0"(152mm) x 2.5"(64mm) x 1.8"(46mm).
Weight: 14 OZ (392 grams).
Size: 6" x 3.3" x 2"

Net Weight: 16.00 oz

i map out the charge time, and set a timer to kill the power in case i get distracted, or in case it malfunctions and wants to overcharge.
the map is made by writing down charge voltage, time at each .1 volt, and amps.
then anytime i need to know how long it needs to charge, i match up the begin volts with the map, read the time to end, then set the timer.
so the charger voltage does not have to be trusted, YOU are in charge.

I also thought that the BMS is designed to shut off a charger? How would the BMS shut a charger off?

since there is no BMS, you will never know what the cell voltages are anyway. any cell can overcharge since there is nothing to protect them.

dnmun said:

since there is no BMS, you will never know what the cell voltages are anyway. any cell can overcharge since there is nothing to protect them.

Click to expand...

actually,I will be running BMS.

Hrrm... I did the math. the samsung cells are charged at 4.2v +- 0.05V. That means 0.4V / 13s = 0.03V. So it is within the tolerance of the spec.

I would put and extra set of sense wires on the pack for cell monitoring. Any cell. can run high bluck charging without a bms or balance charging. One cell could reach 4.4v and at 4.1v.

if you have a BMS to balance it to the 4.2V level it will be ok to use the 55V, if that is what it is. but you end up with 4.23V/cell which is still high. you can try adjusting it down to the 54.6V level on the trimpot inside.

Is this the "trimpot" you speak of (arrow in red, third picture)? Now how would one know how to adjust it so that it changes the voltages correctly?

I put my multimeter on the output leads and the voltages are bouncing all over the place, not sure why I can't get a steady DC voltage read off the charger charge port. So then how would I ascertain the correct charge voltage?

the voltage jumps around because of electrical noise or spikes in voltage on the output wires.

that cermet should do it.

Put a small load on it and check the voltage again--a 100w light bulb (110v) should work nicely.

If the charger is not adjustable, is this a case where a half dozen 1N5401 diodes in series added to the end of the charge wire would trim the final voltage down to 4.2 or below?

I actually don't have aligator leads to put it on a light bulb. i also don't have any 48v batteries lying around. Just a 36v pack.

also, i opened it up again and put the volt meter right at the solder joints of the output lines. that bypasses the cables right? the voltages are still bouncing.

i have another 36v(42v peak) charger that i bought from the same seller. it's different design(shape) and when i put the meter right at the output cables, i get a solid 42.1V. Not the (42.0v) as advertised on the sticker of the charger. Hrrm... i'm guessing if my voltmeter is off or that's really how it is...

NO! Not if you want your batteries to last. 4.2v max means 4.2v max. If you want your batteries to really last don't exceed 4.0v

3 and a half years later, we might be able to ask OP if you were right.

Why the thread necro?