What is the normal charge voltage on these batteries?

  • 1
  • Question
  • Updated 2 months ago
  • Answered
  • (Edited)
RECEIVED NEW ST 1500 LINE TRIMMER WITH A 2 AMP HOUR BATTERY PAK.   AFTER CHARGING BATTERY FIRST TIME THE VOLTAGE RIGHT OFF THE CHARGER WAS 58.5 VOLTS. THIS APPEARS TOO HIGH BECAUSE A LITHIUM ION CELL SHOULD NEVER BE CHARGED ABOVE 4.1 VOLTS AND I BELIEVE THE BATTERY PAK HAS 14 CELLS SO THE CORRECT FULL CHARGE VOLTAGE SHOULD BE AROUND 57.4 VOLTS MAX. JUST A FEW 1/100THS OF A VOLT OVER CHARGE CAN GREATLY REDUCE THE LIFE OF THE BATTERY PAK.  CAN ANYONE TELL ME WHAT THE NORMAL FULL CHARGE VOLTAGE OF THIS SYSTEM IS ?  THANKS FOR ANY HELP.
Photo of GARY

GARY

  • 70 Points

Posted 3 years ago

  • 1
Photo of Blue Angel

Blue Angel, Champion

  • 177,594 Points 100k badge 2x thumb
Official Response
Hi Gary,

If you look around the web you'll see that the normal charge voltage for most 18650 li-ion cells is 4.2V. In that case, 14 x 4.2 = 58.8V

Your question is a timely one... I just finished giving in to temptation and have the new 530 cfm blower in my garage, and happen to have noticed this little tidbit of info on the back of the box:



Ego is actually rating the battery at 58.8V maximum, and 56.0V nominal.

Another observation is with regards to volt meter accuracy, as in they're typically not all that accurate. As an experiment I just charged my new 2.5Ah battery and measured its voltage with two different volt meters:

Meter 1 = 57.4V
Meter 2 = 58.2V

Two meters, same battery, fresh off the charger, repeated three times.

A volt meter can be 1.0V off at 50V and still be within 2% accuracy, so unless you have a meter that's calibrated with a measurement uncertainty statement AND is traceable to a national standard, relying on it for fine 0.1V measurements at nearly 60V is not a good practice!

Sorry to get all analytical, but I work in a calibration/metrology lab and tend to carry that baggage around with me... :-)

Also, just in case you're worried about Ego over-charging their cells, take a look at this video and note that Echo, who also use banks of 14 18650 cells, are charging theirs to a higher voltage than Ego is:

http://youtu.be/lRdBS9oFUXc

That guy has several videos involving Ego and Echo batteries. If you're a battery nerd like I am you should enjoy them! ;-)
Photo of John Pearson

John Pearson

  • 518 Points 500 badge 2x thumb
love that battery nerdery!
Photo of Burugee

Burugee

  • 264 Points 250 badge 2x thumb
I also have 3 batteries and 1 x fast charger 1 x regular charger. Using both chargers, batterries seems to get to the same voltage of 58.2V. I tried different combinations of charging, and consistently same final voltage on both chargers on different batteries of varing capacity. (2.5Ah vs 7.5 Ah).
Photo of Blue Angel

Blue Angel, Champion

  • 177,594 Points 100k badge 2x thumb
Sounds like your meter reads the same as mine (meter #2 above) which is the Fluke I took so long to talk myself into buying. Glad I did!!!
Photo of John Cole

John Cole

  • 496 Points 250 badge 2x thumb
On full power how long should I get with my strimmer ( the pro one with the handles) form the 7.5 AH battery the 5AH battery and the 4 AH battery?
I ask because the batteries don't seem to be living up to the 'hype'
The strimmer itself is a fantastic piece of kit, but over £400s worth of battery's gets me just over an hours run time!
Photo of Blue Angel

Blue Angel, Champion

  • 177,594 Points 100k badge 2x thumb
I believe that model has the same hardware as the 15" trimmer we have here. For normal maintenance style trimming around the yard, most people will get over a half hour of use on a 2.5Ah battery.

If you're really pushing it hard it can suck batteries dry much faster. It all depends on the load you put on the tool and whether you're taking advantage of the variable speed function or just holding it wide open the whole time.
Photo of John Cole

John Cole

  • 496 Points 250 badge 2x thumb
Long grass and weeds, pushing it fairly hard but just over an hour for the three batteries in question?
Disappointed to say the least!
Photo of Blue Angel

Blue Angel, Champion

  • 177,594 Points 100k badge 2x thumb
Is it this model you have, the BC1500E-F?

https://egopowerplus.co.uk/products/line-trimmers-brush-cutters/bc1500e-f-38cm-bike-handle-line-trim...


If so, it appears to be based on the same 15" string trimmer we get here in North America.  If that's the case, yes, it certainly seems you're not getting much run time out of the tool.  I would think even with heavy use the tool should last an hour or more with just the 7.5Ah battery, let alone a 5Ah and 4Ah as well.

I'd get in touch with Ego Europe, express your concerns to them and see what they say.
Photo of Amber F.

Amber F., Official EGO Rep

  • 67,576 Points 50k badge 2x thumb
Please email EU support here: eu.support@egopowerplus.eu. I'm 100% positive they'd be happy to help figure this out.