Voltage reading
03-27-2015 | 10:51 AM
#1
Thread Starter
My Feedback: (6)
Joined: Oct 2002
Posts: 2,684
Likes: 0
Received 0 Likes
on
0 Posts
From: Mountain Home,
AR
Voltage reading
What is the normal voltage of a 3S LiPo after coming off a charger? I mean after taking it off the charger and letting it sit for a few minutes, and then checking it with a multimeter.
03-28-2015 | 10:34 AM
#3
Thread Starter
My Feedback: (6)
Joined: Oct 2002
Posts: 2,684
Likes: 0
Received 0 Likes
on
0 Posts
From: Mountain Home,
AR
Mine are actually reading 12.45 to 12.55 total. I was just wondering if anyone actually gets to 12.60 actual after charging and letting the batteries sit for awhile before checking.
03-28-2015 | 04:27 PM
#6
Senior Member
Most of my lipos behave in a similar manner.
The maximum charging voltage is between 4.20 and 4.23-4.24 as shown on the charger's display.
After setting a few minutes, the voltage typically drops to between 4.18-4.19.
The charger's adjustments and settings for "dead band" and "offset", as well as C/10, C/20, and accurate, quick, high current, etc. also impact the
difference.
If I were to set the charge rate to a lower than normal value, say 10% of normal, and also select accurate,
The voltage difference between the charging voltage and the at rest voltage will be less. The C/20 setting can also reduce the difference.
Why? It seems that the lower charge current setting also lowers the minimum current for final charge and balance. The C/20 setting
also lowers the minimum current.
Many chargers can measure the voltage difference between the voltage when charge current is applied, and when it is not, then using the difference to
alter or terminate the charge.
The maximum charging voltage is between 4.20 and 4.23-4.24 as shown on the charger's display.
After setting a few minutes, the voltage typically drops to between 4.18-4.19.
The charger's adjustments and settings for "dead band" and "offset", as well as C/10, C/20, and accurate, quick, high current, etc. also impact the
difference.
If I were to set the charge rate to a lower than normal value, say 10% of normal, and also select accurate,
The voltage difference between the charging voltage and the at rest voltage will be less. The C/20 setting can also reduce the difference.
Why? It seems that the lower charge current setting also lowers the minimum current for final charge and balance. The C/20 setting
also lowers the minimum current.
Many chargers can measure the voltage difference between the voltage when charge current is applied, and when it is not, then using the difference to
alter or terminate the charge.
03-30-2015 | 03:15 AM
#8
Senior Member
If you are not reading 4.2 plus or minus .01 volts after a full charge, I'd suspect that your volt meter need calibration. The 4.2 volts is a chemical fact, not an adjustable or varying value that can only vary with temerature and then by a very small margin.
03-30-2015 | 11:20 AM
#10
03-30-2015 | 12:31 PM
#11
With a little help from Yahoo! and Robert C...
The nominal voltage of a LiPo is 3.7 volts per cell. But, since we want all the performance we can get out of our batteries, we charge them to their maximum safe capacity. Most manufacturers claim this is 4.23 volts per cell. Almost every LiPo charger out there that utilizes CC/CV type charging will end the charge at around 4.21v.
By way of comparison, NiMh batteries typically will charge to around 1.4v per cell, even though they are rated at 1.2v. The battery in your full size car (12 volts) usually will be around 13.5 volts if it is fully charged.
As to why cells are listed at their nominal charge and not their full voltage capacity... I think it may just be because that is the way it's always been done.
The nominal voltage of a LiPo is 3.7 volts per cell. But, since we want all the performance we can get out of our batteries, we charge them to their maximum safe capacity. Most manufacturers claim this is 4.23 volts per cell. Almost every LiPo charger out there that utilizes CC/CV type charging will end the charge at around 4.21v.
By way of comparison, NiMh batteries typically will charge to around 1.4v per cell, even though they are rated at 1.2v. The battery in your full size car (12 volts) usually will be around 13.5 volts if it is fully charged.
As to why cells are listed at their nominal charge and not their full voltage capacity... I think it may just be because that is the way it's always been done.
03-31-2015 | 10:50 AM
#12
When the battery has discharged 50% of it's energy the cell/battery is at mid point voltage which is the nominal voltage.
It's also used as a description of what the battery is.
It's also used as a description of what the battery is.
04-02-2015 | 06:32 PM
#13
Senior Member
Actual - - - +/- measurement accuracy, charger, etc. Usually between 4.18 and 4.19 per cell or so after the battery has been at rest for several minutes after the charge.
Remember that a charger must deliver energy to the battery, and this means that to charge to 4.20, the charger must have a charge voltage slightly greater than 4.2.
Some chargers, such as the FMA PL & DPL series, allow the user to custom set parameters to match specific lipos. When done properly, this can narrow the differences between ideal and
typical.
04-02-2015 | 06:44 PM
#14
Senior Member
To add to the confusion, most everyday use DVMs read 4.2v to two decimal digits, and add +/-1 LSD +/-/ the full scale accuracy spec.
In other words a DVM reading of exactly 4.20v might mean that the actual voltage is higher or lower.
To combat this, I bought an inexpensive "standard" that puts out a reference voltage of 4.2000 v This allows me to determine the actual
reading of a dvm with 4.2000 v input. That DVM can them be used to compare a chargers voltage reading against the DVM's reading.
