# Battery Pack Voltage when Charging



## Randy Stone (Jan 2, 2008)

I have a 14.8 volt pack and a 18.5 volt pack.

When charging the 18.5 volt pack I seen voltage level go over 21 volts. The 14.8 volt pack is on charge now and the voltage level is at 15.63 volts and still climbing.

It's on fast charge and has been charging for 59 mins

My question is< what voltage level is typical for a 14.8 and a 18.5 volt pack when they are fully charged?

My Dash 9 was running fine with the sound on when I stopped it. When I went to start moving again, the Dash 9 shut down. no sound, no response from the Dash 9.

I replaced the 14.8 volt battery with my 18.5 volt battery and the Dash 9 came back to life.

When I plugged the 14.8 volt battery to my Tenergy Balance Charger and started charing, it showed 11.99 volts.


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## chuck n (Jan 2, 2008)

I'm nowhere near an expert on batteries and charging, but I think that to charge a battery the charging voltage must exceed the output voltage of the battery. The voltages you posted seem reasonable.  TOTALLY UNINFORMED COMMENT, I would think,that the closer the charging voltage is to the output voltage is, that would indicate a trickle charge. I think that is good. Chuck


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## Randy Stone (Jan 2, 2008)

with voltage at 15.94 volts, the charger shut off at 120 mins. 

I have to think it wasn't fully charges. Just timed out


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## chuck n (Jan 2, 2008)

Randy, is the 15.94v coming off the battery, or the charger? 



Chuck


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## Gary Armitstead (Jan 2, 2008)

Randy,

I've been using battery power since 2007, so I'm definitely NO expert. But this is what I have experienced with three locomotives. My Bachmann Connie has a 14.4v, 4200 mah NiMH battery and when I charge it, it goes up to about 18 to 18.3 volts, using a Tenergy charger. Usually after I run a couple of hours or more, the STARTING voltage with the charger shows about 15 volts. My Accucraft #346 with the SAME type and size battery finishes charging at about 16.5 volts-starts at around 14.5 volts after a two to three hour run. My Berlyn goose #6 has a Li-ion 1400mah, 14.8 volts. This charges up to 16-17 volts at the end of 120 minutes. Starts charging around 14 volts after a normal run. Your mileage may vary. But I'm seeing about the same numbers as you are getting. I was told not to fret about it by those here who know more about batteries than I do.










EDIT: Randy I just checked your post again and you mentioned that you were "fast charging". What do you have the "charge amps" set for? I found I get a better charge if I set the charging amps at about half of the ah capacity of the battery. Just my experience.


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## Randy Stone (Jan 2, 2008)

The 15.94 was what the charger showed when it kicked off. 

The charger was on fast charger. 2.0 amps


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## Michael Glavin (Jan 2, 2009)

Randy,

3.7v lithium cells charge to 4.2V, 4.2V x 4=16.8V termination voltage. Monitor the slow charge termination voltage and see what happens, maybe you'll get a full charge. Perhaps the Tenergy unit is operating with some modicum of decorum in the FAST charge mode! Or it’s kinda typical of inexpensive out sourced stuff with varying degrees of acceptable component tolerances…. 

120 minutes and or 2 hours under charge @ 2 AMPS, is out there unless you got a BIG battery!!!! An educated guess based on what little info you provide would lead me to suggest you got a bad cell in the heard. We need more info on the batteries, size and such

There’s no free lunch, fast charging these cells is acceptable practice but has its caveats, less than full charge and extended battery life are the price you pay to play. And you know we don’t ask much of this technology as our current draw numbers are negligible compared to some hobbies and or uses. 

Michael


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## Greg Elmassian (Jan 3, 2008)

uhh... wouldn't 2 hours at 2 amps be 4 amp hours... and the energy in is usually pretty close to the energy out... so I don't know why you wrote "BIG battery!!!!" 

Many people run 5600 mah batteries... this is 4000 mah... 

Not so big... Randy did not indicate pack size... 

Greg


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## Randy Stone (Jan 2, 2008)

Sorry, the 14.8 volt pack is 7800 MAH


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## Stan Cedarleaf (Jan 2, 2008)

Posted By rlvette on 30 May 2013 04:02 PM 
I have a 14.8 volt pack and a 18.5 volt pack.

When charging the 18.5 volt pack I seen voltage level go over 21 volts. The 14.8 volt pack is on charge now and the voltage level is at 15.63 volts and still climbing.

It's on fast charge and has been charging for 59 mins

My question is< what voltage level is typical for a 14.8 and a 18.5 volt pack when they are fully charged?

My Dash 9 was running fine with the sound on when I stopped it. When I went to start moving again, the Dash 9 shut down. no sound, no response from the Dash 9.

I replaced the 14.8 volt battery with my 18.5 volt battery and the Dash 9 came back to life.

When I plugged the 14.8 volt battery to my Tenergy Balance Charger and started charing, it showed 11.99 volts.

Randy, as Gary shared.... Just my experience with Li-ion batteries.....









The 14.8 batteries have the safety pcb built in so the battery will shut down at the 11.99 or 12 volts... That's the way it's designed. When charging, it should shut off at about 15.8 or close to 16 volts. That's the way it's designed. 


Same with the 18.5's... They'll shut off about +/- 15.8 volts on the discharge side and will charge up to just over 21 volts on the top side. The built in pcb shuts them off on both the discharge and the charge ends..... That's the way they're designed...









It's a safety factor on each so the batteries won't be damaged... In the case of the Dash 9 shuttiing down, the battery had discharged to the shutoff point and will not run until recharged or battery changed with a fresh one charged to it's working range..... 

It ain't a tek-in-all explanation 'cause I ain't tek-nick-al..... Just been using them practically for 5 years or so and they just work that way... 

Hope this helps...


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## Michael Glavin (Jan 2, 2009)

Greg,
As was suggested depends on battery size…….. And unless the battery was completely exhausted two hours is a notable[/i] time frame IMO… It was suggested the battery measured 11.99V when put to charge; 11.99V/3.0V per cell maybe the cut-out voltage of the onboard doohickey (more likely the recovered voltage value after a brown-out). 
Maybe a simple case of undercharge, when I first read Randy’s post I thought he suggested the engine shut down prematurely, I re-read his post and see I was mistaken in my thinning.
Anyhow, I’d load test the battery, it’s the only way I know to discover a bad apple up without removing the wrapper on these set-ups… Another reason why I am an advocate for balance charging…
Michael


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## Michael Glavin (Jan 2, 2009)

Stan,
FWIW: I can’t recall ever seeing any specifications where PCB’s were rated to detect/cut-out at 3.0V/16.0V respectively. That said I have not looked at any of those gadgets of late… It’s possible the chargers in play are limiting the charge adsorbed, verses the PCB unloading. 3.0V is a common number for a PCB to close its safety circuit after a brown-out.
Generic industry specification for a PCB/PCM single 3.7V Lithium-Ion cell is generally:
Over charge detection voltage > 4.2V per cell
Over discharge detection voltage >2.4V per cell
Michael


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## Stan Cedarleaf (Jan 2, 2008)

Michael... Thanks so much for the figures... 

As I shared, I'm not a techie when it comes to the "exact" parameters. But I'm sure glad the suppliers have added the PCB's to the Li-ions to protect them from over charge and excess discharge. When I first started "experimenting with Li-ions many years ago, there was no PCB's on the cells themselves. All protection was build into the device and chargers the cells were used with. 

I learned the hard way to "destroy" a number of cells...
















Again, thanks for the input..


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## Greg Elmassian (Jan 3, 2008)

Michael.... if I calculate right (see previous assumption that charge in time is about equal to charge out time), then for Randy's pack, 4 amp hours is about half depleted. I don't see that as a problem, or unusual. Greg Posted By rlvette on 30 May 2013 09:12 PM 
Sorry, the 14.8 volt pack is 7800 MAH


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## TonyWalsham (Jan 2, 2008)

Not to hi-jack the thread but I have a question that is sort of relevant. 
I was wondering if someone could explain to me what the term "final voltage" means on a Turnigy Accucell 8150 charger when discharging, or cycling, a NiCd pack. Turnigy are not very helpful as there is no explanation in the instructions. 

Is it to be the minimum voltage of one typical cell of the pack, or the total of the cells the lowest voltage a cell should go to? That is either 1.1 volt or 6.6 volts for a 6 x cell pack?


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## izzy0855 (Sep 30, 2008)

Michael, 
Stan is correct, most companies that manufacture PCB's for Lithium-ion battery-packs like mine shut-down at a precise voltage. (ie: 14.8V @ 16.8V charged, over release discharged voltage is 3V +/- .01V x 4 cells = 12V). 

Randy, 
To answer your questions about what voltage does a 4S/5S Lithium battery-pack shut-down at? Randy, that depends on the PCB and the quality of the cells manufactured in the pack. Each PCB manufacturer (like CR) can set the peak voltage, you'll see some at 21V, 21.5V like Aristo's but more importantly that depends on the number of cells manufactured in the pack and the quality of those cells. Usually, a 4S lithium PCB is set at 14.8V nominal, 16.8V peak (full charge) and 12V low voltage discharge. A 5S lithium pack is usually set at 18.5V nominal, 21V peak (full charge) and 15V low voltage discharge. The higher the peak voltage that is set on the PCB, the greater risk you run of the cells going out of balance faster. 

In regards to your Dash 9 battery, you can; but a 14.8V lithium battery will not operate a Dash 9 at it's full potential, there's not enough current in the pack. If you pull more amps then what a lithium battery PCB's can handle, then your cells will go out of balance and you will not be able to full re-charge your battery at peak voltage. Most 4S lithium are set between 3 - 5 amps draw with a :45 sec burst at 6amps. "In my opinion," that's not enough current to operate a Dash 9 at low speeds pulling 15 cars or more. You pull more amps starting and stopping your loco than at full speed. I would suggest either upgrading the battery to 18.5V or replacing the PCB on your 4S lithium to a 7amp current draw. 

In regards to fast chargers. All lithium battery-packs cannot with stand a fast charging cycle. If your charging a lithium battery at more than 1.5amps per hour, then you run the risk of catching your battery on fire. All lithium battery-packs charge cold, if for any reason your battery is getting warm to the touch during the charging cycle. Remove the battery from your charger, take it outside and place it on concrete. Wait 30 minutes, touch the battery to see if it is hot, if not; lower your amp hour rate to 1amp and continue the charge cycle. 

I think one question that hasn't been asked is, Randy; how many cycles has your lithium battery gone through? It usually take between 3 - 5 cycles before a lithium battery is at it's full capacity. 

I hope this helps, 
Rick Isard 
Cordless Renovations, LLC 
RCS America


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## Greg Elmassian (Jan 3, 2008)

Umm.... " If your charging a lithium battery at more than 1.5amps per hour, then you run the risk of catching your battery on fire" 

That blanket statement is incorrect. 

The charging current depends on the amp hour capacity of the cell, the design of the cell, and the charging "curves". 

The only reason I bring this up is so someone does not take a small li-ion battery and charge it at 1.5 amps. 

Maybe you only use the same amp hour battery in all your packs, but I think it's very important to qualify the information a bit more. 

Greg 

p.s. Many laptop batteries will charge warm so that "rule" is not really true either, but personally I agree to a very minimal temperature rise when charging... for extra safety...


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## Randy Stone (Jan 2, 2008)

I originally bought the 14.8 volt pack for the Dash 9 and at Marty's the loco couldn't pull a string og grain hoppers up the highline grade which is pretty steep. It would trip the overload in either the battery pack or electronics. After a few seconds it would reset and go again with help from a push by hand. It then kicked out and would need to wait a few seconds to start again. The loco which does not have but one small weight as supplied by Aristo Craft, never tried to spin the wheels. It just bogged down and shut off. This happened at least 3 times before getting up over the hump. So last year I bought a 18.5 volt pack. I didn't get around to pulling the grain hoppers, but pulled my 4 USAT streamline passenger cars up the highline grade several times without and issues. The loco still didn't have the speed I think it should have as others running Geeps were running a lot faster. In hind sight, I think I should have bought the 22 volt pack. Yesterday, I was pulling 26 coal hoppers and a caboose with the 14.8 volt pack. My layout is basically flat and I wasn't drying to go very fast so the 14.8 volt pack was doing the job. 

By the way, while charging the 14.8 volt 7800mah battery pack yesterday at 2.0 amps (Fast Charge) for 120 minutes, I constantly was checking the battery to see it is was getting warm and it never did.


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## Randy Stone (Jan 2, 2008)

One thing regarding batteries that has been on my mind is voltage requirements. 

I hear all the time on this forum that the only difference between running a 14.8 volt battery pack and a 18.5 volt battery pack in a specific loco is maximum speed. 

I am no battery expert, but I believe there is more difference than just speed. 

There has got to be more torque available when powering a loco with a 18.5 volt battery than when using a 14.8 volt battery. 

By that I mean, a Dash 9 should be able to pull more cars using an 18.5 volt battery than one using a 14.8 volt battery. 

I really believe that if I had been using an 18.5 or 22 volt battery pack at Marty's when I was trying to climb the highline grade, the Dash 9 would either have been able to pull the load up over the hill or would have broke traction and spun the drive wheels.


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## chuck n (Jan 2, 2008)

Randy, as usual your question probably exceeds my ability to give a completely correct answer. I think that if your engine is not receiving enough power voltage and amps from the battery to overcome the drag of the train and the weight of the engine it will bog down and stop. From my experience the wheels will spin when there is ample power but the drag of the train exceeds the tractive effort of the engine. If the engine stops not enough power, if the wheels spin, too many cars.

Chuck 

I have measured the tractive effort of a number of my engines. It averages about 1/3 the weight of the engine. I increase the power, on the track, until the wheels on the engine start to slip. I have a fishing scale with a loop that I can hook on the coupler of an engine, or a string of cars to determine the pulling power, or drag. It is easy to do. Just get a fishing scale and loop of string. Hook one end to the scale and the other to the engine or train and pull. Even a slight grade increases the drag. The poorest pullers I have are the LGB Moguls. They rate out at about 25% of the engine weight. Other engines max out near 40%. Traction tires add only a couple of percent tractive effort.

PPS Someday I'm going to measure the tractive effort of my USAt GG1, but it is too damned heavy to carry upstairs to weigh, and the bathroom scales are too damned bulky to take down. OK, I'm lazy!


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## izzy0855 (Sep 30, 2008)

Randy, 

That's good to hear, just keep checking it. We have done numerous tests over the years with PCB amp ratings and a string load of different manufacturers lithium cells. More than 50% of those cells that were charged over 2amps, would get hot and start to balloon or expand (because of their construction) thus causing the PCB to short circuit melting the shrink wrap and catching on fire. Just be careful. 

In regards to the difference in packs, there are three exceptions. Voltage, cell manufactured charge/discharged capacity and PCB amp rating. The more voltage you have the faster your loco will operate (under the same operating conditions). So, if I have one CR-1605 - 14.8V @ 5600mah and one CR-1705 - 18.5V @ 5600mah both manufactured identical, fully charged to the same capacity and installed into the same style of loco's sitting side by side on the same layout, (like drag a race) both using the same operating device and under the same conditions. The CR-1705 will increase in speed faster than the CR1605. 

Then you have to look at the individual cells and how their manufactured. There are several different types of cells for multiple applications all from the same company. There are standard cells for flash lights, there are cells for HRD (High Rate Discharge) that are used in cordless drills, there are cells for high capacity (3400mah) and will run like a diesel truck. It all depends on what your using it for. Then there's the PCB. Generally, most PCB's do one thing, "protect from over-charging or over-discharging" your battery-pack, and that's a good thing. Other's, like the ones we manufacture take it a step further. Amp hour rating with a short burst. What this means is if your pack is rated at 2.8amps then you can draw up 2750mah (or what the cells discharge rate is) of current to operate your train without the PCB resetting itself or cutting off. We over estimate the amp draw, so if your purchasing our 2800mah pack from CR our PCB's for that pack are rated between 4 - 7amps depending on the cells design. Those PCB's can with-stand a short burst of current higher than what there rated at, before the PCB will reset and shuts down. 

In most cases we're just looking for runtime with a high amp draw. When ever you purchase a lithium battery-pack look at the "over-discharge current rating of the PCB." That number or amp draw should usually be 2 - 3 amp higher than the total capacity of the pack. 

I hope this helps, 
Rick Isard 
Cordless Renovations, LLC 
RCS America


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## Randy Stone (Jan 2, 2008)

Rick 

I understand the higher voltage pack will give higher speed, but will it not give more pulling power?


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## izzy0855 (Sep 30, 2008)

Randy, 

No, same pulling power in both packs. We could upgrade you to HRD cells but the milliamp capacity is much less. I think the highest you can get is 2000mah, x 2 is 4000mah or x3 is 6000mah with a higher price tag as well. I'll check.

Rick Isard 
Cordless Renovations, LLC 
RCS America


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## izzy0855 (Sep 30, 2008)

Just checked, 

I can get a 1300mah @ 15C or 1000mah @ 30C. 

Rick Isard 
Cordless Renovations, LLC 
RCS America


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## Michael Glavin (Jan 2, 2009)

Randy,
Your question about torque and voltage is not easy to answer, there many variables at work. Kt (torque per ampere) is inversely proportional to Kv (rpm per volt). So lower Kv gives you a higher Kt and therefore more torque...but only per ampere. So if you wanted more torque a lower Kv motor is the answer. 
The speed at which the motor rotates is related to the voltage used. However voltage is only potential energy and the actual rpm a voltage will create is determined by how many turns of wire there are in each coil and magnet strength. More turns and stronger magnets mean fewer rpm’s per volt. Weaker fields mean more rpm’s per volt. This characteristic is the voltage constant or Kv (expressed as the rpm/v of the motor). 
In your case, a 7800mAh battery is the governing factor of Torque realized. Matters not what the combined cells count or series voltage is, the battery is only able to provide 8 Amps at rated voltage for twenty minutes or so… that said NO consideration is in play for the PCB/PCM, if your battery is limited to seven amps discharge current by the PCB that’s all you’re going to get!!! 
Torque generated by the motor is proportional to the amount of current flowing through the motor… In electrical terms, power is the product of voltage and current (watts). Torque is developed by the interaction of the rotors magnetic field together with its moving conductors, and is proportional to current consumed. So power OUT is proportional to (speed x current) and the mechanical TORQUE is proportional to the current being drawn from the battery. 
Power and or Potential (Watts) derived from the batteries:
14.8V x 8.0A = 118 Watts
18.5V x 8.0A = 148 Watts
As a rule the higher voltage batteries will provide less amperage with a like load at equal torque/power values.
Let’s say a motor is rated @ 100 watts output; 100/18.5V=5.4A while 100/14.5V=6.9A. An18.5V is working well below the aforementioned 7Amp PCB discharge limit.
Michael


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## Michael Glavin (Jan 2, 2009)

Rick,
I just looked high and low at specifications for OEM/aftermarket PCB/PCM’s. None were listed as having a charge detection voltage limit of less than 4.2V per cell (that said numbers could be whatever is desired or specified)…. Lowest discharge detection voltage limit I could garner was 2.8V per cell. The 16.0V termination value as noted by Stan is .8 volt lower than OEM battery recommendations. That .8V represents roughly 10-15% of the batteries full charge if memory serves me, so the battery is NOT ever fully charged. If in fact the discharge cut-off voltage is 3.0V per cell the only loss is realizing rated capacity.
The reason FAST charging is less than desirable is the simple fact that not all battery chemical matrixes are equal, some adsorb charge better than others due the rate of chemical reaction, and a byproduct is often heat and premature cell break down.
FWIW: I generally charge Li-Ion’s at 1C, OEM’s like 0.8C or less for the 18650’s. Randy’s 7800 mAh battery @ 2A is charging at a rate of 0.25C, hardly a fast charge! Two hours won’t get it done for that big battery, more like three hours me thinks.
Seems like what is needed is PCB/PCM's with a higher current discharge cut-off parameters for engines that have high power requirement's under load and or stall conditions...
Michael


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## Randy Stone (Jan 2, 2008)

Randy, as usual your question probably exceeds my ability to give a completely correct answer. I think that if your engine is not receiving enough power voltage and amps from the battery to overcome the drag of the train and the weight of the engine it will bog down and stop. From my experience the wheels will spin when there is ample power but the drag of the train exceeds the tractive effort of the engine. If the engine stops not enough power, if the wheels spin, too many cars. 

Chuck 

My exact thoughts Chuck.


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