# lithium ion battery pack advise



## dougingraham (Jul 26, 2011)

Is it 16 cells or are there more layers than what can be seen in the photo? If just 16 cells then it is arranged as an 8S2P. The S means series and the P means parallel. 8S is correct for a 30 volt as each cell as each cell of that type has a nominal voltage of 3.7 making 8*3.7=29.6 volts. If it is a 200wh pack then 200/29.6=6.76 amp hours for the paralleled element. If just 2P that means each cell is 3.38 AH which seems a little high but not impossible. If it is actually 32 cells making this an 8S4P and each cell would have 1.69 AH which is on the low end for that kind of cell but would be the least expensive version available.

What you want to do is increase the range and if you add 8 more cells to that pack you will increase the range by approximately 50% if it is an 8S2P. You would want to add each additional cell in parallel with the existing pairs. This will allow any existing charge balance or safety features of the BMS to continue to work. If it was me I would buy 8 more 18650 cells and solder them in place. However I cannot recommend that other people do this as these cells can be damaged by soldering to them and without proper technique and equipment you can have an event which will ruin your whole pack. This will not fit in the original pack location and will add 50% more weight to the battery.

Count the cells and check the voltage. I don't see how they could be 36 volts with only 16 cells.

Good luck!


----------



## sunworksco (Sep 8, 2008)

I know everyone is going to jump of the fire truck ladder on my comment but I would seriously consider ThunderPower lithium polymer batteries.
These are the best polymer batteries made and I have used them for years without mishaps. Just make sure you use a good polymer balancing charger and a low battery voltage cutout device.
This will save lots of weight, gives fast charging and will outlast current battery technologies.
Consider using a Hyperion dual battery charger with dual battery packs.


----------



## lucian75 (Feb 28, 2010)

Hi,thanks for your answers...but you don't see both pictures?its on battery pack splited in 2 
8x 2 and 4x2 so 24 cells.

And for the last question..its possible to recharge again or have no chance?


----------



## sunworksco (Sep 8, 2008)

They are rechargeable


----------



## dougingraham (Jul 26, 2011)

lucian75 said:


> Hi,thanks for your answers...but you don't see both pictures?its on battery pack splited in 2
> 8x 2 and 4x2 so 24 cells.
> 
> And for the last question..its possible to recharge again or have no chance?


Ok so 24 cells means 12*3.7= 44.4 volts nominal and 50.4 peak. 200 wh / 44.4 volts = 4.5 AH or 2.25 ah per cell which is an expected value.

You are not going to be able to reasonably replace the 24 cell pack with one that has more capacity in the original space. The 18650 cells have quite a bit higher energy density than the mentioned Thundersky cells. About the best you can do is replace the whole thing with the highest energy density cells in that size. You can get 3.4AH cells (instead of the 2.25 ah) for about $10 each. So for $240 you could probably increase your range from 15km to a little over 22 km in the same space.

If you look for 18650 cells on EBay you will find off brands that claim 4 or even 5 AH. They don't even have as much usable capacity as what you have now. Do a search for Panasonic 18650 battery. If they are real Panasonic cells they will have the claimed capacity. The 3.4 AH are the ones to look at.

And yes they are rechargable using the same charger as you currently are using.


----------



## dougingraham (Jul 26, 2011)

lucian75 said:


> PS i want also to help someone who have a problem...he don't use for a while he's wheel and forget to recharge it after some time..and now he can't recharge at all...he say he measure and have only 12.5 V i think...and her package is 60 V
> ...its any way that he can recharge it again?


It depends on what kind of batteries they are. The fact that you only see 12.5 volts on a 60 volt setup probably means some of the cells have shorted and those probably will not be recoverable. If you had a device that could charge the individual cells you might be able to partly recover the pack but it will probably never be completely right again. The charger that they are trying to use is probably seeing the voltage is outside of its range and refusing to even try to charge.


----------



## lucian75 (Feb 28, 2010)

Hi,first of all i don't know to much about these things...that's i ask your help 
But i'm thinking about something..and you can tell me if can work...
So the pack are 44.4 V..thats why on my charger is 50. 40 V i suppose.
Its possible to use another pack..maybe with a bit more V to recharge the inside one directly? I know that must be balanced...so between those 2 packs can be something similar with charger who keep balance?

Also one question..li ion pack can be charged in the time when is used? Can be dangerous?

About problem to charge the pack with problem..i think he have LiFePo4 pack
LIFePo4 52 V 
122 Wh
He don't recharege it for a few months...and now the charger won't charge it anymore..
12.5 V he measure with an voltmeter i think..


----------



## sunworksco (Sep 8, 2008)

dougingraham said:


> Ok so 24 cells means 12*3.7= 44.4 volts nominal and 50.4 peak. 200 wh / 44.4 volts = 4.5 AH or 2.25 ah per cell which is an expected value.
> 
> You are not going to be able to reasonably replace the 24 cell pack with one that has more capacity in the original space. The 18650 cells have quite a bit higher energy density than the mentioned Thundersky cells. About the best you can do is replace the whole thing with the highest energy density cells in that size. You can get 3.4AH cells (instead of the 2.25 ah) for about $10 each. So for $240 you could probably increase your range from 15km to a little over 22 km in the same space.
> 
> ...


Thunder Power not Thunder Sky.
Different as the moon and the sun.

http://www.thunderpowerrc.com


----------



## dougingraham (Jul 26, 2011)

lucian75 said:


> Hi,first of all i don't know to much about these things...that's i ask your help
> But i'm thinking about something..and you can tell me if can work...
> So the pack are 44.4 V..thats why on my charger is 50. 40 V i suppose.
> Its possible to use another pack..maybe with a bit more V to recharge the inside one directly? I know that must be balanced...so between those 2 packs can be something similar with charger who keep balance?


The charger says 50.4 volts! Excellent. That is the full charge voltage for a 12 cell pack of that type so my guess was correct. If you want to add in a buddy pack to extend the range that would work too. I would just make another pack exactly like the first one and connect the two in parallel when operating the device. Charge them separately. Don't complicate things by having a second pack that is higher voltage and then trying to charge the original pack from it. The greatest efficiency will be attained through simply paralleling the packs.



lucian75 said:


> Also one question..li ion pack can be charged in the time when is used? Can be dangerous?


Most types of lithium cells can be charged at a 2C rate without any issues. With the kind of cells you were showing I think you can safely do a 2C charge so you can get to about an 80% charge in a little over 20 minutes and then the charge rate tapers off so you end with a full charge in about 45 minutes.



lucian75 said:


> About problem to charge the pack with problem..i think he have LiFePo4 pack
> LIFePo4 52 V
> 122 Wh
> He don't recharege it for a few months...and now the charger won't charge it anymore..
> 12.5 V he measure with an voltmeter i think..


LiFe type cells do not like being stored discharged. I think that battery is ruined.


----------



## dougingraham (Jul 26, 2011)

sunworksco said:


> Thunder Power not Thunder Sky.
> Different as the moon and the sun.
> 
> http://www.thunderpowerrc.com


Sorry, I read what I was expecting to read. I've had a couple of Thunder Power packs over the years. I did not think they were anything special. Today I would get the Turnigy packs from Hobby King and save a bunch of money.

The 18650 cells have a higher wh/li and wh/kg rating than the RC LiPo cells.

The LiPo cells have about a 130 wh/kg and about a 260 wh/liter rating.
The 18650 cells in his pack have a 184 wh/kg and a 457 wh/liter rating.
The better 18650 cells have a 266 wh/kg and a 691 wh/liter rating.

The downside of these cells is that you can only drain them at about a 2C rate or they tend to overheat and catch fire while the LiPo cells have continuous C ratings of over 60 in some cases.


----------



## lucian75 (Feb 28, 2010)

Tank you dougingraham for your patience with a newbye like me 

Another thing..its possible to connect in paralel both packs with a jack like i have for charging like in this picture? I ask because if its possible..i can keep connected the second pack with a cable to that jack...but without that thing from charger that lock the cable with jack when is charging...so if something happen like fall down or something like that...the cable will be disconected from jack...

If it was possible i think i was liking more to have battery pack external..and conected with that jack...in that way i can use foe example 2 more spare pack battery...and easy to change it...if you knw what i want to say 

,,


----------



## dougingraham (Jul 26, 2011)

lucian75 said:


> Another thing..its possible to connect in paralel both packs with a jack like i have for charging like in this picture? I ask because if its possible..i can keep connected the second pack with a cable to that jack...but without that thing from charger that lock the cable with jack when is charging...so if something happen like fall down or something like that...the cable will be disconected from jack...
> 
> If it was possible i think i was liking more to have battery pack external..and conected with that jack...in that way i can use foe example 2 more spare pack battery...and easy to change it...if you knw what i want to say
> 
> ,,


It is possible to use a connection something like that one. Maybe even that one. Without actually tracing out the wires and looking at a schematic I can't tell you specifically what will and won't work. If you are going to parallel packs the wires need to be heavy enough to carry the expected current and I don't know what that current is.

Best Wishes!


----------

