LI-ION 18v Battery Pack

[fenner]

I have an 18v battery pack of 18650 which one of them failed so I want to add another I selected the same type battery the 4 original batteries measure around 4.2v the one I bought is 3.37v can I add this or do I have to charge it to 4.2 before attaching it to the others.

 

[Harald Kapp]

A well designed battery pack/charger combination will balance the different charge states.
In any case it will not hurt to bring the new cell up to a charge state near that of the old ones.

I consider it good practice in such a case to replace all batteries at once. Otherwise you risk the remaining old batteries failing one after another and you'll be busy replacing them.

 

[fenner]

A well designed battery pack/charger combination will balance the different charge states.
In any case it will not hurt to bring the new cell up to a charge state near that of the old ones.

I consider it good practice in such a case to replace all batteries at once. Otherwise you risk the remaining old batteries failing one after another and you'll be busy replacing them.

Thanks Harold the batteries are only months old since I installed them I do not know why one suddenly pack in.

 

[Bluejets]

Thanks Harold the batteries are only months old since I installed them I do not know why one suddenly pack in.

Show a link to the cells you bought and it might give an indication of what to avoid in future.

 

[fenner]

http://www.ebaystores.co.uk/lithium-energyy/About-Us.html

 

[Bluejets]

There are 175 different 18650 products in that link.
Which one did you get....?

 

[fenner]

Genuine SAMSUNG 30Q 18650 3000mAh 15A INR IMR Rechargeable Cells Battery
I added the battery but when i tried to charge it the imax charge came up with " Connection Break" so I decided to change the BMS board thinking it may be that I had bought a new BMS but cannot figure out where the wires go looking at the picture there is no wiring diagram big enough for my eyesight. there are B+ B- P+P- I would think the B is battery what is P I have abandoned it for the time being until I can sort it out. Any help would be appreciated can I do away with the BMS board.

 

[Audioguru]

Thanks Harold the batteries are only months old since I installed them I do not know why one suddenly pack in.

Because they are cheap and came from "you know where".

 

[fenner]

Very interesting ! so where do I buy them ? surely all ebay sellers are not selling fake batteries and you can't just buy the dearest thinking (you get what you pay for) .

 

[Bluejets]

RS Components in the UK would be one .
There you can check the cell specs at least.
I have used Hobby King at times and they seem ok but times do change.

 

[fenner]

Thanks to all I will bear that in mind I do not use them to build packs usually but I wanted to convert my battery circular saw

 

[Bluejets]

but I wanted to convert my battery circular saw

Note to watch the discharge ratings when you buy the cells in that application.

 

[WHONOES]

Thanks Harold the batteries are only months old since I installed them I do not know why one suddenly pack in.

Probably Chinese junk!

 

[fenner]

Note to watch the discharge ratings when you buy the cells in that application.

I am not sure what you mean can you elaborate

 

[Bluejets]

I am not sure what you mean can you elaborate

Your use is in a battery circular saw so check what current the saw draws under load.
It should have it on the label or a spec sheet if it is a reputable brand.

Reason being, the cells have a maximum discharge rate.
This can be a certain amount over say a few minutes or just burst of a few seconds.
Overdo it and the cell will overheat and more than likely at least be damaged, at worst, break into flames.

 

[fenner]

Thank you Bluejets There is nothing on the saw regarding power output the only thing I can see on the original battery case is for the saw is 18v with 15 NiCD cells 1.3Ah could I calculate anything from this.

 

[Bluejets]

If these are nicads, where did the 18650 query come in...??

Either way, at 1.3Ah it is not a large capacity by any means so one might deduce the current is not all that much.

To answer you question though, calculating the motor current from the Ah capacity is not possible.

 

[fenner]

If these are nicads, where did the 18650 query come in...??

Either way, at 1.3Ah it is not a large capacity by any means so one might deduce the current is not all that much.

To answer you question though, calculating the motor current from the Ah capacity is not possible.

Thank you Bluejets.

 

[Martaine2005]

A cordless 18v tool, especially saws, wont run for 10 minutes on 1.5Ah batteries. What ever battery you build, get as much Ah as you can.
18v tools are also quite comfortable on 20v. So you really can play around and get as much power and hours of run time as you like. All my 18v tools are now running 20v lithium cells.
Kind of defeats the object but you can also use large batteries via diy umbilical cord.


Martin

 

[fenner]

A cordless 18v tool, especially saws, wont run for 10 minutes on 1.5Ah batteries. What ever battery you build, get as much Ah as you can.
18v tools are also quite comfortable on 20v. So you really can play around and get as much power and hours of run time as you like. All my 18v tools are now running 20v lithium cells.
Kind of defeats the object but you can also use large batteries via diy umbilical cord.

Thank you Martin, what do you mean by your last statement.
Martin