Author Topic: S5 lipo battery management circuit for18v impact wrench  (Read 1976 times)

0 Members and 1 Guest are viewing this topic.

Offline cd_willTopic starter

  • Newbie
  • Posts: 7
  • Country: gb
  • M6LRB
S5 lipo battery management circuit for18v impact wrench
« on: December 10, 2017, 10:59:56 pm »
hi all
i am trying to design a 5cell lipo batttery pack for a 18v impact wrench  to replace the nicad pack
i want to make if stand-alone to charge from a 24v source or from the original charger that can supply around  22v
i have seen some TI chips that say thay can do it but i cant figure out how they do the balancing

i hope some one can help
thanks all
M6LRB 77
 

Offline ovnr

  • Frequent Contributor
  • **
  • Posts: 658
  • Country: no
  • Lurker
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #1 on: December 10, 2017, 11:07:18 pm »
The TI chargers do not balance your pack. You will need to bring your own balancing circuit.

If you didn't plan to stick it in a power tool, I'd suggest something like this BMS module, but the 15A limit will not work for you. Try searching for 5S BMSes. Alternatively, you could just remove the protection components from the one I linked and keep the rest, but I'd really suggest a proper BMS anyway.
 

Offline Freelander

  • Regular Contributor
  • *
  • Posts: 146
  • Country: 00
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #2 on: December 10, 2017, 11:20:53 pm »
hi all
i am trying to design a 5cell lipo batttery pack for a 18v impact wrench  to replace the nicad pack
i want to make if stand-alone to charge from a 24v source or from the original charger that can supply around  22v
i have seen some TI chips that say thay can do it but i cant figure out how they do the balancing

i hope some one can help
thanks all
Hi, are you definitely planning on using LiPo ? or do you mean Li-ion - most normally use 18650 packs.
If you are using 18650's (or indeed the lipo - then you can use an imax external charger / balancer B6AC - or a clone of. You can pick one up for about 15 UK Sheckles. The 18650's need to be the high C versions - and of a known source and make - NOT ebay (although the charger will be fine from ebay)
Even for a lipo the imax b6ac is perfect.
The only difference for the charging is that you will need the main charging lead and the balance lead.

The B6AC is limited to about 5A or about 70 - 100w (iirc) ... ?? - great balance charger . No worries at all.
 

Offline Freelander

  • Regular Contributor
  • *
  • Posts: 146
  • Country: 00
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #3 on: December 11, 2017, 12:02:04 am »
Just to add - a point worth seriously considering if going the LiPo route is that you must charge it and use it - never leave it 'charged' fully as this can permanently damage the LiPo. LiPo cells are designed to be charged then discharged within a fairly short time period.
My cordless devices have multiple spare battery packs. If I went LiPo I could not safely have charged packs stored for use. The cells will usually puff out and fail (or one or more of the cells will)
You ideally would need to discharge to a 'storage' level. Li-Ion are far far far better here. Yes, keeping them fully charged (at around 4.2V, may shorten their life --  eventually -- , but you will not damage them.
I have had my Bosch Pro units on Li-ion for more than 5 years - still on same packs and they seem as new. If they have lost any capacity it is not noticeable.
Lipo are really not a good choice for anything that may be charged and then stored. They are really a charge and then hammer the discharge type of cell.
There are also many many Li-Ion units around (laptop batteries etc) - they virtually ALL use 18650 cells (as do all the power tools - that I know of) In most of the laptop batteries there is often no balance charging at all. In fact, I have never seen a laptop battery with true balance charging. Just 18650s in series or series / parallel with temp sensors on 1 of every 3 cells in series. There is some logic on the input but this is really to enable or disable the output and monitor levels. That can all be done via an external charger. In other words, balance charging is the natural choice however most series connected batteries simply don't bother.
« Last Edit: December 11, 2017, 12:10:15 am by Freelander »
 

Offline cd_willTopic starter

  • Newbie
  • Posts: 7
  • Country: gb
  • M6LRB
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #4 on: December 11, 2017, 12:18:29 am »
that is a very good point i hadn't considered the current pack hples 15 SC cells so i dont think 18650 will fit very well

and yes i want to keep it fully contained in the pack
 
M6LRB 77
 

Offline Freelander

  • Regular Contributor
  • *
  • Posts: 146
  • Country: 00
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #5 on: December 11, 2017, 12:30:49 am »
that is a very good point i hadn't considered the current pack hples 15 SC cells so i dont think 18650 will fit very well

and yes i want to keep it fully contained in the pack
 
Have a look at what space you have inside the pack - you might get away with it. have you got 3 x 3 SC cells together ?
If your SC are 43 / 23 mmm (I have seen slightly shorter ones) then the ;length; of the 3 stack is the same as 2 18650s (18mm x 65mm)
So you could get 6 18650s in - IF the pack is stacked that way.... effectively a 6s - or, 5s with a spacer as the 6S might cause the drill to take off into the sunset  >:D
 



Offline Freelander

  • Regular Contributor
  • *
  • Posts: 146
  • Country: 00
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #8 on: December 11, 2017, 01:04:29 am »
eBay auction: #https://www.ebay.co.uk/itm/Battery-Rebuild-For-SNAP-ON-18-V-volt-CTA3850-CTB3185-CTB3187-3-0Ah-Rattle-Gun/182754818725?hash=item2a8d093aa5:g:A1UAAOxylpNTPkGb this is the alternative but its nimh
NiMh are - imho - about as much use as a one legged man in an arse kicking contest ::) :scared: ;). The self discharge is crazy. You can charge them up and find they have lost 35% in a month - even a few weeks. ! they can lose 15% in the first 48 hours.
NiCd can also suffer a similar fate but I always found NiMh far far worse.
Every time I think of NiMh I get an image of a bucket full of holes. :palm:
If you can get GOOD nicads I would be tempted to rebuild with those and have done with it. When we all used Nicads in RC stuff they were cheap as chips and damn good quality. Now it is the ying tong yip lottery.
Also, 18650 in High C guise aren't cheap. I can get damn good 2c units at 2400mAH from one place I know (dirt cheap too!) but 2 C wouldnt hack it for you in a electric version of a windy gun - (I hadn't heard the term 'rattle' gun before! :)). I still use a compressor and a small windy gun or the 'BFO' windy gun. Pipework is a bit of a pain but hey ho. Some damn good small 'rattle' guns about though. Just don't use an extension... ::) ...................  ;)
 

Offline Freelander

  • Regular Contributor
  • *
  • Posts: 146
  • Country: 00
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #9 on: December 11, 2017, 01:14:12 am »
Cant work out what that is meant for, quick read sort of says - for Lithium, then NOT FOR LITHIUM  :scared:
Could be a good unit but not cheap and depends if you can fit it in the case.
I would be tempted to just string 18650's in series and forget the balance. - or, it is simple to add a balance lead and go for the external charger / balancer. A B6 unit would work ok, the B6AC is better though as you just plug it into the mains. And, you can charge ANYTHING with it. I use it for my SLA units, NiMh units and also the Quads Lipos and the 18650 sets. Fully adjustable and programmable.
Either way, that unit your link to may be fine. Worth considering the 22V you have would almost certainly not be enough to fully charge the battery due to the voltage differential needed to the board. the batteries (a 5s) would top out at 21V. A 1v difference is probably not workable. Probably mean you would need another supply - unless you can tweak the supply you have to around 24v ?
 

Offline cd_willTopic starter

  • Newbie
  • Posts: 7
  • Country: gb
  • M6LRB
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #10 on: December 13, 2017, 04:04:56 pm »
well i have a new style battery pack and it is a s5p2
and the pack is rated for 18v 3.0Ah 45Wh
all the cells are printed inr1 18650-15m m
                                  samsung sdiem 121
and under the wrap a5dz mbk21 a1

the cells are rated up to 20amp / 1.5ah and 4 amp rapid charging safe, so 40amp / 3ah and 8amp charging if im correct



« Last Edit: December 13, 2017, 04:18:32 pm by cd_will »
M6LRB 77
 

Offline cd_willTopic starter

  • Newbie
  • Posts: 7
  • Country: gb
  • M6LRB
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #11 on: December 13, 2017, 04:36:49 pm »
eBay auction: #https://www.ebay.com/itm/18V-21V-18-5V-5S-60A-Lithium-5x-3-6V-3-7V-Li-ion-LiPo-Polymer-Battery-BMS-PCB/222353609188?epid=1440597425&hash=item33c54ed1e4:g:23IAAOSwdG9XRWjt
this bms is an option even tho it said not for power tools (but even the 150A said the same thing )
if it is the one in the picture it should be modifyable to shrink it down abit and will be able to fit a bit of a heat sink in the battery housing 

so whats peoples opinions on the
Quote
""NOT FOR Lithium POWER TOOL Battery!
If you want to use Lithium battery to replace NICD / NIMH battery, this could be a solution on Lithium battery protection. Battery must be brand new high drain battery from the same production batch. Not work for used battery!
May use either BMS or balance charger, cant use both at the same time!
This BMS can not work for Lithium power tool battery replacement. ""
M6LRB 77
 

Offline cd_willTopic starter

  • Newbie
  • Posts: 7
  • Country: gb
  • M6LRB
Re: S5 lipo battery management circuit for18v impact wrench
« Reply #12 on: December 13, 2017, 11:28:40 pm »
and what do u wrecon with wireing it up like this as this is how the cells are curently wired up in there curent pack
M6LRB 77
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf