Author Topic: How To: Battery pack rebuilds -  (Read 12553 times)

Offline goodfellow

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4321
How To: Battery pack rebuilds -
« on: September 24, 2018, 08:49:39 AM »
Hopefully we can use this thread to show how to do various battery pack rebuilds -- post your rebuilds as well. This was a popular thread on the previous GG site.

I love my Ryobi impact driver, but since day one the battery packs have given nothing but trouble. The Ryobi ONE Ni-Cad packs will leak down rapidly after a full charge. A full battery pack will be dead in just a day when sitting on the work bench. At first I thought there was a parasitic draw in the impact driver itself, but that wasn't case. Just leaving a pack sit idle for a day was enough to drain it. This meant that the battery packs would have to sit constantly in the charger to be ready for work -- that's not a good idea because it really shortens the life of the pack.

After two years the batteries were shot -- wouldn't hold a charge for more than 5 minutes. New packs are about $40, but then I'd be back in the same rut. So I decided to upgrade the packs with better batteries.

The OEM batteries are really cheap 1200 mAh sub-C cells. I decided to upgrade to 2500 mAh sub-C cells. Found an eBay deal for 16 cells for $14 INCL. shipping.



Sorry for the poor pics but I used my phone camera on this project. I forgot my good camera at the office. This is the pack in question





The pack is held together by some Phillips screws and is easily taken apart.



The first thing I noticed is a Thermistor that is taped to the left battery. The Thermistor is supposed to shut down the charging process in case the battery pack overheats to a very high degree due to damage or a short. This is a good thing because these packs do get abused in the field, but I think that it's the Thermistor that causes the battery pack to slowly discharge within a day or so. This is a design problem -- ?







Batteries are glued to an indexing card





Make note of how everything hooks up and gently start taking things apart.



All 15 1.2volt batteries in the case are simply hooked up in series (15x 1.2 = 18volts)



Save the index card as a template for arranging the new batteries.



The only pieces that need to be saved from the old battery connections are the connecting tabs for the Thermistor and the  step down tab for the last battery in series. The last battery in series is mounted on top of the battery pack and resides in the connection stem of the pack.





The new batteries come with cheap tabs on top which can't be repositioned to configure a battery pack structure that will fit in the battery case. So I cut the old tabs and sent away for nickel strips that can be readily soldered in any position required.





I used the indexing card to align the batteries in series and then used tape to hold them in place for soldering. First the top joints, then the bottom. I just followed the original solder patterns on the old batteries.



When everything was soldered up and positioned in place, I took a voltage reading and it showed 19.3v -- this surface charge normal for newly charged batteries. These new batteries come shipped fully charged, so I was careful to avoid accidental shorts when soldering.





Everything is buttoned back up and stuffed back in the case



The pack is inserted back in the tool and everything works. It definitely has more power -- let's hope it discharges a lot slower. The Thermistor will still leak, but I'm hoping the extra power will make the leakage less noticeable.





Took about 1.5 hours to do this job. We'll see whether it was worth it. -- LOL


NOTE: I had a few personal messages about battery sizing. Batteries are rated in milli-Ampere hours (mAh)-- which is the capacity of the  battery to discharge while under load. A higher mAh rating means the battery will last longer under load. That said, you shouldn't assume that substituting the highest mAh battery in a rebuild is OK. Higher mAh ratings also effect your charging rate and charging temperatures, and depending on the quality of your charger it may put too much load on the unit. That could cause a melt down or a short in the charger or the battery pack -- remember the Thermistor in the battery pack? If the heat gets too high, the Thermistor will shut it down and you may need a new Thermistor and/or a new charger.

Bottom line - it's best not to exceed double the mAh rating of the original battery packs. In my case it was 1200 mAh and I opted for 2500 mAh. Higher capacities are out there, but why risk it.


Offline goodfellow

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4321
Re: How To: Battery pack rebuilds -
« Reply #1 on: September 24, 2018, 08:51:42 AM »
Various Skil pack rebuilds --

Here is a Skil 18v NiCAD battery pack. These packs DO NOT use standard Sub-C batteries, but rather the smaller 4/5 Sub-C batteries; so be careful when rebuilding various packs from different manufacturers. Even though they are 18v NiCAD, some are different with regard to battery size.



These packs are a bit more difficult to take apart because Skil has tried to make it so. First off, many of these packs (not all) have a scuff guard on the bottom. It must be removed and it pries right off



Next comes the hitch. There are three obvious screws that hold the case together in a clamshell fashion. I've noted them in green on the following pic. The screw are Torx 15. However, there is another hidden screw right under the plastic plug that's circled in red. Punch out and break the plug material to get access to the remaining screw.



Now the case should split open. Some Skil batteries have the "Power Level" indicator, and some do not. Other than cutting the level decal up the middle with a razor blade to make splitting the case easier, there is no difference in the 18v NiCAD packs.



To split the clamshell case, depress the battery holding tangs on each side of the pack and pull it apart. It should split easily --



This is what you wind up with --





Now before the batteries can be removed, the two leads need to be desoldered





Now the pack can be removed and disassembled. The insulation cards on these things are a foam padding that is glued on, so there's no way to save it for reuse, but be can use cardboard paper for our own reassembly.





Here's the entire unit contents --



I ordered the batteries today (Fifteen 1600 mAh 1.2v batteries ), and we'll rebuild this pack when they arrive from HongKong-- LOL -- whenever that may be. There were no value priced higher mAh batteries available on eBay, so I stuck with 1600. I don't know the OEM spec mAh rating, but I suspect it's 1200. The markings on the OEM battery aren't clear as to what the OEM used.

Besides, the Skil 18v chargers are really a cheap design and would probably overheat or even burn up if a higher mAh battery charging load were to placed on them. So I'm being cautious on these packs.

Again, these are 4/5 Sub-C batteries, NOT the standard Sub-C versions shown in the previous battery pack repair posts.



Ok -- today the batteries arrives; 15 x 1600mAh -- total was $21 incl. from an ebay special. Prices fluctuate widely on ebay and if you watch closely for a week, the competition in this market space will get you some great deals. Case in point, I ordered 30 more 4/5 mAh batteries from a HongKong supplier for $36 incl. shipping  -- It was a one time deal, and now the same supplier is back at $44 for the same items.

First thing to do was to make some insulating shields. Simple enough; just take some poster board and copy the outline. Cut it out and use a gasket hole punch to make the center holes. These holes are needed to allow for the internal plastic battery case reinforcement tabs. The holes can also be made with an Exacto knife -- so don't fret if you don't have a gasket punch. You need three of these shields.







Now I use one of the shields as a pattern to arrange the batteries in series and to position the tabs for soldering. To keep everything temporarily aligned, I tape the batteries with electrical tape. On some battery packs there is enough room in the case so the tape can be left in place. Unfortunately, these Skil cases are tight, so the tape will have to come off before reassembly.



Once the lower layer is positioned and soldered up, the upper shield is glued in place with hot glue and the top layer of batteries are soldered in place. The important thing to remember is that the batteries are connected in series and even tough they are stacked, the batteries must be properly connected so that you end up with only one + (pos) and one - (neg) tab at the end of the entire process. Make a diagram if you have to, to help with the soldering pattern.



Now comes the important part. Once the batteries are properly soldered in series; first test them to see if you actually have about 18v of power. If not, the you soldered something wrong, or you missed a solder joint. If it's a short, you should have smelled it by now!! --LOL

The soldered batteries MUST be installed into the side of the shell that has all the wiring attached. That way the batteries will be properly oriented for making the connections. The red wire in the shell gets soldered to the +(pos) battery tab, while the blue wire is soldered to the -(neg) battery tab. Depending on your soldering skills, a bit of electrical tape to protect the soldered tab ends may be called for to prevent a short. The space is tight --

Now the next pic show the proper orientation of the locking switch for the battery pack. The spring must rest against the spring stop, and only the wired side of the battery shell has the stop molded into position. You can't position the lock on the opposite shell because you'll never get the lock spring to stay in place.



Next, install the small "Power Level" circuit board -- this just slides into two runners. Very easy to do, but almost impossible to photograph, so just trust me, you'll know where that little chip must reside.



Now, do a quick check to see if you still have at least 18v power coming from the batteries -- a little higher is OK. The surface charge on these batteries will usually indicate a bit higher than 18 volts. This is it; time to install the other side of the clamshell battery pack casing. Leaving the wired side of the case lying on a table, slide the other side on top.

In order for this side to match up, you MUST pull the battery pack lock downward so the tabs will clear the side that your trying to install. Don't force anything, and take your time. These packs are tight so be careful. Better to try several times rather than pushing too hard.

Once the two shells come together, and before you screw them together, check the voltage one more time --





If everything checks out, screw the two sides together and call it a "job well done"!!



Good luck!









Offline goodfellow

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4321
Re: How To: Battery pack rebuilds -
« Reply #2 on: September 24, 2018, 08:53:51 AM »
A slightly different version of the Skil 18v battery pack. This is the version that doesn't include the charging indicator on the rear of the pack, so in all respects this pack is simpler to rebuild. As in the previous example, the pack is separated by punching out the lower left hand corner plug to gain access to the hidden screw.







To separate the case once the screws are removed, you simply push down on one side of the battery locking tabs and the case pulls apart.





The thermistor is taped to one of the batteries



The entire center plate of the battery pack removes as well to reveal all the connections. Blue wire is -negative, and Red is +Positive





Leave the thermistor alone and unsolder the positive and negative leads. Leave the battery pack in tact to act as a guide for assembling the new pack.







IMPORTANT: In the following pic note how the top stack is connected to the bottom, The center "red" circle indicates how the connection is made from the lower stack to the top stack. One side of the  connection is from the top lead of a battery that resides in the lower stack, while the other side is the lower lead from a battery that resides in the top stack. These two connections need to be soldered to join both stacks.

What you really need to take into account is that you need to wind up with one positive connection on one end of the stack (the green circle in the pic), and one negative connection on the other end (the blue circle).



This is what you should wind up with -- the other half of the cover can now be installed and you're ready with a new battery pack.



Good luck!!


Offline bonneyman

  • Hero Member
  • *****
  • Posts: 3953
Re: How To: Battery pack rebuilds -
« Reply #3 on: September 24, 2018, 10:04:37 AM »
Good tutorial!

I pulled apart one of my Makita 9.6 volt sticks, but then found a total of 4 batteries shorty thereafter, so didn't rebuild it. I noticed the thermistor but also what looked like a diode. Not being an electronics sort of guy I'm not at all sure. But as I recall it was soldered from one terminal - across two cell cases - and then to another terminal that is only used during charging. I'm thinking the diode is preventing too high of a current during the charging cycle (while the thermistor prevent cell overheating).

So I have one blue Makita drill cordless, and I modified another Makita drill to run off of an old car battery charger. I'm set.

P.S. What brand is your digital meter in the pics? Looks suspiciously similar to my old clamp meter on the left.

Offline goodfellow

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4321
Re: How To: Battery pack rebuilds -
« Reply #4 on: September 24, 2018, 10:08:17 AM »
The meter is an old HF CenTech brand -- just used for general around the house duty.

Offline oldnslo

  • Hero Member
  • *****
  • Posts: 712
Re: How To: Battery pack rebuilds -
« Reply #5 on: September 24, 2018, 02:27:03 PM »
Ok, so I found my old Porter Cable 14.4 v drill driver. Found the batteries on fleabay. My one concern is soldering heat. If I go slow, and cool between solderings, it seems to be ok based on my web research.

A similar battery rebuild is here, tho my 14.4 configuration does not have the last battery standing up top.

 <-- long vid.

I have to wrestle with if the upgrade is worth the time/effort, since I use it very little, or just kick it to the curb at a garage sale.

Offline goodfellow

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4321
Re: How To: Battery pack rebuilds -
« Reply #6 on: September 24, 2018, 02:43:31 PM »
No worries about soldering heat OnS. Most new batteries have long enough tabs to allow easy placement and configuration and to minimize heat transfer to the battery core. Many of the older batteries had short tabs and I used separate nickel strips to complete the soldering, but these days with longer tabs that's no longer a worry

Offline daves_not_here

  • Full Member
  • ***
  • Posts: 125
Re: How To: Battery pack rebuilds -
« Reply #7 on: July 30, 2019, 03:11:00 PM »
How's that Ryobi battery holding up?
David

Offline goodfellow

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4321
Re: How To: Battery pack rebuilds -
« Reply #8 on: July 30, 2019, 03:36:51 PM »
How's that Ryobi battery holding up?

Very well - just rebuilt a few more that I bid for on eBay- they were cheap because they were DOA - but allL needed was the housing anyway. Now I have six packs - 4 NiCD and 2  Li.


Sent from my iPhone using Tapatalk

Offline muddy

  • Hero Member
  • *****
  • Posts: 3467
Re: How To: Battery pack rebuilds -
« Reply #9 on: July 31, 2019, 08:05:16 PM »
I need to get on it and repair a Milwaukee battery I have.

Sent from my E6910 using Tapatalk


Offline daves_not_here

  • Full Member
  • ***
  • Posts: 125
Re: How To: Battery pack rebuilds -
« Reply #10 on: August 10, 2019, 11:28:38 AM »
How's that Ryobi battery holding up?

Very well - just rebuilt a few more that I bid for on eBay- they were cheap because they were DOA - but allL needed was the housing anyway. Now I have six packs - 4 NiCD and 2  Li.

Nice. I guess I should have kept some of the dead ones I turned in at HD.
David

Offline goodfellow

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4321
Re: How To: Battery pack rebuilds -
« Reply #11 on: September 27, 2022, 02:05:38 PM »
It's been a while since I rebuilt some battery packs, but after five years the Skil 18V packs (the same ones as in the posting above) needed to be rebuilt again. Like I always do, I find the best price on bulk batteries on ebay, solder them in series, and we're good to go. That said, it's not so easy these days.

Batteries from Asia (China mostly) seem to have some serious quality problems in that they won't hold a charge and deteriorate very quickly. It's better to pay a few dollars more for batteries from reputable merchants, than just ordering the cheapest set. I'm looking for some good quality Sub-C and 4/5 Sub-C batteries to rebuild my Ryobi and Skil 18v packs.

Supply chain issues aside, getting quality parts these days (regardless of type) seems to be quite a struggle. I hear the same complaints about Chinese produced automotive and electronic parts.

Offline muddy

  • Hero Member
  • *****
  • Posts: 3467
Re: How To: Battery pack rebuilds -
« Reply #12 on: September 27, 2022, 08:40:07 PM »
With the advancement in Battey and tool technology within the 5 yrs. Is it still a cheaper/viable choice to rebuild?


Not judging one bit Ray, just curious of it still pays. I have some snap on battery's that could use rebuild.


Sent from my Pixel 6 using Tapatalk

Offline goodfellow

  • Global Moderator
  • Hero Member
  • *****
  • Posts: 4321
Re: How To: Battery pack rebuilds -
« Reply #13 on: September 27, 2022, 09:43:26 PM »
With the advancement in Battey and tool technology within the 5 yrs. Is it still a cheaper/viable choice to rebuild?


Not judging one bit Ray, just curious of it still pays. I have some snap on battery's that could use rebuild.


Sent from my Pixel 6 using Tapatalk


Inflation being on a roar right now Tim, I'm seeing prices for battery packs climb quite rapidly. Also, my Skil cordless tools are 15 years old and the battery packs have been discontinued for quite a while.  I can get knock-offs, but they're pretty worthless.

I can rebuild a pack in short order these days, and if the batteries are of good quality I'm ahead of the game.