Side by side teardown of two Makita chargers - Page 1
Forum section: electronics / projects

author: jitter
author_rank: Frequent Contributor
timestamp: October 15, 2016, 07:23:34 am
content: A couple ofweeks agoI toyed with the idea of posting a side by side teardown of two Makita chargers of different "vintages".Just for the fun of it and to see if there's much difference between a good old NiCd battery pack charger, the DC9710, and the more modern Li Ion charger, the DC10WA. Both were supplied with similar class cordless drills (almost bottom of the range, for a Makita, that is).The DC9710 can charge 7.2 V or 9.6 V NiCd packs, the DC10WA does 7.2 V or 10.8 V Li Ion packs. As is so often the case with tool battery chargers (a thing Mike, from mikeselectricstuff, mentioned in one of his vids), input voltage is not universal, 220-240 V for both of them.Having seen some consumer chargers, I can't help but be amazed at the complexity of the circuit in these Makitas, regardless of whether it was the NiCd or the Li Ion charger. The latter does balance charging, but at first glance it doesn't look all that more complex than the NiCd charger.These clearly are designed with the pro in mind who sticks in a hot battery right after depleting its charge and leaving it in the charger until needed. A fit and forget charger, so to speak.

author: jitter
author_rank: Frequent Contributor
timestamp: October 15, 2016, 07:25:34 am
content: DC9710.The IC under the battery socket is a quad comparator. Beats me why they put some soft goo around it...There's no manufacturer indicated on the pcb, but the transformer starts with "TAM" and the design clearly has strong resemblences to the "Tamura" marked DC10WA pcb.There's a mix of different brand electrolytic capacitors. Some from Nippon Chemicon, but also from TK and Jamicon. I guess they chose to go for the more expensive caps in critical locations. This charger was made at the beginning of the capacitor plague, so maybe that was just as well...

author: jitter
author_rank: Frequent Contributor
timestamp: October 15, 2016, 07:28:12 am
content: DC10WA.The two SO14 are quad opamps (LM324 clones) and the heart of the charger is a custom chip marked "DC10WA-01", but will most likely be a common Li Ion charge management IC.For this one every eletrolytic is a Samxon of different types, so now they went for a single brand instead. But this charger was made long after the end of the capacitor plague.

author: SeanB
author_rank: Super Contributor
timestamp: October 15, 2016, 10:17:26 am
content: Simple reason for the goop is that these often are used in construction, where they might be out in the rain and in use. Thus the goop so the charge controller will never fault when wet and start charging the battery way past the full charge level if the user puts in a wet pack ( either in a pocket in the rain, or it was in the tool and it sat in a puddle) and the water drips down onto the board.

author: jitter
author_rank: Frequent Contributor
timestamp: October 15, 2016, 11:33:45 am
content: I can see your reasoning, but I keep wondering.These chargers have been constructed so that any water in the battery compartment can seep out without going inside the charger. I actually recently started athreadon this feature (photos there).The reason I keep wondering: despite the drain hole, there's nothing else that would suggest that this charger (nor the drill and battery pack) are suitable for use in the rain. There aren't even any rubber seals in any of them.

author: viperidae
author_rank: Frequent Contributor
timestamp: October 17, 2016, 06:12:37 am
content: They don't look like much more than a mains step down transformer.The li-ion charge controller and balancer will be integrated into the battery.

author: Dubbie
author_rank: Unknown
timestamp: October 17, 2016, 09:13:11 am
content: I had a go at trying to reverse engineer one of these once, so that I could replace old batteries with new cells. Let's just say, it wasn't a success.Sent from my iPhone using Tapatalk

author: jitter
author_rank: Frequent Contributor
timestamp: October 18, 2016, 05:37:09 am
content: Quote from: viperidae on October 17, 2016, 06:12:37 amBasically they are just that and a bit of circuitry to cut charging when the battery is full.Given that there's an optocoupler feedback from secondary to primary, regulation is probably done on the primary side.QuoteYes for the higher voltage batteries as it would otherwise need (too) many contacts between charger and battery pack.However, I believe the the 2- and 3-cell packs (7.2 and 10.8 V) are the exception to this rule.These packs have all the requisite contacts to be able to balance charge it with the balancing circuitry inside the charger. This way Makita saves on a complex circuit inside each and every battery, most likely they will only have the standard protection.My 10.8 V pack (BL1013) has 5 terminals:The main + and - terminals with the full 10.8 V (and which are the only ones which connect to the drill).But there are also V1, V2 and T, and of course the charger mates with all of these contacts. A DMM confirmed I can measure each cell individually without tearing the pack apart.

author: Monkeh
author_rank: Super Contributor
timestamp: October 18, 2016, 11:16:00 am
content: Quote from: jitter on October 18, 2016, 05:37:09 amNot so.18V is only 5 cells remember, you only need 4 pins for the balance contacts.

author: jitter
author_rank: Frequent Contributor
timestamp: October 18, 2016, 04:27:38 pm
content: D'oh!You're right, and Imightshouldhave known...So, we have here the BL1830 which is known to have a pcb inside, is that only for protection?

author: bitslice
author_rank: Frequent Contributor
timestamp: October 19, 2016, 01:10:31 am
content: Quote from: jitter on October 18, 2016, 04:27:38 pmI believe the new 18v ones have a battery control IC inside, it disables the pack under certain fault conditions,ebay sells a frig PCB to repair them for those who want to re-cell.http://i.ebayimg.com/images/i/221539762612-0-1/s-l1000.jpgit might be a TI chip?

author: Monkeh
author_rank: Super Contributor
timestamp: October 19, 2016, 01:16:53 am
content: Yes, the current ones have an extra protection circuit in them, however, there's no charging intelligence beyond "don't charge me".

author: bitslice
author_rank: Frequent Contributor
timestamp: October 19, 2016, 01:36:15 pm
content: Quote from: Monkeh on October 19, 2016, 01:16:53 amSomewhere on t'internet I was sure there was a guy trying to communicate with the battery IC,I think he was trying to reset the "don't charge" flag, and I'm sure there was a whole bunch of battery related stuff that this chip did.

author: aaronbyron1316
author_rank: Newbie
timestamp: January 25, 2017, 10:44:30 am
content: hello!! i need some of your help guys. i bought this makita DC10WA from taiwan so the input power is 110v and when i go home to my place here in philippines my brother plug it to 220v so the charger was burn.. there for i need to buy the components that was burned but i don't know the name because it was burned. can anyone help me to find out the label of this capacitor. i already pull out the components.. i hope anyone can help me for my problem... thank you very much...

author: JoeMuc2013
author_rank: Contributor
timestamp: October 26, 2017, 12:41:34 pm
content: Similar issue here. My charger would no longer power up because two electrolytic caps failed (C1 and C2, both primary side 'behind' bridge rectifier). Both ruptured at the top and sprayed everything around them. The main fuse also failed, probably at the same time.I have replaced the caps with Panasonic quality parts and put in a new fuse, but the first attempt to power the thing up ended in the MOV blowing its top off - fortunately not right in my face but close enough. Will pay more attention to stay further away from stuff when I power it up after repairs.The brand new fuse blew as well, of courseI was able to decipher the marking on the MOV though. It reads TVR 10471 and is apparently aThinking Electronicspart that can easily be replaced by any MOV that has a breakdown voltage (is that what this is called?) of 470V and normal operation at 240V, at least that's what I believe. The fuse is a 250V / 3.15A slow blow ceramic sand-filled fuse. Unfortunately this part is hard to get with wires readily attached to it. I'm wondering anyway why Makita would not place a regular fuse holder there. How many fractions of a penny did that save? Anyway I'll place a fuse holder to make the next repair easier.There are still some doubts as to why the whole thing failed anyway. To remove the electrolytic from the PCB, I put the entire PCB into the ultrasonic cleaner yesterday evening, then cleaned it up with Isopropyl alcohol and let it dry over night. I did not 'bake' it though to remove the remaining moisture, if any. Didn't look like there would have been much anyway. On the other hand, I have also read that MOVs get weaker over time after smaller over-voltage events so it might just as well have reached its lifetime and failed for that reason.Certainly, there could also be something catastrophically wrong with the circuitry which might have been caused by the caps failing, or the caps failed because of something else failing. However, no other components show any signs of damage or aging.High voltage stuff is not actually in my focus so I am uncertain how to continue besides replacing the parts with best-fitting new ones and giving it another try. I measured some places and did not find any short circuits or unexpectedly low / high resistance values.Next test will happen outside and out of some distanceIf it fails, I will have to spend the money to buy a new charger. Sad though, I'd really like to know how to troubleshoot stuff like this and not get killed on the way.Cheers,Joe