Search found 33 matches

by MAXIMUM_AMPS
Dec 07 2019 3:07pm
Forum: Battery Technology
Topic: Can we parallel BMSs to handle high current ?
Replies: 20
Views: 1715

Re: Can we parallel BMSs to handle high current ?

Questions : 1) What would the expert say about above designs for both diagram #1 and #2 ? 2) What are the downsides of each design, if any ? 3) What is the max number of BMSs that can be paralleled ? Only applicable to diagram #1. 4) How many bluetooth connections can we connect to a single user de...
by MAXIMUM_AMPS
Dec 07 2019 2:32pm
Forum: Battery Technology
Topic: 36 V pack not charging
Replies: 16
Views: 1338

Re: 36 V pack not charging

Sadly you'll have to replace that whole group of cells from B1 to B-, and likely the BMS board. If you know someone with a battery spot-welder, this can be done cheaply, but if not, it's very difficult.
by MAXIMUM_AMPS
Dec 07 2019 10:53am
Forum: Battery Technology
Topic: Parallel "Groups" or Parallel Strings or Neither ?
Replies: 87
Views: 6621

Re: Parallel

I thought I did, sorry if I was unclear. No need, and just want to focus on the foundation layer first, otherwise more convoluted than necessary. Those Makita modules' "lowest cell level groups" are not paralleled together, and that is the question at hand. Can the two "dimensions&qu...
by MAXIMUM_AMPS
Dec 06 2019 1:12pm
Forum: E-Vehicles General Discussion
Topic: No Solder, No welding 48v 20Ah. Cheap battery Pack
Replies: 12
Views: 2899

Re: No Solder, No welding 48v 20Ah. Cheap battery Pack

bik-e-bik-e wrote:
Dec 06 2019 1:08am
NewDesign1.jpg
Looks like a clever design! I take it those "pillars" provide the necessary clamping force to get a solid connection?
by MAXIMUM_AMPS
Dec 06 2019 1:06pm
Forum: Battery Technology
Topic: Parallel "Groups" or Parallel Strings or Neither ?
Replies: 87
Views: 6621

Re: Parallel

I know BMS is your schtick, but that's a bit premature here, any chance you could address the fundamental questions I actually asked? Is the conceptual layout itself sound? I thought I did, sorry if I was unclear. Yes the concept of modular mini-batteries is sound at a small level, and has already ...
by MAXIMUM_AMPS
Dec 06 2019 12:01pm
Forum: Battery Technology
Topic: Parallel "Groups" or Parallel Strings or Neither ?
Replies: 87
Views: 6621

Re: Parallel

I've come across this idea a few times now. Bear with me while I set a hypothetical context, and posit a "standardized" meaning for another term, besides "group" for paralleled units and "string" for series'd ones. Now "modules", for standalone-functional pac...
by MAXIMUM_AMPS
Dec 05 2019 9:07pm
Forum: E-Bike General Discussion
Topic: Regen
Replies: 41
Views: 2537

Re: Regen

Some of the comments could probably be left out, if my post was read completely "I" asked for suggestions! Money is not a problem at all. Self made. Good investments when I was young. I am however frugal, I have a big family. I do want quality products. I've only ever purchased products f...
by MAXIMUM_AMPS
Dec 05 2019 5:08pm
Forum: E-Vehicles General Discussion
Topic: No Solder, No welding 48v 20Ah. Cheap battery Pack
Replies: 12
Views: 2899

Re: No Solder, No welding 48v 20Ah. Cheap battery Pack

Wow, very substantial bus-bars.

How is the voltage drop under load? Judging only by the pics, I would think that the interface between the cell and the bars would impede the performance a bit.
by MAXIMUM_AMPS
Dec 05 2019 2:12pm
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

Interesting, why use series modules though? Is the load a passive component like a brushed DC motor? A SMPS with a wide range of input voltage? In 1S protection circuits there's often (not always) a shunt on each cell, and with coulomb counting multi-cell systems the large shunt at the bottom of the...
by MAXIMUM_AMPS
Dec 04 2019 3:46pm
Forum: E-Bike General Discussion
Topic: Looking for a 60V controller
Replies: 8
Views: 1236

Re: Looking for a 60V controller

Hi, I already have a 48V 1kw Kunteng controller. I'd like to upgrade my 13s battery to a 14s battery. The voltage will go up to 58.8V at full charge and I'm not sure that my controller will handle it, can you confirme that ? On the other hand, I'm looking for a 60V controller compatible with Eggrid...
by MAXIMUM_AMPS
Dec 04 2019 3:36pm
Forum: E-Bike General Discussion
Topic: Reputable/reliable 48v batt sellers for BBSHD build
Replies: 25
Views: 1927

Re: Reputable/reliable 48v batt sellers for BBSHD build

Solid advice in this thread, an oversized, understressed battery is a reliable one.
by MAXIMUM_AMPS
Dec 04 2019 3:33pm
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

you'll never see a protected 18650 that can come close to a unprotected 25R or VT6, because of the resistance of the shunt and protection FETs "Come close" in what? Not sure what dimension of performance you mean here. I definitely want/need modular packs that can be stacked either/both i...
by MAXIMUM_AMPS
Dec 04 2019 12:59pm
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

I agree, not much point in going modular on an ebike BMS. A single 10-14S BMS is ideal for most ebikes. Not sure why 2S or 3S units would be particularly advantageous? The advantages of using a >1S system I see: 1. Less voltage drop than a protection circuit with separate shunt resistors + 2 FETs in...
by MAXIMUM_AMPS
Dec 04 2019 11:43am
Forum: E-Bike Technical
Topic: Why doesn't a li-ion battery take load?
Replies: 24
Views: 2256

Re: Why doesn't a li-ion battery take load?

As already said, you can't believe anything about the specification of any cells with "fire" in the name. If you want to make a 36v 20-cell pack, you need high discharge rate cells, like Samsung 30Q, LG HG2, etc. Interestingly enough, the cells with "fire" in the name carry the ...
by MAXIMUM_AMPS
Dec 04 2019 11:29am
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

Could you give an example of a proper way for a 2S or 3S bms to be built, and then have the ability to put multiples together and still have the same safety factor. bms1.jpg Of course, there's 2 ways to go about it. The best way to build a modular system like that, is to use a chip that was designe...
by MAXIMUM_AMPS
Dec 02 2019 7:25pm
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

I did not say all. 99.99% being dangerous is not all. And some of the BMS most frequently causing the biggest fires do sell for thousands, paying a lot of money does not necessarily get you the security you hope for. My point is exactly as you say, BMS as backup layer of protection. That means not ...
by MAXIMUM_AMPS
Dec 02 2019 6:09pm
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

BMS is just a collection of functionality, no need to put everything into one point of failure. Balancing for example does not need to be included in the protective hardware, and IMO should not. In many use cases, a pack may only need rebalancing a few times in the first few years. Even just checki...
by MAXIMUM_AMPS
Dec 02 2019 5:49pm
Forum: E-Bike General Discussion
Topic: 48v to 72v controller overvoltage at 82v
Replies: 5
Views: 941

Re: 48v to 72v controller overvoltage at 82v

82v is very close to 84v, could be that the voltage divider circuit in the controller is slightly off... In any event, it's better in the long run to only charge the cells up to 80v or so. You get about 2x as many cycles while only losing ~10% of the capacity. (but first make sure your BMS is smart ...
by MAXIMUM_AMPS
Dec 02 2019 5:45pm
Forum: E-Bike General Discussion
Topic: 72 volt battery only chargers to 81 volts not 83volts
Replies: 14
Views: 1836

Re: 72 volt battery only chargers to 81 volts not 83volts

That is ideal, but the vast majority of BMS boards are not like that. The nicer ones with bluetooth programmability and monitoring like what EM3EV offers on their batteries is not the standard, that's an exception that puts them above the competition. All BMS units need to cut off the charger input ...
by MAXIMUM_AMPS
Dec 02 2019 5:35pm
Forum: E-Bike General Discussion
Topic: Stackable power wall kit with 18650 on ebike
Replies: 6
Views: 1381

Re: Stackable power wall kit with 18650 on ebike

hello Anyone used this for their ebike? https://s.click.aliexpress.com/e/AvtwcITKj I think it's possible to stack as many as needed but no idea on reliability on ebike with all vibration I've seen those, they're primarily made for powerwalls, and other low-current stuff. Performance is similar to t...
by MAXIMUM_AMPS
Dec 02 2019 5:22pm
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

john61ct wrote:
Dec 02 2019 1:02pm
your LISTS are invisible
Removed BBCode tags, should be visible now.
by MAXIMUM_AMPS
Dec 02 2019 5:19pm
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

That's very common for a BMS to fail and become unable to trigger OVP. Overvoltage when charging is by far the most dangerous thing possible with a Li-Ion cell! BMS should **not** control charging termination, just OVP to act as a failsafe backup for when (not if) the charger fails. Or, **if** the ...
by MAXIMUM_AMPS
Dec 02 2019 10:33am
Forum: E-Bike Technical
Topic: Should I fuse my battery?
Replies: 11
Views: 1955

Re: Should I fuse my battery?

I would use a fuse, BMS or not. Under a dead short circuit, it is possible that the BMS's FETs can go into an avalanche condition, where they are stuck ON and the BMS chip's FET driver cannot turn them off. https://www.infineon.com/dgdl/Infineon-ApplicationNote_Some_key_facts_about_avalanche-AN-v01_...
by MAXIMUM_AMPS
Dec 02 2019 8:44am
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

Sounds like you may have explained what happened when my house burned. All we know is a battery left on the charger too long burned the garage down. But I have long suspected the bms failed me somehow. Very sorry to hear that. I hope your insurance did you right. That's very common for a BMS to fai...
by MAXIMUM_AMPS
Dec 02 2019 8:07am
Forum: E-Bike General Discussion
Topic: Circuit analysis of a cheap BMS, and why you shouldn't use one
Replies: 31
Views: 3465

Re: Circuit analysis of a cheap BMS, and why you shouldn't use one

Yeah, it is hard to find good pictures really close to ANT BMS. There is some picture, but it is quite bad too. You cannot see what components they used etc. http://www.mayibms.com/d/file/shenxianyebaojiancha/2018-11-14/6dd2959d1bc68746ec97d61e36a3855e.jpg Nice find! From the pic, I believe it's a ...