Search found 211 matches

by eMark
Mar 08 2020 4:32pm
Forum: Battery Technology
Topic: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.
Replies: 17
Views: 522

Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

It is my preference to ignore $ cost for this discussion, since that could complicate things in a non-physics way that could make this discussion messy and vague. Being your preference is to ignore $ cost what is the reason you are set on 1p (21700) or 2p (18650) instead of 3p 18650? Is your applic...
by eMark
Mar 08 2020 12:38pm
Forum: Battery Technology
Topic: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.
Replies: 17
Views: 522

Re: Batteries involving 40T, 30Q and MJ1 cells. Preferences and opinions.

There are too many unknown variables ... not enough specifics (application) to offer another/different opinion at this time. That said, assuming you can adequately justify your reasoning for these 4 choices should we disagree? It's your money, your DIY build, your specific application, your preferen...
by eMark
Mar 07 2020 5:40am
Forum: Battery Technology
Topic: Need help with the battery
Replies: 2
Views: 353

Re: Need help with the battery

I know that the discharge rate of this battery is too big and i want to use a 20s 100A BMS, is it possible to use this BMS without ant problem? or im gonna set something of fire? 50A peak is a stretch when it's spec sheet says 20A max continuous discharge (20Ax7=140A). Also this ES thread suggests ...
by eMark
Mar 06 2020 4:09pm
Forum: Battery Technology
Topic: Paralleling uneven voltage cells?
Replies: 49
Views: 2147

Re: Paralleling uneven voltage cells?

If I have two identical cells, one at 3.75V and the other at 4.10V and I spot weld a nickel strip to the positive and negative of both to parallel them , how fast will it take the two cells to level each other ? Will it be a super fast almost making the nickel red kind of current share or a steady ...
by eMark
Feb 27 2020 9:58am
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

AGREE! :thumb: Even though twilloug's EVE battery may be overrated at 30.6 amps max continuous discharge it's still good for short bursts of 30A (15-30 sec). The previous suggestion of connecting a 7S balance lead ... https://www.amazon.com/uxcell-Balance-Connector-Extension-Charger/dp/B07GN7S7BM/re...
by eMark
Feb 26 2020 10:15am
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

I did some research and the 18650 cells in my battery have a max continuous discharge current of 7650mA each. So with 4 in parallel, that would be a max of 30.6. So my 28amp motor and 30amp controller should be fine right. Note the cells are eve ICR18650 26V cells. Based on my last post, if my batt...
by eMark
Feb 26 2020 2:04am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 377
Views: 37711

Re: Li-ion cells cycle ageing

Realistically, doesn't that "If" become more of a challenge the more P-groups (e.g. 10S4P vs 14S8P) even with top brand name grade A cells as the battery ages. I again ask administrators to ban this trolling member acces to this thread. eMark is responsible for weed infestation also in other thread...
by eMark
Feb 25 2020 1:18pm
Forum: Battery Technology
Topic: What is wrong with this product?
Replies: 15
Views: 899

Re: What is wrong with this product?

28ah for a 3p 18650 pack? not a chance. that's over 9ah per cell. i find it more likely that they are using garbage cells with only a few hundred mah per cell, so the *total* combined capacity of all the cells in *1s*, 3.7v, might be 28ah (just like the many "starter" and "accessory" packs on ebay ...
by eMark
Feb 25 2020 12:02pm
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

As it is now his 7S4P 30.6A EVE ebay battery will be too stressed with the 30A controller especially at full throttle. Besides the actual max discharge current of his Chinese ebay battery may be closer to 26A. There is no "huge boost in power" as you contend with his 30A controller and 500W motor. T...
by eMark
Feb 24 2020 12:10pm
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 377
Views: 37711

Re: Li-ion cells cycle ageing

It is simple. If my paralel groups are within 3 mV, resolution 0,1 mV is must for reliable and repeatable measurement. Realistically, doesn't that "If" become more of a challenge the more P-groups (e.g. 10S4P vs 14S8P) even with top brand name grade A cells as the battery ages. Requirement of ten t...
by eMark
Feb 24 2020 10:00am
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

Just to clarify ... if my battery is rated for 30.6 amps continuous draw, am i ok with 7s4p battery or do i need to go with different battery If so what size? Everything else is new why not another battery. :D Do you have space to double up the existing battery? The second one can be higher quality...
by eMark
Feb 23 2020 3:19pm
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

My biggest folly was not realizing that I was stepping into a preexisting pissing match while looking for a bit of thoughtful discussion. It's an ES thread that made it's way past the first page... I should have known better. I hope that the OP is able to find the information he is seeking. It's no...
by eMark
Feb 23 2020 1:44pm
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 377
Views: 37711

Re: Li-ion cells cycle ageing

Until you check the real voltages (first without BG-8S, then with BG-8S connected) with external voltmeter having sufficient resolution 0,1 mV and sufficient input resistance, you have no idea what´s truly going on. You do realize that 0,1mV is actually 0,0001V. It isn't necessary to have a DMM tha...
by eMark
Feb 23 2020 11:50am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 377
Views: 37711

Re: Li-ion cells cycle ageing

Until you check the real voltages (first without BG-8S, then with BG-8S connected) with external voltmeter having sufficient resolution 0,1 mV and sufficient input resistance, you have no idea what´s truly going on. Padja where are you when i could use your moral support :) docware thinks he's talk...
by eMark
Feb 23 2020 11:23am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 377
Views: 37711

Re: Li-ion cells cycle ageing

Citation from iSTD BG-8S manual : „Voltage measurement accuracy : ± 0,005 V @ 4,2 V“ You have to also take into consideration that iSTD unit is supplied from some measured cells – another factor affecting the voltage. Resulting inaccuracy may be 10 – 40 mV, or more, who knows. Until you check the r...
by eMark
Feb 23 2020 11:19am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 377
Views: 37711

Re: Li-ion cells cycle ageing

Thanks! Maybe, i got a really good BG-8S or i don't have a good enough DMM ... or, maybe because the comparison was at 3.75V ... anyway close enuf for my scientific notation :wink:
by eMark
Feb 23 2020 10:19am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 377
Views: 37711

Re: Li-ion cells cycle ageing

I am sorry, but those various cell monitors are not only often inaccurate and therefore misleading, but also can contribute to real disbalance of the parallel groups. Tend to agree, but when it comes to the iDST BattGo 8S it's more than a monitor and more reliable (+/- 2mV) than a cheap cell monito...
by eMark
Feb 23 2020 8:54am
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

Again thank you everyone for your comments. I did some research and the 18650 cells in my battery have a max continuous discharge current of 7650mA each. So with 4 in parallel, that would be a max of 30.6. So my 28amp motor and 30amp controller should be fine right. Note the cells are eve ICR18650 ...
by eMark
Feb 23 2020 8:21am
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 377
Views: 37711

Re: Li-ion cells cycle ageing

Hear you loud and clear ... that's why it was a comment by docware on another thread that most influenced me to build my pack (without BMS) that can be split in two for balance charging (when needed being battery is 30Q) with duo 6S balance charger. Can also have two of those little cell-log monitor...
by eMark
Feb 22 2020 6:13pm
Forum: Battery Technology
Topic: Li-ion cells cycle ageing
Replies: 377
Views: 37711

Re: Li-ion cells cycle ageing

Yes, I agree that cheap simple voltmeter is very efficient SOC gauge, especially for other chemistry like NCA or NMC. Just recommend to check the real values with an external DMM once or twice per year.... That gets done more like 2-4 times a year when I manually check balance, since I don't use Ba...
by eMark
Feb 22 2020 5:10pm
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

Sometimes when we challenge what we think we know, we learn that we had been mislead. https://youtu.be/Y0T5-a104p0 I stand corrected. You're not the only one. It invariably happens to all of us, even an ES expert. Some may even go so far as to call out someone for being "Dead wrong!" then later lea...
by eMark
Feb 22 2020 4:53pm
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

It's not a difficult question. If it applies to a $15 BMS then it possibly applies to most all BMSs unless one is defective from factory. Is the following claim bogus or true? If it's even partially true please explain ... Getting back to this inexpensive BMS ... https://www.amazon.com/Protection-Ch...
by eMark
Feb 22 2020 3:55pm
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

Sorry, could you be more explicit about what you learned? IMR I believe was only used for LMO but yes INR can vary, mostly NMC & LCO He explained it already that acronyms like ICR and IMR are more general as they don't reference the inclusion of all the tangible ingredients (e.g. Lithium, Cobalt, N...
by eMark
Feb 22 2020 3:43pm
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

Sorry, could you be more explicit about what you learned? IMR I believe was only used for LMO but yes INR can vary, mostly NMC & LCO He explained it already that acronyms like ICR and IMR are more general as they don't reference the inclusion of all the tangible ingredients (e.g. Lithium, Cobalt, N...
by eMark
Feb 22 2020 3:33pm
Forum: Battery Technology
Topic: Lithium battery question
Replies: 78
Views: 4714

Re: Lithium battery question

That brings up something that no one seems to know (for sure) the answer to when it comes to BMSs. Are they really just a BPS (Protection) as some claim? Or if they are capable of balancing (BMS) a battery how and to what extent? Previously posted the following earlier in this thread with no reply. ...