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by john61ct
Nov 14 2019 9:12am
Forum: Battery Technology
Topic: Max safe Voltage Difference when connecting two Batteries in parallel
Replies: 46
Views: 876

Re: Max safe Voltage Difference when connecting two Batteries in parallel

Ambient temperatures when I ride are usually 10-30 degrees. Did you already try what happens to GA cells after about 100 cycles when charging them at 1C at temperatures about 25 degrees? ° C or F ? If C then you need to make **sure** the inside core of those batteries are warmed up **before you** s...
by john61ct
Nov 14 2019 9:09am
Forum: Battery Technology
Topic: Max safe Voltage Difference when connecting two Batteries in parallel
Replies: 46
Views: 876

Re: Max safe Voltage Difference when connecting two Batteries in parallel

nominal 35Ah pack @52Vnominal, 56-57V charging _______ Grin Satiator is a great little adjustable charger, very safe and reliable, perfect gentle charge for your pack at 8A Can be stacked when you want to go faster. About $300 _______ Also to consider, I have dozens of voltage-adjustable Mean Well H...
by john61ct
Nov 14 2019 7:20am
Forum: Battery Technology
Topic: Acceptable Battery Sag
Replies: 4
Views: 84

Re: Acceptable Battery Sag

There are plenty of other options too, both approaches and devices, but rarely used in this context.
by john61ct
Nov 14 2019 3:34am
Forum: Battery Technology
Topic: Acceptable Battery Sag
Replies: 4
Views: 84

Re: Acceptable Battery Sag

Don't use a BMS that does not let you adjust the parameters to your liking.

Or use another method for balancing entirely.
by john61ct
Nov 14 2019 1:12am
Forum: Battery Technology
Topic: Max safe Voltage Difference when connecting two Batteries in parallel
Replies: 46
Views: 876

Re: Max safe Voltage Difference when connecting two Batteries in parallel

Sounds similar to @method's approach, just using resistors.

Wire length x gauge can do the same to limit current I'm told, fine-stranded boat cable, high temp insulation (silicone?)

Start with a lower V delta, use an infrared thermometer, be conservative about ramping the delta V higher. . .
by john61ct
Nov 14 2019 1:05am
Forum: Battery Technology
Topic: Building 13S17P battery, need some criticism on layout
Replies: 7
Views: 245

Re: Building 13S17P battery, need some criticism on layout


crazyfrog wrote:Looks like you’re using loads of little round cells if you used one big triangular cell it would fit much better and take less time to make.
Interesting. Could you link to such a product? What chemistry puts out such high voltage with just one cell? Never seen a triangular one. . .

by john61ct
Nov 14 2019 12:59am
Forum: E-Bike General Discussion
Topic: Why not comfort bikes?
Replies: 80
Views: 2122

Re: Why not comfort bikes?

i only build bikes with 22" wheels or smaller these days Well for mainly dirt / gravel desert & forestry tracks I just can't see going that small. Fattie tires is suspension, so maybe 24" rim, gets to what circumference? And I fully agree with "comfort bike platform" as opposed to the usual competi...
by john61ct
Nov 14 2019 12:30am
Forum: Battery Technology
Topic: New 14s battery pack, US18650VTC6 vs NCR18650GA
Replies: 177
Views: 4796

Re: New 14s battery pack, US18650VTC6 vs NCR18650GA

Well 3.85Vpc is much better than over 4V. And a couple days not as bad as a couple weeks. There are no hard numbers, all greyscale, too many variables, how do you even define "damaging"? And such factors get lost in the noise if the use case demands very high C-rates or avg DoD cycling, or very hot ...
by john61ct
Nov 13 2019 11:33pm
Forum: Battery Technology
Topic: Li-ion battery pac charger advice
Replies: 5
Views: 115

Re: Li-ion battery pac charger advice

Well if you'd post links to the datasheets of the exact motor and controller in question, someone might chip in with a yes or no, but ideally they'd have actual experience with that hardware. IMO maybe the motor if you temp-derated with a new controller, but who knows just a flying blind guess. The ...
by john61ct
Nov 13 2019 11:09pm
Forum: E-Bike Technical
Topic: RPM-Based Current Throttle
Replies: 4
Views: 114

Re: RPM-Based Current Throttle

Plus the included step-up boost converter circuitry, can use it for charging the pack!
by john61ct
Nov 13 2019 11:06pm
Forum: General Discussion
Topic: Links to Breakdown / modification of Meanwell (clone) PSU
Replies: 1
Views: 52

Re: Links to Breakdown / modification of Meanwell (clone) PSU

Great learning project.

I'm looking for something along similar lines, but adding current adjustment, ideally under mcu control, maybe via CAN

Actually, DC-DC would be more flexible, but the cheap chinese stuff tends to be pretty limited in actual power realistically, not much over 20A.
by john61ct
Nov 13 2019 8:56pm
Forum: E-Bike Technical
Topic: 3-speed switch
Replies: 5
Views: 142

Re: 3-speed switch

Is there any scheme where that sort of adjustment affects the power distribution at a given power level, to favour rpm vs torque?

So level 1 for extra strength at lower speeds, 2 for default / normal, 3 for getting a higher top speed?
by john61ct
Nov 13 2019 8:52pm
Forum: Battery Technology
Topic: AliExpress battery pack unboxing (for my eZuma project)
Replies: 237
Views: 13771

Re: AliExpress battery pack unboxing (for my eZuma project)

Wow, sweet.

Think they'd be robust enough to handle the twisting of a front hub motor?
by john61ct
Nov 13 2019 5:03pm
Forum: Battery Technology
Topic: Max safe Voltage Difference when connecting two Batteries in parallel
Replies: 46
Views: 876

Re: Max safe Voltage Difference when connecting two Batteries in parallel

At 25°C just accept the maker's datasheet. Go warm enough, even 1C is no problem at all, maybe even higher. Go colder and even the lower rates are not optimal for longevity. Lithium tolerates being fast charged at Ambient temperature Well in Alaska at the moment, ambient may be well below freezing,...
by john61ct
Nov 13 2019 4:48pm
Forum: Battery Technology
Topic: New 14s battery pack, US18650VTC6 vs NCR18650GA
Replies: 177
Views: 4796

Re: New 14s battery pack, US18650VTC6 vs NCR18650GA

As a general rule it was my understanding that it's better to go with an 80% charge and 50% discharge than an 80% charge and 80% discharge? Maybe, for some an 80% charge and 65% discharge is the happy medium that best suits one's daily ebiking routine. Here's a real-life scenario that may be simila...
by john61ct
Nov 13 2019 2:36pm
Forum: E-Bike General Discussion
Topic: Why not comfort bikes?
Replies: 80
Views: 2122

Re: Why not comfort bikes?

best geared hub hits something like an 84% peak efficiency whereas a DD hub of the same continuous wattage can be up to 90% … lower power requirements, IE 25-30mph Well efficiency is great for range at cruising speed or mild inclines. My critical need is for super high torque, high power when going...
by john61ct
Nov 13 2019 2:18pm
Forum: E-Bike General Discussion
Topic: Why not comfort bikes?
Replies: 80
Views: 2122

Re: Why not comfort bikes?

Right, and I think the geared hub's down side is really more that heat issue, than efficiency lost in the gearing - I mean, that's where the heat comes from, but the direct drives are mainly just better at shedding it I think the ability to derate current based on overtemp is critical. By default I...
by john61ct
Nov 13 2019 2:04pm
Forum: Resources & EV Related Parts and Services
Topic: K2 LiFePO4 batteries
Replies: 1
Views: 49

Re: K2 LiFePO4 batteries

I have yet to see evidence that K2 makes consistently good quality cells that last anywhere near as long as genuine CALB, GBS, Sinopoly, Winston, A123 et al even when brand new and proven Grade A from a trusted seller. I consider 70% SoH to be EoL, most industry uses 80%. Personally, any secondhand ...
by john61ct
Nov 13 2019 11:27am
Forum: Battery Technology
Topic: Bilding a 'distributed' 3s 6p Li-Ion pack
Replies: 9
Views: 191

Re: Bilding a 'distributed' 3s 6p Li-Ion pack

For charging all the sub-packs in parallel from one charger. Ideally individually fused, otherwise need to ensure only doing this with healthy packs. Reliable supplier, many styles. https://www.progressiverc.com/charging/charge-boards https://www.google.com/search?q=site%3Aprogressiverc.com+Self-res...
by john61ct
Nov 13 2019 9:50am
Forum: E-Bike Technical
Topic: RPM-Based Current Throttle
Replies: 4
Views: 114

Re: RPM-Based Current Throttle

And motor voltage is constantly varying. . .
by john61ct
Nov 13 2019 9:49am
Forum: E-Bike General Discussion
Topic: Why not comfort bikes?
Replies: 80
Views: 2122

Re: Why not comfort bikes?

This applies to DD hubs only right?

Geared hubs are generally less raw power, but are there exceptions?

Ability to shed heat becomes critical too, when climbing steep hills with heavy loads.

My thinking is multiple motors. . .
by john61ct
Nov 13 2019 9:28am
Forum: Battery Technology
Topic: Bilding a 'distributed' 3s 6p Li-Ion pack
Replies: 9
Views: 191

Re: Bilding a 'distributed' 3s 6p Li-Ion pack

I have never seen that balance hub. The idea is each #1 cell in every pack is paralleled, also #2 and #3. So each of those triplets self-balance within the set. That has nothing to do with balancing between those sets connected in series, usually done with the charger, or BMS, but can also be a sep...
by john61ct
Nov 13 2019 9:23am
Forum: Battery Technology
Topic: Bilding a 'distributed' 3s 6p Li-Ion pack
Replies: 9
Views: 191

Re: Bilding a 'distributed' 3s 6p Li-Ion pack

Balancing only happen while charging, the charger will balance the packs when nearly full, it will bleed the high cells and let the other cells catch up. That is only true for a particular style of balancing circuits. Yes the most common style, but there are many devices that do it differently, and...
by john61ct
Nov 13 2019 9:19am
Forum: Battery Technology
Topic: Bilding a 'distributed' 3s 6p Li-Ion pack
Replies: 9
Views: 191

Re: Bilding a 'distributed' 3s 6p Li-Ion pack


ThomasEekels wrote:Parallel first is not an option
Why not?

You will definitely see imbalance issues between the modules going that way, even with active balancing gear at that level,

resulting in reduced performance and shorter lifespan.