Search found 4824 matches

by john61ct
Aug 09 2020 2:14pm
Forum: Alternative Energy
Topic: Why no 240v off grid?
Replies: 6
Views: 117

Re: Why no 240v off grid?

Solar panel voltages have no relation to the system / battery bank voltage, just need to select the right controller designed to handle your combinaton. Voltages over say 60V are very hazardous for amateur DIYers Even at 48V you're getting into EV / propulsion use cases, not "House bank" / solar sto...
by john61ct
Aug 09 2020 2:01pm
Forum: Battery Technology
Topic: What's the longest period of time you can store a Li-Ion pack?
Replies: 27
Views: 344

Re: What's the longest period of time you can store a Li-Ion pack?

To just test for go/no-go, no need for great precision. Actual remaining mAh / Ah capacity as a proportion of when new is all you need. A CC load at 0.1C to 0.3C, precisely timed easier with a $100 dummy load, but can be done with an ammeter + DMM + stopwatch. Or an Ah counting wattmeter, but that's...
by john61ct
Aug 08 2020 9:26pm
Forum: Battery Technology
Topic: Drawing slightly over rated e bike battery amps
Replies: 6
Views: 112

Re: Drawing slightly over rated e bike battery amps

Rare is the BMS that turns off the system from overcurrent. You must select one rated for higher amps than **you** plan to ever allow, as per the size of your motor, your controller limits, cav3 etc. As with selecting a fuse. Some BMSs just burn. None actually "control" or limit the amps rate afaik
by john61ct
Aug 08 2020 6:12pm
Forum: Battery Technology
Topic: battery percentage indication not right.
Replies: 1
Views: 101

Re: battery percentage indication not right.

I would never expect SoC% to be accurate.

Even with dedicated pack monitors costing hundreds, very difficult to keep them calibrated within 8-10% of reality.
by john61ct
Aug 08 2020 5:54pm
Forum: Battery Technology
Topic: What's the longest period of time you can store a Li-Ion pack?
Replies: 27
Views: 344

Re: What's the longest period of time you can store a Li-Ion pack?

Storage of **cells** is one thing, and does vary by model, chemistry, temperature etc this means fully isolated, nothing connected, only self-discharge rates to compensate for, checking and topping up monthly should be fine, even less as you become more certain voltage per cell gets nowhere near say...
by john61ct
Aug 08 2020 2:42pm
Forum: E-Bike General Discussion
Topic: Basics for Newbie///
Replies: 37
Views: 858

Re: Basics for Newbie///

Replacement pack from Amazon had no case, mount, lock, or anything, minimal charger, total AH not quite as rated, or at least not as good as the Ezee pack with the same rating, but is close and does what I need, had it 5 months so no long-term data, have noted no degradation in that short time peri...
by john61ct
Aug 08 2020 2:30pm
Forum: E-Bike Technical
Topic: Battery cycles
Replies: 8
Views: 177

Re: Battery cycles

Wow thanks John that's a lot of acronyms to Google Let me know any that aren't readily found. >So upper voltage isn't the problem. Certainly it has an impact on longevity, charging to full vendor spec and then holding a long Absorb time will kill cycles off the back end. But letting a pack sit at a...
by john61ct
Aug 07 2020 2:36pm
Forum: E-Bike Technical
Topic: Battery cycles
Replies: 8
Views: 177

Re: Battery cycles

At the bottom end, the more you leave in the pack the longer they last, so that is a judgment call, but 40% is a lot higher than most do. Resting voltage can be roughly mapped to a precise SoC% for a given pack and then guesstimate how that relates to V under load at various current rates / throttle...
by john61ct
Aug 07 2020 2:29pm
Forum: E-Bike Technical
Topic: Battery cycles
Replies: 8
Views: 177

Re: Battery cycles

At the top end while charging, backing off by 0.05 to 0.10Vpc is conducive to optimal longevity but certainly not sacrificing that much range. Besides the voltage setpoint, better to just Bulk / CV charge, stop at the setpoint or only holding Absorb / CV A few minutes if your charger AHT is not adju...
by john61ct
Aug 05 2020 3:51pm
Forum: Battery Technology
Topic: Recommended battery / BMS tester ?
Replies: 5
Views: 144

Re: Recommended battery / BMS tester ?

Well atomizing into individual cells is a requirement not matter what if you think there are cells in much worse shape than others. So long as they are connected into parallel groups their attributes are averaged out, opaque as individuals no matter the equipment used. Only way around that is to bui...
by john61ct
Aug 04 2020 10:04pm
Forum: Battery Technology
Topic: Recommended battery / BMS tester ?
Replies: 5
Views: 144

Re: Recommended battery / BMS tester ?

Testing the health of cells does not require much precision nor automation, if you aren't doing it as a business,

maybe $100 over and above the chargers/PSUs, DMM & ammeters you need anyway for regular maintenance & balancing.

Testing a BMS is also basically a manual process.
by john61ct
Aug 04 2020 10:00pm
Forum: Battery Technology
Topic: Charging Lithium Battery With Lead Acid Charger
Replies: 4
Views: 148

Re: Charging Lithium Battery With Lead Acid Charger

Volts are volts amps are amps. Plenty of chargers designed for lead work just fine for LI chemistries so long as the voltage is precisely user-adjustable, or you add external gadgets to handle the charge termination algorithm. Plenty of chargers designed for LI I would not leave unattended and/or wi...
by john61ct
Aug 02 2020 10:00pm
Forum: Items for Sale - Used
Topic: ....
Replies: 45
Views: 4031

Re: ....

Me too!

no logic

probably went off his meds
by john61ct
Aug 02 2020 9:49pm
Forum: E-Bike General Discussion
Topic: 72 Volt battery problem.
Replies: 11
Views: 266

Re: 72 Volt battery problem.

Nothing useful is served by just "running it down" other than faster wear, unless in a controlled CC load test.

Make a list of the questions we've asked so far, and track down the answers

in order for us to be able to further hep / educate you
by john61ct
Aug 01 2020 4:35pm
Forum: E-Bike Technical
Topic: How to check the condition of a battery?
Replies: 11
Views: 832

Re: How to check the condition of a battery?

yes scrap

pay more for true deep cycling batteries

Even then they need precise care to get to a couple hundred cycles
by john61ct
Aug 01 2020 4:27pm
Forum: E-Bike Technical
Topic: can I change a cheapo BMS to be 4.1 volts / cell?
Replies: 14
Views: 321

Re: can I change a cheapo BMS to be 4.1 volts / cell?

It's not like BMS that are adjustable are even that expensive

still a small fraction of what, you need to pay for quality, IOW accuracy reliability longevity.
by john61ct
Aug 01 2020 4:22pm
Forum: Battery Technology
Topic: Laudation batteries
Replies: 18
Views: 959

Re: Laudation batteries

Remember even with genuine new top notch cells

the Ah capacity IRL conditions may only be 70-80% of what the factory rating says.

Therefore at a theoretical 1C rate, the pack cannot last for an hour,

after 40min or so you should be stopping if you want any kind of longevity.
by john61ct
Aug 01 2020 4:03pm
Forum: E-Bike General Discussion
Topic: 72 Volt battery problem.
Replies: 11
Views: 266

Re: 72 Volt battery problem.

The voltage it is nominally labeled may not correspond to the usual 20S layout
by john61ct
Aug 01 2020 4:01pm
Forum: E-Bike General Discussion
Topic: How much power is too much power? (hub motor)
Replies: 42
Views: 770

Re: How much power is too much power? (hub motor)

The weight you can stand carting around is the limiting factor

power itself can always be designed around
by john61ct
Jul 30 2020 11:17pm
Forum: Vendor Relations Corner
Topic: EM3ev vs Luna Batteries and Kits
Replies: 44
Views: 4021

Re: EM3ev vs Luna Batteries and Kits

No but they got that at 0.1C or even slower, and using the most extreme voltage possible at bothe ends Not saying you haven't got a real problem, just that best case scenario the "saner" way you measure might see at least 10-15% less than the spec. If you have access to the cell/group balance leads ...
by john61ct
Jul 30 2020 5:30pm
Forum: Vendor Relations Corner
Topic: EM3ev vs Luna Batteries and Kits
Replies: 44
Views: 4021

Re: EM3ev vs Luna Batteries and Kits

Are you saying the main battery problem is that you are getting lower "actual in use Ah" capacity compared to the "theoretical / optimistic" vendor cell ratings? IME completely normal, not necessarily a indication of anything being grossly faulty. I take it you did not get a BMS that shows what's go...
by john61ct
Jul 30 2020 5:14pm
Forum: Battery Technology
Topic: Laudation batteries
Replies: 18
Views: 959

Re: Laudation batteries

Not sure I understand this. No you don't > A single cell is good for 15 amps continuous, and has no problems with 20amps peak. 3s should be good for 45amps easy in series only voltage increases, capacity in oth senses remains the same. It is the 2P that increases Ah capacity, thus ctting the C-rate...
by john61ct
Jul 30 2020 5:10pm
Forum: Battery Technology
Topic: 60v 30ah lithium battery hack
Replies: 11
Views: 200

Re: 60v 30ah lithium battery hack

If some are bad, the rest will likely follow.

Order known-good cells yourself

then either DIY or find a known good uilder to assemble for you.

I would not deal any further with those that ripped you off

assuming it did not fail from your mistreatment
by john61ct
Jul 30 2020 4:29pm
Forum: E-Bike Technical
Topic: Measuring motor current profile
Replies: 3
Views: 145

Re: Measuring motor current profile

Torque sensors as in physical torque, inside the motor? Or are you interested in power consumption at the controller output? Wouldn't current consumption at the controller input be just as informative? I imagine speed and slope would need to be logged at the same time? Check out Grin's CAv3 / Analog...
by john61ct
Jul 28 2020 8:04pm
Forum: Battery Technology
Topic: paralleling in battery packs.
Replies: 17
Views: 550

Re: paralleling in battery packs.

Are you 100% sure when you connect the new Full to the old empty, there is no flow of energy from the former into the latter?

Allowing that would waste a lot.