Search found 6031 matches

by john61ct
Apr 14 2021 3:41pm
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1328
Views: 203700

Re: kWeld - "Next level" DIY battery spot welder

Yes better to rig a current-limiting circuit that does not vary so much as voltage / SoC drops. Of course a PSU / charger powerful enough to "just barely almost" keep up with the welder's Ah/minute consumption would allow for a smaller battery, just using it as a short-term buffer, maintai...
by john61ct
Apr 14 2021 12:04am
Forum: Battery Technology
Topic: Super fast charge
Replies: 16
Views: 364

Re: Super fast charge

You of course **can** charge from a 100% Full pack to an "empty" one but then if they are the same Ah capacity, bith are now at 50%. You need to (MUST for safety) limit the current transfered when initially paralleling them. Both problems can be solved with a quality DC-DC **charger**, but...
by john61ct
Apr 11 2021 9:57pm
Forum: Battery Technology
Topic: Super fast charge
Replies: 16
Views: 364

Re: Super fast charge

Since you have two identical batteries, just set them up to swap easily? Better (safer simpler easier) to charge one pack at a time but if you really want to parallel them, do so at the cell/group level 1S so whatever you are using to keep the packs in balance can monitor at that level to prevent an...
by john61ct
Apr 11 2021 9:49pm
Forum: Battery Technology
Topic: Super fast charge
Replies: 16
Views: 364

Re: Super fast charge

Get a charger (or PSU, or DC-DC converter) that allows you to custom-adjust both maximum setpoints, CV and CC current.

If your source is cheap grid power, don't need to be too concerned about efficiency.

Auto-termination is IMO much more important, safety first.
by john61ct
Apr 11 2021 12:30pm
Forum: Battery Technology
Topic: Super fast charge
Replies: 16
Views: 364

Re: Super fast charge

LTO chemistry is an exception, 10min charge NP

But much lower energy density, for a low speed dump truck or big bus maybe
by john61ct
Apr 11 2021 12:28pm
Forum: Battery Technology
Topic: Super fast charge
Replies: 16
Views: 364

Re: Super fast charge

Current **limiting** is not a function of any BMS I know of. Most don't even have current protection, they just give a rating - usually too optimistic - and release the magic smoke if current is allowed to go too high. Charging very fast can greatly reduce pack lifespan, especially in cool weather. ...
by john61ct
Apr 11 2021 12:22pm
Forum: E-Vehicles General Discussion
Topic: Battery Three way switch - any issues with this design?
Replies: 8
Views: 383

Re: Battery Three way switch - any issues with this design?

at a given voltage, drawing at a lower C-rate results in higher Ah capacity regardless of resistance, heating losses etc A 0.1C rate will show higher capacity than a 0.3C rate. So, swapping out three 30Ah batteries sequentially gives less range than one 90Ah battery See Peukert's Law Unless maybe if...
by john61ct
Apr 11 2021 11:57am
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1328
Views: 203700

Re: kWeld - "Next level" DIY battery spot welder

Apparently the welding circuitry does not limit current drawn, I've read about batteries delivering "too much" power? I was hoping (if that is the case) there might be guidelines for getting to "as much as possible without going over". Or maybe going to big lead units would be be...
by john61ct
Apr 11 2021 12:18am
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1328
Views: 203700

Re: kWeld - "Next level" DIY battery spot welder

So what are the pack specs to get top output power?

Voltage range?

Actual peak vs continuous maximum amps drawn?

What are the specs that might get to be "too much"?

Would a pack tested capable of true 25C continuous be better or worse than one that can only handle 15C?
by john61ct
Apr 09 2021 6:04pm
Forum: E-Vehicles General Discussion
Topic: Battery Three way switch - any issues with this design?
Replies: 8
Views: 383

Re: Battery Three way switch - any issues with this design?

yes all DC circuits should have a Common Reference, tied in with Negative Returns
by john61ct
Apr 09 2021 12:33pm
Forum: Battery Technology
Topic: Isolation between cells needed?
Replies: 4
Views: 279

Re: Isolation between cells needed?

Aha I thought you meant electrical isolation, like diodes or circuit protection between groups

rather than physical protection, insulation
by john61ct
Apr 09 2021 12:15pm
Forum: E-Vehicles General Discussion
Topic: High Power power supply for testing EVs motors controllers without battery pack
Replies: 3
Views: 314

Re: High Power power supply for testing EVs motors controllers without battery pack

But why?

How many watts for how long are needed?

Even a low Ah pack will deliver much more power than you could with a reasonable PSU

and if warm, then fully recharge in 10min or so, without losing too much lifespan.

So two more normal PSU/chargers, two packs, swapped out. . .
by john61ct
Apr 09 2021 9:27am
Forum: Battery Technology
Topic: Isolation between cells needed?
Replies: 4
Views: 279

Re: Isolation between cells needed?

If by group you mean (as is standard) cells in parallel only, at the "lowest" level in the layout at 1S voltage, then those (cell) groups connected together to create one series string then No there is no current flow possible between those groups, they do not affect each other even if at ...
by john61ct
Apr 09 2021 9:15am
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 505
Views: 85961

Re: Spot Welding Copper Strips to 18650 Battery Cells

Think of each section (sub pack?) involving strips, whether soldered or welded as a rigid monolithic block, no flexing stresses allowed at all. Then the flexible wiring with zero solder involved, connecting between those blocks, their connection ends well supported so the crimped terminations are (o...
by john61ct
Apr 09 2021 9:07am
Forum: E-Vehicles General Discussion
Topic: Battery Three way switch - any issues with this design?
Replies: 8
Views: 383

Re: Battery Three way switch - any issues with this design?

You'll get longer range (higher actual Ah capacity) by paralleling for the whole ride.

Better current flow, less voltage sag and longer lifespan too.
by john61ct
Apr 08 2021 11:01pm
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 505
Views: 85961

Re: Spot Welding Copper Strips to 18650 Battery Cells

I am not talking about strip, at all. I am saying, where you are using the wire I spec'd to accommodate flexing, abstain from touching that wire with any solder. If you are connecting wire to strip, then do so via solid connectors with a wide contact surface area crimped to the wire, perhaps quality...
by john61ct
Apr 08 2021 7:33pm
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 505
Views: 85961

Re: Spot Welding Copper Strips to 18650 Battery Cells

No solder terminations, use crimp connections.

Again, no flexing until you get well into the insulated wire body.
by john61ct
Apr 07 2021 6:52pm
Forum: EScooters/EMotorcycles
Topic: Finding a battery - Alibaba?
Replies: 9
Views: 298

Re: Finding a battery - Alibaba?

LFP is only rarely used for EVs. Much longer lifespan, thus better value by far much safer, thermal runaway (boom, fire) less likely but also lower energy density, thus slower performance and/or lower range. Tesla using it in the China-produced models only. Otherwise the 3.6 - 3.7Vnominal chemistrie...
by john61ct
Apr 07 2021 6:44pm
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 505
Views: 85961

Re: Spot Welding Copper Strips to 18650 Battery Cells

Fine-stranded tinned wiring, ideally marine grade UL 1426 rated (BC-5W2 usually 105°C)

No movement at terminations obviously, just leave slack in the length portion.


by john61ct
Apr 07 2021 5:46pm
Forum: EBike Technical
Topic: Balance Discharger... or is there anything else?
Replies: 40
Views: 1084

Re: Balance Discharger... or is there anything else?

There is a huge difference between "rough" discharging packs for storage and needing precise CC regulation for accurate capacity testing of individual cells. The purpose of using chargers like FMA PL and 4010 is to get the latter control functionality. Apparently at that 2-4V discharge ran...
by john61ct
Apr 07 2021 5:36pm
Forum: Alternative Energy
Topic: Inverter recommendations? 48V sine wave, no grid tie
Replies: 27
Views: 3675

Re: Inverter recommendations? 48V sine wave, no grid tie

spinningmagnets wrote: generic sine wave 500W for $80
Wow lots of flexibility there!

Apparently can order 72V input and output 240V 50hz

EV packs for multiple uses, off grid living, get away from inefficient USA appliances.

A more stable imports source would be ideal, not sure if SPIPOWER is the canonical branding
by john61ct
Apr 06 2021 9:42am
Forum: Alternative Energy
Topic: Running a house on an e-motorcycle battery?
Replies: 63
Views: 1180

Re: Running a house on an e-motorcycle battery?

Yes as stated, the only grid connection being your bank charger, makes for a very simple, inexpensive and safe design. No aircon obviously. There is no need for any 3-way switch, just power off your mains charger and there is no input from the grid. The SC will always be active. ______ I also read t...
by john61ct
Apr 05 2021 7:35pm
Forum: Battery Technology
Topic: Where dispose of potted lifepo4 battery
Replies: 3
Views: 162

Re: Where dispose of potted lifepo4 battery

Some towns/counties have a few Hazmat disposal days per year where they accept most anything
by john61ct
Apr 05 2021 11:46am
Forum: EBike Technical
Topic: BMS destroyed my battery?!
Replies: 51
Views: 960

Re: BMS destroyed my battery?!

This looks like a good seller?
https://www.ebay.com/itm/313014455885