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by spinningmagnets
Feb 18, 2018 9:42 pm
Forum: Alternative Energy
Topic: 4S LiFePO4 as a 12V system
Replies: 14
Views: 322

Re: 4S LiFePO4 as a 12V system

Thanks for posting EbikeAus. Lately I have been thinking about putting together a hybrid system. Originally, I thought I would get four 20-Ah high-current flat foil packs from EIG ($220). Now I am leaning towards four large LiFePO4 15-Ah cylindrical cells, and a capacitor bank to help with burst amp...
by spinningmagnets
Feb 17, 2018 12:13 pm
Forum: Battery Technology
Topic: 18650 questions - How does internal resistance relate to voltage?
Replies: 11
Views: 136

Re: 18650 questions - How does internal resistance relate to voltage?

The lower the internal resistance, the more amps you can pull from the cell without it overheating.

If you draw more amps than a cell can provide, there will be a voltage drop (sag), and heat.
by spinningmagnets
Feb 16, 2018 2:37 pm
Forum: Battery Technology
Topic: Would you charge a 4s LiFePo with a "15V" wall wart (intended for charging a 12V SLA)?
Replies: 11
Views: 171

Re: Would you charge a 4s LiFePo with a "15V" wall wart (intended for charging a 12V SLA)?

I wouldn't charge LiFePO4 up to 4.2V per cell, but...I have read that doing so will not cause the electrolyte to off-gas. This is touted as one of the reasons LiFePO4 is considered to be very safe, and less likely to catch fire. I have recently become interested in 4S LiFePO4 as a 12V SLA replacemen...
by spinningmagnets
Feb 16, 2018 11:58 am
Forum: E-Vehicles General Discussion
Topic: Lithium batteries for Submarines
Replies: 17
Views: 295

Re: Lithium batteries for Submarines

When my submarine pulled into Australia (Perth, a lovely city with fun people), there were protesters at the Navy base gate with anti-nuke signs. We braced ourselves for trouble and planned to take quite a bit of abuse when passing through the gate (without causing an international incident). The pr...
by spinningmagnets
Feb 15, 2018 9:12 pm
Forum: E-Vehicles General Discussion
Topic: Lithium batteries for Submarines
Replies: 17
Views: 295

Re: Lithium batteries for Submarines

I've wondered this for years, and someone finally clued me in to the fact that nuke missiles have to have their warheads refreshed every so often, and light water uranium reactors can produce fresh plutonium as a byproduct. I don't know how much of an influence this on policy decisions, but..I'd lik...
by spinningmagnets
Feb 14, 2018 4:08 pm
Forum: Battery Technology
Topic: Common pack design mistakes, how to avoid?
Replies: 236
Views: 18554

Re: Common pack design mistakes, how to avoid?

The main reason the Powerwall guys use individual fuses on the cells (even though it's a fixed non-mobile installation) is because it's popular to build with used cells that are typically $1 each. Sometimes they overheat under normal use...
by spinningmagnets
Feb 14, 2018 8:24 am
Forum: Battery Technology
Topic: Common pack design mistakes, how to avoid?
Replies: 236
Views: 18554

Re: Common pack design mistakes, how to avoid?

I'm not a fan of soldering onto cell ends, especially the negative electrode, but I have to say I would definitely not use the technique shown. He says to get a good soldering iron, and then he shows a 40W unit with a fairly small tip. Then he holds the hot tip onto the negative electrode as an exam...
by spinningmagnets
Feb 13, 2018 9:16 pm
Forum: E-Vehicles General Discussion
Topic: Lithium batteries for Submarines
Replies: 17
Views: 295

Re: Lithium batteries for Submarines

I was on a 637 class that was built in 1969. Don't be too impressed that I was on a nuke, I was the gear head that ran the diesel.

In spite of Chernobyl, Fukushima, and 3-mile island, Navy nukes have had a very good safety record.
by spinningmagnets
Feb 13, 2018 9:09 pm
Forum: E-Bike Technical
Topic: Melting wires
Replies: 44
Views: 726

Re: Melting wires

I've read that crimps can withstand a level of heat that would re-melt a soldered connection. However, my personal opinion is that no joint should ever get so hot that any solder that is present would be damaged. I'm not sure on the specifics but...it's also bad to get copper extra hot (hardening? B...
by spinningmagnets
Feb 13, 2018 5:59 pm
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 292
Views: 24921

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

Those electrodes look good!
by spinningmagnets
Feb 13, 2018 5:31 pm
Forum: E-Vehicles General Discussion
Topic: Lithium batteries for Submarines
Replies: 17
Views: 295

Re: Lithium batteries for Submarines

I can't speak for the current theories of best design trends, but...the battery compartment wouldn't have much airspace to flood, and the sub I was on maintained several large tanks with fresh water in them. Of course, any build-up of pressure would be vented to the outside...And also, I would have ...
by spinningmagnets
Feb 13, 2018 10:00 am
Forum: E-Vehicles General Discussion
Topic: Lithium batteries for Submarines
Replies: 17
Views: 295

Re: Lithium batteries for Submarines

Speak of the devil...I was a mechanic on a nuclear-powered submarine for a handful of years, back in 1977-81. We had a back-up diesel generator and a huge lead-acid battery, in case there was ever a problem with the reactor. I was told that if the torpedo room ever flooded with salt-water (just abov...
by spinningmagnets
Feb 13, 2018 9:24 am
Forum: Battery Technology
Topic: Common pack design mistakes, how to avoid?
Replies: 236
Views: 18554

Re: Common pack design mistakes, how to avoid?

The spray insulation "might" be OK on the negative ends of the cells (fast, cheap, convenient), but...I'd keep the vents open on the positive end.
by spinningmagnets
Feb 13, 2018 12:44 am
Forum: Alternative Energy
Topic: 4S LiFePO4 as a 12V system
Replies: 14
Views: 322

Re: 4S LiFePO4 as a 12V system

Alan, if you were buying Headway cells today, would you have one or two retailer recommendations?
by spinningmagnets
Feb 12, 2018 8:46 pm
Forum: General Discussion
Topic: Credit Card Problems?
Replies: 10
Views: 176

Re: Credit Card Problems?

I highly value having a credit card (I have two), and I hate them both. Me and credit card banks are like porcupines mating, and I am the female. I occasionally have the need to be used in order to get something I want. For instance, when I was younger...I left a deposit-check with a car rental agen...
by spinningmagnets
Feb 11, 2018 8:06 am
Forum: Alternative Energy
Topic: 4S LiFePO4 as a 12V system
Replies: 14
Views: 322

Re: 4S LiFePO4 as a 12V system

Thank you e-beach. That is a very good and useful link. On a side note, Harbor Freight Tools / HFT (yes...I know)...they have water-resistant Pelican case clones now under the Apache brand name. I hate when China clones something, but...Pelican cases are already made in China so...whatever. Apache b...
by spinningmagnets
Feb 10, 2018 1:23 pm
Forum: Alternative Energy
Topic: 4S LiFePO4 as a 12V system
Replies: 14
Views: 322

Re: 4S LiFePO4 as a 12V system

Thanks! There are several amp-output versions of the Headway cells ("HP" version shown above, 20C, 8Ah, 160A), the continuous 80A test for five minutes was the highest amp version. He dead-shorted the weakest cell at the end and got over 300A for a few seconds. The factory advertising claimed 160A c...
by spinningmagnets
Feb 10, 2018 11:26 am
Forum: Alternative Energy
Topic: 4S LiFePO4 as a 12V system
Replies: 14
Views: 322

Re: 4S LiFePO4 as a 12V system

Awesome info, thanks! Charging and LVC methods I have a 100W 14V solar panel for emergencies, and 12V car battery chargers / alternators often actually put out a variable voltage around 14V. The 4S LiFePO4 at a fully-charged 3.65V would be 14.6V. LVC If I drain to only 3.0V per cell for long life (a...
by spinningmagnets
Feb 10, 2018 9:31 am
Forum: Alternative Energy
Topic: 4S LiFePO4 as a 12V system
Replies: 14
Views: 322

Re: 4S LiFePO4 as a 12V system

reserved for additional info
by spinningmagnets
Feb 10, 2018 9:31 am
Forum: Alternative Energy
Topic: 4S LiFePO4 as a 12V system
Replies: 14
Views: 322

Re: 4S LiFePO4 as a 12V system

Youtubes "DIY Portable LiFePO4 Power for Ham Radio" (Headway cells in 4S) https://www.youtube.com/watch?v=SJGKuriGRok 2.0V-3.65V max range SOC (it appears there is no usable range under 2.8V per cell) https://endless-sphere.com/forums/viewtopic.php?f=14&t=86698&start=25#p1298285 Starting a V6 car wi...
by spinningmagnets
Feb 10, 2018 9:31 am
Forum: Alternative Energy
Topic: 4S LiFePO4 as a 12V system
Replies: 14
Views: 322

4S LiFePO4 as a 12V system

I'm just starting this thread as a place to park useful info about 4S LiFePO4 as a 12V battery pack. Depending on the components the pack is powering, the charging system desired, and the LVC needed...using 18650 Li-NCA or Li-NCM can be too low at 3S or too high at 4S, however LiFePO4 has a lower no...
by spinningmagnets
Feb 09, 2018 10:46 pm
Forum: Battery Technology
Topic: DIY battery pack cooling
Replies: 14
Views: 240

Re: DIY battery pack cooling

The larger the pack, the less of a difference there is in the battery-cell-per-volume between the common "rank and file arrangement, and a honeycomb layout. I prefer honeycomb because the is less air restriction and more air-flow allowed if they are packed-in to the same cell density as a common squ...
by spinningmagnets
Feb 09, 2018 1:14 pm
Forum: Motor Technology
Topic: Halbach array Inrunner or Outrunner
Replies: 13
Views: 229

Re: Halbach array Inrunner or Outrunner

There is no single way to wind a motor that is "best". There are many variations. I don't mean to say that I know them, or that I understand each versions benefits and drawbacks, but...I know enough that I would only copy an existing successful design that matched the size and job that I wanted to m...