Search found 836 matches

by flippy
Nov 04 2018 4:45pm
Forum: Battery Technology
Topic: Samsung 25R Internal Resistance
Replies: 19
Views: 671

Re: Samsung 25R Internal Resistance

Nope, 100. Even fairly new cells were giving about 80-90 mOhms. They are typical Alibaba cells though. those are not real GA cells. Almost certainly rip-offs. Or at least the second-cut cells form the same factory. New out of the box they manage about 60 mOhms. i have about 400 on the shelf, known ...
by flippy
Nov 01 2018 11:21am
Forum: Battery Technology
Topic: Samsung 25R Internal Resistance
Replies: 19
Views: 671

Re: Samsung 25R Internal Resistance

jonescg wrote:
Oct 31 2018 8:29pm
Nope, 100. Even fairly new cells were giving about 80-90 mOhms. They are typical Alibaba cells though.
those are not real GA cells.
by flippy
Oct 15 2018 12:18am
Forum: Battery Technology
Topic: bluetooth BMS?
Replies: 862
Views: 51464

Re: bluetooth BMS?

i use it for a few days now, its a LOT better and fixes most texts.
by flippy
Oct 12 2018 12:00pm
Forum: Battery Technology
Topic: 18650pack cell protection idea. PTC + fuse & diode).
Replies: 5
Views: 502

Re: 18650pack cell protection idea. PTC + fuse & diode).

If you want to go that route then you need a regular fuse, never ever put passive or active parts between the bms and the cells. Please note that it is still academic, the risk of a cell popping does not cause a immediate problem, you just lose capacity and the bms will keep trying to balanc out the...
by flippy
Oct 12 2018 11:43am
Forum: Battery Technology
Topic: 18650pack cell protection idea. PTC + fuse & diode).
Replies: 5
Views: 502

Re: 18650pack cell protection idea. PTC + fuse & diode).

Please be more accurate, a PTC inside a cell is called Pressiure Temperature Current. A regular PTC in electrical terms a polymeric positive temperature coefficient, aka: a self resetting temp fuse. They both work as a fuse but one is permanent and the other is just a fancy resistor
by flippy
Oct 11 2018 11:30pm
Forum: Battery Technology
Topic: Help with building a low cost LiFePO4 trolling motor battery
Replies: 19
Views: 625

Re: Help with building a low cost LiFePO4 trolling motor battery

Those cells they tested are brand new. After 100 cycles you will see very different values. This is why i have a machine that can do lifetime cycles and plot the performance after a few months of daily use. flippy, You are incorrect. The cells tested in those videos I linked above are not brand new...
by flippy
Oct 11 2018 5:27am
Forum: Battery Technology
Topic: Help with building a low cost LiFePO4 trolling motor battery
Replies: 19
Views: 625

Re: Help with building a low cost LiFePO4 trolling motor battery

Those cells they tested are brand new. After 100 cycles you will see very different values.

This is why i have a machine that can do lifetime cycles and plot the performance after a few months of daily use.
by flippy
Oct 10 2018 6:05pm
Forum: Battery Technology
Topic: Help with building a low cost LiFePO4 trolling motor battery
Replies: 19
Views: 625

Re: Help with building a low cost LiFePO4 trolling motor battery

Sorry, confused. Do you mean the Headway's won't provide the 50A (needed for the trolling motor) or take 5A of discharge (for draining and bottom balancing/cycling the batteries? headway grossly overstate their ratings. i got brand new ones "back in the day" and they were seriously lacking. at high...
by flippy
Oct 10 2018 2:43pm
Forum: Battery Technology
Topic: Help with building a low cost LiFePO4 trolling motor battery
Replies: 19
Views: 625

Re: Help with building a low cost LiFePO4 trolling motor battery

those headways will never supply that current without killing them.
by flippy
Oct 09 2018 1:18pm
Forum: Battery Technology
Topic: 200Ah 12V battery bank (18650)
Replies: 12
Views: 542

Re: 200Ah 12V battery bank (18650)

Tomasenskede wrote:
Oct 09 2018 3:26am
DC DC seams not to be an option...
then you need to accept a 60% loss (or more) in capacity in the battery you build.
by flippy
Oct 08 2018 6:39am
Forum: Battery Technology
Topic: 80A BMS for 75 A battery
Replies: 8
Views: 279

Re: 80A BMS for 75 A battery

the bms needs to be rated for the limits of the battery, not it's application.
by flippy
Oct 08 2018 5:49am
Forum: Battery Technology
Topic: 25R low lifespan?
Replies: 19
Views: 715

Re: 25R low lifespan?

there is no high capacity cell that cen deal with these loads for any lifespan at those current levels. headways will also die under those loads. you need a bigger battery. more cells in P and crank the voltage (more S) if possible. but you need physcially more cells to spread the load. preferaby un...
by flippy
Oct 08 2018 2:48am
Forum: Battery Technology
Topic: 200Ah 12V battery bank (18650)
Replies: 12
Views: 542

Re: 200Ah 12V battery bank (18650)

it would be impossibe to charge 16v and you would lose most of the effective capacity is above 14.4V wich just happen to be the voltage where a alternator peaks. you you would only get 40Ah from a 100Ah battery... good luck finding a voltage controller for that alternator that does 16v. unles you wa...
by flippy
Oct 07 2018 5:01pm
Forum: Battery Technology
Topic: 200Ah 12V battery bank (18650)
Replies: 12
Views: 542

Re: 200Ah 12V battery bank (18650)

https://www.ev-power.eu/Winston-40Ah-200Ah/WB-LYP400AHA-LiFeYPO4-3-2V-400Ah.html?force_sid=5hsl9p12j2k5nmi7jl7uicr4q6 four of those and then a couple of balance boards to keep them equal, no bms needed. that cell (a pack of 4) will destroy that lead acid in performance in every metric (or imperial :...
by flippy
Oct 07 2018 2:24pm
Forum: Battery Technology
Topic: 120A+ BMS
Replies: 13
Views: 410

Re: 120A+ BMS

by flippy
Oct 04 2018 9:31am
Forum: Battery Technology
Topic: PSA: dont underspec your strips
Replies: 26
Views: 1499

Re: PSA: dont underspec your strips

With all due respect. I think these consideration are not really relevant. I used Sn60Pb40 solder, which has a melting point of 188°C (370°F). There is absolutely no way I will ever bring these cells higher than 50°C during their cycle life, even if I pull very hard on them. If you think about it o...
by flippy
Oct 03 2018 10:11am
Forum: Battery Technology
Topic: PSA: dont underspec your strips
Replies: 26
Views: 1499

Re: PSA: dont underspec your strips

A relatively large, soft, semi-liquid contact might actually carry a greater current than those tiny poorly bonded welded contacts depicted in the photos of the OP. As I noted previously, the technology available today in regards to soldering, is MUCH improved over my lifetime. While coppers have a...
by flippy
Oct 02 2018 7:32am
Forum: Battery Technology
Topic: PSA: dont underspec your strips
Replies: 26
Views: 1499

Re: PSA: dont underspec your strips

Low melting point solder, dudes. Sometimes I use pure indium, MP about 300F. Its electrical and thermal conductivities are much better than lead-tin solder. Sometimes I use indium-bismuth alloy, MP about 165F. Both are expensive, but a little goes a long way. So if i were to pull some serious amps ...
by flippy
Oct 01 2018 4:49pm
Forum: Battery Technology
Topic: PSA: dont underspec your strips
Replies: 26
Views: 1499

Re: PSA: dont underspec your strips

The reason I am frequently posting about spot-welding techniques is because I realize a lot of home garage pack builders are going to spot-weld, and I hope to help their results be "less bad". Harm reduction is a great thing. It's kind of a shame people have had so many problems with 18650 packs ca...
by flippy
Sep 30 2018 5:53pm
Forum: Battery Technology
Topic: bluetooth BMS?
Replies: 862
Views: 51464

Re: bluetooth BMS?

always measure from B-. C- is controlled my the board. when a failt happens it only allows the precharge circuit to pass power. if the led is lit on the board the it means it is trying to discharge the cell due to overcharging. measure from the first black wire and make sure to measure 3.8v on each ...
by flippy
Sep 30 2018 4:25pm
Forum: Battery Technology
Topic: PSA: dont underspec your strips
Replies: 26
Views: 1499

Re: PSA: dont underspec your strips

liveforphysics wrote:
Sep 30 2018 3:13pm
Nope, still need strain prevention somehow, deeper welds just tear the nugget right out of the can, if they don't already cause pinhole failures just from welding.
what stress is a nickel strip under when proper cell holders are used?
by flippy
Sep 29 2018 6:00pm
Forum: Battery Technology
Topic: Anyone else have a 14s4p 30Q pack?
Replies: 3
Views: 367

Re: Anyone else have a 14s4p 30Q pack?

that is a pretty heavy load to be putting on 30Q's. if its only peaks once every few minutes for a few seconds then fine but if you are constantly pulling into the 1000W range then i would get a much bigger pack, those cells will not survive that abuse long.
by flippy
Sep 29 2018 5:18pm
Forum: Battery Technology
Topic: PSA: dont underspec your strips
Replies: 26
Views: 1499

Re: PSA: dont underspec your strips

the slit helps if you have a cheap low power welder. if you have something more meaty then you can just compensate with more joules/amps. i did some delicate questions and it seems that the guy has a sukko 7xx welder. too bad he does not know how to use it and/or has worn out electrodes. that welder...
by flippy
Sep 29 2018 11:04am
Forum: E-Scooter and Motorcycle General Discussion
Topic: China’s largest electric scooter maker
Replies: 10
Views: 628

Re: China’s largest electric scooter maker

to each their own, i dont like physical effort, done plenty of that during my service to last me a lifetime. and if i want warmth i turn on my heated gloves. :mrgreen: you can get a govecs with 96v lead or 72v lithium. 40Ah 72v being the biggest from factory. i can upgrade them up to 80Ah if i reall...
by flippy
Sep 29 2018 5:44am
Forum: Battery Technology
Topic: PSA: dont underspec your strips
Replies: 26
Views: 1499

PSA: dont underspec your strips

....because of you do you will end up with something like this: https://i.imgur.com/njjl5h2l.jpg melty.... the customer came to me because often he would smell something "funky" after pulling full amps. this is from a pack that was built by "a friend" for him. he used the cheap 0.15 nickel plated st...