LiFePO4 purchase advice needed

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LiFePO4 purchase advice needed

Postby LROBBINS » 24 Jan 2021, 16:44

Now that Expresso reports that he expects the PL8 he ordered will actually soon arrive, given that no one has been able to identify a usable balance-at-end-of-charge board, and given that I'm now confident enough that the new chair I've built is working well, it's time for me to replace the very old Odyssey batteries I've been using for testing with lithium

There have been so many messages about different cells from various suppliers that I am (partially) at a loss to decide what to order and even more at a loss from whom to order them. I need to know what cells will fit in the space available and who are reliable suppliers of guaranteed-new CLASS A cells.

The space available is roomy for the Odyssey P1500s, so I should be able to fit lots of AHr (especially given Rachi's light weight and light use profile). That free space measures 200 mm wide X 660 mm long X 225 mm high and has to fit the cells, insulation studs and connecting wires. I prefer cells that are tapped for 6mm studs and not 4mm, but, of course, could re-drill and tap if necessary - perhaps even putting in 6mm helicoils right from the start. I would also prefer to not have the cells completely fill the box so that, should one ever become available, I would have room for an on-board balance board.

Can anyone point me toward cells from a known-to-be-reliable supplier?
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Re: LiFePO4 purchase advice needed

Postby Burgerman » 24 Jan 2021, 17:17

I am not sure I could. However I think expresso was referring to his cells arriving soon for yet another pack rather than the PL8. So maybe wait a while for him to reply!
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Re: LiFePO4 purchase advice needed

Postby Rye » 26 Jan 2021, 00:36

A lot of people buy from these guys https://blslifepo4battery.com/collectio ... o4-battery

This guy is always testing different company's Lifepo4 batteries and actually links to the BLS cells on aliexpress.
https://www.mobile-solarpower.com/raw-l ... -page.html

Here's their aliexpress A cells:
https://www.aliexpress.com/item/3304892 ... d59e09e9b9

They have a good reputation as far as I can tell. I think they also sell B grade cells.
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Re: LiFePO4 purchase advice needed

Postby LROBBINS » 26 Jan 2021, 09:48

Thanks Rye. BLS is on my list to consider.
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Re: LiFePO4 purchase advice needed

Postby rickystyx » 26 Jan 2021, 14:08

I've had two lots from BLS and both have been fine but I went direct to their store which may appear a little more expensive but didn't have the PayPal charge, however I have not ordered anything since Brexit so I don't know if the imports from their EU warehouse may have additional charges but that would be the same from anywhere these days and worth checking on
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Re: LiFePO4 purchase advice needed

Postby LROBBINS » 26 Jan 2021, 15:50

Ordering from the BLS EU (or US) warehouse adds about $20/cell, and cuts shipping time from several weeks to several days. Prices from the BLS store on AliExpress are somewhat lower than from their "home" pages.
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Re: LiFePO4 purchase advice needed

Postby expresso » 27 Jan 2021, 06:23

Out of all the Cells i purchased from - the place i got them from now - so far for me has been the best in terms of fair price - communication has been good - i would buy from them again if i need more - now its very hard to tell what is a Grade A brand new cell - i cant help there-

i asked a dozen time - i want brand new cells - i was told yes they are brand new - etc, - they look it - but how can i know for real - i cant -

so far i got the 100ah Cells from this seller - 16 of them - its in another friends chair now - - and i got the 200ah i just received - same seller -

i am testing for Cap. will take time - - those BLS looks nice also - first off - figure out the size you need - if its not alot more to pay for shipping - i would take the faster shipping option - took me 2 months to get mines - and PL8 i was told Feb- which is next week - not sure i believe it - we see

least expenisve are Varicore Cells - search on aliexpress - i was told they are brand new also - i cant say for certain what seller or brand is actually brand new Grade A - its a gamble - even with a good seller sometimes - i was impressed with the packing this time around - very important - you dont want to deal with damaged goods after - i wish i could help more -

https://www.aliexpress.com/item/1005001 ... web201603_

cheapest price - but know nothing about them - email seller ask -


https://www.alibaba.com/product-detail/ ... 388alZ01r0

i got those - now i see a 210ah version - i hope i get at least 190ah when done testing for Cap.
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Re: LiFePO4 purchase advice needed

Postby Burgerman » 27 Jan 2021, 12:31

Search for grade A cells. You should get AT LEAST the rated capacity tested properly.
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Re: LiFePO4 purchase advice needed

Postby expresso » 27 Jan 2021, 17:17

thats another thing with how we test them compared to how they are tested in china - unless you test them under the same conditions the results will be different -

i am testing them now - but i need to make a cable first to use the dumb load to discharge them - PL8 would take 3 days to do one 200ah Cell

i will connect dumb load and PL8 to monitor - should take 5 hours this way - once i make the cable first -

in the end - for me - if i can get at least 190ah out of mines - i be more than happy - close enough - and that difference could be the way its tested - i hope i get at least 190ah - we see -
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Re: LiFePO4 purchase advice needed

Postby Burgerman » 27 Jan 2021, 17:49

To measure full capacity, accurately you need a 25C room. A single fully charged cell to 3.650V and held there for 15 mins
Then set it to discharge without dump load, use internal. Set to discharge to 2.5V. Set discharge to 10A. Wait. When it ends record the capacity removed. It should be 200Ah or greater.
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Re: LiFePO4 purchase advice needed

Postby expresso » 27 Jan 2021, 21:23

well it looks like i am going down that road after all - i planned to use the dumb load - i made cable to connect both PL8 and dumb load - turns out - it didnt work - i checked the cables on the dumb load and they were bad - wire was brown black - so i figured ok - i had a wire made with the connector i needed on one end already

so i cut off the other end and connected that to the dumb load - nothing - then i tried the other side of the dumb load - connected it there and nothing - so i gave up - the Cell is discharging on the PL8 only - 10A a hour - will be done by tomorrow night 7 pm - not sure i want to do it this way to the rest of the cells -

i did charge to 3.6v though on this one - it put back 134ah - meaning it should have had about 70ah still when i got this one - - i didnt know the dumb load could go bad this way - it worked last time i tried it a year ago and just sat till today - it has two coils and connection on each end - i tried both ends to connect the cable and nothing -

do those Coils go bad ? or is it the ends where they are connected to which can be bad ? either way - i guess i need a new one ? any ideas for a low cost one i can use ? or just finish this one cell and dont do the rest - or use PL 8 for everything - may wear that out going 24/7 for a few weeks ?

what do you suggest ?
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Re: LiFePO4 purchase advice needed

Postby Burgerman » 27 Jan 2021, 21:59

I suggest you connected it wrong. They can burn out but then you would see, black, loose! Like a blown fuse. You can see where to connect by looking at the coils, It goes in one end and along both coils, and out.

How were you going to use a dump load (its not dumb!) to measure power taken out?
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Re: LiFePO4 purchase advice needed

Postby expresso » 27 Jan 2021, 22:07

its labeled pos and neg where i connect it - - cant make a mistake there - now on the other end - its not labeled - i followed the same pos and neg as the other side with the label - or did i do that wrong and had to swap neg and pos when useing the other end ?

the coils seem dark - later i will take picture and post maybe you can see something i am not


i made a cable to connect to both the dumb load and PL 8 - i use the Pl8 and discharge also so it stops at 2.9v - the dumb load is also connected - i stop that with the breaker inline when its near the end and let the pl8 finish it - just to get it done faster - but your right i dont think i would see Cap out - only what the Pl8 does ?

in that case if using a dumb load - you have to go with how much you put back in on the full recharge once you discharged it all the way - then recharge and look at Cap in - to get an idea
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Re: LiFePO4 purchase advice needed

Postby Burgerman » 27 Jan 2021, 22:27

Its not a DUMB load! Its a DUMP load... And it will only draw high current at 24V not with 1 cell...

Connect to the plus/minus. JOIN THE OTHER END TOGETHER!

Also, how do you intend to measure Ah out with the DUMP load? You cant. Well I can but its complicated. So use the PL8 and set it to discharge at 10A and just leave it. It will automatically stop at the voltage you tell it.
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Re: LiFePO4 purchase advice needed

Postby expresso » 27 Jan 2021, 22:54

AHHH i see - your right - it was a 24V dump load - i though anything i connect to it will just start -

i used it before with a full pack - 24V - and it worked - so it may still work if connected to a 24V pack then ?

its on the PL8 now - i guess i will just use the PL8 for each one if i want to know - going to take a few weeks - if the PL8 dosnt wear out - it shouldnt be working hard with just discharging ?
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Re: LiFePO4 purchase advice needed

Postby expresso » 27 Jan 2021, 22:56

if i connect as i always had - then connect the other side together - one wire connected -

what would that do ? it would work for one cell ? not going to affect the battery in any way Neg. ?

i was wrong - it cant be measured out with the dump load - it was just to get it done in 5 hours instead of 15 - i would stop the dump load before it reaches 2.9V - i would see it on the computer since i have the PL8 going at the same time - i can see what the PL8 pulls out only - when near the end - i let the PL8 finish it so it stops on its own - that was the plan

i will check the dump load on the next cell - connect it as you suggest - one end together and the other end pos and neg. - that would work ?
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Re: LiFePO4 purchase advice needed

Postby LROBBINS » 27 Jan 2021, 23:03

In ham radio circles it's known as a "dummy" load. If its resistance gives a draw of say 40A at 24V, at 3.6 V it will draw only 6 amps. You're better off with the PL8 in any case for a single cell.
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Re: LiFePO4 purchase advice needed

Postby expresso » 27 Jan 2021, 23:29

now thats good to know - thanks for that info. i wont be spending any more time playing with it till i build the whole pack and do it with the full 24V pack

i went crazy half the day thinking what was wrong - the wires were bad anyway - i cut a cable i made years ago for some reason i dont recall now - to use it on it - which i will anyway - i also made the cable from the battery end to two other ends to connect both - thinking i was going to know the Cap out - i wasnt now that BM mentioned it -

so overall - i learned something at least - no time wasted with the cell - it was already started on the PL8 while i kept trying to get the dump load going - i am glad its most likely not broke - - now i cant recall how i did it the other times with single cells - i guess i used the PL8 - there were 100ah cells

with 200ah - takes double the time - alot longer - this will go till tomorrow night at 7pm - should stop - its been going since 2pm i believe
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Re: LiFePO4 purchase advice needed

Postby Burgerman » 27 Jan 2021, 23:47

A dummy load refers to an antenna load. So the transmitter has an SWR thats super low and comes to no harm. Its a dummy antenna load.

The dump load is where you dump a load of energy! Usually sold for wind tubines so the can waste energy by dumping it, if the batts are already charged and they are making too much power. Releasing the windmill/generator electrically instead causes it to unload, overspeed and damage.

But yes, PL8! Then we will know how much Ah.
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Re: LiFePO4 purchase advice needed

Postby expresso » 28 Jan 2021, 00:25

glad i got that resolved - hope it still works on 24V when pack is done
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Re: LiFePO4 purchase advice needed

Postby LROBBINS » 28 Jan 2021, 09:27

Laws passed by a parliament are often ignored, you can't do that with Ohm's law.
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Re: LiFePO4 purchase advice needed

Postby expresso » 30 Jan 2021, 06:16

from this pic you can see i have no room in the battery tray one way - and have extra space on the side

i cant use anything in between the cells the long way - my question is - if i leave them alone - using them as they arrive - blue wrap which is fine - no rips or anything exposed -

if i build the pack with both ends touching each other - in this pic its the Neg. posts - side to side - would this be ok - this way - since i cant add anything in between -

or if they somehow touch exposed - would that be a problem or not being they are both Neg. touching Neg. ?

its very tight and i barely can fit them this way - only way they can fit - i may use a very thin tape i have its Green - forgot what its called but its to protect - fire etc, - even that may be too much -

would this be safe if i didnt add anything ?
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Re: LiFePO4 purchase advice needed

Postby Burgerman » 30 Jan 2021, 11:24

Use the tape! If the outside edges touch the battery space (metal?) or the cells touch each other, smoke! Lots of smoke... Or slot a thin plastic card/sheet between, and under them. You dont want anything to ever touch. Even a layer of grey duct tape.

Do they fit easier if turned 90 degrees?
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Re: LiFePO4 purchase advice needed

Postby expresso » 30 Jan 2021, 14:37

i havnt tried in different angles - i can try another way - maybe fit 6 going down and two on the side - - same issue - those two would be touching but only those two - if i start changing the layout - which may work better - i dont want to confuse myself when i wire it up :D

i will tape the bottom since they are bare - and the sides that touch now - i just cant over do it - even 1mm - i dont have room to spare

the width - enough room i like to make them fit this time without having to cut the battery tray -

they are wrapped nice - which is good - at least i may be able to just use the thin Green Tape in between -
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Re: LiFePO4 purchase advice needed

Postby expresso » 30 Jan 2021, 17:32

i think its better arranged this way -

Question for everyone who purchased Cells already -

How Many users purchased Cells - Grade A Brand New - tested them for Cap ?

Any Cells and tested for Cap ? Did they match or come close to the rated Cap ?

if so - would you mind posting the links to where you got them from ?

this would help other users who are looking -
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Re: LiFePO4 purchase advice needed

Postby LROBBINS » 30 Jan 2021, 20:28

Expresso,
You REALLY do have to insulate the cells, even if you have to modify the battery box to do it. Although each shell is connected to the + terminal of that cell, remember that the + terminal of one cell will be connected to the - of an adjacent cell when you wire them in series. Even slight cell-to-cell imbalance can leave one cell more positive or less positive than its neighbor and with the extremely low internal resistance of LiFePO4 cells that can make for a large current flow if they make contact (Ohm's law strikes again) and that large current can make large smoke.

I have a question about the cells you just got. Are they drilled for 4mm or 6mm studs?
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Re: LiFePO4 purchase advice needed

Postby expresso » 30 Jan 2021, 20:34

i will add a thin sheet of silicone as i did on all the packs i made - the only spot where its going to be tight now is the 2 cells sideways - its a tight fit - i will use the green tape i used before - its thin and very good -

yes they are M6 - i asked them a dozen times to be sure also -
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Re: LiFePO4 purchase advice needed

Postby expresso » 30 Jan 2021, 20:38

each cell gets a sheet of silicone between them - the two sideways - i have to use the green tape thin to make it work - i will try the silicone first but i already tested them in the box - tight fit - i want to avoid cutting the box this time

i did that on my other one - not a big deal - i cut one side on one end - the Cells just needed a few mm more room - there were not these cells - and a bit longer i think -
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Re: LiFePO4 purchase advice needed

Postby Burgerman » 30 Jan 2021, 20:50

Expresso,
You REALLY do have to insulate the cells, even if you have to modify the battery box to do it. Although each shell is connected to the + terminal of that cell, remember that the + terminal of one cell will be connected to the - of an adjacent cell when you wire them in series. Even slight cell-to-cell imbalance can leave one cell more positive or less positive than its neighbor and with the extremely low internal resistance of LiFePO4 cells that can make for a large current flow if they make contact (Ohm's law strikes again) and that large current can make large smoke.

I have a question about the cells you just got. Are they drilled for 4mm or 6mm studs?


He doesent read! We have to go about 20 posts before we repeat everything all over again! Actually every cell of his 8 are capable of thousands of amps, and all are 3.4V different to each other. So its not a case of balance but a full on cell short!
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Re: LiFePO4 purchase advice needed

Postby Burgerman » 30 Jan 2021, 20:55

The 1st cell tested was charged to 3.65V and discharged to 2.50V and did 189Ah. Clue 1. The white plastic surrounds on the terminals are not all the same colour at least one has gone brown through aging or heat. Clue 2.

These cells are used. They are cheap, and display almost the capacity that they should have. So considering the fact that they are the same price as a set of 40Ah capable MK lead bricks, not too bad. But A grade cells they are not. They appear used and recovered in plastic. But very cheap.
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