PINNED - Lithium battery conversion/info

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Re: PINNED - Lithium battery conversion/info

Postby steves1977uk » 19 Sep 2021, 19:15

Went to check the volts on my Digimess PSU, turned it on, it made a crackling sound and it went off instantly. :thumbdown: Now it refuses to power back up. Both fuses (mains plug and internal one) tests fine. My Brother opened it up and nothing looks blown.

Bugger! :cussing

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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 19 Sep 2021, 19:24

I suspect that that was the problem. Your power supply wasnt doing what it said.
Because what you showed on that photo wasnt actually possible. The cells when connected to an ACTUAL 3.600V will likely charge at high amps quickly as they should.
Do you have a shirley one?

Incidentally I sent mine (digimess) back once after connecting a 24V wheelchair in reverse (smoke and noise!) and they charged a fixed amount to repair and return it. Dont remember where though. It was 17 years ago...

Also https://www.eevblog.com/forum/repair/am ... on-smps_s/
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Re: PINNED - Lithium battery conversion/info

Postby steves1977uk » 19 Sep 2021, 19:50

I have two Shirley PSUs and have one of the full case mod with SB50 and XT90 connectors on order! :thumbup:

I had this Digimess PSU repaired before when the PL8 killed it. Think I mentioned this before about 6 years ago.

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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 19 Sep 2021, 19:58

How can a PL8 kill it? Even a direct short cant do that. It just shuts off. I think thats not possible, but the other way around is. A bad or unstable or noisy supply can definitely kill a PL8.

Connect your cell to a shirly supply. Set Amps to 20 ot 30. Or whatever your cables can do. Set volts to 3.60V. And CHECK with your MM. It will likely charge at max amps for a while and then tail off slowly for 20 mins. Then its charged.
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Re: PINNED - Lithium battery conversion/info

Postby steves1977uk » 19 Sep 2021, 20:09

At that time I was charging my chair at 40A, Digimess PSU was set to 30v and as soon as the current climbed above 38A, BANG! It blew the 16A fuse, tried another, BANG again. So had to send it in for repair back then. So yes it's possible to kill them unfortunately. The PL8 still works fine to this day.

Will try charging the cell in the next few days. Thanks for your help and advice BM! cheers

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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 19 Sep 2021, 20:25

I wind mine to max 40A and 30V and charge odyssey all the time. I think yours must have some additional problem somewhere. But dont worry the shirley ones are if anything better, more compact, and instead of 30V are 60! And 50A too. And so far I have not blown one of those yet...
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Re: PINNED - Lithium battery conversion/info

Postby steves1977uk » 23 Sep 2021, 15:37

My Brother found one of the components have blown off one of the PCBs inside my Digimess PSU while he was cleaning it out, luckily the top has the writing on it to identify what it is.

Hopefully I can find a replacement and bring it back to life.

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Re: PINNED - Lithium battery conversion/info

Postby Arima » 23 Sep 2021, 16:54

40152 cells finally arrived. The orange connecting blocks do not slip nicely onto the cells. The only way I'll get these on is to use a clamp like a press. Is this normal or do i have the wrong blocks? They are not far off from being a good fit but I can easily see one of the blocks splitting.
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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 23 Sep 2021, 19:19

All the ones I ever bought were a tight hand push fit. Needed a ligh tap with a hammer when doing many at once.
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Re: PINNED - Lithium battery conversion/info

Postby Arima » 24 Sep 2021, 06:27

Even after putting a clamp on these would not go together. Didn't realize there are 38120mm cells also. Put the ruler on it and these assembly blocks are definitely 38mm. How it is I have so much bad luck. Hopefully evassemble will send a rush replacement.
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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 24 Sep 2021, 07:32

Why are you using headway cells today. Things moved on, and prismatics became more energy dense and are now available in sizes that alow us to get more Ah into the same volume and fit into the space lead came out. And cheaper too now.
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Re: PINNED - Lithium battery conversion/info

Postby Arima » 24 Sep 2021, 17:03

This will be an add-on pack. 40152 cells give me the size and weight I can handle. My brain won't commit to a full lead replacement until I live with these and experience the use pattern. I realize this is not the most efficient configuration but it will be a great experience for me.

Not fond of things hanging off the back of my chair so I'm considering a 2in aluminum box enclosure under the butt cushion.
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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 24 Sep 2021, 17:16

Headways are OK for that. Higher C rated.

Didn't realize there are 38120mm cells also

Ah. The clue is in the name. 38 x 120mm. So you have the 15Ah ones?
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Re: PINNED - Lithium battery conversion/info

Postby Arima » 24 Sep 2021, 19:57

Yes 15Ah. Hopefully I don't suffer the deep discharge dilemma.
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Re: PINNED - Lithium battery conversion/info

Postby steves1977uk » 25 Sep 2021, 11:32

I'm using 40 of those 40152 cells in a 8S5P configuration from nearly 7 years ago and they still beat a new pair of 73Ah MK Gel batteries in range. All chairs should be LiFePO4 in the 21st Century.

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Re: PINNED - Lithium battery conversion/info

Postby Arima » 26 Sep 2021, 19:45

That's encouraging Steve. If it doesn't work out on a chair maybe I can find some other use for it. For example my storage unit does not have lights that are under my control. They switch off after 10mins. Now if evassemble would just send the right parts!

IMG_20210926_111601188.jpg
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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 26 Sep 2021, 20:44

Buy metric allen screws. Stainless. Dont use the split shake proof washers only flat washers. Or there may be trouble ahead. Got the T shirt! And be sure to use some blue loctite only a tiny bit on the thread alone and get them tight on final assembly. Everyone misses one no matter how much they say they didnt...
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Re: PINNED - Lithium battery conversion/info

Postby fishinjunky » 05 Oct 2021, 01:37

Anyone having any luck finding a potential charger?
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Re: PINNED - Lithium battery conversion/info

Postby Arima » 05 Nov 2021, 18:53

Burgerman wrote:Buy metric allen screws. Stainless. Dont use the split shake proof washers only flat washers.


I think you are telling me the screws that came with the cells are to short? Been waiting weeks for the correct orange assembly blocks and bus bars. Figured I would measure the screw length after mocking up the pack with all the terminals connected. Seriously doubting if the correct parts are ever going to show up. So what is a replacement for bus bars...all I can think of is wire with terminal ends? When packing the cells is it okay to have them touching each other...or they need a millimeter between each? Still looking for a box (to hold the cells) that can be sat on.
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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 05 Nov 2021, 19:37

They should not touch. The can is connected to the negative. I am telling you to use allen bolts, the correct length with some blue loctite, and only use a FLAT washer. You could use terminals for every connection. And some cable. Very much work...
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Re: PINNED - Lithium battery conversion/info

Postby Arima » 05 Nov 2021, 20:15

Okay no touching! I can get bolts. Curious why the button head screw style is less desirable? Yes terminals would be a pain in the ass.
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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 05 Nov 2021, 20:20

They come loose as the battery flexes and bets banged around. And you cant get them reliably at the correct tightness. They are cheaply made. Allen bolts are better. They need
to be surgically clean connections and threads locked. Or you will get issues.
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Re: PINNED - Lithium battery conversion/info

Postby ICEUK » 16 Nov 2021, 13:38

Biggest problem with doing a lithium battery conversion is you forget when you last charged your pack, :dance :D
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Re: PINNED - Lithium battery conversion/info

Postby Arima » 21 Nov 2021, 02:17

ICEUK wrote:Biggest problem with doing a lithium battery conversion is you forget when you last charged your pack, :dance :D


Don't you use them?

Burgerman wrote:They come loose as the battery flexes and bets banged around. And you cant get them reliably at the correct tightness. They are cheaply made. Allen bolts are better. They need
to be surgically clean connections and threads locked. Or you will get issues.


The threads on my cells are filthy. I don't like the idea of running a tap in and out...the material feels soft. Can I use a brush like this...https://www.amazon.com/gp/product/B0719 ... LB5XE4F35P or would brass be better?

Bolts are on the way. They should be torqued to...26 inch lbs. and do not exceed 35 inch lbs?
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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 21 Nov 2021, 11:58

What type of cells?
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Re: PINNED - Lithium battery conversion/info

Postby Arima » 21 Nov 2021, 23:04

These are Headway 40152 cells.
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Re: PINNED - Lithium battery conversion/info

Postby Burgerman » 21 Nov 2021, 23:31

Are those supposed to be new? Never saw a thread like that in a headway. Maybe a clone or used or old. You can use a tap by hand if a screw wont screw in easily.
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Re: PINNED - Lithium battery conversion/info

Postby Arima » 23 Nov 2021, 01:52

Well I didn't specify "new" when I ordered them from EV Assemble. Shouldn't have to. Still have not received the orange assembly blocks and connector plates. On the bright side they did respond to email and promised to resend the correct parts. This is normal for everything I touch.
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Re: PINNED - Lithium battery conversion/info

Postby ex-Gooserider » 23 Nov 2021, 02:21

Minor caution on taps - the most common style has a good bit of taper on the tip, which is intended to gradually start cutting the threads into a non-threaded hole. If you use them on a blind hole the tap will bottom out before you have cleaned up more than the first few threads. DON'T try to force the tap in as there is an over pressure vent valve on the bottom of the hole on one end (I forget which one) and you don't want to damage it... By the same idea, be careful about screw lengths.

What you need is a 'bottoming' tap, sometimes also called a 'plug' tap that has no tapered section and instead has full threads over it's entire length...

However a much simpler thing that I find works well for cleaning up threads and is arguably safer for soft materials is to get a plain bolt the right size and grind or file a lengthwise groove in it to make an imitation tap...

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Re: PINNED - Lithium battery conversion/info

Postby Arima » 24 Nov 2021, 20:19

I think this is the first time I've seen mention of a valve. One end of the cell looks like it has vent holes...so that might be the one. 10mm bolts look like they should be fine. Great idea about making a tap! Put a little oil on it and worked a bolt in going back and forth without any trouble. Dirty connections cause more resistance correct?
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