PINNED - Lithium battery conversion/info

[woodygb]

You might want to consider an electrical jointing compound ...
https://www.ebay.co.uk/itm/Unial-Univer ... ctupt=true

[Scooterman]

Even if the copper nut and washers on the top oxidises, it's still a good contact between aluminium terminal surface and the underside of tinned lugs.

[Burgerman]

Nope. The actual contact surface between the alloy terminal and the copper stud is tiny. It touches in only a few places tight enough to keep oxygen out. And because they are disimilar metals you get other reactions with moisture in the air... And high resistance.

Copper and aluminium bad idea. The fact that they are dissimilar metals creates a battery. A very good one. That creates corrosion on all the points that were initially in contact. And then generates a few mV all of its own.. Your balance may only be a few mV out. And the charger tries to fix it. Copper/aluminium will give around 0.78V 780mV! And makes an excellent battery... I keep advisng people to run away from bare copper but they do not listen! Shirley recently tried it and had big problems.

The photo below shows a battery made by placing a strip of copper and a strip of aluminum into a glass of Coca-Cola (I used the sugar-free cherry flavored variety because that's what I found in the refrigerator).

https://sci-toys.com/scitoys/scitoys/ec ... m_coke.jpg

[Burgerman]

Aluminium is also a stupid material to make a battery terminal from, because it reacts with many metals. Inc Zinc plating. But unlike copper the zinc plated or stainless bolts dont oxidize so badly or quickly. Its also a good reason to solder all the connectors. Once assembled, a quick squirt of WD40 (the ONLY thing its any good for) helps prevent it oxidizing.

[Scooterman]

Galvanic reaction occurs with steel and aluminium too. Plus I won't be pouring cola over my terminals

We'll just have to agree to disagree. I know bare copper isn't advisable but Shirley got it for me so I thought I might as well use it. But I'm more confident than you, and if it does create wiggly graphs I'll rip it out and change it...

PS: Thanks for the link woody

EDIT: I was typing you replied above

[Scooterman]

a quick squirt of WD40 (the ONLY thing its any good for) helps prevent it oxidizing.

Thank you for the tip

Also how about that stuff we used to spray on HT leads?

[Burgerman]

That is WD40 or a clone. If an HT lead is of decent quality, and clean, you can pressure wash your engine and it will start and run perfectly.

If you spray that crap (like WD40) onto your high tension leads, coil etc it may help it start by driving out water once. And garantees that a film of moisture absorbing dust then sticks to all of it. Meaning every time a cloud passes it now wont go. Only retards spray that junk on engines.

[Scooterman]

Egg in the radiator to stop a leak

[Burgerman]

Yes. It stops the leak. And BLOCKS everything else.

The way to stop a leak, is to FIX THE LEAK!

I may add that shirley tried USING bare copper after he shipped yours. And had to remove it when everything looked all crazy on screen. He replaced it with tinned connectors, and wires, and everything perfect again.

[ex-Gooserider]

How rapidly do those cell monitors respond? If they are pretty much instant, it is worth remembering Will's comments about watching the voltage drop as a 'state of charge' estimate...

He used a simple digital meter, which is gives a pretty instant response, and said that he has learned to judge the amount of power used by watching how much the voltage drops under load, and how fast it recovers.... The more discharged the pack is, the more of a drop you get when doing a given maneuver and the longer it takes to return to the 'resting' voltage...

(I see the same sort of thing with my pod 'charge' LED's on lead bricks....)

Also as a note about fire extinguishers - any standard extinguisher is NOT going to put out a lithium fire, there isn't much of anything that will! However an extinguisher WILL put out burning wire and other chair bits - at least as long as you don't still have short circuits re-heating things, or actual lithium burning that re-ignites the fire...

However an LiFePO4 battery will not normally get into a lithium fire - (it has been linked to in the past) there is a You-Tube video of a guy abusing a Headway cell by grossly overcharging it - The result was smoke and heat, and a liquid oozing out of the cell. He managed to light the liquid, but it was clearly an oil or alcohol type flame, not lithium, and was pretty easy to put out...

The reason is that the chemical reactions in an LiFePO4 cell never result in metallic lithium being present, just different lithium compounds that are each relatively stable and not violently reactive... OTOH LiPo and to a lesser degree LiCo and other Li-Ion chemistries do have stages with metallic (pure) lithium - which is one of the most violently reactive chemicals known - including to water vapor and oxygen.... Once one of those chemistries gets going, there is no really good way to put it out - just get away and let it burn until the chemical reactions stop...

ex-Gooserider

[Burgerman]

What I can tell you is that unless they are superbly calibrated the cells will LOOK to be unbalanced between 95% full and 10% charge remaining. (And that a typical BMS that balances all the time, sees the same thing and will UNBALANCE the cells trying to fix a non existant balance error! So dont use one of those!) Its not actually true, as the PL8 showed on terry's battery...

In adition the vast majority of the day the voltage remains almost constant. It may even climb as it becomes discharged, as it warms up. That will be displayed as anywhere from 90% to about 20% remaining, depending on actual cell manufacturer and exact chemistry and temperature. So ignore it as a fuel tank because it tells you nothing. It will make you think that the battery is way lower than reality. Because most are based on HOBBY A123 small cylindrical cells, that have a little higher voltage in use. It IS useful as a low voltage alarm set to 2.9V so you dont damage the cells. Thats its purpose.

[terry2]

You might want to consider an electrical jointing compound ...
https://www.ebay.co.uk/itm/Unial-Univer ... ctupt=true

I will get a tin of that. Thanks woodygb

[Scooterman]

I did a bench test, I was worried and got up at 6am. The graph looks okay, but whether it'll will stay that way over time I'll just have to see...

I wonder whether the higher cell resistance of cell 4 is due to me having two physically separated 12v packs. The series links between 4 and 5 are about 3x longer than the series links between the other cells.

[terry2]

I did a bench test, I was worried and got up at 6am. The graph looks okay, but whether it'll will stay that way over time I'll just have to see...

I wonder whether the higher cell resistance of cell 4 is due to me having two physically separated 12v packs. The series links between 4 and 5 are about 3x longer than the series links between the other cells.

Those are better than mine. Here is a new one from today

I did put a new cross wire on 1-2

[Burgerman]

It may well be. But still check inter cell connectors and balance wires, connectors, etc on 4, 5 and 6. But not urgent. It may be that a squirt of switch cleaner on the connectors, or a tighten of the bolts will make it all perfect. Or it may always be that way.

[woodygb]

Scooter ...I would try increasing the "size" ( cross sectional area mm2 ) of your link wire by a factor of 3.

[Burgerman]

The highest one is 1.2mOhms which is nothing really.

[woodygb]

The highest one is 1.2mOhms which is nothing really.

I totally agree ...however .. if Scooter wants to strive for perfection ..then he could try resizing his link wire.

[terry2]

It may well be. But still check inter cell connectors and balance wires, connectors, etc on 4, 5 and 6. But not urgent. It may be that a squirt of switch cleaner on the connectors, or a tighten of the bolts will make it all perfect. Or it may always be that way.

Ok BM.

I have someone coming round today, so he can lift the chair on to my old MKs

I will have to strip down the pack as I can't get to cells 5-6

[Burgerman]

Thats about all lead bricks are good for in 2019.

When its possible to fit a USABLE 160Ah safe lithium, with a healthy 16Ah in reserve, that will last a decade.
What use are 73Ah lead bricks that only last a year used hard, and have just 40Ah usable. Initially... At double the weight and half the price.

You are paying half the cost with lead. But are getting 7 to 10x less service life. And at least 4x less "fuel" and storage. And 10x slower charging. They come complete with range anxiety that stops you having a life in the evening...

[steves1977uk]

I did a bench test, I was worried and got up at 6am. The graph looks okay, but whether it'll will stay that way over time I'll just have to see...

I wonder whether the higher cell resistance of cell 4 is due to me having two physically separated 12v packs. The series links between 4 and 5 are about 3x longer than the series links between the other cells.

Those are better than mine. Here is a new one from today

I did put a new cross wire on 1-2

Terry, you don't leave the cell monitor connected while charging do you?

Steve

[terry2]

I did a bench test, I was worried and got up at 6am. The graph looks okay, but whether it'll will stay that way over time I'll just have to see...

I wonder whether the higher cell resistance of cell 4 is due to me having two physically separated 12v packs. The series links between 4 and 5 are about 3x longer than the series links between the other cells.

Those are better than mine. Here is a new one from today

I did put a new cross wire on 1-2

Terry, you don't leave the cell monitor connected while charging do you?

Steve

Yes I left the monitor connected

Unplug it then I take it?

[Burgerman]

The monitor only takes a small current, but if connected all day it will slightly unbalance cells 1 and 2. And if set to "balance" will UNBALANCE the pack...

[terry2]

The monitor only takes a small current, but if connected all day it will slightly unbalance cells 1 and 2. And if set to "balance" will UNBALANCE the pack...

I will make sure it's disconnected when I've done my trips.
I have never used the balance option.

The chair is up on the MKs and I am stripping down the pack.
Hopefully for the last time.

[steves1977uk]

Terry, you don't leave the cell monitor connected while charging do you?

Steve

Yes I left the monitor connected

Unplug it then I take it?

Yep, only connect it when you're going on loooooooooong runs I removed mine a few years ago since I have a good idea of how much I use my chair. Indoors I charge it once a week, but if I'm out and about then every 2-3 days for just a 75Ah pack.

You could use your chair indoors for a month easily before you needed to charge it again!

Steve

[Scooterman]

Hi Woody, yes I will try increasing the CSA of when I install the packs in the scooter.

And yes BM, I do agree with you in that bare copper isn't a good material to use, I thought that a while back when you first mentioned about it oxidising. But I'd already asked Shirley about getting the copper and didn't like to keep on chopping and changing my mind. But I didn't HAVE to use it when it arrived, but thought I might as well give it a go. I thought afterwards I wonder if I could have electrically plated it with aluminium? I've revived old silver jewellery by putting in a bowl of soda and scrunched tin foil, although it only puts a very thin layer of aluminium on, at least I think that is what happens? The jewellery comes out more 'silvery'.

Come the winter I might look and re-connecting the cells with stainless studs and soldered links. Hopefully I might be a bit better at soldering by then. But if the graphs stay good then maybe it'd be best to not disturb it I don't like to keep on doing up and undoing the battery terminal bolts incase someone 'gives' in the cells, or the aluminium threads starts to crumble.

I've taken the old 75Ah AGMs out the scooter and put them in the Salsa. The salsa has so much more grunt now, even though the leads are nearly 3 yrs old. But then I love the salsa, especially the 4 pole motors and 120Ah r-net.

Also I fitted an odometer to the scooter. I did away with the parking brake I never used once, and used the disc to mount the odometer magnet. The sensor is a reed switch and the odometer is really accurate. To calibrate I marked the floor distance of 10 wheel revs, measured the distance, divided by 10, and inputted the wheel circumference in mm. I'm going to use it along with a cell checker to gauge when to recharge the batteries.

A parking brake is require by law, but the law can go hang

[Scooterman]

Btw, after struggling to replace the lead in the powerchair I thought I'd upload the a photo of the mobility scooters battery compartment for anyone unfamiliar with mob scooters. The difference between battery and 'power' electrics access on the scooter compared to a powerchair is night and day. Although access to the non-power electrics under the plastic covers on the steering tiller are a bitch, especially the 'dashboard' pcb. Lot's of horrible plastic clips that snap and short stubby wires!



To get to the position shown in photo is just a case of getting someone strong and able bodied to light the seat off the centre post, undoing three bodywork screws, lifting bodywork of after unplugging rear lights. And that's it! Trouble is the seat is just too heavy and awkward for me to lift off . It's frustrating having to ask someone to come over just to do that

[Burgerman]

And I thought I would upload my breakfast...
These pies are solid ham and turkey. Bigger than it appears here and around 18 pounds for all 4 bits...
Feels like I swallowed a brick now.

And 4 cream cakes!

My ex just dropped them off. She has been shopping. She knows what I like!

[Scooterman]

And I thought I would upload my breakfast...

As long as you don't physically 'upload' your breakfast you'll be alright. Although perhaps that might not be a bad thing?

The pie looks really nice, but I'm not keen on chocolate eclairs. I like them 'cream slices' is that what they're called? They're layers of flaky pastry, (bit like a short leaf spring) with cream in between and icing on the top.

[terry2]

All the connections was replaced. Yes they was soldered. It's a little bit better..
But the Volts on each cell are down from before.

I'm going to discharge 20AH out of it. Then recharge...