# Upgrade to Lithium



## TTmartin (Feb 7, 2012)

I thought I would share my experience of upgrading to lithium for anyone who is thinking of doing the same but has reservations as I did initially particularly regarding the expense and weather they are as good as people say they are? I'm definitely what's described as a newbie, 1 1\2 years ago I never knew there was such a thing as a DIY Electric car. I spent well over a year converting a Mk1 Audi TT and ended up with a Kostov 11" 192v motor, Soliton 1 controller and 12, 12volt lead batteries (second hand batteries). After debugging the car to the point where it actually worked quite well other than only 5 miles maximum range, it was decision time! Upgrade to lithium or maybe get some new lead?

​Long story short, took the plunge and ordered 73, 100AH sinopoly cells, 6 weeks later they arrived, connection straps and hardware included. Removed the cells from there well made shipping crates and checked voltages, every cell was sitting at 3.294v to 3.295v.

​After much reading on these forums and elsewhere I decided to bottom balance. I installed the cells in the car and very carefully drove checking pack voltage and each cell frequently with a DVM slowly gaining confidence in how they behave. After a lot of start, stop, measure, driving I got the pack to 3 v per cell resting no cell ever sagged below 2.9 v, At this point I was starting to notice some slight variation in cell voltages Thats as far as I was going, time to bring each cell down to 2.7 volts individually. I've made a bottom balancer using a resistor that draws about 22 amps from a cell, this is controlled with relay and programmable volt meter. Not my design just searched on YouTube etc and put it all in a box. Anyway 3 days later every cell was at 2.702 to 2.705 volts resting, I think that's good enough.

​The first charge was a tense time, running around with a DVM checking 73 cells as I did'nt know what to expect. All the cells came up nicely together to around 3.4 v per cell at which point a few started to go ahead of the rest, this made life easier to check for the first cell to reach 3.5 volts. The first cell reached 3.5 v when the pack was at 249.5 volts, the JLD404 meter counted 126.4 amp hour in to the pack. The charger will be programmed to end charging at this voltage but also as back up I have 2 programable meters which will stop the charger, one counting amp hour in and the other monitoring pack voltage. The pack has been recharged about 6 or 7 times now and has reacted identically each time. Initially I was checking every cell frequently but every thing is so consistently the same I now just keep an eye on 3 or 4 cells that go ahead near the end of charge but it's the same every charge, the amp hour I take out driving I count back in when charging, so the checking of each cell will now become a monthly avent then maybe 6 monthly. Gaining confidence daily. The JLD404 meter is Just like a fuel gauge so you always know where you are as regards remaining range. Also the soliton 1 has minimum pack voltage settings at rest and under load, At 80 amp hour used I'm getting between 50 and 60 miles depending on driving style and the pack is at 237volts resting at this point. I think I could safely use 100 ah if needed as the pack initially accepted 124.6ah on the first charge. Shortly after ordering the cells I was informed they would be new spec with extra capacity, this certainly seems to be the case. How accurate my amp hour counter is? Not sure but the numbers are consistent going in and out, so as a fuel gauge along with pack voltage monitoring all is good at the moment. As many people have stated on this forum, if you stay away from the top and bottom all will be ok, this is my experience so far.

​Not having any experience with batteries in general let alone lithium I'm amazed at the energy density of these sinopoly cells. Driving the car is a real pleasure now, with lithium it's now a viable car compared to lead.

http://electrictt.blogspot.co.uk/

http://www.youtube.com/watch?v=hksc-XgGSbg

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## crackerjackz (Jun 26, 2009)

Nice build ! Great clean job  congrats


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## onegreenev (May 18, 2012)

Awesome story. Nice to hear about folks switching over to lithium. Nice car.


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## kennybobby (Aug 10, 2012)

Congrats on getting into Lithiums, bet the car is fun to drive with a decent range. 

Counting amps out and in seems like a good method to keep track of SOC, maybe the best method actually. 

What sort of margin are you using at the top--are you trying to put 126 Ahr back in when you charge, or have you decided on a lesser value to give a little buffer. Sure a 100 Ahr cell that can take 126 is a great value, but how many cycles will it last with stuffing extra electrons into the matrix? Just wondered if you had given it some thought, etc.


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## TTmartin (Feb 7, 2012)

kennybobby said:


> Congrats on getting into Lithiums, bet the car is fun to drive with a decent range.
> 
> Counting amps out and in seems like a good method to keep track of SOC, maybe the best method actually.
> 
> What sort of margin are you using at the top--are you trying to put 126 Ahr back in when you charge, or have you decided on a lesser value to give a little buffer. Sure a 100 Ahr cell that can take 126 is a great value, but how many cycles will it last with stuffing extra electrons into the matrix? Just wondered if you had given it some thought, etc.


Hi thank you, 
At the moment the car is to good to be true after only 5 mile range with lead but early days yet I need to get to know these cells and gain confidence.

As I mentioned I'm new to all this, without this forum I probably wouldn't have the car I've got now.
A wealth of knowledge and experience being shared, it's great You do need to be able to sort the wheat from the chaff though

The way I see it, the cells accepted 126ah because of design improvements just like most technology it's moving forward, look at phone batteries they seem to get more out of them every model change.
I charge until the first cell hits 3.5 v the pack is at 249 v at that point, on the first charge after the initial bottom balance the JLD counted 126AH in to get to 249 v so all the cells are 3.5 v or below and at rest the next day the pack is at 243 v, each cell being at about 3.338 v.
From what I'm seeing if anything I'm under charging very slightly, time will tell?
Ever since the first charge all I've done is count AH out driving and put the same amount back in charging but at the same time monitoring pack voltage so as not to go above 249 v. I use the same monitoring at the other end to make sure voltage stays at a safe level not dropping to low.
Maybe the JLD is not calibrated correctly and the 126 AH is actually only say 106 or 116 The number isn't important as long as it's consistent and inline with the voltage so the cells are staying below what is considered a safe level > 3.5 volts maybe.
From what I see when charging, a cell has capacity if it's accepting currant without rising in voltage quickly, once I get to around 3.4 v per cell the voltage climb speeds up showing they are near full, a bit like a compressed air tank, the pressure goes up when you pump air in to it and if you don't control the pressure the safety valve blows, if there is one! or the tank blows!
That's seems to me exactly why cells have swelled up, to high a voltage = to much pressure = swelled cell.
Just my thoughts, if I'm wrong I'm happy to listen and learn.
Cheers


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## Roy Von Rogers (Mar 21, 2009)

Be careful with the JLD checking amps in and amps out, its not going to be the same due to the difference in amps in and out.

I'm assuming your using a 500 amp shunt or higher, with high current it will be pretty accurate, but when you go the other way and say only put in 15 or so amps, its not going to be so accurate with a high amp shunt, due to the resolution being so small.

I had thought about using another shunt for charging, but don't find it important at this time, but may try it later when I have nothing better to do.


Roy


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## TTmartin (Feb 7, 2012)

Roy Von Rogers said:


> Be careful with the JLD checking amps in and amps out, its not going to be the same due to the difference in amps in and out.
> 
> I'm assuming your using a 500 amp shunt or higher, with high current it will be pretty accurate, but when you go the other way and say only put in 15 or so amps, its not going to be so accurate with a high amp shunt, due to the resolution being so small.
> 
> ...


I haven't seen any inaccuracey in amp hour in and out?
I can only say what I'm seeing, 
If I use say 80 amp hour counted by the JLD, then reset the JLD to zero before charging. Set the relay output from the JLD to latch at -80 amp hour to stop the charger, the numbers are spot on every time. when it stops the charge my weakest cell has just arrived at 3.5 volts, the pack is at 249 v. So far this is what I see every time weather it's 80, 50, 40 or what ever amp hour I've used. 
By the way my JLD has 2 relay outputs the second one I have set for pack voltage so if the amp hour count was incorrect the second relay output will stop the charger at 249.2
Also once I've convinced myself this is in deed consistent I'll have the charger reprogrammed to stop at the correct voltage.
As an additional back up I have a volt meter with relay output that will drop out the AC supply to the charger if I'm charging overnight when I'm not around.
So hopefully with a correctly bottom balanced pack, with no parasitic loads and the safe guards I've put in for not over charging, my sinopoly cells will serve me well, if not it will be an expensive mistake


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## kennybobby (Aug 10, 2012)

TTmartin said:


> I charge until the first cell hits 3.5 v the pack is at 249 v at that point, on the first charge after the initial bottom balance the JLD counted 126AH in to get to 249 v so all the cells are 3.5 v or below and at rest the next day the pack is at 243 v, each cell being at about 3.338 v.
> 
> Ever since the first charge all I've done is count AH out driving and put the same amount back in charging but at the same time monitoring pack voltage so as not to go above 249 v.


Excellent strategy. i would consider 3.338 after resting to be right on the mark at "100% SOC" from what i have found in testing 44 cells, also what is found in literature from vendors.


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## onegreenev (May 18, 2012)

I have charged cells to an average of 3.65 volts per cell and to 3.55 volts per cell and you know, the resting voltage was always the same, 3.34 volts give or take a few hundredths. Charging to 3.55 volts is to reduce the charging stress when the cell nears full. As it nears full the electrons need to get in. The room is full and the room full of electrons needs to shuffle around to make room for more. The fuller it gets the more this happens, stressing the cell. At rest they will settle to 3.34 or so even if you take them to 3.6 or 3.8. I know because some of the cells went to 3.78 volts and always rested at the same 3.34 volts as the others. So when near full the resting voltage is nearly the same across the board. 

So the only reason to charge to 3.55 is to reduce stress and increase longevity of the cell. It is also known that the extra few AH's into the cell once you reach 3.5 volts is very little usable power so why stress the cell for such a tiny amount of energy. 

I also don't stop the charge when the lowest cell reaches 3.5 volts. I stop when the average is 3.5 volts. So a few may be higher. What you don't want is your resting voltage in the 3.4 volt range or higher. That is in the stress zone. It also means you really over charged and stressed your cells.


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## steelneck (Apr 19, 2013)

What kind of performance are you getting with this motor/controller/battery configuration, especially regarding acceleration?


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## TTmartin (Feb 7, 2012)

steelneck said:


> What kind of performance are you getting with this motor/controller/battery configuration, especially regarding acceleration?


The TT has been transformed with lithium as aposed to lead.
I have the controller settings adjusted concervativly at present to give what I would consider average gas car performance, I'm more than happy and feel I'm not stressing the cells, however if I changed the controller settings The performance would be quick to say the least.
Early days yet, still getting to know the cells and how they react? It was a big investment so I don't want to throw caution to the wind just yet
To date, marks out of ten
1, kostov 11" motor 10
2, soliton 1 controller 10
3, sinopoly cells. 10


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