Setting up my Lithium connections

6846 Views 71 Replies 8 Participants Last post by DIYguy, Jan 24, 2011

spdas

Discussion Starter · Jan 19, 2011

Aloha, all. Please advise me what to buy or materials to use and where to get it for installing my 44 x 200ah (160ah case) TS cells that I am installing to get rid of the 14 lead optimas in my Toy Yaris.

1: I currently have 10xoptimas in the rear and will put 22 TS 200's there. What ready made - to + straps do I need and where to buy-OR-what materials and gauge, tools, etc. do i use to make them?

I will be charging 22 cells at a time, 22 in back and 22 in front. And want one charging point in rear. What size charging wire do I need to run from back to front to carry [email protected] max? #8, 6?

2: What gauge wire do i need to join the front and rear pack? (I probably already have it though for the current lead)

3: In front I will have 11 cells just behind the bumper and 11 cells up near the firewall.

suggestions?

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DIYguy

· #2 · Jan 20, 2011

spdas said:
Aloha, all. Please advise me what to buy or materials to use and where to get it for installing my 44 x 200ah (160ah case) TS cells that I am installing to get rid of the 14 lead optimas in my Toy Yaris.

First of all 14 x 12 volt optimas = 168 volts. 44 * 3.2 volt TS = 140 volts. Hope that is not an issue.

spdas said:
1: I currently have 10xoptimas in the rear and will put 22 TS 200's there. What ready made - to + straps do I need and where to buy-OR-what materials and gauge, tools, etc. do i use to make them?

Interconnecting bars are available where you bought your batteries I expect.

spdas said:
I will be charging 22 cells at a time, 22 in back and 22 in front. And want one charging point in rear. What size charging wire do I need to run from back to front to carry [email protected] max? #8, 6?

How do you get 80volts and 50 amps? I suspect both numbers are low....???? Go to your local welding supply store and buy 2/0 welding cable and lugs with suitable hole sizes for connections. You may need to borrow/rent/buy a crimper.

spdas said:
2: What gauge wire do i need to join the front and rear pack? (I probably already have it though for the current lead)

As above...2/0 welding cable.

spdas said:
3: In front I will have 11 cells just behind the bumper and 11 cells up near the firewall.
suggestions?

Just confused about your pack voltage and expected current draw. You should expect several hundred amps to get rolling and then perhaps as low as 50 for maintaining lower speeds. 80 volts??

spdas

Discussion Starter · #3 · Jan 20, 2011 (Edited)

DIYguy said:
First of all 14 x 12 volt optimas = 168 volts. 44 * 3.2 volt TS = 140 volts. Hope that is not an issue.

My charger is a charge controller running off of 12x200W solar panels and will put out 80v @ 40-50amps so to charge 22 cells @ 3.6V=79.20. I can go more cells to equal 80v if charging the TS cells at 3.5 is better? (23 cells)

Interconnecting bars are available where you bought your batteries I expect.

I bought the cells used so no accessories.

How do you get 80volts and 50 amps? I suspect both numbers are low....???? Go to your local welding supply store and buy 2/0 welding cable and lugs with suitable hole sizes for connections. You may need to borrow/rent/buy a crimper.

I am charging up to 160v and having to split charging into 2 so that is how i get the 80v. 3.6v per cell.
All the cabling is 2/0 for the Lead packs, so I will use as much as this for the Lithium and probably only need to make/order buss bars.

Just confused about your pack voltage and expected current draw. You should expect several hundred amps to get rolling and then perhaps as low as 50 for maintaining lower speeds. 80 volts??

On mild accelleration I use up to 200amp and cruising at 40mph I use 50amp, that is with the lead optimas.

DIYguy

· #4 · Jan 20, 2011

# 8 wire should be fine.

Any of the battery suppliers could get them for you. You may want to call around first so you don't wait for a shipment from china. Some folks have made their own from copper or even aluminum.

I hope you don't mind waiting for your car to charge... lol

Tahoe Tim

· #5 · Jan 20, 2011

DIY,
I'll bet his lead pack sags well below 140v so I am guessing he will be fine on that issue.

G

· #6 · Jan 20, 2011

You will still need a charge algorithm for your charge controller to charge your batteries. If you only are getting 80V DC then you'd need a way to bump the voltage and lower the amps to get the voltage you need. At 80 volts you will only charge to 80 volts. How are you going to up the voltage and how are you going to control the charge algorithm? You can't just plug into an outlet and let them charge with no control. I am hoping your putting your solar into a static battery bank and if so you can use an inverter to power your home and a proper charger like an Elcon that can charge to the proper voltage limits and amp limits you need.

Do you have your batteries yet? TS should provide interconnects with your cells if I am not mistaken. Yes, 2/0 cable. Is your controller able to run at a lower voltage?

Pete

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EVfun

· #7 · Jan 20, 2011

I really don't recommend charging with the pack split into two parallel packs and discharging those two packs in series. It is very hard to insure that charging current splits evenly and this is important with Lithium because the charge voltage curve is so shallow until the very end. There is no reason to charge more than just slightly into the top end of the voltage curve so it will be difficult to insure the packs both get equally full.

GizmoEV

· #8 · Jan 20, 2011

I would recommend that you get a fine wire stainless steel brush to clean off the top of the posts just before making your connections. You should also put some NOALOX or NO-OX-ID on your connections too. Aluminum oxide has a high resistance and happens quite rapidly.

For buss bars you could have a sheet metal shop make some out of several layers of copper sheet with a bend in the middle. You can see a picture of what came with my TS cells on my blog. You can also read what I did to prepare my posts here.

Do you have an Ah counter of some sort? If not I'd recommend the CycleAnalyst. Get the large display high voltage version. I have a picture of how I mounted it here. It is a very reasonably priced meter and worth every penny. You need to know how much energy you are using.

ElectriCar

· #9 · Jan 20, 2011

Let me chime in that it would be better if you can afford it to run 4/0 cable for connecting the front and back halves and to tie in to the controller. That way at higher currents you won't be wasting voltage heating your wire. Wire has resistance and higher currents will create more voltage loss which will appear as sag. 1C for your cells is 200 amps and I sometimes draw near 400. However is you have a Gizmo type vehicle that is light weight and you have no desire to race etc 2/0 would be fine.

DIYguy

· #10 · Jan 20, 2011

ElectriCar said:
Let me chime in that it would be better if you can afford it to run 4/0 cable for connecting the front and back halves and to tie in to the controller. That way at higher currents you won't be wasting voltage heating your wire. Wire has resistance and higher currents will create more voltage loss which will appear as sag. 1C for your cells is 200 amps and I sometimes draw near 400. However is you have a Gizmo type vehicle that is light weight and you have no desire to race etc 2/0 would be fine.

Perhaps 4/0 from controller to motor where current can be higher...but the rest should be more than adequate at his amperage levels. (I did exactly what you suggest though... then again, I have a Soliton1

)

DIYguy

· #11 · Jan 20, 2011

EVfun said:
I really don't recommend charging with the pack split into two parallel packs and discharging those two packs in series. It is very hard to insure that charging current splits evenly and this is important with Lithium because the charge voltage curve is so shallow until the very end. There is no reason to charge more than just slightly into the top end of the voltage curve so it will be difficult to insure the packs both get equally full.

This is a good point. Perhaps instead of charging them separately, (which I think is the intention...??) the two packs could be paralleled for charging all at the same time @ 80volts. This should keep them all the same... yes/no?

ElectriCar

· #12 · Jan 20, 2011

DIYguy said:
Perhaps 4/0 from controller to motor where current can be higher...but the rest should be more than adequate at his amperage levels. (I did exactly what you suggest though... then again, I have a Soliton1 )

Bragger! I have parallel 1/0 throughout my pack and most under the hood which is electrically equal to 4/0. I have no way to measure my motor current but I think it must hit 500A at times because I never quite make it to 400 battery amps. Most ever on kw meter was 46 at about 122V I think and then I was only trying to see what I could max out at. Either that or I don't have enough voltage to force enough current through the motor. That should be remedied in about 6 weeks or so when I get my pack installed. However with other additions ie cycle analyst, voltage relays, new tach etc it may take longer. If I did [email protected] sag free volts I'd be looking at 60ish kw!

BTW where is your new pack? I'm due 20th or so Feb.

EVfun

· #13 · Jan 20, 2011

ElectriCar said:
Let me chime in that it would be better if you can afford it to run 4/0 cable for connecting the front and back halves and to tie in to the controller. That way at higher currents you won't be wasting voltage heating your wire. Wire has resistance and higher currents will create more voltage loss which will appear as sag. 1C for your cells is 200 amps and I sometimes draw near 400. However is you have a Gizmo type vehicle that is light weight and you have no desire to race etc 2/0 would be fine.

I really think this is getting carried away. Typical running currents do not exceed 200 amps for most EVs. If you can replace 20 feet of 2/0 cable with 4/0 cable the savings will be less than 1/8 of a volt at 200 amps. If you are running a 120 volt system that amounts to less than 1/10 of 1% in a 120 volt EV. For the few seconds you draw 1000 amps (if you batteries and controller are both capable) the voltage drop is almost 0.6 volts for an efficiency loss of about 1/2 of 1%.

Even if you compare between 20 feet of 1/0 cable and 4/0 cable the difference is not great. At 200 amps the additional voltage drop is about 0.2 volts and at 1000 amps it is about 1 volt. If you regularly hit 1000 amps in a street vehicle I don't recommend 1/0 because you can make it warm. I do recommend the motor loop be wired one step larger than the battery loop (1/0 and 2/0 is typical for me) because the controller can make motor current higher than the battery current (at lower than pack voltage on the motor) but will never make the motor current lower than the battery current.

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DIYguy

· #14 · Jan 20, 2011

ElectriCar said:
Bragger! I have parallel 1/0 throughout my pack and most under the hood which is electrically equal to 4/0. I have no way to measure my motor current but I think it must hit 500A at times because I never quite make it to 400 battery amps. Most ever on kw meter was 46 at about 122V I think and then I was only trying to see what I could max out at. Either that or I don't have enough voltage to force enough current through the motor. That should be remedied in about 6 weeks or so when I get my pack installed. However with other additions ie cycle analyst, voltage relays, new tach etc it may take longer. If I did [email protected] sag free volts I'd be looking at 60ish kw!

BTW where is your new pack? I'm due 20th or so Feb.

Sorry for braggin... lol (BTW, I've done 1000 amps sag'd to 160 volts (from 205 or so)

)
Pack is on the ship. Arrives in Vancouver on the 25th and Toronto on the 7th.

DIYguy

· #15 · Jan 20, 2011

EVfun said:
I really think this is getting carried away. Typical running currents do not exceed 200 amps for most EVs. If you can replace 20 feet of 2/0 cable with 4/0 cable the savings will be less than 1/8 of a volt at 200 amps. If you are running a 120 volt system that amounts to less than 1/10 of 1% in a 120 volt EV. For the few seconds you draw 1000 amps (if you batteries and controller are both capable) the voltage drop is almost 0.6 volts for an efficiency loss of about 1/2 of 1%.

Even if you compare between 20 feet of 1/0 cable and 4/0 cable the difference is not great. At 200 amps the additional voltage drop is about 0.2 volts and at 1000 amps it is about 1 volt. If you regularly hit 1000 amps in a street vehicle I don't recommend 1/0 because you can make it warm. I do recommend the motor loop be wired one step larger than the battery loop (1/0 and 2/0 is typical for me) because the controller can make motor current higher than the battery current (at lower than pack voltage on the motor) but will never make the motor current lower than the battery current.

For most, yes. Mine is just right. I have 2/0 between batteries, 4/0 for long runs and 4/0 from motor to controller. I have had both the 2/0 and the 4/0 to motor pretty darn warm.

I wouldn't change it for sure. But yes, for most, it's true. . .and if it aint gettin warm, u don't need to change it.

EVfun

· #16 · Jan 20, 2011

DIYguy said:
This is a good point. Perhaps instead of charging them separately, (which I think is the intention...??) the two packs could be paralleled for charging all at the same time @ 80volts. This should keep them all the same... yes/no?

Could we deliberately insert a precision (0.01%) 1/2 ohm resistor in each half? The thing is, just 0.01 volt differences in per cell voltage represent quite a difference in SOC in that great middle range. I wonder if leaving the pack halves in parallel could allow them to equalize?

Well, that question brings up a big question I've had. If a big bunch of cells where all placed in parallel (say 40, 100 amp hour cells) making one giant 3.2 volt 4000 amp hour battery would the cells all reach the same state of charge if left in parallel? What would happen if all the cells where right in the middle of their resting voltage range at 3.29 to 3.31 volts each at the start? How long might that take? It would seem that even a few microvolts would slowly move charge if given some time since there is no significant current flow to cause wiring voltage drop issues.

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DIYguy

· #17 · Jan 20, 2011

EVfun said:
Well, that question brings up a big question I've had. If a big bunch of cells where all placed in parallel (say 40, 100 amp hour cells) making one giant 3.2 volt 4000 amp hour battery would the cells all reach the same state of charge if left in parallel? What would happen if all the cells where right in the middle of their resting voltage range at 3.29 to 3.31 volts each at the start? How long might that take? It would seem that even a few microvolts would slowly move charge if given some time since there is no significant current flow to cause wiring voltage drop issues.

Yes, they should all equalize. This is how to balance a new pack. Best to feed charger from two "sides" of the circuit perhaps even one tie in the middle...but yes, they should all equalize.

ElectriCar

· #18 · Jan 20, 2011

EVfun said:
I really think this is getting carried away. Typical running currents do not exceed 200 amps for most EVs. If you can replace 20 feet of 2/0 cable with 4/0 cable the savings will be less than 1/8 of a volt at 200 amps. If you are running a 120 volt system that amounts to less than 1/10 of 1% in a 120 volt EV. For the few seconds you draw 1000 amps (if you batteries and controller are both capable) the voltage drop is almost 0.6 volts for an efficiency loss of about 1/2 of 1%.

Even if you compare between 20 feet of 1/0 cable and 4/0 cable the difference is not great. At 200 amps the additional voltage drop is about 0.2 volts and at 1000 amps it is about 1 volt. If you regularly hit 1000 amps in a street vehicle I don't recommend 1/0 because you can make it warm. I do recommend the motor loop be wired one step larger than the battery loop (1/0 and 2/0 is typical for me) because the controller can make motor current higher than the battery current (at lower than pack voltage on the motor) but will never make the motor current lower than the battery current.

No, not getting carried away. I said if he can afford it, it would be wise unless he's driving something like I described that doesn't draw many amps. I did some calculations recently for someone running 1000A on 2/0. The voltage drop in wire is proportional to the length. The calculation I did was for 80 feet of wire and the voltage drop was 6.4V. That equates to two batteries being wasted heating wire, same as internal resistance in batteries. 40' would be 3.2V. Jumping to 4/0 dropped it down a good bit but don't recall how much. The 80' was for example purposes because that equates to a 2 cell drop in voltage at 1000A. My wiring in an S10 adds up to about a 65' loop.

If you're pulling 1000A you're either moving a large vehicle or racing etc. If that's the goal then I would go with even larger wire or parallel smaller ones for an equivalent larger size. IMO there's no reason not to other than money. Why lug around one or two more batteries if you're just going to waste the capacity on heating under sized wiring??? Skip the weight and spend the money on larger wire. The wire would only add a few pounds compared to additional batteries and would free up space.

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EVfun

· #19 · Jan 20, 2011

DIYguy said:
Yes, they should all equalize. This is how to balance a new pack. Best to feed charger from two "sides" of the circuit perhaps even one tie in the middle...but yes, they should all equalize.

I'm curious is they would equalize if the charging was omitted. Just parallel a bunch of cells as received (about 1/2 full) and wait for some period of time.

DIYguy

· #20 · Jan 20, 2011

EVfun said:
I'm curious is they would equalize if the charging was omitted. Just parallel a bunch of cells as received (about 1/2 full) and wait for some period of time.

Yep... that way too... Parallel and wait a bit. They're all gonna be the same.

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