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  #31  
Old 07-06-2012, 09:19 PM
albo2 albo2 is offline
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Default Re: Finally starting my MX5(Miata) conversion

well the front box is finally in.
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  #32  
Old 07-06-2012, 09:26 PM
Grant_NZ Grant_NZ is offline
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Default Re: Finally starting my MX5(Miata) conversion

Sweet.. almost done

Quite small cells for 200Ah, I take it your packs going to be 102 volts at 200AH? If so, how far will that get you?

Last edited by Grant_NZ; 07-06-2012 at 09:32 PM. Reason: bad speller...
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  #33  
Old 07-07-2012, 06:23 AM
albo2 albo2 is offline
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Default Re: Finally starting my MX5(Miata) conversion

Quote:
Originally Posted by Grant_NZ View Post
Sweet.. almost done

Quite small cells for 200Ah, I take it your packs going to be 102 volts at 200AH? If so, how far will that get you?
Hi grant. I expect to get about 104 miles brandon holinger has done pretty much the same conversion with 36 cells he burns about 200 w/hours per mile I require 84km for my commute into town the cells are the same form factor as the CALB 180 ah, It doesn't feel almost done but I think most of the time consuming stuff is placement of the cells should start to move along now well hopefully I just want it ready for summer its alot of fun to drive
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  #34  
Old 07-08-2012, 02:52 PM
albo2 albo2 is offline
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Default Re: Finally starting my MX5(Miata) conversion

Have decided to bottom balance the cells to 2.8 volts, just at the start of the discharge knee, I have done this with a couple of cells already, these cells hold an incredible amount of energy I have them regen discharging into a 12v lead acid and the lead acid running one of the spots on the Mazda, it takes a good couple of hours.
I will then charge the entire pack, I have a chinnic charger programmed to 117 volts 3.65 volts per cell, I was told they could only program 1 profile so that gives me the option of adding another couple of cells and still charge to 3.44 volts per cell, this drifting I have read about appears to be a load of nonsense I have had these for a couple of months now and they are still at exactly 3.08 volts per cell, I have a crate not yet opened they will be the same.
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  #35  
Old 07-26-2012, 02:56 AM
albo2 albo2 is offline
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Default Re: Finally starting my MX5(Miata) conversion

I don't think I balanced them properly after a full charge most of the cells were around 3.43 but. 3 of them were over 4 volts so its back to the drawing board, I finished the balance at 5 amps this time Ill do it at 2 amps I've now figured out how to do 5 cells at once it takes about 12 Hours to run them down and they were out of wack this time Im discharging to 2.75 volts. finishing at 2amps.

If anyone wants to know how to connect multiple cells to the power lab I cut the boards off and extended the leads soldering a 8mm terminal to each end,

the number of white leads determines how many cells you can connect, I have 5 on mine, if you number them 1 would be closest to the black and 5 to the red

with the cells connected in series black goes to most negative, white lead 1 to the strap between cells 1 and 2 either end it doesn't matter with each white lead connecting to the corresponding strap eg white 2 to the second strap between cells 2 and 3 with the last white lead sharing the most positive with the red lead

you will want to connect the heavy bannana leads to the most positive and most negative as you will be discharging for the rest of your days without them, don't choose the. option to balance entire charge all the othe options are the same as charging a single cell.

hope this helps as it took me a while to figure this out.
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Last edited by albo2; 07-26-2012 at 04:19 AM.
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  #36  
Old 07-26-2012, 04:26 AM
albo2 albo2 is offline
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Default Re: Finally starting my MX5(Miata) conversion

I have also made some progress I have fitted a fuse on my. rear box i had to emove the entire box to work on it so i have made a few alterations check it out I'm quite happy with how it's coming together
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  #37  
Old 07-26-2012, 05:09 AM
drgrieve drgrieve is offline
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Default Re: Finally starting my MX5(Miata) conversion

Quote:
Originally Posted by albo2 View Post
I don't think I balanced them properly after a full charge most of the cells were around 3.43 but. 3 of them were over 4 volts so its back to the drawing board,
Hi there.

If you bottom balance (which I agree with) then you gain the benefit of not bricking your pack if you ever happen to discharge it fully. However when you charge you will exaggerate any capacity differences between your cells at the top.

So first question is - What is the capacity difference between your largest and smallest cells in ah?

2nd questions is. Are you charging constant current, constant voltage and what is your terminating amps? For a bottom balanced pack I would charge at most C/3 (thats 60 amps! less is OK of course) CC then to 3.5v CV terminating at C/20 (that is 10 amps for a 200ah pack).

3rd question is the 3.43v and over 4v charging voltage (which is fairly meaningless) or resting voltage. You should be aiming for a resting voltage in the region of 3.33 to 3.35 voltages (24 hours after charging). This would indicate a pack charged to 90 to 95% capacity.

I think that under charging the pack slightly increases cycle life.

This is information gathered from watching the EVTV episodes on charging, YMMV as differences with the Sinopoly cells are not really known at this point - but this information should be fairly close.

Cheers!
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  #38  
Old 07-26-2012, 08:08 PM
albo2 albo2 is offline
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Default Re: Finally starting my MX5(Miata) conversion

Quote:
Originally Posted by drgrieve View Post
Hi there.
.

Q What is the capacity difference between your largest and smallest cells in ah?


2nd questions is. Are you charging constant current, constant voltage and what is your terminating amps? For a bottom balanced pack I would charge at most C/3 (thats 60 amps! less is OK of course) CC then to 3.5v CV terminating at C/20 (that is 10 amps for a 200ah pack).



3rd question is the 3.43v and over 4v charging voltage (which is fairly meaningless) or resting voltage. You should be aiming for a resting voltage in the region of 3.33 to 3.35 voltages (24 hours after charging). This would indicate a pack charged to 90 to 95% capacity.



I think that under charging the pack slightly increases cycle life.

This is information gathered from watching the EVTV episodes on charging, YMMV as differences with the Sinopoly cells are not really known at this point - but this information should be fairly close.

Cheers!
Hi drgrieve I'm also a big fan of EVTV, I'm even going to EVCON will you be there? To answer your questions I'll try:

Answer 1: They should all be over 200 amp hours, haven't measured them as that would be a major undertaking, was not provided with a data sheet

Answer 2: Answer: I have a TC/Chennic/what else are they called Elcon loaded with the profile for no BMS it is set to charge to an average of 3.65 volts per cell so cuts off at 117 volts, max amps will be well below 60

Answer3: Yes I measured the voltages at the end of the charge cycle just before cut off, you are probably right I needn't be that concerned however I want to make sure the pack is set up right and the cells I have fully discharged did reach the bottom at different stages, now I can do them 5 at time I can compare them, I'm only talking .1 of a volt but I will know I've done it properly. With the resting voltage wouldn't you have to dismantle the pack before leaving them to rest otherwise they will all read the exact same voltage?
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  #39  
Old 07-29-2012, 07:34 PM
albo2 albo2 is offline
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Default Re: Finally starting my MX5(Miata) conversion

Was about to chop the end off my throttle cable when I remembered a handbrake I purchased for my son when his hands were too small to fit the brake on his bike he's now 16 so I don't think he'll mind me using it it fits the cable perfectly
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  #40  
Old 07-30-2012, 06:57 AM
Jesse67 Jesse67 is offline
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Default Re: Finally starting my MX5(Miata) conversion

When you are bottom balancing your smallest capacity cells will arrive at the fully charged state first, think of it as a row of different sized cups, all empty. Now start pouring water into them at the same rate. The smallest one will overflow first which is whats happening to your two cells going to 4 volts. If they are a couple Ah smaller than the rest and are going to 4V on charge you will have to pick a lower final charge voltage to keep them happy.

That said it's an excellent idea to re check your bottom balance point. A lower final voltage and a smaller current draw just like you're doing should help. I would imagine differences in internal resistance will be exaggerated near empty so you want to minimize the effects of voltage sag by using as low a current as possible.

Do you have room for end plates and straps in those boxes or is the decking material stiff enough to prevent the end cells from bulging?

Nice build! Looking great so far.

Jesse
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