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Discussion Starter · #1 ·
I am considering building a lithium battery pack for my EV. I know the original batteries are lead acid and operate at 48 volts but most 12 volt batteries are charged to about 13.8 to 14.2 volts. This would imply the controller can operate with at least 55.2 volts (13.8 x 4) assuming you operate the machine immediately after taking it off of the charger. My question is does anyone know what the maximum voltage is that the controller will operate with? Most controllers have a high voltage cut-out and am just wondering if anyone knows what that voltage is. I would like to build the highest voltage pack that will operate with the original controller. I'm planning on using lithium iron phosphate battery cells and therefore I can build a battery pack in roughly 3.2 volt increments. 15 cells in series equal 48 volts. If possible I would prefer to build the pack using 16 cells in series which will operate at 51.2 volts but will charge up to 58.4 volts.

Thanks....
 

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Discussion Starter · #2 ·
Grumpyb,

I found a thread that you posted (guess I should have searched before asking) regarding the Sevcon controller being capable of a max of 69 volts. Do you know if that is applicable to the controller used on a 2010 model?

Thanks...
 

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Grumpyb,

I found a thread that you posted (guess I should have searched before asking) regarding the Sevcon controller being capable of a max of 69 volts. Do you know if that is applicable to the controller used on a 2010 model?

Thanks...
I've had my 2011 SEVCON running at 56.0V. The pack was 7 Nissan Leaf cans charged to 8.0V each. When I added the 8th one, for 64.0V, it would not operate. I got a code.

So it's possible that the SEVCON will run at 69V, but I think you'd need someone to adjust the programming.

I need to get the BMS fitted to the pack. Once I do I will see how high the charger will take the pack before it trips the SEVCON. With the Ranger up on jacks, it should not be a long test. But I'm 6 months into building the pack .. so I wouldn't hold my breath!
 

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Discussion Starter · #4 ·
Thingstodo,

Thanks for the info. It sounds like the Sevcon will protect itself from overvoltage which is good. I'm thinking I can just hook up one of my variable power supplies and slowly increase the voltage until the Sevcon trips out. This would give me my upper voltage limit.

I was originally thinking about using Nissan leaf cells also but it seems lately most of the ones being sold are advertised as 70% capacity and typically a lithium battery is considered "used up" once they drop to 80% capacity. Regarding the BMS I fully understand. Having built several lithium packs in the past I can agree that most of the effort is getting the BMS installed in an orderly manner and operational. Good luck with your install.

I'm also curious as to what the upper voltage limit is for the 48v to 12 DC/DC converter and does it protect itself from overvoltage.
 

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Worked well. Get the BMS from overkill solar. I have about 20kWh of usable battery life which is plenty. I gopt the cells from batteryhookup.
 

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Discussion Starter · #6 ·
Deertay,

Thanks for the link and info. I noticed that Battery Hookup is currently out of the Nissan Leaf batteries. For the price, these would be worth trying even at roughly 70% capacity. I wonder when/if they will be getting any more in.
 

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You simply have to change the setting in the Sevcon. The sevcon gen 4 48v has a max voltage of 69v. Its normally programmed to not function above 64 so you need to change that setting and change the low voltage to reflect the discharge of the lion, otherwise with original low in the 30(s)v will take you way into over discharge area on the cells.
 
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