# lithium batteries



## gaminde (Sep 18, 2011)

I'm seeing prices of 600 - 700 for lithium batteries where ?? Im looking into replacing my golf cart batteries with lithium, and having some trouble with the size needed or what compares to the t1275 lead batteries ?? I would like to up the voltage to 55 so 15 batteries ? where would I get a charger to fit this pack size ??


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## GizmoEV (Nov 28, 2009)

As a general rule of thumb it takes 4 LiFePO4 cells to replace a 12V battery. The nominal voltage of a LiFePO4 cell is 3.2V but charging voltage will be any where from 3.45V to 3.8V depending on the cell and what you believe about charging LiFePO4 cells. FWIW, my testing and experience so far says that 3.5V is plenty for charging.

Before you change voltage you need to find out what the input voltage range is for your controller, DC-DC converter if you have one, and charger. If you give specific details about your setup, including model numbers, we can help you more specifically.

On my rig I went from a 48V lead acid setup to a 20 cell LiFePO4 setup and I only charge to 69.3V total because my DC-DC doesn't work at voltages much above that and that is close to my controller's limit of 70V. I had my Zivan charger reprogrammed for my pack. Note that this took me from a 20-30mile range to a solid 70mile range even at full throttle. For a Golf cart you probably don't need that kind of range.


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## gaminde (Sep 18, 2011)

GizmoEV said:


> As a general rule of thumb it takes 4 LiFePO4 cells to replace a 12V battery. The nominal voltage of a LiFePO4 cell is 3.2V but charging voltage will be any where from 3.45V to 3.8V depending on the cell and what you believe about charging LiFePO4 cells. FWIW, my testing and experience so far says that 3.5V is plenty for charging.
> 
> Before you change voltage you need to find out what the input voltage range is for your controller, DC-DC converter if you have one, and charger. If you give specific details about your setup, including model numbers, we can help you more specifically.
> 
> On my rig I went from a 48V lead acid setup to a 20 cell LiFePO4 setup and I only charge to 69.3V total because my DC-DC doesn't work at voltages much above that and that is close to my controller's limit of 70V. I had my Zivan charger reprogrammed for my pack. Note that this took me from a 20-30mile range to a solid 70mile range even at full throttle. For a Golf cart you probably don't need that kind of range.


*No converter yet and the ones I have looked at go to 72 volts, I think I can do 60 vdc with my stock controller. my charger now puts out 60 vdc so If i use 17 battery packs can I use this charger, or will a charger a new charger be needed no matter what. Im being very general right now just looking into converting batteries and maybe controller replacement also, and will do this in some sort of sequence so I can stay running and step through the upgrade. *


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## frodus (Apr 12, 2008)

what charger do you own?

Is it for SLA batteries? If so, don't use it with lifepo4.

and go in groups of 4, 4, 8, 16, 20, 24...etc. 15 and 17 are odd numbers and can complicate things like BMS, chargers and controllers choices.


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## gaminde (Sep 18, 2011)

frodus said:


> what charger do you own?
> 
> Is it for SLA batteries? If so, don't use it with lifepo4.
> 
> and go in groups of 4, 4, 8, 16, 20, 24...etc. 15 and 17 are odd numbers and can complicate things like BMS, chargers and controllers choices.


 Excellent thank you these are the little trips I need to know. How do you pick chargers they seem to be for specific voltages


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## frodus (Apr 12, 2008)

where are you looking that you're having trouble?


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## gaminde (Sep 18, 2011)

frodus said:


> where are you looking that you're having trouble?


Well from this site to China and in-between


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## GizmoEV (Nov 28, 2009)

As frodus says, don't use your lead acid programmed charger for lithium. I initially used my Zivan NG1 still programmed for lead acid and had to charge 18 cells to just under 4vpc so that the charger didn't cut back too soon and then time out without finishing the charge. After reprogramming the charger it does just fine and in less time since it runs full throttle right up the the last few minutes.

The number of cells you use may or may not be complicated by the BMS if you use one. I'm not sure which ones frodus is alluding to but with ones like the Black Sheep Technology units I used it doesn't matter what number of cells you use. Whether you use a BMS or not should be a carefully considered decision as each way you go has its pros and cons along with "religious fervor" on both sides of the issue. In any case, you will probably be happiest to go with at least an even number of cells rather than an odd number.

Also note that the top voltage you intend to charge to may have a bearing on how many cells you go with. Many charge to 3.65vpc but I'm finding more and more who are only charging to 3.4-3.5vpc since there is very little energy above the 3.4V charging voltage. The idea is that the cells will not spend as much of their life at 100%SOC and thus will have a longer calendar life and cycle life, also, charging to a lower voltage provides a bigger safety range at the end of charge so there is a lower likelihood of grossly overcharging a cell.

If you post the brand and model numbers of your equipment we may be able to help you more.


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## tomofreno (Mar 3, 2009)

The capacity of the T-1275 is 150Ah at the 20 hour rate, 100Ah at 60A discharge current, and about 80Ah and 140A, so 100Ah cells should work well to replace it. Four of them connected in series would replace one T-1275, with nominal 12.8V and about 3.5V rest voltage about 10 minutes after charge, before use.


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