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Old 12-18-2014, 11:07 AM   #7
sunking
Gone Wild
 
Join Date: Oct 2009
Posts: 486
Default Re: Converting to Lithium

OK to start To equal 48 volt @ 225 AH FLA will require 48 volt @ 100 AH of lithium as both will give you 80 AH of usable energy.

The type of lithium battery used in a cart is not the same type used in EV's for a couple of reasons.

1. Cost. EV's use Lithium Cobalt and Lithium Manganese. These are high energy density and cost upward around $2 to $2.50/wh. Or for a 48 volt 100 AH battery about $10,000. The type used in carts and DIY EV's is Lithium Iron Phosphate aka LiFeP04 or LFP for short. LFP can be bought for as low as $.0.3 to $0.45/wh or around $2000 to $2600 depending on manufacture.

2. As mentioned the type of Lithium EV's use are high energy density. All that means is watt hours/Kg. Being very high energy density means unstable and prone to catching fire. To prevent that means EV manufactures have to use thermal management, and that is expensive. LiFeP04 is very stable and does not require any thermal management, and only Passive BMS (battery management system).

Lastly LFP is very forgiving when charging and can tolerate some over charging. But like any lithium be aware they DO NOT TOLERATE being over discharged. You need to make note of this because one thing every golf cart owner does is over discharge their batteries. You do that one time with Lithium and you turn them into a BRICK which makes for a nice expensive Boat Anchor.

Now that we have that out of the way lets talk specific brands and where to get them. Calb and GBS are the two go too's. Calb is the least expensive but will require some fabrication to bind them together. Something like a box. Under Calb you want the gray CA series. For 48 volt takes 16 cells as each cell has a nominal 3.2 volts. Most DIY EV builders get their Calbs from Electric Car Parts Company. You are looking for Calb Ca-100. They cost around $125 per cell for a quantity of 16.

The other is higher quality and they make drop in replacements with BMS included. They use GBS 100 AH cells. I bought mine from Elite Power Solution. I used the Turnkey option with the BMS Balance boards included. These are a bit expensive, but GBS are really good batteries and you get a drop-in package.

OK let's move on to chargers. Unless you know how to modify electronics just buy a charger from whoever you buy the batteries from. The good thing about Lithium is they do not have to be charged as slow as FLA batteries. FLA batteries are typically charged at C/10 or 10 hour rate. Lithium can be charged up at 1C or 1 hour rate if you can afford it.

There is one extra peice of equipment you will want. A Low Voltage Cutoff. It is needed to protect the batteries. It literally disconnects the batteries if you reach the Cutoff Set Point. On a AC cart it is really easy as it is built into the controller to operate the Run Solenoid. If you have a DC motor/controller I am not sure what is out there.

That is the basics and all for now. Let you digest that and start pricing things out. If you survive sticker shock, ask more questions.
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