lifepo4 batteries in a golf cart

[dougs_huntingcart]

So I'm going down this major rabbit hole of understanding the lithium battery application in a golf cart and another post had referenced this guy in the video (link below). It's a 13min video that may be worth your time if you are like me and trying to understand this stuff before plunking down 2 grand on batteries. Maybe someone can comment about the lifepo4 battery use in the golf cart application and how best to manage heat, because I think with the bms we can manage the charge variables.

So he's discussing the solar application of lithium banks, charge/discharge rates, temperature.... all the things covered in many posts. But what interests me here is how is this solar discussion corelate to the golf cart application and are his talking points in direct relationship to the real world use of lithium in a golf cart.

What is really compelling here is the management of temperature in this lithium ion phosphate . I mean we're talking about utilizing batteries in an application that can have high charge and discharge rates, in hot temperatures. We also talk about charging to 99% capacity. Well, if you correlate that to the information this guy discusses in this video, makes me wonder how "real world" these manufacturer rated charge cycles is.

https://www.youtube.com/watch?v=Yf9N9zBgyB8

[Pat911]

Hi Dougs_huntingcart,

There are no set rules that you must abide by all the time except for the overcharge and overdischarge limits. Definitely don’t charge above 100% or discharge below 0%. These percentages represent different voltages for different chemistries. Cell damage will occur if these limits are exceeded. Fire can also result days, weeks or months down the track if a particular cell develops a short due to charge/discharge abuse.

You can charge/discharge between 85% and 20% for normal use but if you need more capacity on a particular day you can charge up to 100% and discharge below 20% if needed. A 100% cycle every now and then won’t make that much difference to cell capacity.

Installing a larger battery to begin with will reduce the C rate as well as reducing the need to use 100% of capacity. This will also reduce heat generated within the cell. Discharging at 200A on a 100Ah battery gives a discharge rate of 2C. Increasing the battery to 200Ah drops the discharge rate to 1C. There’s not much you can do about discharging at high ambient temperature except for not using your cart when it’s hot. Installing a ventilation fan in the battery compartment may be beneficial but it also may introduce hot ambient air into the compartment. You will have to monitor temperatures to see if it will be beneficial. Charging at or below C/2 won’t generate much heat at all, especially as most charging will be done in a cooler garage over night.

You should keep your batteries at around 50% charge until you need to use the cart. Charge up to 85% (or 100%) just prior to using the cart. Unlike FLA, you should never store your cart with your batteries at a high charge level.

Al these measures will help increase battery life but rest assured, as long as you adhere to the simple measures of not charging above 100% or discharging below 0%, and not storing the battery at high charge levels, lithium batteries will easily outlast FLA batteries and give far better performance even when factoring in the higher initial cost.

Cheers
Pat.

[dougs_huntingcart]

Originally Posted by Pat911

Hi Dougs_huntingcart,

There are no set rules that you must abide by all the time except for the overcharge and overdischarge limits. Definitely don’t charge above 100% or discharge below 0%. These percentages represent different voltages for different chemistries. Cell damage will occur if these limits are exceeded. Fire can also result days, weeks or months down the track if a particular cell develops a short due to charge/discharge abuse.

You can charge/discharge between 85% and 20% for normal use but if you need more capacity on a particular day you can charge up to 100% and discharge below 20% if needed. A 100% cycle every now and then won’t make that much difference to cell capacity.

Installing a larger battery to begin with will reduce the C rate as well as reducing the need to use 100% of capacity. This will also reduce heat generated within the cell. Discharging at 200A on a 100Ah battery gives a discharge rate of 2C. Increasing the battery to 200Ah drops the discharge rate to 1C. There’s not much you can do about discharging at high ambient temperature except for not using your cart when it’s hot. Installing a ventilation fan in the battery compartment may be beneficial but it also may introduce hot ambient air into the compartment. You will have to monitor temperatures to see if it will be beneficial. Charging at or below C/2 won’t generate much heat at all, especially as most charging will be done in a cooler garage over night.

You should keep your batteries at around 50% charge until you need to use the cart. Charge up to 85% (or 100%) just prior to using the cart. Unlike FLA, you should never store your cart with your batteries at a high charge level.

Al these measures will help increase battery life but rest assured, as long as you adhere to the simple measures of not charging above 100% or discharging below 0%, and not storing the battery at high charge levels, lithium batteries will easily outlast FLA batteries and give far better performance even when factoring in the higher initial cost.

Cheers
Pat.

Thanks Pat. I'm ready to get into building my own pack . Just need to pick out the right components.
Wouldn't it be cool to have a radiator and way to keep the batteries thermally neutral at 70 degress F ... I was watching a video on how tesla designed their cooling system for the car/ battery compartment.

[Pat911]

Now that’s a thought!

Not worth the effort for cool climates like where I am but I can see the benefits for warmer climates.

Cheers
Pat.