A Few Questions About LIFEPO4

Hello everyone.

I am in the planning stages of an electric car conversion. I am interested in using LIFEPO4 batteries (who isn’t, right?). When I look Cloud EV for example, they indicate that their batteries come with a BMS (http://www.cloudelectric.com/inc/sdetail/2196). However, in the description, they indicate “You may use almost any pure DC isolated charger to charge the packs if you employ the PakTrakr and BatteQ technology in your vehicle. Set your upper limits at 3.8VDC per cell, and your lower at 2.7VDC per cell and you are all set.” Well, can somebody tell me what is the battery’s included BMS doing if one still needs to use the PakTrakr and BatteQ? I guess my real questions is, what would one really need in order to charge a series string of LIEFPO4 batteries that have included BMS’s.


  • Joe

Exact same things here:

That info seems to conflict with other charging requirements I’ve seen from other lithium iron phosphate batteries so it’s scaring me away from using them still :slight_smile:


A fully charged and balanced Li battery pack will remain balanced as long as you do not exceed 3C in discharge. (What is 3C, you ask? C-Rate is a measurement of internal resistance as expressed as a multiple of a battery’s rated amp hours. So as an example 3C for a 100 AH battery would be 300 amps.)

Lithium batteries are very obedient. They will continue to provide current if you want it, even if it means their death and destruction. For this reason it is very important that you monitor the charge on the cell groups at all times. A 12V group of Li should not be allowed to fall below 10.8V, set your discharge cut off at this point. These puppies are way too expensive to experiment with deeper discharge cycles. This allows a level of safety for your pack. There is a specific known level at which a Li will not recover, I know what that level is…but I am not going to tell you because someone out there will set their cut off at .01VDC above that point and then blame me when their pack fails. Set your cut off at 10.8VDC per 12VDC pack. That is 2.7VDC per cell, a comfortable margin.

Quality Lif-po batteries will remain balanced as long as you do not exceed 3C in discharge. If you exceed 3C in discharge they will become imbalanced over time. This will not damage them but it will require that they be individually re-balanced to regain their full capacity. To avoid the hassle of taking your packs apart to balance them it is recommended that you employ automatic balancers in your packs. The absolute best one out there for the money is the BattEQ. If you have questions about the BattEQ do a google search.

You may use almost any pure DC isolated charger to charge the packs. Again, because of the cost of the initial investment, a tool like the PaktrakR is money well spent.

Lithium technology batteries do not behave well in freezing conditions. They will not take a charge when the pack is below 33 deg F. They do generate heat when charging and discharging under load but if you live in an area that experiences extreme cold consider insulating your battery boxes and adding a heating pad under the pack.

Li packs do not require water cooling even in desert climates, air works just fine. They do generate heat, and in the summer you do have to move that heat away from them. The air movement created by the vehicle during a drive is sufficient to cool the packs. Route this through your packs. A properly ventilated Li pack will settle in at about 114F.

Li batteries do not vent gasses as long as the discharge rate is kept below 3C. Some venting can occur above that. The venting gases are non-toxic.

Li batteries love to be kept on a charger, they have no memory effect. Many Life-Po battery packs are rated at well over 2000 charge cycles. This does not mean that you can only plug in the charger 2000 times, it means that you can fully deplete them to 10.8VDC per 12VDC pack and fully charge them 2000 times. If you only drive 50 or 60 miles a day on a 200 mile pack, and plug it in every day, you are going to get about 17 -20 years of cycles before the pack falls to 80 percent capacity, but if you drive 190 miles every day on that same 200 mile pack you should expect them to last 5-6 years

If well treated Life-Po batteries are wonderful but for most builders the upfront cost will still force the use of Lead Acid technology.

1 Like

chargers are extremely important for lifepo4 cells, it should cooperate with its BMS. otherwise bad cycle life because of imbalance.

Do not only can not think.