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Tech Help / To use full BMS or not to use full BMS
« on: May 24, 2013, 11:35:19 AM »
Looking for some experienced help. I have a very nice DIY conversion electric motorcycle, a 1990 Yamaha FZR with a great AC motor and currently using 6 (alleged) 50AH 12V SLAs to run 72V (http://www.evalbum.com/3918): the motor has a peak of 36HP and the controller is 300A. But the batteries are already getting tired (yes, I know they're not deep-cycle) and range is now only about 10 miles, and that's not enough.
I want to go to lithium, and I assume I will try to use good-quality iron phosphate batteries. But, I have a few questions. First, I have individual chargers for each of my 6 SLAs, and I'd like to retain this basic layout, such that I will connect in series 6 12V battery-blocks which each contain 4 batteries and each charger will charge each battery-block. Based on size, cost, and desired range factors, I figure I will get 60AH cells (3V x 60AH x 24 cells = 4.3KWH).
Question 1: Is it possible to use a simple PCB (http://www.batteryspace.com/pcmprotectioncircuitmodulefor4cells128vlifepo4batterypackat16alimited.aspx) for each 12V battery-block of 4 cells, and not use full BMS?
Question 2: If the answer to question 1 is "yes," then what are the appropriate matching battery and PCB amp ratings, assuming the bike will be asked to go fast sometimes?
Question 3: I want to rely on the Soneil 14.7V chargers to keep the cells from overcharging: is this a risk?
Question 4: Do I need to do anything to the Curtis controller when I make the switch? Frankly, I find the controller indecipherably difficult to set up, and I'd just as soon leave it alone if that's possible.
Question 5: I understand that draining these batteries too far is very bad for them, and the PCB will not prevent that, and that it would be on me to keep a close eye on voltage to make sure this is not a problem. Is this an acceptable solution?
Thanks.
jzj
I want to go to lithium, and I assume I will try to use good-quality iron phosphate batteries. But, I have a few questions. First, I have individual chargers for each of my 6 SLAs, and I'd like to retain this basic layout, such that I will connect in series 6 12V battery-blocks which each contain 4 batteries and each charger will charge each battery-block. Based on size, cost, and desired range factors, I figure I will get 60AH cells (3V x 60AH x 24 cells = 4.3KWH).
Question 1: Is it possible to use a simple PCB (http://www.batteryspace.com/pcmprotectioncircuitmodulefor4cells128vlifepo4batterypackat16alimited.aspx) for each 12V battery-block of 4 cells, and not use full BMS?
Question 2: If the answer to question 1 is "yes," then what are the appropriate matching battery and PCB amp ratings, assuming the bike will be asked to go fast sometimes?
Question 3: I want to rely on the Soneil 14.7V chargers to keep the cells from overcharging: is this a risk?
Question 4: Do I need to do anything to the Curtis controller when I make the switch? Frankly, I find the controller indecipherably difficult to set up, and I'd just as soon leave it alone if that's possible.
Question 5: I understand that draining these batteries too far is very bad for them, and the PCB will not prevent that, and that it would be on me to keep a close eye on voltage to make sure this is not a problem. Is this an acceptable solution?
Thanks.
jzj