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Hello All, I'm new to this forum, this is my first post. I appreciate all the help in advance.
My DIY car is a 1994 (mexican model) VW Bug. I have a 72v brushed PM DC motor, a Kelly KDZ72401 controller, and the current source of my sorrow, a 100 AH 76.8v battery pack made with 120 20 AH 3.2v cells arranged as 5p25s.
Honestly, I didn't know what I was doing (still trying to figure out) when I bought these as a kit from some online seller. I finally put it together for a first discharge run, after which I took the battery apart for bottom balancing.
On this first run yesterday, I took the car out for what ended up being a very short (7 mile) drive, with the factory charge. All batteries were 3.2x or 3.19v when I started. The thing ran fine for 5 miles or so, but once it hit the 70v it declined pretty fast and I had the controller programmed to stop at 60v.
While using it, i did get up to 50 mph for a short period of time, then stayed for a minute or so @ 40 mph and most of the driving was under that. The AMP meter was briefly, for a second at a time or so above 100 amps, and while cruising between 50 - 90 amps.
When I took the battery pack apart, i tested every battery, none seem dead, but a good bunch look swollen, these are between 2.40 and 2.43 volts and the other ones are between 2.6 up to 2.9 volts.
At this point I have 2 theories, one of them is hope, the other one is more factual.
1 - the factory charge was not 'good enough', once I bottom balance these and charge them well, the pack will perform as I expected and give me twenty some miles per charge, hopefully more.
2 - I totally don't understand how these batteries are supposed to perform and need to figure it out or I will fry these and the next pack i end up making.
The specs for these batteries are:
NOMINAL/MINIMUM CAPACITY: 20Ah @ 1/3C Discharge
STANDARD DISCHARGE CURRENT: 6.7A (1/3C)
MAX DISCHARGE CURRENT (continuous): 100A (5C)
MAX DISCHARGE CURRENT (<10 Seconds): 160A (8C)
STANDARD CHARGE CURRENT: 6.7A (1/3C)
MAX CHARGE CURRENT (continuous): 100A (5C)
DISCHARGE CUT-OFF VOLTAGE: 2.0
NOMINAL VOLTAGE: 3.2
SUGGESTED MAX CHARGE VOLTAGE: 3.65
CYCLE LIFE AT 100A (80%): 500
CYCLE LIFE AT STANDARD (80%): 4000
SELF DISCHARGE RATE (30 days): 4-6%
INTERNAL RESISTANCE/IMPEDANCE (milliohms): 2
ENERGY TYPE: 3V-3.2V-3.65V, 20Ah EV, Lithium, LiFePO4, LFP Aluminum Shell Battery
Obviously I don't understand how the AH and C work. In my simple mind, if I made a 100 AH pack, i could get 100 amps for an hour, I don't understand why each of the cells is 20Ah @ 1/3C.
Any help figuring out what happened and will happen is greatly appreciated. Right now I know I paid too much for these batteries, and I'm unsure if they are well suited for this small VW conversion, though the supplier claimed these were great.
Thanks a lot, sorry for the naiveness..
My DIY car is a 1994 (mexican model) VW Bug. I have a 72v brushed PM DC motor, a Kelly KDZ72401 controller, and the current source of my sorrow, a 100 AH 76.8v battery pack made with 120 20 AH 3.2v cells arranged as 5p25s.
Honestly, I didn't know what I was doing (still trying to figure out) when I bought these as a kit from some online seller. I finally put it together for a first discharge run, after which I took the battery apart for bottom balancing.
On this first run yesterday, I took the car out for what ended up being a very short (7 mile) drive, with the factory charge. All batteries were 3.2x or 3.19v when I started. The thing ran fine for 5 miles or so, but once it hit the 70v it declined pretty fast and I had the controller programmed to stop at 60v.
While using it, i did get up to 50 mph for a short period of time, then stayed for a minute or so @ 40 mph and most of the driving was under that. The AMP meter was briefly, for a second at a time or so above 100 amps, and while cruising between 50 - 90 amps.
When I took the battery pack apart, i tested every battery, none seem dead, but a good bunch look swollen, these are between 2.40 and 2.43 volts and the other ones are between 2.6 up to 2.9 volts.
At this point I have 2 theories, one of them is hope, the other one is more factual.
1 - the factory charge was not 'good enough', once I bottom balance these and charge them well, the pack will perform as I expected and give me twenty some miles per charge, hopefully more.
2 - I totally don't understand how these batteries are supposed to perform and need to figure it out or I will fry these and the next pack i end up making.
The specs for these batteries are:
NOMINAL/MINIMUM CAPACITY: 20Ah @ 1/3C Discharge
STANDARD DISCHARGE CURRENT: 6.7A (1/3C)
MAX DISCHARGE CURRENT (continuous): 100A (5C)
MAX DISCHARGE CURRENT (<10 Seconds): 160A (8C)
STANDARD CHARGE CURRENT: 6.7A (1/3C)
MAX CHARGE CURRENT (continuous): 100A (5C)
DISCHARGE CUT-OFF VOLTAGE: 2.0
NOMINAL VOLTAGE: 3.2
SUGGESTED MAX CHARGE VOLTAGE: 3.65
CYCLE LIFE AT 100A (80%): 500
CYCLE LIFE AT STANDARD (80%): 4000
SELF DISCHARGE RATE (30 days): 4-6%
INTERNAL RESISTANCE/IMPEDANCE (milliohms): 2
ENERGY TYPE: 3V-3.2V-3.65V, 20Ah EV, Lithium, LiFePO4, LFP Aluminum Shell Battery
Obviously I don't understand how the AH and C work. In my simple mind, if I made a 100 AH pack, i could get 100 amps for an hour, I don't understand why each of the cells is 20Ah @ 1/3C.
Any help figuring out what happened and will happen is greatly appreciated. Right now I know I paid too much for these batteries, and I'm unsure if they are well suited for this small VW conversion, though the supplier claimed these were great.
Thanks a lot, sorry for the naiveness..
