699 Views 2 Replies 2 Participants Last post by  MrScooter93
Hello, I threw together a diy electric bike kit (48v) with a gel lead acid pack. I have a voltmeter that I can change to show either percentage or voltage. I know a fully charged pack is ~53.4 volts with no load and 42 volts no load should be completely discharged but under load fully charged it wobbles around 50v and goes as far as ~40v under high load when it about to give up but with 40v under load it shows ~48 volts with no load and that's about 60% if you switch the gauge to display percentage.

My question: should I calculate my state of charge under load (driving) or should I do it under no load? I guess I can run it down to 42v with low amp draw. but it doesn't wanna give the 22amp my controller wants ands drops below 40v so I guess 47-48v no load = empty?( atleast empty enough to not be able to give the power to the wheels)

Update: just did a real world test until it was basically empty. It reads 38.9v at high load up a hill(dangerously low?) the controller cuts the power from time to time at this point. It reads 50.3 with no load. Why the huge voltage drop?
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#### rmay635703

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Hello, I threw together a diy electric bike

Update: just did a real world test until it was basically empty. It reads 38.9v at high load up a hill(dangerously low?) the controller cuts the power from time to time at this point. It reads 50.3 with no load. Why the huge voltage drop?
Why Peukert.

It sounds like you have too small of a pack.

Lead is quite saggy, at high amp draws its capacity is greatly reduced if you draw enough amps to pull its voltage too low it wears out faster.

Better off to consider either another chemistry, a larger capacity pack or an AGM pack.

#### MrScooter93

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Yeah that explains it! I still get around 12 miles on it before the voltage drops appears so I will cruise around til the pack dies then I'll experiment with modern chemistries.

Yeah peukerts is a bitch haha

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