Temporary power loss at low speed under load - question.

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Zarathustra1984   100 µW

100 µW
Posts: 9
Joined: Jul 03 2020 3:32pm

Temporary power loss at low speed under load - question.

Post by Zarathustra1984 » Aug 01 2020 10:20am

I previously had an issue with ignorantly attempting to use a 10AH battery with a 1500w motor :lol: - and I switched up to a 20AH 48V battery. With the 22A continuous/ 45A max controller not tuned down via the LCD3 it pulls ~2k watts which is ridiculous. Sag is about 2.2V at that power level and with it tuned down to ~1400W I'm getting about 1.8V sag which is just under 4% - which I assume is "safe". Under long sprints doing 30mph the battery is not even warm to the touch.

When gunning the throttle from a dead stop when load is the greatest, it will accelerate 5 ft, temporarily lose power (LCD stays on), then resume acceleration. I can only assume the battery is under too much load when this happens, but I don't understand which component would be initiating this protection, what the mechanic is, and how much damage this is doing to the battery. Of course, I now roll on the throttle a bit before opening it up to avoid it, but thought I'd ask you fine folk about your thoughts on this "feature" and if I can get away gunning it from a stop - and have no repercussions.

Much thanks!

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E-HP   100 kW

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Joined: Nov 01 2018 9:20pm

Re: Temporary power loss at low speed under load - question.

Post by E-HP » Aug 01 2020 11:30am

Zarathustra1984 wrote:
Aug 01 2020 10:20am
When gunning the throttle from a dead stop when load is the greatest, it will accelerate 5 ft, temporarily lose power (LCD stays on), then resume acceleration.
This likely rules out the battery BMS, since if that trips, you usually have to shut off/disconnect the battery to reset it. That said, you didn't mention the specs on the battery BMS.

Since the LCD stayed on, I'm guessing it's a current limit. How are you "tuning down" to 1400W (C5?)? The motor will pull more than that from a stop, and potentially way more if you're are on an incline. The LCD3 tops out at 1999, but I'm guessing you're pulling more in bursts, based on what I've seen moving from the LCD3 to the Cycle Analyst and seeing the actual peak power.

If you are concerned about the battery, and want to use the controller to protect it, set the current limit of the controller equal to the continuous current rating of your BMS. You could also set it to the peak current of the BMS so you have access to the peak power, but then you need to limit your throttle hand from regularly abusing your battery.

Zarathustra1984   100 µW

100 µW
Posts: 9
Joined: Jul 03 2020 3:32pm

Re: Temporary power loss at low speed under load - question.

Post by Zarathustra1984 » Aug 01 2020 6:54pm

They say it's a 50A BMS https://www.amazon.com/gp/product/B0822 ... UTF8&psc=1

Yes, I have the LCD3 'C5' setting tuned to 3. When it was at 10 I noticed the screen would display up to 1985ish watts very temporarily then 'normalize' at about 1500 until I got to speed. With it on 3 it appeared to limit the burst to about 1400. Maybe I didn't monitor it enough? I assumed that the LCD3 C5 setting was limiting the controller current by having it on 3? Really have no idea what that cutout is or why and would like to be able to not feather the throttle upon takeoff if we can get this figured out and it be safe.

Another question if anyone would be willing to awnser - I rode it 20 miles tonight on the throttle starting at 52v and at the end of the trip I was down to 47v with sag at 45.6. How low would be acceptable to end my trip for sag?

Thanks :o

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