Acceptable battery performance?

Ok, I am into this full force now, and am considering another battery already for various reasons (ebike trip with the wife coming up and her battery is in the ocean somewhere still, spare, occasional longer range for my bike, etc) and would like some advice. I am trying to determine if I should buy another of the exact same battery so I can use it in pannier packs occasionally.

My current pack was $388 to my door from China and here are the specs:



According to Dogman's formula I found in another post and my recent logs, I don't think I am getting 20AH of juice out of this thing.

I am averaging 27Wh/mile real world around here with winds and hills and such.
48v x 20Ah = 960 Wh
960/27 = 35.55 miles theoretical range

I rode my bike the other day on this route to test range: https://goo.gl/TsBemP 26.2 miles at 15.72 avg mph (100 minutes)

I don't have my Wh figure for the ride because my watt meter faded away and lost my stats

I was taking it semi-easy on the battery by pedaling and keeping it under 20mph for most of the time. There were LOTS of people on Cherry Creek trail the whole way so lots of slowing and accelerating involved. Toward the end I was close to empty, so I upped my speed for the last couple of miles as I wanted to hit LVC. My LCD showed battery empty for a mile or two and it turned out to be correct and I hit LVC as I turned into the neighborhood and had to peddle 100% the last 3/4 of a mile or so.

So either my consumption was much higher on this particular ride, which I doubt since I usually am hauling along much faster at 27 Wh/mile, or this battery is not a true 20AH, right?

Next time, keep a closer eye on that wattmeter when you see your other indicator showing the end is coming. But your wh/mi won't have changed that much at the end. FWIW, that's one feature we love about the Cycleanalayst, it keeps the data even when your bms trips, or the bike gets unplugged to swap batteries.

27x 26.2 is 707 wh. About 13.6 ah. Possible you tripped the bms early, because of one cell out of balance. Slower at the end will milk more out of it, perhaps to 15 ah.

In general, at 388 shipped for that much capacity, it would be sort of typical to see it only deliver 15 ah in reality. At that price, they simply cannot be using top quality cells. V power hong kong? They were at one time notorious for 5 ah under delivering capacity. But, still a great price for 48v 15 ah! You might be able to balance the pack better, and still get 19 ah out of it. My allcell tends to do that. 13 ah, but I have to push it to balance better to get it. Typical charge yields more like 11.5 ah.

Depending on your charger voltage, it's possible you don't get a full charge. Or, just need to leave it on the charger for a week or so to fully balance.

Thanks for the reply!

Yes, I think its's a Vpower type. Heres a pic



Yeah, I am probably not too far away from ordering a Cycle Analyst, as I just ordered some compatible controllers last week lol. Told you, I have the bug! In the meantime, I may supply external battery power to my meter and run another test.

As far as a cell out of balance, it is possible, but I leave my 2 amp charger plugged in pretty much always since I ride almost every day. This charger tops out at 54.3v and stays there and watt meter indicates no current flow. I have never seen it turn back to red after finishing, or any more power be consumed after a charge via the meter. Honestly, I am reluctant to cut into the shrink wrap and pull out the bms to test cells, but it seems I may be headed in that direction to make an informed decision here.

External power meter supply is almost necessity when testing capacity using hobby power meter. I also use an old toaster oven (wire directly to heater element) usually good for 5-6A load somewhere around 50-60VDC. Good enough capacity test instead of attempting to coordinate a ride without running out too soon and/or winding up too far away from home.

But yeah, get a CA installed and you will immediately have all consumption info and much more readily available.

I am reluctant to cut into the shrink wrap and pull out the bms to test cells, but it seems I may be headed in that direction to make an informed decision here.

Dont do it,Yet.your battery seems pretty good for vpower,im sure you will get a few days where you dont need to ride.then you can let the cells level over a few day charge cycle as per Dogman suggests.

you have to measure the voltage on the cells before discharging the pack into the dummy load like ykick uses. i use electric oil radiators like the Pelonius and a radiant heater.

your wattmeter could be off by 5%.

but you have to charge each cell to 3.65V to get the pack fully charged before claiming that the pack is no good.

measure the cell voltages on the BMS where the sense wire is plugged in while the battery is charging. watch for the cell that goes to 3.9V and cuts off the charge at HVC.

when you can finally get it fully charged then all of the cells will have been pushed up to 3.65V and you have to verify that before beginning the discharge into the dummy load.

No, it's not a V power HK pack. Unless there is one hidden under that shrink.

54.3 volts seems low for a 16 cell lifepo4. Not fully charged, if it's 16 cells. Should go closer to 58v for that. This could mean the bms never really gets into balancing mode. It could be just that simple, undercharging and not balancing.

Once you do open it, you can look at the bms to count the cells. Likely its on the end where the wires come out, so you can cut away the shrink on just that end

Assuming you can't send it back to china, Nothing wrong with cutting the shrink off to find the bms. Then if you need a better charger to get to 58v, that's fairly easy to do.

Hmm, I never gave a second thought to voltage. That is the stock 2 amp charger that stops at 54ish volts and goes green. I also have a 6 amp charger from china that I need to watch more closely, only used it once to test, anbd come to think of it, it was cycling red then green at end of charge but I forget the final voltage. Maybe it goes higher... I also have multiple mean wells that are adjustable, so I will pump it up to 58 and see.

I also use an old toaster oven (wire directly to heater element) usually good for 5-6A

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Ykick, you have shown me the way...you provide a battery load for testing, using easily found free junk, and I can make a BLT (with extra B) sandwich at the same time.

spinningmagnets said:

I also use an old toaster oven (wire directly to heater element) usually good for 5-6A

Click to expand...

Ykick, you have shown me the way...you provide a battery load for testing, using easily found free junk, and I can make a BLT (with extra B) sandwich at the same time.

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Hahaha... 60-67VDC directly on those heater elements = just about perfect for BLT or reheating Pizza!

Lighting has always been a common test load but don't forget space heaters or anything with heating element can make for a handy resistive load too.

That battery sure looks like it says v-power on the label.
otherDoc

dogman dan said:

54.3 volts seems low for a 16 cell lifepo4. Not fully charged, if it's 16 cells. Should go closer to 58v for that. This could mean the bms never really gets into balancing mode. It could be just that simple, undercharging and not balancing.

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My chart above says Charge Cutoff Voltage 54.6. Shouldn't that be the target voltage to kick into BMS balancing mode?

Hey Ykick, that toaster trick is awesome! I am having issue in another thread with my mean well chargers kicking into protect mode, and verified they can provide current normally with your trick. I just touched the AC plug to the 48v terminals on the power supply, and I could hear the power supplies kick into gear, and the heater elements got hot pretty quickly. Thanks!

striider said:

I also have a 6 amp charger from china that I need to watch more closely, only used it once to test, anbd come to think of it, it was cycling red then green at end of charge but I forget the final voltage.

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That cycling usually means the BMS in the pack is balancing the cells. If it doesn't do that, it could easily be causing problems with not getting full capacity, because the pack isn't being fully charged.


But if the pack is out of balance that badly without being deeply discharged, it could also be a pack problem

Unless you open it enough to access the balance connector on the BMS and measure individual cell groups as has been advised, there's no way to know for sure.

striider said:

Hmm, I never gave a second thought to voltage. That is the stock 2 amp charger that stops at 54ish volts and goes green. I also have a 6 amp charger from china that I need to watch more closely, only used it once to test, anbd come to think of it, it was cycling red then green at end of charge but I forget the final voltage. Maybe it goes higher... I also have multiple mean wells that are adjustable, so I will pump it up to 58 and see.

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According to the specs you initially posted the battery is one of the LIMN variety and the 54.6V charge voltage is correct. Do NOT use a higher voltage charger unless you know for a fact this is not correct.

Also I have 3 wattmeters, A Watts-Up, A Turnigy and one of those blue units. The blue one indicates WH up to 8% BELOW the other 2.

-R

I shoulda read the spec sheet better. 13s pack, charge to 54.6v. It's not a v power lifepo4.

However, I found my 13s pack would not balance at 54.6v, but would at 55v. So that could be part of the problem. I only lose about 2 ah from mine though. But way out of whack could still cost a lot of capacity, if one high cell stops charging early.