Reduced Range

[adamsavage79]

I've noticed that lately the bike has been acting quite strange. I find despite the motor using 1/2 the power it was normally using, I'm not getting the same range as I was when I was pushing the motor harder. I do the exact same route to and from work, and I have only 2 - 3 stop and go at the most. Going to work I was typically pulling 1200-1300 watts, and coming back I was using 500-700 watts while riding.

I find the battery is going down 1 bar to 50v roughly 2km sooner than it was before hand, and I'm using about 500-700 watts now going to and coming back from work, going the same route. The only difference is the outside temp is cooler now. So I'm using less power, and yet I'm still getting less range.


My question is, would the cooler temps be playing a role in this ? I've always assumed you would need below freezing temps for any noticable change in range to happen. It has been any where from 4 degree's celsius to 15-16 celsius.

Here are the specs of the bike and the battery.

https://www.teslica.com/purity-mountain-ebike-m1h.html#proTabPanelSpecs

 

[amberwolf]

I keep circling back to the quality of the cells. I believe they are cheap China cells, and this would explain why they are able to sell me a 20ah pack for $589 USD or $750 CDN. The owner swears up and down that they are on par with the brand names, and I want to believe him. However, I've never heard of a battery being highly senstive to temps below 15 Degree's Celsius.

There is literally no way to know anything about the cells without disassembling the pack and testing them methodically alongside the "brand name" cells you wish to compare them to, using the same methods and tests. Even if you opened it and found they had labels, you can't know that the cells under the labels are really those cells--cheap cells do get rewrapped as brand name cells.

Since that's not an option, there is no reason to worry about what cells they are--just assume they aren't as good as you wish they were.

Since:
--you can't open the battery to do any testing, and
--you (presumably, since you haven't said you are) aren't testing by charging overnight as much as possible and retesting the ride range/etc, and
--you're not able to get them to replace the battery under their warranty,
your two options for the problem you are having is to either live with it, or to buy a new battery from a different place that does use known-good known-brand known-specification well-matched cells, and provides the information about the pack you want to know, and does honor their warranties.

If you're willing to charge overnight as much as possible and retesting the ride range/etc., then you can find out if the pack is simply unbalanced, which is the most likely cause of the problem you're seeing. (it's a very very very common problem)

If you're not willing to do that, or else it doesn't seem to change anything, then if you're willing to open the pack and test the cells, at least to test the cell group voltages before and after a charge, and before and after a ride, you can then tell if there are cell groups that are unbalanced.

There are other problems it could be, such as temperature-induced capacity or resistance changes, etc., but you'd have to test in a repeatable controlled way to find out for sure.

Without testing, then it's all speculation, and it isn't going to fix anything for you.

 

[adamsavage79]

I can definitely start leaving it on charger overnight. They are a nice company but they seem to have picked up bad info on batteries. Everything is overcharging with them. I got told the other day that my old pack was being overcharged if the voltage on the charger while charging was higher, vs being off the charger. I was like what ? I've never heard of a E-bike pack get overcharged, let alone a cell phone battery. I don't know this strange tunnel vision on the idea that these packs can be over charged.

As for a new pack, I'm not sure this is an option. The packs are designed to fit inside the frame. You would need to find a BMS that is small enough to fit in a casing that would fit inside the frame.

I do have a battery cover that does seem to help with my range. I found I've been able to reduce my range lose to about 10% - 15%. Basically another km and half ? Need further testing. With BOTH packs though, I can now go pretty far once the weather warms up. That won't be till March at the earliest though.

Here is the link for the Battery/frame cover:

https://www.amazon.ca/gp/product/B09K7NWX19

Below is what the smallest Battery Pack looks like.

 

[adamsavage79]

I got a email back from the vendor. I'm still not convinced you can overcharge the battery. I have two different people on here telling me two very different things. So at this point, I have no idea if overnight charging is bad or good.

This is what they had to say when I asked about overcharging.

Yes, the BMS keeps on measuring each battery's voltage, and if it starts to exceed the allowed limits, it will shut off the charging cycle. but see the problem in what I said? it shuts off when each cell starts exceeding the recommended limits. A 3.7 V 18650 Cell is supposed to only be charged to 4.2 V, the more voltage you put in a battery, the more electrolytes that will travel from your positive terminal (Cathode) to negative terminals (Anode), having electrolytes rest on the anode will cause oxidation and will lead to an effect called plating, plating creates a layer of resistance on the anode and will therefore reduce its ability to receive Lithium from the cathode, the more this happens, the faster your fully charged battery will last. Here is a reference link, followed by a simplified version of it:

https://www.nasa.gov/sites/default/files/atoms/files/1-lithium_plating_azimmerman.pdf

https://www.upsbatterycenter.com/blog/lithium-plating/#:~:text=Lithium%20plating%20is%20the%20formation%20of%20metallic%20lithium,cause%20these%20rechargeable%20batteries%20to%20malfunction%20over%20time.

Your BMS will stop you from reaching intense voltages, but it will still get slightly higher than desired Now, if you would like to do a test to see if the battery does indeed overcharge, you can leave the battery plugged in overnight and see if the charge just before you unplug it in the morning would be higher than 4.2V, you have 13 rows built in series, therefore the battery charge should not exceed 54.6 V (4.2 V * 13 cells = 54.6 V).

Note that plating starts at 4.1 V per cell, and happens in higher magnitudes at the higher voltages.

Remember that last time you can in I told you that you can make your battery last longer by not fully charging it? This is for the same reason, by not charging your cells above 4.10 V, (4.1 V cell charge *13 series of cells = 53.3 V battery charge) you will significantly reduce the amount of plating your battery.

Here is a slide by NASA to admire, Battery B is charged to full potential while battery A is not to exceed 4.1 V. The x-axis is the number of charging cycles, and the y-axis is the resistance, note that more resistance = less range per cycle.

 

[99t4]

I got a email back from the vendor. I'm still not convinced you can overcharge the battery. I have two different people on here telling me two very different things. So at this point, I have no idea if overnight charging is bad or good.

Depends what you mean by "overcharging."

Do you mean charging to an overvoltage situation, exceeding the mfr's max. voltage spec. (more than 4.2V per cell)?

Or do you mean overcharging as in charging too often, or leaving the battery on the charger for too long?

Depending on the health and quality of the charger and BMS they may or may not be the same thing.

This may help clear up some of your confusion:

1. Faulty or out of adjustment charger or faulty BMS may charge the cells beyond the mfr max. voltage limit (4.2V). This will damage the cells, no question.

2. The cells themselves do not like sitting at full capacity (4.2V) for extended periods. Can manifest as shortened useable lifetime, less capacity, less endurance. Many here fully charge only when they know they will be using the battery immediately upon reaching full charge. Otherwise leave the battery at ~50% charge. Others charge up to max. ~4.1V, to extend the battery lifetime.

3. A good quality battery, used intelligently, should not require frequent balance sessions. Depends on the cell quality, quality of materials, assembly, ratio of battery capacity to usage scenarios, whether the battery is run to the last drop, etc. For a good quality battery, sized appropriately to the usage demand, maybe 1-4 balance sessions per year? So even though the battery is sitting at max. charge while it is balancing overnight, in the overall scheme of things that infrequency is not that serious.

 

[adamsavage79]

I'm told Overcharging is when the battery is @ 54.8v fully charged vs 54.6v. Very slight difference. As for leaving it on the charger, I would say the longest is 12 hours ? I typically don't have it on that long and I've gotten better at remembering the pack is on the charger.

That being said, I'm debating on getting a better charger. It's called a Satiator ? I can set it to only charge the pack to 80%, thus extending the life span. If I don't need the entire capacity of the pack all the time, then this makes sense. However, it's not cheap. I need to read up more on it, and see what the life span of the charger is.

https://ebikes.ca/product-info/grin-products/cycle-satiator.html#WheretoOrder