Battery Amp limit

Solderbro

Solderbro

1 mW
Joined
Dec 10, 2019
Messages
12
Hello there,

my Misterride 7000 did 2 years and 1000km with the icluded silverfish battery (36V / 13Ah). After that the voltage and reach of the battery crumbled down, only 20km rest and it wasn't possible to reach 25km/h as before. After loading a voltage of around 40V did not even occur anymore. So my idea: They placed foul or recycled 18650 cells inside the box.
Bought a new silverfish from Greencell, a 36V / 11Ah, did change the connector and all is well again for cheap 200€ :D

One thing on the manual bothers me, "Use for 250W motors". The misterride has a 4" hub drive limited to 14Ah by the controller. Is this a killer environment for smaller battery packs?

[youtube]https://youtu.be/jFfdvDKfcBw[/youtube]

Solderbro
 
Since you are a solder pro did you open up the old battery and inspect the battery, bms often kill batteries and how often did you use the battery
controller is 14a not ah at 36v thats 504w
the battery will put out whatever the controller asks for unless you have a bms on the battery which will enable the bms to cut off the battery if the controller asks to much from your throttle or pas
 
Solderbro said:
One thing on the manual bothers me, "Use for 250W motors". The misterride has a 4" hub drive limited to 14Ah by the controller. Is this a killer environment for smaller battery packs?
Click to expand...
Need to use the correct electrical current measurement units to calculate whether the battery will happily supply the controller.

We need to know the Amps (A) ratings for the battery and controller, not Amp hours (Ah).

Controller specs should list A and A max. Compare that to the battery A and A max specs.

Derate the advertised battery specs by 20 - 40% because almost all battery sellers lie.

Example: Controller 36V, 10A, 20A max. Battery 36V, 30A max. This will not overstress the battery.
 
Fuse wont literally kill the battery like a bms can and will and does all the time
 
Two year lifespan of batteries is about average, if they get used regularly. Longer can happen, but much depleted performance is normal by the start of the 3rd year. One cell gets weak is all it takes to lose 4v.

Well, the smaller motors can generally handle about 2 or 3x the actual motor rating. So 750w would be the max for the motor, if the spec you are talking about is actually the motor rating.

36v x 20 amps is about 750w. Any battery with 11amp hours of capacity should be able to handle 20 amps peak current. If the cells inside are not complete junk. Chances are you have a 20 amps controller.

The easiest way to judge how your battery is performing under load is to put a voltmeter on it that you can read while you ride. lets say you ride around the block a few times, and now the resting voltage is 38v. Apply full throttle, and see how big the voltage drop is. If its 10v, you have a battery that cannot handle the 20 amps load. 4-6v drop under load while the battery is still fairly full is normal. 8v drop tolerable, but not ideal.

From the sellers POV, if you limited the load to less than 10 amps, he'd be very unlikely to need to honor any warranty claims. If you really want lower sag under load, and more likely long lifetime, get a 20 ah battery next time.
 
dogman dan said:
Two year lifespan of batteries is about average, if they get used regularly.
Click to expand...

Of course but the OP did only 1000 Km in those 2 years. I do that in 2 nice summer weeks. :shock:
I would be very mad if my battery died after 1000 km, that is a very high operating cost.
 
Solderbro said:
my Misterride 7000 did 2 years and 1000km with the icluded silverfish battery (36V / 13Ah). After that the voltage and reach of the battery crumbled down, only 20km rest and it wasn't possible to reach 25km/h as before. After loading a voltage of around 40V did not even occur anymore. So my idea: They placed foul or recycled 18650 cells inside the box.
Click to expand...

If you kept it charged up to 4.2V/cell all the time, that would be enough to knacker your battery in 2 years.
 
Solderbro said:
After loading a voltage of around 40V did not even occur anymore. So my idea: They placed foul or recycled 18650 cells inside the box.
Click to expand...

Since that is a 10S pack if its not 42v its not fully charged, even if it has recycled cells. If its 40v then possibly one or more of the bricks fell out of balance from neglect. Those BMS only top balance and it requires to be left on the charger several hours after the charger light turns green.

Common practice is to balance charge once a month.

If the voltage drops below 42v 10 minutes after unplugging the charger then its not fully charged, even if the charger light was green.

Now that you have a new battery you can experiment with the old one and leave it on the charger for 23 hrs and then test it, or you can open it up and see whats going on.
 
A lot of it is how you maintained and charged it and at what voltage you've kept your battery at ?. How hard you've used it ? Do you run it down to it cuts out ? Please answer all three.
Give us the voltage of your charger and also give us the voltage of your battery.
 
Hi Solderbro. Two numbers would be useful on the old battery, if you really wanted to satisfy your fixing things passion,

1, Voltage after it's been fully charged.
2, Voltage when your bike stops running after 20 km,

If it's unbalanced, the second number will be much higher than the usual cutoff voltage for a 36V pack. That would be 30 - 33 volts.

And given that very few inexpensive batteries are capable of rebalance, that's about all you can do without going inside.
 
Okay,
the battery was put on the charger every 3 weeks if the display was on the last dot of the 5 dot bar. Few times i measured this with around 40V for full. The battery was never driven down to voltage cutoff and used the whole year. The hardest load would be a start on PAS5 what i had only tested 2 times, cause you need to pedal to it.

This is the controller MR700-Controller.jpg what have an amp limit to fit EU regulations.

999zip999 said:
A lot of it is how you maintained and charged it and at what voltage you've kept your battery at ?. How hard you've used it ? Do you run it down to it cuts out ? Please answer all three.
Give us the voltage of your charger and also give us the voltage of your battery.
Click to expand...
 
Solderbro said:
One thing on the manual bothers me, "Use for 250W motors". The misterride has a 4" hub drive limited to 14Ah by the controller. Is this a killer environment for smaller battery packs?
Click to expand...

You already bought the pack and it works, so just enjoy riding it until it doesn't work anymore. Based on your riding history, it's not as though you're going to wear it out, so just pay attention to maintaining it and keeping it at a storage charge level when you're not riding it much.

The best lesson is to do your research before you buy things, and you get what you pay for. I noticed all of the batteries listed on that Greencell site mention the 250W limit, so 7A @36V from their 15Ah pack is less than 1/2C, so if their description is right, then it would mean pretty crappy cells (but I doubt their descriptions are right, so could be OK).
 
And always take your measurements yourself with known good instruments.

Relying on makers' blinky lights can be fraught
 
You must log in or register to reply here.
Back
Top