Help! Replacement 36v battery for a Giant Suede

[sjpt]

Does that mean that the battery voltage reading after use directly relates to how much is left in it ?
Example if I did 21 miles from full (42), and it now shows 35, is that 7/10 of the available power used ?
42-35 =7. That would mean I could get 30 miles in total from one charge .

There is a relationship between voltage and remaining capacity that is fairly linear over quite a bit of the range. Typical sample graph below; you may be able to find one for the cells in your particular battery.
Also, that is capacity in amp hours. 1 amp at 42v is 42w, but only 32w at 32v.

The LEDs are probably linear with respect to the voltage, but with full led being below 40v, and empty led being above 30v.

Also, when the motor is working hard the voltage sags because of internal battery resistance. LEDs often drop one or two bars under heavy load. If the battery is showing almost empty when you are tired near the end of a ride and you hit a hill it is quite likely the voltage will drop enough that the BMS cuts out and you are without assistance at a critical time.

Only experience will tell you how your particular battery/motor/LED setup behaves.

Calculating the Battery Runtime - Battery University

Examine battery losses when estimating energy reserve

batteryuniversity.com

 

[mikeconnect]

Not necessarily, the system is not that linear, each LED can mean a different number of miles. Remember that as the voltage falls, so does the performance.

And of course as a power assist system, much depends on what you are putting in. If after the 21 miles you are tiring so putting in less, the combination could mean even less remaining.

These LED meters are only a rough guide at best, not mathematically linear.
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Thanks but no no I'm ignoring the LEDs which are on the throttle control anyway not on the battery I'm referring to to the voltage Reading from the battery contactsv using multimeter would have been 42v when full currently at 35v after 21 miles usage hence the calculation in my post

 

[mikeconnect]

There is a relationship between voltage and remaining capacity that is fairly linear over quite a bit of the range. Typical sample graph below; you may be able to find one for the cells in your particular battery.
Also, that is capacity in amp hours. 1 amp at 42v is 42w, but only 32w at 32v.

The LEDs are probably linear with respect to the voltage, but with full led being below 40v, and empty led being above 30v.

Also, when the motor is working hard the voltage sags because of internal battery resistance. LEDs often drop one or two bars under heavy load. If the battery is showing almost empty when you are tired near the end of a ride and you hit a hill it is quite likely the voltage will drop enough that the BMS cuts out and you are without assistance at a critical time.

Only experience will tell you how your particular battery/motor/LED setup behaves.

Calculating the Battery Runtime - Battery University

Examine battery losses when estimating energy reserve

batteryuniversity.com

View attachment 42123

Thanks the LEDs are on the throttle not on the battery thinking they're not reliable so I'm ignoring them that's why I'm checking the voltage it's a new battery so we'll see what happens I've only been testing it after work so so I've done 10 miles 7miles and 4 miles separate days. Planning to be out tomorrow morning to see how much it's got left but I'm not sure if it's good to run it till it stops??

 

[sjpt]

Thanks the LEDs are on the throttle not on the battery thinking they're not reliable so I'm ignoring them that's why I'm checking the voltage it's a new battery so we'll see what happens I've only been testing it after work so so I've done 10 miles 7miles and 4 miles separate days. Planning to be out tomorrow morning to see how much it's got left but I'm not sure if it's good to run it till it stops??

It certainly isn't good to run till it stops regularly, but I don't think doing it occasionally matters. One of the jobs of the BMS is to ensure it cuts out before significant damage. Do recharge asap after it runs out; very bad to leave very low for any length of time.

 

[mikeconnect]

It certainly isn't good to run till it stops regularly, but I don't think doing it occasionally matters. One of the jobs of the BMS is to ensure it cuts out before significant damage. Do recharge asap after it runs out; very bad to leave very low for any length of time.

Yes I'd never do it regularly. But as a one off want to see how long it lasted after that I'll keep topping up just as and when and I'm sticking to 2-amp charger as I believe anything higher for a 10ah may shorten life

 

[flecc]

Thanks but no no I'm ignoring the LEDs which are on the throttle control anyway not on the battery I'm referring to to the voltage Reading from the battery contactsv using multimeter would have been 42v when full currently at 35v after 21 miles usage hence the calculation in my post

It's the same thing so long as you observe the reading when not using power, the LEDs are just a colour display of battery voltage, non linear so not indicating fixed ranges per LED.
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[mikeconnect]

It's the same thing so long as you observe the reading when not using power, the LEDs are just a colour display of battery voltage, non linear so not indicating fixed ranges per LED.
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Yes. so far I've done 10 miles on green further 6 miles on amber and so far 9 miles on red with juice still in battery. Current voltage 34.5 after 25 miles. Maybe break 30 miles

 

[flecc]

Yes. so far I've done 10 miles on green further 6 miles on amber and so far 9 miles on red with juice still in battery. Current voltage 34.5 after 25 miles. Maybe break 30 miles

That's good, you now know you are safe for a bit over 25 miles in similar terrain and weather.

But of course they are two more variables. A more hilly route and you probably wouldn't get so far. And if the weather is markedly colder, battery efficiency drops so once again less miles achievable.
.

 

[mikeconnect]

That's good, you now know you are safe for a bit over 25 miles in similar terrain and weather.

But of course they are two more variables. A more hilly route and you probably wouldn't get so far. And if the weather is markedly colder, battery efficiency drops so once again less miles achievable.
.

At my age and condition

That's good, you now know you are safe for a bit over 25 miles in similar terrain and weather.

But of course they are two more variables. A more hilly route and you probably wouldn't get so far. And if the weather is markedly colder, battery efficiency drops so once again less miles achievable.
.

At my age and condition there'll be no variables . My sense of adventure is down to slight inclines and max 10 miles each way to visit my daughter. So I'm pleased that it indicates 30 range . Well just see how it performs over time And many recharges. Although I don't see me charging more than twice a week . They say it'll only drop to 80% after 600 charges but I'll believe that when I see it. Let you know in 6 years time. It's initial performance is encouraging for an Aerdu battery. We'll see how it goes over time

 

[mikeconnect]

Does charging slow down towards end of charging ? It's nearly full 39.5 fir 36v battery but it's supposed to be About 5 hours (2a for 10ah) but still not green on charger after 6.5 hours

 

[vfr400]

Does charging slow down towards end of charging ? It's nearly full 39.5 fir 36v battery but it's supposed to be About 5 hours (2a for 10ah) but still not green on charger after 6.5 hours

A new battery is normally half-charged (37V) when you get it, so it should take about 3 hours. 6.5 hours doesn't sound good. A charger can slow down when it gets nearly full, like around 41V, but not at 39.5v.

 

[Nealh]

We did say the aerdu battery not only sounded very dodgy but is highly likely so, I hope you have a fire proof box to keep it in just in case.

The cells are likely recycled old crap cells or just cheapo China ones, as you said Mike time will tell.

The new cell cost alone for my new battery build is over £144 and the cells are top notch.

 

[mikeconnect]

We did say the aerdu battery not only sounded very dodgy but is highly likely so, I hope you have a fire proof box to keep it in just in case.

The cells are likely recycled old crap cells or just cheapo China ones, as you said Mike time will tell.

The new cell cost alone for my new battery build is over £144 and the cells are top notch.

Assume you diy build

 

[mikeconnect]

A new battery is normally half-charged (37V) when you get it, so it should take about 3 hours. 6.5 hours doesn't sound good. A charger can slow down when it gets nearly full, like around 41V, but not at 39.5v.

Well I took it off charge to go fir ride so maybe my start time was wrong . I'll see next charge

 

[cyclebuddy]

Does charging slow down towards end of charging ? It's nearly full 39.5 fir 36v battery but it's supposed to be About 5 hours (2a for 10ah) but still not green on charger after 6.5 hours

Chargers work CC/CV - that is Constant Current, then Constant Voltage. A 2-amp charger will charge at 2 amps until maximum voltage is reached. The charger then holds that voltage steady and reduces current progressively until the battery is full. When the battery is at peak voltage and the current has steadily reduced to say 200mA, the battery is full and the charger stops. It's the latter CV stage that's adding time because the charger is working at a constantly reducing current.

Don't forget that the battery itself is also balancing cells in the very final stages of charging by bleeding those cells that peak early, which again adds more time. So it's not a linear process: A 10 amp battery can take a lot longer than 10A/2A = 5hrs, longer still if the cells need balancing.

 

[mikeconnect]

Chargers work CC/CV - that is Constant Current, then Constant Voltage. A 2-amp charger will charge at 2 amps until maximum voltage is reached. The charger then holds that voltage steady and reduces current progressively until the battery is full. When the battery is at peak voltage and the current has steadily reduced to say 200mA, the battery is full and the charger stops. It's the latter CV stage that's adding time because the charger is working at a constantly reducing current.

Don't forget that the battery itself is also balancing cells in the very final stages of charging by bleeding those cells that peak early, which again adds more time. So it's not a linear process: A 10 amp battery can take a lot longer than 10A/2A = 5hrs, longer still if the cells need balancing.

All seems ok I ran it down to 35v yesterday and it charged about 3 hrs. I think my timing was out on previous charge

 

[mikeconnect]

New uk supplied Aerdu battery update ... very early days of course but at least it's not doing what some Ali express purchased Aerdus did which is die after 20minutes . So it's holding at 25 to 26 miles range . Only 4 or 5 charges so far so as I said early days.

 

[vfr400]

New uk supplied Aerdu battery update ... very early days of course but at least it's not doing what some Ali express purchased Aerdus did which is die after 20minutes . So it's holding at 25 to 26 miles range . Only 4 or 5 charges so far so as I said early days.

It'll probably be OK now. How much did you pay for it?

 

[mikeconnect]

It'll probably be OK now. How much did you pay for it?

185. eBay seller battery.pack. Wellingborough. And he lets you collect if you're near . Dodgy suppliers wouldn't allow that