why did battery cut out?

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PRW   10 kW

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why did battery cut out?

Post by PRW » Apr 04 2021 10:22pm

went for a ride over the weekend. The battery is a 18S6P 30Q. Battery was fully charged at around 74v at the start.

The ride was very hilly, and I wasn't pedaling along (torn achilles at the moment). Regen also wasn't working - I am normally very reliant on that for braking and some regen.

At about 36km, battery died. Voltage was 63v, amp hours 15.3. LVC is set at 55.8 - so I wasn't close. When I switched the bike back on, voltage was shown as 13.4v (recharging at home, it shows the 63v.

Why don't I get the use of the 55.8v and 18 ah?

thanks

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markz   100 GW

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Re: why did battery cut out?

Post by markz » Apr 04 2021 11:35pm

3mAh x 6 = 18Ah
18S x 4.2V = MAX 75.6V
18S x 3.6V = NOMINAL 64.8V x 18Ah = 1164Wh divided by / 25-30Wh/km = 42km (27.5Wh/km)
18S x 3.3V = MIN 59.4V
or 18V x 3.2V = MIN 57.6V
Yours is 3.1V for your 55.8V lvc. Use nominal for range.

Seems about right even when you have hills, and not pedalling, wind, total weight including your weight, and your cargo.
Trace your route with googlemaps, above the graph pull down menu - https://ebikes.ca/tools/trip-simulator.html

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Re: why did battery cut out?

Post by PRW » Apr 05 2021 12:04am

very nice simulator - unfortunately I cannot get Google maps to recognise the off road trail.
https://www.google.com/maps/dir/Ongarue ... 1?hl=en-US

on road, it shows a use of only 8ah for the trip - but that doesn't take any of the hills off road into account.

edit - managed to get Google maps to show the trail... https://www.google.com/maps/dir/Timber+ ... 1?hl=en-US

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Re: why did battery cut out?

Post by goatman » Apr 05 2021 12:20am

i do 36km all the time without pedalling on my trike, high speeds, hilly and the ca3 shows 12.6ah
if you look at the 30Q test in my signature the capacity from 4.2v to 3.2v is around 2400 mah x 6p=14.4ah
like markz said, sounds about right

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Re: why did battery cut out?

Post by amberwolf » Apr 05 2021 1:10am

PRW wrote:
Apr 04 2021 10:22pm
went for a ride over the weekend. The battery is a 18S6P 30Q. Battery was fully charged at around 74v at the start.

The ride was very hilly, and I wasn't pedaling along (torn achilles at the moment). Regen also wasn't working - I am normally very reliant on that for braking and some regen.

At about 36km, battery died. Voltage was 63v, amp hours 15.3. LVC is set at 55.8 - so I wasn't close. When I switched the bike back on, voltage was shown as 13.4v (recharging at home, it shows the 63v.

Why don't I get the use of the 55.8v and 18 ah?

thanks
THe most likely reason is a weak cell group, that under load dropped below the cell-level LVC of the BMS, so the BMS shut off to protect the pack. Cheap common BMSs generally "recover" from that and allow you to beat the crap out of the weak cell(s) and kill them by repeatedly making them work until they drop like that, but "better" ones will lock out the pack until it is reset by plugging in a charger; that's what yours appears to have done.

If you don't have access to the cells to measure them when this kind of event happens, then you can simply try leaving the pack on the charger all the time when you are not actually using it, for at least several days, and see if it improves. If it does, then one or more of the cell groups has less capacity and/or capability than the others, and is going to require this rebalancing at each recharge to keep it closer to the rest of the groups.

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markz   100 GW

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Re: why did battery cut out?

Post by markz » Apr 05 2021 4:25am

goatman - Yeah but your a toothpick right, say 100 lbs soaking wet :wink:

PRW - There is a trick to mapping your route on that simulator. Right click a start point, right click an end point, then move the route to your desired route by click the line and moving it. If you can do it on Google Maps website, you most likely can do it in the simulator as well. And if you can not, then you better find a similar route somewhere else and map it.
- Like what amberwolf said, charge it up completely, leave it on the charger a long time because balancing doesnt occur until the last little bit.
Remember that any little slope can have a drastic impact on range, even a strong headwind, also if you go full throttle all the time then your using up a lot of wh/km.
goatman wrote:
Apr 05 2021 12:20am
i do 36km all the time without pedalling on my trike, high speeds, hilly and the ca3 shows 12.6ah
if you look at the 30Q test in my signature the capacity from 4.2v to 3.2v is around 2400 mah x 6p=14.4ah
like markz said, sounds about right

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neptronix   100 GW

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Re: why did battery cut out?

Post by neptronix » Apr 05 2021 9:08am

What's the peak amps of your controller? you're very likely hitting LVC from voltage sag.. the 30Q isn't the strongest cell. Like, a realistic continuous current for your pack would be 36A ( 2C ) or less.
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PRW   10 kW

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Re: why did battery cut out?

Post by PRW » Apr 05 2021 4:40pm

amberwolf wrote:
Apr 05 2021 1:10am
PRW wrote:
Apr 04 2021 10:22pm
went for a ride over the weekend. The battery is a 18S6P 30Q. Battery was fully charged at around 74v at the start.

The ride was very hilly, and I wasn't pedaling along (torn achilles at the moment). Regen also wasn't working - I am normally very reliant on that for braking and some regen.

At about 36km, battery died. Voltage was 63v, amp hours 15.3. LVC is set at 55.8 - so I wasn't close. When I switched the bike back on, voltage was shown as 13.4v (recharging at home, it shows the 63v.

Why don't I get the use of the 55.8v and 18 ah?

thanks
THe most likely reason is a weak cell group, that under load dropped below the cell-level LVC of the BMS, so the BMS shut off to protect the pack. Cheap common BMSs generally "recover" from that and allow you to beat the crap out of the weak cell(s) and kill them by repeatedly making them work until they drop like that, but "better" ones will lock out the pack until it is reset by plugging in a charger; that's what yours appears to have done.

If you don't have access to the cells to measure them when this kind of event happens, then you can simply try leaving the pack on the charger all the time when you are not actually using it, for at least several days, and see if it improves. If it does, then one or more of the cell groups has less capacity and/or capability than the others, and is going to require this rebalancing at each recharge to keep it closer to the rest of the groups.
thanks Amberwolf - I will do so.

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Re: why did battery cut out?

Post by PRW » Apr 05 2021 5:28pm

markz wrote:
Apr 05 2021 4:25am
goatman - Yeah but your a toothpick right, say 100 lbs soaking wet :wink:

PRW - There is a trick to mapping your route on that simulator. Right click a start point, right click an end point, then move the route to your desired route by click the line and moving it. If you can do it on Google Maps website, you most likely can do it in the simulator as well. And if you can not, then you better find a similar route somewhere else and map it.
- Like what amberwolf said, charge it up completely, leave it on the charger a long time because balancing doesnt occur until the last little bit.
Remember that any little slope can have a drastic impact on range, even a strong headwind, also if you go full throttle all the time then your using up a lot of wh/km.
goatman wrote:
Apr 05 2021 12:20am
i do 36km all the time without pedalling on my trike, high speeds, hilly and the ca3 shows 12.6ah
if you look at the 30Q test in my signature the capacity from 4.2v to 3.2v is around 2400 mah x 6p=14.4ah
like markz said, sounds about right
thanks Markz - love these graphics - got it to go on the trail. https://ebikes.ca/tools/trip-simulator. ... &rx=0&rw=0

PRW   10 kW

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Re: why did battery cut out?

Post by PRW » Apr 05 2021 5:37pm

neptronix wrote:
Apr 05 2021 9:08am
What's the peak amps of your controller? you're very likely hitting LVC from voltage sag.. the 30Q isn't the strongest cell. Like, a realistic continuous current for your pack would be 36A ( 2C ) or less.
the controller is 70 amps, the bms 90 amps, CA sets max amps at 65

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