Battery life seems off?

[DeezNeuticles]

Hi everyone! Long time listener, first time caller... I got an account finally to ask this question, please go easy with me I've been riding around on my newly converted hybrid for the last week and the battery life just seems really low, wanted to see what yall think. Did the conversion myself with the help of a diy ebike nerd friend:

Medium size aluminium hybrid/fitness bike frame, 26 lb original bike weight, I weigh 175 and carry 10-20 lb of stuff
TSDZ2B from ecocycles, no throttle, no ebrakes (i'm careful though!), 42T chainring, running OSF, with cooling mod
Bicycle motor works battery 52v10a pocket rocket, it was supposed to be a molicel battery but doesn't say it is on the invoice so, idk?

Riding at 12-20mph, mostly using medium/lower gears, between levels 1-4 of torque assist but mostly at 1 or 2, occasional haul up a hill at 5-7. Mostly on flat/slight incline, occasional hills. I'm in portland, OR.

I'm going from 100% to 30 or 40% in about 15 miles, does that seem normal? I haven't calibrated the battery or torque assist because uhhh I have no idea how and just don't understand the manual.

thanks!

 

[Adrian_]

battery 52v10a pocket rocket

I'll assume that's a typo and you meant 52v10Ah. I did some quick rough calculations, TSDZ2B comes in 500w and 750w versions, I used 500w in my calculations to be safe and what you provided, it does sound about right. 10Ah is really not a lot even if you think about it especially if you're going up to 20mph.

 

[amberwolf]

Medium size aluminium hybrid/fitness bike frame, 26 lb original bike weight, I weigh 175 and carry 10-20 lb of stuff
TSDZ2B from ecocycles, no throttle, no ebrakes (i'm careful though!), 42T chainring, running OSF, with cooling mod
Bicycle motor works battery 52v10a pocket rocket, it was supposed to be a molicel battery but doesn't say it is on the invoice so, idk?

Riding at 12-20mph, mostly using medium/lower gears, between levels 1-4 of torque assist but mostly at 1 or 2, occasional haul up a hill at 5-7. Mostly on flat/slight incline, occasional hills. I'm in portland, OR.

I'm going from 100% to 30 or 40% in about 15 miles, does that seem normal?

For 20MPH on the flats, assuming the motor is doing all the work, it takes about 20wh/mile, probably 300-350w motor power, 400-450w out of the battery (difference is wasted as heat).

If you have a 52v10ah battery, there's around 500wh in it (v x ah = wh), so 500 / 20 = 25 miles of range, more or less. Since you also have hills with potentially *much* higher power usage (especially if you are not shifting down to lower gears to let the motor run more efficiently), the range could be quite a bit less than that depending on actual usage on the hills.

Very general simulation (hubmotor rather than middrive, doesn't matter much for flat roads, gearing and motor size makes a difference for hills though so you could use "middrive mode" and your specific gearing ratio(s) used on the hills, and the hill grade, to guesstimate wh/mile usage for those parts of your trips).
https://ebikes.ca/tools/simulator.html?motor=MG310_STD&batt=B5211_PF&cont=cust_15_70_0.03_V&hp=0
Most of the numbers and graph aren't relevant because they're not your actual motor system, but the general power usage figures are roughly the same for any system under those conditions.
Load 334W
Batt Power 411W
Consumption 20.5 Wh/mi

If we assume you have some say, 7% hills for 20% of the trip, power usage goes up to over 50wh/mile
Load 552W
Batt Power 761W
Consumption 55.3 Wh/mile

so say 20% of 15 miles is 3 miles at 55wh/mile, or 165wh, then 12 miles at 20wh/mile or 240wh, that's 405wh out of about 500, so 80% of the battery used up in only 15 miles instead of the 25 it might get on just flat roads. Even a very small slope makes a difference to power usage, so a road that "feels" flat with the motor (but not with just pedals) will use up more power than an actually flat road.

If there are any winds, they also eat up power. A 10mph headwind means it takes as much power as going 10mph faster than you really are, and that's a significant amount of power when up at 20mph, going to 30mph. The opposite is true of tailwinds--it's like riding slower by that amount.

Startups from a stop eat power up just like going up a hill--the more weight the more power to acclerate it, and the harder the accleration and the longer it lasts the more power is used to do it.

So your actual power usage especially on hills, and at startup from a stop, and any winds, will be needed to really say if your battery is supplying the capacity it should.

If you have a cycle analyst or other wattmeter / coulometer between the battery and controller, you can directly measure power usage and total Wh out of the battery, if necessary or if you're just curious.

BTW, when I google "Bicycle motor works battery 52v10a pocket rocket" I get this relevant result
https://bicyclemotorworks.com/product/ebike-battery-pocket-rocket-s-52v-10ah/
which says it is samsung cells, not molicel. See quote below off the page. If this is not the correct battery, then link to the one you have instead.

If it is right, then this page
https://lygte-info.dk/review/batteries2012/Samsung%20INR21700-50G%205000mAh%20(Green)%20UK.html
gives some test data for these cells. Since they are only 5Ah each, and it's only a 2p pack, and the TSDZ2's LVC is almost certainly not set low enough to deeply discharge the cells (because that's bad for them over time), you probably can't actually get 10Ah out of them (even the BMS is probably set to not allow totally discharging the cells), but more like 8-9Ah. (even totally discharging them doesn't get 5Ah each per the test chart below, even at only 1Ah, but at the 5A (per cell) rate you're probalby using them at, best capacity even at total discahrge is only about 4.6-7Ah, so a bit more than 9Ah total).

https://lygte-info.dk/pic/Batteries2012/Samsung%20INR21700-50G%205000mAh%20(Green)/Samsung%20INR21700-50G%205000mAh%20(Green)-Capacity.png

The Pocket Rocket S Ebike Battery is built with the latest Samsung 50S 21700 cells. Bicycle Motor Works is a USA Made Company. Your electric bike battery is a premium product.


* 52v = more power on a 48v system. Safe and simple power upgrade!

* 10ah (MASSIVE CAPACITY!!!)

* 45 amp continuous BMS

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* 14s2p – 28 Genuine First Grade Samsung 50S 21700 cells

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* All Battery Packs are shipped in the order it is received. Please allow 2-10 days to ship. Tracking will be sent as soon as it ships. Contact us if you need assistance.

More Highlights:

1. 52 volts – The ultimate secret weapon for your 48 volt system. Compatible with 48 volt motors and controllers – plug and play. You’ll enjoy more power while gaining more range. It’s win-win!!

2. 10 amp hours translates to 520 watt hours.

3. The more pedal assist (pedals assisting) – the longer the battery will last on a ride.

4. Our 14s 45amp continuous BMS with temperature protection will ensure stability within the battery pack and keep all 28 cells juiced up properly.

5. This 52v pack is built with a tight frame for better heat dissipation. Having too much empty air space actually acts as an insulator – trapping the heat inside the pack (think double-pane windows). Connections are made with solid Nickel AND Copper strips, spot welder to each cell. Each cell and each series is tested before assembly. The BMS will prevent over charging and will balance the cells after a full charge. It basically makes your battery as safe and as efficient as possible. much bigger than a Samsung 30q pack with almost 35% more capacity!!

 

[E-HP]

Riding at 12-20mph, mostly using medium/lower gears, between levels 1-4 of torque assist but mostly at 1 or 2, occasional haul up a hill at 5-7. Mostly on flat/slight incline, occasional hills. I'm in portland, OR.

I'm going from 100% to 30 or 40% in about 15 miles, does that seem normal? I haven't calibrated the battery or torque assist because uhhh I have no idea how and just don't understand the manual.

thanks!

Seems high, but percentage indicators on the display or battery are at most a vague estimate of remaining charge, with no standard on what it really represents from one manufacturer to another. Almost as bad as saying I have two bars left, LOL. Providing the starting and ending voltages would be some actual data to see if it's reasonable usage.

 

[docw009]

In my experience, the TSDZ2 is low power and easy on batteries. You'll have to be more qualitative in your estimate on battery consumption. The gauge on my VLCD5 display as a lot of bars, but without volts, it's useless to me.

I am barely able sustain 18 mph on my TSDZ2 with motor doing all the work. I ride a lot slower. The other day, did 20 miles at 12 mph in Eco/Tour mode and on recharging the battery, which was full when I started, it only took 2AH, which on 48V is 100WH, and 5WH/mile. I've also had the wattmeter on the battery and get about the same number. I've got a 13S2P 6AH battery that should be capable of the 14A drawn by my TSDZ2.,

 

[Two4Seven SuprDan]

OSF open source firmware -- buffs up the power and battery usage a bit, makes the economy 10ah battery small for the application imho...;.

no pictures of the build? it might sound counter intuitive but try riding in a lower gear so the motor is not pushing so hard for rpm, youll get more inerta and less heat from it, but have to move the pedals faster.

 

[DeezNeuticles]

thanks for the inputs everyone!