Expected range of 48v 17.5aH?

Posted by lawyerz88@reddit | ebikes | View on Reddit | 16 comments

I'm having some range issues with a brand new 48v ebike with 2.2" MTB tyres.

The battery is a 17.5aH 48v Reetion Dorado battery. With mixed terrain, mostly flat, no throttle use and a rider weight around 90kg, I'm only seemingly getting 35km of range which seems low.

I've also noticed if I leave the battery charged up to the minute I am using the bike, range is a further than if I charged to full and turn off the charger and only pick it up again a few days later.

Need some advice, have I got a faulty battery? Should I ask for a replacement battery, or is there something I'm doing wrong?

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Bagel42@reddit

How many watts is your motor?

You have an 840wh motor. If you were to draw 840w the entire time, you would be out of battery in an hour. If that gets you to say, 20mph, then you would get 20 miles of range or about 33km

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lawyerz88@reddit (OP)

Ooo this is a useful visualisation. I've got a 500w rear hub bafang motor, which peaks just over 800w according to my screen. My commutes about 1 hr 15 mins, for simplicity let's say I ride at 800w for half the journey and 400w for the other half.

That works out to be 500wh + 250wh used so 750wh used so it's close.. maybe it's correct.

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plorraine@reddit

In my 4000lb Tesla Model 3, I would get about 3 miles. My e-scooter would get 20-30 miles depending on the speed (most highly) and tire pressure. My e-bike using PAS 2 out of 9, will get about 40-50 miles.

If you are struggling with range, first check your tire pressure. Then conduct your range experiment at 10-12 mph - your range will soar. Energy consumption over a given distance roughly doubles every time you double your speed - you get there in half the time but you need to input 4x the kinetic energy. The lighter the bike and the lighter the rider, the longer the range will be as well. Also, don't blast up hills - you may be able to cruise up hills at 10 mph while at 20 mph you will max out the current from your battery and things will heat and become less efficient.

So decrease rolling resistance, lower weight where possible, decrease speed - all will put you closer to what the manufacturer lists as the nominal range.

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TenMilePt@reddit

https://reallygoodebikes.com/pages/electric-bike-ebike-range-calculator

2 things I generally find -- the battery either has a faulty cell (or bank of cells) or the cells are not properly balanced -- not all BMS' balance cells. Its also possible it has a loose/wet/damaged connector as those Dorado style batteries tend to get wet inside.

If you have a multimeter (or your bike display shows voltage) -- when it's fully charged it should be at 54.6V when unplugged from the charger. The BMS and/or your bike will likely shut the motor down when the voltage reads 41V. It is useful to take a voltage reading when its fully charged and when it shuts down -- note that when you put the battery under load (e.g. while you are riding) the battery voltage will drop by 2-3V so it's quite possible to see 43-44V on the battery after the bike has shut down. If you find the fully charged voltage is less than 54.6V you probably have a bad cell or cell bank.

Of note, if this is a new bike -- that battery was built in June of 2022 so might be old stock.

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lawyerz88@reddit (OP)

I'll look at getting a multimeter if it isn't too costly. Is having the battery being old stock a problem per se on this new bike? It's new and hasn't gotten into any wet riding at all.

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TenMilePt@reddit

You can usually grab a MM for $10-20.

Cell balancing is something the BMS (circuit board) on the battery is supposed to do. Sometimes the manufacturers install BMS modules thar won't balance the cells. It's supposed to happen each time the battery is charged over 90%. What it does is ensures each cell is charged to the same voltage so that they drain and wear at the same level.

Older cells aren't really a terrible issue. It depends how they were stored -- charge level and temperature can degrade them.

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chuckwolf@reddit

Depends on the wattage of your bike and the speed you ride at on average. But with that battery on a 750 watt bike at class 2 speeds, 20 mph it should last about an hour or slightly over. So 20 miles range at the highest PAS level, further if you go slower and use less actual motor power.

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