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Razor Ecosmart Metro hill climber modifications

Hey guys! I started reading this forum a week ago and you've already answered about a hundred of my questions, helped me choose which scooter to go with and everything. I'm buying a new Razor Ecosmart Metro, and I plan on upgrading it in stages. If you could answer these few questions, I'll be well on my way to finishing the first! So, I have a long uphill on my commute home from work, and I want to increase the range so I don't blast up the hill and then have to crawl home for the last 2 miles. There are medium ups and downs all over my area, so I want to be able to get as much range as I can in general. I want to wire a second battery pack, as discussed here: but with some changes: First, I want to mount the batteries behind the seat instead of on top of the existing pack. Should I wire them with an on/off switch, as backups, or wire them all together? (I want to avoid getting a new controller and throttle etc, for the time being) If you could help me understand the pros and cons there, that would be huge! (My gut says go with the switch.) Second, to limit costs I'm sticking with 8ah batteries (Item # BAT-12V8AX3) instead of going up to 9ah, but I'd like to hear your thoughts. I figure I'll be essentially doubling my range if I add a backup pack with a switch anyway, and it makes sense to buy 3 new batteries instead of 6, since I plan on going with li-ion eventually. My only other question is about torque. I plan on upgrading to a 750 or 1000w motor in the future, but for now I wonder if you can guide me through choosing a different sprocket to gear the 500w motor for better hill climbing? Top speed isn't the priority here, as long as I'm not crawling along I'll be happy. This is my first scooter project, and it's been a blast scrolling through this forum and your parts website doing my research. You guys are great! Thanks for the help

Regarding wiring the second battery pack to the scooter there are pros and cons for each method.

Wiring all of the batteries together into one battery pack provides a longer range than wiring them with a switch that selects one of the battery packs at a time. This is because the slower that batteries are discharged the more capacity they have. However when making a battery pack all of the batteries should be the same brand, age, and Ah rating. So if the scooter has a good original battery pack and you are adding a second battery pack made with different brand batteries then using a switch to select one battery pack at a time would be the best way to go, however if you plan on all of the batteries being the same brand, age, and Ah rating then wiring them all together into one battery pack would provide a longer range for the scooter.

If all of the batteries were made into one battery pack then a larger battery charger would be needed, however if the two battery packs were kept separate then a second battery charger that is the same size as the original would be needed in order fro both battery packs to be recharged overnight.

Even though the scooter's range would be slightly decreased with two battery packs and a switch, it would allow for the second battery pack to be switched on when the first one gets low on power. This is a good feature to have because then when the first battery pack gets low you can switch the second one on and turn around to go home. While with a single battery pack you have to guess when the batteries are halfway discharged.

The difference in range between 8Ah and 9Ah battery packs are equal to their Ah rating numbers. The 9Ah batteries will provide a 12.5% increase in range over an 8Ah battery pack.

8Ah batteries are good for loads up to 16 Amps. A 36 Volt 750 watt motor consumes 21 Amps, and a 36 Volt 1000 Watt motor consumes 28 Amps. So an 8Ah battery pack would not provide enough power for a 750 or 1000 Watt motor. Here is a sealed lead acid battery discharge chart to help with selecting the right size batteries for a certain motor.


Since most electric scooters have a 30 minute or longer range the 30 Minute Maximum Discharge Current row of the chart should be used to determine what size batteries to use.

For better hill climbing changing the rear wheel sprocket provides the most options. The Razor EcoSmart scooters original wheel sprocket has 65 teeth. 80 and 89 teeth sprockets that bolt directly onto the EcoSmart's freewheel sprocket are available. The large the wheel sprocket is the better the scooter will be at hill climbing.

The EcoSmart scooters top speed with its stock 65 tooth wheel sprocket is around 18 MPH. With an 80 tooth wheel sprocket the top speed would be around 15 MPH, and with an 89 tooth wheel sprocket the top speed would be around 13 MPH.

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