Of course one of the first questions that arises when you plan to drive an electric mobility scooter a long distance is do you have batteries that can get you that far? I think I have just about got a plan sorted out for batteries, but I’ll have to get them and test them to see what distance I can get, how long they will take to charge, and if they can be relied on to perform well over 4 months time. The scooter uses 2 x 12 volt 40 Ah sealed lead acid batteries in series to power the 24-volt motor. These weigh 32.5 lbs each. These will take me about 20 miles on a full charge. The charger that came with the scooter is a 24-volt 5-amp unit, and, since it charges the two batteries in series, the time to fully charge two completely discharged batteries would be 8 hours. Clearly neither the power storage nor the charger output is ideal for this trip. So, lithium batteries are needed. I want drop-in replacement LiFeO4 batteries (e.g. 12v 50Ah, 14.3 lbs each), but I am told there is a possible issue with using these in series. It relates to balancing the cells and cut-off voltages, but I think they will work and I will need to monitor their status to know where I am relative to their discharge cut-off value. I’m not sure how to do that, and because they maintain a relatively constant voltage throughout their current delivery they even say to not rely on voltage as an indication of status. I figure I will get a pair and run them to they cut off and see how far I get. Then I will need to see how long it takes to charge them, and then repeat the run to see if their performance is consistent. It seems like it could be good to plot performance for each day to see if they change. Also will need to test with a load (Gracie is 80 lbs; what about uphill in the Rockies; etc). The problem now is that I can’t find two of the same batteries in the US, although they will be available later in December.
I will also need backup power. I think this 24v 50Ah (27.8 lbs) battery may do the trick. I did not want to rewire the system, but I will probably need to rewire if I want a convenient way to switch to a backup. I just need to figure out where to position this. Might just strap it to the floorboard using a couple of flat bungees. This is available immediately, and it will allow me to test see if a 50Ah power supply will get me the distances I need. Even with the additional power of the two replacements plus the backup 24v battery, the overall weight will be around 9 lbs lighter than the two original batteries.
I think this will also provide an emergency backup option, and may even be something I can use to charge the backup battery while we travel. I have seen 60-120 watt units that would work. From what I understand, best-case scenario, it should take a 100-watt charger 6 hours to charge one 12v 50Ah battery.
Gracie’s Side-Car or Trailer
I will not expect Gracie to run all the way across the US. I could be wrong, but I don’t think she will be up for 25 miles/day, but she will be happy to do 5-10 miles most of the time. So I will need to either design and construct a side car or opt for a trailer. I prefer the idea of a side car, because I would rather have her at my side than behind me where I can’t keep a good eye on her. I’m thinking of something that attaches on the right side of the scooter with an aluminum frame that is hinged where it attaches to the scooter, a platform about 15″ wide that is supported by a 14″ bicycle wheel. The platform could swing up so that the wheel lay flat against the bottom of the platform, and the unit could be secured when not in use or when a narrow path was encountered. It would be padded and Gracie could lie down and put her head on the scooter floorboard or sit up. It would need to have some sort of outer support on the right side.