Question for those e-bike guru's

[Maka]

I have found the e-bike for me. Question, I sort of know electrical stuff, but just enough to be dangerous! If the bike I want to buy has a 48V 16 Ah battery..... If I want to add a second battery to increase range. From "what I know". If I buy the exact same battery and hook it in parallel all "should be fine". What are the probable consequences of buying a secondary battery that is not an "exact match"? will one batterie hurt the other? Will it fry the controller in not exactly the same Amperage / voltage? Your advice would be greatly appreciated!!
Thanks, Maka

 

[Maka]

Thanks !!! You really helped me understand the "same voltage" diff. amps is ok. I have been drooling over one specific e-bike for quite a while. But still researching to make sure it is the right choice. since it's SO expensive. From you video I noticed you mentioning a mounting solution for the "splitter/mixer". My main hobby is 3D printing. If your interested? I can make mounting "brackets" for any converter / (or thing) for any tube size or shape. I don't plan to make money doing these, but it would be nice to at least "break even". I love the design side of all thing, and usually spend dozens of hours designing things that work. If this is of any value to you, drop me an e-mail. its "[email protected]".
Thanks. Maka

 

[Maka]

I have my eye set on the..... 1250W 16Ah 48V Electric Mountain Bike, 26 Inch Wheels Addmotor M-5500 E-Bikes, Blackish Green. I thought getting a second battery would help distance / power? If it's the way to go, I still have to learn the proper way to charge them.... I am guessing you disconnect both batteries from the duel battery parallel connector?

 

[indianajo]

That's no problem, as long as you parallel connect with battery converter.
And the voltage would have to match.

That's one opinion. Most quality batteries have a bms (battery management system) to charge the weaker of parallel stacks during the "balance charge" to full voltage. The highest voltage stack(s) are turned off while the weaker stacks charge. Your parallel batteries will not have a bms to charge the weaker of the two batteries during balance charge while the better one is turned off.
More reliable would be a 2 way switch between the discharge cables of the two batteries. then you discharge one at a time. You also charge one at a time. Switch needs to be rated for bat voltage, and for the discharge current you expect. 30 amp 48 v switches are rare; it is probably easier to unplug & plug in two connectors like andersns.

 

[Maka]

Might be best to unplug both batteries and hook each one of them to their own charger. So charging time would be whatever is normal for 1 battery.

 

[Maka]

I can also mount both batteries and only hook up one and if it je6ts used up, just swap the plug? But i was thinking, double capacity would be less trouble in the long run?

 

[harryS]

I don't use a smart Y-connector, just a straight wired one. I parallel my 36V batteries, which are 42.0 volts at full charge, only when I know both are charged fully, A smart connector is a good thing to prevent a careless mistake. I could make one with a pair of diodes. Don't want to do it.

As far as charging, it depends on the battery, but most should be separated and charged separately. You break the design safety by charging one pack and having its output charge the other, Really, if battery 1 has a charger overvoltage failure and a BMS failure simultaneously, you got a major problem anyway, but why include battery 2 in it.

.

 

[tomjasz]

You won't get the extended range like connecting two batteries.

Explain please?

 

[PedalUma]

@Timpo is correct. Yet it is so much easier to swap two identical batteries. And for most rides you just take one, cutting battery weight by half. I use the smallest battery I can for a given ride. I also use connectors that work for different sizes of batteries.

 

[tomjasz]

I'll give you a scenario.

Interesting. I’m gonna have to pay better attention. But at the moment I don’t think I saw those same results. But then again I no longer makes long rides needing max mileage. Two identical triangles to test.
Thanks for the post.

 

[PedalUma]

Interesting. I’m gonna have to pay better attention. But at the moment I don’t think I saw those same results. But then again I no longer makes long rides needing max mileage. Two identical triangles to test.
Thanks for the post.

Those suckers are HUGE! I built that 11-speed road bike yesterday with one 3-pound battery.

 

[tomjasz]

Those suckers are HUGE! I built that 11-speed road bike yesterday with one 3-pound battery.
View attachment 105900 View attachment 105901

Yeah, I over bought and will be retiring some packs that are dying of old age.

 

[PedalUma]

I read that any battery retailer in California must accept any used battery, provided that it is less than eight pounds. Anyone willing to fact check this?

 

[harryS]

Peukert's Law, presented in 1897, says "As the rate of discharge increases, the battery's available capacity decreases, approximately". Use this for your parallel battery expectations,

In real life terms, two identical batteries in parallel, with each putting out 4 amps, will give a longer range, than running each battery in succession at 8 amps. Or two batteries that give you 15 mile range singly could give you nore than 30 miles if used in parallel, How much more is experiment. This gives me chance to do some science on my daily riding, but I never write the results down, or forget to zero a meter, etc.