Add extra batteries for distance?

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AlexNC's picture
Last seen: 15 years 2 months ago
Joined: Wednesday, July 23, 2008 - 10:48
Points: 6
Add extra batteries for distance?

Small intro :

I am new to electrical vehicles, but with the United States current conditions with gas (dependency to foreign oil and environmental), I have finally had enough and feel like I need to do my part. My ultimate goal is to buy an electric scooter/motorcycle in the next few months to year, and eventually have a solar net-metering/charging station. Right now I am very encouraged by the X-treme's XM-3500Li, but it will really comes down to real world user reviews. I am also continuing to watch the Vetrix in hopes that its upcoming lithium batteries do not adjust the current pricing too much. Other contenders are Electric Motorsport's GPR-S and EVC's Volta. More than likely I will go with the XM-3500Li or GPR-S due to the ability to possibly upgrade and maintain my own batteries. The closed, non-standard battery systems of the other bikes seem to lend themselves to more expensive maintenance.

With that said, I have a pretty basic question for the electric veterans here. Assuming I go with a bike that is easily 'gutted', [u]would I be able to add extra batteries to extend my driving distance?[/u] For example, from what I understand, the XM-3500Li is coming with a 20 pack battery system. What is stopping me from spending some extra money and adding 4 more battery packs to extend my driving distance? Of course, this is assuming I can find room to put them.

Do the batteries charge in series, or do they all charge separately for peak performance/longevity? I am assuming charging in series means the following ... the first battery charges to full capacity, then the next one starts to charge. It fills up, then the next one starts charging, etc.). Any further explanations on charging systems, types, pros/cons would be appreciated.

Needless to say, I am very excited about the fact that batteries have finally got to a point that they can built long distance scooters/motorcycles. These are some very exciting times, and it is fun to be part of the pioneers that are making the shift toward less foreign oil dependency a reality. Though, I am saddened by the fact that there seems to be not scooter style lithium bikes coming out of the United States. Everything is Chinese. But I guess that is better than giving all my fuel money to countries I do not trust.

reikiman's picture
Last seen: 11 months 3 days ago
Joined: Sunday, November 19, 2006 - 17:52
Points: 8447
Re: Add extra batteries for distance?

It helps to understand battery math. And to understand first that the electronics especially the controller is rated for and designed for a given voltage. It may be possible to increase the voltage of a vehicle and not have it burn up, but any electric gizmo will burn up if the voltage gets too high. If the controller is designed to handle a higher voltage then it will be okay...

Battery math ...

Connect two batteries in series .. you add their voltage together

Connect two batteries in parallel ... the voltage stays the same and the amp-hour capacity is added together

What you described is to add additional batteries in series. This will increase the voltage of the pack. If the voltage is within the specifications of the controller you'll be safe. If not the magic smoke will be let out of the controller and you'll be dead on the side of the road (or maybe dead in the middle of the road).

That said there are Xebra owners who have done exactly this. The Xebra is a 72v system and the controller it ships with is rated for 72v. But some Xebra owners run theirs with an added battery to make an 84v system. How? The Alltrax 72v controller uses components rated for 100v and an 84v battery pack has a maximum voltage just shy of 100v, meaning that with an 84v system can be (knock on wood) run on a 72v Alltrax controller. The safest method I've heard of to do this is ... leave the extra battery out of the pack initially, then after a couple miles when the total pack voltage is depleted a bit then switch the extra battery into the pack. It will act to increase the pack voltage and the total voltage will still be low enough to not run the risk of making the controller let out the magic smoke.

Other vehicle owners do this .. for example the wilderness energy bicycle kits regularly run at 48v or higher.

Adding voltage doesn't have a direct effect on range. It has a direct range on speed because roughly speaking voltage=speed and amp-hours=range.

This means getting a longer range would mean adding more batteries in parallel rather than adding more in series.

The last problem is-- where will you put the batteries? There usually isn't much spare room in an EV because usually every effort is made to wedge as many batteries as possible into the vehicle.

AlexNC's picture
Last seen: 15 years 2 months ago
Joined: Wednesday, July 23, 2008 - 10:48
Points: 6
Re: Add extra batteries for distance?

Thank you for that detailed description. That was very informative for a newbie like me =)

Any word if the Extreme 3500Li or GPR-S are Series or parallel?

What if a bike comes wired in Series, but I want to make it Parallel so I can add extra batteries for distance ... is this possible?

Here are the specs for the GPR-S ...

sparc5's picture
Last seen: 12 years 9 months ago
Joined: Wednesday, May 21, 2008 - 09:29
Points: 243
Re: Add extra batteries for distance?

Hi Alex,

Welcome to the forum.

You can add packs to extend your range. It's not as simple as you're hoping. I'd go to battery university's website and read to your heart's delight or read the archives here for nuggets of information.

Batteries charged in series means they all get charged simultaneously while wired in series. It's been known to overcharge and undercharge batteries limiting their life.

Don't be sad that it's all Chinese, unless it's child labor or people with people making below living wage assembling them. Seriously, that's not cool. Americans find new ways to be competitive. Did you know the average american changes jobs five times in their life? Not small changes, but in completely different sectors! Now that's the power of a flexible economy!

What is really exciting is many battery startups are coming online in the near term, it really might give us the range and speed to compete affordably with gasoline powered vehicles. Right now we're mostly using lead acid batteries who's basic design was invented in 1859. Even the Edison Cell used to power early electric cars lasted longer. Oil companies just buy up patents and sit on them, it sucks. It makes me depressed just thinking about it. You might as well ride a bicycle, it's more healthy and you'll save money. Or go to Europe where there are nice smooth high speed electric trains you can jump on to get to one city to another.

-DC-DC converter replaced with a Dell D220P-01 power supply.
-72V mod
-Expensive bank charger until I come up with something better... Still trying.

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