Which would you rather buy? LiFePO4 48V15Ah, or 72V10Ah

broloch

1 kW
Joined
May 10, 2008
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358
Which battery would you rather have?

LiFePO4, 48V15Ah
$500
35km/h top speed, fair distance - 45km

LiFePO4, 72V10Ah
$600
52km/h top speed, shorter distance - 32km

Are my distance estimates off?
I figure with the 72V battery, most would be going at a higher speed anyway, using more power per kilometer.
 
you're getting 720 watts of battery either way, so unless there is a bms or charger or something just buy the cheaper one.
 
I think the question is which one do YOU want so as Ypedal said you have to specify the components you have or plan to buy for your build, if that's what the question is all about.

If I had to answer the question you pose for myself however I'd take the 48V15Ah battery :wink:

-R
 
That would be with a CLyte 408 motor with a 72V controller. I think that speed is fun. 50km/h top speed would be nice to have around, but it doesn't mean I will always be going that speed. In cases of passing parked cars, etc.. it just feels safer at higher speeds, when the way is clear.
 
One option for me would have been to get the 48V 15Ah battery and then take my current NiMH battery and convert it to a 12V 15Ah battery and add it as a 12V booster.
That way I would have a 60V 15Ah battery. But is this a bad idea? Combining a 48V LiFePO4 pack with a 12V NiMH booster?

I could skip it, and just go 72V 10Ah instead, and keep my 60V4.2Ah NiMH pack as a backup. But the cells for the NiMH are getting hammered pretty hard.
 
Good point. I am using a 25A controller, how will the 10Ah's discharge (1.5C) versus the 15Ah's discharge (1C) affect the life of the battery?
Is 72V easier on the battery? Is 1.5C on the 10Ah incorrect? Will I only be using 10A on the 72V?
 
Really? The range will still be the same at a relatively slower speed, similar to what a 48V will put out?
 
Don't mix your nimh with lithium.

The controller determines how many amps to allow, so if it's a 20 amp controller...

20A x 48v = 960w ( peak output )
20A x 72v = 1440w

The voltage determines the RPM of the motor, higher voltage = higher motor rpm = higher speed..

If you pick a motor that does 20 mph at 36v, it will want to try and go 40 mph at 72v.. the faster you go in real life the more watts you need x 2 ( and more ), wind resistance is just like going up hill . and if that motor can't get going fast enough it will suck as much amps as the controller will allow and this is not a good setup.

If you get a motor that goes 40 mph on 72v, it is alot more fun to feed it 40 amps instead of 20 so that you get 40x72v = 2880 watts and that requires high C rate batteries.

Basically.. get a motor that goes 20mph in a 26" wheel.. put that in a 20" and run it at 72v, thank me later !
 
I see what you are saying. However, I thought that the amp rating on a controller was the maximum amount the controller would allow through it.

So if my controller were a 25A controller, it could pull a maximum of 25A give or take 2A's from the controller if I needed it (extreme hills, unreal acceleration, heavy headwinds, etc.).

But the controller isn't pulling 25A's all the time. I may take 20A's to accelerate to 43km/h. But once I reach that speed, I may only need 15A's to sustain that speed.

Does that sound about right to you?

Also, if I were to have to batteries, a 10Ah and a 15Ah, with a max of 2C, is it bad to use the 10Ah battery with a 25A controller, or is it better to use the 15Ah? Is the only problem battery life? e.g. 1000 discharge cycles will drop the 10Ah to 87%, whereas, 1000 discharge cycles will drop the 15Ah to 91%.

Or is there also voltage sag? e.g. 48V 15Ah makes the bike go faster than a 48V 10Ah battery? Or perhaps, the 48V 15Ah battery is better at accelerating because the discharge rate is closer to 1.25C?
 
Ypedal said:
Don't mix your nimh with lithium.

The controller determines how many amps to allow, so if it's a 20 amp controller...
20A x 48v = 960w ( peak output )
20A x 72v = 1440w
The voltage determines the RPM of the motor, higher voltage = higher motor rpm = higher speed..

As ypedal shows above, 72V gives you about 50% higher power. This is not just on the top end, but more torque at lower speeds also.
 
but would i be killing the battery much more quickly at the higher "c" discharge?
 
broloch said:
but would i be killing the battery much more quickly at the higher "c" discharge?

That all depends on what battery you pick.

a 10ah 5C cell will do better at 20 amps than 20ah worth of 2C cells. ( less weight, less bulk, less cells.. less connections.. easier to mount.. )

But forget all that.. use the smallest battery capacity you need to get you the range you want, higher quality cells is always better than more cheap one's . oversized ah packs are great if you like to do 100 mile runs but for most of us who like 20 or less km per charge a 10ah pack is plenty.
 
I'd take the 48v15ah for sure. It's all about capacity. You're going to eventually want longer bike rides and the 48v15ah will probably get you farther than the 72v10ah.

I don't know about anyone else but I find myself mostly going between 20mph - 30 mph most of the time. 48v will get you there. I've went 37mph and after a while, the speed just doesn't appeal to me as much as enjoying a nice long ride on the bike.
 
I'm with bikeraider, and to be honest I'm surprised we're in the minority. Both packs have the same amount of wh's. Both will use the same amount of watts to keep to a certain speed like 20mph, so the small pack wil pull more amps than the large to go (x)mph, therefore both packs will last equally long.

The higher voltage pack could be marginally more effecient (probably not noticeable) due to needing less amps to keep the same speed. If you go 20mph all day it doesn't matter which pack you use, but it is a lot of fun being able to how off with 72 volts occasionally.

I have the 72v10ah headway pack, and while I can go 40mph, I very rarely do, most of my riding is at 20, and at that speed I can go 30 miles+.

Obviously if you have no self control then my whole argument is moot, but you're a big boy now, you can control your right hand can't you 8)
 
Yeah, I agree with Ypedal. Carry what you need, no more. If you only need 10 ah of 48v then get that assuming 5c cells, less cells than 72v to carry. The range would be less than 48v 15 ah, but if you don't need it then don't carry it.

As for what would I buy for a 408? Depends on what I used it for. Most likely street use, and my rides are allways long, so 48v 15 ah of 2c cells would work fine for me. I'd be nearly illegally fast on the street at 48v on a 408. (25 mph for mopeds in NM) Why would I want to call attention to myself running 72v in the street? A dirt bike would of course want the 72v battery, but it wouldn't be a 408. 9c or 5305.

I'll never understand this I'm safer on the street going illegally fast idea.
First, when you crash, you'll know that idea was wrong. Belive me, after 45 years on two wheel vehicles, its not IF it's WHEN.
Second, nobody expects a bike to be that fast so they pull out in front of you.
Third if you need to "keep up with cars" you need to seriously examine your choice of route.

When I need to go where I need to keep up with cars, I take the 150 cc scooter. People expect a motorcycle to be fast. Cops don't mind you going 45 mph on that bike. If I haul ass and get a ticket, It does no harm to other ebike riders.
 
Those are two valid perspectives, and I thank-you for your posts. I will have to do some "soul-searching" as to what it is that I need from my ebike.

I was going about 43km/h and it felt pretty fun. I actually wanted to go faster. This was running at 60V. I wasn't running the entire way at 43km/h, there was a slow acceleration, followed by slowing down for road hazards, as well as for stop lights. The burst in speed is there if I needed it.

Now, I am faced with a dilemma, go 12V up to 72V for more speed when I need it, or drop 12V to 48V to keep it closer to legal. I guess, there is also option "C" as most Spherers like to offer...get a bigger pack than I currently have, but keep it at 60V...

So, I won't try to hurt other ebikers by going at full-speed all the time. It'll be there when I need it.

By the way, I have already had a crash, but it wasn't on ebike, just a regular bike.
 
Most of the time, travelling fast is a BAD idea. It increases the chances of a crash, and when a crash occurs, it increases the effect of the crash.

Travelling at illegal speeds is not generally a good idea. However, sometimes, there may be a need for it. An example is when the bike lane is occluded due to construction or by a parked vehicle, or a service vehicle. It CAN be useful to have a higher speed, and stronger acceleration, when one has to move into the passing and only available lane (two-lane road) in order to pass the occlusion. At times, it may agitate drivers if there is only one lane, at other times, the driver may not give enough room to the cyclist in that one and only available lane and may clip the cyclist. That is an instance when it can be dangerous for a cyclist going slowly. If he were going fast, he could take the lane, and go with traffic for a small stretch of lane before moving back to the right and into the bike lane area.

It can also be argued that the cyclist could take the lane anyway and take the entire lane, or the cyclist could stop until traffic is lighter, then proceed into the left lane when there is no traffic. I have done this today already. It can be safer because the cyclist is not subject to the higher speeds that could result in loss of control, or a crash.

So the case is, it can be safer to go faster when needed. But, it can be just as safe to stick to a lower speed, and in the instances when higher speeds are required, it can be a way to keep in a safer position. So what determines whether to choose for more speed, or to keep the maximum speed of the ebike lower to improve safety? This is really an issue of the ebike rider preference. What does he feel more comfortable with while keeping safe? This will depend on whom you are conversing with and what he considers the best way to maintain safety, with more speed, or less speed by pulling over or taking the entire lane.
 
the ride without any issues... The caps available are enough aren't they ?
I believe humans can hold enough wisdom
 
One otha thang I would take in to consideration is that its simpler to wire in a booster pack in series than parallel.. If you need more bat down the road.
 
Maybe I need a reality check.

99% of ebikers probobally ride stock kits or bikes that go 20-25 mph. Whether legal or not in a given jurisdiction to go 20mph most are not getting tickets. In my town, cops completely ingore me since I stop at stop signs and don't ride the wrong way up the street. They seem to ingore regular bikes that do that stuff too. Pretty much, they pay attention when you ride under somebodies wheels and that's it for my town.

That leaves the 1% ers, Us on the Sphere. Lots of us are running 48v, many are running 72 and some 100. But who's getting tickets? Nobody really. One guy in New York, but there ebikes are completely illegal. So my perception of high volt ebikes ruining it for the rest may be completely false so far. This kind of bike is pretty expensive, so the young dumb crowd may just gravitate to the used motorcycle option which is cheaper and faster.

So I'll back down from my pulpit about what voltage you want to run on the street. I just find that personally I never need more than 25 mph, on my route, in my town. But if moped legal speed was 35, I bet I'd ride that speed. :roll:

But I will repeat what I said about route selection. Bike lanes are nice, but there are quite a few in my town that I consider a stupid choice of route. An adjacent street with houses is safer than the commercial street with the bike lane. And guess what, speed limit in the houses is 25. Don't drive my car faster there either. I think it's safer to be patient and stop if you must to stay safe, rather than rely on speed to squirt through a tight spot. I ride the motorcycle or drive the car the same way. But stopping can cause a problem too, so again, route selection helps. Where some people live, and where they need to go may make any kind of bike a bad choice or a good one.

I totally agree that any bike, motorcyle, etc is invisble at all times to most car drivers and ride accordingly. I've never been hit by a car, but till I slowed down, I did hit a few at my own fault.
 
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