Adding +12V battery for boosting up hills?

[Blueshift]

I was thinking of doing a small upgrade to my ebike. I have a 36v 15ah battery from ping already and its paired with the amped bikes dd 500-700 watt front hub motor. Is there a way i could wire in a smaller 12v battery without rebuilding the 36v so i could have a boost for hills? could i use a switch to turn on the extra 12 volts on the fly as i begin a hill climb?

 

[NeilP]

As long as the controller will accept the extra voltage, and its C rating is at least the same so it will take the current you put through it, it should work just fine
may depend on the HVC of the controller too.

Should not be too difficult to find a switch to take the sort of currents you are likely to be seeing...What 40 amps max? depends on your controller really

 

[cruiserbikeman]

You can contact Ping by email and get his suggestion on what you're trying to do. I have the same kit and run both 60 volt and 48 volt Ping batteries on the ampedbike controller.

 

[dogman dan]

That diagram would work. Or you could just get a 12v lifepo4 battery and go to 48v all the time. If it's just for one particularly big hill on your route, stopping to manualy hook up the booster is not going to take but a few seconds.

Personaly, I find andeson connectors make a good on off switch that's easy to use.

For sure, the controller can do 48v.

 

[tony67]

I've been thinking about this myself lately. It would make a handy push to pass function. Im looking at going to 72v in the future but don't want to be wired at 72v permanently. Its a pain holding partial throttle so i run all the time at WOT. This is fine at 48v but 72v would be too much. What I'd need (and I assume the OP) is instant access to 72v at the push of a button or flick of a switch from a 48v pack to a 48v+24v booster pack.

Has anyone ever seen a switch (pref bar mountable) that would perform this function and be capable of 40 amps @72v. Long shot I know but you never know.

Tony

 

[neptronix]

3 speed switch + cruise control functionality is built into infineon controllers. All you need to do is wire it up or buy a controller + throttle combination to use it.

 

[tony67]

Hmmm, I have a 12 fet lyen that I will be using for this when the time comes, so all i need is a 3 speed switch and to program my controller to the required levels?

 

[neptronix]

yeah - you can set the speed percentage for each position.

https://sites.google.com/site/shelbyelectro/controllers-and-electronics

 

[dogman dan]

Definitely a better way to do it. Even when running a similar three speed switch at 48v, I found the ability to select a power level very nice. Mostly I was doing the opposite, running full power most of the time. But it was very nice to select an economy mode for when I wanted to extend range by 10 miles or so.

I guess I'll never quite get the need to have the 36v -48v thing on the fly though. I suppose it's the local terrain. No rolling hills. Along the valley bottom it's quite flat. But to leave the valley in any direction it's a huge hill. So no need to switch back and forth between voltages constantly.

 

[d8veh]

I was thinking of doing a small upgrade to my ebike. I have a 36v 15ah battery from ping already and its paired with the amped bikes dd 500-700 watt front hub motor. Is there a way i could wire in a smaller 12v battery without rebuilding the 36v so i could have a boost for hills? could i use a switch to turn on the extra 12 volts on the fly as i begin a hill climb?

A booster battery like that will give you more speed on the flat, but I'm not sure it'll help your bike climb much better. For climbing, you need more amps. How many amps does your existing controller give? You know that you can get more by soldering the shunt, which doesn't cost anything?

 

[dogman dan]

Takes watts to climb a hill. Add 12v, you add about 240w more if using a 20 amp controller. And likely you start the climb at a faster speed, which matters if the hill is short. To really fly up the hill, you'd also add amps, and volts, and literally double the wattage.

Solder your shunt, and you have more amps all the time. This could harm your battery, depending on what exactly you have. If you have a strong enough battery, then by all means solder the shunt and add 12v.

 

[cal3thousand]

So this could be a way to use those harvested laptop batteries to augment my speed? 24V 5Ah of Lithiums for a short boost of 72V would be awesome (48V LiFePO4 currently)

Anything crazy about this idea besides the obvious dangers? How could I calculate a pack to make sure that I don't exceed the C rating of the laptop batts?

 

[veloman]

Check my build thread in my signature. I added 3s lipo to a 36v 21amp peak lifepo4. It is wired in, no switch. I want to make a switch for it though. Why? Some here will tell you just run the higher voltage all the time. Well because maybe you don't want matching ah capacity, and you truly only want the extra power once in a while. Running higher voltage than you need means your controller will heat up quite a bit more reducing your battery voltage to the motor.

My plan is to add this 3s lipo booster of mine to my bigger 52v cellman pack, so that I can hit 40mph on my 8t mac. But I certainly don't want to be running 63v all the time on it, as I spend a lot of time around 20mph. So I will need to do a switch. I'm glad you guys say it shouldn't be a problem, especially at my peak amps of 25 or so.

I'd be leary of using low c rate laptop cells. Just spend $30 on a 3s 5ah lipo stick. Parallel two for 10ah if you are pulling high amps.

Oh yeah, you can charge that 3s lipo with a laptop supply easy peasy. I do it 2-3x a day Love it.

 

[veloman]

I was thinking of doing a small upgrade to my ebike. I have a 36v 15ah battery from ping already and its paired with the amped bikes dd 500-700 watt front hub motor. Is there a way i could wire in a smaller 12v battery without rebuilding the 36v so i could have a boost for hills? could i use a switch to turn on the extra 12 volts on the fly as i begin a hill climb?

A booster battery like that will give you more speed on the flat, but I'm not sure it'll help your bike climb much better. For climbing, you need more amps. How many amps does your existing controller give? You know that you can get more by soldering the shunt, which doesn't cost anything?

More volts definitely means faster hill climbing. It's all about wattage. Now, efficiency won't be as proportional, but eh.

 

[d8veh]

I was thinking of doing a small upgrade to my ebike. I have a 36v 15ah battery from ping already and its paired with the amped bikes dd 500-700 watt front hub motor. Is there a way i could wire in a smaller 12v battery without rebuilding the 36v so i could have a boost for hills? could i use a switch to turn on the extra 12 volts on the fly as i begin a hill climb?

A booster battery like that will give you more speed on the flat, but I'm not sure it'll help your bike climb much better. For climbing, you need more amps. How many amps does your existing controller give? You know that you can get more by soldering the shunt, which doesn't cost anything?

More volts definitely means faster hill climbing. It's all about wattage. Now, efficiency won't be as proportional, but eh.

The way I see it is that you have higher power available but you can't use it. Hill-climbing depends on torque, and torque is directly related to current. Power = torque x rpm, so the faster you go the more power you require/use. However, the controller limits current (hence torque), which will limit your speed on a hill. To hit your peak power, you need to reach the peak speed.

When you only have enough torque to do 15mph up a hill, having enough volts to do turn the same torque at 20mph won't help you because the torque x rpm is limited - i.e. your power. It would be different if you had drive through the gears because you could change down, which would allow the motor to increase its rpm with the same torque, and hence give more power. This is one of the reasons it's important to match your battery, controller and motor to the speed and climbing on your own typical rides.

The only advantage then is like Dogman says. You get a chance to approach the hill faster with more volts, so you have extra momentum to help you up, which is OK for short hills, but won't help on those long ones that get you puffing when you have an under-amped bike.

 

[John in CR]

If your bike is bogging down on the hills, ie it can't maintain roughly half of top speed on the hills on your route, then adding 12V won't help and will just lead to an earlier motor death. If it's not already struggling on hills, then yes it will help, and I feel your pain. I doubt that's going to satisfy you for long, and a better route is to double the voltage and reduce the wheel size. I guarantee the fun quotient will go way up.

Personally I don't understand how anyone can ride a vehicle that is ridden always at WOT, so every puff of head wind or slightest uphill grade slows you down. If you want to cruise at a specific speed to match a pedal cadence, adhere strictly to a speed limit, or for whatever reason, simply add a cruise control. I've ridden my main bike at top speed on flat ground only twice just to find out it's to speed. I cruise at significantly lower speeds,, and my chosen speed is primarily dependent upon conditions. If I want to cruise at 35 and I get behind a dump truck going 35, there's no way I'm going to sit back there getting sandblasted. I also don't want to speed a week hung out in the other lane making the pass. I want to quickly zip around him and go back to the speed of my choosing.

John