Integrated Battery switching??? (2 batteries)

[joby1]

Hello,

I am running cyclone motor with a 48v 20ah battery, I am planning on getting another additional battery sometime in the near future.
I am using the triangle bags for both and would like to have both on bike at same time, as it would be a real pain removing either battery or taking the bags off.

I have been thinking alot about running 2 batteries, and migh run them parallel, but dont really want to get another 48v, and not sure if I would want to spend the money to get 2 new higher voltage batteries or even 1 BIG battery.

Playing with the idea in my head of just getting like a 60v or maybe even 72 volt for this bike AND having it wired on the bike with the 48v also still in play.

I am sure that I could somehow wire up a switching system that would make it really easy to switch from one battery to the other. Anyone done this?

As the bike is set up now it would be a real pain to have to disconnect one battery and connect a different one manually,,, The idea of just using a switch to switch back and forth is ideal, looking for ideas...if anyone can help....

Thanks
J

 

[joby1]

I know they have switches for marine that you can choose #1 battery or #2 battery, (probably even more) OR to have both batteries on (which I know would have to be the same voltage batteries).

Maybe the other option is just to have 2 switches, one for each battery, kill one, turn on the other..??

ideas?

 

[Voltron]

A big question would be can your controller switch between the voltages... also, if they are both independently switched, there's a possibility somebody might accidentally switch them both on at the same time, which would be bad with two different voltages, which also goes for most of the boat type switches as they usually have a common ground. The 2 different voltage thing makes it a lot more complicated. Plus a benefit of same voltage paralleled is that each cell suddenly aren't getting worked as hard as the load gets shared, so if you're carrying the battery weight, may as well have them both hooked up unless you have BMS conflict problem.

 

[joby1]

Thanks for the response, makes a lot of sense, although I am only one messing with the bike and am pretty sure I can keep the switching straight personally...

I have cyclone motor "3000" / controller, supposedly it can run from 36v to 72v.

I was thinking of doing the higher voltage most likely a 60v, because I dont really need 72v


and dont want to burn anything up or break stuff just to have a little more fun.

I am hemming and hawwing on whether to just get another 48v...even though I dont really need to go over 30 mph, the allure of the higher power from a higher voltage battery is in the back of my mind, plus I will be running with an axiom trailer at times as well, although no really huge hills around, and it wont be LOADED up...etc..etc.

Mostly what is holding me back from just deciding is that I made a quick decision on the 48v and now maybe dont want to pin myself down to the 48v system, it was what I could afford at the time of the build.

either way I want to get a bigger battery in AH so I can increase the range considerably, as it gets warmer here, I will be riding a lot more and further out. I am not driving a car right now and the bike is what I use to go places with currently.

A little thinking to do, I was figuring I could get like a 60v 30-35ah, and use that, then turn on the 48v 20ah as sort of a "reserve" battery, but you are right in the fact that if I just got r 48v I could use them both at same time and take it easier on each battery...

hmmmmmmmm.....

 

[joby1]

another post from me on Electricbike.com, if anyone can help with either topic, I appreciate it..


Lets say I have 2 batteries and one is 48v and the other is a 60v, both 20AH, so one is 960 wh and the other is 1200 or so wh,

Lets say I was to drive the bike in the unlocked mode and hover around 15 mph fairly consistently , I know there are more wh hours in the 60v battery so it would go further than the 48v.
I guess the question I am pondering on, would there be any beneficial gains due to something other than more wh capacity with the higher voltage?

I assume (maybe incorrectly) with the higher voltage battery, that the controller would also draw less amps to maintain a constant speed due to lower throttle required. So in simple terms it seems rational to think that the 60v would yield more WH AND draw less overall amps to perform at the same level as the 48v, providing a sort of double bonus in extending range..

Is this way off base? My first ebike .

I will most likely get additional battery in a few weeks, just trying to wrap my mind around the pros and cons of the higher voltages that the motor can supposedly handle.

:

 

[Pinesal]

I've done it with an extra 6V battery. I added a three way switch to add it in. One ways is 48V, the middle is off and the other way is 54V.

I made a diagram of my set up. The six dots are the three-way switch,

https://endless-sphere.com/forums/download/file.php?id=202384

 

[dustNbone]

I would be very, very careful to design such a system so that both batteries cannot at any time, under any circumstances end up connected in parallel if one is of a higher voltage than the other. The result of such a misconnection would likely not be immediate, and you might not even notice until the lower voltage battery catches fire in a really big way, due to being charged either too much or too fast.

This is not something I would trust myself with, not because of the likelihood of a mistake but because of the consequences of one.

An A/B switch should be OK provided it's rated for the highest voltage, and the maximum system amperage you expect to pull through it. You should be fine switching only the positives, common ground doesn't look like a problem to me, but I cannot stress enough the need to avoid having those two batteries in parallel.

Big fire. Hot fire. Please no.

 

[joby1]

yes no explosions or fires needed

I've done it with an extra 6V battery. I added a three way switch to add it in. One ways is 48V, the middle is off and the other way is 54V.

I made a diagram of my set up. The six dots are the three-way switch,

https://endless-sphere.com/forums/download/file.php?id=202384

so this was in series, just to add a little more voltage?

 

[amberwolf]

The result of such a misconnection would likely not be immediate, and you might not even notice until the lower voltage battery catches fire in a really big way, due to being charged either too much or too fast.
<snip>

Big fire. Hot fire. Please no.

This has happened to ES members before; I believe BikeFanatic had it happen with an RC LiPo pack. (3s & 4s accidentally plugged together)
https://endless-sphere.com/forums/viewtopic.php?f=14&t=46921&hilit=fire

 

[joby1]

all good stuff, thanks for the replies

 

[Samd]

Easy to just swap your two packs out with xt90 antispark connectors


Sent from my iPhone using Tapatalk

 

[DrkAngel]

On/Off/On switches work fine .
Cheap ones are rated up to 30A. (But confirm voltage rating!)
Rig with common ground, left terminals to battery #1 positive center terminals to controller right terminals to battery #2 positive.
#1 battery/Off/#2 battery
Fuses for both batteries!!! (switch function failure could be a spectacular! - from different voltage batteries)

 

[ferret]

I assume (maybe incorrectly) with the higher voltage battery, that the controller would also draw less amps to maintain a constant speed due to lower throttle required. So in simple terms it seems rational to think that the 60v would yield more WH AND draw less overall amps to perform at the same level as the 48v, providing a sort of double bonus in extending range..

That is incorrect.
Simply put speed is effected by voltage and acceleration is effected by amperage.
To maintain the same speed the motor needs an equal amount of Watts, Volts and Amps.
When you use less throttle the motor "sees" lower voltage.
Higher battery voltage will allow higher top speed and higher amp draw (unless limited by the controller or BMS).

If you change the gearing/wheel diameter so that the same throttle position will give the same speed, then the motor will draw less current with the higher voltage.

If you are interested in more details about how and why the controller effects voltage not amps at part throttle, check out this page about Pulse Width Modulation:
http://www.electronics-tutorials.ws/blog/pulse-width-modulation.html

Avner.

 

[dogman dan]

One,, to switch batteries unplug one, plug in the other. Simple, foolproof.

As for higher voltage being more efficient, not really,, at a given speed, wind drag from weather, grade, and weight of bike, you will use x watt hours per mile. You won't magically change any of those variables by changing voltage. And since a watt hour is a watt hour,, it will take the same x watt hours per mile.

 

[joby1]

thank you for the links and all the posts/ideas. Makes sense, Will do more research as well. any more input is appreciated of course...

I like the idea of a switch because everything (wiring) is hidden currently , I have not unplugged the battery since installation, it has the charge port on the bag.. It would not be hard to get everything exposed though, I suppose.

I have a little time to ponder on battery choices, Although the smart thing for me would probably just be to get another 48v really, and hook them together to take the load down,, I dont really NEED more power, just want it .

The next projects are the lighting / horns and such, taking down to 12v,running front / rear turn signals, headlight, brake light/tail light and probably some sort of LED strips for marker/increased visibility.

 

[Marin]

Once you get a switch with enough voltage and amperage it is quite large and clunky to mount on a bike. I have 2 nice marine switches and a skidoo switch I have bought and not mounted. They are kinda too big, even for my
Luna bike.

I have made a Y harness between my controller and battery or batteries one one bike. The bike in the photo I put a double Anderson connector on the controller wire and plug both batteries in there. Easy simple.

Once you parallel your 2 batteries you won't want to use them separately anymore. It's that good with either no or way less sag.
I do unplug one and charge
them individually.
I have 52v 25r 15ah, and 52v 25r 10ah in parallel.

The weight is ok on this bike but my other one same batteries is a bit too heavy.

You'll be satisfied with another 48v battery just by quality.

 

[Sunder]

The switch that DarkAngel mentioned is one like this:

With the central position being open for both circuits, it is impossible to then short the two batteries together. That model only does 10A, but should be very easy to rig up relays that handle much more. Or, as DA said, many are available at higher ratings.

When you use less throttle the motor "sees" lower voltage.
Higher battery voltage will allow higher top speed and higher amp draw (unless limited by the controller or BMS).

I know you put the word "see" in quotes, but I don't think it's close enough to justify that statement. Electrically there is a large difference between say, 24v @ 100% load, and 48v @ 50% duty cycle under PWM.

The motor still "sees" 48v, but only 1/4 of the time. The problem with that, is that motor efficiency is a function of the percentage of top speed. So a motor running at 100% of its top speed, is more efficient than the same motor running on 50% of its top speed, from having a higher voltage.

Here is the ebikes.ca simulation:



Although the difference is minor, the higher voltage motor run at 50% throttle, is about 5% less efficient. You should also note that the higher voltage motor has more torque and power. This is not from battery sag. It is because a motor is an inductor, and therefore has a rate of change of current - higher voltage = higher current ramp up.

 

[amberwolf]

I like the idea of a switch because everything (wiring) is hidden currently

If you don't mind the bulk, there's an "easy" and cheap battery cutoff switch that can be used to turn each battery on and off, but it takes one for each pack, and there can be a measure of safety in that you cannot turn a switch on without it's key, so if you only keep one key with you, you have to take it out of one (turning it off) to put it in the other (to turn it on).

I'm only using one (US General?), as a master switch, but it looks like this on my SB Cruiser trike:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1257233#p1257233

Others ahve used them on their "normal" bikes as well; not sure what search terms will pull up pics of that though.

Although the smart thing for me would probably just be to get another 48v really, and hook them together to take the load down,, I dont really NEED more power, just want it .

I can sympathize...but I recommend going with a pair of same-type packs, so that as they age you can use them in parallel. (because at some point they'll have enough voltage sag under the power levels you'll be using by then that using either one by itself would just cut out at heavy load, but using both in parallel would probably work fine. Can't do that if they're different voltages. )

It's part of why I have been using just 14s packs (except for one 16s LiFePO4 pack, which is about the same as the other chemistry's 14s, so it works in parallel).

The next projects are the lighting / horns and such, taking down to 12v,running front / rear turn signals, headlight, brake light/tail light and probably some sort of LED strips for marker/increased visibility.

[/quote]
Teklektik has a good thread about wiring up brake lights, turn signals, etc., if you look thru his posts. His uses all new stuff, and has p/n's and places to order from, etc.

If you like reusing old stuff, or repurposing things for stuff they were never meant for you can look thru my SB Cruiser thread (and the CrazyBike2, DayGlo Avenger, and Delta Tripper threads for more). Pics below from same link as above:


(headlight isn't turned on, so you can see all the other lights better)

 

[DrkAngel]

Sample switch:

Ui 690V Ith 50A ON/OFF/ON Position 8 Terminals Rotary Cam Changeover Switch <$25

Positive duo-pole changover with center disconnect



or
If bulkiness not a consideration:

60Amp Rain Proof Reversing (or changeover) Drum Switch ~$16



Alternate ~$10

 

[joby1]

thanks for all the replies, appreciate them all...
Joby

 

[joby1]

Teklektik has a good thread about wiring up brake lights, turn signals, etc., if you look thru his posts. His uses all new stuff, and has p/n's and places to order from, etc.

If you like reusing old stuff, or repurposing things for stuff they were never meant for you can look thru my SB Cruiser thread (and the CrazyBike2, DayGlo Avenger, and Delta Tripper threads for more). Pics below from same link as above:

Thanks!! I have already bugged Teklektik with 3-4 private messages, and he has been very helpful...I will check out your threads as well

thanks again
Joby