Overvolt Controller, bad for batteries,

[broloch]

Is it bad for the batteries to overvolt the controller?

For instance, if I have 60V 10Ah for the pack, and the controller is 'meant' to take 48V, is that bad?

When will the controller know to cut off the battery and stop discharging?

Maybe for the 48V controller, it will know to stop discharging a 48V pack when it reaches around 44V, or something.
But with a 60V pack, won't it run down to 56V, and still be above the controller's "Cut off point"?
Doesn't that mean the controller will keep discharging the battery?

noob here. Unless of course the 10Ah comes into play here too...
How does this work? :|

 

[Drunkskunk]

48 volt battery means 48 volts nominal. Depending on the type of battery, 60volts full charge is normal.

 

[broloch]

What I mean is if I take

Five packs of 12V 10Ah battery and wire them up to make a 60V pack, will the 48V controller try and suck the battery dry, overdischarging it, or will the controller know to cut off once the battery doesn't delivery a certain amperage?

I am using a Crystalyte 408 motor. Crystalyte 48V controller.

 

[Ypedal]

The controller has a fixed LVC ( Low Voltage Cutoff ), no matter what voltage battery ou plug in, the lvc is still the same.. so a 48v controller will have a lvc of 39 or 40v, if you use a 60v battery on this controller you risk overdischarging the battery as the controller will not adjust itself accordingly.

Typically it's quite obvious when a battery is out of energy and needs to be recharged, but you have to stop using the throttle.. like turning the key on your car and turning the starter over and over when you are out of gas.. hehe..

There are usually " resistors " you can swap inside the controller to adjust the lvc but this is for the more geekazoid types.

 

[broloch]

this is for the more geekazoid types.

This is our court isn't it, and the ball is in our court...

 

[broloch]

DSkunk,

how is the weather in Dallas?

Do you get a lot of gripe from motorists?

 

[Anonymous]

.

 

[broloch]

Just wondering what you guys thought...

a battery has a certain amp-hour...e.g. 4.2Ah

basically, the voltage drops as you use the battery, and so does the available amps

the ebike needs a certain amount of amps to run

so whether at 60V and 4.2Ah, or 48V and 4.2Ah, once the battery drops to a certain amp, the motor will stop working anyway...
and this point will probably be higher than the LVC anyway...am I right?

not really have damage to the batteries...

 

[dogman dan]

Lithium batteries? If so, you really ought to get a bms on them to manage lvc on a cell group level.

As for the controller, some have had issues with 36v controllers that run fine on saggy 48v sla or nicads blowing eventually when used with 48v lifepo4 that stays near 60 v longer. Usually these controllers, 36v or 48v will have 63 v caps inside. But running near their upper limit may not be so good for one with a defect of any kind.

As for bad for batteries, the basic procedure is to figure out what your general amp rate is. Easy with a ca, or it can be done close enough for a cowboy by seeing how close you get to one hour of riding at full throttle and doing some math. Then you look at the ah size of the pack and find out if you are in the butter zone for c rate. For example, riding full throttle on a 10 ah battery, the pack lasts for 1/2 hour. At 1 c amp rate, the pack would deliver 10 amps for one hour, so in this case the battery is averaging 2c. For pouch type lifepo4, this is near the upper limit for the pack lasting, or for typical round cells double the safe limit, which would be 1c. In this example the motor is averaging 20 amps over the whole ride.

Typicaly, a 408, will average about 15 amps or sometimes even less in cruise mode at full throttle, and more of course on hills or starts. To really have a battery that lasts, 10 ah is pretty much a minimum size for the lesser cells, like pings etc. 20 ah is of course better, and 15 ah a good compromise, especially in the 48v versions. The 48v 15 ah is usually a manegable size where carrying it is concerned.

Other batteries, fatpacks, headways, etc, can handle higher c rates and be a bit smaller. Nevertheless, they also will surely benefit in lifespan from c rates closer to 1 c than to 5 c.

 

[dnmun]

Just wondering what you guys thought...

a battery has a certain amp-hour...e.g. 4.2Ah

basically, the voltage drops as you use the battery, and so does the available amps

the ebike needs a certain amount of amps to run

so whether at 60V and 4.2Ah, or 48V and 4.2Ah, once the battery drops to a certain amp, the motor will stop working anyway...
and this point will probably be higher than the LVC anyway...am I right?

not really have damage to the batteries...

by 60V do you mean 5 SLA? that puts you at about 66V and if you have 48V controller then the caps are likely rated to 63V. they may last for awhile, or they may blow right away. but if you have the p75fn75 FETs then they will handle the voltage.

the input power resistors may be large enuff, but without knowing what their value is and what controller you have and the idle controller current it is impossible to establish whether that voltage is too high for the input to the voltage regulator.

kinda not enuff info to determine how to answer your question.

 

[Russell]

Just wondering what you guys thought...

a battery has a certain amp-hour...e.g. 4.2Ah

basically, the voltage drops as you use the battery, and so does the available amps

the ebike needs a certain amount of amps to run

so whether at 60V and 4.2Ah, or 48V and 4.2Ah, once the battery drops to a certain amp, the motor will stop working anyway...
and this point will probably be higher than the LVC anyway...am I right?

not really have damage to the batteries...

When talking about batteries you should specify what type, for example: SLA, NiCd, NiMh, Lithium (and what flavor of lithium), because each is different. There are basic concepts however that are common. Generally when a battery is rated 4.2Ah, as in your example, it means it can deliver 4.2A of current for 1 hour or 2.1A for 2 hours, etc. The exception to this is SLA batteries which are generally rated for a 20 hour discharge. All batteries will deliver current for less time if they are drawn down more quickly however the effect is far more prominent with SLA batteries. What this means is to get 4.2A for an hour from SLA's you would need to buy batteries rated at 7Ah. Whether a 4.2Ah battery can deliver 8.4A for 30 minutes or 16.8A for 15 minutes depends, as Dogman talked about, the 'C' rating.

In e-bike applications the actual current demanded from the battery at any time will vary from zero to the maximum rating of the controller. 20 amp controllers are common on ebikes but there is a wide range available, I use a 15A. The way I ride the average current I'm drawing from the batteries works out to around 2.7 amps per hour (at 48V). Those who have larger controllers and ride faster can easily use 2-4 times as much power so when determining your battery needs you have to discuss how fast and how far you want to go. For maximum life from your batteries you should pick a size which can deliver the power and range you need without stressing them too much. If you want more details from the board you should specify what type of battery you want to use and how you're going to use it.

-R

 

[broloch]

Regarding the battery, it is in NiMH chemistry.

The caps and FETs are rated for 100V, using a Crystalyte controller.

The motor is a 408. I would like to go a range of 10 miles, 20mph is okay, but I would prefer a bit faster, closer to 27mph.
So... a 4.2Ah being drained at 10A would probably only last for about 25 minutes?
Meaning that if I were to travel at 25mph, using 60V, I would only reach about 10.5 miles, maybe less than that because the battery output drops?

My current battery pack is 36V 4.2Ah NiMH. I want to add an extra 12V 4.2Ah to make a 48V, or even another one after that to make it a 60V pack.

I would love to have a Ping pack (LiFePO4, 10Ah ---$500 CDN), but I am also saving for a motorcycle, and have other costs as well, academic related. I own two other non elec bicycles. I train on those. I would like to use the ebike to travel the whole way in my other travels, (not joyride related, albeit all rides on bikes are joyrides, but for instances, where I have to commute somewhere it isn't so much a joyride), so that I don't sweat on my forehead and back when I arrive.

Thanks for the posts all about the batteries, I don't mean to ignore your posts, or that I am not answering them directly. I will do my best to answer what I can, but some of the info here is still a little too technical for me.

 

[broloch]

The "C" rating is not given.
The packs are made from sub C batteries if this information is related.

The max discharge is rated at 40A, not to discharge below 18V for a 36V pack...there are 30 1.2V cells...so no less than 18V/30= 0.6V per cell...when each cell puts out about 1.2V

But...won't the controller/motor require a certain Amperage of electricity in order to keep running? In terms of electrical pressure, once it is too low, won't the motor slow way down?

My current setup does this...on the 36V NiMH 4.2Ah pack, the bike will cut power after a few miles. Is this likely the LVC, or the battery's electrical pressure giving up?
The controller is a 48V controller, LVC is probably 24-30V.
I haven't checked recently, but it was probably around 11.9V for each of the three 12V packs at the end of a ride (when the motor stops working), so maybe that answer the question

 

[icecube57]

I swear to god if you are using the 12v 4.2AH Nimh Tenergy packs as a battery pack. Its sounds like thats what you are using. I would smack you silly if u were next to me. All they are good for is booster pack. I need 4 in parallel to pull 40A and stay anywhere near 12v. I thought I could use it as a main battery but after doing discharge tests it quickly put that idea to an end. You wont get 4.2AH out of them so lets get rid of that wet dream right now. Realistically 2.5-3AH. One pack will not sustain 40A @ 12v. So 3 in series will have the voltage sag from hell with anything above 10A. So I already know that 1 pack will provide 40A @ 9-10v so if you have 3 it will be 27v-30v under load which is below the lvc of the controller already.

To run these packs on a 20A controller you will need two packs in parallel with 6 packs total for a 36v pack. It will give you around 5-6AH. The most Ive got from my packs was 60-70% down to 10v. The voltage really takes a dive after that indicating the battery is dead.

Here is a post with my test data on the packs that I ordered from All-Battery.com
http://www.endless-sphere.com/forums/viewtopic.php?f=14&t=10756
http://www.all-battery.com/sidebyside12v4200mahexpandablenimhbatterypackmoduleswithtwoconnectors.aspx

Here is the battery pack that you might have.
http://www.all-battery.com/36v4200mahnimhbatterypackfore-bikeandscooter.aspx

If this is the pack that you have then the packs I have are made of the same cells. If you want real data on these packs that use these cells read my test data post above. It will give you a very good idea on how the pack will perform.

You are not supposed to drain the cells below 1v because there is nothing really past that do. 30v would be more appropriate voltage to discharge to. Maybe they meant 28v. Where they got 18v on a 36v pack is beyond me.

 

[Russell]

Regarding the battery, it is in NiMH chemistry.

The caps and FETs are rated for 100V, using a Crystalyte controller.

The motor is a 408. I would like to go a range of 10 miles, 20mph is okay, but I would prefer a bit faster, closer to 27mph.
So... a 4.2Ah being drained at 10A would probably only last for about 25 minutes?
Meaning that if I were to travel at 25mph, using 60V, I would only reach about 10.5 miles, maybe less than that because the battery output drops?

My current battery pack is 36V 4.2Ah NiMH. I want to add an extra 12V 4.2Ah to make a 48V, or even another one after that to make it a 60V pack.

I would love to have a Ping pack (LiFePO4, 10Ah ---$500 CDN), but I am also saving for a motorcycle, and have other costs as well, academic related. I own two other non elec bicycles. I train on those. I would like to use the ebike to travel the whole way in my other travels, (not joyride related, albeit all rides on bikes are joyrides, but for instances, where I have to commute somewhere it isn't so much a joyride), so that I don't sweat on my forehead and back when I arrive.

Thanks for the posts all about the batteries, I don't mean to ignore your posts, or that I am not answering them directly. I will do my best to answer what I can, but some of the info here is still a little too technical for me.

Well the good news is your controller sounds like a good one; the bad news is your present battery pack sounds woefully inadequate. Much however depends on the maximum current your controller allows. I use a 36V 6Ah LiMn pack plus a 12V SLA booster with my 36V controller which has 63V capacitors with no problems. I get good range even with minimal pedaling, 18.2 miles at 18.0 mph, but I get that because I have a 15A controller and I keep the speeds reasonable.

If you want to experiment on the cheap by adding the SLA boosters I'd say go for it. Since you say your controller is a 48V version it will not have a problem with you adding a 12V SLA to your present 36V NiMh pack. Be sure to get a 7Ah-9Ah SLA since Lead-Acid batteries deliver only about 50-60% of capacity when used on ebikes. My 9Ah booster died after 4.7Ah today. You should be able to manage low 20 mph with one booster but for how far I couldn't say...just try it. As your controller has 100V caps I would think adding two SLA's would not be a problem but hey start out slow.

After you've had some fun with your present pack and the boosters you'll inevitably want to upgrade to a nice lithium pack, so keep saving

-R

 

[broloch]

I swear to god if you are using the 12v 4.2AH Nimh Tenergy packs as a battery pack. Its sounds like thats what you are using. I would smack you silly if u were next to me.

Why do you want to slap me silly? Are you mad at me? Did I do something wrong?

 

[icecube57]

I was just playing with you when I made the comment earlier. Dont take it personally.

Add a 12v booster pack to give you 48v. Those cells will put out but they sag like hell under load. The booster pack help you stay above the lvc of the controller. The controller will be fine because the actual working voltage will be much lower than 48v. More like 38-40v. The mosfets should be good to 100v maybe and the caps should be 100v.


Also you will need to get a Watts Up meter or a Standalone Cycle Analyst. This will help you keep any eye on you voltage and your AH consumption. Also at 48v the lowest I would like to see on those packs is maybe 38-39v resting at the end of the discharge and no lower than 36 under load. And thats a generous range. 40v should be the cut off on a 48v pack and maybe 38v being absolute lowest under load. With those Tenergy Sub C cells everything that we normally apply to NIMH goes out the window because they are so crappy. You kinda gotta bend the rules on those packs.

 

[dogman dan]

Yeah, start saving for a ping, or some headways, bosh fatpacks, etc. It sounds like your current pack is not going to be around very long. It's just too small, and the cells are getting hammered.