36V Charger

[camerart]

Hi,

I've just received 10 5000mAh 3S batteries from Hobbyking, for building a battery pack 3X3. Each cell has a balance wire.

I now need a charger. Any suggestions please. Hopefully one that can be used from the mains.

If this topic has been done to death, I'll be happy with links to the pages.

Camerart

 

[Deleted member 4366]

You'll need a balance board for that lot, any 6S lipo charger and a 12v power supply. Most people start with a imax charger, but only buy a genuine one, which you can get from Hobbyking along with yhe balance board. You can modify an old PC power supply for 12v if you have one.

9S3P is a strange configuration. Is it for a 24v motor?

 

[camerart]

You'll need a balance board for that lot, any 6S lipo charger and a 12v power supply. Most people start with a imax charger, but only buy a genuine one, which you can get from Hobbyking along with yhe balance board. You can modify an old PC power supply for 12v if you have one.

9S3P is a strange configuration. Is it for a 24v motor?

Hi D8,

I've ordered a Turnigy Reaktor 30A 1000W Balance Charger from Hobbyking, after looking till I was goggle eyed. I got the idea that it would be good to have a charger capable of balancing my 9X3 cells = 36V. I read that they are re-packaged iChargers, but time will tell.

A strange configuration? Have I calculated incorrectly? I thought that 3X 3S =36V which is what I need. Any way it's done now £230 later

I will figure out the power supply as I go, I think eventually I need 24V and quite a lot of Amps to run it properly, but that will be later. At the moment, I've got an Imax B8+ charger, so time consuming. (Till my charger comes)

C.

 

[Deleted member 4366]

10S is 36v. Each cell is nominally 3.7v, so actually 37v. Most people go for 12S because most 36v controllers will work OK at that voltage and you get 20% more power. What will you use as a power supply?

 

[awol]

How about using them as 4x2 to get 12s2p 44v 10a with 2 batteries left over as spare.

 

[camerart]

Hi,

When you say "more power" d8veh, I assume you mean more speed, but not more range. So far I've tried 3X cells in series, as a test and it seems fine to me, as a little push when I need it. I want to be able to go round a 30mile circuit, and it's just a bit too far for me to enjoy without help.

With no experience of how much balancing cells needs to be observed, I went for a charger that can balance all of the series of cells at the same time.

I'm looking into power supplies, and have an old microwave that might be able to put of 25V 30A,if I re-wind it. I'm just looking into it. I've also seen this: http://www.ebay.co.uk/itm/281600624877?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT.

I can try 48V later perhaps.

C.

 

[Deleted member 4366]

You can use a server power supply to give 12v at up to 30 amps. You have to do a slight easy modification. Use Google to get the details. You can get them ftom Ebay for not a lot.

Increasing from 9s to 12s will give 33% more torque and it will allow the motor to spin 33% faster, so you get more choice of speed. The torque can then be applied at higher speed, so you get 33% more peak power. Peak power comes at approximately 2/3 maximum motor rpm and peak efficiency at about 3/4. Choice of motor winding and voltage is important to get the best efficiency and most suitable power.

Range depends on the total number of watt-hours in your battery, though efficiency also has a bearing. After that, come the user factors, like speed, hills and weight.

 

[camerart]

You can use a server power supply to give 12v at up to 30 amps. You have to do a slight easy modification. Use Google to get the details. You can get them ftom Ebay for not a lot.

Increasing from 9s to 12s will give 33% more torque and it will allow the motor to spin 33% faster, so you get more choice of speed. The torque can then be applied at higher speed, so you get 33% more peak power. Peak power comes at approximately 2/3 maximum motor rpm and peak efficiency at about 3/4. Choice of motor winding and voltage is important to get the best efficiency and most suitable power.

Range depends on the total number of watt-hours in your battery, though efficiency also has a bearing. After that, come the user factors, like speed, hills and weight.

 

[camerart]

After I receive the charger, I can read how it all works, I think it needs 24V, but will work on 12V.

I'll be able to try different power supplies, I have, including batteries, once I have it.

Regarding range, which is what I'm after. Are you saying that running at 3/4 full speed, is more efficient than 'say' walking pace? I'm medium weight, there aren't many hills round here, and I don't mind pedalling

I'm waiting for connections to parallel 3X my 3X series batteries. So far I've tried 1X 3X pack and got about 5miles. This X3 will power me 1/2 way round the aimed for course, which seems about what I'm aiming for. I'm sure I can improve, once I get the charging more precise.

C.

 

[Deleted member 4366]

After I receive the charger, I can read how it all works, I think it needs 24V, but will work on 12V.

I'll be able to try different power supplies, I have, including batteries, once I have it.

Regarding range, which is what I'm after. Are you saying that running at 3/4 full speed, is more efficient than 'say' walking pace?
C.

If someone were going at walkng pace at full throttle (startup of steep hills), efficiency could be as low as 30%. At 15 mph, it could be as high as 80%, so yes, you would get more range at the higher speed. That's why it's important to match your motor speed and power to what you actually need for your journeys.


It gets complicated when you reduce the required power from maximum by reducing the throttle or selecting a lower PAS level. In effect, the lower setting becomes a new maximum speed, so the 3/4 rule still applies, but at the lower speed. Let's say your motor could spin to 20 mph max, so half-throttle sets the speed to 10mph. Maximum efficiency would then cum at 7.5 mph.

It gets even more complicated when you use one of the modern controllers that use current control for the PAS. It's difficult to work out where highest efficiency comes then. I think at 15 mph regardless of PAS level in the above example, but that's a pure guess.

 

[camerart]

d8veh,

It is complicated! I tend to work better by experience. I did a test today. With almost balanced cells in the battery, I travelled 7 miles on 3X =36V batteries, @top speed 14mph. Does this sound somewhere near?

C.

 

[Deleted member 4366]

Do you mean that you used a 9S 5Ah battery and it was empty after 7 miles?

 

[camerart]

Do you mean that you used a 9S 5Ah battery and it was empty after 7 miles?

Yes.

 

[Deleted member 4366]

That seems a bit low on range, considering the low speed. Maybe get a cheap wattmeter to check what's going on.

http://pages.ebay.com/link/?nav=item.view&id=310925684854&alt=web

 

[camerart]

That seems a bit low on range, considering the low speed. Maybe get a cheap wattmeter to check what's going on.

http://pages.ebay.com/link/?nav=item.view&id=310925684854&alt=web

Ok. What do they actually tell you? What distance would you expect?

My charging and checking conditions, aren't the best at the moment, until I receive the charger that's in the post and set up a charging station. Then I will be able to monitor better. (I'm a bit busy with other projects, at the moment, so can't give this as much concentration as I would like). I just have the batteries in one pannier, with the controls in the other, that should be tidied up. As long as I'm not doing too much damage to the batteries, I'll carry on like this, while getting the feel for it, until I can do the above.

Had a really pleasant ride yesterday, as I said, which was worth the price of the admission.

C.

 

[Deleted member 4366]

The wattmeter is very useful when using lipos. it will show how much battery you've used, like a fuel gauge. It will show your pack voltage in real-time, your instantaneous power consumption and current. Yu will learn a lot about how your motor behaves. All the cheap ones are designed to go inline, so it's best to use a remote shunt so that you can mount it on your handlebars. If you get one, I'll show you how to do that. You shouldn't use lipos without at least a real-time voltmeter unless you have lipo alarms fitted. Don't try and ride your bike if they go below 3.5v per cell. After that, they accelerate diwnwards rapidly into the danger zone, which catches out many people.

 

[camerart]

Hi d8,

I'll probably get one. So far I have monitored one battery with a plug into the balance connection, voltage gauge.

There is a gauge on the LCD screen, that I can tell when it is low, and I normally stop at 3.7, but I could go a bit farther to 3.5v.

(I'm studying how to tighten spokes at the moment, they came loose yesterday. I've got info and videos)

C.

 

[camerart]

Yesterday, I have a look through the Imax b8+ manual, to find
I had it not set correctly. I hadn't understood, CAP and FULL.

Now, from my understanding, each set of batteries (LI-PO?) has an approximate time, capacity and voltage, the setting of which can be stored in the charger, for charging that pack. These are for safety measures, so that the charger switches off, at one of these settings. Am I correct that the capacity of a pack, is what's written on it X the number of parallel cells, and the time can be estimated by experiment?

C.

 

[Deleted member 4366]

If it's anything like most lipo chargers, as a safety measure, you can limit how many mAh it gives or the time it charges for so that you can't over-charge your pack. When the limit is reached, you see Cap or time in the display. Only when it's completed the charge cycle and it decides that the cells are charged properly do you get "Full."

The default setting is always too low for ebike batteries, so you need to increase it. If you're charging two 5000mAh batteries in parallel, the capacity limit would be, say, 11000mAh. If charging at 2 amps, the time should be, say, 320 minutes. That's if it goes that high.

The charge rate always slows down at the end when it's trying to balance the cells, so you might have to set the time higher. Whatever you set it to, if you reach the limit, you can just press the start button again, but be mindful, that the limit is then reset, so have a quick look to see that everything is in order.

 

[camerart]

d8veh,

Yes, I was using it in the 'press and start again' mode, I follow now thanks.

C.