BMS or Hobby Charger

Batteries, Chargers, and Battery Management Systems.
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brianjonesphoto   10 µW

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BMS or Hobby Charger

Post by brianjonesphoto » Jun 14 2018 6:58pm

Hello I’m new to the board, but it’s been a great resource for my Lipo project. This is for my son’s OSET 36v electric motorcycle I’m replacing the aging 3 series connected 12v10ah SLA batteries with lipo.

I have 4 turnigy 5s 5000mAH packs that I’ve configured in a 10s2p set up. I’m trying to decide if I should use the Battery support 60A BMS I ordered or if I’d be better off with a quad channel hobby charger. After reading about storage voltage and also noticing the low voltage cutoff of the BMS I’m a little concerned that the BMS will make life more difficult than simpler.

I am using a Kelly KDS36100E programmable speed controller and have the voltage cut off set at 32v so I hopefully the ESC will cut out before the 2.85v of the BMS. The fact that the cut off of the BMS is below the danger level (3.0-3.2v) of a lipo worries me. I have the max current set to 30A contentious/50 burst for now as he get more skilled I will likely increase the limits. The controller is rated for 60/100 amps. There is also a relay and 45amp fuse protecting the everything from the battery. So there are already some protections from a short on the bike side, but the battery it self would not be fused which is pretty normal in the RC world.

Since this is something that will only be used at most a few times a week I’m always going to need to be achieving at storage voltage somehow. I’m pretty sure the BMS will not balance below a 39V charge not to mention I haven’t been able to find an adjustable power supply that costs less than a quad channel balancing charger.

So I’m at a crossroads. Do I call the BMS a loss (maybe try to sell it to someone here if I’m lucky) and run the batteries with low voltage alarms and the ESC cutt off as safety measures while investing in a decent hobby charger? Or use the BMS and 42v5a power brick I’ve already sourced for this project? Maybe a 3rd option would be the 0-60V 5A lab power supplies available on Ebay and return the brick.

Like all project as I learn more the more I realize I don’t know. I want to do this safely and right now I’m thinking that not using the BMS might be the safest route which goes against everything I knew at the beginning of this project.

Thanks in advance for your time and knowledge.

Brian

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eee291   10 kW

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Re: BMS or Hobby Charger

Post by eee291 » Jun 15 2018 4:16am

I would go with the BMS route.

first a cheap charger like this will do the trick: https://www.ebay.com/itm/Electric-Bike- ... Swq4la9~6h
or
https://www.ebay.com/itm/36V-2A-Liion-b ... FdVL4_zuMw#

And yes the Bms cut off is a bit low for a hobby lipo, but there is a way out.

Like you said, you can programm the Kelly to stop at 33V or 3.3V per Cell. Since you shouldn't rely on the Bms for LVC anyways.

Using that BMS with the charger is safer and simpler I'd say, since you don't need to mess around with the Balance plug everytime you want to charge your scooter up. Which for me can be daily.

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dogman dan   100 GW

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Re: BMS or Hobby Charger

Post by dogman dan » Jun 15 2018 8:31am

Heres the catch 22. The bms is what you want if you ride a lot, like daily. The charging individually with a hobby charger is a real pain to do often.

However, if you really really want max performance from those packs, you need to run then naked, or nearly so. This risks overdischarge, but having a handlebar mounted voltmeter can help reduce that risk. You can also identify which pack has the lowest capacity, and put a warning beeper device on just that pack.

Don't buy a quad charger, just get one higher wattage charger. Better one good 200w charger than four shitty 50w chargers in one box. You can charge away with the packs still in 2p 5s, so one way would be two larger chargers.

With more experience, many of us just run one bulk charger, so for 10p, a 250w 36v charger set to 41.5v, a slight undercharge, can work good. Balance manually, with a light bulb discharger, or balancing device.

Now for safety. After a "safe type" battery burned my house, my remaining lipo is definitely outside in a bunker. I was always careful with my lipo, but its staying outside forever now.

brianjonesphoto   10 µW

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Re: BMS or Hobby Charger

Post by brianjonesphoto » Jun 15 2018 9:00am

After some
More research and reading last night I'm going to go with a diy programmable power supply. With a made well knockoff 48v 400w power supply and a DP5005 controller. That should get me up and running for controlled charging for $50 and be slightly more portable than a lap power supply.

That way I can charge at 41.5v or 39 as well as using a hobby charger if needed.

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motomech   1 GW

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Re: BMS or Hobby Charger

Post by motomech » Jun 18 2018 12:52pm

brianjonesphoto wrote:
Jun 14 2018 6:58pm
Hello I’m new to the board, but it’s been a great resource for my Lipo project. This is for my son’s OSET 36v electric motorcycle I’m replacing the aging 3 series connected 12v10ah SLA batteries with lipo.

I have 4 turnigy 5s 5000mAH packs that I’ve configured in a 10s2p set up. I’m trying to decide if I should use the Battery support 60A BMS I ordered or if I’d be better off with a quad channel hobby charger. After reading about storage voltage and also noticing the low voltage cutoff of the BMS I’m a little concerned that the BMS will make life more difficult than simpler.

I am using a Kelly KDS36100E programmable speed controller and have the voltage cut off set at 32v so I hopefully the ESC will cut out before the 2.85v of the BMS. The fact that the cut off of the BMS is below the danger level (3.0-3.2v) of a lipo worries me. I have the max current set to 30A contentious/50 burst for now as he get more skilled I will likely increase the limits. The controller is rated for 60/100 amps. There is also a relay and 45amp fuse protecting the everything from the battery. So there are already some protections from a short on the bike side, but the battery it self would not be fused which is pretty normal in the RC world.

Since this is something that will only be used at most a few times a week I’m always going to need to be achieving at storage voltage somehow. I’m pretty sure the BMS will not balance below a 39V charge not to mention I haven’t been able to find an adjustable power supply that costs less than a quad channel balancing charger.

So I’m at a crossroads. Do I call the BMS a loss (maybe try to sell it to someone here if I’m lucky) and run the batteries with low voltage alarms and the ESC cutt off as safety measures while investing in a decent hobby charger? Or use the BMS and 42v5a power brick I’ve already sourced for this project? Maybe a 3rd option would be the 0-60V 5A lab power supplies available on Ebay and return the brick.

Like all project as I learn more the more I realize I don’t know. I want to do this safely and right now I’m thinking that not using the BMS might be the safest route which goes against everything I knew at the beginning of this project.

Thanks in advance for your time and knowledge.

Brian
First off, forget the BMS w/ LiPoly.
I don't get your math. 32 V(LVC) / 10(cells) = 3.2 Volts
I ran 2S/1P of Turnigy 6S/ 5000 mAh (20C) on a genaric controller w/ a LVC of 31 Volts for a while and what happens is this;
Below approx. 3.65V/cell, one or two of the cells start to stray downward, setting off the LVC around 3.2 or 3.3 V avg./per cell w/ some variances. I didn't much like the cells getting out of wack, so I went w/ 9S resulting in a LVC avg. of 3.5 or 3.6V w/ little cell variance, acceptable.
Your test is to run your Pack down to LVC, and check the cells. If the variance spread is less than, say, .5 Volts, they should come back together during charging and you are good.
My 9S system was for a "boardwalk bike", where my speeds were very low. When I moved back to "street" riding, I went back to 12S, a much preferable system because most controller's set LVC is 42 Volts and the resultant actual LVC is 3.65V/cell, or right before they start to stray.
At the other end of the cycle, charging, I bulk charge using a Mean Well HLG 320 series power supply and ck/balance(rarely) w/ Battery Medics. This is preferable because I don't have to "break the string" to charge. I have detailed my set-up many times and if you are interested, search my posts w/ key words like "bulk", "Mean Well", "Battery Medics", etc.
Although most of my LiPoly is the Multistar, I used Turnigy bricks for years and still have a couple. Great stuff, excellent value! The main reason I went w/ the Multistar was it used to go sale a lot and it's avail. in big capacity bricks like 10 Ah, 16 Ah, etc. Big bricks is the easy way to add capacity while retaining a 2P string. Going to a 3P string complicates bulk charging.
I should point out that using a Voltage alarm as an audio alarm is difficult. The stray cells taking a nose-dive when accelerating set the alarm off prematurely. I have used them as a visual tool and as such, they work well.
Motomech

'03 Rocky Mountain Edge 2WD 260 Q100H frt and Ezee V1 rear 2 Elifebike 20A & 25A 9-FET controllers 12S/20Ah Multistar Lipo rear 5Ah Turnigy frt Luna Cyclops Extra lite Alex 24DM rims, Crazy Bobs run ghetto tubeless. 25 mph. Mean Well HLG-320H-54A
viewtopic.php?f=3&t=83430
'07 GT Idive 4 4.0, Q100C 201 14S LiPoly elifebike 9-FET 20A controller. 23 MPH.
viewtopic.php?f=3&t=49691&p=1378484#p1378484

solveitnow   1 µW

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Re: BMS or Hobby Charger

Post by solveitnow » Jun 18 2018 9:15pm

Please help - I am new to custom battery building! I have a homemade 8S battery pack with 10 cells (18650 batteries) per pack. The total wattage (fully charged) is about 1200W - can I still use an iCharger 1010B+ (300W max) to charge it or should I buy a balance charger with a higher wattage spec? For example, the iCharger 3010B is 1000W max.

brianjonesphoto   10 µW

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Re: BMS or Hobby Charger

Post by brianjonesphoto » Jun 19 2018 12:22am

motomech wrote:
Jun 18 2018 12:52pm
This is preferable because I don't have to "break the string" to charge.
Does this have any functional meaning other than literally need to take the time to separate the paralleled packs from the the series? I assume there is no effect on the battery itself by splitting it apart to charge repeatedly.

Thanks.

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