battery questions

[doggydowg]

Hello all

Ive recently built my first ebay ebike kit, the seller says the battery is - Samsung 2900mAh Cells
- 12A Rated Current

1) its in a conceled black metal box, is it safe to open this box up and confirm the cells?

2)i was hoping to only charge once a day as i comute 7.5 miles each way and if i charge twice a day ie each way will this half my battery life? I dont want to be buying a new bat every year.

i had 1 out of 4 bars left this morning so pedalled hard up hill in fear of having to ride the rest of the way to work.with no charge lol.

3) if i am going to charge my bike each way 7.5 miles what is the highest amps i could mod my controller to run with the battery cells i have? Currently have a 22amp controller.

I try and pedal along and keep a steady 20mph all the way to work apart from paths and built up areas.

my motor is a 1000watt and battery is 48volt 10ah i weigh 12.5 stone.

thanks for any tips.

 

[danielrlee]

Hi doggydowg. Here are some brief answers to your questions.

1) Sure, I don't see why not. Make sure you have disabled the self-destruct function first though.

2) Lithium batteries will give the longest service life the sooner you are able to charge. Charging twice a day will prolong the life of your battery. Discharging to 100% is a sure fire way to shorten the life of your battery.

3) You already stated that your battery is rated at 12A. Running it with a 22A controller will not be doing your battery any favours. I would say you are already over the recommended discharge rate.

 

[dogman dan]

12 amps rated current is a bit small for a 22 amps controller. This is typical, they compete for price by undersizing the battery, and they know you will need a battery every year.

So what can you do about it? ride slower.

FWIW, you will likely use less than 12 amps, if you keep your speed below 32 kph on the flat parts. Pedal hard up the hill, because you will likely be pulling about 18 amps then. If you can still make 20 kph up the hill with less than full throttle, do that.

Lastly, are you sure its rated 12 amps? Or is it 12 amp hours in size?

 

[riba2233]

Battery is 10Ah (realistically 11Ah if it's 4p, or 8.25 if it's 3p ), and if the cells are really Samsung 29E, then the continuous rate is 10A, and peak rate is 3C (datasheet). However, cells wont mind 2C continuous discharge, but it's not great for cycle life.

 

[doggydowg]

Thats good news that i can charge both ways and it wont decrease the life of the battery. if I wanted to run 30amps
Or what ever my 1000watt motor will take what battery and budget for ready made should i be saving towards for when this battery gives up?

My battery is 10ah and the seller said it was rated to 12amp but without opening it i wont know what it is.

ive read the faq in this section and most of it just went over my head, so all the people that do shunt mod on controllers run better spec batteries then me?

If it makes any difference I only traval 7.5 mile and dont exceed 20mph but do like the idea of getting there quicker especialy crossing busy roads etc or getting out of a sticky situation.

 

[dogman dan]

I still have no clue what you have really. What voltage? Most 1000w kits run 48v, so I'm assuming you have that.

Cruising 20 mph takes 400-500w for most people. So that's about 10 amps, (if 48v) and safe for your battery if it only allows 12 amps continuous.

If you want to do the shunt mod, you will need to increase the size of your battery, so each cell sees les amps. If you ride fast, it will take a lot more than 12 amps.

Pedaling hard the first 20 feet at stop signs will also help lower your amps.

 

[doggydowg]

Hi its 48volt motor, I am charging both ways so every 7.5 miles and according to my batery gauge which I know wont be that acuret I use between 1 out of 4 bars and 2.

I can ride to and from work on one charge but probably am dangerously low on battery power.

I was contemplating building a 2nd ebike and a guy from ebay has been advising on parts to build a fast bike he recommended these,

https://www.hobbyking.com/hobbyking/store/__16227__ZIPPY_Flightmax_8000mAh_5S1P_30C.html

Il start another thread asking about this but this is probably where I am heading towards, I probably did make a bad choice in the kit but it was only £460 and I have already racked up 106 miles in just under a week that otherwise would have been in a car and sat in hours of traffic so the kit will soon pay itself off lol.

 

[Ykick]

You don't need a new thread.

I've ran Zippy/Turnigy RC Lipo over 5 years and will never buy/use Zippy brand again. I'm also suspicious of 8Ah bricks - when it comes to RC Lipo I want the freshest stuff produced in the greatest numbers. Not some oddball low production count stuff.

Personal favorite is Turnigy 4S 5Ah 20C Hardcase assembled in 12S, 16S, 20S configuration(s). Of course, 16-20S requires controller upgrade. Install a decent BMS and use a bulk charger.

 

[doggydowg]

Thanks YKICK

What is wrong with the batteries that were suggested to me out of intrest?

I am looking at buying a crystalyte hs3540 a 70amp controller and getting a 72volt battery, the link that I posted above apparently all I have to do is buy 4 packs of them and connect red to black wire on the 4 blocks, buy a ballencer charger which I wasn't sure of which one and a normal bulk charger same again?

That seems too easy, if I was to buy a cycle analyst 3 would that remove the bms aspect so resumably it can keep and eye on the voltage to make sure I don't run too low?

Also the seller of the hs3540 has offered to fit a thermistor in the hub so I can keep track of the temps im assuming this will just plug straight into my ca3?

Does the above kit look like a good wknd toy im in no rush to build my second ebike so I will ask lots of questions and reaserch this on more, thinking of selling my scrambler to fund this project although money isn't realy an issue

thanks for imput.

 

[Ykick]

Maybe nothing's wrong with them but based on my experience I don't trust Zippy brand. Sorry, I don't have any experience with Cystalyte motors/controller. I try to speak about things I've personally witnessed and used. I've never used the 8Ah bricks so maybe they're great but I'm also fairly certain they're not produced at the rate and numbers 5Ah pouches are produced.

Relying on any pack voltage based LVC (CA, controller) is foolish and asking for trouble. When a single cell drops above/below accepted voltage range cells will likely suffer from the imbalance. What's needed is a BMS or alarm which monitors individual cells and either shuts everything down and/or alerts you to a problem before it becomes a danger to yourself and others.

 

[dogman dan]

It's sort of just that simple. Unless you screw up and burn your house down, or weld your hand to a connector. But for a high performance bike, RC packs do have the c rates to handle your controller. The problem is, they are so cheaply made. 20c zippies, with a real world practical c rate more like 5c, won't cut it for a performance ride with 70 amps controller. You need better grade packs, 30-40c turnigy, or better. 8 ah of 20c zippy will sag like grannies tits when you open up that throttle. Fine for a 20 amps commuter, not fine for a flyweight motorcycle.

72v 8 ah will be very fun to ride, but you won't go all that far on that size battery.

Once you start to boogie around at 60-80 watt hours per mile, a 576 watt hour battery like that won't last very long. Theoretically 8 miles, but since a lipo pack gets wrecked fast if you discharge it too deep, you will have a practical real world mileage from that pack of about 5-6 miles at full speeds.

You do need a CA, or other decent watt/voltmeter on a lipo pack. You need to know what's happening so you don't screw up. Screw ups can cost many hundred dollars. A voltage read out is the bare minimum.

 

[doggydowg]

Thanks for the replys so turnigy batterys is the way to go, that's good to know as that would have been about £2-300 wasted lol.

Can I buy off the shelf bms for turnigy batterys, I have absolutely no idea about any of this stuff by the way I tried watching a video on how to build batterys and watched some kid stripping apart laptop batterys for 20 mins and soldering them altogether, id be buying it pre solders and hopefully ready to plug in if at all possible?

Ive tried searching for 72volt battery packs in this country and I cant find any maybe for liability reasons or im just looking in the wrong places ( I live in Enland)

I wont be flat out everywhere you just couldn't get away with it where I live, there are some single track country roads I could open it up for about 2-3 miles the rest would just be poodling about 15-20mph so im hoping 8ah would be enough in any battery technology as im hoping to do away with wanky panier battery they a pita and make my bike handle like a shopping trolley.

Im going to google the turnigy battery packs for today, maybe I biter the bullet and pay someone off this forum or from china to build me a complete battery with bms built in with a charger etc what kind of cost would I be looking for this if this is evan an option?

Thanks guys

 

[Ykick]

Maybe a reasonable way for you to get into the RC Lipo game is to assemble a small "range extender" pack? That way you're not relying on it as much but gets you accustomed to purchase, cell qualification, series/parallel wiring, connectors, charging schemes, alarms, etc.

Many of us have been buying BMS from bestechpower and installing them to help make bulk charging a little safer. But without some previous RC Lipo experience It's not particularly easy to wire up, understand and employ a BMS out of the gate. That's why I wonder if a small "starter pack" could help you get up to speed with the usual RC chargers and cell alarms until you better understand how to construct a BMS protected eBike pack from RC Lipo bricks?

Small steps...

 

[dilkes]

Many of us have been buying BMS from bestechpower and installing them to help make bulk charging a little safer. .

How do you actually buy/order one of these BMS's from bestechpower? I was on the web site, but don't see any prices or ordering instructions.

 

[doggydowg]

Thanks YKICK

Small steps indeed sounds like I need to do an electrical course to build this battery lol, I can do basic soldering, but better then that my mates old man used to do small pcb board solering etc for a job I once got him to solder a bigger resistor in my ecu on a car to raise the rev limiter.

With some help from you guys perhaps he would be able to assemble the battery pack to save me potentially burning the house down or welding my hands to a battery lol.

From what ive seen on hobby king the packs can be bought all assembled in shrink wrap with just a red and black wire coming from each block, what exactly do I need to do from here with the turnigy packs then?

Just to add I don't expect to be breaking any world records Id be happy getting anything above 35mph I doubt id be able to build anything exceeding 35mph and don't realy want to go over 40mph if that's evan achievable as lets be honest it is a pushbike at the end of the day, ive ridden fast motorbikes but to be honest evan at 30mph this seems much more fun and relaxed and loving the fact there are bus lanes and bike lanes that I didn't evan realise were there. Normaly I sit in traffic for 45min just to get 2 mile down the road im now getting to work in 30-45 mins ;_)

Got a bit off topic there keep the info coming ;_)