smallest viable battery..

[thelarkbox]

Most of my regular ridding is short distances mostly downhill on the way out and uphill on the way home, so I dont need any ebike power until i return for the majority of my ridding. but when i do need it i expect im drawing the most current as its uphill

Looking for the smallest battery option i came across the thread discussing 36v powertool batteries but thats gone down a technical rabbit hole im not qualified to follow.

I found these on ebay/amazon

But I failed to see any mention of the max drain it could sustain in any ad,
iirc my controller is rated at 7a with a max of 15a? and 'eco' is registered in the headset as on.

The powertool thread which mentioned these batteries suggested they are limited to a 10a continuous draw

I had a quick google for hoverboard motors and they come in all power sizes but the basic cheap ones appear to be rated at 250w
but even if these could draw similar to my hub motor I cant imagine the controller would deliver it full on? but am just guessing now,

is there a way to determine the actual draw from my battery under load with just a multimeter and without destroying cables?
if 10a or less it would mean i could use one of these batteries safely ? assuming it is 10a they are rated for??

Or is there a smaller viable option, ideally small enough to remain installed most of the time stealthy .

 

[AGS]

You have to size your battery for the maximum that the controller can deliver and add a bit for safety. So if the maximum draw on your controller is 15 amps then you really need a battery that can deliver 20 amps.

Your motor is likely to be operating at over 500w uphill unless you are giving it a lot of assistance.

 

[StuartsProjects]

I have tried a couple of different types of those hoverboard batteries, a 4Ahr one and a 4.4Ahr on my electric Brompton. One battery has developed a fault, it cuts out at around 34V and is low capacity.

They work, although at the price (circa £50) clearly they are not using the best cells and the voltage sag under load might be an issue for you.

I had a 10S1P 5Ahr battery made with good quality 21700 cells and its a better performer than the hoverboard batteries. This is the battery on its holder;



To measure the current consumption voltage sag etc get one of these;



About £10.

Looking for the smallest battery option i came across the thread discussing 36v powertool batteries but thats gone down a technical rabbit hole im not qualified to follow.

The issue with the Bosch powertool batteries is that they dont have a conventional BMS. There appears to be no cut-out in the battery itself for temperature issues so unless the data produced by the temperature sensor on the Bosch battery board can be read somehow you wont have a battery temperature cut-out. Feel lucky ?

 

[saneagle]

I have tried a couple of different types of those hoverboard batteries, a 4Ahr one and a 4.4Ahr on my electric Brompton. One battery has developed a fault, it cuts out at around 34V and is low capacity.

They work, although at the price (circa £50) clearly they are not using the best cells and the voltage sag under load might be an issue for you.

I had a 10S1P 5Ahr battery made with good quality 21700 cells and its a better performer than the hoverboard batteries. This is the battery on its holder;

View attachment 53615

To measure the current consumption voltage sag etc get one of these;

View attachment 53614

About £10.



The issue with the Bosch powertool batteries is that they dont have a conventional BMS. There appears to be no cut-out in the battery itself for temperature issues so unless the data produced by the temperature sensor on the Bosch battery board can be read somehow you wont have a battery temperature cut-out. Feel lucky ?

Controllers nearly always have the max current written on them - no need to use a meter.

If you want o use a meter, you can figure out the current using Ohm's law. The voltage drop along any wire is proprtional to the voltage drop. Current = voltage drop/ resistance. Whatever wire you're using for the battery, you can look up its specific resistance (Ohms per meter). If it's 14g wire, the resistance os 0.001 Ohms for 6", so if you stuck your probes 6" apart, each milivolt you get on the meter would be 1 amp. If they were 12" apart, each mV would be 0.5A.

You can get the resistance of copper wire from this calculator:

Wire Resistance Calculator - Cirris Inc

www.cirris.com

 

[thelarkbox]

@AGS Thanks, I was wondering if the mysterious eco feature the headset displays might mean less power and thought if i could validate a lower than 10a draw.... At least i know enough to stop think and ask eh?

While i do contribute uphill, - not a lot atm as im just thrilled to roll up the slopes that i have been puffing up for way too long without e-power.. I may start dropping down the power levels after the 'honeymoon', no promises tho.

@saneagle, again my misunderstanding of the load demand and what numbers are relevant, tho Max amperage is a bit of a give away.. wishful thinking on my part perhaps.. I still recall ohms law ok but am rusty in its application, my requirement for the metric is now moot since the 15a max current of my controller exceeds the 10a of the hoverboard pack.

@StuartsProjects NO I do not feel lucky at all when it comes to batteries, Not at all.
that looks like quite a neat package? you say custom built, is the builder taking further commissions?..
the theory of battery building is one thing having a large enough sample of cells to select 10 with close to identical profiles after testing, and then spot welding and sourcing a suitable quality bms is more than i can take on comfortably.

After reading 2 pages and skipping to the 6th only to read about 4 byte data bursts which looks like its heading towards oscilloscope territory i backed away quietly with the intention of revisiting when the comms protocols have been determined, (google cant answer that yet?)..

an ebay special dc meter may find its way onto my bike soon too.

Thanks for your patience and taking time to respond..

 

[StuartsProjects]

NO I do not feel lucky at all when it comes to batteries, Not at all.
that looks like quite a neat package? you say custom built, is the builder taking further commissions?..

No;

eBike batteries have ceased trading

According to the ebike batteries website, Jimmy is in ill-health and so his business will be closed for an indefinite period. Let's hope he is able to return to good health - his battery re-celling service will be badly missed. Does the forum have an alternative recommendation for battery...

www.pedelecs.co.uk

 

[thelarkbox]

@StuartsProjects Cheers, thats a shame.. hope your man feels better soon..

Im currently reading through your build thread, great stuff thats quite a bike, I was ignorant of anything Brompton until when working a laboring job early 80's another lad onsite was a huge fanboy and filled us in on his plans to merge a in hub gear system with derailleurs,for the optimum city courier bike and oh boy did he lurve the inner hub gear system.. I know nothing about bikes but will never forget the name Brompton ..

 

[saneagle]

@AGS Thanks, I was wondering if the mysterious eco feature the headset displays might mean less power and thought if i could validate a lower than 10a draw.... At least i know enough to stop think and ask eh?

While i do contribute uphill, - not a lot atm as im just thrilled to roll up the slopes that i have been puffing up for way too long without e-power.. I may start dropping down the power levels after the 'honeymoon', no promises tho.

@saneagle, again my misunderstanding of the load demand and what numbers are relevant, tho Max amperage is a bit of a give away.. wishful thinking on my part perhaps.. I still recall ohms law ok but am rusty in its application, my requirement for the metric is now moot since the 15a max current of my controller exceeds the 10a of the hoverboard pack.

@StuartsProjects NO I do not feel lucky at all when it comes to batteries, Not at all.
that looks like quite a neat package? you say custom built, is the builder taking further commissions?..
the theory of battery building is one thing having a large enough sample of cells to select 10 with close to identical profiles after testing, and then spot welding and sourcing a suitable quality bms is more than i can take on comfortably.

After reading 2 pages and skipping to the 6th only to read about 4 byte data bursts which looks like its heading towards oscilloscope territory i backed away quietly with the intention of revisiting when the comms protocols have been determined, (google cant answer that yet?)..

an ebay special dc meter may find its way onto my bike soon too.

Thanks for your patience and taking time to respond..

If you really want a small battery pack, you can use lipos. They'll give all the current you need. You must use cell alarms to know when they're empty.

 

[thelarkbox]

If you really want a small battery pack, you can use lipos. They'll give all the current you need. You must use cell alarms to know when they're empty.

Ahh I was wondering where the obvious cross over between the RC bods and the ebike bods would be my money was on esc s

Yikes 10s charges are not cheap!! theres the catch eh..

 

[saneagle]

Ahh I was wondering where the obvious cross over between the RC bods and the ebike bods would be my money was on esc s

Yikes 10s charges are not cheap!! theres the catch eh..

You use two 5S or 6S packs!!!

Turnigy 5000mAh 5S 30C Lipo Pack w/XT-90

Turnigy 5000mAh 5S 30C Lipo Pack w/XT-90. Turnigy batteries are known the world over for performance, reliability and price. It’s no surprise to us that Turnigy Lipoly packs are the ones to use for those in the know.

hobbyking.com

 

[thelarkbox]

You use two 5S or 6S packs!!!

Turnigy 5000mAh 5S 30C Lipo Pack w/XT-90

Turnigy 5000mAh 5S 30C Lipo Pack w/XT-90. Turnigy batteries are known the world over for performance, reliability and price. It’s no surprise to us that Turnigy Lipoly packs are the ones to use for those in the know.

hobbyking.com

Ive had less exposure to lipo options than ebikes i was surprised to find 10s even existed as glances in that direction in the past had revealed chargers with the capacity to handle upto 7s packs. so i looked up 10s chargers and fell over backwards.. currently i use a handful of 1s packs only..

I was wondering the best config for batteries in series was thanks for answering that in advance while ive browsed hobbyking a few times with interest ive never committed to a purchase.. yet..

 

[saneagle]

Ive had less exposure to lipo options than ebikes i was surprised to find 10s even existed as glances in that direction in the past had revealed chargers with the capacity to handle upto 7s packs. so i looked up 10s chargers and fell over backwards.. currently i use a handful of 1s packs only..

I was wondering the best config for batteries in series was thanks for answering that in advance while ive browsed hobbyking a few times with interest ive never committed to a purchase.. yet..

You have more choice with lipos. You can have 10S (2 x 5S), 11S (5S+6S) or 12s (2x6S). Most 36v controllers can handle 12S, and you get 20% more speed and torque with 12S.

 

[thelarkbox]

You have more choice with lipos. You can have 10S (2 x 5S), 11S (5S+6S) or 12s (2x6S). Most 36v controllers can handle 12S, and you get 20% more speed and torque with 12S.

Think i want to read up on lipos more now,, as i think its not the mah printed on the label thats important but the mah available between 4.2v and 3.2v charge states of the battery. but with the less dense packs cost is more attractive and a smart charger will always be useful.

 

[saneagle]

Think i want to read up on lipos more now,, as i think its not the mah printed on the label thats important but the mah available between 4.2v and 3.2v charge states of the battery. but with the less dense packs cost is more attractive and a smart charger will always be useful.

On an ebike, they do around the capacity written on them. I used to use them a lot and always used a wattmeter to show voltage and how much I'd used.

 

[thelarkbox]

On an ebike, they do around the capacity written on them. I used to use them a lot and always used a wattmeter to show voltage and how much I'd used.

SO? 'typing aloud' If I know my max travel time is 10 minutes and i assume 500w constant draw during a journey,

So my controller is delivering close to if not its max current @ 15a? requiering 15ah to run for 60 mins and 6/15 = 0.4 ah to run for 10 minutes

So 400mah batteries are required to keep me running for 10 minutes, add 20%. -make that 25% 500mah. and double it to be safe 1ah batteries perhaps? 2 x 6cell 1ah 1000mah batteries required.

Now could £50 balanced charger charge a 6s 1ah battery in a timely manner (circa 1 hour) as charging 2x nightly needs NOT to be a chore and something that needs to be done at 2 am or similarly silly.

if so we might have a plan unless above is totally wrong?? (reason i typed it)

next time the actual max journey duration and calculate accordingly, 15mins 1.5ah batteries etc..

 

[thelarkbox]

Google is great looks like a 6a balanced charger can be found at a reasonable price, amazon link
So i have reviews to scan and sub par clones to weed out

 

[StuartsProjects]

NO I do not feel lucky at all when it comes to batteries, Not at all.

Then consider carefully if you want to use a battery on an eBike that has no BMS or safety cutouts .........

And take great care charging the Hobby RC type Lithium Polymer batteries, I came very close to being blinded (or worse!) when a humble 3S 1800mAhr one exploded in a fireball whilst being charged.

 

[Nealh]

3.2v with lipo use is too low for bike use, one should be looking at a very min of 3.6v or 3.5v for lvc on lipo with bikes. Once below 3.6v the voltage collapses or falls off the cliff very quickly and tbh there is little point in trying to grab all the mah out of the pack.
The chemistry stresses far easier then lion and the odd cell will swell if not up to it and will become the weak link in the pack.

They may be ok as a twin pack set up for short jourenys but the pfaff with multiple packs isn't worth it as you spend too much time connecting/disconnecting and trying to monitor each pack, a few of us have been there with multiple packs and tbh a single lion /BMS pack/battery makes life so much easier.

 

[saneagle]

SO? 'typing aloud' If I know my max travel time is 10 minutes and i assume 500w constant draw during a journey,

So my controller is delivering close to if not its max current @ 15a? requiering 15ah to run for 60 mins and 6/15 = 0.4 ah to run for 10 minutes

So 400mah batteries are required to keep me running for 10 minutes, add 20%. -make that 25% 500mah. and double it to be safe 1ah batteries perhaps? 2 x 6cell 1ah 1000mah batteries required.

Now could £50 balanced charger charge a 6s 1ah battery in a timely manner (circa 1 hour) as charging 2x nightly needs NOT to be a chore and something that needs to be done at 2 am or similarly silly.

if so we might have a plan unless above is totally wrong?? (reason i typed it)

next time the actual max journey duration and calculate accordingly, 15mins 1.5ah batteries etc..

Something wrong with your calculations. 500w for 10 minutes is 500 x 1/6 Wh = 83Wh. At 10S, that's about 2.3Ah. at 12S, it's 1.9Ah.

The recommended charge rate for lipos is max 1C, so for a 2.5ah 10s pack, that would be 2.5 amps or 92w

This dual channel charger costs £80 and it's supposed to charge each channel at over 100w, but I've always found them to be optimistic, so say 50w each or 100w overall, that'll do your 83Wh in just under an hour.

https://www.amazon.co.uk/dp/B0B5RGTYJZ/ref=sspa_dk_detail_1?psc=1&pd_rd_i=B0B5RGTYJZ&pd_rd_w=x5SKM&content-id=amzn1.sym.84ea1bf1-65a8-4363-b8f5-f0df58cbb686&pf_rd_p=84ea1bf1-65a8-4363-b8f5-f0df58cbb686&pf_rd_r=XJ1T8TSKM2PWRGDF5RNA&pd_rd_wg=yfQ6Z&pd_rd_r=e3d0d731-039e-45bc-aa13-f575aad42773&s=electronics&sp_csd=d2lkZ2V0TmFtZT1zcF9kZXRhaWw

Charging lipos as work is a bit dodgy unless you have a safe space to do it.

 

[thelarkbox]

Something wrong with your calculations. 500w for 10 minutes is 500 x 1/6 Wh = 83Wh. At 10S, that's about 2.3Ah. at 12S, it's 1.9Ah.

Thanks for putting it so kindly, Probably best if i stick to professionally built for purpose batteries for now perhaps..