Scary battery purchase time

r.brown.bayliss

r.brown.bayliss

Member
Hi, It is time for me to buy some batteries, and dropping a ton of money on Ali Express makes me nervous.

I am in New Zealand so have limited options.

One site I have looked at is https://hakadibattery.com/

Does anyone have any experience with them or maybe some alternative stores to recommend?
 
I'm in NZ too. Bought two sets of batteries off AliExpress. They took about twice as long as when buying other stuff but arrived in good condition nevertheless.
 
cool, got a link to the store? I am planning to go with LTO batteries and have seen reviews calling small den a scam store, but they seem to be the most pushed on aliexpress
 
They arrived. A few glitches, tracking numbers and company names changed, but they arrived.

The Alibaba store I purchased from. Help full staff, responsive to queries. I would use them again.
Cindy Li, email beyond@imr-power.com
imr.en.alibaba.com

Company Overview - Shenzhen Imr Technology Co., Ltd.

Shenzhen Imr Technology Co., Ltd. Products:Battery/Lifepo4 Battery/Battery Pack/Portable Energy Storage, E-Bike
imr.en.alibaba.com imr.en.alibaba.com


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Those should be very potent. My LTO cells are only 18 amp hr and have no issues putting out 678 amps running the sledgehammer. How many did you buy, and what motor/ESC/compressor will you be using?
 
AlexLTDLX said:
Those should be very potent. My LTO cells are only 18 amp hr and have no issues putting out 678 amps running the sledgehammer. How many did you buy, and what motor/ESC/compressor will you be using?
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I ended up with 48 of them, going 16s3p so 36 to 38 volts, with the speedmaster P2, and I have 2 of the ezrun 70125s and a max4 esc for each. The motors are a 540kv so maybe 20k rpm from them and something like 1:2 gearing to increase the impeller speed on the P2 to 35k+

I want to use it on a track, time attack style, so I will need 3 to 5 minutes of boost to get a couple of good laps in from a typical 10 to 15 minute session on track.

Back in the design and saving cash mode now, having just burned all the leaves off my money tree to get that lot 🤣
 
Oh I bet those cells weren't cheap. I've been looking at those motors as well; tbh the higher kv of the Castle motors is what keep me using them. Why only 36-38 volts? I think you'll find you'll need about 20s packs to run them at full power (voltage sag and all). Of course, this is uncharted territory and I don't think you'd do any damage running them at a lower voltage. It might work out. Either way, I think you'll have plenty amp hour capacity to do what you want to do, esp. if you bring in boost proportional to throttle/load.
 
Lower voltage because I was thinking about heat build-up with the motors, plus 1:2 ratio is easy maths to do.

I have 2 of these from Aliexpress for each motor, 30mm wide, 70mm ID, which I need to source some heat transfer goop to 'glue' them on with. Yes, I will be controlling the speed relative to car gear and throttle. I don't want to be breaking traction every corner, well, sometimes I do but not always 😆

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I initially did a water jacket/pump cooling type setup. I found that the air movement of the car was more than enough to keep the motor cool. As long as you have some degree of airflow, you'll probably be ok. I do want to put a bunch of these in the back of an SUV or truck, in which case cooling might be necessary.
 
I am moving at the speed of a geriatric snail. I finally got around to testing the resistance of my LTO batteries. Mostly came in at 0.35 or there abouts milliohms on the yr1035+ test device. Google tells me that is good so I hope google is right. Ol' Google has been getting pretty unreliable as it settles into old age :LOL:

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I'm sure that'll be fine. Those readings are done at a particular frequency and the results can vary at different frequencies. It's very similar to how a capacitor ESR meter works. The LTO cells provide tons of power.
 
3p x30ah x 20c = 1800amps !!! that will make an impressive pack! They look well balanced but if you want peace of mind, you can get a JK BMS balancer connected to your CC/CV charger. No need for high output, +/-1amp balancing and just not use it to control the load. (only charger and balancing.)
 
AlexLTDLX said:
Why only 36-38 volts? I think you'll find you'll need about 20s packs to run them at full power (voltage sag and all). Of course, this is uncharted territory and I don't think you'd do any damage running them at a lower voltage.
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I'm curious to know if we can overvolt large ESC like the Max4? Specs seem to say 6-12s lipo (4.2vx12 = 50.4v) 17s LTO would remain in the range but 20S LTO would be fully charged at 58v (20s x 2.9v) Is the spec more a suggestion to extend lifespan , or it would beep an error code and won't work if voltage exceed +/-50.4v ?
 
I wouldn't overvolt them. I don't know what the limiting factor internally is. I do know some are less than generous with their capacitor voltage ratings (but I'm not saying that's the case here). Keep in mind you'll have voltage sag with any pack under heavy load; also pay attention to the shape of a particular battery type's discharge curve. Usually, going from 100% to 90% results in a much greater voltage drop (and therefore performance drop) than say from 70% to 60%. Also the batteries tend to live longer only being charged to 70 or 80 percent.
 
Jeff23spl said:
I'm curious to know if we can overvolt large ESC like the Max4? Specs seem to say 6-12s lipo (4.2vx12 = 50.4v) 17s LTO would remain in the range but 20S LTO would be fully charged at 58v (20s x 2.9v) Is the spec more a suggestion to extend lifespan , or it would beep an error code and won't work if voltage exceed +/-50.4v ?
Click to expand...
I'm using my max4 at 54.5V and it still works fine - for the last 6 months or so anyway. Any higher and the my charger trips out the ESC regularly and you can tell it doesn't like it as the audible 'ready' tones sound wonky. Using a 21S battery which means each cell is at 2.6V which is perfect for my particular LTOs due to the discharge rates and longevity as Alex mentioned above. Once the eSC has been at 300ish amps for a couple of seconds the voltage is down below 50V anyway so i don't think the higher voltage is a problem for the (12s) motor either.
 
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