Budget Battery suggestions 72v?

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MxusMick   1 mW

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Budget Battery suggestions 72v?

Post by MxusMick » Jan 28 2020 5:33pm

Battery? for Mxus 1000w 48v/Greentime 2000w 18f 60a Controller (in USA). Greetings, I am looking for an affordable 72v battery setup to purchase in USA. Walmart scooter batteries 36v 4.4ah $37 ×2? Any Suggestions for my DIY?
Cheers, Mick

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Re: Budget Battery suggestions 72v?

Post by torker » Jan 28 2020 6:40pm

Don't go lead acid.
Em3ev is one of the better vendors here. Honest specs on their products.
Welcome to the ES forum. Is this your first bike? If so you will find the battery is the biggest expense.
Dave When I die I want to slide in sideways yelling WooHoo what a ride !

Giant Rincon w rear 9C 6*10 36 v x 20 amps
Specialized FSR Comp 9C 6*10 48v x 30 amps

MxusMick   1 mW

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Re: Budget Battery suggestions 72v?

Post by MxusMick » Jan 28 2020 9:56pm

I appreciate your input, yes first post and DIY, been reading forum heavily, my controller hasn't arrived yet from Aliexpress, and prefer to find a battery in US to purchase. I am unsure of what to avoid, (with my larger controller) but wish to overvolt 48v Mxus 1000w hub with 2 -36v packs for a 72v. Walmart sells 36v 4.4ah $37 and 36v 7.5ah $101. I would prefer more ah but on a budget to get rolling. Am I on the right track, 72v 4.4ah $80, or 72v 7.5ah $200?
Mahalo, Mick

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Re: Budget Battery suggestions 72v?

Post by torker » Jan 28 2020 10:12pm

You really don't want that lead acid. You actually only get half of the amps. 4.5 ah. would like 2 ah. Not enough to run a bike . You would barely get around the block.
I would save a little more and find some lithium.

Maybe you can get lucky and find someone on here that wants to upgrade and sell you something decent.
Dave When I die I want to slide in sideways yelling WooHoo what a ride !

Giant Rincon w rear 9C 6*10 36 v x 20 amps
Specialized FSR Comp 9C 6*10 48v x 30 amps

MxusMick   1 mW

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Re: Budget Battery suggestions 72v?

Post by MxusMick » Jan 28 2020 10:30pm

Thnx Torker, I am looking at lithium packs sold at Walmart for escooters, the 36v 7.5ah $101 ×2 possibly. $202 72v pack if it can be ran in series, but I don't want it to be a tease, will look into forums battery sales section, I probably need more ah but thought this maybe a good start. Here in Houston surprised not to find more affordable local options. I have an old 18" Cook Brothers Racing bike, blast from the past:)

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dogman dan   100 GW

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Re: Budget Battery suggestions 72v?

Post by dogman dan » Jan 29 2020 7:57am

Lead for a slow, 24 or 36v bike, intended for use for under 6 miles. Forget it for 72v.

The only thing affordable for 72v are lipos, which most get at hobby king. but they are known to be dangerous, and you have a lot to learn to use those safely.

72v speed on bikes is tricky, cheap bikes break down fast at 40 mph sustained speeds. 52v 14s would be a better choice for now, and still get you going a very respectable 30 mph.

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Re: Budget Battery suggestions 72v?

Post by torker » Jan 29 2020 10:03am

Dogman is right. I did not know those walmart batteries were lithium. But they are super small. You really need about 10 ah of lithium to run a 20 amp controller without taxing the battery.
Lipo is the cheapest option but dangerous. Not sure if you can get lifepo? any cheaper than good lithium. Dogman has run those.
Dave When I die I want to slide in sideways yelling WooHoo what a ride !

Giant Rincon w rear 9C 6*10 36 v x 20 amps
Specialized FSR Comp 9C 6*10 48v x 30 amps

MxusMick   1 mW

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Re: Budget Battery suggestions 72v?

Post by MxusMick » Jan 29 2020 11:19am

I appreciate your comments, I will keep shopping, also my ride is a full suspension Motobecane, I plan to trail ride mainly, up in CO, so there will be lots of hills. My Mxus 1000w hub was purchased used, I have no idea what wind it is, and the 2000w 60a controller is on order, so hoping to sort out the battery pitfalls now. I am 160lbs and the bike will hopefully weigh 50lbs or less complete. Excited to be on this journey, will be relieved to install it proper without blowing anything up!
Many thanks, Mick

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Re: Budget Battery suggestions 72v?

Post by MxusMick » Jan 29 2020 11:30am

Is there a minimum to be aware of with battery size when using 2000w 60a 48v-72vcontroller, as ah is concerned, I know it's low v cutoff is 40.5v, so I can't run less than 48v battery. Thanks for sharing your knowledge:)
Mick

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Re: Budget Battery suggestions 72v?

Post by torker » Jan 29 2020 11:38am

Em3ev. Has good info about their batteries. It will give you "honest" ratings for max current.

2000 watts is not too much. Most 10 ah batteries with good cells should handle it. It gets bad when you do run the battery at its limits for extended times.
Dave When I die I want to slide in sideways yelling WooHoo what a ride !

Giant Rincon w rear 9C 6*10 36 v x 20 amps
Specialized FSR Comp 9C 6*10 48v x 30 amps

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Re: Budget Battery suggestions 72v?

Post by amberwolf » Jan 29 2020 8:49pm

MxusMick wrote:
Jan 29 2020 11:30am
Is there a minimum to be aware of with battery size when using 2000w 60a 48v-72vcontroller, as ah is concerned, I know it's low v cutoff is 40.5v, so I can't run less than 48v battery.
60a controllers can often allow momentary bursts of much more at startup from a stop, and potentially 60a continuous.

so your battery must be able to handle at least 60a continuous if you have hills or will ride at speeds or with loads that cause that much current to be drawn.

cheap batteries are typically 2c max, at least if you want them to stay balanced and last a long time, so if you expect to run the system at 60a for any length of time, you'd want at least a 30ah battery. if you only plan to use the system at much less (or change it's settings to lower it's current limit), or you get a better quality battery that can handle higher currents for long periods, then you can get a smaller battery.



please note that if you use a battery that needs a higher lvc to protect it, you will want to change the controller's lvc setting to match the battery. meaning, if you have a 48v pack, 13s, the lvc it's already setup with will protect the cells at 3.1v or so, so they don't get run down so far the bms has to shutoff the pack to save them. but i fyou use a 72v pack, the controller lvc can't protect the pack, and if you don't manually watch the voltage to stop riding when the battery drops to around 62v or so, then the bms will have to do the protection of the pack, and that's harder on the cells cuz the bms lvc is usually setup for a last-ditch prevent-damage/fire kind of thing. if you can program the bms's lvc to be higher than that, then that works too.


also, you may find cheap batteries that give the option for wildly inappropriate bms sizes (like a 10ah pack that has a 100a bms, but only has cells that can really handle 10-20a without heating up), so beware of that. some cells can handle that, but the cheaper they are the less likely that is.

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Re: Budget Battery suggestions 72v?

Post by 999zip999 » Jan 29 2020 9:53pm

You can melt that thousand watt motor at 60 amps 30 amps is more like it for long life of the motor. I'm saying this as I know Colorado have some hills and even hogging down on the throttle and chugging up a mountain you're just making heat

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Re: Budget Battery suggestions 72v?

Post by MxusMick » Jan 29 2020 10:55pm

Thanks for the knowledge, I have no clue if the Greentime controller can be adjusted to limit amps, would a 30a fuse do the trick, since I have purchased the 2000w 60a controller already. 72v 30ah battery probably too pricey for now, will a smaller battery limit amp output to keep hub safe, or ruin battery pack with the large controller? Or did I get carried away buying too big of a controller? I don't want to ruin my stuff in a week, planning on riding in the fairly hard but safe range. I bet the answer is already here in forum, don't want to be a pain, simply have no $ to waste by frying anything.
I also underestimated battery cost, but have put in less than $300 for all components except battery, charger, voltmeter, so it seems like it's meant to happen eventually.
Happy Trails, Mick

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Re: Budget Battery suggestions 72v?

Post by amberwolf » Jan 30 2020 12:57am

some thoughts:

the battery is the core of the system; if ti can't output the power to run the system, then the system won't perform the way you want it to.

either it will sag in voltage a lot from too high a load for it, which means the power will drop a lot, and as the battery discharges closer to empty it may even shut off long before the battery should be empty, beause the bms sees the voltage drop below the lvc low voltage cutoff and is trying to protect the cells. the cells will also heat up more than they should, and age them faster.

or the bms will just shut off to protect against the overcurrent load, turning off all power to the bike when it happens.

if the overlaod is bad enogh and hte bms can't shut off to protect itself, and the bms fets aren't made to handle that much current, it could damage or destroy the fets, requiring the bms to be repaired or replaced to be able use the pack again.

depends on how the bms is designed. the cheaper the battery, the cheaper the bms design usually is, too.




you can fuse the system at about whatever the limit of the battery's capability is, but every time the controller tries to draw more for long enough it'll blow the fuse. that's gong to get annoying real quick if it happens a lot. ;)

fuses don't blow right at their current rating, either...their rating is generally the max they can sustain...it can take a lot more to overlaod them enough to blow.

they also need to be rated for the voltage they have to break, so if you have a 72v pack you need one that can handle the over-80v that will be fully charged. otherwise when the fuse tries to blow you may just get arcing inside the fuse instead of blowing the circuit, for as long as the current demand is high enough, and if it stays hot enough long enough the fuse or holder can burn or start a fire in stuff around it.

also, fuseholders for like the glass fuses and some of the blade fuses can be crappy. when they are, they don't hold the fuse very well, so there's a high resistance in the contacts, and they can get hot enough to melt the holder plastic, and eventually start arcing and even catch fire under some condtions...but usually the melting just causes problems with the system like intermittent cutouts, etc.

bolt-on fuses won't have that problem as long as you use hardware with locking nuts (nylock, etc).

if you can't adjust any of the controller settings, then if you really have to you can cut it's current limit down by disconnecting one or more of teh shunts in it, if it uses more than one. if it has four, taking one out cuts the limit by 25%. if it has two, then it's 50%, etc.



the controller is what limits current in the system. if ti's too big for the motor or battery, neither of those can do the limiting hte controller is meant to.

a smaller motor can take some mroe power than it is rated for, but how muhc depend son the situaiton and usage, as well as motor type and design. dd hubs ake more than geared, and usually for longer, before they have problems. hills and higher pseeds force the motor to draw more power, making it hotter, as do lots of stops and starts. if it's only short bursts of a few seconds at a time, with time to cool off afterward at a more normal power level, most motors can take more than twice their ratings, sometimes several times the rating.

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Re: Budget Battery suggestions 72v?

Post by MxusMick » Jan 30 2020 1:39am

Nice to hear, thank you! I am looking at vids of 60v or 80v tool batteries ran in parallel, there are factory reconditioned ones (Dewalt, Ego, Greenworks) for cheap online($50-100). People are opening them and connecting wires through to connect to controller without cutting tool butts to interface, it looks like a start. Maybe 2 in parallel with the Greentime 48-72v 1500-2000w 60a controller I have? Let the Good Times Roll! Mick

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Re: Budget Battery suggestions 72v?

Post by amberwolf » Jan 30 2020 2:04am

if you bypass the bms inside the packs (necessary for some toolpacks when not used with their tools) then there is no protection for the cells against overcurrent or overdischarge.

there are threads here on es about various toolpacks used on ebikes if you want to see what's already been done, and problems encountered.


remember you must get enough of them in parallel to supply both the current and the capacity you need. if the toolpack is designed for say, 5a output, then if you have a 60a controller you'd need 12 packs in parallel to run it without stressing or damaging the packs.

if they are made for 10a output, you'd need six of them.

if they have, say, 4ah of capacity, then if you want to have significant range, you'd likely need to parallel at least a few of them, dependign on exactly what your needs are. (range depends on speed, terrain, wind, weight, if riding is stop/start or continous, how hard you like to acclerate, how much pedalling you do, etc).

if the packs are 20ah then just one is probably enough for significant range, though you might still need multiples to get the amp rating the controller requires.

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Re: Budget Battery suggestions 72v?

Post by MxusMick » Jan 30 2020 12:08pm

Thanks Amberwolf for the excellent feedback, you rock!

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Re: Budget Battery suggestions 72v?

Post by problemaddict » Feb 09 2020 1:55am

Hi Mick,

I've used both 36v "hoverboard" packs and tool battery packs on my two ebikes. I can offer you some insight. These were my two first ebike projects and I think for beginners, these types of packs are a good way to get started, but maybe not the best way...

I got the hoverboard packs from batteryhookup.com a couple years ago. THey no longer have any stock. They have some off-brand cells in them, but they are supposedly capable of 20A per cell. I am running six 36v packs, two in series, and three in parallel for 72v 12aH total. They've been working great in series, with no failures for over a year. Mostly on my eMTB pulling 50A. But recently I put them on my eBMX bike with a controller pulling 80A:

Image

These packs have been holding up suprisingly well. I don't know if the Walmart packs will be as robust. The only complicated thing with these packs is balancing. While the packs have a BMS, they are only low-voltage and over-voltage protection BMSs. So they don't balance the cells. I balance them using cheapo "Battery Medic" balancers, but they are only good for 6s batteries. So i had to solder up a harness to use two 6s Battery Medics to balance the 10s hoverboard packs. I balance them after every 5th or 6th charge/discharge.

I think, for a beginner on a budget, tool packs might be the better option.
On the same eBMX bike as above, I started out using Echo Tool "58V" 4aH battery packs. They are actually 52v nominal, 14s2p packs. You can get them at Home Depot for $169 per pack, but I've been buying them on eBay for around $80/pack for "refurbished" packs.
I have bought seven packs and only had one pack that was not good. I alerted the seller that the pack wouldn't charge and received a full refund.
I use two in parallel with a home built harness. I charge and balance them w/ the factory Echo charger that you can find on eBay for about $35.
These packs are great! They have robust LG cells in them and are built for abuse. I've dropped them on a concrete floor a few times and they suffer no damage. With 2 packs in parallel, they take 50A draw with no issue.

Image

Harness:
Image

With either pack you go with, you will have to purchase some 8g wires, some XT90 connectors, and a good soldering iron to build the custom harnesses you will need. But you with the hoverboard packs, you will have a cheap, high voltage pack for experimenting; and with the tool packs you will have some robust batteries, at a decent price, but not the smallest or easiest to work with size/shape pack. These type of packs will get you started and have you riding quickly without having to worry about building your own battery or paying a big sum for an off-the-shelf battery.

if you are a tinkerer and experimenter and a cheapskate, then this is a good way to go. If experimenting worries you and you want something with a warranty, then definitely buy an EM3EV pack.

If you have any other questions about using these packs, lemme know!
You can read about my eBMX build here:
viewtopic.php?f=6&t=84157&p=1292495#p1292495
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Check out my YouTube Channel: Mike Tinkers and Builds Stuff

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Re: Budget Battery suggestions 72v?

Post by MxusMick » Feb 09 2020 5:28pm

Many blessings for the awsome info! I am definitely a tinkerer and scrounger, and really stoked on the reallife application of reused materials for ebikes, eskate, and offgrid solar. I also believe this is the future technology that will save humanity when SHTF, I am reading the forum regularly now and have a used 36v hoverboard battery and 2 used tool packs 18v & 20v to salvage. I haven't even used the internet before for social media, but feel a connection to you guys who give free good advice on this forum, thanks to all! I imagine y'all akin to that helicopter flying mad scientist in Road Warrior. I am learning alot and want to build my own packs eventually when I'm confident I won't blow anything up, and practice solder, also digging the Vruzend legos for ease of repair. Looking forward to getting the skills to build bikes for others, always love the fun shit! Worked at a Surfpark, a ski area, a juicebar, live the life you love and love the life you live! Many Mahalos to E.S. Contributors

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