Battery power problems

Popebike

1 mW
Joined
Jan 29, 2019
Messages
14
Location
North jersey
Hi i am new to ebiking and new to this forum have been experimenting with converting my old bike to ebike with a Ebay kit trying to keep cost low . Every thing was working well but batteries now have problems
Please let me know any helpful suggestions thank you
I have two 48 Volt batteries with problems of power cutting off on load and one battery is not charging to full capacity
I have a 48 V 15 AH 13th series lithium ion battery made with Gabriel 18650 batteries made by a individual . My problem is that the battery power cuts off on a load , cuts off at about 45 volts. I know it is not a good quality battery but the problems I have is that I need to reset the power by unplugging the battery from the system and plug it back in to have power again and then it works again.
I also have a 48 vote 14 AH lithium ion 13 series battery home made with used 18650 laptop batteries and VRUZEND kit with the Vruzend BMS. This battery also cuts off on a load around 40 volts. This battery resets itself with out having to unplug the battery ,I do not need to unplug and replug,
Is the BMS on the batteries cutting the power off ? Why do i need to unplug one unit and the other resets by self ?
Could the power off problem be my controller (Controller came with the Ebike eBay kit no information available)?
The battery built with Gabriel 18650 no longer charges more than 52.2 volts use to charge to almost 54 volts why?
 
Hi Popebike! Welcome to ES.

Sounds to me like your batteries are not balanced. Have you been leaving them on the charger long enough to balance charge?

Also, you may be hitting your low voltage cutoff at 40v or so.

But first things first.

Are you batteries balanced at the end of the charge?

:D :bolt:
 
Cutting out at that voltage is normal. The batteries are essentially flat and when under load the voltage will sage further and be tripping the low voltage cut off in the controller or BMS.

The lower voltage when the charger reports charging finished is probably due to imbalance. The BMS is cutting power because one of the series groups has reached 4.2v but the final pack voltage is less than 54.6v because one or more of the other groups are not 4.2v.

Problem with cheap BMS is you can't easily see what is going on. You need to open the pack and put a multimeter across each group and record the voltage and see if one or more is lower than the others. Leave it on charge for a while and see if it improves at all. It can take many hours for a pack to balance.

Ideally you have a bluetooth BMS as these allow you to easily monitor the state of each group from a mobile app. They cost about 40USD I think.
 
Usually if the BMS trips on low voltage you'll need to unplug the load and reconnect it before it powers back up. If not, then it's generally the controller hitting it's LV cutoff, releasing the load at which time the voltage goes back up and it carries on.

If the BMS is tripping at a higher than expected pack voltage it's going to be reading low voltage on one cell group (as opposed to the entire pack).

If the charger is cutting off before full pack voltage is reached, it's because a cell group has reached full voltage before the rest of them. Leaving the charger connected should eventually allow the pack to balance itself, as the BMS will bleed off that high cell group and then recommence charging to let the rest of the cell groups charge up. It can be a slow process, depending how bad the imbalance is, and in the most extreme cases might not be possible.

If a pack is constantly going out of balance and you're not exceeding it's specifications in terms of amperage draw, that's an indicator of something wrong with it. Sometimes it's a bad cell in a group, sometimes it's the BMS malfunctioning and constantly bleeding down a cell group (because it's "stuck")
 
Thank you for the info
If the battery charger shows done with green light would leaving it connected continue to perform the balancing work on the cells??
 
some chargers continue low current flow after green led for balance function

easiest leave charger connected for several days

might be able to see voltage continue to climb probing charge input

only way to really know insert power meter
 
Yes, you may need to leave the battery charging overnight for it to be fully balanced, even if the green light is already on.

Sometimes the batteries will cut out under a high load. This is an indication that the controller is asking for more power than the battery pack can supply. This is caused be either the battery not being charged and balanced, or it could just be that the battery is undersized for your motor/controller. If the battery is undersized you just need to learn what level of load causes it to shut off and avoid that.

Warren
 
Thanks all, will try leave charger on for a few days and check voltage
The pack worked well when new and when this pack cuts out I have to disconnect the a wire to reset pack ,I have been told that it is the BMS that cuts out this way ,if controller cuts out it would reset on its own and that is what my home made battery with a BMS does at times on hard pull late in ride.
Have an other question my controller has a set of wires that are called (road legal switch wire) it is a 1000watt motor and when connected it supposed to limit it to a 750 watt motor . How does this work ? And does this reduce the amount of battery power used??? Is there a problem using this switch wire?? It does limit speed I noticed
I have no idea what controler I have ,it came with the complete 1000 watt front motor kit from EBay any I idea what the specs are ?? It has worked very well since last spring when batteries are good.
Has any one have any comments about the Vruzend battery kits I use one with old laptop batteries works ok but not quality batties, thinking of doing again but purchasing new 18650 quality batteries ,what do you all think
Buy battery made or make with good cells
Has been fun riding it looking to spring
 
Popebike said:
Have an other question my controller has a set of wires that are called (road legal switch wire) it is a 1000watt motor and when connected it supposed to limit it to a 750 watt motor . How does this work ? And does this reduce the amount of battery power used??? Is there a problem using this switch wire?? It does limit speed I noticed

The wire changes the current limit in the controller and possibly limits the maximum speed. In you situation, I would try using it in the low speed mode and see how much further you get. Running at lower power will reduce the load on the batteries and they won't trip so early. But it's not as much fun...

Long term, you need a bigger battery or one with stronger cells so you can run at full power.

A good test (but difficult in practice) is to measure the pack voltage while using full power. Compare this to the resting voltage. This will tell you how much the pack is sagging under load.
 
[
I do have a voltmeter connected and there is a lot of voltage drop I agree my batteries are not good
Need fix or invest in new battery
Just so expensive
eBay V Power battery????????
 
Ebikes.ca
em3ev.com/
pingbattery.com/
lunacycle.com/

Look around on ES as other posters might have more names for you.

Yes expensive, but worth the money in dependability. And they won't catch on fire and burn your house down.

Otherwise, you pay your money and take your chances.

:D :bolt:
 
Looking to build my own battery and would like everyone opinion on a few things
I am going to use the Vruzend 18650 cap kit again but with new cells not recycled any comments on the Vruzend Kit?
Al most Decided on the cell to use Samsung INR18650 30Q 3000MAH 15AMP or the more expensive LG MJ1 3500MAH 10AMP about about $130 more for 4 moreAH . Any comments and opinions on these cells??
Found a Company that sells lithium battery has any one heard of them and what do you think
Lion Whole Sale in Phoenixville ,PA
Lion wholesale.com

Will be doing a 13S 8P battery = 104 cell at max 24AH with Samsung 30Q or 28AH with LG MJ1

Any comments or opinions would be greatly accepted thanks POPebike
 
Good Question. I have been looking at these same two batteries for my first E-bike build 500 Watt 36 volt rear hub motor. Flat roads, no hills. 10S-6P to start with. Will have to see if that will handle the distance, 20 - 30 miles RT with PAS.

Popebike, did you make a decision?

Regards
Steve
 
Weak cells in at least one cell group is why your battery cuts off under load so soon. ( the one at 45v)

It should cut off more like 42v. Its going early because of at least one cell group is too weak. in the first case, your bms needs resetting. That is definitely one string of cells dropping to the point the bms cuts it off. So if only one parallel group is low enough, will trip the bms. Again, this is normal, and the voltage you are seeing it at is pretty normal. It can be possible to keep riding after you reset the bms, but only at lower load. You seem to have a problem with both batteries being a bit weak for your bike.

The other battery has a bms? if so its cutting out lower than the other. But its not the bms tripping in this case. Its the controllers low voltage cut off. That is also typically around 42v for 48v controllers, but clearly yours is set to 40v. So as you get farther into the discharge, your voltage sag is enough to cause your controller to shut down, but then once shut down, the voltage recovers with no load and the controller starts up. And then shuts down again when you apply a load.


Balancing the battery better can depend on the bms. Some will shut down the charge, but then start it up again once the bms has discharged the highest cell group some. Many, or even most, just shut down and then discharge the high voltate group. This group that charged fastest, is your weakest group. So the good parts of your battery just got undercharged.


The trick to get fully charged and balanced, is to wait a half hour, then unplug and replug the battery to the charger. If it does not start back up, go ride around the block, like a quarter mile ride. You may have to repeat this process a few times to get the battery to charge full, and hold its charge. Old or damaged cells will never quite hold the full 4.2v. But a decent cell will still hold 4.15 or so, once it gets an opportunity to get full. Even after this process though, that cell group that charges too fast will always have less capacity than the others, and limit your range.
 
20 30 miles rt requires large battery

500wh unlikely to manage even pas

hard for new folks to grasp practical range sizing

to avoid stranded or worse take small steps

learning about battery unlocks reliable use/application
 
So what battery config would you recommend for a 500watt motor and why? Help me understand.

Thank you
 
stevecahill said:
So what battery config would you recommend for a 500watt motor and why? Help me understand.

Thank you

the biggest one you can afford and fit is the short answer.

longer answer: a bigger battery has less difficulty delivering the power you want/need. the less stressed a battery is the longer it lives. imagine trying to start a truck with a motorbike battery. it probably can do it but only a few times before it fails.
 
So a 10s 6P is too small? How about a 10S 10P? I do not need speed, or a 2000 watt motor.
 
stop thinking a battery can be too large, that is not possible, a battery can only be too small. cutting the load by using more cells in P gives you more lifespan and less sag. it does not give you more speed, just more stable power delivery and possibly more acceleration if you choose. volts give you speed, amps give you acceleration.
and yes, 6P is too small if you want you battery to last. 10P lowers the load on the cells by 45%. that is a HUGE jump in lifespan and actual usable capacity.
imagine what would be better: using a moped battery to start a truck or a truck battery to start a moped? what battery lasts the longest?
 
stevecahill said:
I have been looking at these same two batteries for my first E-bike build 500 Watt 36 volt rear hub motor. Flat roads, no hills. 10S-6P to start with. Will have to see if that will handle the distance, 20 - 30 miles RT with PAS.
How much battery you need depends on speed, wind/weather conditions, terrain, total weight (bike/rider/etc) acceleration time desired, how much pedalling you're doing, etc etc.

An example: If you do no pedaling and want 20mph on average terrain and weather, you could use up to around 1/2Ah to 1Ah per mile on 36v. Something like 15-20Wh/mile. So for 30 miles of range, up to 600Wh required. Wh is average volts * Ah, so for 36v that would be around 17Ah.

More hills, more wind, more weight, more Wh needed.

The slower you go, and the more you pedal, the less Wh needed.
 
One reason for bigger battery packs than you actually need is because they will always wear down, and get less and less range over time. You always want more than you actualy need, by the percentage of how fast the pack will wear down, so you don't start running out before you're done riding.

Related to that is how hard the pack is used--how high the "c-rate" demand that is placed upon it. If it's a 15Ah pack and the controller pulls 30A, that's a 2C demand. Cheap packs don't always sustain this kind of demand well, even though it is relatively very low. Similarly, faster charging is harder on packs.

If you live in an area where there can be detours for whatever reason, you may want to add that distance to your required range, so you never run out even if you have to take detours.

Similarly, if you have headwinds or crosswinds, they change the power requirements to those needed for the windspeed plus the actual speed. Up to around 15-20MPH total windspeed, the power increase is not that much. Beyond that (say, 10MPH wind and 20MPH speed) it goes up very quickly. This increases stress on the battery if it is too small, as well as on the controller and motor (assuming they are sized to be capable of overcoming such winds and still maintaining road speed).
 
Good advice, thank you.
The original question we had was, should we purchase the Samsung INR18650 30Q 3000MAH 15AMP batteries or the LG MJ1 3500MAH 10AMP ?
 
the 30Q are NOT 15A rated. at least not if you pack a bunch together and dont want to end up burning your pack up.

if you want reliabliity get the 29E, way cheaper and basically indisctructable by comparison to the large capacity cells. that way you can use the money to buy more cells so the battery gets bigger and more robust.
 
Samsung 29E 18650 2850mAh 2.75A Battery, https://www.imrbatteries.com/samsung-29e-18650-2850mah-2-75a-flat-top-battery/
Do you use this battery yourself? I thought I would be better off with a higher capacity cells. The pack will be a 10S 10P in size, for 36VOLT 500 WATT motor with a 20 amp controller.
 
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