Troubleshooting

General Discussion about electric bicycles.
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Sami fouad   1 mW

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My ebike goes off sometimes

Post by Sami fouad » Jan 28 2020 4:23am

:lowbatt:
Hello is there any one that had a problem with his ebike... The issue is that my ebike goes off sometimes when i use it... When i turned it on it shows all that power are full while i move on the power assist looks like goes down gradually as far as i pedal when i stop pedaling the power assist comes full again..thanks in advance

Sami fouad   1 mW

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Troubleshooting

Post by Sami fouad » Jan 28 2020 12:21pm

Hello is there any one that had a problem with his ebike... The issue is that my ebike goes off sometimes when i use it... When i turned it on it shows all that power are full while i move on the power assist looks like goes down gradually as far as i pedal when i stop pedaling the power assist comes full again..thanks in advance

docw009   100 kW

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Re: Troubleshooting

Post by docw009 » Jan 28 2020 2:41pm

Does the problem happen at full charge too?

Most smaller batteries at half charge will act like that. You ride and the battery display will drop fast when you start pedaling harder to climb a hill, or you have a throttle and use it. Then when you stop the harder usage, the battery display comes back. This means your battery is getting older, or if it is new, then it wasn't strong enough for your ebike. It could also need rebalancing.

Sami fouad   1 mW

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Re: Troubleshooting

Post by Sami fouad » Jan 28 2020 3:07pm

Yes the battery shows that's fully charged.. If i hold the bike up and turn the throttle nothing happensit works fine. The problem is while pedaling i can see that the power assistance is getting lower until it shut down.. And i have to turn tge key another so as ti to start again.. Sometimes by only moving the throttle it turns off while im riding.i don't know what's the problem

Sami fouad   1 mW

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Re: Troubleshooting

Post by Sami fouad » Jan 28 2020 3:11pm

Its a 250w motor brushless, battery 36v 10ah

docw009   100 kW

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Re: Troubleshooting

Post by docw009 » Jan 28 2020 9:22pm

How old is the battery? Is it a brand name ebike? How far did you ride on a full charge when it was new? How far do you go now?

Sami fouad   1 mW

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Re: Troubleshooting

Post by Sami fouad » Jan 29 2020 10:26am

Its 2 years old and half. I go with it like 2 kms and turns off

markz   100 GW

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Re: Troubleshooting

Post by markz » Jan 29 2020 9:33pm

Get yourself a digital multimeter and read the voltage of the battery when it cuts off.

Sami fouad   1 mW

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Re: Troubleshooting

Post by Sami fouad » Jan 30 2020 1:07pm

Hello its 39.5 v

docw009   100 kW

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Re: Troubleshooting

Post by docw009 » Feb 03 2020 10:38pm

I think your battery must be badly unbalanced. You have a few cells just barely above the minimum voltage, and the rest are almost at full voltage. When you try to charge it, the charger stops as soon as the high cells reach full voltage and the low cells can't get recharged. When you run the bike, after 2Km, the lowest cells are discharged, so the battery shuts off.

A new battery will get you going again.

You could try rebalancing the battery, but I think not that many batteries have balance circuits. .

Sami fouad   1 mW

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Re: Troubleshooting

Post by Sami fouad » Feb 04 2020 3:03am

How can i do the rebalancing?

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E-HP   100 kW

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Re: Troubleshooting

Post by E-HP » Feb 04 2020 11:30am

Sami fouad wrote:How can i do the rebalancing?
That’s a pretty generic question, so I’m assuming you didn’t attempt to use the search tool, as suggested in the FAQ sticky above?


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Sami fouad   1 mW

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Re: Troubleshooting

Post by Sami fouad » Feb 04 2020 11:33am

No i didn't. Sorry

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amberwolf   100 GW

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Re: Troubleshooting

Post by amberwolf » Feb 05 2020 1:44am

docw009 wrote:
Feb 03 2020 10:38pm
I think not that many batteries have balance circuits. .
huh? pretty much any (even generic) ebike battery will have a bms with balancing function in it.

unless it's a diy built specifically with no bms, it's almost certainly going to have a balancing bms in it.

whether that is any good at balancing the specific cells in a pack under a specific use case, may be another story.

docw009   100 kW

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Re: Troubleshooting

Post by docw009 » Feb 05 2020 2:24am

Karl Gesslein says "There are 2 kinds of BMS, ‘balancing’ (smart) BMS and ‘monitoring’ (stupid) BMS. "
https://electricbike-blog.com/2015/02/1 ... e-process/


Tom Jazewksi (he posts here sometimes) used to do some customer support for Unit Pack Power, and says a lot of their packs use the "stupid" BMS. I have a few batteries purchased over the years from UPP . I also have other packs with balance BMS inside, and they will draw 40 to 50 ma for a while after their chargers go green. My UPP packs don't do that,

In fact, I replaced the BMS in a UPP bottle battery this week. When I opened it up and found all the cells in perfect balance anyway, I almost buttoned it back up, Why break something that was working, but I purchased a balance BMS last summer and forced myself to do it.

Here's the battery. It's made with GA cells.
P1190185.jpg
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Tiny little BMS removed from the battery. There's no room for balance circuits on this thing. That's a Canadian nickel next to it. The dIameter of the BMS circuit board is about 1 3/8".
P1190186.jpg
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I rounded the corners off an Annpower BMS (with balance circuit) and shoehorned it in. I don't think it will run any better if the original pack was balanced after 2 years.
P1190181.jpg
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The install went without incident. I made one error and skipped a cell, but I double check each balance wire with a meter and caught the mistake immediately. Whew.

It also turns out the many of the BMS I see on ebay and aliexpress have no balance circuits.

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amberwolf   100 GW

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Re: Troubleshooting

Post by amberwolf » Feb 07 2020 10:51pm

that's interesting...and maybe that's the cause of a number of people's battery problems where they couldn't fix them leaving them on the charger.

i guess we should stop recommending that step, and go straight to pack disassembly and cell testing. :/

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