Sudden drop from half charge to zero

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azvectrix
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Sudden drop from half charge to zero

I seem to recall reading that at least one other person has had the following problem: Toward the end of my usual 20-mile one-way commute, with about half a charge showing, I started to lose power, and eventually got the "batsult" message. After a recharge at work, the same thing happened toward the end of my ride home. I put another mile or so on to see what would happen, and it eventually dropped to no charge showing, and zero estimate miles left.

This has happened a second time now, with several uneventful commutes between incidents. I have to say my confidence is a bit shaken. Has this happened to others? Does anyone have any theories as to what the problem could be?

Thanks,
Ron

nasukaren
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Re: Sudden drop from half charge to zero

Maybe a bad cell in one of your packs? It might be charging up ok, but depleting faster than the rest of the pack, then when it goes empty, its internal resistance would go up and your entire pack would seem to die....

Do you have SLAs or NiMHs?

Karen

Working on a Piaggio Boxer (mo-ped) EV conversion: http://gpsy.com/ev

Mik
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Re: Sudden drop from half charge to zero

Sounds as if somehow it had not charged properly, but decided to "declare" the battery full anyway.
I have not had this problem yet.

It might help to note the battery voltage before you unplug (unless a timer has done that for you); this might give you an indication if the battery is actually charged, but it gets harder to interpret the longer ago the charge was finished.

The most reliable way is to use a "Killawatt" kind of meter which tells you how much energy was consumed during the charging process. If you find your scooter presumably full but very little kWh have gone in, then you could expect it to not go as far as usually.

I still take photos of the instruments just about each time I get on or off the Vectux, and also during charging.
Once something strange and unexpected happens I can check all the details and compare it to similar situations.

What does your Vectrix dealer say about the problem and how to prevent it?

Mr. Mik

This information may be used entirely at your own risk.

There is always a way if there is no other way!

Mik
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Re: Sudden drop from half charge to zero

Maybe a bad cell in one of your packs? It might be charging up ok, but depleting faster than the rest of the pack, then when it goes empty, its internal resistance would go up and your entire pack would seem to die....
Karen

I would expect this should happen every time if it was a bad cell, though.

Mr. Mik

This information may be used entirely at your own risk.

There is always a way if there is no other way!

azvectrix
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Re: Sudden drop from half charge to zero

Mik, the Kill A Watt is an excellent suggestion--I think I'll grab one on the way home tonight.

The dealer passed my first report along to Vectrix, who haven't offered any theories, but did say that they would do whatever is necessary to correct the problem. I just notified the dealer of the second incident, so I'll see what they have to say this time.

Thanks,
Ron

rooster
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Re: Sudden drop from half charge to zero

I think, bearing in mind my experience has been virtually identical to yours, my battery is LiFePO4, one or more of the cells just plain failed!
Even my charger would not start in the end, indicating a full charge, which was certainly not the case.
These Li-on batteries may be the next technology and I love the extra mileage, etc., but it´s a bummer when they fail!!

rooster

azvectrix
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Re: Sudden drop from half charge to zero

Karen, Rooster:

I guess some bad cells are a possibility, though I wouldn't expect the problem to be so intermittent if that were the case. The good news is that a guy from Vectrix has contacted me directly, so maybe he'll come up with something.

Thanks,
Ron

azvectrix
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Re: Sudden drop from half charge to zero

Here's the response I got from a fellow at Vectrix:

"This sounds like it is a heating issue. We’re still trying to work out every problem, big or small, and we appreciate your patience in the matter. We’ve seen this sort of thing happen before, and it commonly has to do with the ambient temperature during the charge. It mostly happens when the outside temperature is 85 degrees, or higher. One thing we recommend you try is after a ride in such weather, before plugging it in, let it sit for 5 or 10 minutes (preferably in the shade, but just sitting should be fine), the fans may stay on, but it helps cool the batteries down."

It sounds like he's recommending to not plug it in right away in hot conditions. I have noticed that if the temperature is high, but not too high, it'll start the charging cycle right away instead of doing cooling cycles, so presumably the batteries don't cool down anyway.

AndY1
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Re: Sudden drop from half charge to zero

I agree. The best temperature to charge NiMH batteries is 20'C.

DaveD
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Re: Sudden drop from half charge to zero

Indeed, there is another thread in this forum that has in it a discussion about battery chemistries, and how it's best to have the battery fairly cool before starting a charge. I have taken to putting my Vectrix on a timer that starts it charging many hours after I return home and plug it in. That's partly to shift the load to nighttime, but also to let the battery cool down.

Mr Mik has gone further, and rigged his vectrix to run the fans off of an auxiliary power source that's also on a timer. That cools the battery as much and as quickly as possible, before another timer later allows a charging cycle to begin.

On very hot days, I've observed that the fans will continue to run for a while after turning the key off, but the time isn't that long, and I'm sure that the thermal mass of the battery is large enough that it's not cooled off that much for the time the fans were left on. I've taken to keeping my Vectrix in the shade as much as possible on hotter days. Happily, the Seattle area where I live has few hot days, and many more days that are kind to batteries of all persuasions!

Morrison
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Re: Sudden drop from half charge to zero

I have taken to putting my Vectrix on a timer that starts it charging many hours after I return home and plug it in. That's partly to shift the load to nighttime, but also to let the battery cool down.

I am doing the same thing. I got the Programmable Timer and set the schedule for charging from 10 pm to 4 am. Then an additional 30 minutes from 7:30 amd to 8:00 am right before I leave in the morning.
http://www.smarthome.com/2046.html

I got the Smarthome.com Energy Monitor (EM 100) Thanks Dave !!!
http://www.smarthome.com/1139.html

Connected in this order:
Electricity outlet in garage --> Programmable Timer --> Energy Monitor --> Vectrix

Based on my typical schedule, the Vectrix will cool down for 3 or 4 hours and then start recharging at 10 pm.
A 6 hour block will typically get an empty battery to 100%.

Since I leave at 8 am most morning, the final 30 minutes of "timer on" guarantees me a full battery.

Something of this nature is a must for all electric vehicle owners.

Mik
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Re: Sudden drop from half charge to zero

Here's the response I got from a fellow at Vectrix:

"This sounds like it is a heating issue. We’re still trying to work out every problem, big or small, and we appreciate your patience in the matter. We’ve seen this sort of thing happen before, and it commonly has to do with the ambient temperature during the charge. It mostly happens when the outside temperature is 85 degrees, or higher. One thing we recommend you try is after a ride in such weather, before plugging it in, let it sit for 5 or 10 minutes (preferably in the shade, but just sitting should be fine), the fans may stay on, but it helps cool the batteries down."

It sounds like he's recommending to not plug it in right away in hot conditions. I have noticed that if the temperature is high, but not too high, it'll start the charging cycle right away instead of doing cooling cycles, so presumably the batteries don't cool down anyway.

A) You need to differentiate between the MC fan and the 2 battery fans.
The MC fan runs when the GO symbol is on and will often continue to run for a minute or two after riding, stepping down in about 7 or so clearly identifiable steps.
The battery fans run at only one speed if they are on. They are the ones running during charging.
When the battery fans are still running with the key turned off, then it makes sense to delay charging, but only until the fans stop.

B) Standing around does not cool your battery much. It will let heat spread through the battery from hotter to cooler cells, so the hottest of the 12 temp sensor readings will come down.

C) Charging does not heat your NiMH battery until the late stages of charging. Due to the fans running it cools the batteries under many circumstances, all depending on temperature gradients.

So, assuming we are talking about at least 30-40% empty battery (60-70%or less left in it), it will be better for battery longevity to partially charge as soon as the battery fans stop running. Or even better, get the fans to run without charging until the battery temperature is down to ambient temperature or 20°C, whichever is higher.

One exception to this general rule would be if you charged your battery fully, it is still hot, the air is hot, you go for a short hard ride and make the battery a bit hotter but only deplete it a little bit. Under these circumstances it would go straight into the part of charging that heats the battery further if you did plug in straight away.

Another advantage of early partial charging is that the bike is not standing around as a dead duck.

To verify this for yourself, just plug in when you would normally delay charging but leave the key in the ON position for a minute before that. The battery temperature will then be displayed immediately when you plug in, avoiding the 21°C usually being displayed first for a minute.
Then, turn the power off and check the battery temperature again after a few hours, like just before your timer would turn the charger on. This will show you that your battery has been standing around in a hot state without loosing significant heat!

Try the same with about a one-hours pre-charge, you'll get the idea when you see how much your battery has cooled due to this!

Mr. Mik

This information may be used entirely at your own risk.

There is always a way if there is no other way!

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