What Is Causing This Voltage Drop?

[PCeBiker]

It does seem strange that the battery in use doesn't show this sudden drop.

It may not be sudden?
Both your batteries may be losing some charge with every bump over the course of 2 hours.


IIRC, you've got a Watt hour meter on your e-bike.
Are you getting the full Watt hours that the batteries are rated for?

 

[6zfshdb]

It may not be sudden?
Both your batteries may be losing some charge with every bump over the course of 2 hours.


IIRC, you've got a Watt hour meter on your e-bike.
Are you getting the full Watt hours that the batteries are rated for?

I haven't tested the unused battery yet to see if the drop is sudden but the one in use discharges at a normal rate. I can ride 10 - 12 miles before it drops from 58.8 to 54.6. Under similar riding conditions, the watt hour rate matches my other batteries.

 

[PCeBiker]

I haven't tested the unused battery yet to see if the drop is sudden but the one in use discharges at a normal rate. I can ride 10 - 12 miles before it drops from 58.8 to 54.6. Under similar riding conditions, the watt hour rate matches my other batteries.

If you do have a flakey cell group that is losing its charge, then the BMS should shut down the second battery before you get a chance to use it.

It's strange how your batteries drain to exactly 54.6 volts.
That's exactly the voltage of a single cell group.

Perhaps you don't have a short but an open (bad connection) on one of the cell groups instead?
You've got 14 cell groups in series and removing a cell group should drop the output to zero, but maybe the BMS is compensating somehow?

Under similar riding conditions, the watt hour rate matches my other batteries.

Your DP9 batteries are about 15% bigger, so you should get about 15% further than your other batteries before your voltage drops to 54.6 volts.


I'm just speculating of course, but I think you've got two faulty batteries.
That voltage had to go somewhere and it probably stayed inside the battery. Either slowly shorting out making heat, or disconnecting and not being used.

I'm curious to hear what Grin has to say.

 

[PCeBiker]

Did you get your batteries figured out?

What was the problem?

 

[Gionnirocket]

Yes!
Inquiring minds want to know. . .

 

[6zfshdb]

It turns out, both batteries were out of balance. I usually charge with a Grin Satiator with it set to cut off at 58.8V. Occasionally, one string in each battery would never reach full charge and the voltage would quickly drop under load.

I discovered if I use another charger with a timer and leave it connected for 15 or 20 minutes after the battery reaches 58.8V, the problem goes away. I'm sure the Satiator has a way to deal with balancing. I'll have to study the manual when I get a chance.

 

[PCeBiker]

,.. I'll have to study the manual when I get a chance.

That's one of the reasons I didn't install my Watt Meter.
I didn't want to have to study the manual.

How's my item?
I dunno?

It looks good in the box.

 

[Gionnirocket]

It turns out, both batteries were out of balance. I usually charge with a Grin Satiator with it set to cut off at 58.8V. Occasionally, one string in each battery would never reach full charge and the voltage would quickly drop under load.

I discovered if I use another charger with a timer and leave it connected for 15 or 20 minutes after the battery reaches 58.8V, the problem goes away. I'm sure the Satiator has a way to deal with balancing. I'll have to study the manual when I get a chance.

I'd think it's one string reaching full charge slightly ahead of the others and the voltage difference is divided amongst the remaining 12.
Otherwise that would be one big imballance and probably show other signs of weakness.
But how does that explain only occurring on a ride?
Anywho.. glad I passed on the Satiator

 

[Slaphappygamer]

Just be thankful that you can write reviews. I’m unable to write reviews. My account has been blacklisted. I’ve contacted Amazon many times over the last decade and I get nowhere. I have no idea why I’m on the wrong list. I usually don’t even write reviews, but I feel bad when a seller asks me to write a review and Amazon won’t let me. People tell me I should care less, but that’s really hard for me.

 

[PCeBiker]

I don't write reviews.
That's almost as much work as studying a manual.

 

[PedalUma]

write reviews

I once wrote a bad yet honest review of a battery years ago. The seller then contacted me and said they would pay me to up the stars or even delete it. So, I cut pasted & posted that in the review. Reviews are garbage if they are corrupt.

 

[PCeBiker]

I don't write reviews.
That's almost as much work as studying a manual.

I did study the manual for my KT-LCD8H display though.

I spent many hours reading through the manual.
I don't have it memorized but I can find the information that I want easily now.

I had to spend two weeks learning to read Chinesium first.




I must have read this a hundred times,..

When C4 = 4 is confirmed, the "percentage value of the first gear speed accounts for its full speed" of the power assist gear flashes, press (UP) button or (DOWN) button for short to make selection, and the default value is 50%. The percentage values of other gears divide automatically in equal.



I opened a new savings account yesterday.
They just sent me an email asking how my Advice Center experience was.

I deleted the email.

 

[Gionnirocket]

It turns out, both batteries were out of balance. I usually charge with a Grin Satiator with it set to cut off at 58.8V. Occasionally, one string in each battery would never reach full charge and the voltage would quickly drop under load.

I discovered if I use another charger with a timer and leave it connected for 15 or 20 minutes after the battery reaches 58.8V, the problem goes away. I'm sure the Satiator has a way to deal with balancing. I'll have to study the manual when I get a chance.

Thinking... at what rate does the Satiator charge? Is it adjustable?
Could be a heat issue if the Satiator is charging at a higher current than your other charger

 

[Gionnirocket]

Just be thankful that you can write reviews. I’m unable to write reviews. My account has been blacklisted. I’ve contacted Amazon many times over the last decade and I get nowhere. I have no idea why I’m on the wrong list. I usually don’t even write reviews, but I feel bad when a seller asks me to write a review and Amazon won’t let me. People tell me I should care less, but that’s really hard for me.

Happens to me often... and I well know why
I'm just off a double secret probation block on this site!! @Angela M. !!!

 

[PCeBiker]

Thinking... at what rate does the Satiator charge? Is it adjustable?

I don't think it's the rate (CC mode).
I think it's the voltage (CV mode)

It sounds like it shuts off as soon as CV is met.

I set my power supply to 50.00 volts (for my 48 volt battery) and set CV at 2 amps.

I let it charge until the current and Watts drop to zero.

My battery should be balanced at 3.85 volts per cell group.

 

[PedalUma]

I deleted the email

I am now getting an email every day to click to digitally sign for and to collect $43,000. Yah, Right.

 

[Gionnirocket]

I don't think it's the rate (CC mode).
I think it's the voltage (CV mode)

It sounds like it shuts off as soon as CV is met.

I set my power supply to 50.00 volts (for my 48 volt battery) and set CV at 2 amps.

I let it charge until the current and Watts drop to zero.

My battery should be balanced at 3.85 volts per cell group.

View attachment 170690View attachment 170691View attachment 170692View attachment 170693

Yes but if the current ramp down to CV isn't early enough the battery can still be warm from the CC stage.. especially if charging at a higher current. Problem with an early current ramp down is it can take a long time to reach absolute full charge.

You should never have CV set above 54.6v as that's your second safety backup to the BMS. If anything give it brief rest and then top off.
50v is not considered a full charge but it's a very safe charge

 

[PCeBiker]

Yes but if the current ramp down to CV isn't early enough the battery can still be warm from the CC stage.. especially if charging at a higher current.

I ramp everything down at 50 volts then just let it sit for up to 8 hours.
I don't shut it off until the current finally drops to zero, by then the temperatures and voltages have all stabilized.

My power supply is underneath my TV so I can see it all the time.
It's sometimes more interesting to watch than what's on TV.

It's exciting to see it switch from CC to CV.
First you watch the voltage count up to your selected voltage, then you watch the current count down to nuthin.
It's fun.

You should never have CV set above 54.6v as that's your second safety backup to the BMS. If anything give it brief rest and then top off.
50v is not considered a full charge but it's a very safe charge

I charge to 50 volts after my ride then top it up to ~53.5–54.5 volts before my next ride.
I charge faster then, at 3 amps but I don't like going past 50% power with my power supply. I'm trying to get it to last longer.
I listen for the fan as it's charging. I turn it down if the fan runs constant.

I can also charge at 4 amps with my supplied battery charger if I don't want to wait as long to go riding.

 

[Gionnirocket]

I ramp everything down at 50 volts then just let it sit for up to 8 hours.
I don't shut it off until the current finally drops to zero, by then the temperatures and voltages have all stabilized.

My power supply is underneath my TV so I can see it all the time.
It's sometimes more interesting to watch than what's on TV.

It's exciting to see it switch from CC to CV.
First you watch the voltage count up to your selected voltage, then you watch the current count down to nuthin.
It's fun.




I charge to 50 volts after my ride then top it up to ~53.5–54.5 volts before my next ride.
I charge faster then, at 3 amps but I don't like going past 50% power with my power supply. I'm trying to get it to last longer.
I listen for the fan as it's charging. I turn it down if the fan runs constant.


View attachment 170694


I can also charge at 4 amps with my supplied battery charger if I don't want to wait as long to go riding.

I understand what you are doing... But I'm speaking about the OP and charging with the Grin Satiator.
I've charged with my power supply but rarely.. Usually to verify it can indeed take a full charge. Most chargers shut down a few tenths short.
Using my DIY Smart Charge Controller (poor man's Satiator) I can see the rate and ramp down with any charger.
My original battery when doing a full charge would start ramping down at 54.3v.

 

[Mily]

Usually a lower charge will cause a voltage drop, you can try a full charge and test again.