Quantum Blast 850 modification & rebuild

[Burgerman]

It can discharge at UP TO a max of 100 watts (volts x amps) using its internal discharge resistors and fans.
It can discharge at up to 40A and 1344 watts into a battery system.

If you set it above 100 watts it may give an error as it stabilises the discharge current.

It should regulate it so that it just reduces current accordingly.

[hotwheels_75]

That’s the problem though, I don’t think I set it above 100watts? Is it pack volts x Amp level chosen in the software? Or PSU Voltage x Amps? Either way, unless I’ve missed something I should have been below the 100 watts.

My pack started around 28.8V and even selecting 3A as a discharge rate, I got the error code. It worked once for several hours. I stopped and restarted with the same settings and it errored.

Could it be related to my PSU?

Further testing with regeneration discharge it was working pretty well.

[Burgerman]

Possibly. But I never saw an error on any discharge in hundreds of tests with chairs or hobby lipos etc.

[hotwheels_75]

Sooo long absence, haven’t been feeling well or using my modified chair. It was out on our closed in deck. Temperatures have been freezing. Finally got to bringing the chair in to test batteries.... and store them inside. Whoever parked my chair a couple months ago never disconnected the pack. It’s now beyond dead 6v total from a 96ah 24v 8s lithium pack

I suspect it’s toast. Is there anything I can do to try and save it. I keep getting low voltage error when trying to charge.

[shirley_hkg]

Need a power supply ，to charge at high volt if necessary , and limits it at VERY low current , to bring it back to 24V .

Then , recharge at a relatively small amp during the next few cycles .

[Burgerman]

Wont work. Its worth a try but I would give it about 1% chance of them being any good.

All our chairs pull a few mA from the battery at all times. If you measure them its around 7mA to 14mA. Doesn't sound much. But thats 5 to 10Ah approx per month. 60 to 120 Ah per year. And some controllers are worse.

A couple of months then cant use 100Ah.

If the chair is left switched on in error however, then its 10 x this figure.

[foghornleghorn]

During the winter i'm not using the chair much outside and it sits in the garage. Would a battery isolator switch be a sensible addition?

[Burgerman]

Essential I would say. I dont use one though, I use an Anderson loop. Pull out the plug/loop and its isolated. Then you need to do the following.

Discharge by around 30 to 40%. Use the PL8.
Every 3 months, ideally, charge, balance, and discharge again.
If you are sure that the discharge rates are pretty equal, across groups, then 6 months is fine.

[hotwheels_75]

Appreciate the replies and the suggestions Shirley. I think it’ll take a charge, if my PSU wasn’t such a pile of junk. The errors were happening before my battery died and I suspect psu is causing the errors now.gonna replace it. Pack is upto 18V.

My chair has a bigger idle draw. Something with the 20 year old seating electronics that I plan to replace. I do have an Anderson quick connect to isolate the battery, it just didn’t get pulled. I also parked it after using it and battery was ready for a charge so didn’t have as far to drop.

[hotwheels_75]

So my battery pack is finally taking a charge, after 3 days of charging 3 mins and 25 mah at a time thanks to PL8 errors due to low pack voltage, I got it to a high enough voltage that it will take a normal charge.

I’ve been watching very closely for problems, everything seems normal, but I checked the graphs and saw internal resistance is off for two cells.... but I have no record of what that graph looked like before the pack was drained.

I have pics but need to convert from BMP format.

What should I be looking for to tell if something is wrong?

[Burgerman]

Fully charge.
Leave it a week. And choose monitor for a few mins to see all the cell voltages.
Then do a discharge test down to 2.9V. See what capacity is.

You could have charged as a CC Nickel type cell, for half an hour till the voltages were up a bit. Or just use your power supply.

I suspect that many cells will have high self discharge, and low capacity, and a short life in the future. If they were below 2 volt. Thats what happens on the hobby life packs that we run too low. So they may appear ok initially, but dont count on it just yet.

The fact that all cells are together in voltage is promising. Dont worry if cell 1 or 8 is off in resistance its because of the two long charge cables.

[hotwheels_75]

All charged and balanced. Now sitting inside, isolated. Will wait a week and recheck.

Good to know about the nickel cad trick, although I hope to never need to do that again.

Makes sense about 1 and 8. I forgot about that.

Hope to do some upgrades to the chair over the winter now. If I haven’t wrecked the pack.

[Burgerman]

I think if your stated low voltages were correct then you will not be so lucky. Low voltages has a lot of effect on cycle life you can expect in the future. If not worse. So dont get too exited just yet.

[hotwheels_75]

This is my battery fully charged, sat since Monday disconnected from chair. Seems to be holding steady in this situation.


I don’t have high hopes. I’m expecting to find some problems of some kind... it’s not my luck to have nothing go wrong.

What’s the fuel reading measure? Is it accurate?

[Burgerman]

Thats looking good. Do a discharge test. Set to 2.900v per cell, wait till it stops, post the cell voltage graph. And measured capacity when it stops. Will take a long time.

[hotwheels_75]

Ok I’ll give that a go. What discharge settings do I use?

Constant Power or Constant Current?

it was on current but I got “exceeded 120v” errors

Switched to Power and so far so good .

Discharge amps set at 3.5A

CCCV Disch = Yes

Cycles = None

End Cycling = Charge

Cool Down = 2 mins

Store chg or dsch = No

[Burgerman]

Ok I’ll give that a go. What discharge settings do I use?

Constant Power or Constant Current?
CONSTANT CURRENT.
Set to 3.75A and it will discharge at a max of 100w which about it.

it was on current but I got “exceeded 120v” errors
MAKE sure its on power supply and not on regenerative battery in the supply tab.

Switched to Power and so far so good .
No.

Discharge amps set at 3.5A
Thats OK.

CCCV Disch = Yes
No need.

Cycles = None
Correct.

Ten wait... A lot.

[hotwheels_75]

Ok switched it back. Anything above 3A and I get error 139 power exceeded 120watts

[Burgerman]

Well you shouldnt. Unless you are doing a regenerative discharge into a battery and are actually connected to a power supply. I always discharge at 3.5 to 3.75 Amps, at CC down to 2.900V on a full pack.

Maybe you have a bad connection.

[hotwheels_75]

Maybe it’s my power supply? I’m waiting for a new one to arrive so will soon find out.
I’ve triple checked all settings, it’s set to power supply, not battery, and matched to all the settings you posted earlier. Ive always gotten that error when discharging on power supply. It works fine if I connect and switch settings to 12v battery.

[hotwheels_75]

Ok finally discharged! Things seem fine, but here’s the graph. You weren’t kidding about taking a long time!

See any problems?

[Burgerman]

All looking ok. What is the capacity supposed to be? Says 80Ah out.

Headways if healthy do exactly what it says on the tin. So presumably you must have 8s x 8p 10Ah - so 64 cells, and an 80Ah pack?

[hotwheels_75]

Normally a 96AH pack, 8s 8p x 12ah

So maybe it lost some capacity?

[Burgerman]

Yes. You now have 80Ah instead of 96...

The problem is that it will deteriorate faster from now on too. Thats what happens when you run them low.

Tell me, you did have balance on discharge OFF didn't you? It seems odd that all ended together with the exact same Ah...
It may be that only one group has lost capacity, the rest were artificially pulled low to stay balanced?

If not, repeat the test and turn balance OFF for the discharge...

[hotwheels_75]

Knew there had to be an issue.

Bal discharge is off.

[Burgerman]

Yes you have lost about 15% or so of capacity. About 1000 to1500 cycles worth...

When I tested my 45V 72Ah pack, I got 70Ah out down to 2.90V .
When testing my 120Ah pack I actually got 117.5 out.
Both very close to the rated Ah.

I would have expected you to have got about 90 to 93Ah if they were 100% healthy.

[foghornleghorn]

Probably a stupid question but it's the only way to properly learn - Could they cheer up with a couple of charge/discharges or are they permanently reduced now?

[Burgerman]

Permanent. They might improve a few percent for a couple of cycles. They likely go downhill from here rather than the other way. I am surprised they are working at all, but they appear to beat least usable for now.

[hotwheels_75]

not sure if the measurements are as accurate when recharging, but I put 90-95AH back into them a few times before this happened.

If I wanted to isolate potential weak cells, do I have to take it all apart and repeat the process we do when building a pack? Charge each cell, let sit for a few weeks, recharge and measure the amount of power lost while sitting?

Is there a safety cutoff circuit that could be put inline with the power harness, so when the pack reaches critical low level it just cuts off?

[Williamclark77]

Sooo long absence, haven’t been feeling well or using my modified chair. It was out on our closed in deck. Temperatures have been freezing. Finally got to bringing the chair in to test batteries.... and store them inside. Whoever parked my chair a couple months ago never disconnected the pack. It’s now beyond dead 6v total from a 96ah 24v 8s lithium pack

I suspect it’s toast. Is there anything I can do to try and save it. I keep getting low voltage error when trying to charge.

The same thing happened to my Willchair 1. It was stored and forgotten turned on. A 14S 48v pack had 5v.

Charger wouldn't even recognize it. I applied 48v directly to the charge leads with a power supply. No balance connector. It finally took power. After 30 or so minutes I hooked up the charger properly with the balance leads. It charged. One cell group is still a tad high. I haven't gotten around to completely balancing and capacity testing yet.

Is there a safety cutoff circuit that could be put inline with the power harness, so when the pack reaches critical low level it just cuts off?

You have to be careful with something like that. It could be triggered under a heavy load. If you could find one that required the voltage to be under XX amount for XX time before it tripped. I have not seen one like that though. It can be done using an Arduino and a relay like I use as a main and emergency disconnect, but not without a bit of knowledge.