72 volt ebike maximum voltage/nominal voltage

[johnnyz]

Hi there

I already have a recumbent trike with 92 volt Lifepo4 and its awesome. I decided to buy a really cool looking Motorino XMR. This is a 72 volt 20 ah SLA version.

Question: While charging up the cells, the "smart charger" supplied indicated voltage at 89 volts and still not fully charged so I disconnected. Lifepo4 I know but these cells....seems to me that maximum voltage per cell should be around 14.7...so this charger was getting each cell over 14.8...Resting voltage after sitting for hour is 80.

What is the maximum charge voltage the charger should charge to?...I hate these cheap chinese controllers but thats what came with an otherwise quality ebike. Unbridled it tops out at 57 or so kph which for now (until I replace these cells with Lifepo4 and controller) is ok, as it gets up and goes pretty good.

Thanks


John

 

[wesnewell]

If your charger is charging the pack to 89V it's over charging the cells. Typical fully charged sla cell is 2.25V, but that varies with ambient temp. During charge, most chargers provide ~2.45V per cell until the battery won't take any more current. It then shuts off and/or goes into float mode to maintain battery voltage at full charge . So if you measured 89V while charging that's a little high but not that far off. If the charger is not shutting off, it will burn up your batteries in a fairly short time.
https://en.wikipedia.org/wiki/Lead%E2%80%93acid_battery#Voltages_for_common_usages

 

[johnnyz]

Thanks for the response. That's what I thought as well...it's funny..a $3000 ebike and a cheap cheap Chinese charger...something is amiss...

After driving an average of 30 kph for 30 kms, voltage still read 75. I think that I actually pretty good considering...also, I noted that voltage sag is very minimal when fully charged, they went from 79 volts under full throttle to about 75.

I think I am going to have a talk with the vendor...


John

 

[dogman dan]

Lets just back up one step.

You know the voltage how? Your multimeter? It's possible it just needs a battery, they read high when the bat is low. Dash display? Is it accurate?

Just saying, it could be just a bogus reading. But if your charger really is putting out way too much, you should be able to open it up, and dial it down some.

Look for an adjustable pot, right by the DC output wire.

 

[johnnyz]

Lets just back up one step.

You know the voltage how? Your multimeter? It's possible it just needs a battery, they read high when the bat is low. Dash display? Is it accurate?

Just saying, it could be just a bogus reading. But if your charger really is putting out way too much, you should be able to open it up, and dial it down some.

Look for an adjustable pot, right by the DC output wire.

The dash has a voltmeter and I used that. I referenced this by taking off the side panel and referencing the batteries with my voltmeter. This time, it stopped at 88.5 volts for about an hour and then shut off...looks like 14.75 volts for each battery. So looks like its ok.
I have to say this thing is pretty good..great handling great brakes and even with the limited controller (pulls max of 35 amps) and SLA batteries gets up and goes quite good...speed about 55 kph...If i put 92 volts of headways and a Crystalyte controller pulling 65 amps into this thing..well..without knowing the wind of the motor im guessing minimum another 10 kph and much more torque and greater range. I have already done 30 kms on this thing and the voltage read 74.5 starting from 79.5..so it was probably good for another 10-15 kms for sure and thats pretty good for SLA.

Any opinions or thoughts would be much appreciated.

John

 

[eee291]

You want to know my thoughts?

Damm I'm jealous :x


But on a serious note, I would dump those SLAs in a heartbeat, maybe even opt for a 100 amp Powervelocity sine wave controller with 130% overspeed

 

[dogman dan]

I'd be inclined to turn that charger down, to more like 13.5-13.75v per brick. I think that's cooking them. Once they die, lipo that sucker.

Those things are cool, Jason (of e bike kit) has one. Purely a fun toy for him. But if you had a fairly short, no highway commute it would make you want to work more often.

I finally broke down, and got a gas scoot. does 90mph. Need for speed finally satisfied. It's costing me 12 cents a mile, while e bikes have run 20-30 cents because of battery costs. No commute, purely a toy.

 

[johnnyz]

I'd be inclined to turn that charger down, to more like 13.5-13.75v per brick. I think that's cooking them. Once they die, lipo that sucker.

Those things are cool, Jason (of e bike kit) has one. Purely a fun toy for him. But if you had a fairly short, no highway commute it would make you want to work more often.

I finally broke down, and got a gas scoot. does 90mph. Need for speed finally satisfied. It's costing me 12 cents a mile, while e bikes have run 20-30 cents because of battery costs. No commute, purely a toy.

Right now im ok with the SLA's...but 14.7 volts is the voltage to charge them at...even my RC charger will charge my little 10 ah pb battery to 14.7 volts...so this thing is technically overcharging them by a little bit(14.8).

Im thinking of taking the headway cells in my trike (28 x 3.3=93 volts) and the 18 fet controller (which can pull 65 amps vs 30 amps max for the one on the bike) and modifying this sucker..Im thinking it will be at least 10 kms an hour faster,a bit more range but loads more torque as my trike pulls 3 times as hard as this bike does with the Crystalyte H4080 hub motor on a 24 wheel.

Speaking of which...I noticed that even on 90 degree days and driving wide open for more than 30 mins the motor side plates are not even warm..where the H4080 sometimes is so hot you cannot touch the side plates...this motor is huge and wide so I am thinking it can take lots of volts and amps..( ill be checking the thickness of the phase wires later today)..heres a picture if anyone knows anything about this motor...Motorino wont tell me squat.





Thanks

John