48v 12Ah battery pack?

[Hardcore]

hey all, can someone help me with this so I can send a solution to gm instead of problem?

Problem: Range is decreasing

Tests show: 54v fully charged
48v after cut off and after 12 hours it is 49v-50v
Then it charges to 54v

Wheater: Dry and 10-30 Celsius

Range on 16 aug 2010: 14 km 37,6km/h average
Range on 23 aug 2010: 12 km 38,2km/h average

[Leslie]

Try leave the pack on charger for three days with no riding and see if it improves.

If you see no improvement ride it flat 7kms out and 7kms home and get one of those timers and set it to charge on and off every 15 mins and then after 12 hours of charge hours total try ride it again.

If no luck email TOM.

[Hardcore]

I'll try that, first i'll leave in on charge for 3 days and I will test the range after that.
If that didn't help i'll try your second methode and get one of those timers, uhm I am confused about what you mean. Maybe if I ask a local shop for that kind of stuff.

But I would first of all like to thank you for the fast reply

Sincerely,

Kevin

[Leslie]

You can set timers to turn on and off in intervals,  Maybe 30 mins on and 15 mins off for 16 hours and set it to stay on for 8 hours after this 16 hour cycle has completed, just to allow the cells and BMS to cool down.  This gives the high cells time to level out and cool down if they get too high.

I name it cold bulk charging I used it about 2 years ago to balance SLA cells with amazing results and works best on a flat pack.. You may find reference to my post I did here or ES.

The BMS may be HVC one of the high cells and hault the charging process..  Pack just keeps getting worse.

A fully charged pack should turn green straight away if you were to unplug the pack and plug it back in 5 mins latter but a out of balance pack even if you charger light is green will take some time to go green if you were to repeat the unplug and plug back in thing.

Well the timer does just this. Allows more time for the charger to remain at many different voltages all the way up to 56.4v

Just before it is full charged the timer may allow the pack to go right up to max charge 5 times before the pack is truley charged

Another method is to charge to ful go for a 10 min ride strip the surface charge off the high cells then charge again.  And keep doing it until the battery stops jumping up in volts so fast to the end.

Remember it took you 12 hours and then it all of a sudden was full.  Well you want it to charge normal.

Its sad but I do think some of you cells are defucnt.

If your lucky it may be badly out of balance.

The last method is try to detect the low cell and carefully hook up an old mobile charger for LIPO cells to the BMS B connections on the effected cells blocks and individually charge this block.

After youve done all this there is not much more you can do but replace the bad cells.

[Leslie]

The timer owns the leave on for three days as it allows the cells to cool during the initial bulk modes..

If the timer works maybe do it for a few times after rides.

I would do both.

Use the timer first to get a cold bulk charge then leave on for three days.

Another thing I do sometimes is I slow down the charge rate.  I got one of these AC 240v timer and set it to charger over 12 hours, in that 12 hours it turns off 6 times, charge for 1 hour, settle for 1 hour, on, off, on, off, etc.... My batts uninterupted take about 5 hours max to charge.  I find this is really good to do for my SLA's as they balance better.  I missed doing a batt terminal up tight 2 days ago installing a new box, and it shook a little loose. One battery with the loose terminal seemed to be out of balance and I was losing speed and distance in one long ride,  it seems also the one that has the less capacity in the series does tend to be the one battery is left floating over the max specified charge voltage when charge has completed.  This problem tends to make charging shorter and the pauses increase charging time with less force on the any particular battery.  Sure things fix themselves up in a few rides with SLA's but this seems to fix things up faster and better.  I often use the timer when I put the bike to bed for more than 12 hours and set it to do another charge first thing in the morning for two hours, I avoid float as often as I can,  When things get out balance float charge seem to keep the voltage memory out of whack so the on off method is very very good and I seem to get very good milage, power, and speed from this.  Is it just me or does the SLA seem very saggy when its allowed to sit on a float for a long time?

October 2008.  I used this method often until I built an SLA bms to balance each SLA.  I,d still do it if I had a timer.  It crapped out on a power transformer those timers don't like the old school inductive heavy power transformers.  Timers are sweet with the GM charger or pre rectified switchmodes.

[Leslie]

Actually I think I will use the timer method on my pack for its first charge but I will use the timer for three days. before I use the pack.  It cant hurt the battery, in fact IMO it is less harmfull than a normal charge cycle especially if you have a good BMS protecting the high cells.

With my SLA's I had no BMS and it worked the charm.  I think the batteries were balanced before it even got to full.

And for GM chargers. GM recommend having your pack plugged in before turning on/off the charger at the mains so the timer its not going to be out of GMs recommendations.

[Spacey]

Which battery are you using?

Something is not right as I've managed 38 km and that's with using my modded monster controller. I do have Headway 12ah cells though which can put out 100mps continuous if needed but hold their voltage beuatifully, hardly any sag.

[Hardcore]

I'm using the Gm's 48v 12ah pack, so indeed around 15 km is a very poor range for 12Ah. I ones also could do about 30 to 40 km with little or no pedaling and I miss those times 

[Hardcore]

Also I think I got the fastest reply by gm, it took them just 4 hours to answer. So improvement is coming, I think

[Leslie]

How's the pack going Hardcore?  

Day 2 and we all live in hope this can save your GM pack.
 

[Hardcore]

The cold bulk charge is completed and it's now on charge for 1 day, so 2 more days and the 3 day charge is completed.
I moniter the voltage but it hasn't been changing. Also I can't see diggits like ,6 or so it's just 54v not 54,6v so I don't know the excact voltage but I believe it's good. On monday I will do a test run to measure the range and see if it indeed saved my gm pack. If not then i'll need to find the faulty cells and get some replaced by GM.

[Leslie]

The cold bulk charge is completed and it's now on charge for 1 day, so 2 more days and the 3 day charge is completed.
I moniter the voltage but it hasn't been changing. Also I can't see diggits like ,6 or so it's just 54v not 54,6v so I don't know the excact voltage but I believe it's good. On monday I will do a test run to measure the range and see if it indeed saved my gm pack. If not then i'll need to find the faulty cells and get some replaced by GM.

I do hope this hasn't wasted your time.  

Did you notice that the every time with the cold bulk charge the green light would come on sooner on each timer switch on?

[Leslie]

A flat cell is very hard to pick with these types of batts.  If your pack was out of balance it sure wont be when you finished.

If you notice good power and speed on the take offs when you first ride this is a good sign.

If you even notice 8kms range improvement do cold bulk charge and repeat the job.  You may not need to wait three days though.  If its worse again and keeps getting worse.

Then