Hello all, haven't been posting or riding my xb600 modded to 72v lately. Yestarday was going to ride it and determined my batteries had run down to nothing. I forgot to charge it recently so they were died. Big mistake for lead acid batteries. I charged them up when I was gone and forgot about them. Just remembered this morning. Checked it and the charger never turned off, so they charged for about 24 hours I think. Unless it turned off and back on over night as the batteries dissipated some power. I checked the kilowatt meter I have and it said it had delivered 3.1kw since I hooked it up yesterday. The batteries were warm to the touch but didn't smell and the two under the seat don't appear to be bulged. Haven't check the others. My question is how many watts of power should a normal 6 pack of batteries receive to be fully charged. I am using 6 stock xb600 20 amp batteries.
Any ideas as to what I can do to test the bike to make sure I don't have any bad batteries. The charger should have turned off so it may mean I have and unbalanced pack.
Also if the charger is a 2amp charger shouldn't it have delivered about 5.7kw over a 24 hour period if it was always on. ( 120v times 2 amps is 240 watts an hour times 24 hours) that would be 5.7kw of power? Unless I am misunderstanding the way the charger works.
the current rating of most chargers is the output to the batteries.
so 2A * ~82v / 0.8 eff = 205W
24 hours would be 4.92 kwh.
sounds like you hit thermal runaway, where the charge current in the first constant voltage phase didn't fall sufficiently to terminate the charge.
the easiest way to test if you have lost capacity is to ride the bike and see if you still have the same range as before.
overcharging won't cause balance issues (all batteries will still be fully charged) but their capacities may be more different to each other.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
A single 20 AH 12V battery has .24 KWH at the 20 hour rate. Six would have 1.44 KWH. Allowing 30% for inefficiencies, a TOTAL charge would be about 2 KWH. Of course, your batteries probably weren't absolutely flat (you'd better hope they weren't). If they were at 50% SOC, they would only need .7 KWH to reach full.
The excess electrical energy went into turning water in your electrolyte into hydrogen and oxygen. The now surplus gas then vented from the cells. Like cats, batteries have nine lives (there is some excess electrolyte built into each cell). Yours probably have one less life left. Watch voltage, and, when the pack voltage gets to 66V, test the individual cells UNDER LOAD. If one is dramatically lower in capacity than the others, you'll see it then.
Mark
Thanks for the help on this. So if I understand correctly. It would take about 10 hours to fully charge a completely dead battery pack, but if the pack was 50 percent discharged it would be about 5 hours to fully charge figuring in the 30 percent inefficiencies. Correct?
That being said any idea why it showed 3.1 kWh on the kilowatt meter. I would have thought it would have been much higher for as long as it was plugged in.I also noticed that the killawatt meter being plugged into the charger draws power even if it isn't connected to the bike. So some of that 3.1kwh figure is the charger itself drawing power.
Any idea why the charger didn't shut off correctly?
I guess I will start driving it around and see if I get the same speed and distance I am use to getting before this happen.
Yup.
You asked:
I think antiscab's reconstruction is probably correct. If one of your batteries was failing to get to full voltage, the charger would only see that the pack needed more juice and keep pumping in electrons. I suggested one way to check the pack for a weak cell. You might also separately charge each battery with a good 12V charger and verify that each accepted a charge and had a similar charged resting voltage. My pack charges to a peak voltage (on the charger's uncalibrated on-board voltmeter) of 14.6V/battery and has a resting voltage of 13.2V or so.
Also,
That's good news. I would infer that it HAD throttled back from full charge for part of the cycle. What was the watt draw when you got out to remove the charger?
A normal 3-stage charger will:
As to drawing power even when not charging, you are right. However, it is (or should be) a very small idle drain that would not amount to that extra 1.5 KWH.
Mark
I didn't look at the watt draw. I unplugged it after I saw it had 3.1khw. I did ride the bike today for about 2 miles with no problems. Same top speed of around 30mph. I need to see were the pack voltage is on a voltmeter now. The gauge on the bike still reads above the H. So it didn't seem to drain down very much on my 2 mile ride. I am going to ride it about 20 miles over the next couple of days without charging. If it does that then it is fine I think. I will then charge each battery individual to test them and the balance the pack once again. Then see if the 72v charger I have will work correctly again.