How often do you test your charger?

E-HP

10 GW
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Nov 1, 2018
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I think a few folks have invested in good battery chargers for their packs, but I suspect a lot of us have just been using the cheap generic Chinese chargers that are sometimes included with a new battery pack. I've been using mine for about 3 years now, but it never occurred to me that it might need some occasional adjusting. During the last 6 months, after switching over to my current controller and cycle analyst, I noticed on a few occasions that the fully charged pack voltage was higher than 58.8V for my 52V pack. I don't charge to full very often, so I saw this happen during the last few times that I did. I had concluded at the time that my CA was reading voltage slightly high, and put the thought off for another day, thinking I would calibrate the CA.

This weekend, I charged to 100% to allow the pack to balance, and noticed the CA was reading 59.28V, so I got out my meter to measure it. Sure enough, the charger's voltage had drifted over time and was reading high. The CA was right. I took the charger apart and adjusted down the voltage to 58.8V. I checked the voltage a few times after assembly, cycling the charger on and off a few times and it remained at 58.8V. Anyway, it didn't occur to me that these cheap chargers could drift that much, but maybe something to check once in a while.
 
I routinely use a known accurate DMM to check on all charge sources, even those costing many hundreds of dollars can't be trusted more than a month or two at a stretch.

My 60A Sterling B2B being the one exception.

And an old TDKadjustable PSU, but that's a lab quality bit of kit cost thousands when new.
 
DMM on the charger connector is all I did for my Dell laptop chargers and Meanwell's. Never used generic chargers. Now I have a Cycle Satiator for my new battery.
 
My method is to use a CA V3 on the bike, an iPhone camera and excel to keep track of battery use and charge data and do the calculations.

One use is to keep track of charge Vi, Vf, Ti and Tf, from this dT/dV is calculated for each charge and averaged for all the battery charge cycles. The average dT/dV charge is used to predict charge time, charge dT, for the next charge cycle. This system gives very repeatable results, charging is done to around Vf of 4.0 to 4.15 V/cell. I seldom charge to full charge, to balancing titration. Vf off the charger is also Vi for the next ride, though Vi for the ride is recorded just before riding.

If the charger begins to deviate from the historic dT/dV I'll notice it. So far, so good.

Ride Vi and Vf, as well as charge Vf are recorded from the CA V3. After an hour of rest after charging, usually late night, the CA V3 is reset to zero mileage and the new Vi is recorded. Next morning the new Vi is recorded again, typically the Vi will decline by about 0.2 V over night and then stabilize there.

The battery is a 52v, 20ah, 14s, 8p, the charger is the 2.5 amp charger that the vendor sent with the battery.

So, the charger gets tested each charge cycle by monitoring charge data.
 
Clearly I have some room for improvement on my battery charge monitoring. :?

I shouldn't have doubted the Cycle Analyst, since I use my display to monitor battery voltage while charging. I really didn't think the voltage would start drifting after so many charge cycles, but I guess it did not too long after I switched to the CA. Come to think of it, my old KT display was indicating 58.9V before I stopped using it, so maybe it was starting to drift.

I actually just got a new charger that arrived a day early today. Not a replacement, but I got a 5A unit for quicker charging before going out for a ride. I haven't checked the voltage yet, but since it's another cheap one, I'll have to keep a closer eye on it.
 
E-HP said:
Sure enough, the charger's voltage had drifted over time and was reading high.
I had similar experience but in the opposite direction-- my charger had drifted slightly lower. It was struggling to fully charge, to the point of not even being able to let the BMS finish balancing by not meeting the threshold. Like you, I opened the case and adjusted the pot. Took quite a few tries as it seems like there was considerable slop in the adjustment.

Question: I presume I measured the charger voltage correctly while not connected to the battery-- is this the correct way to measure charger voltage?

Voltage adjustment pot labeled VR2, turn counter-clockwise to increase voltage.
 

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Every time. I bulk charge using big power supplies. No BMS, no automation of any kind. I have to set and monitor charging myself, but it does complete in a very short time, so I am never tempted to leave for any reason.
 
MadRhino said:
Every time.

+1 I charge to quite conservative voltages 4.05V/cell and I always check voltage after the charge. I only need to charge 2-3 times/wk and when I start the charger I set an alarm on my phone to go check it and disconnect. To get to 4.2V would take over an hour additional charging, so even if my charger failed and didn't cut off I would catch it before overcharging. I had one of those chargers fail in that manner before and it killed a pack at slightly less than 5V/cell. I was lucky that the 26ah Panasonic cell were well designed and when the cells puffed and formed an arch the terminal sheered off, so there was no short to start a fire. After that, even though the failure was due to a tiny lizard getting into the charger and laying some eggs, the trust is gone, so without exception I monitor and disconnect before damage can be done by a cheap charger.
 
My new charger was registering at 58.95, so I've already adjusted it to 58.8 and my battery is currently charging. It's charging noticeably faster at 5A instead of the 2.5A for the old charger. My 6S Turnigy Graphene arrived today as well, so I'm charging them up now as well. My lipo charger has been adjusted to the 1000th of a volt. I really close to pulling the trigger on a new 52V pack, so battery/charger maintenance will be a higher priority going forward . :bigthumb:
 
I adjusted my cheap plastic 48V chargers all the way down, for better pack life. The trim pot only got me down to 54.0 volts or so, but I reckon every little bit helps. I mostly use them when I’m out of the house, because they’re light and small enough to carry one on the bike all the time.

If anyone knows a trick for adjusting the voltage down further, to 52.6V or so, I’d like to know what it is. I guess I could use a couple of power diodes on the output, but that’s a pretty crude, and hot, solution.
 
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