My experience with the Power Queen battery was not so simple. I used a little hobby charger I've had for a few years to charge it. I discovered this would only charge at ~4A so it was a slow process. To discharge I hooked the battery up to a small 12V-110AC inverter, a Kill-A-Watt, and a 250W heat lamp. I knew this would be a crude measure of discharge energy since the inverter efficiency is unknown, but I thought the charger's measure of input energy would be accurate. Unfortunately, that wasn't true! After a full discharge, the charger showed 116Ah to fill it. There is no way a 100Ah battery would have that much extra capacity, so I knew a real test would need to wait until my battery meter with shunt arrived.
One odd thing I noticed though, was that the battery would shut off charging at ~14.0V, while I expected more like 15.0V. BMS's have a function to shut off charging if a cell voltage gets too high. This is safety function and is typically ~3.75V per cell. Note that these batteries have 4 cells in series. I got the manual out and saw that PQ recommends setting the charge controller to 14.4V +-.2V, and you never want the BMS to cut out before the charge controller... so something wasn't right. I posted on the DIY Solar Power Forum, and was advised to set it to charge at a fixed voltage that was just under the point where the BMS trips. This would hopefully activate the BMS balance function. My charger wouldn't allow setting a voltage, but I repeatedly charged the battery in the 13.7-14.0 range at 0.1A, so that it accumulated at least a couple hours in this range, with no improvement.
Once my meter arrived I was able to do a good capacity test, and that was fine... 106Ah! Actually that is a bit extreme for a 100Ah battery which made me wonder if it had 100Ah cells, or cells of a higher capacity that were degraded or rejects. At any rate despite the high capacity, if one or more of the cells are out of balance, and the BMS doesn't fix this, it is likely to get worse. And it's in a sealed box so I can't balance it myself. For a battery that is supposed to last 10 years, this isn't good.
I got the solar charge controller (Epever Tracer), the battery monitor (Qwork), and associated wiring, circuit breakers, and fuses installed in the camper, and connected the PQ battery in parallel with the GoKWh. After a brief check at home, I took a 2 week camping trip to Big Bend and the Terlingua TX area. The plan where the PQ battery was concerned, was to set the max charge to 13.9V and "boost" charge to 13.8V (for 180 minutes, the longest setting). Since I had plenty of solar for the energy I was using (mostly a laptop), this gave me 3 hours per day of holding the battery just below the point where the BMS was shutting off the charge. If the BMS was ever going to balance the cells, this should do it.
But... when I got home from that trip I tested the PQ battery again and the BMS was shutting off at 13.9V now rather than 14.0V. Getting worse. So I contacted PQ to see what they said. Their standard questions when there is a problem are "what charge controller do you use?" and "what is the settled voltage of the battery after charging?"... which is the voltage after you let it sit for an hour or so. Neither of these was relevant to my issue, but I gave them the info, and then they asked for a video of the behavior, which I supplied. I also asked them if the BMS even has a balancing function, and if so what are the parameters for it to balance the cells?... details of its operation. I was still trying to come up with a way to fix it, rather than send it back, or at least understand what was wrong. The first two times I asked the question I was ignored, but finally I got a reply that they would not tell me how the BMS operated, except to say that it cuts off charging if one of the cells exceeds 3.65V. If all 4 cells were in perfect balance this adds up to 14.6V. Since the BMS is a protection mechanism, and their own manual recommends setting the charge controller as high 14.6V, and you never want the BMS to terminate while the charge controller is functioning... I doubt it's that low. 3.75V or so is typical, or 15.0V for a perfectly balanced 4 cell battery. Anyway, I'm not getting close to 14.6V, and the situation is worsening despite doing everything I can think of to help it. Meanwhile they kept telling me that if the battery settles to 13.3V or more then it's totally fine, fully charged, no worries. This is also not true. You can look up LiFePO4 battery voltage vs charge level and all the charts will show you that the curve is very flat, and also that 13.3V for a 4 cell battery is probably in the 80-90% range for charge level. I didn't mention that I was able to get 106Ah out of it prior to the trip (I didn't test it after). But that's irrelevant IMO. The battery is supposed to last for 10 years and many thousands of charge cycles and if the BMS balancing function doesn't work, the odds of that happening are nil.
I started the return process through Amazon on the last possible day. There was some weirdness with that also, as the return label came from PQ directly, and they told me not to use an Amazon label as "Amazon would charge me too much". The label they sent said "postage due", and I thought the return shipping should be free for defective merchandise. More emails with PQ. They eventually agreed to send me a prepaid label, but they never agreed that the battery was defective, maintaining throughout that it was fine. They also said that they were going to replace it, rather than refund my money. I twice told them that I wanted a refund, not a replacement since if the new battery behaved in the same way, it would also be returned. Also when I initially requested the return with Amazon, a refund to my CC was the listed resolution, not a replacement. I was confused about what was going on and still am, but a day after I shipped the battery I got an email from Amazon stating that my original CC charge had been refunded. A day later I got an email from PQ stating the same.
I took a closer look at all the reviews on Amazon and discovered that nobody really tests them. One person actually bragged that the voltage went to 13.9V... not realizing that it should have gone to ~15.0 before shutting off. "It works!" is about all you can glean from the positive reviews, and the negative ones are mostly total failures. Also because different varieties of batteries are sold from the same page, and the Trolling model was fairly new, there were few reviews of it, and no indication that it was actually tested. There are youtube reviews of the LiTime version of the same battery, but they did not check the maximum voltage or balance of the cells.
Based on my experience with Power Queen, and their repeated insistence that the battery was fine even though it clearly wasn't, I think that the "5 year warranty" they state is not worth much. If I'd bought from them directly, I'm pretty certain they wouldn't have taken it back. At some point down the road if the battery completely died in under 5 years, they may have given me a prorated replacement with shipping at my expense. They have US warehouses, have been in business a couple years, have mostly great Amazon reviews, as well as good youtube reviews, and still... your best warranty is with Amazon, and it typically lasts for only 30 days.
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The moral of this story is to have the means on hand to test your battery as soon as you get it! I think most of us will have a battery monitor, and all of us should have a solar charge controller. I you lack a monitor you can drain it until the BMS cuts off, then hook it up to solar and charge it (with no loads!) until the BMS cuts off charging again. Be sure to set the controller limits high enough so this happens. Note the Whrs or Ahrs it took and compare to specs, and also check that the battery achieved spec voltage (at least 3.65V per cell). If you have to watch it to find the cutoff point (like me!), then let it fully charge and settle for a while, or give it a brief load to reset the BMS disconnect, and charge it again. It will take very little for it to max out this time because it's already full. If these tests results are fine then at least you know the cells are balanced and the capacity is alright, and BMS is probably working correctly at the start.
If you have low temp protection and you plan to use it, it's good to test that as well... but it isn't easy especially if you can't take the battery apart. BT is helpful in that case, because at least the settings are shown. Otherwise you need to stick it in the freezer... but not at 0F, rather at something in the high 20s at least, and let it saturate. Since the only freezer I have is the one in my house, and I keep food at 0F, that one would be tough...
Or you roll the dice and hope for the best... or go with a company that really stands behind their product, and will guarantee to replace the battery completely free of charge or shipping costs, for any defect, for at least 1 year... better 2. Are there any of those?
ipowerqueen.com
