This isn’t necessarily bad (like others have already pointed out). If I were you, I’d keep riding it like normal and just keep an eye on the voltage that full charge is. If you start to see it decrease from 58.1v to something lower like 57.9v / 57.8v over the course of a few weeks, then you might have an issue that is worth investigating.
As it is now, just ride the board and have fun. I wouldn’t be concerned over it.
I really appreciate the input, I’ve had the board a few months and the max charge voltage has not changed in that time. It’s winter here but now I’ve got esk8 in the blood so in place of riding, I’ve been reading and the subject of battery fires comes up every so often which got me questioning the safety of my battery. The logical part of my brain says ‘there are millions of battery packs in existence so fires are actually REALLY rare’. But some of these stories and footage of batteries in thermal runaway made me concerned my charge voltage being a tiny bit low might indicate catastrophic issue with my battery. Commenters like yourself have really helped ease my mind. Thanks! Thanks to everyone who’ve replied!
I hear you on the battery being a worry.
I have 3 low $ low quality premades, one with a 7s2p battery., 2 with 7s1p batteries.
One was bought as a non operational parts only board
When it arrived I checked the battery voltage on charge port, 23.98v, 6 cells were @ 4v, one was 0.025v. The BMS had nickle strip spot welded to the solder pads, and the dead cell balance lead was a missed spotweld which blew a hole through the strip and burnt the PCB. The cells are BFN, 2000mah, 10 amp max. Ive made them into 2 11.1v nominal 3s1p packs with non balancing BMS. One of them I added a JST plug, to easily monitor individual cell voltages, and balance accordingly, and over 5 slow dis and recharges the VDelta is over 50mV. I manually top balance to within 6mv, and the cells just drift far faster from this than i would expect innsuch light duty use.
During charging, one cell always hits 4.20v first about 30 to 150mV ahead of the others, and I am limiting it to 12.56v or so. Often, the pack is still accepting 0.25amps when I say no more, you are done. The bms says 4.25v +/- 0.05 for high voltage protection to kick in, so potentially the one high cell could hit 4.3v
The other 3s pack, without the JST plug, i limit it to 12.3v, and i noticed the bms tripped once during higher amp charging, which indicates even with an average of 4.1v per cell max charge voltage, one cell hit at least 4.25v and triggered the BMS HVD.
I might go rip off the kapton tape and add a JST plug now so I can see how bad this pack has drifted.
It should be noted that these 6 BFN cells were all 4.00v +/- 0.02 v when i disassembled the pack, and the same 5 weeks later when i reassembled them into two 3s1p packs. I domt have a battery impedence tester but i figured the cells were fairly well matched by how closely they stayed in voltage resting alone for 5 weeks.
The 7s2p battery in my faster cheap junk skate, I had the esc disconnected during charging once, measuring voltage on the XT60, and with charging source set at 29.39v, and battery accepting 0.4 amps still, the XT60 meaSured only 28.98v. That seemed to be too much of a disparity even if BMS was bleeding off some voltage from the higher P packs, unless they too are very unbalanced.
Later, on I cut off the heatshrink from around the BMS to have a look, and the balance wires were all crumpled together, a few mm away from the edges of the sharp nickel strip a MM away. Reluctantly i returned it to service, but I added some fishpaper to further insulate the nickle strip and balance leads from each other.
I mentioned I have 3 junky low$ 7s skates. 2 functional.
They all came with 1.5 amp 29.4v chargers, and while they do meet the 1.5amp figure, they all output no less than 29.87v no load, after a few uses. the first time i checked no load voltage they all were over 30, one at 30.11v. One skate has an always live charge port, and the included charger will happily charge it to 29.87v.
Also all three chargers go from red light to green light, as soon as amperage falls from 0.33 to 0.31 amps. They do not stop charging when red light goes green.
I use a xl4015 voltage bucker inline on these ACDC chargers to limit them to no more than 29.39v, and will often reduce charge amperage from the 1.5max to as low as 0.25 amps when time to recharge is not a factor.
I never Charge without one of these wattmeters inline on the DC OUTPUT.
Knowing voltage is good, but only tells part of the story.
How much amperage is the battery accepting at that charge voltage, tells much much more of the story.
Though an imperfect analogy, I equate knowing only the target voltage with knowing how fast ones car can go, not how fast it is actually going, much less how far it has traveled, or how far it still has to go.
That wattmeter above can fill in most all the blanks, with pretty good accuracy and precision, but should not be trusted to read accurate under 0.1amp, and might not even acknowledge a 0.05 amp load.
But the 0.1 to 40amp range seems pretty accurate among the many wattmeters i have employed over the years.
They also count amp hours so one can guestimate how much of the battery they used, and with time and many observations get a pretty good read on the battery’s ‘personality’ as it ages.
Those observations might allow the observer to see a giant red flag, well before some other indicators might arise.
I’m looking forward to my first smart BMS and the extra data it can provide, but I will always use the wattmeter inline inbetween charging source and battery as well.
Regarding my three 29.4v power supply /chargers, all being 0.5v above that I saw this on a 7s BMS spec sheet, particularly the ‘30vdc’ recommended charge Voltage.
I also saw a YTvideo, IIRC, Regarding an Exway premade 10s board, the chaRger provided with it said 42.5v on it.
I’d enjoy input from the more knowledgeable member on this disparity of max safe charge voltage vs the charger’s unloaded/open circuit voltage often being well above this.
Thanks for taking the time to share your experiences,it was enlightening! I’m definitely going to get a watt meter for the DC output of my charger.
