15S Li-ion thoughts?

[Bbbbrass]

There are obvious BMS and balancing hurdles, but what would people think about using a 15S setup for a controller with components rated up to 60V?

My charger would top at 59V, so 3.9V per cell. My thought would be this would keep them in the healthy discharge curve for longer (stopping at 3.4V) than a 14S setup. Has anyone tried this?

 

[amberwolf]

Plenty of people have run controllers at their max ratings, with the expected success to smoke ratio.

The thing about max ratings is that they're not an absolute exact thing because of parts tolerances, and circuit designs mean sometimes you get voltage spikes in some sitautions that exceed the input voltage...if they are enough past the max rating the part can either fail outright, or be damaged in various ways, some of which may not matter or just degrade performance, and some of which may cause failure later.

So...it will probably work fine...but it might not always do so.

 

[lnanek]

Yeah, I once plugged a 72V battery into my Grin Technologies Baserunner controller with a 60V max through a DC-DC converter set to exactly 59V. Not super different from your plan to just not fully charge your battery.

Just kept getting over voltage faults, despite hours messing with the settings. Tried both just adjusting max voltages, and against the manual's recommendation, the base system voltage that all the other voltage settings are evaluated against. Doesn't help that the programming app will undo some settings if you exceed specs and not let you completely disable others.

Eventually just gave up and decided it was easier to atomize the battery and rebuild it to a supported voltage.

 

[Bbbbrass]

Yeah, I get that issue. I figure I’m already at 58.8 with a 14S getting the full 4.2 per cell, so I wasn’t concerned about the controller as much.

How do you think the cells would like a 15S setup?

 

[leffex]

Yeah, staying with your 14s setup is enough and you don't have to worry about charging the full way. That is the fastest and quickest way.

Sure, you could add a small group of 4 or 5 cells in parallel on the outside if the pack but in my experience you always fail one day with some kind of fault or error leading to something that may not be fun at all times. It has happend me too many times and in many diffrenet areas. Aquarium on fire anyone?

 

[999zip999]

Quit thinking about it and just make it easy on yourself.
It's more common making it cheaper to go with the 14s.