Battery Replacement Circuitry

[Hunka Hunka Burning Love]

With modern laptops, most are able to tell you when you need to replace the battery.  On my Lenovo X220 tablet laptop, there's a mode to "recondition" the battery pack if it's getting long in the tooth.  On a EUC, they apparently will start low battery tiltback sooner, start acting wonky (the shakes), or just drop you dead in the middle of a ride (looking at you @noisycarlos).  How difficult would it to be to incorporate a battery drain monitor to keep track of the health of the battery pack in order to issue a warning to the rider that impending doom is near without killing them by shutting off while climbing a steep hill?  As our rides get older over the months, the batteries will age and start reaching their lifetime ratings.  Some will upgrade before that happens, but sooner or later individual cells will start dying so someone will be getting a surprise. 

What's to prevent riders from dying or getting injured as a result?  Maybe a smart BMS could issue a warning to the controller board that things are going south or detect when certain cells aren't responding well to balance charging?  Considering you can get complete 4K Android TV boxes running Kodi with the latest hardware video chips for about $40, you would think they could smarten up these controller boards to do something as simple as battery life monitoring without incurring a huge expense?

 

[Chriull]

I am hoping to get some "battery monitoring" like you mention working by analysing the wheellog data files. But first i have to gather same more data and find time (and some more ideas) to try out if i get something working in this direction. I am quite sure that there should be quite some nice analysis and alarms possible...

 

[noisycarlos]

Yeah. That would be nice. I read somewhere that the NB S2 has some diagnostics, but I don't know the details, or if it includes the battery (could be just for the unit itself).

[flass]

Actually, from what I have heard it is not very easy to determine the capacity level of a battery, with a high degree of reliability.

[flass]

Quoted from: http://modernsurvivalblog.com/alternative-energy/battery-state-of-charge-chart/ 
(I cannot vouch for the correctness of this information)

Note: Voltage measurements are only approximate to determine SOC, and measuring battery voltage is NOT the most accurate way to do this (there are variables under varying circumstances). A more accurate method is to measure the specific gravity of each cell within the battery, however for many batteries this is difficult or impossible (AGM batteries, for example). Many (most) alt-energy systems incorporate a DC-shunt which keeps track of SOC by monitoring the current flow in and out of the battery or battery bank, which is a very accurate way to track state-of-charge.

Note: For best accuracy when measuring battery voltage, the battery must be in ‘open circuit’ condition (at rest). This means that the battery must NOT be under load and it must NOT be charging. To be somewhat accurate, the battery should be in that condition for an hour or two before taking a measurement, while for a more accurate measurement you should wait 6 hours up to 24 hours.

Note: Battery voltages are temperature dependent.

[HEC]

For example Inmotion has Battery check as a part of wheel Diagnostic option in the mobile app. Considering the additional "AUX" 5 wires going from the battery pack to the CB it might me advanced enough to detect early the aging cells or other serious issues with the battery pack.