Forum

Limiting SoC to 80%...
 
Share:
Notifications
Clear all

Limiting SoC to 80% when charging


Soco_Sweden
Posts: 2
Topic starter
(@soco_sweden)
New Member
Joined: 1 year ago

Just as a cool project to increase the longevity of my batteries...

I have a TS and a standard charger, and have lately been experimenting with how to limit the charge of the battery to around 80%, just like they do with EV (cars) to not kill the battery prematurely, as fully charging the battery limits the number of charging cycles it can handle, degradation sets in quicker.

Last year I used a Z-wave controlled plug, between the outlet and the charger, it was without power metering, and one click gave two hours of charging (adding around +20-30% SoC, State of Charge) and two clicks gave four hours of charging (adding +50-70% Soc), I don't remember the exact numbers it added, but something like that.

So depending on SoC when starting the charging, you either clicked once or twice on the plug, to end up around 80% SoC. It worked really well!

But as you know, there are always things to improve to reach perfection!

This year, I have a power metering plug for Z-wave, and after experimenting last week, the charger usually uses around 300 Watts to charge in the range of 0-70% SoC, and when it reaches around 80-85% SoC, the charger usage has dropped to 150 Watts, and that I use as a cut-off point (if you single-clicked the plug to start it). That seems to always give me around 80-85% SoC. Job done!

To add to this:

If you double-click, it keeps pumping for five hours (assuming you want to get the battery 100% full due to a long drive next time..., without any cut-off due to watt measurement. I can easily add more time if that is needed, of course, e.g. to go from 0% to 100% SoC, but I think 5 hours is a good starting point and it won't be often I need to do that.

I also added this feature:

If the power usage after starting the plug does not go above 150W within the first five minutes, I cut the power to the plug too, as it is likely not connected to the battery, so no need to keep the charger on.

Of course the system emails me when the charging is done or if the charger is turned of for any reason.

Sweet, hey?!?

Even cooler, would of course be if Super Soco could add charging limits to the bike itself. Just like EVs have!

Equipment list:

I use a Vera Plus Z-wave gateway and a Telldus power metering plug, but it is a bit crappy so a Fibaro is on its way!
I set the plug to report every minute (read the manual), rather than the default 10 min reporting.
I use PLEG, a plugin for a few Euro, to gain full control over the plug and which actions to take.


Can share screenshots of config if anyone has the same setup.

Best regards,
Tomas

2 Replies
socomods
Posts: 96
(@socomods)
Trusted Member
Joined: 2 years ago

the battery is already supposed to have its charge capacity limited to increase lifespan✌️ (via its BMS)

 

that claim would seem to tally with the max 70V the controller accepts, 17p 18650 max voltage is 71.4V

 

did you read the voltage at full charge, before doing your own limiting? (assuming its a new-ish battery that can reach its full charge anyway)

 

Reply
1 Reply
Soco_Sweden
(@soco_sweden)
Joined: 1 year ago

New Member
Posts: 2

@socomods
Yes, the charger has 71.4 Volt output, I have no idea at which voltage the charger stops charging. The battery had 69,5 Volt at SoC 88% earlier this week.

If the BMS already keeps the battery in the <90% max SoC, very good! However, by me cutting it even sooner, let's say 150W charging leaves 85% according to the display on the Soco, assuming that would correspond to 75-80% true SoC, I'm losing available range, but I'm EVEN MORE nice to the battery.

This is the third summer coming up with our Soco, we got it in May 2018, and it has 4020 km on the clock and the battery still has decent range, if it is above +7°C. Below that temp, the range really suffers and you should not even charge the battery near or below freezing, also printed in the manual.

So, if your point is that it is not necessary to limit the charging like I do, I understand your view, but I will keep doing it anyway, as I find it interesting and a fun project.

/Tomas

Reply
Share: