Energica battery temperature versus usable capacity after balanced charge

Energica motorcycles have this neat trick where you can retrieve the Watt hours left on its battery using a Bluetooth connection. It’s probably also on the OBDII can bus data but since this value doesn’t change that often it’s a bit more work to pin point it.

UPDATE: I now also have a lower battery temperature number. I left my bike outside overnight when the ambient temperature was around freezing (1, 0 and -1 °C) from 22:00 to 5:00 in the morning. Somewhat sadly to discover the battery pack only dropped to 7 °C minimum temperature over that time. So for now that will be the minimal value in my data collection. I created this linear regression chart from the (limited) data I have.

I don’t always check this number, however at some point someone asked me if mine was also getting lower and lower as the ambient temperature (aka weather) got colder and colder. So I checked and in summer I would typically get something around 16400 Wh. To my surprise a full balanced charge in winter only rendered around 15000 Wh. And that is where this series of tests started.

Woensdag 26/01

Battery temp 11/11 - 15/13 Celsius (start - end)
Ambient temp 11 Celsius
Home smappee charger no limit set (full 3kW)
Started charging at 71 %
Resulted in 15026 Wh
After storage for like 5 days

That was from a charge overnight the day before I would go to the office. Even more suprisingly was the result the next day at the office where I charged up again before going home. The charger used then was a 220V schuko to type2 adapter but also the garage space is heated up to 23 Celsius. And after a balanced charge it would hold 16236 Wh, very close to what I would get in summer.

Donderdag 27/01

Battery temp 19/20 - 26/27 Celsius (start - end)
Ambient temp 23 Celsius
Schuko 220V charger limited to 10A
Started charging at 33 %
Resulted in 16236 Wh
After long highway ride, same ride home in cold resulted in about 8 % more left

Could it be that easy? Just the ambient or battery temperature resulting in more capacity to be used after a charge? Cause that Wh reserve number is literally what you can use from the bikes battery. I’ve tested that enough in combination with consumption numbers while riding and it all seems to match up.

Next I had to figure out if it really was just the temperature, also what temperature, and not a difference with the charger or other elements in play. Personally I was thinking in the direction of an algorithm in code that would take a param (temp?) and use it to achieve a 100% balanced SOC figured. On Facebook Jeffrey responded right away that this could simply be the battery chemistry.

Due to covid I’m still limited to 1 day at the office so testing this would take some time. Today I have enough results to confirm it is just the battery temperature that influences this. I excluded the charger by using the same schuko adapter after letting the battery cool down and got a very similar 15026 Wh (more like exactly the same).

Donderdag 10/02

Battery temp 12/13 - 14/15 Celsius (start - end)
Ambient temp 12 Celsius
Schuko 220V charger limited to 10A
Started charging at 79 %
Resulted in 15026 Wh
Confirmed that it's not the charger

Next test was to see if having the battery temperature up to the preferred 25 Celsius was sufficient. For this I could benefit from the non cooled battery set up. Just charging for longer to let it heat up or charging DC or riding faster for a while on the highway is enough to get the battery temperature up.

So in an attempt to verify that the same day I went for a short highway ride. And indeed I could already charge up for more right after. I didn’t get it hot enough due to the very cold weather here these days. Maybe I should plot out a table of some of the more common ambient temperature values?

I can charge indoors so for me 10 Celsius is really the lowest it will ever go in the non heated but insulated garage. And for next year we’ll probably see if heating the garage also helps with range of our electric van. There is efficient floor heating, it’s just not opened up at the moment.

Donderdag 10/02

Battery temp 17/18 - 18/19 Celsius (start - end)
Ambient temp 12 Celsius
Schuko 220V charger limited to 13A
Started charging at 69 %
Resulted in 15334 Wh
Confirmed that it's the battery temperature

A week later I was again at the office so could test charging at a very comfy 23 Celsius ambient temperature. The result was the expected 16236 Wh battery reserve from last time I charged there. So the numbers are really matching up.

I’ll probably never heat up our garage to 23 Celsius but having it closer to 20 degrees is an option. And by doing so I’ll get some extra range and an overall happier battery it seems. For me I have plenty of range anyway. Where this could come in handy is where people have to choose between storing or charging the bike indoors or outdoors. Or where the range is just short of enough.

Donderdag 17/02

Battery temp 23/25 - 28/29 Celsius (start - end)
Ambient temp 23 Celsius
Schuko 220V charger limited to 10A
Started charging at 32 %
Resulted in 16236 Wh
Confirmed that it's the battery temperature

It would also be interesting to see at what point increasing temperature stops being a benefit. On this last charge for example I ended already with a battery heat close to 30 degrees Celsius. I can imagine going to 35 Celsius won’t result in even more capacity. Only one way to find out!

2 Comments on “Energica battery temperature versus usable capacity after balanced charge

    1. At least we can explain why now 😆. With the Zero I could check the Ah and that would also “degrade” over time from 114 Ah to 98 Ah or so but I never checked if that was related to temperature. Probably yes.

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