Battery charge levels

[djangoW]

Who monitors their battery level? Who leaves battery on trickle? Who still needs to even when driven regularly? Who swears they never need charging if driven regularly? How long should a Li-ion battery last? Opinion seems split: "Never charged, never needed" v "Always should be left on trickle to 'maintain' charge". "Lasted 6 weeks unused", "went flat in 2 weeks"... confusing ...

Just purchased a 650s spider. At 96% when collected. 72% piqued my interest when I noticed ... dropped despite over 14 days driving regularly. Now even after 1 hour drive wont recharge (without trickle) in car above 79%. Another hour return drive, same.

Is this normal? Is the vattery "getting old, wont hold last 20% charge"?
If it hovers 50-75% surely thats ok, no trickle required unless leaving multiple weeks, 2+ I am thinking.

Why wont car recharge nearer 100%? I wonder.

Of course, even non li-ion batteries have a lifetime and will need replacing. I know what phone batteries are like.

Any thoughts, experiences?

[davek_964]

Generally, mine always seems to be about 95%. Even if I leave it a week without charge it doesn't drop below that much and stays above 90%.
I usually do keep it on charge if I think I won't use it for a few days.

Having said all that, I moved the car a couple of times over the weekend and when I moved it just now it told me the battery was low and showed 10%! Yet it was on CTEK last night and showed fully charged this morning on CTEK.
Alternator took it up to 35% quite quickly and it's now on CTEK again. But I suspect I have a new issue.

Edited by davek_964 on Monday 2nd November 09:24

[650spider]

Mines stayed outside for almost all of my 19mths ownership and at no point on trickle charge.

Cannot remember ever seeing it less than 90% even after a 5 week stint sitting idle; it shows on startup the battery level.

I cancelled the vodaphone tracker upon purchase so unsure how much that helped, although will do exactly the same on the next one.

[12pack]

I use the car during weekends, and put it on trickle when done, so it stays pretty much at 100%, which is actually not great for Li battery longevity.

Keep in mind, just like in phones, for measurement accuracy the battery needs to have a full discharge and then top up to 100% occasionally which I expect hasn’t happened in your car. So I wouldn’t put too much stock in the reading per se, but probably need to trickle it if it goes below 50%.

[djangoW]

Thanks for replies, all make sense. I will monitor over a few weeks. I'm not phased (no pun intended) by the potential for needing either to trickle charge for extended periods of no use, or indeed even a new battery at some point in the years ahead. I've spoken to a friend who knows a lot about li-ion and these behaviours may be considered relatively normal. Getting the last 10-15% of charge takes much longer, 1000+ full charge/discharge cycles should be attainable and capacity will normally deteriorate by 1-2% compound annually, depending on use. Of course, the true test is at what point low battery levels cause non-start issues, and how frequent they become without trickle charging.

Apologies for being a "battery bore", but this topic may be relevant as there do seem to be a few Mac owners who have experienced unexpected challenges - and with the 650 lack of access hatch to battery / terminals it is much more of a potential pain.

Appreciate further views, especially from those with cars 4-5+ years or older, as replies may be helpful to potential purchasers also.

[davek_964]

Just took mine out for a run to charge it and battery level behaviour was curious.
Was about 40% when I left, and it went up to around 80% within about 30 mins - but was then very slow getting to 85%. I gave up in the end and stopped for petrol. Curiously, it showed 85% when I got out of the car and 96% when I got back in, which is normal level for mine.

I've left it off charge to see how it behaves over the next few days. I know it usually stays high but I still don't understand how it dropped to 10% today.

[justin220]

Any more than 3 or 4 days without use, I plug my 3 year old 540C in.

[djangoW]

justin220 said:

Any more than 3 or 4 days without use, I plug my 3 year old 540C in.

But why? Do you see levels fall if longer? Is it based on any bad experience?

[davek_964]

djangoW said:

justin220 said:

Any more than 3 or 4 days without use, I plug my 3 year old 540C in.

But why? Do you see levels fall if longer? Is it based on any bad experience?

I do the same.

For me, it's based on two things:

1) Car lives outside, so if battery does go flat it would lower the windows. This would be bad.
2) Battery is bloody expensive so I'd rather keep it maintained

As I mentioned earlier, apart from the blip yesterday (which I think I caused by repeatedly starting the car and moving it) my battery seems to drain very little over time.
But I'd like to keep it that way.

[12pack]

djangoW said:

But why? Do you see levels fall if longer? Is it based on any bad experience?

Why not, especially if it’s used occasionally.

With 4 BEVs in the family and 3 occasional use performance cars, we plug them all in in (except for the Atom which is not so easy).

[djangoW]

Update after 7-10 days
Car run regularly each 3-4 days
Battery level monitored each time
Level had consistently risen gradually and is now back up to 100%

Conclusions? Err..
Still no idea why dropped to 70% even tho used regularly
Still no idea why it "stopped" at 89% on a long journey
Happy it does now appear to have self recharged back to 100%
Bit suspect about accuracy of the measurement now, esp as level regularly appears higher on restart than when stopped.
Will continue to monitor and record.

Apols for boring everyone

PS petrol filler gap spontaneously self opened on firing up and then wouldnt shut until powered down. Also later spontaneously reopened stopping at station to refill. Lovely... car reafs minds... Its been fine since.
Quirks

[davek_964]

Mine has been exactly the same - it had a slightly odd few days where it dropped (probably my fault), and then didn't see to want to go back up on the charger - and a few days later, after a couple of runs was back to normal and has been since.

The good news is it means I don't need a new battery - but why it behaved that way in the first place is anybody's guess. Although I suppose if it hadn't got low enough to warn me, I wouldn't even have been aware.

[SSO]

I keep all of our cars on trickle chargers when they are not being used. Never had a battery issue with any of the Macs. Charge level is always in the 90% range even when they are out on multi-day road trips.