Hi all,
I've seen something strange yesterday.
I drove the V gently empty to the red light, yesterday, and then plugged in with half an hour delay, the bike was at 24 or 26°C. ambient temps were around 30, but the V was standing in the shadow.
I didn't look while it was charging, but when I heard it end, I went for a quick look. 146V, 36°C. that is not common for my bike. I'd expect it to end at about 144V, 28-30°C.
I wouldn't mind it too much, even when the temperature rose to 40° later on..
But this morning, temperature was still at 30° and voltage dropped to 138 (expected 142 - 143!)
All bars were full when I drove off, felt normal, but voltage went down to 132v after 10 kms..
opinions?
When charging at 30°C ambient temp. 36°C batterytemp is not that uncommon to me. I can´t sa that the V´s NiMH react in that way, but I read a revision from a batterypack manufactuer, who testet his packs charging at high temperatures. He came to the conclusion that the charge was lost quicker at higher temps AND that the batterypacks
did´t accept the full charge at high temperatures. I´m sorry I have not saved the article.
Greetings Mike
146V is fully charged.
The raised temperature meant it was overcharged significantly (not the end of the world with nimh)
self discharge increases the further above 22 deg C you go.
it also increases the higher the state of charge (SOC).
the self discharge is pretty stable until you reach between 60 and 80% SOC (temperature dependant), past which it increases exponentially.
by the time you have left the bike overnight, it will have self discharged to around 80% SOC.
by 24 hours it would be around 70%SOC.
generally it is better to only charge to around 70-80% SOC unless you were planning on using the capacity immediately (theres no easy way to do this with a Vectrix), otherwise the extra charge will just be wasted as heat.
so everything is normal, just be aware that your last 5 or 6 bars won't exist, unless you go for a ride immediately after a charge where the voltage rose above ~145V.
Matt
Daily Ride:
2007 Vectrix, modified with 42 x Thundersky 60Ah in July 2010. Done 194'000km
Hey Matt,
Sounds plausible..
did another cycle since then, and charged again last night, and all seems ok, no more high temperatures (last charge finished at 26°C).
must have been the overcharge + 30°C ambient together.
I know it would be better to cut off the charge when at 80% SOC, but as you say: there's no easy way.
I guess I'll just pull out of the Nimh pack what it can give me (after 11000km I only saw the "charge ending voltage" drop a bit - still good range), and if it dies (after bridging several cells :-)) I know there's a better solution waiting :)
I'm just praying the rest of the bike keeps up.
Turok
"doing nothin = doing nothing wrong" is invalid when the subject is environment
In my opinion, you shouldn't perform a full recharge at 30°C ambient temp. You've already realised that it is not healthy for your v's battery. ;-)