The IMA system already does this, at both the top and bottom ends. It moderates voltage (or throttles current) so you don't go above 180 volts at the top and 125 volts at the bottom....
FYI, like all things IMA-related, this might not be as cut and dried as I make it out to be. This evening I was doing some longer duration assists, with a somewhat cold battery (~44F), and I was seeing pack voltage as low as 119, 120V (Bvo on OBDIIC&C) and holding steady there. I generally don't hold (relatively) higher amperage assists for very long, so perhaps I just don't observe every circumstance enough times to really know the bottom end. Normally it will drop below 125V but quickly moderate back up to at least 125V. This time it wasn't doing that. Perhaps it's because the battery was colder than usual and battery temp plays a part in the car's decision making?.
Battery temperature has a profound impact on the car's decision making.
The car will only pull full assist(80A+) if the battery is room temp or warmer. Anything below about 74 degrees and things are progressively notched down.
This is why you don't see many battery failures in the winter. It's also why you aren't seeing the dips well below 120V that you were seeing before the cold temps.
__________________
Bumblebee Batteries, LLC - Helping your hybrid get from point A to point Bee!
95 amps?!?!? Wow. Suddenly I feel less safe in my car. Better avoid water. (Or maybe go climb a mountain, drain the batteries to empty, and then install the clutch switch to disable the battery.)
Pure water, if there is any left on the planet, is an insulator. Dirty or salter water is a much better conductor. If you got a water induced short, it wouldn't be through the seat or plastic steering wheel so you're safe.
Battery temperature has a profound impact on the car's decision making.
The car will only pull full assist(80A+) if the battery is room temp or warmer. Anything below about 74 degrees and things are progressively notched down.
That's the reason I faked the batery temp in my lithium conversions to around 25-30C so you could get full assist at all time.
__________________
OBDIIC&C $50 inc software, pcb, switch and obdii plug.
IMAC&C HCH1 $50 inc software and pcb.
This is why you don't see many battery failures in the winter. It's also why you aren't seeing the dips well below 120V that you were seeing before the cold temps.
Yes and No, if you live in region where temperatures drop below 0C and the pack cold soaks, this can trigger some more nasty IMA codes on weak packs.
As temperature drops, the internal resistance increases. For old cells with high resistance already, this magnifies it and can contribute to throwing the light even if the pack would function reasonably fine in moderate temperatures.
__________________
2001 Honda Insight CVT - 210k+ miles on the odometer
Yes and No, if you live in region where temperatures drop below 0C and the pack cold soaks, this can trigger some more nasty IMA codes on weak packs.
As temperature drops, the internal resistance increases. For old cells with high resistance already, this magnifies it and can contribute to throwing the light even if the pack would function reasonably fine in moderate temperatures.
Good point. As usual, "it's complicated".
Insight #2 recently threw an IMA light. So it's definitely not impossible to get a winter IMA light, but they do seem to decrease fairly significantly.
__________________
Bumblebee Batteries, LLC - Helping your hybrid get from point A to point Bee!
FYI, like all things IMA-related, this might not be as cut and dried as I make it out to be....Normally it will drop below 125V but quickly moderate back up to at least 125V. This time it wasn't doing that. Perhaps it's because the battery was colder than usual and battery temp plays a part in the car's decision making?.
I should have written/asked whether 'in this particular case battery temp is playing a role in the car's decision making'?, i.e. Did the battery drop below 125V and stay there because the battery was colder than usual? I know that battery temps play a part in the car's decision making, in general...
Another thing that occurred to me is that I recently did my first grid charge (on a pack that had the sticks individually cycled some 10k miles ago). Maybe the grid charge did help, maybe it brought up some low cells and the pack V can now drop lower... Maybe prior to the grid charge a few troubled cells would drop out at an overall higher pack voltage and that would cause the IMA to throttle back current? Now perhaps the cells have been brought back to life, or at least boosted some, and the whole pack voltage is allowed to drop a little lower?
Earlier we were talking about re-programming or bypass device/methods that might trick the car into exploiting a weak battery more fully. I said it was probably '"fruitless," that the car 'probably already does a good job getting the most from a weak battery'. Now, I'm not so sure.
I've been trying to explore the lower limits of my pack a little more, and I wonder whether the negative recal threshold/s, trigger/s, or what have you might be geared more for the newer or normal pack, rather than the weak pack, and as a result negative recals occur earlier than they need to. If whatever triggers negative recals could be manipulated, could we get more from an old weak pack?
One might think that a pack voltage lower limit of about 120-125 volts tries to keep the pack above 1 volt per cell on average, the typical cut off for depleted NiMh cells. Yet, I wonder, do older cells develop a lower cutoff voltage, below say 1 volt, where the whole pack might be below 120 volts and still function good enough - if only the car would let it? Or another way to look at it, perhaps older weak packs have more voltage sag under typical loads, like instead of holding around 130-140 volts under a 40 amp discharge, it might be 115 to 125 volts, yet since the negative recal trigger is at say 120-125 volts, the car pulls the plug. What might be good for a normal pack, maybe doesn't quite apply to an old weak pack?...
Does the negative recal try to prevent cell reversal? What other damage might occur to cells pulling voltage down below 1 volt or 0.9 volt?
Anyway, I'm not so sure the car is able to get the most out of a weak pack... It seems to me that the average pack voltage for a weak pack gravitates toward a lower number than a good pack, yet perhaps the lower bound doesn't change; if it could you might be able to get more juice out of the pack...
FWIW YABO are sending me some of there sticks for testing.
I can test very accurately upto 60A discharge on a stick or single cell.
And a bit less accurately upto 120A on a stick.
Won't be any testing until new year sometime though.
Quote:
Originally Posted by retepsnikrep
My Yabo sticks have arrived for testing.
At a cursory external examination they look identical to the BB battery sticks with similar stickers, heatshrink, stick assembly etc.
How'd they test? The suspense is killing me!
Did they come with the heatshrink already in place, or are you expected to shrink 'em in place after affixing recycled PTC strips? Based on this message, I'd expect the later.
The AutoGuide.com network consists of the largest network of enthusiast-owned enthusiast-operated automotive communities.
AutoGuide.com provides the latest car reviews, auto show coverage, new car prices, and automotive news. The AutoGuide network operates more than 100 automotive forums where our users consult peers for shopping information and advice, and share opinions as a community.
It's also why you aren't seeing the dips well below 120V that you were seeing before the cold temps.
