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Discussion Starter · #1 ·
The poor man's grid charger:

Take the car out of the garage and rev it up to 4,000 RPM until it starts to charge, hold 4,000 RPM until it is charged and then let it idle for 40 minutes. It will do a slow background charge while it idles and that will top balance the cells, just like a grid charger.

Credit to Frankie for sharing this method, mudder confirmed that it is in the service manual.
 

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Although I think 'on-demand' charging using the ICE similar to this is way under-appreciated, or just not known, there's a few things about this description that don't quite ring true...

The poor man's grid charger:
Even under the best circumstances - the conditions under which the description is closest to right - I don't think what you get is comparable to grid charging. Grid charging is typically only about 350mA, whereas the lowest background charging off ICE that I've seen was something like 1.2A. And to get that, the IMA has to be in a particular 'maintenance mode', like after a neg recal and normal background charging/forced charging can't charge at least ~30% of nominal capacity without a tap voltage 'peaking' or hitting a high threshold, I think. It's a bit mysterious, I used to see that ages ago with bad packs, I'm not exactly sure when/why it does that versus when it simply just stops charging...

And then, even in this mode, I'm pretty sure the IMA stops charging at a level that's still not officially 'overcharging', which is usually the way people around here describe what a grid charge does. Basically, I think the IMA will allow some extra charging, with slightly tweaked termination parameters, but it won't, say, charge more than 100%, i.e. if the BCM has recorded a cumulative net input of 6500mAh pretty sure it won't go over that.

So, not really comparable to a grid charge. Not that that's a bad thing in itself...

Take the car out of the garage and rev it up to 4,000 RPM until it starts to charge, hold 4,000 RPM until it is charged and then let it idle for 40 minutes. It will do a slow background charge while it idles and that will top balance the cells, just like a grid charger.
You can do a 'rev-charge' similar to this any time you want. But, the only time it will charge at idle is when the IMA is in a maintenance mode, like if you've turned the pack OFF, or after a neg recal (pack empty), etc. And you don't need to rev to 4000 to invoke it.

Revving to 4000: you only need to rev a little beyond 3000 to invoke rev-charging. The current rate at just above 3000 RPM is about 7 amps; the current rate at 4000 RPM is something like 20-30 amps! I charge my pack like this sometimes, at high current. I'm not sure how well your typical cruddy, somewhat dysfunctional pack/cells would handle it. It's worth trying, but I'd be watching pack temps, personally. Even at such high rates I don't see a ton of heating; with cruddy cells you'd be able to see temp increasing by the minute...

Like I mentioned in that other thread some days ago, you do get a balancing effect at higher charge states, not necessarily only at chock-full. More charged cells charge less/slower than less charged cells. I'm not sure if this depends on actual charge state or not, or whether the NiMH 'vario-stoichiometry' allows it to happen virtually anywhere in the absolute charge state range. You can have cells that are charged say only 10-20% but they'll still have high voltages, makes me wonder if what matters for this balancing effect is high voltage and not necessarily high charged in the amp-hour capacity sense (i.e. where 100% equals 6500mAh, where high charge might be say above 65%)...

Lots of mysteries, still...
 

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^ It does - merit discussion. Or at least every Insight owner should know they can charge their pack any time they want, simply by revving above 3000RPM (at light throttle)... I sometimes drive in 2nd gear for extended lengths just to charge the pack quickly - it takes only minutes if you're up around 4000 (20-30 amps will do that).
 

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I gave it a thumbs up because it is on the right path as far as thinking goes. I don't have a grid charger in my car. I have once used the "keep resetting the IMA and idling until only a few minutes is needed to reach full charge" method once. But I eventually pulled that pack for conditioning.

I am currently on the road collecting data and hope to share some insights on how a long road trip is a great poor man's battery conditioner, if the data supports it (I believe it will.) I believe I am watching my car doing "grid charging" aka top balancing as I drive!!!
 

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What you wrote is Honda's official recommendation for charging the IMA pack... it's in several service bulletins. It's not an ideal method, though, as it was more meant to recharge the pack after the car had been sitting on the lot for a long time (because nobody wanted them).

However, I must point out that you can build your own grid charger for under $50. Just connect this bad boy up to your IMA battery with a proper inline fuse and a reverse blocking diode (to prevent discharge when the car is off), then add a power cord. Next, connect your IMA fan to a 12 volt supply, which you can wire into the same power cord. Now you can just tuck this whole contraption into your IMA bay and then plug in the power cord whenever you want to grid charge.
 

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vote 4 mawah
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What you wrote is Honda's official recommendation for charging the IMA pack... it's in several service bulletins. It's not an ideal method, though, as it was more meant to recharge the pack after the car had been sitting on the lot for a long time (because nobody wanted them).
It's also in the Service Manual, at least for the 2006 HCH2. Dealers were recommended that method, every 30 days for honda hybrid cars on their lots.
For a new pack it is an OK way to check the packs (SoC), and since the ECU's were still factory fresh, little variation in IMA behavior to deal with, either.

However, I must point out that you can build your own grid charger for under $50. Just connect this bad boy up to your IMA battery with a proper inline fuse and a reverse blocking diode (to prevent discharge when the car is off), then add a power cord. Next, connect your IMA fan to a 12 volt supply, which you can wire into the same power cord. Now you can just tuck this whole contraption into your IMA bay and then plug in the power cord whenever you want to grid charge.
Thanks for the writeup and links.
Now, if there were only a solution for self discharge and (cell / stick level) heath differences seen in older packs, we'd all be set.

@Recovering_Gasaholic - here's a link to one of Eli s' polls about the effects of how Honda programmed regen charging - asking will the pack self balance and if so how long will it take.
Can the car recover from artificial imbalance?
 

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I'm not convinced.

Honda has only ever referenced running the engine at 3,000 RPM; Not 4,000.

I know I've read service bulletins from Honda that recommended resetting the computers and then rev charging (hold the engine at 3,000 rpm) the battery until the gauge read full.

I don't recall reading a recommendation to then leave the engine to idle for an extended period of time. If anything, this will slowly discharge the HV battery a bit.

Also, this isn't grid charging.....
 

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Discussion Starter · #12 ·
I don't recall reading a recommendation to then leave the engine to idle for an extended period of time. If anything, this will slowly discharge the HV battery a bit.

Also, this isn't grid charging.....
Well it would be easy enough for somebody with the 0DB II C&C to check for a small background charge when doing this procedure.
 

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Well it would be easy enough for somebody with the 0DB II C&C to check for a small background charge when doing this procedure.
Like I mentioned earlier, the charge at idle only happens under specific 'maintenance mode' circumstances, like after the pack has been turned off or drained to effectively empty.

Also, fyi, you can always check for a 'background charge', charging off the ICE, if you go light on the throttle and bring RPM above 3000. If there's a background charge you'll see 4 green CHRG bars.
 

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Now, if there were only a solution for self discharge and (cell / stick level) heath differences seen in older packs, we'd all be set.
There's a pretty fool proof way to identify which tap has the lowest/least charged cell, which is also likely to be the fastest self-discharge tap/cell (1). And as far as I can tell, you can avoid problems caused by uneven self discharge if you usually run the pack to empty at the ends of your drives. It doesn't fix self discharge, you simply 'do management' that prevents uneven self discharge from becoming a debilitating problem...

(1) Drive, use assist until close to neg recal, pull into garage with headlights ON, let car go into autostop, turn headlights OFF, measure tap voltages immediately, time 1, and then either some minutes later or when you see the BAT gauge plummet (i.e at empty/neg recal), time 2. Calculate the change in tap voltages, time 2 minus time 1. The tap with the least charged cell will likely have the largest voltage drop between time 1 and 2. This is the tap that's causing the pack to be seen as empty. Usually that's the one causing problems, like a P1449-78, and prevents the pack from charging higher (or from discharging lower)...
 

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Well it would be easy enough for somebody with the 0DB II C&C to check for a small background charge when doing this procedure.
I have already done this. Once above roughly 30% SoC, the car does not charge the HV battery at idle.

In your opening senario, leaving the engine to idle for 40 minutes will do nothing except burn more gasoline.
 

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Well I know there can be a background charge without it showing charging bars.
Not sure what you're suggesting... What you say, that's right: a 'background charge' typically/often doesn't show charge bars, that's why it's called a "background charge," it's happening and most of the time there's no visual indicator. But even so, you can go light on the throttle and bring engine speed above 3000 RPM, and then you will see 4 green charge bars - the background charge is no longer in the background...

With some 'background charging' you actually do see the bars regardless, not really sure what the criteria are. If you drain the pack until empty, you'll get a 'forced charge' or 'mandatory charge' and you do see the bars, at least until it charges to something like a nominal 55%. I think in general there must be some 'dude, pack really low' ICE charging, and you see the bars, and some 'dude, we're just getting the pack charged a bit more' background charging. As much as I've watched over the years, I've never been able to nail down specific criteria.

Here's a link to a thread that explores the topic: Ideas, facts, wild-*** guesses about background charge?
 

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I'm not convinced.

Honda has only ever referenced running the engine at 3,000 RPM; Not 4,000.
I think there are some variables. But 3k rpm to start forced charge sounds about right to me, at least in most circumstances I've run into.
I haven't used a forced charge in years, but I do remember seeing some odd stuff showing up at times, when expecting something to happen like it did before, than something else happens.🍵
Also, this isn't grid charging.....
I think most here would agree with that statement. Poor is the key word. Don't know how grid charger got into the sentence, though.
 
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