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Discussion Starter · #1 ·
Hi everyone, I recently bought my first Insigh about 2 weeks ago and have been slowly hammering it back into shape (the inside was a total wreck!). Even so it is the funnest car I have ever driven!

One problem my car has is that it has been sitting for 2+ years without being used, according to what I have read on these amazing forums (big reason I bought the car actually...keep up the good work) is that the battery pack can become super unbalanced after sitting for so long and should be grid charged to prevent damage. So I have 3 questions.

1. Since the car sat for so long is it possible it is already balanced due to all the batteries essentially discharging (grid discharging :p )?

2. Does it damage the batteries if I drive with them unbalanced or does it just reduce the performance reversibly.

3. I am considering building a grid charger from scratch very similar to the early designs that Mike had posted in the sticky which in essence was 3, 48 volt supplies, 1, 24 volt supply, and another 12 volt supply (for the fan). Then connecting the supplies together to generate 168 Volts (with one of the supplies being current limited).

I am thinking about using boost converters such as these powered off of a 12 volt computer power supply: DC DC Converter Boost Step Up 8 5 48V to 12 50V LED Driver Power Supply Module | eBay

Is there any technical problem with this design?

An alternate design I was considering was to do the same thing but with isolated wall warts I am planning on purchasing at my local thrift shop. Essentially connecting together a bunch of wall warts (with 1 current regulated supply).

Is there any technical problem with this design?

I look forward to your answers and to joining your wonderful community! Lets keep these cars running forever!

-Trezitorul
 

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1. Since the car sat for so long is it possible it is already balanced due to all the batteries essentially discharging (grid discharging)?
Possible, yes. I had 10 sticks sitting in the garage for a year and a half, and all of them were completely discharged, i.e. balanced in the sense that they were all discharged. On the other hand, I had a pack sitting in the garage for the last 6+ months, and the few cells I've discharged to-date, I pulled about 3000mAh out of them...

2. Does it damage the batteries if I drive with them unbalanced or does it just reduce the performance reversibly.
Your IMA system would probably be disabled, with a light and code, with a pack that sat 2 years. If such were the case, no, no damage - cuz they aren't in play. If there's no lights or codes and the IMA system appears to be enabled, I personally would not drive on the pack until I did a full charge, perhaps full charge, a discharge, and another full charge... Even so, I don't think you'd cause any damage - because the car would disable the system before any damage (ok, major damage) were to happen... You can also pull a couple connectors on the BCM and turn off the pack switch and drive gas-only until you get your pack squared away...
 

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Your IMA system would probably be disabled, with a light and code, with a pack that sat 2 years. If such were the case, no, no damage - cuz they aren't in play. If there's no lights or codes and the IMA system appears to be enabled, I personally would not drive on the pack until I did a full charge, perhaps full charge, a discharge, and another full charge... Even so, I don't think you'd cause any damage - because the car would disable the system before any damage (ok, major damage) were to happen... You can also pull a couple connectors on the BCM and turn off the pack switch and drive gas-only until you get your pack squared away...
Conventional wisdom around here used to be that if you drove a car that had been sitting a long time the battery would fail in about 8 months. IIRC, this was pretty well documented. Is this no longer the case?

Sam
 

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Discussion Starter · #5 · (Edited)
Wow that was fast!

Thanks for the heads up on the boost converters sharing power supplies issue. I will not go that route. So on to design 2, using a bunch of wall warts from the thrift shop. Any ideas if that plan would have any issues (other than being ghetto)?

Regarding the battery state I hope to grid charge within the next 2 weeks without putting any serious mileage on it (<100). I think this should be OK since the battery will not be significantly stressed? The IMA system has been working although it has been a bit spotty due to a ground strap being totally missing (throwing temp sensor codes). (I will replace that asap).

Thanks for the help!

-Trezitorul
 

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i used two of the little led drivers that peter found on amazon. i bot a apir for $19 on ebay and got a $5 credit voucher from the seller at his online store (dragonmart) so i bot a second set for $15. the diode cost about $.14 and the extension cord i used for the power to the led drivers and the other end i used for manual discharge was free so my second entire grid charger/discharger cost $15.14. i wish i could post up pictures but the website will not let me post pictures anymore for some reason. kinda annoying when i see others posting up 7megapixel pictures and i can only post up a few tiny VGA 150k images. it is really annoying to be denied the ability to illustrate what i did.
 

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On grid chargers, there's a few Meanwell LED drivers that have the right current output and the right voltage range so all you'd need is a single one of those drivers. I think the cost range is something like $25-$60 depending on whether you go for the adjustable current, heavier duty ones (ex. HLG-60H-C350A) or the non-adjustable, lighter duty ones (ex. LPC-100-350, 500, or perhaps LPC-150-xxx). Not sure why more people haven't been turned-on to these options... Perhaps it's because even the original Mike D. 'dumb charger' wasn't so dumb, in the sense that you were able to adjust the output voltage and by doing so prevent charging above whatever voltage you determine your pack to be fully charged. With LED drivers with just the generally correct voltage range, you have to monitor, time, turn it off manually, etc., which is something I've always done anyway...

I have a grid charger made out of two of the 'Amazon Gino' LED drivers, the first ones Peter suggested a long time ago, but it only puts out about 225mA now, though it's supposed to be 300mA... I've been thinking even 350mA might be too low, so I might buy one of these single LED drivers at a slightly higher current output, maybe 500mA...

Conventional wisdom around here used to be that if you drove a car that had been sitting a long time the battery would fail in about 8 months. IIRC, this was pretty well documented. Is this no longer the case?
Sounds like some IC wisdom from the Dark Ages. I can imagine that if you let your pack sit for a long time and then drive with it like that it would seem to "fail" eventually if not immediately - probably way out of balance plus self-discharged to low yet still functional capacity. But that's just imbalance, maybe some voltage depression mixed in, and low capacity, nothing a deep discharge and solid grid charge shouldn't take care of... The 'only' risk I see - and it's not one I'd take simply because you don't have to - is that if your cells are really imbalanced then there's a good chance individual cells are slipping through the cracks - getting overcharged and undercharged within that narrow window where the whole pack is actually working. Since the car only monitors the voltage for every 12 cells, a cell or two or more might be very low or very high relative to the median or mean voltage for the 12. On discharge, that one or few cells might be drawn down quite low, lower than the rest, and on charge, the one or more high cells might be overcharged... Something like that. I'm not positive how it all comes together. But overall, I think the car probably does a pretty good job shutting things down when things get too whacky, so there's little risk of say, reversing a cell at 50A for a long time, or little risk of having a completely full cell that's getting charged at say 50A...

Anyway, based on what I've seen with some really old cells that were driven plenty under whacky conditions, there doesn't seem to be much you can do with the stock BMS that will truly wreck cells - or even seriously damage them... But like I said, why take chances when you can just discharge and charge and get the cells as balanced as they can possibly be given their age, use, etc?.
 

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what 'stock BMS' are you talking about?

there should be no need to select the final voltage for the top balancing charger. that will be dependent on the charging current and internal resistance of the cell during the final portion of the charge itself.

the grid charging is done to bring all of the self discharged cells up to the same final voltage that the cells with the lowest internal resistance to charging have already reached.

if you do this at a low rate then there should be less internal heating during overcharge of the full cells. i find that the led driver current is dependent on the battery pack voltage and decreases as the pack voltage climbs to 176V. it drops from 294mA at 160V down to about 270mA at 174V but that is still enuff to overcharge the cells that have already received full charge.

it is then just a matter of how long do you overcharge at the lower rate than the 500mA to force the cells with high internal resistance to charging to accept the charge. that has not been analyzed from what i have read here and over on mikey's blog.

i was not able to detect any heating of the sticks when i over charged them at 300mA. has anyone else been able to determine how much warmer they get and why it is that i cannot feel it with my hand in contact with the sticks?
 
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