I'm pretty sure that your recommended method of 3X{ 12V reset then charge at idle} will leave the pack at ~50% SOC. On a parked HCH I one must push the RPM over 3K to force the pack to a SOC higher than that. Well, a stock HCH I anyways, one of retepsnikrep's Imac&c devices may allow it.

 

Good to know. Odd that it's different than both the Insight and HCH2.

 

Steve, I've read quite a few of your posts on this topic regarding both the HCH1 and HCH2 battery to try and get up to speed on the methodology.

Sorry if you've covered this before, but is there a reason not to use the LPC-100-500 instead of the LPC-100-350? My thinking is that this would get a bit closer to the 0.1C charge rate you mentioned there. Does the 350mA charge rate provide more of an opportunity for the cells to self balance without damage from heat?

Looking at the specs on the LPC-100-500, I see it can stay in the CC regime up to 200V, so it should be fine there.

 

The standard assumes discharging a smaller pack to 1V/cell. It wasn't intended to apply to 120-250 cell packs where 1V/cell has little meaning. Yes, I'm picking and choosing applicability, but for good reason (a lot of my work is with the 6 cell subpacks, where it is very applicable).


LPC-100-500 is generally okay for maintenance; however, for severely imbalanced packs, you may need to run them for the full 1.6X capacity input. This can severely overcharge the healthy cells.


I know of an Insight driver that uses one without issue, but he's already done a lot of work to his pack and has a good feel for its state. IIRC, 2X APC-35-350 are cheaper than 1 LPC-100-500.


Additionally, the 100-500 only works from 100-200V. If you're going deep discharge, you're going to be waiting for the voltage to recover as the voltage just pulses. The 28-100V APC-35-350 gives you an effective range of 56-200V.

 

Thanks for the quick reply. My pack luckily seems to be in fairly good condition, I'm just looking to keep it that way. I don't think I will be drawing it down below 1V per cell right now unless there's a very strong argument for doing so?

Am I correct in thinking there's not much to be inferred from the resting voltage of my individual sticks? After a reset and 80% indicated SOC on the car and letting the pack sit for ~6 hours, all sticks were at 8.15V +- 0.03V which would be 1.35V per cell. I'm glad to see they were not completely out of whack, but that's about all I can tell.

 

Resting voltage is only a confirmation of a problem, not necessarily a lack of one. A resting voltage of > 0.2V is an indication of a potential problem. Closer is better, but that's a decent guideline.


You can infer that you likely do not have a failed cell. Failed cells generally won't hold a charge for any significant period of time. You may have self-discharge and capacity issues.


If you haven't experienced a pack failure, then you're probably in decent shape. I would still encourage a lower current.


Remember that charging an HCH1 or HCH2 pack in-car requires a PWM fan controller to limit the fan speed or a 10A/12V power supply to run it at full speed. DO NOT attempt to charge with the pack installed without active cooling. You will cook the pack.

 

Pardon my ignorance but does the actual charger cost only 35 dollars?!?


Buy 3 DMM's, the discharge hardware and all the other bits and pieces.... this sounds like it only cost you about 85 bucks (if even that!)

What does the extra 400 dollars for the Maxxvolts or HA units get you?
(or the extra 150 for a generic ebay unit lol)

Auto shut off?
looks cleaner?
In car? (Steve explained around that it looks like)
Harder to kill yourself? (this is a real thing so... that would be worth some $$)

sheesh, I might copy your setup!

Also you took the pack down to 15 volts, isn't there a risk of flipping the weakest cells by going that low?

 

The minimum components necessary to make something work are cheap. You're buying safety, convenience, presentation and somebody else's time.

No, there is no risk of flipping the weakest cells. It's an absolute certainty. Probably half of the pack's cells are reversed at that level. Essentially anything below 1.1V/cell almost guarantees at least 1 reversed cell. This is part of the reason why a full charge is recommended to ensure that you're starting with ALL cells at 100% SoC.

Reversals have been discussed ad nauseam for years now. If cells are otherwise relatively healthy, reversals at low current do not measurably harm them.

 

Now that I think about it... it might actually be good for them as it would really cause any crystals to redissolve.

But I'll still do some more reading.

 

It's not the reversal that changes the phase at the terminals, it's the consumption of the voltage depressed capacity. Reversing it is essentially just a guarantee that you've consumed that capacity.

Energizer's guidelines on reversals of CONSUMER grade cells is that they can be reversed without harm at up to -50% capacity, i.e., if you have 6500mAh in a cell, you can discharge that and then run up to 3250mAh of capacity through it in the reversed condition before damage occurs.

Over on IC, Mike Dabrowski reverse charged cells at 2A until they read -1.8V and then cycled them at 15A discharges. The reversed cell performance was indistinguishable from the cells that were not reversed.