The idea behind grid charge is hold peak voltage for 5-8 hours NTE 24hr total. Since you don't know when the pack peaked, I'd go for the 24hr option.

The drop to 177V seems excessive. I'll see about 10V drop over 24 hours, but my packs peak around 192-193V, and I don't check them for 24 hours, so that 10V might happen within the first several hours, and I don't know it.

Was the car charging period very brief - less than 2 minutes?

I count 17 hours total grid charge. I'd go for 7 more provided you haven't actually driven the car.

The idea is to ensure you input 100% SoC. 350mA for 24 hours = 8400mAh, which is 1.5X the rated capacity and compensates for charging inefficiencies. The 24 hour guideline was established for Insight/HCH1 with their 6500mAh capacities. Since the HCH2 cells are lower rated, you could go as little as 21 hours, but I like to keep it at 24 for simplicity since I occasionally work on both.

Nice work. I like the container.

 

My old computer p/supply shell earmarked for the purpose turned out too cramped so, I raided my wife's stash of freezer boxes
It's roomy and plastic thus easy to work with.

Car charging took longer than 2 but no more than 5 mins. and I only did it once.
Haven't driven it today so, will let it charge overnight as you suggested just to make sure it's full.

Many thanks!

Art

 

Art,

I built something similar out of a computer PS w/Fan, but it was amazingly cramped, and I had to fabricate some sheet metal brackets... very time consuming, and my stubbornness about protective equipment, meant I finished the project with a few sheet metal cuts.

I used one of the displays similar to Hybrid Automotive, but in 0.00A resolution instead of 000mA and no tenths on voltage. No temp monitoring either. Took a LONG time to put together. Was pleased with it in the end, but not worth the effort compared to my crude phenolic board with no display

Excellence in simplicity! Nice work.

Steve

 

Agree on simplicity being the key, but it comes with confidence.
Mine was intended to be self contained and safe to use in the hands of someone less competent than me. (If I upgrade the car, though with our daugter at university, it won't be soon )

Now for the results of overnight "top-up".
Started at 10pm at 177.44V (quite a drop from 181V at 3pm!),
at 11pm it was on 183.70V, then at midnight on 187.29V with temp. readings between 18-19 deg. I switched charging off at 7am on 186.75V and temp. at 25 deg. just kept the fan running till 8.45.
By then voltage dropped to 185, SOC reset took about 2 mins. and I watched the voltage climb to 188V max.

Interesting facts, your batteries appear to peak at higher voltage and don't self discharge at quickly.

Art

 

Without measuring self-discharge directly, it's not reliable to draw conclusions based on voltage drops. NiMH voltage at rest is a VERY POOR indicator of state of charge because the range is so tight and can vary from cell to cell.

I noted your labels indicated connection for discharge, do you intend to go that route now?

I would recommend it.

Steve

 

Well spotted, the charger is discharge ready though still needs to be built.
The meters and gauges should still work to make the process easier.
Yes, I will definitely attempt it in the spring and thanks for your detailed description of the procedure!

 

How goes the grid charger efforts?

 

Hi Steve,
It's been a while... good to hear from you!
Well, I performed a "soak" charge in December just before our Christmas/New Year ski trip to Austria.
Notices the battery fluctuations were virtually eliminated.
I am glad to say it's still the case, though the battery dropped to two bars on my trip to the airport last night. It is very rare event, most of the time in town the batery remains at 6-7 bars.
I haven't forgotten about performing a dischrge, just waiting for the weather to get warmer and stable.
How are things with you?
Art

 

2 bars = recalibration. It's time for another grid charge at a minimum.

Weather is only relevant to the human component. For the currents prescribed for grid charging and bulb discharging, anything above freezing is fine.

I have become much more conservative on my deep discharges. I recommend up to 200W when discharging above 158V; however, once you hit 158V, pause discharge, swap out for 25W bulb and continue discharge to 66V.

Steve

 

re: weather, yes, I know, in fact the colder the better.
As for the discharge, I will certainly follow your recommendation.
Trouble is, due to Europe wide legislation, it's virtually impossible to purchase any incandescent bulb above 40W. The idea is energy saving bulbs are to replace higher wattage light sourves.
I will need to find some on eBay perhaps?
Wil have a look.