I have recently acquired 2 HCH1s with high miles. I purchased a grid charger and will soon be attempting to recondition the batteries. I have been doing a lot of reading on the site to get up to speed. I plan to build my own discharger and follow the discharging instructions on the HA website. I already have all of the parts needed except the connector but that is on the way.

My basic question is: What are the relative benefits and drawbacks of a 1-bulb vs. 2 bulb system?

I understand that a 2-bulb system should be wired in series and the same recommended wattage bulb should be used in each fixture. From my reading, I believe I know some of the answers to my question but I am looking for confirmation and anything I might have missed or gotten incorrect.

2 bulb system.
drawbacks:
A) needs more materials/$ to build (negligible since I already have it on hand)
B) if one bulb fails, you still have to replace it before you continue (same as single bulb)
C) ?
D) ?

Advantages:
E) Less likely to blow the bulbs (is this because the heat dissipation load is spread between 2 bulbs?)
F) ?
G) ?

Other questions:
1) Assuming the same wattage bulbs are used, would the discharge times decrease? (My current understanding is, no.)

2) How hard/expensive would it be to build your own automatic discharger? Since the commercially available units are more expensive than the chargers I'm assuming it would be more $, more components, greater complexity. But it also would seem that there is a greater opportunity for savings (plus,aWQ21 I like projects and learning through DIY). Lots of people have built their own grid chargers & manual dischargers but I haven't found examples/plans for homebuilt dischargers you don't have to babysit. (I'm an engineer and a very experienced ICE Civic mechanic and also have electric & electronics experience but I am not an electrical engineer. (i.e. I could build one from plans easily enough and could understand them with some basic explanations but wouldn't be able to design one myself without a lot of re-education.)

 

If you use single 120V rated bulbs, you will blow them because the pack voltage is significantly higher and will force the bulb to exceed its rated power.

Faster discharges aren't better. Discharge current below nominal voltage should be kept as low as practical.

1) Not sure of context. Bulbs are resistors. Two resistors in series will increase resistance, decrease current and increase discharge times.

2) Can be done. For me the task would take much longer than the inconvenience of doing it manually.

recommend 2 120V bulbs in series:
any wattage above 158V
100W max above 132V
40W max below 132V

Do not discharge below 106V

Recommend multimeter in 10A ammeter mode in series to measure current and another voltmeter on battery terminals. Log time, voltage, current at: 5s, 15s, 30s, 60s, 5m, 10m, 15m, 30m, 60m and every 30 minutes thereafter. With that data you can accurately approximate pack capacity.

Also worth logging all 11 tap voltages at: 158, 145, 132, 119 and 106V.

 

Thanks for the reply. Yeah I was only thinking of decreasing discharge time in the >158V range because I had read your statements from before that any wattage was fine in that range since it would still be less than the currents drawn while driving.
"1) Not sure of context. Bulbs are resistors. Two resistors in series will increase resistance, decrease current and increase discharge times."
I did some ohms law calculations after my initial post and figured that out. Sorry for the dumb question. It's been a while, my electrical knowledge is rusty.

OK, so it sounds like if there's value in recording tap voltages, etc. at various times then I'm babysitting anyway. So unless I'm going to build an auto-discharger that also logs all this data then I'm not getting what I need. That's a lot more complex. I see why it wouldn't really be worth it.

A) I have an inexpensive clamp-on ammeter. Any reason putting that on the positive lead from the battery to the discharger wouldn't give me good readings? (I will have another MM set up for voltage readings.)

B) You mentioned 11 tap voltages. HCH1 has 10 pairs of sticks. Am I missing something or were you thinking of HCH2?

C) How would you suggest measuring the tap voltages? I'm assuming you would stop the discharger at those points and backprobe the connector to get the readings, then turn the discharger back on and proceed. (I know you have to stop at a couple of those points to change bulbs anyway.)

 

I just thought of a related question. I mentioned in another thread that one of my HCH1s has been sitting for weeks while I have been rebuilding the trans. Now that I have a grid charger I want to charge it to a suitable level and keep it there until the car is put back together and being charged regularly by driving. If I am remembering correctly, being kept at 50%-80% of capacity is best.
The question: How do I know when I am there?
1) Is there a calculation that correlates voltage to % capacity?
2) Is it a simple ratio of peak voltage or something more complex?
3) Does it depend on the conditions or the results of my grid charging?
I am in SE Michigan and current temps are in the ~25-38*F range.
The car is not in the city where I reside and I only get to work on it on weekends?

 

Sorry. Not sure why I'm hung up on HCH2.

HCH1:

any wattage above 144V
100W max above 120V
40W max below 120V

A) if you have a clamp ammeter capable of DC, that's great.
B) derp. Yes. 10.
C) back probe the connectors during the discharge. It's important the readings are taken under load. practice taking readings quickly at other times to minimize the skew due to the time difference. Not looking for perfect. Looking for good enough.

Wait until you're ready to put the car back into service and give it a full grid charge with 10,400mAh of input.

1) not reliably. SoC depends on voltage, current and temperature. The car has a lookup table built into the BMS. I do not know the relationships.
2) See #1
3) See #1

Recommend you remove battery and take with you for testing given the time consuming nature of this type of work. If you can rig a box fan or carpet dryer to blow through the pack to the point that you can sense air flowing through, it's enough. Fan only necessary when charging.

 

Thanks for the clarification and suggestions, but I am confused by this:

1) Are you suggesting that it's better not to charge it until I am ready to put it back in service?

It has been sitting 2 months and is probably well below 50% SoC. I know that was a bad move and maybe I did some damage but now that I finally have a way to charge it without running it I thought it would be better to get it into the 50-80% range that is recommended.

2) If I should store it partially charged I still need to decide on a good level. I understand your answer about SoC vs % capacity but does your experience suggest a voltage range that would be best?

I've read that I shouldn't leave it deeply discharged and also shouldn't leave it at 100%.

3) Do I understand correctly that 144V would be considered 0% SoC, and 100% SoC would be in the neighborhood of 170V +/-?

I will take your suggestion and bring the battery back with me and I can do charge/discharge cycles to diagnose and recondition. But there will still likely be time while it is sitting & waiting to go back in the car. So I am still looking for the storage state that is least harmful to the battery.

One last question?

4) Should I start with a drain or a charge? Or does it depend on the voltages I get when I pull the battery today?

 

I assumed OEM cells. On OEM cells, there is no significant issue associated with long term storage. Healthy cells will retain charge for a long time. On older cells, they may self-discharge, but this does not harm the cells. It is beneficial in some ways as long-term self-discharge completely eliminates voltage depression and removes the need to discharge for capacity recovery.

If these are not OEM cells, it may be too late.

If OEM:

1) yes
2) Don't do anything with it until you're ready to return it to service.
3) No. 144V is nominal; however at REST, that voltage would indicate at or near 0% SoC. Under load, it would depend on current and temperature.
4) Prior to the first discharge, always charge with 10,400mAh input to insure all 120 cells are pushed to 100% SoC. Active cooling. Should pack air exit temp exceed 100°F, terminate charge. Should voltage peak and fall back >1V, terminate charge.

If not OEM, charge for two hours. Every 30 days, check tap voltages. If any fall below 14.8V, charge for 2 hours, repeat check every 30 days and charge as needed. Prior to return to service, charge for 10,400mAh input.

HCH1 OEM sticks are almost always yellow.

 

Thanks, that's great info. Got the pack out today and it's not as bad as I thought it might be.
Total voltage = 154.0

Tap voltages are:
15.40 15.40 15.38
15.38 15.41 15.40 |
15.36 15.45 15.38 15.40

as they would appear looking at the business end of the pack. I'm not sure if the sticks are original or not. The ones on the bottom rows (as it sits in the car) are bright orange. The ones on the top row appear a slightly different color (like a pale orange brown) but I think its because there is some sort of hazy semi-translucent material or sleeve over the orange material. Its hard to tell.

1) So based on this, the recommendation would be to leave it alone until I'm ready to put it back in service? (I will still check tap voltages every couple weeks if it goes that long.)

2) I can store it outside (~25-38*F), inside at ~45-50*F (for most of the week) or at my residence at ~63-68*F. Would one of those be best for the battery?

3) When it's time to go back in, I'll do a full soak charge as you suggested. Should I then do a discharge cycle logging data to assess it's capacity (and then recharge prior to installation) or just skip the discharge and see how it drives?

 

Healthy looking battery.

1) Yes.

2) Whatever is easiest.

3) Up to you.

 

Thanks. Got it.

I think I’m going to pull the battery from the other vehicle (also HCH1) today. It is not registered yet but I take it for a short drive each weekend I’m here to keep the batteries charged. It does a recal almost every time I drive it so I think the battery is in bad shape. I plan to evaluate both batteries and put the better one in the vehicle I plan to keep (04 MT).

You mentioned these points for logging tap voltages when you were thinking of the HCH2.
I did some calculations based on these and 120 vs. 132 cells and came up with the following for the HCH1:
Nominal Voltage = 120 x 1.2v = 144v
Minimum discharge voltage = 120 x .8v = 96v
4 equidistant points to log tap voltages between nominal and min (144-96)/4 = 12v interval
Log tap voltages at 144, 132, 120, 108, 96

1) Is that what you would recommend?

Discharging setup would be 2-120v rated bulbs in series:
>144v - 2 @100W+ bulbs
144-120v - 2@100W bulbs
<120v - 2 @ 40W bulbs

2) Did I get all that right?

You mentioned spec as 10,400mAh. I am unsure how to determine charging instructions based on total input.

3) Would the standard grid charger instructions give me the desired input?

My understanding would be:

- If deep discharge was done, start charge immediately after discharge.
- (optional) Charge in car at idle until stops charging, disconnect/reconnect battery to reset ECU, repeat (3x total)
- Connect to grid charger with active cooling (in car or out)
- When voltage stops rising, charge for an additional 3-5 hours, not to exceed 24 hours total.
- If at any point voltage goes down >1v(?), terminate charge.
- Monitor internal pack temp if possible, if temp exceeds XX(?) terminate charge/increase cooling.

4) I’m not sure about those last two points because I can’t find the posts where I read them. Please correct/fill in the missing info.


I apologize for all of the handholding and questions I know you have addressed elsewhere. I’m just trying to get all of the info in one place so I can use it as a reference. I was thinking that, once done, we could rework this and get rid of all the info that would not be relevant to others and turn it into a guide or a sticky (do they have those on this forum?) I would be willing to compile and organize it and then give it to you to post (since it’s all your knowledge anyway.) If it was good, you would ultimately be able to spend less time answering repetitive questions from newbs like me. You could also alter the relevant figures and easily create similar guides for other vehicles or generations. Let me know what you think.