Truck #1 (Nicad)

So after the last deep discharge of the nicad pack a month ago, the pack has been very soft lately. The voltage drops quickly long before I get to work. It is winter, but tonight I found out something new. I pulled the lid off of the pack and was wondering if the 24 redtops were way over charged compared to the rest of the pack, due to their higher capacity. This would allow the pack voltage to rise quickly and not fully charge the rest of the pack. So much for that theory. I took my discharge equipment and applied a 55 amp load for 12 minutes. That discharge took out exactly 11ah out of those 24 redtops. When they were almost finished, I checked them with a DVM only to find that many of them were nearly at zero volts! No good. So I put the constant current power supply on that group of redtops at 10 amps for 3 hours. So they took on 30ah worth of charge. Some cells were venting liquid which means they were over filled. I had refilled them a while ago, not knowing they were actually low on charge, which makes them low on fluid as well. Hmmm. So I’ll look forward to a stiff pack tomorrow morning on the way to work.

This past Tuesday the truck got another deep discharge on the nicad pack. The range was low, but it had also been cold lately. The pack went from -4kwh to +5.3kwh or -17ah to +29ah. This is encouraging. On the 5.7 mile drive to work, the pack voltage never went below 310 volts. This is also a good sign.

I’ve also been working hard on an analog Lithium BMS for 160ah cells. Later, it will be adapted to 40-90ah cells. The board has been iterated a couple of times. Each time better ideas were added for the layout. This last version needs to be built yet as it had some serious changes. The first version is built on a breadboard and works fine.

This deep discharge should be done at least one more time. The nicad manual states that sometimes up to 3 deep cycles are required to completely erase any memory issues. I will check the entire pack for water levels this weekend. A spot check showed that most levels are ok, but were checked while the pack was fully discharged. It has to be checked when fully charged.

This past weekend I jacked the #1 truck up to determine if I could get another water tight connector mounted into the front of the battery box. It looks like my only option is to remove the 1/2″ connector that is there for the Emeter cable and install a larger one. This would still be a tight fit to install. I may consider just adding lithium to the #2 truck, but it does not have a good pack in it yet. I have seen other trucks with a hole drilled and filled with silicone. Not an appealing solution.

Tom and his son bought the spare USE S10 battery box from me some time ago and installed it in their ’84 S10. At Saturday’s SJEAA meeting, I asked for input on how to get a BMS data cable into the #1 trucks’ battery box while keeping it water tight. Tom knew the answer because he knew the battery box better than I did. By removing the drive shaft, the wall of the box that holds the watertight connectors, is exposed clearly from under the truck. That way I can see if how hard it would be to drill a hole and add another watertight connector. The hole would need to be something like 5/8″ to 3/4″ in diameter. Someone talked me into using the water tight connectors that don’t need a threaded hole to be mounted. That translates into less work in a tight space under the truck. Thanks Tom!

Last night I took a drive on the highway. It was obvious the nicad pack was doing much better. So I drove at about 72mph which is the max the truck will go. Same thing driving back. About 11.7 miles round trip and the pack was above 300v 98% of the time. I burned over 4kwr and there was probably 1-2 kwh left. I’ll do a range test to see how much the capacity improvement really is.

On the way to work this morning the pack was over 315v the whole drive.

I will do the discharge maintenance again just to ring out any extra capacity that is held back by the memory effect. The manual says sometimes up to 3 complete discharges are required to restore the pack from deep memory effect.

The pack was down -5.2kwh. It charged to +6.3kwh. The truck took on 11.5kwh as of this morning. So it recharged with more than 100% overcharge. The pack voltage on the way to work this morning was significantly higher. It stayed in the 315-320v range while driving. This is about 15 volts higher than before the discharge maintenance. I won’t recharge at work to see how well the pack voltage holds up on the way home. At some point I’ll have to do a load test to see how many kwh’s the pack is good for now. It is possible that the deep cycling of the pack may need to happen once or twice more.

All of this work is important as it keeps the pack’s soc higher since the total pack capacity is kept higher. The cold weather brings the capacity down as well.

Starting yesterday afternoon I had to short circuit the pack after driving it until it would barely roll. The pack seemed to develop the classic memory issue again. The pack was only good for 4.5kwh during a drive that day. Not good. So this time I loaded each half of the pack to 1.5 amps with several light bulbs. After a few hours the pack was low enough to load it will all the light bulbs across the entire pack. This brought the load to 2.5 amps. 22 hours later I connected the new 240vac Variac from Ebay to it’s bridge rectifier and started charging the pack.

I had to keep turning the Variac’s voltage up to keep the current at a good charge level of between 6 and 10 amps. That 240vac Variac really sped things up. I didn’t have to do half the pack at a time as with a 120vac Variac. We’ll see if this gets the range back up.

The weather has been in the 40’s to 50’s and I suspect it will lower the range.

When using Dolcom for looking at ground fault info, the standard nominal reading is about +20 counts above the pack voltage.

In my experience when the ground fault reading taken with Dolcom is higher than nominal then the ground fault is between the negative most battery in the string and mid pack. When the ground fault reading is lower than nominal then the ground fault is between the positive most battery in the pack and mid pack.

So far with mild rain exposure the #1 truck had only had a ground fault reading swing about +30 to about -20 from nominal. It looks like the new gum rubber weather stripping is working.

I put an ad on Craigslist for the rear bumper, class 3 trailer hitch, and a bed mounted tool box. These are the parts I took off of both USE trucks to they could have perfectly functioning tilt beds. I wanted only $40 for all 3. But the only fellow that showed interest, did not need the other stuff. So I cut the price to $20 and he took all of it. It was all stored in the wagon. This stuff took up all of the room in the wagon. Now it’s nice and cleared out. Still there is a USE motor back there. I was just glad to get rid of it all.

This morning I headed over to the hardware store to see if they had any 3/8″ fuel line to help adapt the 5/8″ heater hose to the 3/8″ barb. The fuel line was difficult to push onto the barb even with lubrication. In fact I had to use the coolant bottle from my spares that had the barb cut off. This allows the fuel line to barely fit over the barbless inlet. At least it worked. Then with some lube the 5/8″ heater hose fit snugly over the fuel line. A hose clamp made the whole thing water tight. This is what prevented the truck from being finished last night.

The heater element pulls about 8.5 amps at 321vdc. That’s over 2700 watts! The air sure gets warm quickly. On the drive to work I watched the thermometer that I stuck into the vent. It peaked at 130F or so, and then the over temp sensor would shut off the heating element. The temp at the vent would drop to about 105F, then the element would come back on. It was so nice to have a real heater for a change!!!! The bad news is that the heater uses 2.7kwh. So it’s a bit of a load for my small pack.

The original heater hoses were fairly brittle. When I clamped them with long nose vice grips they cracked and leaked. So the heater got all new hoses. I’m a little concerned about using 100% coolant and no water. I may siphon some coolant out and add water. Ethylene Glycol is not as efficient at 100% concentration. I used silica free coolant. A large syringe really helped when I had to prime the pump or remove coolant without any spilling. I used a Dremel tool and fiberglass cutoff wheel to shorten the inboard mounting tab on the Hotstart heater housing. It was a lot faster than using the mill because I didn’t have to figure out a jig. Cut off enough of the tab to just remove the 2 inboard mounting holes and no more. Otherwise there won’t be enough material to keep the seal in compression.

BTW, the heater core tubes coming through the firewall were aluminum. Be careful when adding or removing hoses!

This heater upgrade could really be polished off with a variable temperature control. I thought about it today. The control circuit could be placed with the heater relay in the battery box, or if it fit, into the heater box. The heater box is a bit cramped. I suspect the circuit will need a source of metal around to thermally sink the fets to. The heater box might be too warm, but it would be the most convenient. Maybe the engine compartment is a decent mounting place for at least initial testing. This circuit would also lighten the load on the battery pack by allowing the heater to run at settings less than full current.

The temperature control knob would mount next to the heater button the dash. I think it will fit onto that small cover. An LED would be good to indicate if temperature control is on or not, and at what rate it’s pulsing. Maybe zero to 100hz would do it. The schematic is in pieces but has enough info that I could start on circuit testing in the future.

A lesson learned from an ACP failure that I witnessed, will give the circuit an indicator signal that is actually enabled when there is high voltage present at the output of the fets. This makes sure that if there is a fet failure, that there will be an indicator to tell me that.

I used a Dremel tool and fiberglass cutoff wheel to shorten the inboard mounting tab of the Kim Hotstart heater housing. It was much faster than using the mill because I didn’t have to jig up the heater to machine it.

Don’t forget to prime the pump!! It’s a pain in the butt!! You will smoke your heater if you don’t!!! You can shine a flashlight behind the coolant bottle to make the coolant glow. When you look inside the bottle or through the wall of the inlet, you can see both huge bubbles or microscopic bubbles. Both of them should be moving to show that the coolant is flowing. I used my aux battery to spin the pump without running the heater. A 50/50 mix of coolant and water will help with the priming as coolant is way too thick.

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