96 volt DC to DC converter?

gottdi said:

Been using this one with no troubles.

HWZ Series DC/DC Converter 96V to 13.5V 25A

http://kellycontroller.com/hwz-series-dcdc-converter-96v-to-135v-25a-p-371.html

Click to expand...

That has potential, it says it works from 75 volts to 130 volts and I can live with a little higher minimum. Perhaps I should explain what I have in mind...

I'm getting the lead out of the buggy in my avatar. I have removed the Optimas, the charger and the battery monitoring system with its neatly tied spaghetti. It will have a small Lithium pack and I'm looking at my choices. One option is a 96 volt, 32 cell, pack (down from 10 Optimas.) If I go down in voltage I will need a new reliable DC>DC because I don't run a 12v system battery and don't intend to unless/until I install a Zilla controller. The car has been without a 12v battery for over 10 years, I understand the pros and cons (it's not like it has 4 way flashers.)

If I go with a 32 cell pack I can put the entire pack in the floorboard boxes that run under the front seats and rear seat floor. It would look real clean but the performance would be less. There would be nothing up front where the gas tank used to be and you could see through the car between the rear tires too. With the little Prestolite MTC replacing the engine, no gas tank, not even a 12v battery cluttering up the area under the rear seat it would be a very simple and clean look for presenting an EV, even simpler than a gas buggy. The car would weigh about 1150 pounds with the pack, about 50 pounds more than when it was gas powered with the weight shifted low and center. It weighed 1420 lb. with 10 Optimas and an onboard charger.

From there my options go upward. If I put 4 cells on each side under the rear seat (there was an Optima on each side) I will have a 120 volt pack and my existing Todd PC20-LV DC>DC will continue to work fine. I could add a small 12 volt battery up front and put a Zilla above the motor (The Curtis 1221B is above the transaxle and right between the tires.) I could even install another 5 in front in place of the gas tank (maximum pack of 45 cells) though I'm planning to eliminate the longer cables and front rack to leave the room for a possible onboard charger. I've also thought that a Soliton with its built in main contactor and artful case would look nice bolted to the back of the rear seat right above the Prestolite motor.

Range should be better with the lithiums. What brand lithiums are you thinking about? CALB's or TS or GBS? 100 or 200 AH cells? I think your performance should still remain reasonable since your going to be replacing the curtis with a zilla. I peeled out my 12 battery because it was too unreliable and would not hold a charge good enough and caused my contactor to shut down a couple times while out driving. Once I put in the dc dc it never had that problem and since I was only running head lights and other running lights and an occasional windshield wiper I figured the DC DC would be fine and it has been. Never getting hot either.

Why not go with a 120 volt pack. That is only 38 cells right? I am sure you could figure out how to stuff in 4 more and keep them out of the front. If your going with 100ah cells you should have no trouble fitting them in.

What charger are you going with?

Pete

The cells will be TS because they haven't let me down so far. I've done up to 5C without the voltage going down to 2.9 vpc. The CALB has a new size for their 60 amp cell that looks interesting though, it is basically a thinner 100 AH cell. It would be a good way to run up the voltage (though not the power because you can't pound a 60 AH cell as hard as a 100.)

I can stuff 32 (4 rows of 8) cells under the front seats and rear floor. I can add 4 on each side under the back seat (40 cells total), I had one Optima on each side there. I could stuff 5 up front (where I had 2 Optimas) but that means putting the front to back wiring back in. So I have been looking at 4 possible cell counts, 32, 37, 40, or 45 (I suppose 36 and 39 would also be awkward options.) It is easy to always think more, more, but there are reasons think about it more. I've pretty much ruled out adding front cells even though it would help weight distribution.

One is just a matter of esthetics, keeping it pretty. I could pull that off with any cell count but some would be cleaner than others. All in the floor is mesmerizing to me because it is so clean and so simple, but it actually cuts power. On the plus side, even that pack would increase the range.

Two is that this is a limited use vehicle. I drive it for around 6 months of the year and park in the garage over the winter. Western WA is not exactly roadster weather. I need to consider cost how much I really get to enjoy that money. I do enjoy power but the real world doesn't let me enjoy it that often.

Three is wiring and battery management. I need to be able to easily read each cell voltage and get to it with a charger or resistor if for some reason balance gets off. I haven't seen any need yet, but I haven't seen 7-10 year old LiFe packs either.

I will most likely end up with a 40 cell pack. It would be around 70 pounds heavier than a 32 cell pack. It is most like what it has been for the last 11 years (only better.) This will be the EV Buggy version 2.0.

Nope, the charger has 10 end voltage settings to taylor my pack to what I want. I am using 38 cells for 120 volt pack. The end voltages are user settable. So If I want to end at lets say 3.5 volts I can. We will be starting out with 3.57 per cell or 136 volts for the packs max voltage. All my cells must be well matched first so no one cell goes into over voltage. This I must check before I am able to leave my charger on it's own. The charger will stop when pack voltage is 136 @ 2 amps. Manufacturer recommends 3.8 volts per cell or 144.4 volts total pack. That is not resting voltage mind you but should be close when that final voltage level is terminated at 2 amps. Some recommend stopping at 0 amps but I am stopping before that to allow a little less after the surface voltage drops away.

Pete

I am balancing the cells now. Most of my cells are at 3.32 volts already. I had to cull out two to bring down in voltage but won't be using them till later. I have others that will be put into the pack and monitored closely until I have the few cells up to snuff.