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Wednesday, August 19, 2009

Battery Fairy Now Ships UPS

Of course, that's Uninterrupted Power Supply, not the destructive gorillas in the brown trucks. :-)

The battery fairy came by yesterday, with an old server-sized UPS with both the internal and external battery packs. Unable to sleep due to various things going on in my life right now, I spent the night until dawn or so disassembling the units to get to the batteries and check them out.

The external box just has 4 batteries in it, setup as pairs, two bolt-down wiring tie-in points, and a 100-amp fuse holder to fuse from the next box into this one. The Anderson connector shown on the back is to go to the UPS, then there is another internally-mounted Anderson connector to allow further daisy-chaining of these boxes to the UPS for lenghtened runtime.

It's a nice enough box that I may use it as-is on the trike, if I ever get that far with these batteries (they might not last long enough, as I don't know their age).

They slide out easily enough, with a string-pull on the Anderson connectors to make them easy to disconnect. I'll be leaving those string pulls on just in case. :)

Under a plastic taped-on-with-foam cover are the bolt-on terminals, recessed in each corner of the batteries. Much better than slide-on tab type battery terminals.

The batteries themselves came taped together by a layer of doublesided foam tape between them into 24V "RBC"s, with a 100A fuse bolted between them at one terminal pair, and a 600V/50A Anderson connector at the other.

Those connectors are as useful as the batteries themselves, because it means that now I will have enough of them to make easily disconnected "packs" for the bike. I did not have that option before, and had to bolt on the wires to them each time I mounted or dismounted the batteries from the bike, for fixing it or working on it, or even just to take them off and ride it without motor or batteries for any reason.

All but one pack read at least 23V unloaded; the last read 20V.

Even so they all ran my treadmill motor just fine, even when I put enough load on the shaft to draw about 8 amps (instead of the 1.3A or so it draws unloaded, at 24V).

One battery of the 20V pair is only at 9V, and may have a shorted cell or something. When I put the wheelchair battery charger on this pack, the charger light randomly pulsates at various brightnesses, instead of going off (dark) to show a charging cycle is in progress.

Monitoring the voltage across the low battery shows from 9V to 15V to 17V, while the other is steady at around 15V. So there is almost certainly something wrong with this battery, not likely to be cured by charge cycles.

During charging, maybe 5 minutes in, one of the other packs starts to make very faint bubbling sounds, but loud enough to just barely hear in the quiet room. I had to put my ear up to the side of each battery to figure out which one was doing it. Voltages seem ok on them both, so I'm not sure what's wrong. Current is only 3A max out of the charger, and 5A is the nominal max input current to the battery.

Another pack seemed to take charging normally, with no sounds/etc. After warming up a bit during charge, I unbolted the fuse and Anderson connector from the pack and pulled the two batteries in it apart, so I could read the label/specs of the individual cells. (The outer labels from APC only specify that they're a pack for use in APC stuff, etc, and to use only APC replacements yadda yadda. No numbers).

12V 17Ah by Sacred Sun company, (Shandong Sacredsun Power Sources Industry Co. LTD), max charge current 5.1A. I'm guessing around 13 pounds each, maybe 12.

I'm now letting that pack (as two cells) charge up overnight, then will do the same for the other three.

They're also easier to fit outside my cargo pods. I could even just strap them to the cargo pod-to-bike frame adapter, under the seat, without a battery box, at least for when I'm going to work, since the bike is inside instead of locked up outside where I can't keep an eye on it.

With 8 smaller batteries, of which possibly two might be bad (or will at least fail before the other 6), I have a lot of options.

They can be setup as a series pack for high voltage on that treadmill motor (rated at 120VDC/7000RPM/21A), as a 96V 17Ah pack, at 104 pounds, which would probably not work on *this* bike but should on the trike, and would make it a very powerful long-range vehicle.

They could be setup as a bunch of 24V packs, kept charged and ready to quick-swap out when I get home should I need to go right back out somewhere. If there are any places (like friends' houses) that I have to go where I might need to fully charge up in order to get home, I could leave a pack there on a trickle charger, and simply swap out for the one on the bike when I get there, instead of waiting for what might be several hours (it would also save me the several pounds of charger weight).

36V or 48V packs are also an option, with either one or two packs on the bike, for greater range. I don't know how well the wheelchair motors will hold up under 36V (nominally rated at 24V) but I have tested one of them at that voltage using the three larger 31Ah batteries in series, and it does run, although it is considerably noisier than at 24V.

The treadmill motor is by itself very quiet, but with the alternator fan on it's shaft it is like having a little bitty box fan on high. Moves a lot of air, though, and keeps the motor pretty cool at 24V and 36V. Probably at higher voltages, too, since it's original use at 120V running the treadmill didn't even have a fan on it, just some very minimal vanelike strips on the back of the cast iron pulley/flywheel that came on it's shaft. Those did not move much air at all, even at rated voltage (though they were much quieter). Still, it's a lot quieter than any of the wheelchair motors, and has more raw power potential than they do. Harnessing it's power is more of a challenge, since it has no easy-to-use gearbox built onto it like they do, forcing me to build my own systems for that (like the pulley-then-chain drive I tried it with before I got the wheelchair motors.

Besides the batteries and cabling, there's also a wealth of other EV parts inside the UPS:

More 100A fuses (which I think I'm going to use one of on each battery in case something stupid happens, since it *is* possible to connect batteries together directly in parallel with these Anderson connectors, and if one is fully charged and one is fully discharged, I can imagine some "interesting" things that could happen.

Interesting as in the Chinese curse and as in traditional Chinese fireworks. ;-) I prefer boring to that kind of interesting, and hopefully the un-hole-y kind of boring. (yeah, I can hear your groans from here, just be glad I don't do that a lot more).

Inside the battery box is the 100A fuse on top of this pic, with the internal Andersons to each battery, wired in series for 48V total in this box.

More of the UPS case itself, from the back, just prior to disassembly.

Off comes the outlet and breaker section, since it has these inviting arrows pointing at the screws on it.

Three panel-mount 30A thermal circuit breakers, push-to-reset. They're definitely handy. I think the one I have in the system right now is a 20A.

More Anderson connectors.

The front panel electronics. Not sure I have a use for them yet, but you never know.

The interior, main board, transformers, wiring, and a 120MM fan (24VDC 0.40A). Unknown CFM or sound level; standard 3-pin plug with power, ground, and tach.

Back of the board. It has spots for more MOSFETs and more relays, must be for the next model up or something.

24V 30A SPDT relays. Exactly like the ones used in my ScootNGo controller, except for having twice the SNG's current rating. I will probably use these as contactors for the system, since right now the ignition key only breaks the pot throttle circuit (as specified on the 2QD, which makes it turn off due to "pot fault" detection). That leaves me with no way to totally disconnect power except for disconnecting a battery manually at some point.

The full board. It's quite large, at least one and a half square feet, I'd say.
The four heatsinks each have 5 MOSFETs, IR630P on the front row (can't see the others to tell). Room for 3 more on each heatsink.

Room for more relays, too.

Those MOSFETs are a little hard to read, since they're so lightly printed. None physically looks blown, and at least one in each parallel set must be working, because the gate test works on all 20.

Some very tall caps, too. About 1.5" across, and about 5 inches tall, 75V @ 1500uF. 3 of them.

A whole board full of various kids of caps, chips, transistors, diodes, etc.

Many of the components to build a second full 2QD are on this board, perhaps everything but the LM339 (which I still have another one).

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