Hmm.. I got a DC-DC converter from powerstream (see Bleah, not enough amps for an exaplanation of why). It's rated for input range of 36-72v and output 12v at 12.5 amps. It should be sufficient for my Lectra's needs.
Unfortunately.. I hooked it up today to try and play with the lighting system and get that straightened out. Unfortunately I found the DC-DC isn't producing a steady voltage, instead it's bouncing from 8-10v pretty rapidly. Fully charged my pack is reading 70 volts (60 v nominal) so of course that's at the top end of the rated input range.
I'm beginning to get very frusterated, every DC-DC angle I try is being thwarted. Today I started thinking of an escape route through other technologies instead of DC-DC.
The purpose for DC-DC is to keep the pack balanced (rather, prevent imbalance). The simplest way to get 12v is to tap one battery in the pack. That works except that the battery you tap has greater load than the others, depletes earlier, and generally all the bad things from a misbalanced pack. The DC-DC route cures that by drawing from the entire string, converting that to the desired end voltage.
One option is to have a secondary battery, 12v, that's charged separately. Oh.. hmm.. I just had a strange thought... Because it's hard to find a 60v charger, I have two chargers, 48v and 12v. If, e.g., the battery that's charged at 12v had an extra battery connected to it, this would cure the imbalance. Aaaaahhhh... that's worth thinking over.
Another way I could have a secondary battery is these old 12v NiMH packs I have lying around.
The PowerCheq / BattEq approach is a different alternative. You'd tap one of the batteries to get the 12v system, and then trust the PowerCheq or BattEq (your preference) to keep the pack balanced.
I put a ? because maybe there's a different option.
I do kinda like the variant I just thought of above. In case it didn't make sense I'll explain what I'm thinking... the pack is made of 5 buddy-paired 12v 26AH batteries making 60v 52AH total. What I'm thinking is that I have a spare 12v18AH battery and it could be paired with one of the existing pairs. Specifically it would be paired with the one already charged by a 12v charger. It's that battery which would be tapped to drive the 12v system. The pairs would all be 12v52AH except for this one which would be 12v70AH.
Hurm...
I was thinking the same about the DC-DC headaches. I have a nice DC-DC unit but it is kinda big for the bike (will use it on the motorcycle). My latest idea is to use a "smart" tap that looks at any subpacks in the string and chooses the highest voltage one for tapping the 12v for the lighting system, etc. This "device" would dynamically be deciding which subpack to suck off of during use.
Jeff K. Bubank, CA "Bike to the Future" and "Deep Cycle"
The separate extra battery and 12v charger would be the simplest way to go.
I wonder why the dc-dc you got is misbehaving?
The surplus switching power supplies might work if you parallel the output from several to get the current you need. Some of them are very inexpensive. If you used 4 of them, for example, you could possibly mount them in separate locations to make use of available space.
surplus switching power supplies Yeah.. you mentioned that before. I went to halted specialties (my local surplus electronics store) (which, by the way, is across the street from Green-E-Motor's storefront.. coincidentally) and they had a large range of surplus power bricks, only one of which was close to the required specs. Output of 12v3.5A (I think) for $15. I think it's worth stopping by later today to get one to try out.
While there I noticed that PC power supplies tend to have a 12v20A output (and a few other outputs). That's an interesting possibility.
The separate extra battery and 12v charger would be the simplest way to go. It's good to know I'm not crazy. It does make sense and I already have this one battery in the pack (like I said) that's on a 12v charger.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
It's good to know I'm not crazy. Well, not any crazier than the rest of us.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
I wonder why the dc-dc you got is misbehaving? I didn't get any response from powerstream. Maybe I have to call them on the phone.
Thinking that maybe the 70v of the Lectra pack was too high.. I connected it to a 36v nominal pack on another vehicle. Again, the voltage is bouncing up and down the same way. It's something screwy about this DCDC converter.
surplus switching power supplies might work
I bought one of the power bricks I'd found at halted specialties. I just hooked it up to the battery pack ... the first way I hooked it up, no volts came out the other end. Then I reversed the connection and got 12v. So, yeah! This gives an option that's much more affordable than the DC-DC's.
I made a little mistake. I cracked open the plastic case. Inside the case there's a copper shield around the whole thing, and it's clear the innards are not going to be easy to insulate. I shoulda left the case in place...
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
David, Those inexpensive DC-DC converters do not have isolated ground so if your using a frame negative as a "wire" it may be upset... Jeff
Jeff, Are you referring to the DCDC I got from powerstream? The input has +/-/ground and I don't know where to connect ground. I'm not using the frame for the negative part of the wiring.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Okay, good news. I called Powerstream just now.. It has a "minimum load" and if the load is below that threshold it goes into a standby mode. I didn't have a load on the thing, so it went into standby mode. Their genius claimed it's printed on their website but either I skipped over it or ..? It does say on the side of the unit "Minimum Load 0.1A" ...
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Good deal, that should solve your problem.
As predicted by powerstream.. as soon as I applied a load, it came right up to 12v (er... 11.9v).
BTW I also tonight got a different step further in that I worked out the wiring for the headlight. That leaves puzzling out the mysteries of turn signals still to go, and then the lights wiring will be finished. er.. okay.. I already researched turn signals. It's just a relay that controls whether to switch the flasher unit into the circuit. What is to be puzzled out is the way this is implemented in the Lectra.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki
Ok Scooter People,
I'm going to get my XM-3000 next week (they tell me). Unfortunately the BattEQ's I ordered are not in stock, and they are overpriced. The PowerCheq for various reasons is an inferior product. This leaves me (and a lot of others I imagine) charge/discharge equalizationless. So I'm thinking we need a 3rd option.
I'll design the hardware for a new battery equalizer and leave it open source so the people on this form and others can hack it. I'll sell it in kit form to keep the prices down, or if you don't want to bother soldering it together, I'll initially stock some hand made ones.
Tell me what you like and don't like in your BattEQ's Powercheq's and what you'd like to see in a superior battery equalizer. Since it will monitor each battery, it will not be too hard to add an LCD to display each battery's information. I'd also like to be able to have the charger be onboard and have it have a mode to desulficate the lead acid batteries.
--Jeff
XM-3000...
-DC-DC converter replaced with a Dell D220P-01 power supply.
-72V mod
-Expensive bank charger until I come up with something better... Still trying.
-
Jeff - I'd buy one of those. I also have an xm-3000 coming next week. I will use it for my 15 mi commute to work. For now I intend to string charge it at work and bank charge it at home. I think you should start a new thread to discuss your idea. I'd be interested in hearing about the theory and circuit design.
John
Jeff & John..
I've also got an xm-3k coming.. just got a backorder notice the day after an order notice, though.. :/
I found some vector 2/6/10's through amazon cheap, & ordered 5 (~ $140 shipped). I'm planning astar's simplified bank charging circuit & have the connectors & terminal strips coming for that. So i'm also planning a bank charger for home, & use the string charger for roaming.
I like the paktrakr for monitoring features.. but i don't know if any of the equalizers really will do the job.. better to bank charge each battery. I've been tinkering with electric scooters for a couple of years, but this will be the biggest. The battery care will still be the main maintenance issue for longevity, i think.
Anyway, i'll be watching this forum with great interest when the new xm's come out.
Does anyone know if the xm-3000's have a 60-12v dc>dc converter for the 12v accessories? Or do they just run off one of the batts? What did the xm-2000's have?
Thanks to all for the great tips & info on this site.. makes it a lot easier to not have to re-invent the wheel all the time!
scotty
scotty, Sedona, Az
xm-3000 60v, 38ah silicones, since 7/08
quazar 48v, 12x12ah, since '05
5- vector 2/6/10 bank chargers
Cool, it sounds like there is a demand for these. I spent my weekend learning about lead acid battery charging and read over the patents BattEQ uses. If you ask me there is nothing patentable there, but just to be on the safe side, I'm going to make a design that doesn't infringe upon theirs. I already have one idea how to do it, but will investigate more over the week.
When the XM-3000 comes I'll be able to tell how much space I have to work with, maybe I'll be able to fit it with an onboard charger so we can plug in on the road. From what I read, you don't need to worry too much about equalization when the batteries are brand new, it becomes more of a problem as the cells take on their own personalities with time.
EDIT-- The XM-3000 came, lots of room to work with. I was going to build a switched capacitor equalizing system like the BattEQ and sell it in kit form or completed for a bit extra, but I'm worried about patent infringement, so I dropped the idea, but for anyone who does want to build it here are the schematics, from a real Electrical Engineer, all you need to do is optimize the component values, his design uses a capacitor instead of a FET for one part taking away some of the most costly components:
http://www.electric-lemon.com/?q=node/151
In the next month or two I hope to complete a PWM charger that can charge my bikes 5 batteries. I'll have extra boards made for anyone who wants to have it. It should save us all some money. Will also serve to do the same things the PakTrakr does. We'll see, it's the most ambitious project I've ever embarked on. I'm using the best charging chips from Texas Instruments (UC3909), it should keep the patent infringement lawsuits away from me, but I probably need to talk to someone knowledgeable about these things.
XM-3000...
-DC-DC converter replaced with a Dell D220P-01 power supply.
-72V mod
-Expensive bank charger until I come up with something better... Still trying.
-
Thanks for the input, sparky.. sounds like you'll be coming up with some good stuff for the ev community. I'll definitely be interested in whatever you come up with, & i'd be glad to be a guinea pig. :)
For now, i'm planning on a labor intensive regime of monitoring all the batteries' voltages at start of charge, then again after charge.. i might log the results. I'm also going to watch carefully the first batt in the string.. a problem that has come up before in ev's. I'm hoping the bank charging setup will solve a lot of the battery issues.
If you (or anyone) could come up with a device that monitors the batteries, balances the charging, logs the data, scratches your back & makes a cappuccino, that would resolve a lot of battery issues with ev's.
I also wouldn't think there'd be much to patent.. we're talking charging circuits.. they've been around for a long time. But i don't know how patents work with electrical circuits.
Anyway, let us know how things go, & what you come up with, & how it works. I'm sure there are a lot of people who will watch with great interest!
scotty
scotty, Sedona, Az
xm-3000 60v, 38ah silicones, since 7/08
quazar 48v, 12x12ah, since '05
5- vector 2/6/10 bank chargers
I have a couple patents for some things which I'm not sure are patentable. However the lawyers and the patent office all agree the idea was patentable. They say to me patentability isn't limited to bolts of inspiration direct from God, but also available for new/unique combination's of parts in a novel application.
- David Herron, The Long Tail Pipe, davidherron.com, 7gen.com, What is Reiki