Ive had a few pms from people asking what my charging setup/equipment/batteries are, so rather than keep on typing it out each time I thought i'd chuck it up 'ere.
I want to firstly state openly though that I am still quite new to lipo and the rest of it, so there's a good chance that there's a better way of doing this, and a small chance that I may even be doing something wrong (though I've had no fireworks yet!). Anyway, here we go...
The current batteries...
http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=19499So far so good, about 12 cycles down and they seem to be gaining a little capacity each time. As of writing, about 8 ah from 4.15 to ~3.75 (im running them 20s 2p). I have LVC set at 3.6, witch is about .1V above where the cells start to become unbalanced during discharge. Ive yet to drain them below about 3.7 resting so far, and they seem to stay very well balanced ruining them this way (less than .01V variance between each 5s2p pack when I come to recharge). I havent looked closely, but they seem to only drop about 2-3V or so under a 5C load, and that's when running 20s (so an average of .125V per cell). It could be more or less, but when running 50A through a HT I dont normally take the time to look at my CA
. I did however recieve 1 dud pack out of an order of 9, so as always with HK buy 5-10% extra to save on waiting for a replacement to be sent out. Hk were pretty good with returning it though (to the AU wharehouse, then refunded the $$)
The Charger
http://www.fmadirect.com/new_applications/powerlab8.html
Expensive? yes. Powerfull? Definatly. Worth it? I think so.
This is the only charger ive owned, but from what ive read it seems to do the job as good if not much better than anything else. The PC connection is great, lets you generate graphs of cell V, individual cell IR, pack V, pack capacity, how much power your drawing from your supply and supply voltage, the list goes on. Though I havent had to do much balancing yet, it seems to be the bees knees when it comes to this too. Its able to balance during charging (apparently not all lipo chargers can) and can pull up to 1A from an individual cell or cells to allow others to 'catch up' and balance out. Has a 100W internal/1.3kw external discharge mode too!
A long story short a great charger, able to charge up all 8 5s packs at once, in about an hour (set to auto 1c charge, witch isnt the fastest but prob the safest+gentle on cells).
The power supply...
to power this monster I have 2 ex-server power supplies, that can supply 55A at 12V. They're connected in series (with some modification) for a 24V 55A power supply. Cost me $35 delivered, and about 45min worth of modding to get them to run safely in series. Ill may do my own writeup at some point, but for now this
https://sites.google.com/site/tjinguytech/my-projects/diy-24v-47aIs where I got all the info I needed to get these guys running. Many thanks to T Jin (I think that's his name).
The wiring...
basically, I have each of the sub 5s 2p packs permanently hooked up in parallel, both on the discharge leads and the balance leads. The main leads are hooked up in series and then to my controller for discharge, and for charging I need to reconfig the pack from 20s 2p to 5s 8p. The main leads (4 M/F combo's total) are disconnected form series, and reconned in parallel with some 4-1 parallel leads. the balance leads I have running to a 25pin DVI connector. By plugging in another single DVI connector I can connect each of the 5s balance leads from each pack into a single 5s pack, rather than having to plug in each one individually to some 4-1 parallel leads. All in all takes me about 3-5 min to reonfig for parallel charging (including removing the bats from the bike). Works like a charm.
You could save a few bob and buy a few 6s chargers off HK, and get a similar power output than the CP8, but to be honest the cost difference didnt seem that much given the gap in quality (in my eyes at least).
This should give you some idea what I mean... just make sure that your discharge leads
ARE NOT plugged into series when you connect this, unless you like fireworks on your bike.
BMS?I didnt bother with any sort of BMS or cell based LVC due to the number of people stating that if the inside these units happens to go south then itll likely take the whole pack with it, sometimes with some explosive results
that, coupled with reports that those without bms/lvc boards have few to no issues so long as they're smart about it, and the decision was easy.
Future mods...
I've bought one of these
http://www.bmsbattery.com/alloy-shell/28-alloy-shell-900w-lifepo4li-ionlead-acid-battery-ev-charger.html for bulk charging, and will probably only balance once or twice a month depending on how well cells stay in balance. Im also going to make a cell level allarm plug using 4 of these
http://www.dealextreme.com/p/1s-6s-lipo ... larm-72381 so I know if any 1 cell dies on me, or if the pack gets way out of balance. I may end up switching to 24s too, for a bit more speeeeeed
. alternatively I have enough to make a 20s 20ah case, for all those times I want to ride for 6+ hours straight
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Damn, didnt mean to make that so long winded. Ah well, writing this is a great way of procrastinating when I have uni work to do.
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Keep giving it to much and falling off the back. Moving the battery case down lower should help with the balance.
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For now I've just been using good ol' ducktape/electrical tape, but it then becomes a major chore to disconnect anything... Ive had a hunt around for some waterproof connectors but they dont exist locally, and I'd like to get this done in the next week rather than wait a month or more for shipping from china!
