Search found 3779 matches

by coulomb
Fri, 06 Feb 2009, 21:28
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

Do chargers like being paralleled? An excellent question, and I'm not that sure. For bulk charging, they are essentially switch mode power supplies, and each of these has a slight droop with load. I guess that means that some of them might not provide as much current as others. In extreme cases whe...
by coulomb
Fri, 06 Feb 2009, 20:05
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

Here is version 3 of my battery paralleling circuit; many thanks to acmotor for his many suggestions: http://forums.aeva.asn.au/uploads/689/switch_and_diodes_v3.png In this version, there is only one (set of) charger(s), so there is no possibility of a shock of two times the charger voltage. I've al...
by coulomb
Thu, 05 Feb 2009, 07:20
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

So you have a one bus solution for the Rodeo? Ah, no, I'm guessing this is already done in Red Suzi, with this box: http://forums.aeva.asn.au/uploads/24/P1030773_inside_charging_box_compressed.JPG BTW, are the fuses in there? Or in the modules? http://forums.aeva.asn.au/smileys/smiley25.gif When yo...
by coulomb
Thu, 05 Feb 2009, 06:52
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

Cut, paste and mirror has got the better of you ! Note diode A/K on positive charge bus. Oops! http://forums.aeva.asn.au/smileys/smiley9.gif    Corrected now, thanks. I would still not use any earth return, even though your were thinking charge current only. For two reasons.... Fault currents will ...
by coulomb
Wed, 04 Feb 2009, 06:58
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

Can you re-draw with fuses at the diodes? http://forums.aeva.asn.au/uploads/689/switch_and_diodes_v2.png Edit: 2 right hand side diodes were wrong way around. Thanks, acmotor! I'm not sure whether to include the contactors inside each battery group, or leave them, as shown, between groups. I'd also...
by coulomb
Wed, 04 Feb 2009, 05:49
Forum: Batteries, charging, management and monitoring
Topic: Power Consumption for Dummies
Replies: 144
Views: 17433

Power Consumption for Dummies

coulomb ...so how is the parallel not cancellin out power as they are connected negative to negative in the begining or positive to positive at the end? The difference is in a series string with negative connected to negative, you are measuring/using two positive leads, so the total voltage is zero...
by coulomb
Wed, 04 Feb 2009, 05:23
Forum: General EV Discussion
Topic: Green Car Innovation Fund
Replies: 57
Views: 4994

Green Car Innovation Fund

Mark T wrote:Was the light plane guy Howie Hughes with his Roadie EV ?
He started by saying that his name always gets a laugh. "My name is Howard Hughes and I produce aircraft". So yes, it sounds like it.
by coulomb
Tue, 03 Feb 2009, 18:39
Forum: General EV Discussion
Topic: Green Car Innovation Fund
Replies: 57
Views: 4994

Green Car Innovation Fund

Ok, I've been yesterday to the Brisbane session. Here are my thoughts: 1) This is not for the very small company or individual that has little money behind him/her. The usual ratio is 1:3 (1 government grant dollar to 3 grantee dollars, and you have to prove that you have your $3). The minimum grant...
by coulomb
Tue, 03 Feb 2009, 18:06
Forum: Batteries, charging, management and monitoring
Topic: Power Consumption for Dummies
Replies: 144
Views: 17433

Power Consumption for Dummies

another question....putting cells in series and in parallel..in regards to making the volts and getting the right amps how does this work? can you explain this to me. I'll have a go at this one. First, let's consider series: http://forums.aeva.asn.au/uploads/689/series.png The two parallel bars rep...
by coulomb
Mon, 02 Feb 2009, 16:01
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

Never use earth return for traction pack currents. It is not safe and you risk super-imposing voltage on the 12V aux system. Run a separate wire. I don't suggest this; only charging current. Traction current will use the ends of the batteries (+350 and -350 wrt chassis). Can you re-draw with fuses ...
by coulomb
Mon, 02 Feb 2009, 03:58
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

If the pack fuses are put in series with the battery connections to ground, then at least any contactor problems like make before break or a flashover will be safe. (In the sense that blowing a multi-hundred amp fuse is ever "safe" http://forums.aeva.asn.au/smileys/smiley3.gif )   Of course, that le...
by coulomb
Mon, 02 Feb 2009, 02:35
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

I suppose we could invert the negative batteries and put the whole lot in parallel. No need for paired chargers, either. Hmmm. Next post perhaps. Oops, the negative side doesn't "invert" quite so easily. So this arrangement might have to be confined to conversions where the positive and negative pa...
by coulomb
Mon, 02 Feb 2009, 02:23
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

Coulomb, keep thinking about the parallel charging of modules though. Add in some diodes in the charging lines. It would be intersting to see if you come up with something similar to my (yet to be posted !) circuit. Ah, I think you might mean something like this: http://forums.aeva.asn.au/uploads/6...
by coulomb
Mon, 02 Feb 2009, 00:14
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

The use of contactors to bypass is IMHO not a requirement as batteries are generally reliable Well, it just seems criminal that one bad cell out of perhaps 220 can stop you from getting home. Bypassing a module would allow an almost normal ride home. One factor to consider is the contact resistance...
by coulomb
Sun, 01 Feb 2009, 17:06
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

Bypass is hopefully rare enough for it to be a manual operation, but depending on the pack location (e.g. On Ute Tray vs Under Body) it may be desirable to have it remotely switchable. You might change your mind if you have an older pack with a handful of bad cells. What did you use to draw the cir...
by coulomb
Sat, 31 Jan 2009, 17:33
Forum: Technical and conversion discussion
Topic: NCOP14 regulations, safety and revision
Replies: 143
Views: 15584

NCOP14 regulations, safety and revision

easy. 144V pack is actually +/- 72 Volts if you ground the centre via a relay or ... Suppose you have a 576v nominal system made up of four 144v modules. I don't believe that any manufacturers of 144v modules do/would provide a "centre tap" for this. I don't want to void the warranty of my modules ...
by coulomb
Thu, 29 Jan 2009, 08:51
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

I saw a4x4kiwi contactors which split his pack into 12 x 48V packs and a 24V pack for charging. It made sense for me to join them all in parallel to 1 48V pack for use with a big charger. The way to do this was DPDT contactors:     48V Bus + ---O O--- + 48v block - ---O O--- - 48V Bus              ...
by coulomb
Tue, 27 Jan 2009, 18:45
Forum: Members Machines
Topic: Red Suzi
Replies: 217
Views: 53861

Red Suzi

I am not using the brake resistor at present... I did consider connecting the battery pack to the Danfoss via a power diode (100A , not much PIV needed) shunted by a power resistor to carry the regen. I guess you don't need a diagram there. Use a braking resistor as normal for the controller to dum...
by coulomb
Sun, 25 Jan 2009, 23:06
Forum: Technical and conversion discussion
Topic: Hang on to those Phone Chargers!
Replies: 14
Views: 4338

Hang on to those Phone Chargers!

Nice stainless wire coils. Good for testing battery chargers, but not necessary on BEVs. That's what I thought for a while too. Unless you start at the top of a big hill, it'll take more energy to accelerate to braking speed than can be recovered by stopping, therefore no need for a braking resisto...
by coulomb
Sun, 25 Jan 2009, 19:08
Forum: Technical and conversion discussion
Topic: Hang on to those Phone Chargers!
Replies: 14
Views: 4338

Hang on to those Phone Chargers!

I am in the process of designing my brake resistor controller ... Johny, do you mean an active resistor circuit, or an AC controller that requires an external brake resistor? For the regen brake resistor, which hopefully would be used only when the pack can't take any more charge, I was thinking of...
by coulomb
Sun, 25 Jan 2009, 18:39
Forum: Members Machines
Topic: Red Suzi
Replies: 217
Views: 53861

Red Suzi

Ah, OK, thanks acmotor. So it's basically a "not-so-badboy": isolated (assuming it's not an auto transformer), inrush protected, EMI filtering, etc. But it uses only a handful of components at the input end of the controller. I had visions of you using the motor as a single phase to three phase conv...
by coulomb
Fri, 23 Jan 2009, 21:59
Forum: Members Machines
Topic: Paul's VS Ute 55kW AC & LiFePo
Replies: 20
Views: 7462

Paul's VS Ute 55kW AC & LiFePo

Electric Motor: 55kW 3-phase AC (Azure Dynamics – USA) Nominal 415v AC Not that it really matters, but with a 320vdc pack, the highest AC voltage you can generate (with neutral wobble) is 320/sqrt(2) ~= 220v. So I'd say it's a 220v motor. Batteries: Brand: Thundersky TS-LFP90AHA Type: Lithium Iron ...
by coulomb
Fri, 23 Jan 2009, 20:23
Forum: Members Machines
Topic: Red Suzi
Replies: 217
Views: 53861

Red Suzi

acmotor wrote:The 'VLT charging' was simple but perhaps too simple.
I only use the 48V module charging method now.
Can you explain how the VLT charging worked, please? I'm curious.

Thanks.

- Coulomb
by coulomb
Fri, 23 Jan 2009, 18:33
Forum: Technical and conversion discussion
Topic: DC to DC converters
Replies: 85
Views: 14077

DC to DC converters

96V is a bit on the low side when it is expecting 110 x 1.4 = 154VDC although most SMPS seem to work down to less than half voltage. The input circuit of most power supplies is similar to this (ignoring fuses, thermistor, etc): http://forums.aeva.asn.au/uploads/689/ps_input.png When the switch is c...
by coulomb
Fri, 23 Jan 2009, 02:45
Forum: Batteries, charging, management and monitoring
Topic: Home grown BMS ideas !
Replies: 781
Views: 114451

Home grown BMS ideas !

Voltage doubler circuits are inherently lossy. They will only supply very small currents. ...Ric Yes, that seems to be the received wisdom. Where are the main losses? Ferrite losses in the inductor? FETs are pretty efficient, and the copper losses are pretty easy to keep low. Perhaps it's junction ...