Recent content by Jeremy Harris

Sorry for the delayed reply, been busy with new house-related stuff over the holidays. As Neil says, we spoke on the 'phone a couple of days ago about this. I bought some of this thin PTFE wire for Halls a couple of years ago and have found it to be really good. It's a pain to strip, unless...

No need for the zener at all, if the right resistor values are used. Just an extra component that adds nothing useful. The FETs need more than about 6 or 7 V on the gate to turn hard on, and less than 20 V to be safe, so there is a massive safety margin if the right resistor values are used...

Yes, no problem if you are going to mount them on an alloy bar as a heat sink. My rule of thumb for TO220 FETs with no heat sink, mounted inside a sealed case (which is how mine are mounted), is no more than about 1W, but if you can bolt them to the case then that makes a big difference.

A good general rule of thumb for these controllers is that the FET dissipation is roughly double the resistive loss (because of switching losses). A 12 FET controller running at 40A will be dissipating around 3.6W per FET, around 1.8W as resistive loss, and 1.8W as switching loss.

I see you've quoted a comment by etriker (personally I find very little of interest in his posts so have him permanently on ignore). For the record, etriker made several posts, one after the other, on this thread that were just repetitive statements, unconnected with either the topic or the...

It's best to use the data sheet maximum figures, rather than the typical, just to be safe, so 3077s are really 3.3mohms, 4110s are really 4.5mohms and 4310s are 7mohms. If you had 4 paralleled 4310s, then the total on resistance would be around 1.75mohms max. At 40A the power loss in the FETs...

If using the much higher on resistance IRFB4310, then I would strongly advise using more of them in parallel, to reduce the total on resistance. I've found that I can just about get away with two paralleled IRFB3077 FETs (3.3 mohm on resistance each) for a 20A switch, and four IRFB4110 FETs in...

I described my way of doing this here: http://endless-sphere.com/forums/viewtopic.php?f=3&t=40142#p586436 I found that even for low current use there was a big benefit in using several FETs in paralell, just to keep the temperature down in the FETs. My first version used a single IRFB4110 on a...

Yes, but in my case it only took one cell to fail to cause the fire, so in essence the cause is similar. My guess is that your charger may have been designed back when NiCd cells were far more prevalent than NiMH, and it's the latter than are more sensitive, it seems, to being over-charged. My...

The circuit in the thread below does this, and manages the capacitor inrush current when switched on. The isolation when the switch is off is very good, I couldn't measure any current at all flowing when switched off and two of my bikes have this type of switch as the only power switch, and I...

I had a massive fire and explosion from accidentally charging some NiMH cells in parallel, at a charge rate that was only about 0.1 or 0.2C, IIRC. I'd thought (wrongly) that at a low charge rate this would be safe, but it nearly burned my house down. Are you sure that the charger in question...

The plan is to build a controller to run a paralleled pair of Colossus 80-100 motors (on a common shaft). The reason for choosing this arrangement is really because I can then fit this double motor in the space where the air box used to be on my RD50, leaving most of the old engine/gearbox...

Merry Christmas to all, and the very best wishes for the coming New Year. The shear size and multicultural membership of ES, with everyone around the globe that's here sharing a common interest in pollution free, low impact, transport, is heartening in this age where so few seem to care much...

It may be that the voltage drops with the flat battery as soon as there is any load, causing either the controller low voltage cut out to activate os perhaps the battery BMS low voltage cut out to operate. Was the meter connected all the time, or only when you were testing the battery voltage...

As already said, forget this idea, it will give no end of trouble and isn't practical for the sort of current that an ebike battery has to handle. Either get the cells welded together with nickel tabs (there's a long thread here on a cheap way to do this) or do what many have done and learn to...