BMS NIMH for vectrix.

I cannot find the manual or installation instructions.

The website seems to be much hype with little technical detail. Maybe that's just because they do not want to scare people off, but it puts me off.

Hey guys,

the idea of adding a BMS to the pack has been in my mind for a long time.

I think the existing systems are too expensive. If you're going to put down more than 1000$ or so, you might just as well save them up to put Lithium in your bike.

A while ago, I started experimenting with some electronics, with just one idea in mind: builing a cell/cell battery 'monitoring' system (no, not managing).
I'm still far from that for now, but if electronics interest you, you might be interested in some ideas that came up in this discussion.

I'm currently experimenting with smaller packs/cells, but I'm still a long way from getting it right.
I'll keep you updated if I get further, maybe asking some of your advice in the process.

T

I would have to agree that over $1000 for a battery management system is ludicrous.
That MAX11068 chip looks definately interesting. Obviously from the skim read i've just done unless you are multiplexing the input it you would need 10 chips to interface with all the batteries. But that is only $70 of chips..... very very interesting. Its certainly got my interest in electronics jumpstarted again after a 5 yr hiatus.

That MAX11068 chip looks definately interesting... Its certainly got my interest in electronics jumpstarted again after a 5 yr hiatus.

glad to hear that! I have not yet experimented with the chip, but if you have some basic design ideas with them in mind, you may always share them with me..

Original Vectrix don't even have a BMS ?

Original Vectrix don't even have a BMS ?

Now that's just mean, rubbing it in! :-)

Original Vectrix don't even have a BMS ?

It wasn't really necessary,

A Nimh cell will survive both overdischarge (even so bad that the cell is -0.2V) and overcharge.
A Lithium cells fails immediately when subject to the same conditions.

A nimh cells self discharge rate increases with SOC and temperature, allowing balancing without circuitry.
A Lithium cell has no self discharge...

Lithium cells voltage rises when fully charged.
Nimh cell voltage falls when fully charged.
That last bit means cell balancing is impractical.

There are a few temp sensors within the nimh battery, but thats it.

The relatively high failure rate of the battery was due to the software allowing the user to attempt to use the full 30Ah on every discharge.
If this were limited to 20Ah, 90% of the batteries that did fail, would not have.

New Lithium Vectrix has BMS though.

Matt

If this were limited to 20Ah, 90% of the batteries that did fail, would not have.

But imagine.. 90 kg of expesive NIMH battery to only get 20 Ah... only 2,5 kwh...

The potentially very high lifetime mileage is what makes NiMH interesting. Some of the original NiMH batteries will probably still be going strong when all Lithium conversions have approached their end of useful life.

If this were limited to 20Ah, 90% of the batteries that did fail, would not have.

But imagine.. 90 kg of expesive NIMH battery to only get 20 Ah... only 2,5 kwh...

well yes....That is the present maximum reliable usable capacity of an original Vectrix nimh battery

If you use more, it fails relatively quickly.

Use less, and it lasts a *really* long time.

One of the bikes I converted had done 27'000km on its original battery (albeit with a couple of cells replaced).
The range was still usable (as it still had above 20Ah capacity) but the owner wanted to go further.

Its the old, stay away from 100% and 0% trick to getting good service life.

Matt

If this were limited to 20Ah, 90% of the batteries that did fail, would not have.

But imagine.. 90 kg of expesive NIMH battery to only get 20 Ah... only 2,5 kwh...

well yes....That is the present maximum reliable usable capacity of an original Vectrix nimh battery

If you use more, it fails relatively quickly.

Use less, and it lasts a *really* long time.

One of the bikes I converted had done 27'000km on its original battery (albeit with a couple of cells replaced).
The range was still usable (as it still had above 20Ah capacity) but the owner wanted to go further.

Its the old, stay away from 100% and 0% trick to getting good service life.

Matt

In my case I´m still doing around 45 Km with one charge using less than 20 Ah.
Top Speed 70 Km/h 2/3 of the distance, 1/3 city riding. The revision this winter
will tell how healthy the cells are. Greetings Mike

If this were limited to 20Ah, 90% of the batteries that did fail, would not have.

But imagine.. 90 kg of expesive NIMH battery to only get 20 Ah... only 2,5 kwh...

well yes....That is the present maximum reliable usable capacity of an original Vectrix nimh battery

If you use more, it fails relatively quickly.

Use less, and it lasts a *really* long time.

One of the bikes I converted had done 27'000km on its original battery (albeit with a couple of cells replaced).
The range was still usable (as it still had above 20Ah capacity) but the owner wanted to go further.

Its the old, stay away from 100% and 0% trick to getting good service life.

Matt

In my case I´m still doing around 45 Km with one charge using less than 20 Ah.
Top Speed 70 Km/h 2/3 of the distance, 1/3 city riding. The revision this winter
will tell how healthy the cells are. Greetings Mike