Just need amp limiting BMS - any cheap suggestions?

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Piers
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Just need amp limiting BMS - any cheap suggestions?

Hi,

I have had endless problems with my 60v 2500w bike set up. Essentially the amperage seems too high for SLA to last beyond a few months.

So I went for Vpower - from Hong Kong via ebay. I thought that the guarantee inherent with ebay would be okay - but slight problems are causing problems.

I installed a switch rated at 50 amps and it trips after a few seconds on open throttle. The batteries are only rated at 40 amps. Is the BMS faulty? Should I get a new one? Are there any cheap ones?

Thanks

Piers

amberwolf
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Re: Just need amp limiting BMS - any cheap suggestions?

Rather than a BMS to limit current, why not use something like the Cycle Analyst
http://www.ebikes.ca/drainbrain.shtml
to do it? What it does if current limit is reached is then limit the throttle if higher demands are made than the limit allows.

The manual for it explains how it works:
http://www.ebikes.ca/drainbrain/CycleAnalyst_Manual_Vers21.pdf

--
Michael Elliott
Cybernetic Necromancers, Discorporated
Phoenix, AZ
Watch me build an electric-assisted recumbent bike from recycled junk:
http://electricle.blogspot.com

Piers
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Joined: Tuesday, June 9, 2009 - 07:12
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Re: Just need amp limiting BMS - any cheap suggestions?

Thanks for the suggestion. That seems to be about the only thing around.

cell_man
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Re: Just need amp limiting BMS - any cheap suggestions?

You could also modify your controller to reduce the current being pulled. It will have shunt resisistor inside which can be partially cut and this will trick the controller into thinking it is delivering more current than it is and back off the power. The Cycle Analyst can do something very similar but does need to be connected into your controller to do this and will likely need some new connections before this will function. The stand alone unit will not current limit, only display data.

A BMS does not limit current, it just trips when it's limits are exceeded or the cells capabilities are exceeded, ie. the cell voltage is pulled below the acceptable limit. Big power e bike setups need good quality high C batteries or very big low C batteries to function acceptably. The makers max current is probably already higher than you should really be running the battery if you want it to last.

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