Since the EVtech list appears to be down, I'll post this here.
----- Original Message -----
From: "Al" <[email protected]>
To: <[email protected]>
Sent: Sunday, March 13, 2011 1:08 AM
Subject: solid state relays (again)
> It's been pretty quiet on the list so I thought I'd start some discussion.
> I am going to try a battery monitor/management system similar to Lee
> Hart's battery balancer.
> I am going to use solid state relays (mosfets) to switch between
> batteries.
>
> First problem is mosfet voltage rating. Higher voltages have higher on
> resistance and cost more. Instead of having all the "relays" connected to
> a common buss, I could break the pack into manageable pieces like 12 6V, 6
> 12V or 24 3V. I am planning on maximum 10A balancing current. Also using
> bidirectional TVS across each "relay". How much headroom should I have on
> the mosfets and TVS's? Should I double the worst case voltage and current?
> Should the TVS be rated just below the mosfet rating?
>
> With SS relays, I need to be darn sure that only the proper relays are
> energized, even small "glitches" could turn them on. Would an IC decoder
> be the best coice for this? I checked on Mouser and most of this "old
> school" logic is getting rare. The 4028 1 of 10 decoder that Lee uses
> looks like my best bet. Do they make a such a thing as a 1 of 16 decoder?
>
> BTW I am using photovoltaic drivers for the mosfets. These things are
> great, no need for an isolated gate drive. You can have a separate supply
> for the LED side that if killed would disable all relays.
>
> Check out these fuses that I will have on each line right at the battery
> terminals. They are rated 500V AC and DC! even in the higher amp range.
> They also have excellent interrupt ratings.
>
> http://www.littelfuse.com/data/en/Data_Sheets/Littelfuse_Fuse_505.pdf
>
> Enough for now, thanks for any comments.
>
> Al
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----- Original Message -----
From: "Al" <[email protected]>
To: <[email protected]>
Sent: Sunday, March 13, 2011 1:08 AM
Subject: solid state relays (again)
> It's been pretty quiet on the list so I thought I'd start some discussion.
> I am going to try a battery monitor/management system similar to Lee
> Hart's battery balancer.
> I am going to use solid state relays (mosfets) to switch between
> batteries.
>
> First problem is mosfet voltage rating. Higher voltages have higher on
> resistance and cost more. Instead of having all the "relays" connected to
> a common buss, I could break the pack into manageable pieces like 12 6V, 6
> 12V or 24 3V. I am planning on maximum 10A balancing current. Also using
> bidirectional TVS across each "relay". How much headroom should I have on
> the mosfets and TVS's? Should I double the worst case voltage and current?
> Should the TVS be rated just below the mosfet rating?
>
> With SS relays, I need to be darn sure that only the proper relays are
> energized, even small "glitches" could turn them on. Would an IC decoder
> be the best coice for this? I checked on Mouser and most of this "old
> school" logic is getting rare. The 4028 1 of 10 decoder that Lee uses
> looks like my best bet. Do they make a such a thing as a 1 of 16 decoder?
>
> BTW I am using photovoltaic drivers for the mosfets. These things are
> great, no need for an isolated gate drive. You can have a separate supply
> for the LED side that if killed would disable all relays.
>
> Check out these fuses that I will have on each line right at the battery
> terminals. They are rated 500V AC and DC! even in the higher amp range.
> They also have excellent interrupt ratings.
>
> http://www.littelfuse.com/data/en/Data_Sheets/Littelfuse_Fuse_505.pdf
>
> Enough for now, thanks for any comments.
>
> Al
_______________________________________________
| REPLYING: address your message to [email protected] only.
| Multiple-address or CCed messages may be rejected.
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| OPTIONS: http://lists.sjsu.edu/mailman/listinfo/ev