5000W/ 48V water heater dump load element [RE-wrenches]

[Hugh Piggott]

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>Hi again
>just to be clear, my dump load is not 5kW. it is more
>like 1 or 2 kW.  The tristar I use is a TS60.  Has
>anyone tried to parallel two tristars to handle a 100
>amp load of a single 5kW heater?  I would think that
>both of them would fry.  First one tristar would take
>the whole 100 amps and fry its FETS then the second
>would do the same.

Yes you need to use two loads - one on each Tristar.  They may 
'fight' to an extent about whether they are in so called pwm (boost) 
or float mode.  But it should work well enough.

>
>  > The tristar lives, the Solar boost lives, the SW
>>  plus
>>  lives, but the batteries die in one to two years. I
>>  can never get the batteries to be charged correctly.
>  >

This is not normal.  I have had problems with engine driven charging 
via an SW or whatever because the Tristar does not know about this 
and dumps engine power, but this should not harm the battery, and 
there are various ways around that.

>  > They either get overcharged or undercharged.  It
>>  sweems as if the setting on the Solar boost,
>>  tristar,
>>  SW Plus drift constantly or change.   Some times the
>>  solar boost will sence overvoltage and cut out or
>>  other times the SW will be charging the battery and
>>  the tristar will be selling the power to the water
>>  heater then the space heater.  It seems to me the
>>  setting on the controllers are not accurate enough
>>  to
>  > play this game.

Settings will also be modified by battery temperature sensors and so 
on.  It is hard to prevent dumping of engine power just by using 
'voodoo set-points'.  And it will tend to risk inappropriate charging 
too.

You can use a relay to insert a diode drop into the Tristar sensing 
wires when there is engine power present, thus fooling it that the 
battery voltage is lower than it actually is.  If renewable energy 
input is very high when the engine is running then an SW will push 
this power into the AC circuits (displacing gen power) to prevent 
overcharge.  That's a nice way to limit voltage provided you have 
enough AC load.  I am not sure if an Outback would do this too.

There is no reason the set-points should drift or that the battery 
should suffer.

best
-- 
Hugh

Scoraig Wind Electric
http://www.scoraigwind.co.uk/


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