Solar, battery inverter outputs

[gunnadoo]

hi, i have a few questions outputs. my inverter is a [se32 24 V dc -to 240V ac] with4 outputs,and 1battery 24V + terminal. the manual states these are 'open collector transistors which can sink 100Ma each or 25Ma if connecting a contactor directly.max voltage on outputs is 60volts dc'
1- can i connect a transistor/darlington to output, to drive a relay
2- if so , how ? [probably a stupid ?, but i dont want to damage these outputs ]
3 - would i be better off using small relay to drive a bigger relay. [starts getting a bit messy, for me anyway]
4 - whats the difference between ,say, a relay/light etc Ma, and a contactor Ma.[as above]. 100Ma -vs 25Ma.i thought an amp is an amp
5-what exactly does 'outputs is 60 V max' mean , when the bat+ terminal is 24V [another silly ? ]
thanks in advance for any replies...dennis..

 

[kellys_eye]

What do you want to control?

You can use SSRs (solid state relay) which would connect directly and control many 10's of amps on the AC side.

 

[gunnadoo]

i would like to control a pump [ac 500w], turn it off when tank is full, and maybe use another output to turn it on if i can figure out a low level switch . also switch solar power [ dc ,up to 80A] to other loads when primary batteries are full.i have read up a bit on ssr,s and there main fault is they short cirquit when they fail. how reliable are they?

 

[kellys_eye]

If you use a reliable supplier for your SSR (and one that is correctly rated) there's no reason why it should fail - besides, there's nothing stopping a relay from failing 'short' (welded contacts) either. Your reasoning behind not using an SSR aren't really valid.

For an 80A DC switched load you would be better off with a suitable contactor - they can be found with operating coil voltages from 12V DC to 240V AC (or more) but you'd have to check their data sheet to see if the coil current is within the capability of your open collector output.

You would connect the coil to the 'open collector' and the other side of the coil to the required supply voltage (MAX 60v according to your data) - the voltage chosen to match the contactor coil of course.

 

[gunnadoo]

thanks k e, for replies, and advice on ssr, i will try one [any good brands ?]. i doubt i will find a contactor that draws< 25Ma,which is why i was thinking along the lines of using a bjt to drive relay / contactor , but obviously, i can't do that . my reasoning for using a very low power device to drive a relay is my water tank is 70 metres away and i have some very light telco wire, which i am not sure would carry [40Ma/24v [my pump relay] that far. by the sound of your 1st reply, these ssr's have "high gain" and will solve pump problem. without dragging this thread on and wasting your time, i will do some more research on ssr's and see if they make something with a very minimal dc current draw and switch 3A ac. i can hear the readers saying, 'just buy heavier wire'. well, i have telco wire [free], 2-i'm in a money drought atm .also thought of pressure switches, but on gravity feed approx 10psi full/8psi empty.
thanks again....dennis

 

[kellys_eye]

All brands are good - just source them from a reliable supplier (cheap Chinese knock-offs may be fine but you get a greater level of security buying from the big names).

If you (and I'm sure you do) have power at the well/pump then use the telco wiring to send a DC supply to a relay at the well. This can be buffered - as you originally surmised - by a transistor but pay due regard to line pick-up/interference etc to avoid spurious operation.

 

[gunnadoo]

just one last ? if i may. i found some mini ssr's [omrons] 7Ma max on net, should do job. would 2 paralleled on inputs. be ok with inverter output. i just thought if i ran the load through ssr's in series it should be failsafe should one fail. overcautious yes, but i dont want to flatten batteries,pump well dry,or burn out pump,or stock run out of water, etc if i am away for a bit.i will upload small pic [hopefully]. might explain things better than me. just a yes or no for answer will suffice..over and out........regards..dennis...

 

[kellys_eye]

Yes