DC Contactor to disconnect charger from battery bank (SBMS0)

104 views
Skip to first unread message

Morgan Varaine

unread,
Apr 23, 2021, 8:58:26 PMApr 23
to electrodacus
Hi,

The solar charger (older Outback MPPT 60A) I'm looking at using for a project doesn't support any form of remote on/off operation. Would it be safe to use a DC Contactor to disconnect and reconnect the charger as required? I've got some EV DC Contactor units (https://na.industrial.panasonic.com/products/relays-contactors/mechanical-power-relays/lineup/automotive/series/2800/model/2817) that I am hoping would be able to do the job. It would require something else to drive this from the SBMS0 (relay).

Or should I just use a properly spec'd SSR?

Cheers,
Morgan

Will OBrien

unread,
Apr 23, 2021, 9:01:03 PMApr 23
to electrodacus
I think you could just use a DSSR0 to provide a disconnect the PV input to the outback.

Morgan Varaine

unread,
Apr 23, 2021, 9:05:31 PMApr 23
to electrodacus
The 'PV' input is actually a pelton wheel, and I'm not sure the DSSR0 would handle that properly. Although the DSSR0 with diversion would be handy in this case to heat up water when batteries are charged.

Dacian Todea

unread,
Apr 23, 2021, 11:46:44 PMApr 23
to electrodacus
Morgan,

Your solar charger was likely not designed to handle disconnecting battery from it while PV or other source is connected to input.
You may want to disconnect the input and leave the MPPT connected to battery or actually much better stop the water flow to that pelton wheel.

Morgan Varaine

unread,
Apr 24, 2021, 1:08:05 AMApr 24
to electrodacus
@Dacian, very true, I don't think it would like that...

We've been playing with the Hydro today, changing nozzle sizes and spacing out the rotor trying to get the voltages in the correct range. This Hydro setup is right on the marginal side of things so not getting huge amount of power in any case.

With a 10.5mm nozzle and spacers we've got the voltages down to 68v open circuit and 26-27v under load at 10.5A. 270-280W is what we can expect with the current size pipe, head, and friction losses inherent in the current setup. Static pressure is 62 Psi and Dynamic is not 44.5 Psi.

We started with a 9.5mm nozzle which was only giving 23v under load at 11.5A max. So a much needed improvement in any case.

Will the DSSR0s handle that voltage range? I see that the spec sheet says 51V max PV input.

We could look at spacing the rotor out to further reduce the open circuit voltage, but this would also reduce the max current.

Cheers,
Morgan

Dacian Todea

unread,
Apr 24, 2021, 12:03:45 PMApr 24
to electrodacus
Morgan,

You can clamp the voltage using a 60 cell PV panel then voltage will not exceed 45V. It can be a used 60 cell panel no need to be new and that can handle easy 15 to 20A so more than what your hydro can deliver.

Morgan Varaine

unread,
Apr 24, 2021, 5:03:16 PMApr 24
to electrodacus
Interesting, never come across voltage clamping before. Would this meaning putting a solar panel in parallel to the hydro? I'll do more reading! Thank you Dacian, this might also work for when we look at increasing the pipe diameter to get more oomph.

Cheers
Morgan

Dacian Todea

unread,
Apr 24, 2021, 6:00:34 PMApr 24
to electrodacus
Morgan,

The typical 60 cell panel made with 6" cells can clamp up to 20A and clamping voltage will depend on current and panel temperature but it will be around 40 to 45V.  Of course the panel will need to be indoors or covered so there is no sunlight. If you want to also use the panel then max clamping current can be just 10A as panel can also produce 10A in full sun.
You can not scale this by adding more solar panels in parallel it only works with one. To scale you will want to have multiple generators under 10 or 20A depending on where you install the panel. Panel will of course dissipate the energy as heat.

Reply all
Reply to author
Forward
0 new messages