Best way to sync charge of 12 volt battery bank over long distance?

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houser asked Sep 16, '19

Best way to sync charge of 12 volt battery bank over long distance?

Hello,

We have a small wind turbine that charges a small battery bank that is only used as a buffer for a 240 inverter that goes into a 240 cable about 70 meters and charges the main 12V battery bank there via a Victron Blue smart 10A charger.

The main bank is also charged via a Victron smart solar charger.

Both battery banks are about to be replaced so would like to know if there is a better way to do this, before we buy new batteries.

Q:

Can these two chargers sync via Blue tooth to optimize shared charging of the batteries?

Can the Blue Smart charger output be connected over the Battery smart shunt, as any load?

Many thanks for any hints on how to proceed!

smart solar set-up help Smart Battery Sense charge controller compatibility

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Answer 1 · 2019-09-16T20:41:24Z

Alistair Warburton answered · Sep 16, 2019 at 08:41 PM

Bluetooth is a poor plan, it isnt stable enough if it worked at all over that distance.

RS485 or an analouge signal, current preferably, is the way to go, Ethernet is also an option but will cost more.

What you need to do is control the charge base on the voltage of the small bank.

If the charger can be comunicated with you could do this dynamically, limiting the AC load.

That said you could also manage the charge as a duty cycle, simply turning it on or off.

A simple external PLC or DSP could easily handle both tasks with dynamic control being the best option whilst duty cycle control being by far the easiest to impliment.

If you went the latter route you wouldnt actually need and comunication as the inverter on the small bank could simply be turned on and off, based on battery voltage.

I am not suggesting you cycle the battery... If you measure the load when the inverter is on that will tell you what the charger at the other end is doing, but more importantly it will tell you what the 100% duty cycle load is. You will have a target load to aim for based on battery voltage so all you have to do then is calculate the duty cycle yiu require to achieve that as an average.

Depending on the size of your bank you would probably want a base frequency for the duty cycle of several minutes or even tens of minutes.

You would also want to set a minimum on and off time so that neither the inverter or charger is cycled too quickly. This would be best implemented by limiting the upper and lower limits of the duty cycle and forcing either 100% or 0% when the bounds are reached.

Victron may well have a product that can do either of the above but if not it wouldnt be hard to manage the stuff you have in this wy.

Hope this helps

Al

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houser commented · Sep 19, 2019 at 01:27 PM

Many thanks for that reply, Alistair Warburton.

Reg. bluetooth, I simply ment if possible using the built in syncing that has been mentioned should arrive this fall for some chargers. The two smart chargers (solar+ 240 Blue smart) would be right next to each other, so no issue with distance there.

Yes, we are looking at various forms of automation to achieve this better long term. Just trying to keep it as simple as possible for robustness.

Many thanks again!

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