24 volt inverter on 48 volt battery bank

[reprepper]

OK, I hope I can explain why I am even asking this.

I have 12 each 300 watt panels. 2 each classics and 32 each 6volt golf cart batteries and a 2400 watt pure sine 24 volt inverter. All works great and is designed for use as an off grid system. This system runs everything except my a/c, dryer, and water heater. Occasionally I switch to shore power to let the batteries get a good charge and stabilize.

This past summer I had a huge pulse from a lightning strike take out my two classics, a tv, my modem and a switch, my wireless broadband antenna, a multimeter in my work shop as well a couple of cell phones and numerous other small items. It was a doozy and scared the heck out of my wife and daughter, I wasn't home. So I sent the classics off to midnite for repair which wasn't too bad. That is all fine when the world is running the way it is supposed to. But I was thinking to myself, what if something like this happened after shtf which is why I have this system. I have a contingency plan to be able to direct wire the panels through a 400 amp relay controlled by a cheap controller that I keep in my faraday cage. That is just in case. By the way, everything in the faraday cage was unharmed by the pulse. The multimeter was on top of the faraday cage, It was toasted.

To maximize the 12 solar panels for a 24 volt system I need 2 classics, but If I had to, I could configure the battery bank to a 48 volt system and be able to maximize the 12 solar panels with just one classic. But then I would have to connect the inverter to the middle of the battery bank at 24 volts.

What effect will this have on the battery bank? The load batteries would still be fed and stabilized by the rest of the bank, wouldn't it? Will it put extra stress on or unbalance the battery bank.

Tell me what the bad effects on my battery bank are going to be if I had to do this. Again, this is just for my knowledge if this situation were to ever arise. I have no plan to change the current configuration of my system at this point. Actually I was thinking about putting an extra classic in my faraday cage as well as an extra 48 volt inverter, but just don't have the funds at this point. I just want to know what my options would be in a bad situation.

Thanks for any input anybody would like to give.

[mike90045]

You have to do manual swapping from one bank of 24v to the other bank. 4x a day !!  Otherwise, you discharge half the battery bank, the other half is full and the charge controller gets really confused and the batteries die.
It becomes incumbent on you to monitor the 2 halfs of the battery bank, and swap the inverter to the other bank often enough to keep the batteries balanced.
Or buy a spare 48V inverter.  That's what I would do.

[boB]

First of all, I think it is great news that the stuff inside the Faraday cage was un-harmed !  Theory triumphs again !

I think I see why you want to do this... You would like to CHARGE the batteries in the 48V mode but
Dis-Charge the bank in 24 volts.

You definitely do not want to discharge the 48V string tapped in the middle.  This will unbalance and
possibly harm the batteries. BUT, what you CAN do is to have a set of switches connected such that
they are in series one way (48V) and  in parallel the other way (24V) and also to make sure
that the 24V inverter can not run in the 48V mode.  This would keep the batteries evenly charged
and discharged.

Why is it now that you can't just get a 48V inverter ?   Anyway, you could certainly switch it
one way and then the other.

boB

[reprepper]

Why is it now that you can't just get a 48V inverter ?

boB

MMMMMOOOOOOONNNNEEEYYYYYY!

I agree, a new 48 volt inverter is the best solution. This is also what I told my wife right before she offered to lend me her lipstick to go stand on the corner to raise the money for my new 48 volt inverter.

I will work on it. Thanks for the input and explanations.

[Westbranch]

spend what you can now on more protection ie a bigger Faraday cage, then buy another inverter...

ADD: PS I think 24 V redundant equipment would be better than 48...  especially if you are lightning prone...

hth

[Halfcrazy]

Yeah the issue with EMPs of any origin that I see is that no matter how good you are at grounding and Faraday cages etc if its wired up and running it is prone. The real answer is spare stuff unwired in a double Faraday cage. Now that said that is Money and as stated if you are like me the Lipstick wont help me on the corner 

If I where in your shoes at the moment I would rewire the battery for 24vdc (Not ideal as you will have 8 strings of batteries but if you are very careful and make all cables the same length to some solid + and - bus bars it should be manageable) And reset the Classics. Now this may leave the Classics way over loaded Wattage wise but that should be ok on a temporary basis. Then I would work towards a new 48 inverter and some spare chargers. Take the 24v inverter and a spare charger or 2 and put them in a very robust dual Faraday cage.

Feel free to email or call Roy or I at Midnite if you want to discuss any of this more indepth.

Ryan