I have run my batteries down to 11.7 volts twice. Now I think I might have an idea how to stop this from happening again but I wanted to ask you all to see if you have a better idea, so here it is. My charge controller has a output load shut off that I can set the low voltage shut off set point I can't use the output load from the controller it just doesn't have enough amps. Now my idea is to buy a car starter solenoid relay to connect split my positive wire from the batteries to the inverter. I can use the output load of the controller to hold the solenoid closed and set the load disconnect at 12 or 11.9 volts so the load turns off opening the solenoid relay disconnecting the batteries. I think that will kill the controller too. You think it will turn on again when the sun comes out? Just an idea.

Views: 607

Reply to This

Replies to This Discussion


    A few problems here! First a car solenoid is meant for short duration use and at a lower voltage, due to the starters heavy draw. There is a switch that looks like an old ford solenoid that is meant for continues duty, they all however draw a lot! The basic idea is good just not your choice in how, my opinion not meant to insult.

   If you ran all your load 120 volts off your inverter and have a good inverter this is already a built in feature. The good puresine wave inverters nearly all have a low supply voltage shut down as a built in feature.

   Relays and bigger electric trip switches had there place but draw a lot for what your up to. A better start would be a control firing an SCR, which basically is a solid state switch. They are used in electric forklifts, and a 1000 other places! and can be big enough to easily handle these loads and require far less to operate.

   OR! to keep it simple you could use the 120 off the inverter to run the relay coil holding the 12 volts supply power on. If your 12 volt load comes after the relay when the inverter shuts down it will drop the 12 volts to. You would need a start switch to reset this after the low voltage dropped the relay.  

I hear yeah no offense taken. My inverter does shutdown automatic at 10.7 volts. I think the batteries are really dead by then LOL. For now I will just pay attention to the volts maybe disconnect the house fan and tell the wife it broke hahahaha



   Here in the woods I live with a short left handed woman and we have bear, not sure which is the order!

   Our problem is I've been retired a fair while. I can tell you several ways to do this,, with old time technology thats going to draw more then we want. We need some one how works with newer solid state controls this can be done and done easily I'm just to far out to no whats out there today! Or go with a bigger system so the looses aren't as big a deal? I'll keep checking around and if I come up with an answer I'll pass it on to ya, I see my boy on weekends, he may be up on this one!


Thanks I'm going to get two more batteries in a couple weeks I just keep buying them two at a time I figure I have 4 now when I have my rack flied with 12 batteries if we leave the fan on one night it won't be a big deal since I have 880 amp hours two barriers take me to 1316 amp hours and all 12 put me at 2632 amp hours.


I'm old and may be senile, But! I question your battery math here. What are you using for batteries?

Maybe this will help. I have 10 deep cycle golf cart batteries, 6 volt! They are 232 amp hrs or 122 minutes at 75 amp, or 474 minutes at 25 amp. My reserve battery bank is 1160 amp hour. All in an ideal world!

The ratings go out further in time as the amp draw goes down due to heat and chemical efferences.   

Lets work with 10 as it makes quick easy math! If I take two 6 volt 100 amp hour batteries and run them plus to plus, minus to minus, parallel. We now have 6 volts at 200 amp hours, or 1200 watt hours.

If we tie the plus of one to the minus of the other, series, we will have 12 volts at 100 amp hours, or 1200 watt hours. One of our batteries in this case can only delievers 600 amp hours so two can only deliever twice that, regardless of hook up. Watts is the Amps times the Volts.

You may have batteries that big, hope so! But, I suspect your math is wrong and that will haunt you in figuring run time and general conditions.

Let us no what your using for batteries, in ratings and we can see, you may be right, I was wrong once?

I'm running 6 volt 232 amp barriers running them in series parallel. I have 4 batteries. Two in series, two get the 12 volts, then I got em in parallel if you know what I mean.. I thought putting them in series would double the amp's just like it does the volts? My math is wrong my first 2 batteries are 208amph my second 2 are 232amph so how do I calculate the amp hours the right way so I can figure out how long they will last pulling 300 watts.

I think 208 plus 232 equals ..... 208. 

Really? Omg I'm bumming I need 1000 batteries lol

I think I am confused, maybe it's 416. Series to parallel, so double the lowest number, then.....OK. bring in the smart guys.


If a lower capicity battery is in series with bigger, the smallest battery becomes the bank rating, a 100 amp in series with a 200 amp is only 100 amp! In parallel they all just add up! 100 and a 200 and a 50 becomes 350.

  So, the 2, 232's in series are 232 at 12 volts, the 208's become 208 at 12 volts. When we join them in parallel we become 12 volts at 450. If you had joind a 208 and a 232 you would have 208 twice or be 416, you did do the preferable hook up!

   Mark 450 amp is what your running!

   When your tieing batteries of different capacitys together in parallel the difference isn't a big factor as long as we stay reasonably close in size. In series however it becomes a very limiting factor and should be avoided. Also, Ideally we would like all the batteries to be purchased at the same time, and be the same size. The reason for this is an old battery that is dieing can discharge the others effecting the operation of the entire bank. Then before they go in service a slow charge to equalize the bank so at start-up all is equal and ready.

   Watch out for that Ray fellow, he's as crazy as me! Hope he has a sense of humor!


@W.R.  ....sense of humor? Of course I do, about as much of a sense of humor as any forum moderator can have. If you saw what I deleted in a day you'd think this was like being a junior high principal. And I love every minute of it!

Back to the battery thing. Over the years I have grown to detest mixing old batteries with new so much that I would rather just create separate banks and switch between them then to ruin new batteries. But that's just me.  :-]

Mr Ray

Sounds like the best of advise, I over the years have spent many hours on the road to tell someone not to mix and match! I also would advise readers that the batteries are in fact the heart of your solar gear and it's not the place to cut corners as a truely good set of batteries will last a long time if all is right, or die in a hurry if its not!


© 2016   Created by Renewable Ray.   Powered by

Badges  |  Report an Issue  |  Terms of Service