I have a Samlex 2000 watt Pure Sine inverter that has a LVD @ 10.5 volts. Why? That is a completely dead battery. Who designed it this way?

Anyway, I am looking at the "Battery Brain" heavy duty (500amp/2000amp surge) which will disconnect the battery completely when it drops to 11.7 volts. Is this purchase worth the money? or are there better options out there to disconnect the batteries (LVD)at a higher voltage. I would like it to disconnect at 12.5 personally, but the folks at Alte told me good luck in my search. This seems like such a no brainer as many inverters out there cut off at approximately 10.5 volts. Perhaps someone has a suggestion.......besides ditching the $1000.00 Samlex and getting a $2000.00 new inverter....out of the question.

Internal resistance would have an effect on output voltage. A battery under load would have a lower voltage.

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Making the world a better place just makes sense.

A battery under load at 12.5 volts is a fully charged battery and then some.

SOC voltages only apply to a battery that is disconnected and allowed to rest for several hours. SOC voltages mean nothing when the battery is under load or being charged.

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Dereck, PE, MSEE
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having a inverter that stopped working at 12.5 v means it would hardly ever function. a fully charged batery has about 13.3 v in it but under heavy load that could easily drop to 12.5v. under normal circumstances the battery would revert to a higher figure say 12.8v when the load removed.providing that the very heavy load was a start up load and not a constant current load for long duration.
Inverters have a buzzer that sounds at 11v at this point you should be turning off the load on the inverter. As 10.5 v is certainly not good for the battery .But just about all inverters cut out at 10.5v.
I believe an external low voltage cutout set to 11v would be a good idea, anything higher would reduce the time you could run it on a battery if heavy start up loads.

ok, I see the difference......I think. So what do you think about the 11.7 "Battery Brain" cut off level? The voltage will probably be at 12volt with no load after several hours (if I understand the last couple threads right.) This voltage is still is a battery bank that has been taken to half of its capacity.

I guess the reason I want to buy this item is to preserve the life of my battery bank. I want the cut off to be automatic with no supervision because the old lady has real bad hearing and I am quite sure the batteries will be drawn to the 10.5 volts in my absense. It will be hard to comprehend the differnce of battery power compared to grid power. All appearances inside the cabin to the untrained solar savey eye will appear to be a normal grid tied home, but with a sever choke collar on it that she may not understand.

So no one gave there opinion on the "Battery Brain". Is this a solar compatible item? It has a wire on it that keeps a car from turning off in motion (good idea..lol) and another wire that connects the "BB" to the negative terminal and I do not know if it will interfere with a solar application...ie my MPPT charge controller or my 120v AC battery charger I have hooked up to my genny.

Thanks for the other imput though.

11.7 v is still too high for reasons already explained. the best compromise is a 11.00v cut off. I know nothing of that item the battery brain. so cant help with that

http://www.batterybrain.com/HD_manual.pdf. If anyone is interested read the specs and let me know. Before I buy it I would like to know if it will work in a solar application.

I bought the "Battery Brain" Heavy Duty. I ran a test with a 1500 watt load on my El Cheapo inverter. The "Brain" tripped at 11.87 volts under load. The manual says it should trip at 11.7. The volts immediately went to 12.41v once the load was shut off. I reset it thinking it should go lower than 11.87v as the manual states 11.7 should trip the "Brain", but the "Brain" again tripped at 11.87v. I kept the volt meter on the terminals and watched as the volts increased from 12.41 over the next couple of seconds under no load. I am not sure what the true voltage on the battery bank will be once the batteries settle, but I would assume it will never level out over 80%. The 12.45v read on my charger measured 70% of my banks capacity when I hooded up my charger a minute or two later. I am happy with that number. No more than a 30% depth of charge was what I was aiming for anyway so that will extend the life of my batteries.

The only thing that concerned me was that the "Brain" tripped about 3 or 4 minutes into the test. The volt meter (on the terminals) measured 11.99v under load. Don't know what that unexpected trip was all about. The "Brain" ran fine for the duration of the test after that initial hicup until it tripped at 11.87v. I guess my "Brain" has a mind of its own.

Does anyone think I should return the "Brain" due to a defect because of the faulty tripping behavior..ie tripping unexepectedly, and tripping at a higher than claimed voltage, or should I just stick with it and give it a couple more tests? Perhaps the batteries were surging or whatever the correct term is?

I have been trying to tell you now many times that the battery is going to trip out many times even if almost full,, You will find the claimed voltage cut out setting of 11.7v is only accurate to mabe + or - 2% it very hard to manufacture something like that with a much closer accuracy. its not a lab certified item. temperature alone can make a 1% difference. A slightly imperfect conection can also give a slight error.
That is why I said 11.7 is just too high for everyday use
Another thing where was your your voltage meter calibrated and when was that done. and at what temperature was it at when the calibration was done??

Voltage meter is pretty much new out of the box. So its never been calibrated?
My test was over a 25 minute time period and the ambient air temperature did not change. Do you mean battery temperture? I did not measure that and have no way to measure that temperature right now.

The brain did not have a heavy start up surge that caused the trip. It was already running with the one 1500w load on it for about three minutes.

If it will trip all over the place at any ole voltage it feels like on a constant load, at a constant room temperature, than yes, I will have to take it back. But if it trips at 11.87v consistently with all things being equal, I am good with that number. What I never made clear in this thread, that this was just a test of my equipment, not how my system is going to be utilized in my cabin. My load (cabin) is very minimal. My system is very minimal 300w solar panels and 450ah 12v system pushing a 2000w inverter. I am not trying to power an entire full time residence.