Giandel 1200 watt inverter spec

[John Frum]

That'd be the ideal thing, when ever applying DC to the inverter precharge it. You could put it across the breaker in that situation but only if you don't have any other loads connected at the time as they will try to run via the resistor and will also discharge the capacitors in the inverter once you remove the resistor (you could turn the breaker on while the resistor is still in place).

There is a better way. You'd have a 3 position switch in line with the breaker. The breaker goes before the switch. The three positions are off, pre-charge, on. The resistor goes permanently between the pre-charge and on positions, DC from the battery goes to the common terminal on the switch. The inverter goes to the on position. Then it's just a case of move switch to pre-charge position, wait a bit, move to on position and you are ready to turn the inverter on, when you leave rotate switch to off position (if ytou want to turn the inverter off that is)

You mean like this one https://diysolarforum.com/threads/giandel-1200-watt-inverter-spec.9653/post-104660 ?

 

[gnubie]

You and your fancy expensive pre-made answers, this is a DIY forum, I'm going to ignore it and do it myself!

 

[Mex Rider]

Thank you both and Gnubie, nice design and execution, will probably try to copy. But for what it's worth, none of this makes commercial or logical sense to me. I can understand pre-charging the capacitors upon installation of an inverter.... but every time you re-energize your system...don't capacitors hold their charge for a long time? and how could a company sell inverters that were not built to handle the DC load when it was turned on.... to me that is totally absurd. Do the owners manuals of high end inverters warn the owner that he or she needs to pre-charge their capacitors before applying current....???? How do all those old farts (me) function in their RV's with an inverter....what am I missing??

 

[gnubie]

Not connected to anything they will hold their charge for some time, but they are connected to something - the rest of the inverter, and good practice would have a bleed resistor across them should the inverter not draw them down for some reason. So each time you disconnect DC from the inverter they will discharge.

As far as damage goes, this is only really a problem if you do it a lot. If it's only occasionally, that's fine. It also tends to apply to the cheap end of the market, ie most of these high frequency inverters, since they use cheap capacitors. High end products use much better components so tend to stand up to repeated abuse much better.

It's not just the capacitors that take a hit. The switches / breakers do too. The good ones are built to take abuse, but they too will degrade with repeated high current hits. You may see youtube clips where people put beefy wires connected to inverters onto battery posts and there's a big splat and a spark. That actually blows a bit of metal off the battery terminal and lug on the cable. If you want an example, one of Will's youtube clips shows him connecting to 48V (?) and the resulting damage to the battery post. Quite a bite is taken out.

Think of all this like a car. You can drive it around in a normal fashion and get 100,000 miles out of it. Thrash it and you won't.

 

[Mex Rider]

Thanks Gnubie, that really puts it into perspective and may induce me to bump up to a Samlex or other higher end inverter. I don't think that drawing my batteries down to cutoff is a real issue, but I have to say going off and leaving the van for the day may have me shutting down the AC system, as I did on my cruising boats, but perhaps with all the breakers and fuses and my solar panels continuing to charge, the idle current of the inverter maybe a small issue. Until we see how we really live in the van it is a bit of a guess. On the boat I hardly used the inverter and it was only 1000 watts (Samlex) so it was off most of the time. I like your 3 way switch and will probably incorporate that when I can get the parts, very nice contribution to the forum... and thanks for all the advice and help. I try to give back on the Transit forum but here I only know enough to get in trouble

 

[Mex Rider]

Thanks Gnubie, that really puts it into perspective and may induce me to bump up to a Samlex or other higher end inverter. I don't think that drawing my batteries down to cutoff is a real issue, but I have to say going off and leaving the van for the day may have me shutting down the AC system, as I did on my cruising boats, but perhaps with all the breakers and fuses and my solar panels continuing to charge, the idle current of the inverter maybe a small issue. Until we see how we really live in the van it is a bit of a guess. On the boat I hardly used the inverter and it was only 1000 watts (Samlex) so it was off most of the time. I like your 3 way switch and will probably incorporate that when I can get the parts, very nice contribution to the forum... and thanks for all the advice and help. I try to give back on the Transit forum but here I only know enough to get in trouble

Well, Credit to Smooth Joey on the switch

 

[PriusFan]

I’ve been looking at this same inverter and now have the obvious question. What inverter should I get which will have a proper (higher) low voltage cutoff for lifepo4? (The problem identified in the original post.)

 

[John Frum]

I’ve been looking at this same inverter and now have the obvious question. What inverter should I get which will have a proper (higher) low voltage cutoff for lifepo4? (The problem identified in the original post.)

Configurable low voltage cutoff is a feature generally only found on inverter/chargers.
Because of my very peculiar usage model I have to use a discrete inverter.
I use this one https://www.donrowe.com/samlex-pst-1500-24-pure-sine-inverter-p/pst-1500-24.htm
controlled by one of these https://www.victronenergy.com/battery_protect/smart-battery-protect
The battery protect controls the inverter but is not in the high current path.