smart inverter trouble due to poor batteries?

[robertp]

Can someone help me with this riddle?

I have upgraded the inverter/charger recently. It is a smart machine and it refuses duty. Its charger attempts to click in every second or so but fails generally. Every minute or so it hangs on for a few seconds, and a few times it has hung on and charged for about 10 minutes before flicking out of it again. The inverter runs for about 10 minutes before stopping. The display indicates battery < 60%.

The battery bank is a set of 6 x 2V series to make 12V. Before the new inverter arrived, we used another inverter (more basic) without fail (we upgraded because it had no AC charging capability). The bank could be fully charged in the late afternoon (indicating 12,5-13 V) but after a night of only running a lightbulb and modem, it drops away to below 12V. Similarly, after a good boost with a DC charger (160A) it shows good voltage, but has no 'oomph'. Today it ran until the sun disappeared and then gave up, while the batteries still showed 12,5
V on the controller. Oh, and the inverter indicates also that the incoming power is 0-2V!

The system has been underpowered and is 8 years old. My theory is that the batteries are pretty much stuffed and show a surface charge but cannot hold power. The hydrometer confirms this. They may be sulphated sand need a good kick. The new inverter must sense this and shuts off to protect the batteries. Any thoughts on this theory please? Has someone had this problem with their (new) inverter?

(BTW, this is not the system I discuss in another thread. We're renting an off-grid shed while setting up a new off grid system nearby. This problem refers to the rented system).

[vtmaps]

The bank could be fully charged in the late afternoon (indicating 12,5-13 V)
<snip>
My theory is that the batteries are pretty much stuffed and show a surface charge but cannot hold power. The hydrometer confirms this. They may be sulphated

Your theory sounds correct.  It's hard to argue with an hydrmeter.

The voltage in the late afternoon... is that a resting voltage?   How high a voltage does the battery get to while being charged?  What are the charge parameters?

--vtMaps

[boB]

Are you charging from a generator there (I assume)  ?

Can you try turning down the charging current some on that inverter/charger ?   Maybe it is a power factor
problem into the charger ?   This is a Powerstar inverter charger ?  Not too familiar with that but I've hear
of it before.

Then again, you mention the charger says it see 2 volts on the input.  Is this all the time or just when it
turns itself off ?

What kind of generator and how large, power wise ?

[robertp]

Thanks for your responses. This particular inverter/charger is going back to the supplier.

I am learning that not all inverters are created equally. Also that some traders are fairly casual with the claims they make about their products, and are proving to be ignorant about their wares when quizzed. I recently bought two inverters (for two different systems/locations) and I cannot afford to run either of them. I should mention that I've not bought the top models, as we're losing losing one of those every two years on average due to lightning. I didn't buy the cheapest ones either.

I don't think I should single out any particular manufacturer, but have some hard learned lessons for members who are looking to buy one.

Try to find out the idle consumption. I have a machine that consumes 240W when working, and 50W when idling in 'power-saver' mode. When powering a single 11 watt light bulb, the meter goes to 251W! Who can afford that? The idle power consumption is directly related to the max. output, yet some list a generic idle current across their inverter range, giving an incorrect impression.

Find out if the power saver mode can be turned off. One of mine can, the other cannot. On the latter machine this means that I need to run a minimum load of 200W or the machine switches off, making a mockery of our frugal off-grid set-up and management.

Make sure that the fan is thermostatically controlled, and is not going all the time, making unnecessary noise and using power (neither of mine are).

I guess this is a problem in our game, especially when living in rural, out-of-the-way places: that the components of our systems are not found on the shelf of the local store to check out, but often must be sourced remotely, trusting the trader's advice. With prices varying wildly, who can you trust?  I'm going to have to buy more inverters to complement the 'big boys' and am doing a lot of homework this time around.

My 'powerhouse' (shed) is 30 m away from my future off-grid home, and I am considering running triple cables into the house to keep running and idle currents low when I can: one 24V DC to power lights and perhaps a small load (computer) via a small inverter(500W); one 240V AC cable to general power points supplied by a 2kW inverter on stand-by, and a few power points in house and workshop to power hungry tools fed from a hefty cable powered by a hefty 6kW inverter (remotely/manually controlled).

Anyone gone to that sort of trouble?

[vtmaps]

My 'powerhouse' (shed) is 30 m away from my future off-grid home, and I am considering running triple cables into the house to keep running and idle currents low when I can: one 24V DC to power lights and perhaps a small load (computer) via a small inverter(500W); one 240V AC cable to general power points supplied by a 2kW inverter on stand-by, and a few power points in house and workshop to power hungry tools fed from a hefty cable powered by a hefty 6kW inverter (remotely/manually controlled).

Anyone gone to that sort of trouble?

Two inverter systems are not uncommon...  I just wrote about it a few hours ago here:
http://forum.solar-electric.com/showthread.php?p=193013#post193013

Why run 24 v DC to your house?  Just put the small inverter out in your power shed with the other stuff.  If you try to transmit 500 watts at 24 volts over a 30 m distance you would need 4 awg copper cable to limit your voltage drop to 4.4% and limit your power loss in the cable to 22 watts.

Most full featured inverters have remote monitoring and control options.  AC power cables can cause interference with the low voltage monitoring and control cables, so be sure to put in a separate conduit between your shed and house for monitoring and control cables.  If you do run DC to your house, it can run with the monitor & control cables.

--vtMaps

[zoneblue]

It was one of the first lessons i learnt off grid: with inverters you get what you pay for.

If you are serious, start saving now, slap the cash down for an outback/magnum/schneider. Messing about with anything less is just playing around. There are one or two reasonable quality cheaper inverters but they are only a bit cheaper, eg samlex. But you lose the superior reliability,  the programability, surge capability, the charger etc. So whats the point?

If it aint heavy you dont want it.

As to two inverters, i also will probably go that route. We use a 1100W inverter with 10W idle for day to day, and plan to add an outback for the workshop, hotwater and the vacuum. The outback isnt too bad at 20W idle.  SW is a reasonably priced inverter but the idle is around 40W.

Some inverters like our 1100W can stack. You can put several smaller inverters in parallel, and the interconnnecting device only turns on as many as it needs. In the case of the Steca system, that means you could potentially have a 4.4KW inverter with 10W idle. But for the crazy german price tag, that is .

[tecnodave]

I am doing the dual inverter routine for idle power savings. I use a high frequency sine wave type for small loads and a hybird high/low frequency sine wave type like the outback and magnum for big loads.  This has worked very well for me as a lot of my power is used at DC and my AC loads are moderate mostly and I need a clean waveshape ,but there are times that a big inverter has its place.

I use a Exeltech 1100 watt for my household use and a Cotek SK 1500 watt for shop both are low idle draw sine wave units, for shop and house heavy use I use Dynamote Brutus inverters that are similar in design to the outback and magnum  very heavy low frequency transformer based design but a bit much idle draw at 96 watts, only run with big load when needed, cheaper than dinosaurs in the Onan

td

[robertp]

I am considering to run the 24V DC into the house to run 24V DC LED lighting. When the inverter fails for one reason or other (lightning has been an issue for us and our neighbours) we'd still have lights at least and could run a cheerful 300W inverter to power other light loads such as the internet modem and computers. Repairs and shipping back and forth have taken weeks in the past.

Stacking the inverters is a good idea that I'll look into. Like other folks have reported, running a conventional fridge and freezer and the need to have the power on tap to should they both decide to start up at the same time is dictating the minimum capacity needed. I should also start saving for more frugal DC freezer and fridge… (Why doesn't everyone buy one of those? -  the price would come down and everyone wins)

[vtmaps]

I am considering to run the 24V DC into the house to run 24V DC LED lighting. When the inverter fails for one reason or other (lightning has been an issue for us and our neighbours) we'd still have lights at least and could run a cheerful 300W inverter to power other light loads such as the internet modem and computers.

You will have better selection and prices on 120 volt bulbs than 24 volt bulbs.  Also, your 24 volts will vary from 21 to 31 volts depending upon where you are in the charge/discharge cycle.  Most DC lighting does not appreciate such variation.  Since you have a 300 watt inverter as backup if your big inverter fails, you ought to be able to run some LED bulbs.

--vtMaps