Inherited a mess?

Gino · September 2013

Hey all, Justed moved into the Off-Grid house, the solar here is a total mess, and it seems like nobody has done any maintenance on it in quite a while.
I could really use a few tips on getting things back in order.. There are some red-flags I see, but I'm a novice so would love some more input.
We are as a house of course on the broke side.. so hopefully I can fix things on the cheap...

Here is the setup

12x 2V - Panasonic 1040Ah Batteries (MSE 1040) in 2 series of 6, for 12V.
Xantrex C35 Charge Controller

All Solar PV is in Parallel right now...
4x 150W Panels with 20Voc = 2x300W at 20V
1x Mystery Panel, giving out 20Voc (different brand)
3x mystery Panels, Also giving out 20Voc slightly larger than my 150W panels... (but no labeling)
1x Wagen 5000W Pure Sine Inverter
No generator

If i'm generous and put every panel at 150W thats 9x150W=1350W
so 1350W / 20V = 67.5AMPS!

I have no shunt to measure amps, but I think its safe to assume we are well above 35Amps if all panels are operating correctly..
however the charge controller never shows over-amperage warning light.. or anything... the charging lite just blinks.. thats it..

Do you think I need a larger charge controller??

Things I'm thinking of doing, but really not sure....
*Reconfigure all panels for 40V charging voltage to bring down amps..
*maybe get rid of some of these mystery panels that don't match each other..
*Test batteries for dead cells

The batteries rarely get above 12.0V on a sunny day, usually run in the 11.2-11.9 range.. after a full days charge!

Any tips or help.. really want to get this up to the rated 13.5 full charge for that battery bank.

It is possible that since those batteries are used maybe some are bad?? not sure, i'm going to test it soon, just haven't done that yet.

mike95490 · September 2013

Re: Inherited a mess?

You are right. you have a mess on your hands. how old are the batteries ? more than 5 years old, they may be at end of life, and with that low voltage, in danger of being destroyed. Switch off all the loads you can to let them charge up.

You really need a generator to get them charged. And with winter & short days coming, solar will not do it alone.

And sadly, a high power, 12V system is not nearly as efficient as converting it to 48V.
2000A @ 12V = 24000wh At 48v, that's only 500ah for the same power. Could do it closely with 8 batteries
But there are prices to pay for new inverter, controller, panel re-wires..

Do you have any idea what your loads are ?

YehoshuaAgapao · September 2013

Re: Inherited a mess?

I assume all panels re connected paralell due to the charge controller being PWM. I'm guessing the panels have a Imp of 8 amps @ STC. 8 panels times 8 amps is 64 volts (64 amps not volts, niel). This is assuming you get full STC output which you usually don't. Imp @ NOCT is probably 6.5 amps, times 8 is 52 amps. Your charge controller is probably overloading only on the colder days, if at all. PWM controllers do not have any voltage conversion ability, so the amperage specs matter more than the wattage specs for these controllers. If you had a MPPT controller, you would be dealing with more like 80+ amps.

The PV is very light for that inverter and battery bank. And if you have more than bare bones power usage, you will need more PV at the very least. Bigger systems would be more efficient at 48V but you would need a new inverter to convert to a new battery bank voltage (you have enough batteries for a 24V bank). If you don't want to touch the batteries or inverter (assuming none are bad), you will likely need to get 2 80 amp charge controllers along with your additional PV capacity. The mystery panels should not be an issue if the voltages match. The PV wiring could possibly also be undersized (excessive voltage drop - more wasted energy on top of the PWM controller).

Do at least voltage test the batteries. SG testing is better.

NorthGuy · September 2013

Re: Inherited a mess?

By your description, I counted only 8 panels, so it would be 1200W.

The charge controller is undersized for 12V system, but might be Ok if you rewire for 24V. Most likely you will need a new inverter if you do. An opportunity to get one with good generator support.

Batteries are oversized compare to panels (and especially compared to charge controller), which means they were severely undercharged throughout their live. Looks like they're nearly dead. Perhaps they may be revived somehow.

Before you re-do your system it is a good idea to look at the consumption. This will help you figure out the size of the system you need, whether you need to expand or not, etc.

Gino · September 2013

Re: Inherited a mess?

hey all, thanks for all the tips! i think we can afford an mppt cobtroller and im gonna try for a generator as well..
i dont know m ch about generators that output 12v though..

do you guys think that if i rewired all the panels into 40V series and put those in parallel it would help with charging?
i thought that would lower the amps to a more sane value, this pwm says it supports input volts up to 55V??

thanks again!

Cariboocoot · September 2013

Re: Inherited a mess?

Check the specific gravity on the batteries first. If they are toast (and they probably are) you will need new batteries which actually opens up an opportunity.

If that system were working it could not work well: the C35 controller will only handle 35 Amps. The batteries @ 1040 Amp hours would like to see 100 Amps. That is a problem. The 1350 Watts of panel would provide 77 Amps (divide Watts by Vmp, not Voc, to get expected maximum current) which the controller can't handle. Upping the array Voltage will not help charging because the PWM controller only passes current; it can not down-convert the higher Voltage for more charging power (unlike an MPPT controller). It says it can take up to 55 Volts input because it can work with either 12 or 24 Volt systems, and the Voc on a cold 24 Volt panel can approach 55 Volts.

So you see as-is it can't possibly work. If it has been not working for years the batteries will be badly sulphated and unrecoverable.

As others have said, get a handle on your loads and see how much battery capacity you actually need. Then think hard about going up in system Voltage to at least 24, as that will be more efficient. You may be able to use some of the panels you've got; I'd keep the 'known good' ones and unload the 'mystery' panels. Four 150 Watt panels could give you 600 Watts, and if used on a 24 Volt system (two parallel strings of two in series) you'd get about 17 Amps which the C35 could handle. If you then replace the batteries with four GC2's you'd have a 7% peak charge rate. This is on the low side but is viable. You'd also have about 1.2 kW hours AC to work with. Small, but there are many cabin systems around that size.

niel · September 2013

Re: Inherited a mess?

gino,
you need to get an idea of the status of those batteries as you indicate that maintenance was lacking. as was said, give them a good charging, but also check for water levels. is the electrolyte muddy or off colored and are any of the plates exposed? check the specific gravity with a hydrometer after you've given them a charge.

zoneblue · September 2013

Re: Inherited a mess?

We seem to come across systems like this alot, (way too low pv to battery ratio). They date back to the time prior to the pv price fall, and converse lead price increase.

Those batterys are history. If you want to be kind, borrow a generator and give them a full absorb then EQ, if the sg fails to respond, bin them. But hey you never know.

inetdog · September 2013

Re: Inherited a mess?

zoneblue wrote: »

... if the sg fails to respond, bin them.

But keep in mind that the lead in the batteries gives them a substantial scrap value, so don't just give them away to the battery recycler or let them sit around.

Gino · November 2013

Re: Inherited a mess?

Hey All!
If your interested here is a status Update on our setup!

1. Our inverter died and is on its way back home, its a Wagan Tech Pure Sine 5000w (12v)
I would warn others to never buy from this company, inverter has been gone for 2 months now!!! will it over come back?
I'm hoping to sell it when it returns to sell it and get a 24v inverter then we-wire the battery bank for 24v.

2. Replacing PWM Inverter with MorningStar T-60 MPPT controller we just ordered. we hope that will fix charging issues, We want to run a mini fridge in addition to our current load
and are waiting for the new charge controller before trying it.

3. I know people think its weird but I built a "Single School Girl Bedini" Circuit and set it up on the battery banks, now the batteries are regularly at 13.5 by the end of the day (fully charged for my setup!

If anyone wants house photos look here : https://plus.google.com/photos/113084925789981363106/albums/5944484892596968513

Thanks!

PS: Any tips on a good charge Pure Sine Inverter?

jcheil · November 2013

Re: Inherited a mess?

Gino wrote: »

We want to run a mini fridge in addition to our current load
and are waiting for the new charge controller before trying it.

PS: Any tips on a good charge Pure Sine Inverter?

Just remember that those small fridges can use as much, and sometimes more power than a new full size 19cf energy star rated fridge (especially in the summer). There were a few threads here recently on this and someone did a rather extensive comparison of them. I also know from personal experience with 2 neighbors.

As far as the inverter, are you looking for a stand-alone inverter or an inverter/charger combination?

Gino · December 2013

Re: Inherited a mess?

jcheil wrote: »

Just remember that those small fridges can use as much, and sometimes more power than a new full size 19cf energy star rated fridge (especially in the summer). There were a few threads here recently on this and someone did a rather extensive comparison of them. I also know from personal experience with 2 neighbors.

As far as the inverter, are you looking for a stand-alone inverter or an inverter/charger combination?

Hey! thanks for the response, we have a good charge controller now the MPPT T-60 from morning star.

We are looking for an stand alone inverter, one with 24V input, in a perfect world we could sell our 12V input existing inverter and get that one.
Then i can reconnect our battery bank for 24V setup.. and reconfigure the solar panels..

jcheil · December 2013

Re: Inherited a mess?

Gino wrote: »

Hey! thanks for the response, we have a good charge controller now the MPPT T-60 from morning star.

We are looking for an stand alone inverter, one with 24V input, in a perfect world we could sell our 12V input existing inverter and get that one.
Then i can reconnect our battery bank for 24V setup.. and reconfigure the solar panels..

Well, since you do not need an inverter/charger, like myself, I have been happy with the Cotek SK 3000. A few people I know have had them for a few years without issues. It is a Pure Sine Wave unit, I swear it looks exactly the same as the Samlex (might even be). They are both around $1200.

Just be sure that whatever one you get has the ability to be hard-wired on the AC side. If it just has "plugs" then you will be limited in that the most you will be able to get out of that single outlet is 20amps (or 15amps). Also sometimes the ones with plugs do not like to be connected directly to a house panel due to neutral/ground bonding issues.

In MY opinion, I have had, and seen, terrible luck with AIMS products and absolutely RUN AWAY from those china-inverters you see on ebay. But again, just my experience. I have to admit one neighbor has an AIMS 5k that has been running for 3 years now. However, I have personally seen 4 of them die within 6 months, including 2 that I personally owned for less than 2 weeks each before buying the Cotek.

westbranch · December 2013

Re: Inherited a mess?

FYI Cotek is a manufacturer in Taiwan and make off brand units for others. And they make some of the Samlex products.

jcheil · December 2013

Re: Inherited a mess?

westbranch wrote: »

FYI Cotek is a manufacturer in Taiwan and make off brand units for others. And they make some of the Samlex products.

No wonder why they look almost exactly the same

zoneblue · December 2013

Re: Inherited a mess?

+1 for staying clear of chinese inverters. Ours died within 6 hrs of unboxing. Pop, and magic smoke.

For mid quality sine wave: samlex, powermaster (taiwanese), and xantrex prosine are often mentioned.

Also scheider SW series seem to be a good deal at the moment.

Inherited a mess?

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