Okay. I need new batteries. What batteries would you recommend?

[Sunking]

As for the safety aspect your system looks well built with the correct size cable and cable terminations. My car's starter motor is 2kW and if I had a larger motor could be 3kWs. There are millions of cars out there that have cabling capable of running 200-300+A.

Ignore that comment, this guy wants you dead and does not know the difference between a burst and continuous loads. Your car was not built or designed by DIY's in a garage. Karrak just gave you a recipe for a FIRE.He has no clue what he is talking about, just a salesman.

[Sunking]

I know you are saying forget 12 volts but.....trying to keep the budget in check, what if I went with a single string of new batteries in series of 6, Trojan 2V 1110 ah L16RE's, upgraded my panels to 700 watts, upgraded charge controller to the MS TS-MPPT-30 and kept my DR 2412 inverter/charger ?

When did I say forget 12 volts? I had to go back and reread your OP. 320 panel watts severly limit what you can do. You asked about battery replacement and I have already given you several options. With just 320 watts of Solar Panels you are limited. If you are staying at 12 volts, a 320 watt solar panel system can support a 12 volt battery as small as 200 AH up to 400 AH. You cannot go to 1100 AH, your panels will not support it. You rpanels on a ggood day can only generate 1 to 1.5 Kwh of usable power each day.

[Mike90250]

..........As for the safety aspect your system looks well built with the correct size cable and cable terminations. My car's starter motor is 2kW and if I had a larger motor could be 3kWs. There are millions of cars out there that have cabling capable of running 200-300+A.
Simon

THIS is COMPLETE BULL. You cannot compare a automotive starting system designed only to endure seconds of cranking, to a generally DIY system.
The starter cables WILL melt if used for more than SECONDS.

200A needs 3/O wire, 300A needs 350cm

Enjoy a weeks vacation in Ban Land.

[Sunking]

Yeah both Karrak and Dax are gone. Two most dangerous fools on this forum.

[Swampy]

When did I say forget 12 volts? I had to go back and reread your OP. 320 panel watts severly limit what you can do. You asked about battery replacement and I have already given you several options. With just 320 watts of Solar Panels you are limited. If you are staying at 12 volts, a 320 watt solar panel system can support a 12 volt battery as small as 200 AH up to 400 AH. You cannot go to 1100 AH, your panels will not support it. You rpanels on a ggood day can only generate 1 to 1.5 Kwh of usable power each day.

Hi Sunking.....your last comment in Post #5 was to forget 12 volts. Please don't get me wrong, I appreciate every suggestion you have given me. I am learning lots and thanks again. Right now I'm thinking of upgrading my panels to at least 700 watts and changing my cc accordingly.

[SunEagle]

Yeah both Karrak and Dax are gone. Two most dangerous fools on this forum.

Umm. Actually Dax's ban has expired and Karrak's vacation is only for 1 week.

My guess is they will both be back but Mike will not be the only MOD that will cut them short if they post anything dangerous.

[Sunking]

Hi Sunking.....your last comment in Post #5 was to forget 12 volts. Please don't get me wrong, I appreciate every suggestion you have given me. I am learning lots and thanks again. Right now I'm thinking of upgrading my panels to at least 700 watts and changing my cc accordingly.

OK my bad. I did say if you are careful and infrequent use, and want to save some coins use your 12 volt Inverter/Charger.

I am not going to bore you with a lecture about 12 volt system. 12 volts does have its application like RV's Boats and Autos where gizmos and gadgets are directly powered by 12 volts and all wire runs are short by nature. Problem is it has trapped most folks in a 12 Volt Battery Box. Early systems were 12 volts and compounded the problem. Once you cross the line into a home, everything changes as limitations have been lifted and new demands. You move into the world of higher power and AC power. Higher power needs to come from higher voltages. Once you cross 100 amps, you are in some very dangerous territory.

Here is what you need to know. Panel Wattage and Battery Capacity need to be matched up and compatible. Lead Acid aka Pb batteries have minimum and maximum charge requirements. For FLA batteries typically C/8 is the fastest you want to charge, no slower than C/12, and C/10 is spot on perfect. It is a window of acceptance.

With that said based on new information (700 watts) means your 12 volt battery window is as small as 460 AH up to 700 AH. Did you say 24 volts? Cut the numbers in half or 230/350 respectively.

What is curious is 700 watts. What wattage panel are you thinking? You can get in trouble stuck with a Prime Number of Panels, the exception is 1 and 3. If you end up with 1, 3, 5, 7, 11, 13....... You are screwed because you are limited to only 2 possible configurations of all the panels in Parallel, or all in Series. There is no other option. Last thing you ever want is all your panels in Parallel. If you have more than 3 panels in Series, you have to start a second but equal string because of Voc input limit on charge controller. 700 is just a queer number that will be hard to work with be diffilcult to work with if you expand. 200 and 250 wattt GT panels are plentiful, cheap, and make excellent building blocks. Get yourself 3 of them, wire them in series, and good to go. Just be sure to get the right Charge Controller. Right now you are looking at a 80 amp MPPT model or about $600 worth of controller. 700 watts @ 12 volts = 59 Amps. If you buy a 60 amp controller, with 12 volts is maxed out at 700 watts, just as wel get an 80 amp model for growth at 12 volts. Or if you upgrade to 24 volts can go to 1500 watts of panels. .

[Swampy]

Sorry to take so long to reply and thanks for the info. I do have a follow up question. If I get 3 new panels as suggested, do I have to change the wiring from the panels to the cc ?
The existing wiring from my 4 panels is 10 gauge and the total length is roughly 45 feet from panel to cc.

[karrak]

If you are going to use an MPPT solar controller you should only wire the new panels in parallel with the old ones if the new ones have the same maximum power point voltage (V_mpp).

Might be better to keep the 85W panels on the old controller and put the new panels on the new controller.

To check the suitability of the cable http://www.calculator.net/voltage-drop-calculator.html

What wattage and voltage panel were you thinking of getting?

Simon

[Swampy]

Peak Rated Power	Pmpp (W)	305	300	295	290	285
Maximum Power Voltage	Vmpp (V)	33.44	33.14	32.84	32.537	32.236
Maximum Power Current	Impp (A)	9.196	9.127	9.06	8.989	8.92
Open Circuit Voltage	Voc (V)	39.981	39.83	39.68	39.528	39.38
Short Circuit Current	Isc (A)	9.673	9.59	9.51	9.424	9.34
Module Efficiency *	Eff (%)	18.9	18.6	18.3	18.0	17.7
Power Output Tolerance	[- 0 , + 4.99] Wp

Here are the specs for the panels I was thinking about. I would go with the 285W panel if I could.
Also, I did not know that it was possible to keep my existing panels/wiring/cc and then add new panels separately with their own wiring and cc.
That configuration might be the way to go? I could then only add 2 panels instead of 3 to get the charging power I'm looking for. Your thoughts please?

[karrak]

I am a little confused, if your system has been working fine until now why do you want to add the extra panels? Are you going to be changing your usage patterns and the amount of power that you use?

If you are going to stay with 12V and if you buy a 30A MPPT controller the maximum power you will get from the controller is around 400W (30amps*13.5volts) so you wouldn't be able to utilise all the power from two panels.

One upgrade path might be to add a 30A MPPT controller and two panels to your existing system and when your inverter dies to change your system to 24V and buy a new 24V inverter.

Simon

Off grid 24V system, 6x190W Solar Panels, 32x90ah Winston LiFeYPO4 batteries installed April 2013
BMS - Homemade Battery logger github.com/simat/BatteryMonitor
Latronics 4kW Inverter, homemade MPPT controller

[Swampy]

Sorry if I have confused things. My current setup has worked well, but before I replace my batteries I was looking for some battery advice and got some replies that my setup was unbalanced. By this I mean way more battery bank capacity then panel wattage. So, I thought I might go with less batteries e.g. from 12 to 8 and increase my panel wattage. It was actually your suggestion in Post #24 that got me thinking about balancing things by adding a couple of panels with their own charge controller.

[karrak]

Is your cabin only used on a part time basis and if so how many days do you spend there and how large are the gaps between your stays?

The reason I ask is that I doubt very much that your 4x85W solar panels would supply you with the 1.5 kWh of power that you say you use on a daily basis. Your current battery can store around 16kW of power so would last four to five days without going below the recommended minimum charge of 50% even without any power coming in from the solar panels.

Simon

[Swampy]

Yes, we don't use the cabin everyday. We typically spend 3-4 days there and then back home for the rest of the week . We use it from May to the end of October and the cabin is closed up from November to the end of April. The longest stay would be a full week in the summer.

[karrak]

This explains why your system works so well,most of the advice you have been receiving from others relates to systems used continuously. Unless you want to change the amount of power or the amount of time you spend at the cabin I would replace the batteries with another set of AGM batteries of the same capacity and leave the rest of the system as it is.

As you may be aware a revolution with battery storage is just starting. At present Lithium Ion batteries are the prime movers of this revolution. IMO for those people who have some technical knowledge and use their off grid systems continuously Lithium Ion batteries are currently a far better choice than Lead Acid batteries. Next time you replace your batteries or need to upgrade your system they, or another type of battery other than Lead Acid batteries will probably be the best choice for you as well.

EDIT: It might be worth looking at the cost effectiveness of two extra panels, an extra 30A MPPT controller and half the battery size.

Simon