One immediate advantage of using a number of smaller batteries is that if one fails it is replaced more cheaply than a larger one. There may be problems with integrating this new battery in with the others especially if there is a big difference in the ages. Also need to factor in higher initial costs of more smaller batteries compared to relatively cheaper cost of larger batteries.

snoopySA said..
Hi all I couldn't find anything in search engine covering this topic. Apologies if it has already been covered. This topic is not related to boating but Same rules would apply I believe. I want to set up a small 12 volt off grid power system in my shed. I have panels and a regulator. I would like to have around 600AH battery capacity. My question is am I better off with more lower AH batteries to total the 600 or several 200AH batteries. I am leaning toward 6 x 100AH batteries as I can transfer them to my caravan and car for camping. (Maybe to my yacht one day) any thoughts on the pros and cons.
cheers Alan

I believe that the best bang for the dollar is still 6 volt FLA golf cart batteries, pairs wired in series to give 12 volts thence parallel for capacity.
If you want to achieve 600AH usable capacity then you need 1200AH of batteries, remembering that you can really only discharge to 50%.
Also, should you at some time experience a dud battery in a bank of multiple batteries then you should either replace the entire bank or reconfigure to remove the dud. Introducing a new battery to an older existing bank will merely draw down the new to the level of the existing.

Crusoe said..
My thoughts are you should avoid putting batteries in parallel. We install and maintain stand only off grid systems all the time and very rarely do we parallel batteries. When installing flooded or sealed lead acid batteries they are normally 2 volt batteries. But all our stand alone system have back up generators. These are critical to ensure the batteries never drop below about 60% charge. On the cheaper end of the scale something like a PL40 MPPT can be set up to provide a start signal for a gen set. You really need to keep an eye on the battery state of charge and people (including yachties) get very apt at doing this.

You can certain do it without a gen set but you have to be prepared to stop using power if the SOC gets down and then wait till your batteries recharge (a bit) before starting to use them again. In theory, if a system is sized correctly, the gen set should never need to run, but who knows how long the rain will stay. A lot of people who do the off grid thing on land also use Selectronic inverters WM1200-12 or similar, As the quality of the sine wave is excellent. They can also dig deep when needed and not trip on start currents.

Unfortunately there is no cheap way around going off grid if you want to install something and get about 10 years out of it. But if you are only doing it for a short duration then there may be ways to save some money. We also install lithium batteries on hybrid (grid connected battery) systems but haven't come across any one with the money to do lithium in an off grid situation on the land.

Hope you find a solution that suits your requirements and budget, cheers.

Nice presentation however I just can't see all this being able to fulfil this "I am leaning toward 6 x 100AH batteries as I can transfer them to my caravan and car for camping. (Maybe to my yacht one day) "

Hello Datawiz, fully aware that its common practice to put batteries in Parallel but it does have its draw backs. Even had batteries in parallel on my boat. One example is that when batteries age they do not age at exactly the same rate, so which ever battery or battery string has the worst characteristics, the next battery string be pulled down to that value. What happens after charging, is the battery or battery string which has accepted the higher charge will actually discharge into the other battery until the good battery has reached the level of charge of the worst battery.

My comments above are really about off grid installations where people are interested in outputting 240Vac and not like what boats are set up for, being either 12Vdc or 24Vdc. In an off grid situation, our battery packs are normally done with 2 volt batteries that have about 1105ah each. So in a 24 volt system that would be 12 of these batteries to give 1105ah at 24Vdc which is the same as 2210ah at on a 12Vdc system. These are at the smaller end of our installs, as most of the system we install now have 24 batteries giving us 48Vdc, which would be (4420 ah at 12Vdc). To get more amp hours we just up the size of the batteries.

People come to us to do these installations and when they are forking a $1000 a battery and there's 24 them, we need to reduce any reason for failure in the next 10 years of their life. Parallel batteries would probably work well for the first few years but as they start to age we start to get problems. Customers don't like problems.

With all our installs, we have auto generator starting to protect the batteries from being discharged too low. We do not leave it in the hands of the customer, as they are usually the most unreliable part of the system. We also install a lot of Selectronic SP Pro's (its an inverter that produces 240Vac and can charge batteries + many other functions) which have the ability to download performance data. Helps us sort the what really happened.

Our systems are designed to have enough capacity to give the customer 3 to 4 days without charging, like what you may get in overcast or rainy weather. And people who live off the grid normally have to change their electrical usage habits. Not just any old fridge will do. Gas hot water or solar, plus gas cooking. Never use an electric frying pan. (just like living on a boat) Well, you can have all the mod cons if you want to put in extra batteries and solar panels plus a bigger gen set to service all the fun. A lot of it's just common sense (but as well all know, not to common)

Link below is for the one of type of batteries we install. I don't think they are suitable for marine use, but have never asked the manufacturer about this use.

www.batteriesdirect.com.au/shop/product/23645/ngs6021130hs0fc-(a602/1130).html

There's many ways to skin a cart and this is just one of them and I'm not saying it the right way or best way, its just the way we do it.

Cheers