You can add additional battery capacity to the base system fairly easily. Its a bit different for golf cart batteries and LiFePo4 batteries, so these are covered separately below.
Adding Capacity Golf Cart Batteries
Since it takes two 6 volt golf cart batteries in series to make a 12 volt battery, you are pretty much stuck with adding two batteries at a time. You could recycle the existing two golf cart batteries and look for either two larger 6 volt batteries that could be hooked in series to make a larger 12 volt battery, or for a couple of large 12 volt lead acid batteries that could be hooked in parallel. You could also look at this as a time to think about going to LiFePo4 batteries.
One thing to bear in mind is that aged lead acid batteries do not tend to work well with new ones, so if your existing golf cart batteries have some age on them, you will probably not be able to use them alongside a set of new ones.
Consider also that if you add two more 210 amp-hr golf cart batteries, you will be using up a fair bit of space and will have about 240 lbs of battery. People do this and its OK, but just something to think about before you go ahead.
If you have a set of two golf cart batteries and want to add two more, then each pair should be hooked up in series (making two 12 volt batteries), and then the two pairs should be hooked in parallel to make a larger 12 volt battery. Sketch below…
The positive lead from the batteries to the Hub should come out from the plus terminal on one of the two pairs, and the negative lead out to the Hub should come off the negative terminal on the other pair of batteries. Taking the power off on opposite pairs of batteries makes the voltage drop through both batteries the same.
Adding Capacity LiFePo4 Batteries
To add capacity to the existing pair of SOK batteries, you can hook one or more additional SOK batteries in parallel to the existing ones. The plus terminals are daisy chained together with short cables, and the same for the negative terminals.
The leads from the bunch-O-batteries to the BlueSea Hub must come off of opposite ends of the stack up as shown in the sketch above. This keeps the voltage drop the same across each battery.
For lead acid batteries (golf cart batteries) it is not considered good to mix batteries of different ages. If you do this, you will likely not get the best life.
If you are reading this before you start your build (good for you!), its clear that if you think you may want more battery capacity later, you should make space for them now, and the space should be right next to the other batteries as its not easy to hook groups of batteries together in such a way that they will work well together if they are not right next to each other.
If you are adding battery capacity because you are adding some heavier loads, you need to check that the current wires in the system that carry these higher loads are big enough.
I need to caution you here that this is not a system that is intended to grown into one of those 600 or 800 amp-hr things. If you want to do that, than this is not the place for you – but I wish you the best 🙂
If you see any errors or misleading information on this page, or there should be more information, please let me know in the comments.