Need Help on Battery Type for Solar ?

scrubjaysnest wrote:
The 300 watt kit isn't enough for 4 - 6 volt GC batteries. It is perfect for two GC batteries. If you plan on the 4-6 volt GC's you will need at least 400 watt and a MPPT controller and even that will be marginal for longest battery life.
The inverter only has an efficiency of 83 to 85 %. If you have to have a TV look for something in 12 volt with LED screen.

As a starting point 100 watts of solar per 100 AH of battery is a very minimum.

You don't need an MPPT for 400 watts. While nice to have not a necessity.

Thank you all for your responses! I will definitely go with the golf cart batteries and know that when power is down I have no problem running the generator with or without battery charger to bring the battery bank back up. I just wasn't sure which batteries would do the job better and now I know! :)

How much solar you need is not a function of the battery bank. If is a function of how many amp-hrs that you use.

300watts of solar panels will likely put out around 100-125amp-hr each day (depends on how much sun they get. It could be much less if you park in shade).

If you use more than goes in each day, the battery bank will be drained over time and you will have to find another means of charging.

If you are limited on space, another vote for 6v golf cart batteries.

scrubjaysnest wrote:
The 300 watt kit isn't enough for 4 - 6 volt GC batteries. It is perfect for two GC batteries. If you plan on the 4-6 volt GC's you will need at least 400 watt and a MPPT controller and even that will be marginal for longest battery life.
The inverter only has an efficiency of 83 to 85 %. If you have to have a TV look for something in 12 volt with LED screen.

As a starting point 100 watts of solar per 100 AH of battery is a very minimum.

100% agree with Scrubjay'sNest on this. For the usage you describe, you might be well off with only two GC-2 golf cart batteries... as ScrubJay'snest said - more properly balanced for your 300 watts.... but in any case the GC-2 batteries are best. You certainly won't hurt anything if your 300W can re-charge four of the GC-2 batteries after a night's use.

4 GC batteries wins. They have the most capacity, should last the longest, and you end up with only 2 parallel "strings" of batteries. The more batteries or sets of batteries in parallel the worse the installation. Batteries in parallel don't usually charge and discharge evenly.

4x GC2 gets my recommendation.

My original 4 Trojan T-105 batteries lasted 13 years. Go with the golf cart batteries.

For solar, check this place. You will want to look for 12 volt nominal output, and aluminum frames, so you have something to attach to.

SunElec.com They had some 140 watt panels on sale a few weeks ago for $229.

Be careful not to buy house panels, without frames, and designed to mount to frames bolted to your roof. The frames can get expensive, and are not designed for flexing and traveling at 70 MPH.

If you click on my name, then click 'view posts' and search Solar, you will find several detailed responses on the subject, some with pictures of my roof and mounts.

You can buy the grey romex that is UV resistant at Home Depot. For mounts, I have 6" long 2" angle aluminum with holes for 3 #10 screws into the roof, and 5/16" hole for the 1/4" bolt into the panel.

Good luck,

Fred.

Another way of looking at it is yes the solar is small for the four 6v's but compared to the needs it isn't. It should easily cover the need depending on the conditions. Worse case is if the solar can't keep up due to bad conditions for long enough, you would have to fund a alternate means of charging be it running a generator on a extended trip or plugging in once you are back home if the batteries don't get too low before then.

Even with a large bank and a better than 1 to 1 ratio watts to Ah, there are going to be times when it's bad enough for long enough that I'll have to run a generator.

The golf cart batteries are more durable and will afford more capacity. They also cost less than equivalent capacity in 12V.

I charge two banks with a total capacity of 300AH using a single 235W panel. My inverter is over 90% efficient. Not everyone's gear is the same.

X2 on the 4 golf cart batteries.