Solar panel with 6v batteries?

[1320quick]

My 5th wheel has a 90 watt solar panel on it with a PVCM25D controller. The two 12v Interstate batteries that are in it have died after 5 years and I need to replace them. I'm thinking about doing two 6v batteries like the Trojan 105. The solar panel always seemed to do a good job keeping the 12v batteries charged. Any changes that need to be made to charge the 6v batteries from the solar panel? Is the 90 watt enough to keep the 6v batteries charged? Am I correct to assume that I just hook up the 6v batteries in series and then hook the positive wires from the controller to the positive of one battery and the negative wire from the controller to the neg of the other battery?

[wa8yxm]

ONe of the differences between an electronics technician and many others is how we see batteries.

YOu have now: One 12 volt battery made up of two pieces in parallel. Without knowing the specifics of the battery I'm guessing about 200 amp horus and about 40-50 usable amp hours.

Your purposed set up is again ONE 12 volt battery. Made up of two parts.
About 220 amp hours and 110 usable

The only major difference is capacity. YOu now have a 12 volt battery and when you convert you will STILL have a 12 volt battery.

Just a little bit bigger.

How I see the word "Battery" A collection of cells arrainged to obtain a specific voltage.

How most see "Battery" A package you can lift and carry..

WHy is a "D-CELL" flashlight not called a "D-Battery" Because it is one cell. you put five of 'em end to end in your Mag-Light or Stream-Light you now have a FIVE CELL battery. I hope this explains the difference.

[1320quick]

Thanks for your input guys. I picked up two Trojan T105's this morning and just finished installing them. Checked both batteries before I installed them and they showed 6.37v on both of them. Got the solar panel hooked up and the controller shows fully charged as well. I know the Solar won't recharge them when they are discharged but being able to maintain and keep them charged in storage is most important to me. Going to try them out next week as we are dry camping in a National forest area for 4 days.

[time2roll]

90 watts is plenty for storage in most conditions. If 90 watts served you well with two batteries it should continue fine with the GC2.

Yes the connections are simple as you describe.

[Optimistic_Para]

1320quick wrote:
Is the 90 watt enough to keep the 6v batteries charged?

Well, that depends on how much power you use every day.

If you asked us whether putting 5 gals of gas into your gas tank every day would keep it full, we'd have to ask you how many miles per gallon your rig gets and how many miles you drive every day before we could answer you, right?

The bottom line is that if your 90 watt panel produces more power than you use every day, then your batteries will stay charged. If you use more power every day than the panel produces, then your batteries won't stay charged.

[2oldman]

1320quick wrote:
Is the 90 watt enough to keep the 6v batteries charged?

If you don't use the batteries very much, yes.

[azrving]

Trojan suggests 14.8 charging voltage.

[garyemunson]

As 3tons mentioned, 6 volt batteries are taller so expect to have to expend some effort coming up with a new holddown scheme. With our Winnebago, when we changed over to a pair of 6 volts, I finally went to a golf cart dealer who fixed me up with a hold down that ran across the long edge of the battery and was made for hold down rods that ran at a 45 down to the tray on the other side of the battery. This only worked for me because our battery tray had a lip the new hold downs held that batteries against. The original 12 volts had a flat top that a bar ran across with hold down rods on each side. The 6 volts with their caps and terminals did not have a clear shot across the top for the original type hold downs. Nothing is ever easy on RVs!

[MrWizard]

No changes
it will still be a 12v system

[DrewE]

A 12V battery is six cells in series. A 6V battery is three cells in series. A pair of 6V batteries connected in series is exactly the same thing as a 12V battery, but is physically split into two chunks which makes it easier to tote around and fit in the battery tray and so forth.

(Incidentally, they're called "batteries" because they're a series of cells assembled into a unit. A gun battery is a series of guns assembled into a unit; a battery of tests is a series of tests considered as a single unit.)

[3_tons]

You’ll be just fine and since they are both flooded wet cell batteries you should see little to no difference in how the 6v batteries respond to the solar panel...As per the single 90w panel, I see that as more of a battery maintainer than a supplimental power source, in my view two 90’s would be even better, especially when overcast - just saying...You are correct in the cabling as well, two 6v in series are essentially one large 12v battery, but with a bit greater DOD (depth of discharge) ability, meaning more ‘usable’ amps...Also, the 6v batts will be approx 3/4” taller at the post...

Best Regards,
3 tons