Am I reading this right...

System

Help Please, before I destroy something. I quite new at this solar thing, and I hope I'm just reading this wrong, which wouldn't be unusual. But I just finished installing a Morningstar Ts 45 charge controller and remote meter in my Rv. They're going to be used in regulating my single Solarex MSX 120 solar panel. The solar power will then be feed into 4-6 volt batteries connected to produce 12 volts. Now here's the problem I'm having.
The panel label states: Solarex-MSX 120. Series fuse-20. P. Max-119.7 Voc.- 21.4. ISC-7.91. VP Max-7.11 P Max-85.0 W. IP Max-5.66 A.
The lead from the solar panel is fused with a 20 amp. fuse, and before I put the fuse in and connecting it to the charge controller, I thought I would put my digital volt meter on the lead to check the voltage from the solar panel itself. It read: 21.6 volts. Is that what it should read? I thought it would be a lot lower than that, or am I just reading something wrong?
I wanted to check in with all the experts in this field before I did any thing foolish or stupid, and causing me more grief than I could possibly afford. And any and all help anyone could possibly give me to figuring this whole thing out would be truly appreciated.
Thanks a bunch gang, Crossroads.

petertearai

Re: Am I reading this right...

yep that is the open circuit volts. The regulator will drop it down to the charge voltages for bulk absorb and float.

BB.

Re: Am I reading this right...

Everything is OK... Voc=21.4 Volts

Vmp (voltage at max power under load at 70F cell temperatures) should be around 17.5 volts or so (did not see in the label numbers you typed).

-Bill

help!

Re: Am I reading this right...

Is it OK to mix 4v and 6v batteries? I thought it's best to keep all the batteries in a bank identical, even in their ages?

BB.

Re: Am I reading this right...

Mixing battery ages, chemistry, mfg. etc. is considered bad form...

If you have to match... Batteries in the same series string should be the same capacity (ideally, identical make/model/age). If not matched, then, for example, 3x4 volt 225 AH batteries in series with 2x 6 volt 225 AH batteries for a 24 volt bank.

If you have a 225 AH battery in series with a 100 AH battery--that string capacity is limited to 100 amps (100 amp*hour cells will go dead way before 225 amp*hour cells). Also the peak current will be limited to that of the smaller capacity cell. If you take a cell past 0% state of charge (reverse charge)--that cell will mostly be destroyed or unusable within days/weeks.

If you have to parallel batteries... For example 3x4 volt cells in one 12 volt string in parallel with 2x6 volt battery string. Each will charge approximately to the same voltage.

How they will share charging / discharging (current proportional to AH rating?)--I don't know and cannot predict.

But if you are stuck with having to make a bank from different cells--that is how I would do it. It should be a functional bank.

-Bill

niel

Re: Am I reading this right...

if putting differing batteries inline it would be best to have them switched so that one bank does not see the other bank. i think your bigger concern may be with can you keep a charge on so many batteries with so little in pv?

Windsun

Re: Am I reading this right...

help! wrote: »

Is it OK to mix 4v and 6v batteries? I thought it's best to keep all the batteries in a bank identical, even in their ages?

It is not 4 AND 6 volt batteries, it is 4 of the 6 volt batteries in series-parallel.

XRinger

Re: Am I reading this right...

Hi Crossroads,
I'm just learning the ropes with my new TS-45 and from the looks of your
panel specs, I'll bet you never get more than 10A from your PV.

I'm using four 125w panels in series to charge my 48v bank, and even
with cloud-edge boosts, my 10A fuse is still hanging in there. (Since May).

I have found that using the RTS (remote temperature sensor) simplifies using this system down in my cold basement.
At least it seems simpler to me.

Cheers,
Rich