Replacing batteries

[extrafu]

Hello everybody,

I've just received my new Rolls 6 CS 25P deep-cycle 6V battery (820Ah) to replace my Rolls S550 (428Ah) ones - 8 of them for a 48v sytstem.

I'll basically just write them in series like the old ones. I've a Schneider XW6848 inverter, 2 MPPT 600V-80A controllers and the PDP (and other stuff, like the battery monitor, SCP, gen start, etc.). I basically plan to: disconnect the power panel from the inverter
disconnect the PV array from each MPPT controller (I have at DC disconnect for that for each of them)
disconnect the MPPT from the battery bank (I have breakers in the PDP of that)
disconnect the battery bank - postive first, negative after from the battery terminals
Then, swap the batteries and connect them in series like right now. Then do 4 to 1. I do no think I can disconnect the *inverter* from the battery bank through the PDP using a breaker.

Does that sound about right? Any extra precautions to take?

Thanks!

[MichaelK!]

You are essentially doubling your amphour capacity. Will you also be adding more solar panels? Assuming you want to charge your batteries at 1/10C, that's ~82amps. So, to get adequate charge density you should have 82A X ~50V X 1.25 effeciency factor = 5100 watts. What do you have in place?

Why are you disconnecting the power panel from the inverter? Why can't you disconnect the inverter from the battery bank through the PDP. Your PDP should have a big 250A breaker for cutting power from the battery bank. What do you mean by doing a "4 to 1"?

I would do things in this order
1) Shut off the inverter via it's on/off switch
2) flip breaker to turn off the solar array
3) flip breaker to turn off the charge controller
4) flip the big 250A breaker connecting the batteries to the PDP

5) swap out the batteries. Here you need to be very careful when you are wrenching the connections tight. You need to be very careful that the wrench handle does not come close to another battery contact. Be very careful that you don't lay a bare arm across any of the contacts while holding the wrench to a battery contact. Use a volt meter every step of the way to confirm what you are expecting to happen does actually happen.

6) switch the charge controllers back on. Wait for them to boot up.
7) switch the solar array back on. Confirm that power is passing through the controller.
8) flip the big 250A breaker back on.
9) turn the inverter back on via the on/off switch
10) flip on a light switch to confirm the power's there.

[Mike90250]

Before doing anything, label each battery A B C D .... and record it's resting voltage and specific gravity (SG) Then log both volts and SG daily for the first week then weekly, then once a month. That will get you close to your batteries and let you observe and track their status. If you have a "dud" from day one, it's unlikely it will get better.

[extrafu]

@MichaelK! - thanks I've located the 250A breaker on the PDP. I'll follow your procedure.

@Mike90250 - I'll also label them and take initial measurements.

[extrafu]

Also before disconnecting my 8 6V S550 (428Ah), I plan to charge them as much as I can. I want to sell them after as they in very good shape - as I took good care of them.

We never know but I think it'll take a few months before they get sold. I plan to wire 2 in series and charge them one pair at the time for a week, and continue like that until I sell them.

Would a good 12V "car" charger do the job? I had this one in mind: https://www.amazon.ca/STANLEY-BC15BS.../dp/B01BYFSUJW

Thanks!

[extrafu]

I found this 12 to 72V charger: https://www.amazon.ca/dp/B07R55C628/...I23FC9IAX1G126

Priced OK for a temporary solution and I will be able to also charge other 12V batteries with it (car and motorboat).

[extrafu]

I've just installed the new batteries - all went fine, many thanks for your advices! I still need to cleanup the wiring stuff but here's a small pic.

2019-11-09.jpg