Two Battery Bank Question

[TempleinCanada]

I recently installed a 2nd battery bank that is connected through a transfer switch that switches between shore power and Inverter Power. This new addition has a battery charger that is powered through the transfer switch when shore power is connected.
I have left the OEM bank connected to the OEM 12 Volt side with OEM converter which charges the 12 Volt side of my trailer. I have both the OEM Converter and the after market Battery Charger powered through my transfer switch.
I also have 500 watts of solar on the roof with a 30 amp solar controller that can charge 2 battery banks (fully charges the OEM side and then switches to new side when OEM side is fully charged)
This works great as both sides charge with solar when I am not connected to shore power and when I am connected each battery charger charges their respective battery bank.
So both systems are isolated from each other except when the Solar is charging.
Here is my question: If one of my battery banks becomes low in available amp hours could I connect the 2 battery banks together (with a manual switch)to equalize them (I know it is not ideal, but would be for an emergency only)

My main concern is that the solar controller sees the 2 battery banks as separate, what will happen when it sees both of them together????

Here are the specs of my components
170 Watt Carmanah Solar Panel GP-PV-170M
340 Watt BougeRv Solar Panel DSM-170W + DSM-170W
30 Amp Go Power Solar Controller GP-PWM-30-UL
1500 Watt Samlex Inverter PST-1500-12 Pure Sine Inverter
15 Amp Samlex Automatic Charger SEC-1215UL Battery Charger
30 Amp Samlex Transfer Switch STS-30 Transfer Switch
30 Amp Samlex Inverter Remote Control RC-300

[time2roll]

TempleinCanada wrote:
Here is my question: If one of my battery banks becomes low in available amp hours could I connect the 2 battery banks together (with a manual switch)to equalize them (I know it is not ideal, but would be for an emergency only)

My main concern is that the solar controller sees the 2 battery banks as separate, what will happen when it sees both of them together???

Yes you can connect all batteries without issue even on a regular basis.

Multiple charging sources is not an issue either. You can have both solar, converter, vehicle alternator, and a portable charger all charging at the same time without issue.

[valhalla360]

Veebyes wrote:
For reasons beyond me most RV parts suppliers are weak when it comes to 12V system bits & pieces.

Look here for a wide selection.

Ignoring the cost of anything labeled "marine", boats far more commonly operate away from shore power, so the demand is higher.

[Veebyes]

For reasons beyond me most RV parts suppliers are weak when it comes to 12V system bits & pieces.

Look here for a wide selection.

[valhalla360]

rockylarson wrote:
I have two battery banks. They are close together in two separate basement compartments. They are connected with a PERCO Marine switch the allows using either bank separately or both at the same time as well as disengage all. Pretty proud of myself when I did it but in reality I only disengage the side I am working on at any one time. Other wise they are both connected as "ALL" when charging.
PERKO SWITCH

I can see throwing a manual disconnect switch between them in case there is a short or other issue but much complication beyond that doesn't seem justified.

[wa8yxm]

You said: "My main concern is that the solar controller sees the 2 battery banks as separate, what will happen when it sees both of them together????"

Sort of depends on where you hooked the solar controller My best guess it it will work,, more or less as designed.

One thing to think of if you join the two banks total usable power increases. This is due to the link below

Peukert's law

[rockylarson]

I have two battery banks. They are close together in two separate basement compartments. They are connected with a PERCO Marine switch the allows using either bank separately or both at the same time as well as disengage all. Pretty proud of myself when I did it but in reality I only disengage the side I am working on at any one time. Other wise they are both connected as "ALL" when charging.
PERKO SWITCH

[valhalla360]

TempleinCanada wrote:
So to answer a few questions clarifying my situation. I previously entered the specs on my trailer in my profile and thought they would be accessible, regardless, it is a 21 ft Keystone Bullet bumper haul trailer.
The battery banks are at opposite ends of the trailer. When I added the new battery bank it was much easier to add it near the back near the electrical panel and shore power connection. If I had just added more batteries to the existing bank I would have had to add the inverter etc near the front which would have complicated the install significantly. (Running wires the length of the trailer)
After researching for a solution I believe if I just put a manual switch that connects the 2 battery banks and disconnects the charging wires from the solar controller to the second battery bank then the solar controller will just see 1 battery bank (which will comprise of the all the batteries).
BUT that still leaves the issue that I will have 2 battery chargers when I am connected to shore power, 1 charging each battery bank. I guess I could turn the breaker that powers 1 of them off. Seems to get more and more complicated.....

Actually after more thought the battery charger issue is really not really an issue, as once I am plugged into shore power I will not have a dead battery. Sometime talking to yourself helps 🙂

A bank refers to a set of batteries connected together. The batteries can be physically separated as long as they are wired together properly and they are still a single bank.

Given that the RV loads are likely to be relatively low for the most part no reason not to just connect the negative ground to the frame and run a single positive line to connect them the same as if they were in the same compartment (you presumably did that anyway if you have a means to combine them).

Even with an inverter pulling a significant load, as long as the half of the bank close to the inverter is decent size, it shouldn't be a problem. The closer bank may drop a little lower momentarily while under inverter load but will quickly balance out once the load drops. (splitting into separate banks does nothing to address the separation anyway).

[TempleinCanada]

O.K> Thanks for your help.
I do realize that long runs of AC wires are not an performance issue, but I did not want to have to run any wires from the front of the trailer to the back. So I opted to do it as I explained previously.
Good to know I can leave both battery chargers connected to common batteries. I never thought of 4 batteries up front instead of 2 being a weight issue, but you may be right
But tucking the new additions in the rear outside kitchen really worked well
Once again Thank you

[BFL13]

On the inverter install, it is right to have the 12v wires to the bank be short, but the 120v output can be on a long extension and no voltage drop with the 120v.

In the 5er we had, I put all the batteries up front with the inverter and a battery charger and ran the shore power cord from the back of the 5er up to the front to plug that into the inverter (converter off, fridge on gas) The power centre was in the middle of the trailer, but the long wires from front to there for the ordinary low amp RV loads didn't matter--I had the high amp charger and inverter up close to the batteries.

Your longer 12v wires to the back from the front batts will not be an issue for running the low amp Rv loads.

You can have both chargers on plus the solar for 3 at once and no problem. Don't fuss that the chargers are not all to the same battery posts. They will add their amps until the charger's voltage equals the battery voltage, so if one has a higher voltage it will keep charging the battery up past the voltage of the other charger(s) until they cannot do any amps and 'drop out' (but still on--just no amps).

You might have a problem with the generator watts though, if both chargers are too much of a load.

That small of a trailer would have problems with weight with all the batteries up front I guess.

[TempleinCanada]

So to answer a few questions clarifying my situation. I previously entered the specs on my trailer in my profile and thought they would be accessible, regardless, it is a 21 ft Keystone Bullet bumper haul trailer.
The battery banks are at opposite ends of the trailer. When I added the new battery bank it was much easier to add it near the back near the electrical panel and shore power connection. If I had just added more batteries to the existing bank I would have had to add the inverter etc near the front which would have complicated the install significantly. (Running wires the length of the trailer)
After researching for a solution I believe if I just put a manual switch that connects the 2 battery banks and disconnects the charging wires from the solar controller to the second battery bank then the solar controller will just see 1 battery bank (which will comprise of the all the batteries).
BUT that still leaves the issue that I will have 2 battery chargers when I am connected to shore power, 1 charging each battery bank. I guess I could turn the breaker that powers 1 of them off. Seems to get more and more complicated.....

Actually after more thought the battery charger issue is really not really an issue, as once I am plugged into shore power I will not have a dead battery. Sometime talking to yourself helps 🙂

[BFL13]

I have had split banks something like that. Did it manually though, no transfer switch. I had the same issue with that where the bank for the usual 12v loads got too low but there was still lots of AH in the inverter's bank but couldn't get at it.

Anyway, the solar controller (IMO no facts) will still only see one bank when they are paralleled. Whichever bank it is on will not be fully charged while it "equalizing" (be careful using that word to not confuse with over-voltage equalizing of a battery to desulphate it) so it will charge it and so also the other.

I had two different controllers with their own panels, One set for each bank.

The OEM bank will be neg grounded to the frame. The bank for the inverter does not have to be grounded to the frame at all--just the wires to the inverter. When you parallel the two banks that will neg ground the inverter bank too if that is an issue.

[valhalla360]

First question: What is your purpose in splitting the battery banks?

I don't see what type of RV you have. If it's a MH, putting the starting battery in a separate bank makes sense in case you run down the house bank, you can still start the motor.

If it's a towable or you are splitting the house bank on a MH, a single large bank with a low voltage cut off has some significant advantages:
- You can charge at a higher rate (without complex combiner systems)
- Puerket effect is less of an issue since you are effectively halving the draw as a percent of amp-hr, so you effectively can pull more amp-hr out of the bank.
- There are fewer parts to fail.