2020 cherokee 27wk -2nd battery & switch

[FtWorthCamper]

I'd like to add a second battery to my trailer with a switch (single1/single2/dual/off). The battery will be mounted right next to the original one and a custom-made battery rack. Will I need to do anything special to the solar system? Does it hurt the solar system to have both batteries disconnected?

[NavyLCDR]

No.

[GravelRider]

No issues adding multiple batteries to your solar setup.

Just curious, but why are you adding a switch instead of just having a larger battery bank?

[Aussieguy]

when you add a second battery you should get 2 new ones that are the same size and condition...
an old battery can pull down a new one


make sure wired in parallel .... positive to positive negative to negative
your charging system won't know or care if you have 2 batteries

will just take longer to charge



if you want to look at using 6v golfcart batteries
they are much bigger and hold a lot more USABLE charge ... you can deplete them to 80%

[GravelRider]

Originally Posted by Aussieguy

if you want to look at using 6v golfcart batteries
they are much bigger and hold a lot more USABLE charge ... you can deplete them to 80%

To 80% and even lower... In fact, you can go all the way down to 20%.

[NavyLCDR]

Originally Posted by Aussieguy

if you want to look at using 6v golfcart batteries
they are much bigger and hold a lot more USABLE charge ... you can deplete them to 80%

Originally Posted by GravelRider

To 80% and even lower... In fact, you can go all the way down to 20%.

Lead-acid golf cart batteries are still lead-acid. Discharging them more than 50% will reduce their life.

[GravelRider]

Originally Posted by NavyLCDR

Lead-acid golf cart batteries are still lead-acid. Discharging them more than 50% will reduce their life.

Attachment 277635

They have thicker plates that allow them to safely go down to 20% SOC. The 6 V golf cart batteries are true deep cycle batteries. It is true that the lower you discharge them, the shorter the lifespan, but the same can be said of any discharge SOC. Your LA batteries will last longer if you discharge them down to only 60% than 50%, and 70% than 60%, and so on. I believe the lifespan of a 6 V battery is between 500-750 cycles if discharged down to 20% EVERY time. Considering I camp between 60-80 nights per year, I'm completely fine with this lifespan for a $90 battery.

For the record, I have my battery bank sized so that I rarely go under 50%, but if I do happen to, I don't sweat it in the least bit.

[NavyLCDR]

Originally Posted by GravelRider

Considering I camp between 60-80 nights per year, I'm completely fine with this lifespan for a $90 battery.

For the record, I have my battery bank sized so that I rarely go under 50%, but if I do happen to, I don't sweat it in the least bit.

It's a bit more of a concern for me when I have $450 in batteries on my trailer. I will stick with the manufacturer's recommendations. I will do everything I can, including opportunity charging, to not let them go below 50%.

[FtWorthCamper]

Im just concerned with the dual sliders sucking too much out of the batteries or the battery amps so low it will damage the slider motors or the 12vdc refer. If Im camping without shore power, I want to bring in the sliders in without starting up the generator that I intend to install.....

So .... are you saying a 12vdc Marine battery addition wont be as effective as. Replacing both eith 2 6 vdc batterys?

[bikendan]

Originally Posted by FtWorthCamper

Im just concerned with the dual sliders sucking too much out of the batteries or the battery amps so low it will damage the slider motors or the 12vdc refer. If Im camping without shore power, I want to bring in the sliders in without starting up the generator that I intend to install.....

So .... are you saying a 12vdc Marine battery addition wont be as effective as. Replacing both eith 2 6 vdc batterys?

A dual-purpose marine battery is a basic and inexpensive choice for a RV. Because it's dual-purpose, it's not the best design for RV application.
The next best step up, is a pair of 6v golf cart batteries, which are much better.

[GravelRider]

Originally Posted by NavyLCDR

It's a bit more of a concern for me when I have $450 in batteries on my trailer. I will stick with the manufacturer's recommendations. I will do everything I can, including opportunity charging, to not let them go below 50%.

I've also got about $450 in batteries on my trailer (was $360, but the prices of everything went up). I just checked the manufacturer's instructions on mine, and it does not mention anywhere how low to discharge them to. Which batteries do you have?

You really should stop the practice of opportunity charging. Nothing decreases the lifespan of LA batteries faster than continuously recharging to less than a full state of charge, like in opportunity charging. You'd be better off dropping down to 20% than opportunity charging to keep them over 50%.

[GravelRider]

Originally Posted by FtWorthCamper

Im just concerned with the dual sliders sucking too much out of the batteries or the battery amps so low it will damage the slider motors or the 12vdc refer. If Im camping without shore power, I want to bring in the sliders in without starting up the generator that I intend to install.....

So .... are you saying a 12vdc Marine battery addition wont be as effective as. Replacing both eith 2 6 vdc batterys?

You'll get a lot more usable amp hours out of two 6 volt batteries than you will two marine batteries, which aren't true deep cycle.

If you're worried about having the battery capacity to bring in your slides, you should invest in a battery monitor with shunt, so you'll know exactly how much capacity you have left. You can also see how much capacity it takes from your bank to bring in your slides, so you'll never be left wondering.

Your idea of having different batteries with switches will be problematic when they're at different states of charge (SOC). Lets say that you discharge one down far enough that you need to use the second one to bring in your slides. You now have two batteries at different SOC. You will need to charge each individually back up to 100% SOC before connecting as one battery bank. This seems like a lot of extra work and potential issues.

[FtWorthCamper]

They wouldnt be different batteries... they would be identiclal batteries on the one main switch. The purpose of the switch is really only to shut off both batteries while in storage. I just thought a marine A/B switch was a good idea.

[GravelRider]

Originally Posted by FtWorthCamper

They wouldnt be different batteries... they would be identiclal batteries on the one main switch. The purpose of the switch is really only to shut off both batteries while in storage. I just thought a marine A/B switch was a good idea.

My advice was assuming they were identical batteries. You don't want to ever have non-identical batteries in your battery bank.

Your camper should already have a shutoff switch (the battery disconnect switch), which you can use for while in storage. Mine is below my fridge (22MKSE). It looks like this:



I see why they have them on boats because it makes for a backup when you truly have no way to recharge (without solar), but for an RV I wouldn't mess with batteries potentially being at different SOC. You have three options to close slides if you have dead batteries (which you won't if you install a good battery monitor with shunt): 1. Shore power, if available. 2. Generator, if available. 3. Your tow vehicle, with engine running.

[FtWorthCamper]

Ureka!!! I found it! With the help of my reading glasses! The battery disconnect is located on the island in the kitchen! I thought it was the propane emergency disconnect switch. I intend to look into those 2 - 6 V batteries as a way to get a longer battery capability out of the trailer for those weekends where we have no hook ups. I presume I'm going to have to get some sort of a regulator or something to change the solar's 12 V system to feed the 6 V systems?

[GravelRider]

Originally Posted by FtWorthCamper

Ureka!!! I found it! With the help of my reading glasses! The battery disconnect is located on the island in the kitchen! I thought it was the propane emergency disconnect switch. I intend to look into those 2 - 6 V batteries as a way to get a longer battery capability out of the trailer for those weekends where we have no hook ups. I presume I'm going to have to get some sort of a regulator or something to change the solar's 12 V system to feed the 6 V systems?

Glad to hear that you found it!

You won't actually change the system. It'll still be a 12 volt system.

---------------------------------------------
tl;dr:

If you put two 6 volt batteries together in series, you'll have a 12 volt system, but with the same capacity as either battery by itself.

If you put two 12 volt batteries together in parallel, you'll have a 12 volt system, but with double the capacity.
----------------------------------------------

In case you were looking for a slightly nerdier version of it:

It all hinges on the equation V = IR and some basic electricity physics. Who knew algebra would rear its ugly head here?!

V = voltage (volts)
I = current (amps)
R = resistance (ohms)

You can basically ignore resistance, as that will remain constant for all intents and purposes.

You also have to know how series and parallel connections differ.



In series circuits (what you'll do when you connect two 6 volt batteries together), you connect the positive terminal of one battery to the negative terminal of the next battery, and vice versa.

In series circuits, you double the voltage, and the current remains constant.

So, if we have, for example, two 215 amp/hour 6 volt batteries connected in series, we double the voltage to 12 volts, but the capacity (which is current/time) remains the same.

Rearranged, V = IR is I = V/R, so if we double V, I = 2V/R.

In a parallel circuit (what you'd do when you connect two 12 volt batteries together), you connect the positive terminal of one battery to the positive terminal of the next battery, and vice versa.

In parallel circuits, you double the current, and the voltage remains constant.

So, if we have, for example, two 100 amp/hour 12 volt batteries connected in parallel, we keep the voltage constant, but the capacity is doubled.

V = IR, so if we double I, V= 2IR


Runny two 6 volt batteries in series is very common (or running four 6 volt batteries in series-parallel), and there are a TON of YouTube videos that make it very simple without knowing the physics behind it.

[NavyLCDR]

Originally Posted by GravelRider

I've also got about $450 in batteries on my trailer (was $360, but the prices of everything went up). I just checked the manufacturer's instructions on mine, and it does not mention anywhere how low to discharge them to. Which batteries do you have?

You really should stop the practice of opportunity charging. Nothing decreases the lifespan of LA batteries faster than continuously recharging to less than a full state of charge, like in opportunity charging. You'd be better off dropping down to 20% than opportunity charging to keep them over 50%.

Mine are USBattery XC2200 and I am going to continue to do exactly what the manufacturer of my batteries recommend according to the page of their user manual that I posted. If you want to tell USBattery they are giving bad advice, please go for it and let me know their response.

For example they say if you are going to take 60% out of the battery in a day, and you have a chance for a 1 hour charge, it is better to discharge to 50%, charge for 1 hour to 60%, and discharge to 50% rather than to do as you say and go from 100% to 40% and then charge.

Manufacturers recommendations for my lead-acid golf cart batteries were in post #6. I would recommend that you read that page because USBattery lead-acid batteries are no different than Trojan or Interstate, except maybe higher quality materials and construction.

[GravelRider]

Originally Posted by NavyLCDR

Mine are USBattery XC2200 and I am going to continue to do exactly what the manufacturer of my batteries recommend according to the page of their user manual that I posted. If you want to tell USBattery they are giving bad advice, please go for it and let me know their response.

For example they say if you are going to take 60% out of the battery in a day, and you have a chance for a 1 hour charge, it is better to discharge to 50%, charge for 1 hour to 60%, and discharge to 50% rather than to do as you say and go from 100% to 40% and then charge.

Manufacturers recommendations for my lead-acid golf cart batteries were in post #6. I would recommend that you read that page because USBattery lead-acid batteries are no different than Trojan or Interstate, except maybe higher quality materials and construction.

I didn't see the image you posted the first time around. Interesting that they specifically recommend opportunity charging for their batteries. I can't argue with their recommendation for their batteries... But it does run counter to what I know of LA batteries. Do you know if they have a new technology in their batteries that allow this? Or is this a case of old wives's tails regarding opportunity charging, I wonder?

The directions on mine specifically say to charge to full SOC when charging.

Either way, they also mention 675 cycles out of a battery discharging down to 20% continuously. For the average camper, or even the above average camper, this is a long lifespan.

[FtWorthCamper]

I assume that even with the trailer battery disconnected using the switch, the battery is still being charged by the solar (on sunny days) and/or when connected to the truck, while being pulled??

Where it is stored, it is parked under larger trees that block direct sunlight and there is no shore power available. So, the way I have been charging the single battery is with a tail-gator geerator and a 10 amp charger.

[GravelRider]

Originally Posted by FtWorthCamper

I assume that even with the trailer battery disconnected using the switch, the battery is still being charged by the solar (on sunny days) and/or when connected to the truck, while being pulled??

Where it is stored, it is parked under larger trees that block direct sunlight and there is no shore power available. So, the way I have been charging the single battery is with a tail-gator geerator and a 10 amp charger.

Yes, the battery disconnect won't disconnect solar (at least it didn't on the stock solar that came with my Cherokee). I'm honestly not sure about when connected to the truck while being pulled. I never tried it.

What do you mean a generator and a charger? I'm a bit confused by this.