Batteries

Timan · 05-21-2019, 04:41 PM

I'm sure this has already been answered many times before. But.... Lol.
I would like to add a second battery to my 233S. I currently have a 27. I checked the spacing on the battery rack and can not fit two 27 size batteries. Can I safely add a smaller size, such as a 24?
Thank you in advance.

larry2c · 05-23-2019, 09:20 AM

Lot's of people on here smarter than me on electricity can give you the why nots but the short answer is that when you put 2 unmatched batteries together the output drops to the level of the weakest component. My personal experience was to put a new group 27 battery with an old one (roughly 2 years old) and the run time I got out of the combo was barely more than my single group 27 battery. I finally bit the bullet and went with 2 6V golf cart batteries.

Timan · 05-23-2019, 01:04 PM

Quote:

Originally Posted by larry2c

Lot's of people on here smarter than me on electricity can give you the why nots but the short answer is that when you put 2 unmatched batteries together the output drops to the level of the weakest component. My personal experience was to put a new group 27 battery with an old one (roughly 2 years old) and the run time I got out of the combo was barely more than my single group 27 battery. I finally bit the bullet and went with 2 6V golf cart batteries.

Thank you for the reply. We don't boondock much, but I was just hoping to get a little more time off grid. Hopefully solar is in the future.

JLeising · 05-23-2019, 01:18 PM

Some use a selector switch like this to use one battery at a time. Eliminates the unmatched batteries concern:
https://www.amazon.com/Dewhel-Batter...s%2C517&sr=8-8

CincyGus · 05-23-2019, 01:33 PM

My thoughts are you have a few options:

The selector switch JLeising suggests. The issue I see with this is trying to charge the two different size batteries using the selector switch. You run one down to 50% then switch to the other one while boon docking, your going to have that one sitting at 50% discharge until you get back to shore power or an ability to recharge it. Batteries don't like to be discharged for significant periods of time.

Going ahead and biting the bullet and getting enough solar to recharge your battery each day and hoping for no cloudy days when your battery is low already. Even people with a bunch of solar generally have small generators for such occasions.

Buying a small inverter generator to charge your batteries or a larger one if you want to run AC. The Harbor Freight ones are about the cheapest quiet Inverter Gennies on the market. Honda and Yamaha are considered the best by many but are pricey. Champion and a few others are kind of in the middle.

Lastly, see if you can add more space on your battery tray by having someone remove the old battery tray and weld new angle on to make it longer. There is not much to the battery tray on most campers and some are not maximized very well to give you the most effective use of the space. Then make the decision if you want to give your group 27 to someone that fishes for their trolling motor and go get two golf cart batteries or two matched larger group batteries. I think this option is likely the cheapest.

gbaldwin · 05-23-2019, 02:01 PM

I know some dont like running a gererator, but I have one 12V battery - Deep cell - My routine is to run 2000 Genny for a couple of hours AM and couple of hour evening.... doing shower, and other heavier use power during this run time. On eco setting and quiet///

My single Bat never drops below 50% and keeps me going.

joeuncool · 05-23-2019, 05:06 PM

Quote:

Originally Posted by Timan

I'm sure this has already been answered many times before. But.... Lol.
I would like to add a second battery to my 233S. I currently have a 27. I checked the spacing on the battery rack and can not fit two 27 size batteries. Can I safely add a smaller size, such as a 24?
Thank you in advance.

We have a 233S and run 2 6 volts. They fit just fine and probably have more amp hours than 2 group 27's.

Chuck_S · 05-23-2019, 05:12 PM

GC2 battery has the same footprint as the simple Group 24 battery dealers fit. Just a bit taller. I've been running a pair for 12 years. Not the same pair but just one replacement.

-- Chuck

Theo · 05-23-2019, 08:16 PM

When I upgraded to 2 GC2s, I also invested in a highly configurable battery monitor (Victron). It took some adjustment to match the no-load volts measured at the batteries, but now I know at a glance when the voltage gets close to 50%. Also, an alarm can be sent when a high/low voltage threshold is crossed. The amps being drawn is shown in real time, allowing the isolation of each item’s DC amp draw. The optional battery temperature sensor allows temperature-compensated volts to be displayed and, presumably, to be used by monitor’s internal algorithms. All this may be “overkill” to most, but it can help maximize the efficiency of any battery’s use while helping to minimize generator run time.

In our region, the State Parks are beautiful...but sites with hookups rarely exist. The plan is to stretch the number of our dry-camping days by more effectively using our battery bank’s amp hours.

FWIW...

TitanMike · 05-25-2019, 10:30 AM

Quote:

Originally Posted by Theo

When I upgraded to 2 GC2s, I also invested in a highly configurable battery monitor (Victron). It took some adjustment to match the no-load volts measured at the batteries, but now I know at a glance when the voltage gets close to 50%. Also, an alarm can be sent when a high/low voltage threshold is crossed. The amps being drawn is shown in real time, allowing the isolation of each item’s DC amp draw. The optional battery temperature sensor allows temperature-compensated volts to be displayed and, presumably, to be used by monitor’s internal algorithms. All this may be “overkill” to most, but it can help maximize the efficiency of any battery’s use while helping to minimize generator run time.

In our region, the State Parks are beautiful...but sites with hookups rarely exist. The plan is to stretch the number of our dry-camping days by more effectively using our battery bank’s amp hours.

FWIW...

What makes the battery monitors like the Victron so great is that they aren't just a voltage monitor. Yes, they show voltage but the state of charge percentage is derived from coulomb counting.

Voltage readings can be inaccurate for SOC measuring because they drop when the battery is under load then rise when the load is shut off. Coulomb counting involves measuring the actual current as well as voltage while under load then calculates how much energy was removed or replaced.

Relying on a voltmeter also requires that you take into consideration the temperature of the battery.

Another nice feature of the Victron monitor is that it will tell you how much time you have remaining on your battery bank at the current load.

Lastly, a voltmeter will show a full charge voltage on a battery but only after you've charged it and let it sit several hours. The Victron will show you when you've hit full charge without the long wait. Important when relying on a generator for charging. You may be shutting down the generator before full charge has actually been achieved.

You may also like: