Battery question...part 2, group 24 or 27? - Page 2

Poppy & Nana · 07-07-2012, 04:03 PM

Quote:

Originally Posted by jsms264

We were at Rollins pond. I charged every couple days...we had 3 teenagers with us so I didn't want to see how long we could go....it could of got very ugly in the woods with teenage girls and no power. I would rather wrestle a black bear.

HA HA - been there done that but with only two girls!!!!!

**JohnB** · 07-07-2012, 07:50 PM

Joe,

You battery cart came out great!

OK, where did you get those really nice looking straps for the covers?

John

jsms264 · 07-08-2012, 06:24 AM

John....I to hate the straps made for these battery boxes. They are very difficult to remove, I've cut them off before out of frustration. The ratching straps I got at Home Depot for like $5. They were 8' long, I cut to more manageable length and burned the cut ends. I image they will rust really fast, but for the cost and convenience I'll just replace as needed.

I also bought a cheap battery voltage reader that plugs into the DC outlet. I have to admit I don't know a lot about DC voltage...so I don't totally understand how to read/monitor levels. I just would check to be sure I didn't go below 12.0 volts? Is that correct????

Jim-Bev-2363 · 07-08-2012, 07:51 AM

Thanks Joe. I just remembered I had a strap similar to that. It is now on the battery.

**JohnB** · 07-11-2012, 11:07 AM

Quote:

Originally Posted by jsms264

John....I to hate the straps made for these battery boxes. They are very difficult to remove, I've cut them off before out of frustration. The ratching straps I got at Home Depot for like $5. They were 8' long, I cut to more manageable length and burned the cut ends. I image they will rust really fast, but for the cost and convenience I'll just replace as needed.

Quote:

Originally Posted by jsms264

I also bought a cheap battery voltage reader that plugs into the DC outlet. I have to admit I don't know a lot about DC voltage...so I don't totally understand how to read/monitor levels. I just would check to be sure I didn't go below 12.0 volts? Is that correct????

Hi Joe,

Thanks for the info on the straps. I will for sure start looking for these. Yours looks just like the ones I have for my canoe tie downs with the aluminum grip clip. I see you too have used a few choice words about the standard battery box straps..... They are evil....

To your battery question, I see you have the chart for the 12 volt side of life web site. Or at least they have that same colored one. The goal to create the longest use out of your battery is to not go below 50% state of charge. It takes more heat to recharge a battery back up once you go below 50%. So the thought is, recharge before you get much below that point. It can be above, just try not to go very far below as a routine practice.

Here is some more info off the Trojan battery site. http://www.trojanbattery.com/BatteryMaintenance/Testing.aspx

The chart they have on the bottom says 50% is 12.1 volts. So yes your 12.0 is in the right spot. They refer to this as resting voltage. Resting meaning it is not working a lot as you will get a voltage drop from turning on a high power device like a water pump or worse the furnace.

There is also what is called a "surface charge". As you charge the battery with 13 volts and above, 13.25 for float, 13.65 for normal charge and 14.4 for boost, the voltage rises up that high in the battery as you are forceing voltage and current into it. At the instant you unhook the charger that high surface voltage (surface charge) is still there. By using volts as a method of determining state of charge of a wet cell, you have to wait until that surface charge bleeds off, then do the volt test to be accurate. This bleed down can take up to 8 hours.

Point: Just because the battery says 13 volts after 3 hours of genny run time with the genny off does not mean the battery is over 100% charged. In reality it may only be 60 to 75% charged. And in 8 hours it will reflect that true voltage.

When boodocking after the first 8 hours, and no high power use in the camper, then read your volt meter for the state of charge of the battery. The absolute perfect place to do a volt test is right on the battery. This is not always easy and in the case of battery covers straps....down right painful....

The next best is right at the converter on the heavy gage battery wire. The voltage drop there from the battery is very little.

A heads up by plugging in to the Wineguard cigarette lighter plug. If the antenna power booster is on, the little green light, then there is a power draw right at the plug. That can cause a slight voltage drop when measuring battery voltage and give you a reading lower than it really is. Since your boondocking unless you have a power source for the TV, odds are high the antenna booster is off or should be as it is sucking precious battery power for not being used. Try it next time your out in the camper. Does the voltage go down slightly by turning in the booster? There is also the possibility that lights in the camper may be on that same plug which can create a voltage drop and give a false reading of the battery condition.

The meter you are using and plugged in the TV outlet is a good quick way to do what you are doing. There is the potential to have a slightly different reading there than at the battery due to the wire size feeding it. It should however be consistent. If you really want to sort this out, plug in your meter, booster off, nothing running in the camper including lights. Read the meter. Then with a digital volt meter go out to the battery and measure it there. The inside plug in meter may read slightly lower. The difference between the battery and the inside is the voltage drop in the wire itself less any accuracy in the meters themselves. Remember the difference and then use that to figure out inside what the real voltage is.

Point: Check the resting voltage of the battery by using the antenna plug with nothing powered on in the camper except the LP gas detector. If there is a voltage drop due to the wire size, adjust your reading accordingly.

PS. I also do not know if the fridge 12 volts is on that Winguard plug. You can test that too by powering the fridge on and off and see if the voltage drops.

Hope this helps

John

PS 2, is your camper stored near the house? If so adding a Battery Minder to keep be plugged in all the time and keep the batteries up at 100% SOC and desulfated is the best way to get the most life out of them. I use one made by VDC Electronics.

jsms264 · 07-12-2012, 05:29 AM

Thank you John...all great info.

I was unaware of the "surface charge" and right after charging is when I would read the volts. I do have a really good hand held volt meter and have checked the cigarette lighter meter verses a direct read off the battery. There is a slight difference....I did it to check the accuracy of the cigarette lighter meter not realizing I the difference was voltage drop.

The ironic thing is I had a year of very basic electrical engineering courses in college (RIT) many many years ago. Too bad I don't have memory cause we did learn all this kind of stuff. I'm a printer, and remember thinking why do I need this non-sense...wish I paid more attention now!

**JohnB** · 07-12-2012, 11:07 AM

Quote:

Originally Posted by jsms264

The ironic thing is I had a year of very basic electrical engineering courses in college (RIT) many many years ago. Too bad I don't have memory cause we did learn all this kind of stuff. I'm a printer, and remember thinking why do I need this non-sense...wish I paid more attention now!

Joe, pull out the text book if you still have it. The theory has not changed any...

I kept all mine and refer to them often. I was lucky, I married the women who was in the same curriculum…. So we have 2 sets. I use one at home and have the other set of techy type of books at work. However DW has wanted to throw them out more then once now… Nope, I want them… Why do you need all that stuff…. I can hear it now. LOL