Sometimes small systems are plenty

[HiTech]

Friday my wife suddenly got the urge to camp. Immediately.

All the TT has is the original Group 24 battery, 5w solar to maintain it and a 700w/1500w inverter I've never even run under significant load. I didn't really need the system to do a lot since at 103 degrees in full sun we will be absolutely doing full hook ups.

Fired up the fridge at 8 am on propane. Pupmed the over chlorainated full water tank almost dry to be ready for use. Ran the compressor from home on the inverter to air up all 4 tires and headed to work.

At noon the freezer and fridge were cold so she loaded but did not even run the fan as the camper still held the cool from overnight.

1:05 PM we headed out for Fredericksburg and wine country.

The current set up is barely above factory, but the battery was brimming with charge and the inverter did everything we would have wanted except for the AC.

I actually think it is the ability to use the microwave that will finally push me to get the Deka AGMs put in the TT. Putting them in will mean i pit in the solar charger to maintain them without cooking the, dry or leaving the discharged. Other than the microwave though, there is just no burning need for us at the moment.

Now if I went crazy and got enough batteries and inverter to run the AC for an hour 15 times a year, that would he a horse of a different color.

😉

Jim (sipping a nice glass of 2010 Brennan Dark Horse)

[HiTech]

You can get the info from the discharge curves for the battery. My East Penn Batteries match the factory curves well (even outperfom them a bit). No idea if there is a BCI standard for this. Seems like many tests end at 10.5v

Lol O&S!

Jim

[full_mosey]

HiTech;

Last year, I used my 79AH Deka to boil a qt of water with an inverter and a 900+W elec kettle in 7 minutes. The kettle whistled at 11.6V. Over a few minutes, there was a rebound to 12.37V.

That equates to a C1 draw of 900W/11.6V = 78A from a 3+yo 53lb 79AH when new battery. That is encroaching into CCA territory. AGMs are all hybrids. This means flexibility in switching between low and high draws.

With GCs, you cannot handle high draws like C1 and keep your inverter running. Is there a BCI rating system that give any guidance on this? All of the BCI tests I have seen use low volt thresholds way below any inverter LVD ratings. I want to know what is going to happen if I draw constant Watts, not constant Amps.

With GCs, high draws are handled by adding batteries to divide the draws between multiple batteries so that the draw per battery is reduced to a low draw. For example, the 78A draw in my test might be spread across 4 x GCs at 20A per battery. IOW, with GCs you transform a high draw into a low draw by adding batteries until you arrive at a low draw.

HTH;
John

[HiTech]

AC to 72. Ahhhhhh.

Actually what I need to run the Microwave the way we use it is first and foremost AMPS, given I'm not cooking a turkey but mostly warming up food from the fridge. Others may use theirs differently.

AGMs generally have a huge advantage running high inverter loads like a microwave. Amp hours are not amp hours and not all the same to an inverter. Watts are watts though. The voltage profile of most AGMs means that their amp hours are delivered at higher volts, meaning they drain slower (because of making the watts with more volts and fewer amps) for a fixed number of watts provided to an inverter.

Their internal resistance is generally lower as well (especially in parallel vs series or series parallel) which means lower Peukert losses for a given load from a given amp hour rated bank.

Lastly they have more useable amp hours on an inverter than many non-AGMs. My AGMs stay above 11.0 volts down to 90% discharge for most currents, which means I can use the inverter at any point in the discharge cycle, not just a portion of the way through.

Jim

[wa8yxm]

What you need to run the Microwave is AMP HOURS.. AGM's have no advantage (or disadvantage with one exception) over other types of batteries when it comes to amp hours (the exception is Optima which has 60% of the capacity of other types of the same form factor).

Though I will admit AGM MIGHT (emphasis there) be a bit easier to recharge and seem to hold the charge better (less internal self discharge) still what you need is AMP HOURS.

And the amp hours per pound is the same for all battery types (Even optima which are 60% as heavy as other batteries of the same form factor).

[HiTech]

O&S it is 106 degrees out. Seriously no interest in not having the AC on. Spent most of our time outside, but once you feel hot and want some AC, nothing else will do.

Some people wilt in that kind of heat, others tent camp in it (over 20 tents with no AC!). We are in the middle. We don't let the heat stop us from going where we want or doing what we want, but that means full hookups for us so we sleep well or have a cool nap.

We tent camped a lot in the old days including in Orlando in August for our honeymoon 30 years ago. We like some creature comforts now.

Roy how long is your pop up when set up? Bet it's only a little shorter than our travel trailer. I have the parts for my plan B system up and running. 5 minutes packing and it would be in the back of the pickup. I just find too much interesting with them to relegate them to spend most of their life in storage with the RV. Some part of me wants to see those panels making power every day and actually doing something with it instead of charging for 10 minutes and calling it quits, where a 5w panel will do just as well.

Mena I love the simplicity of that. Would make a 48v bank and inverter really simple. I really don't have any special like for the 12v systems in my camper vs 110v. If I had been able to order appliances that could run efficiently from propane for hot water, fridge and heat, I would have gladly paid the energy loss of an efficient small inverter to not run any 12v.

My system is first and foremost a back up system in case power goes out, or we have to bug out, to run a fridge for medical supplies. I have found so far it has had more use at the house than on the RV.

I have been considering making it into a portable kit instead of RV mounting it. The Unisolars are very light and roll up easily.

Using the Unisolars and AGMs for other things in the camper is easy and fun to think about, but for the way we camp, really I only need one group 24 battery and 5 watts of solar in the RV itself.

Jim

[mena661]

Almot wrote:
Planning, yes. And habits/whims. I used to do 3 weeks wilderness trips in a kayak, no stores on the way. Had full balance of meat protein (no hunting allowed, and fishing wasn't good), and the use of propane stove 3-4 times a day. Batteries? Let me see... 6*AAA, 8*AA. No solar, and there was not much need to carry small charger - could've easily carried a double amount of batteries if I had to.

Done this myself plenty of times (been camping since I was in the single digits) with the only batteries being for back up flashlights (used propane lanterns primarily). Good times! Now I RV. Still tons of fun!

HiTech wrote:

I also like the idea of batteries plus Inverter external to the RV like we have been discussing in the other thread. Seems like a small bank or even single break away battery might be enough for me on the TT! With solar, AGMs and inverter in the truck.

I have been thinking about doing something similar but different. 😉 Battery bank feeding inverter and everything in the rig (the house portion) runs from the inverter. No 12V, only 120V though. A less complicated way (to some) would be keeping the 12V side but I'd find it simpler to eliminate the dual power sources. Alternator and solar would connect to the batteries directly as they are now.

[Almot]

Planning, yes. And habits/whims. I used to do 3 weeks wilderness trips in a kayak, no stores on the way. Had full balance of meat protein (no hunting allowed, and fishing wasn't good), and the use of propane stove 3-4 times a day. Batteries? Let me see... 6*AAA, 8*AA. No solar, and there was not much need to carry small charger - could've easily carried a double amount of batteries if I had to.

[RoyB]

Camping for us is to have all the PLAN Bs we can think of... We are smaller than your foot print wise and really enjoy it...

We can stay out for a good two weeks and run all of our toys everynight with the game plan of having enough battery capacity to do it and a fool proof way to recharge the batteries the next mornings to let us keep doing it all over again... About the only thing we do without is Air Conditioning...

It does take alittle planning however to make it work SUCCESSFULLY
Roy Ken

[HiTech]

Have some in mind but you know, camping comes first.

I was thinking about maybe some kind of flexible battery box that could accommodate a variety of batteries over time, and make changing them out easy.

I also like the idea of batteries plus Inverter external to the RV like we have been discussing in the other thread. Seems like a small bank or even single break away battery might be enough for me on the TT! With solar, AGMs and inverter in the truck. Hook up would be the AC power cord plus a short heavy gauge DC-DC connection between battery banks to avoid conversion losses.

Sipping coffee in the TT after a nice weekend in wine country.

Jim

[hmknightnc]

Dang, I was hoping for one of your experiments