I figure I am going to have a lot of them, so I better put all in one thread :B.My situation:- I mainly want solar for running residential freezer and fridge, maybe also for charging my shave ice machine batteries. I like to carry a lot of frozen food.- I don't have a propane system in my rig. No RV fridge, no CO2 alarm, no hot water, no furnace. Stove uses canisters.- I do have a 300watt space heater that I run a few times a year, usually for 5 minutes but sometimes for 30 if I have the juice.- I have a 600watt microwave but I don't really expect the batteries to handle it. Shore power or genny.- I have an ex650 genny. I also have an alternator connection but I usually don't drive much in a day.- I am getting a bigger van, and am going to be spending some time in SoCal setting it up. I see there are lots of used solar items there on craigslist so I might buy some.- I have my killawatt meter with me but I do NOT have my larger freezer, so I have to make some guesses about usage. - My small freezer draws 65watts, unknown startup amps. My peak usage(shave ice charger, lights, mattress warmer, electronic devices, etc....) is about 400watts. In 24 hours of average use, including shave ice machine, I use about 60 somethings, based on notes from a test last summer. I get confused about units. Watt-hours? Looking online, larger freezer is guesstimated to draw another 200watts. So maybe make that 60 into a 90 or 100.I may edit this OP if it becomes clear I have left out an important detail.I am grateful to all of you for your knowledge and help!

Starter questions:Should I avoid PWM, is it a dead technology?If I get MPPT, does it not matter AT ALL what voltage a panel is? E.g., could I use a 30-40v residential panel? Would that have other drawbacks? Wire size? Sturdiness?Are these the telecom batteries y'all talk about? Are his 145aH Dekas ok?What do you all think about 2 of his Dekas, plus my current house battery (AGM, unknown vintage, nominally 150aH but probably not that now, I am afraid to test it because testing killed its twin, runs all my non-freezer non-shaveice loads without batting an eyelash.)? And 1 or 2 225-300watt used panels?

Naio, please remember this..."THERE ARE NO STUPID QUESTIONS! ONLY STUPID ANSWERS AND STATEMENTS!"12-volt rated solar panels are getting ridiculously expensive. Simply not worth the money. Like choosing a $50,000 40 mpg car solely for economy, rather than a 30 mpg car for $30,000Meaning, go with MPPT then play jigsaw puzzle on your roof, trying to fit panels.

Naio wrote:Are these the telecom batteries y'all talk about? Hard to tell both from the description and the link he provides.They look like 2v batteries. Not 12.Naio wrote:If I get MPPT, does it not matter AT ALL what voltage a panel is? It always matters. The controller specs will tell you what the acceptable voltage is.I don't know if a question can be called stupid, but there are plenty of lazy ones.

Somethings= AH (Amp Hours). That which battery capacity is measured, and the draw of any given load if run for 60min.

2oldman wrote:Naio wrote:Are these the telecom batteries y'all talk about? Hard to tell both from the description and the link he provides.They look like 2v batteries. Not 12.Naio wrote:If I get MPPT, does it not matter AT ALL what voltage a panel is? It always matters. The controller specs will tell you what the acceptable voltage is.I don't know if a question can be called stupid, but there are plenty of lazy ones.12v @149Ah, the 2v spec is per cell for charging (where do you measure that?)Haven't priced batteries out lately but $150 for a 150Ah used battery of unknown condition seems steep. It's heavy tho..

Stupid battery and solar questions | Good Sam Community

124 Replies

landyacht318
Explorer
Jun 05, 2016
Naio, Yes it is a custom welded battery box, It can fit 2 group 27's side by side, right now just one group 27 AGM resides there.

I have a hatch in the floor in a cabinet behind the drivers seat, to lower battery into. Checking electrolyte levels was a bit of a chore and contributed to the demise of flooded batteries.

When i recently attached my Battery temp sensor i found the AGM terminals needed attention after 18 months without looking at them:

I reterminated some cables with better thick walled ring terminals and made the brass shine like gold before reassembly.
Almot
Explorer III
Jun 05, 2016
pianotuna wrote:
Mex is right about the minders. (I.E. not useful and probably harmful).

I admit that sometimes skip his battery lectures, to protect brain from overloading :)

How a minder - if it has 14x hump and subsequent 13x floating - can be harmful? This is what most chargers do, all kinds - fuel powered, 120V, or sun.

My pretty sophisticated controller does this too, though both 14x and 13x are set up accordingly to my battery specs, and duration of 14x stage is auto-adjusted by controller accordingly to SOC history. I realize that minders are not that sophisticated, and also, they don't shut down for the night.
pianotuna
Nomad III
Jun 05, 2016
Mex is right about the minders. (I.E. not useful and probably harmful).
pianotuna
Nomad III
Jun 05, 2016
Hi Naio,

Memory is never quite to be trusted. I have a log book that I use to track what I've done. (It keeps me from doing things twice! lol)

Flooded batteries need to be looked at for electrolyte levels between once per month and once per year depending on the charging method and age. The older they get the more care they demand. I managed 9 years on four Walmart Marine jars, and 6 years on three Walmart Marine jars. Laying down in the snow to chek them was not my idea of a "good time".

AGM it may be worth while to inspect from time to time. The bolt down posts are less likely to give problems--but it doesn't hurt to gently tighten them. I prefer to monitor them "electronically" by noting charging rate, and voltage.
Naio
Explorer II
Jun 05, 2016
@pianotuna: I have memory problems. I know that adjustable voltage is the best, but I really do not think I can trust myself with it.

@Almot: I have some of those switches.

My concern here is with things that I cannot anticipate wanting to connect to the batteries. And maybe some that I can.

I've had a lot of chargers die on me over the years. If that happens, I bring in a low-amp backup charger and clamp it onto the batteries individually, so they don't sit uncharged while I wait for a new charger (which can be a while, if I am not somewhere where I can get mail).

What do you guys do instead?

Some examples of un-anticipate-able needs from the last few months:

1. My cat got a prescription for meds that needed to be kept in the fridge. I wired up a 12 outlet so I could use a tiny fridge.

2. A battery minder marketed for AGM went on sale, and I got it and hooked it up.

3. Some months later, Mex said that minder was not a good idea after all, so I unhooked it.

Do you guys really go years, or decades, without touching your batteries, even to see if the connections are still good?
Almot
Explorer III
Jun 05, 2016
It is not different with big AGM bank, but can be different in small rigs.

People in trailers and 5-ers mount battery selector switch, sometimes 2 of these, if they want to isolate some battery at some time. Inverter is often wired directly so they have all the outlets available. I don't have inverter wired directly, but the outlets in my mid-small trailer are everywhere - where I need them and even where I don't.
pianotuna
Nomad III
Jun 05, 2016
Hi Naio,

I can only tell you what I would do in your shoes.

There are adjustable power supply type chargers that have adjustable voltages. I would do that--and save for a fancy inverter charger.
Naio
Explorer II
Jun 05, 2016
pianotuna wrote:
I would not do 14.4 in the summer time. Much safer to use 13.6.

What is the time comparison? If I do the bulk charging at 13.6, will they take a lot longer than 14.4?

Sometimes I worry about asking questions, because of the common saying on this site that people have already made up their minds before they ask their questions. But I have not. And this IS supposed to be the thread for dumb questions :B.
Naio
Explorer II
Jun 05, 2016
I can't put them behind the seats because that's where my ice machine fits.

I have used AGM batteries for 20 years or so. But I do find I am always wanting to get at them for one reason or another. To attach a new kind of outlet, or to top charge them individually. Maybe it's different with a big bank.
westend
Explorer
Jun 05, 2016

Suggestions welcome.

Can you squeeze them in behind the seats? You can break them into pairs and connect the pairs with large cables. Also, most AGM's can be oriented in any direction except valve down (upside down).

What type or model of van are these going into?