Greetings and Off-grid advice requested!

Rossman

Hi guys,

Been reading here for awhile but have yet to post. Really enjoy the forums here, there is a lot of useful information here and helpful people willing to share knowledge.

I've got 25 acres in Ontario, Canada, that has no hydro access. I'll be building a house up there at some point but in the meantime just camp out in an old motorhome.

At this point I am trying to come up with a solid system that will keep the RV's "house" batteries charged. These are two Interstate SRM-24 12VDC wired in parallel to give me ???Ah (not sure what this is, I didn't understand the Interstate spec sheet)?

Anyway I'm thinking to perhaps purchase an inexpensive MPPT charge controller (Maybe Sunsaver MPPT, 15A?) and a couple 240W solar panels? If I've understood correctly, and the max. battery I should draw is 50% then I would like to assume I'm using that full 50% each day and have a system guaranteed to meet that. Is what I suggested suitable? I would prefer to be slightly overengineered than under.

Thanking y'all for any and all advice!

Cheers,
mark

Cariboocoot

Re: Greetings and Off-grid advice requested!

Welcome to the forum.

That spec sheet is confusing because those aren't "true deep cycle" batteries, they're the RV/Marine type. Not best suited to RE use. That said, they're about 85 Amp hour in the way we usually refer to them. Two in parallel: about 170 Amp hours.

A couple of 240 Watt panels? 480 Watts on 12 Volts would yield about 30 Amps maximum so the MS MPPT 15 wouldn't handle it. You would need MPPT with these panels as the Vmp on them is bound to be around 30.

The good news is you don't need 30 Amps to charge 170 Amp hours of battery. One of those panels on an MS MPPT 15 would do fine.

Rossman

Re: Greetings and Off-grid advice requested!

Thanks very much for your prompt reply!

Yeah, I understand that these batteries are not ideal. They are just kind of getting me through for now

Looks like things will be cheaper than I expected I guess!

Thanks!

westbranch

Re: Greetings and Off-grid advice requested!

You haven't told us about the loads and the time of year you plan to use the RV??? Big difference summer to winter or shoulder seasons.
you should not plan on using 50% daily as that can be hard on the batteries, it will shorten their life ...

Rossman

Re: Greetings and Off-grid advice requested!

Yeah, I'm sorry I did not provide very much information. It's because I don't know it

In winter I take out the batteries and bring them back home, store in the basement. But I will take up there in the spring and leave until fall next year. Just trying to plan for something so that they stay in good orde when I am not there, so when I get there they will be ready to go and healthy.

I haven't quite worked out all the wiring in the RV and don't have much idea as regards to the loads. When I was up on the roof last I noticed a small maybe 15" square solar panel but I don't believe it's doing much if anything. Biggest problem right now is the in built gennie does not fire up to top up the batteries or handle the AC loads, so while I figure out that problem, I thought I would throw on a panel or two to maintain the batteries in good order and get a bit more familiar with solar in preparation for full time off grid living (when the zombie apocalypse happens).

I would like to replace the batteries with proper deep cycle at some point but dimensions are a big concern, I only have so much space under that step...

Attachment not found.

waynefromnscanada

Re: Greetings and Off-grid advice requested!

Rossman wrote: »

In winter I take out the batteries and bring them back home, store in the basement. ]

Be sure to give those stored batteries a charge at least once a month to keep them up and prevent sulfation. They self-discharge, it's normal, and can be ruined if allowed to go too low.

Rossman

Re: Greetings and Off-grid advice requested!

I have been putting my 2A/12VDC trickle charger on them once every few weeks to make sure they are holding their charge!

Thanks!

EDIT: I should say, these particular batteries are likely already kind of buggered, it's very possible they were run flat at some point since I have had them.

Rossman

Re: Greetings and Off-grid advice requested!

Is there a device I can place between the positive/negative terminal of the battery bank and the RV wiring to determine the current draw of the load in the RV?

Or, alternatively, is something like this accurate enough to determine such?

Thank you!

Blackcherry04

Re: Greetings and Off-grid advice requested!

That one will NOT do DC AMP's. You have to be careful on the specifications.

Voltage Range: 600V AC/DC; Safety Category Rating: CAT III 600V; TRMS: Yes; AC Amps: 400 amps; AC Volts: 600 volts; DC Volts ; 600 volts; Ohms: 4000 ohms; Auto Calibration: No-Recommend sending in for calibration service once every year

Rossman

Re: Greetings and Off-grid advice requested!

Thanks, any recommendations?

This might be a useful item?

Rossman

Re: Greetings and Off-grid advice requested!

waynefromnscanada wrote: »

Be sure to give those stored batteries a charge at least once a month to keep them up and prevent sulfation. They self-discharge, it's normal, and can be ruined if allowed to go too low.

Oh! Another question - I have, until now, been putting the batteries on my trickle charger individually. Should I be charging them connected together as a bank instead? I read people saying that you should keep the batteries charged similarly so perhaps this is what I should be doing?

Sorry, so many silly questions!

Cariboocoot

Re: Greetings and Off-grid advice requested!

These batteries are probably haggard so it won't matter if you trickle charge them one at a time or not. If they're still connected to each other when you put the charger on it will be both at once anyway (you'd be amazed how many people don't realize this).

A battery monitor such as the Trimetric can be a good thing indeed. But there's no point in getting one until you put new batteries in as they have to be programmed with info such as capacity, and you can't really know what that is at this point.

Those seem to be group 24 size batteries: 10 x 6 x 9 inches. That's pretty close to a GC2: 10 x 7 x 10 inches. If there's an inch of "wiggle room" all around you could put a couple of GC2 6 Volts in series in the same space and have 220 Amp hours @ 12 Volts. More capacity, fewer problems with current sharing, simpler wiring, less cells to check, and real deep cycles performance. Might be a good, inexpensive improvement for you.

Rossman

Re: Greetings and Off-grid advice requested!

Thanks for the reply! I am not familiar with "GC2" batteries?

From the picture you can see I have a bit of wiggle room left-to-right (maybe 2" overall) but I need to really get in there and measure to be sure.

EDIT: I feel like these have a good chance of fitting...

Cariboocoot

Re: Greetings and Off-grid advice requested!

Skip those Universal AGM's. Perfectly good batteries but ... more money per Watt hour than flooded and you can't check the specific gravity. Also being 12 Volts you'd have the same parallel wiring problems.

GC2 is another "size" also known at "T105". Here's an example of Crown GC2: http://www.solar-electric.com/cr225am6vode.html
You can sometimes get this sort from warehouse stores for less than $100 each. Good batteries to begin with as they are inexpensive per Watt hour, you can check the SG, and you'd probably still get 5 years out of them with care.

By all means measure the space! Nothing worse than being short 1/4" when you're trying to put 65 lbs. of battery in the hole.

Rossman

Re: Greetings and Off-grid advice requested!

Another possibly dumb question re: batteries, the current ones I have, have threaded lugs on them already for connecting the cables. I notice that some (most?) of the true deep cycle batteries have a connection like:


Do I just get a bolt and jam it through that, in lieu of getting the nice in-built threaded lug?

Cariboocoot

Re: Greetings and Off-grid advice requested!

Rossman wrote: »

Another possibly dumb question re: batteries, the current ones I have, have threaded lugs on them already for connecting the cables. I notice that some (most?) of the true deep cycle batteries have a connection like:


Do I just get a bolt and jam it through that, in lieu of getting the nice in-built threaded lug?

Yes. If the lugs are loops like that you use through bolts. Stainless steel ones if you want to get them apart again.

Rossman

Re: Greetings and Off-grid advice requested!

Cariboocoot wrote: »

Skip those Universal AGM's. Perfectly good batteries but ... more money per Watt hour than flooded and you can't check the specific gravity. Also being 12 Volts you'd have the same parallel wiring problems.

GC2 is another "size" also known at "T105". Here's an example of Crown GC2: http://www.solar-electric.com/cr225am6vode.html
You can sometimes get this sort from warehouse stores for less than $100 each. Good batteries to begin with as they are inexpensive per Watt hour, you can check the SG, and you'd probably still get 5 years out of them with care.

By all means measure the space! Nothing worse than being short 1/4" when you're trying to put 65 lbs. of battery in the hole.

Thanking you kindly. I was actually picking the sealed AGM because I fear having to check SG etc with flooded batteries.

Also does it matter if I get 12V because the parallel wiring isn't really a "problem", it's already there...? Perhaps I do not fully understand what you are getting at.

This forum should have a "thanks" button

Anyone know of a place to get those Crown batteries in Ontario, Canada? Checked costco.ca they don't seem to have anything like that.

BB.

Re: Greetings and Off-grid advice requested!

For a "good enough" DC Current Clamp meter (really a full function DMM), this one is a really good price from Sears.

Play with it on your car and learn how to use the "zero" function. DC current clamp meters tend to drift over time--And you have to rezero them every few minutes (if you want very accurate measurements). With this meter, have no current (no wire in clamp). Push the "Zero Button" until you see "zero" on the LCD. Then you should read zero amps. Now connect to a single wire and measure the current (the clamp measure the total current flow through the clamp--if you have the +/- wires both going through the clamp, the total will be zero amps).

Regarding deep cycle tab with hole... Yep, just toss a nut and bolt on there. Use some sort of anti-corrosion grease (I just get the stuff from an auto parts store). I would suggest brass nuts and bolts (lower resistance). But if you use stainless steel--Make sure you use anti-seize compound on the threads--Stainless threads are prone to galling if there is no lubrication.

-Bill

Rossman

Re: Greetings and Off-grid advice requested!

BB. wrote: »

For a "good enough" DC Current Clamp meter (really a full function DMM), this one is a really good price from Sears.

Play with it on your car and learn how to use the "zero" function. DC current clamp meters tend to drift over time--And you have to rezero them every few minutes (if you want very accurate measurements). With this meter, have no current (no wire in clamp). Push the "Zero Button" until you see "zero" on the LCD. Then you should read zero amps. Now connect to a single wire and measure the current (the clamp measure the total current flow through the clamp--if you have the +/- wires both going through the clamp, the total will be zero amps).

Regarding deep cycle tab with hole... Yep, just toss a nut and bolt on there. Use some sort of anti-corrosion grease (I just get the stuff from an auto parts store). I would suggest brass nuts and bolts (lower resistance). But if you use stainless steel--Make sure you use anti-seize compound on the threads--Stainless threads are prone to galling if there is no lubrication.

-Bill

Thank you sir! Appreciate the Sears link especially. Think I might start with that to figure out the load the RV draws and that way can be better informed as regards to new batteries, charge controller, and panels.

Cariboocoot

Re: Greetings and Off-grid advice requested!

Parallel wiring is always a problem with batteries, whether it's there already or not. The parallel paths through two batteries means they can get/give different amounts of current, which will allow different SOC in each. As such they won't "age" equally. In severe cases one does all the work while the other sits there and slowly sulphates to death.

There are fewer wires/connections/cells to keep track of with two 6 Volts in series as opposed to two 12 Volts in parallel.
Two 12's: 2 wires to connect batteries together, 12 cells to check, 6 connections minimum.
Two 6's: 1 wire to connect batteries together, 6 cells to check, 4 connections minimum.

It may not sound like much, but it is. The larger the battery bank the worse the problems of parallel connections become. But the main one is keeping the current even through both batteries. With two in series it has no choice but to be the same.

Don't fear specific gravity readings. They are your best friend when it comes to determining the actual condition of the battery. Nothing else is as accurate. Even battery monitors lose accuracy over time (batteries' actual capacity changes with time so the monitor has to be periodically reprogrammed). The sulphuric acid solution is hazardous, but it's not liquid death. I've been taking SG readings for decades and the worst I have to show for it is a few holes in some clothing.

Cariboocoot

Re: Greetings and Off-grid advice requested!

Bill, one of these days I'm going to make a note of that link and start referring to it myself.
On the other hand I wouldn't want to deprive you of the fun.

Rossman

Re: Greetings and Off-grid advice requested!

Cariboocoot wrote: »

Don't fear specific gravity readings. They are your best friend when it comes to determining the actual condition of the battery. Nothing else is as accurate. Even battery monitors lose accuracy over time (batteries' actual capacity changes with time so the monitor has to be periodically reprogrammed). The sulphuric acid solution is hazardous, but it's not liquid death. I've been taking SG readings for decades and the worst I have to show for it is a few holes in some clothing.

Thanks for your specific and detailed reply! Good to know series is that much better, will definitely look to this when the time is right to pull the trigger!

As far as the SG goes it is not the acid that I fear but more having to learn this much about batteries. I'm no spring chicken anymore my brain is already full!

westbranch

Re: Greetings and Off-grid advice requested!

here is a good table of Trojan batt sizes on page 2, http://www.trojanbattery.com/pdf/TRJN0111_ProdSpecGuide.pdf

Cariboocoot

Re: Greetings and Off-grid advice requested!

Rossman wrote: »

Thanks for your specific and detailed reply! Good to know series is that much better, will definitely look to this when the time is right to pull the trigger!

As far as the SG goes it is not the acid that I fear but more having to learn this much about batteries. I'm no spring chicken anymore my brain is already full!

Yup. I know what you mean.
But it's easy because all measurements are relative anyway.
Brand new batteries. Charge fully. Take reading from each cell. Write it down. Don't lose the paper (that's the hard part). Compare future reading to these base numbers.

Doesn't have to be "1.277 as per manufacturer's specifications". If the new, fully charged reading is "137.9 Albatrosses" it works out the same. When you get a reading of "115.3 Albatrosses" you've got a problem. If one day it comes up "Hippos" you've got a big problem.

What's more, once the system is proven to be working it isn't that big a deal so long as usage remains consistent. I check mine once a month, usually to find it's spot-on and just needs a little bit of water added.

Rossman

Re: Greetings and Off-grid advice requested!

westbranch wrote: »

here is a good table of Trojan batt sizes on page 2, http://www.trojanbattery.com/pdf/TRJN0111_ProdSpecGuide.pdf

Thanks for the link. I see that I might be able to squeeze in 2 x J250G. There are a lots of ratings in that chart, which one is typically referenced for the Ah rating?

westbranch

Re: Greetings and Off-grid advice requested!

we usually use 20 hr as it is similar to OG use patterns.

Rossman

Re: Greetings and Off-grid advice requested!

westbranch wrote: »

we usually use 20 hr as it is similar to OG use patterns.

Oh nice, so prob best for me is the T-145 Plus'...?

Rybren

Re: Greetings and Off-grid advice requested!

Rossman wrote: »

Anyone know of a place to get those Crown batteries in Ontario, Canada? Checked costco.ca they don't seem to have anything like that.

I've been looking as well and haven't found anyone in Ottawa that carries them, but I did find a place in Montreal that carries Crowns. The CR200 (200ah) are $149 and the CR225 (225ah) are $169. I can send you a link to the store if interested.

Jerry

Rossman

Re: Greetings and Off-grid advice requested!

I would love to get that link, if its against forum rules to post it here, please PM to me!

My mom's up in Ottawa and we've a cottage about an hour south of Montreal, so no problem picking it up from there. Those prices seem pretty reasonable, though not as great as some of the deals our US brothers get!

Thanks!

BB.

Re: Greetings and Off-grid advice requested!

Posting links to other suppliers that directly answer questions are fine.

-Bill

Rossman

Re: Greetings and Off-grid advice requested!

Thanks Bill! To be clear, if I wasn't in another country I would most definitely buy from this site! Prices are great and the help is also! Unfortunately the freight/customs/duties charges ruins everything!