Battery capacity vs. weight

[larry9000]

I have a 2006 16' International CCD with a single AGM 80AH battery. I'd love to double the capacity. But my problem is hitch weight. I'm already at the 500# tongue weight limit for my 2016 4runner. So, I'm considering options:

-Just add another battery, 56 pounds. Assume the WD hitch gives me some margin.
-Since the two batteries weight 112 pounds, and the two propane tanks weight 74 pounds together, move batteries to rear and propane tanks forward on the A-frame tongue to get the most leverage for the heavier items. 10' from axle to hitch means that every foot backwards is a 10% tongue weight savings.
-Move AGMs to the inside? There's not much space under the drivers side dinette cushions, but it would be possible to put AGMs under passenger cushions, replacing the pull out storage drawer. I don't like giving up storage on a Bambi, though.
-Lithium Cells? I think you get more capacity/weight, but I'm reluctant to pay the big bucks needed for a Lithium upgrade.
-Other options????

I've measured our usage, and we use 25AH/day, about the same that we can charge back with our 50W solar cell on sunny days. I'm worried about shorter and cloudy days. We're limited to 2 days max if we can't recharge.

Any suggestions?

[uncle_bob]

Hi

Lithium's will do better in terms of power per pound. They also are a bit more "inside compatible". Lead acid (flooded or AGM) need to be vented to the outdoors. Cost wise, yup, you spotted that already. Since you can run lithium's essentially to zero and can only run the lead acid's to about 50% capacity, you get away with fewer amp hours of lithium. If you accept the claim that they last twice as long, that also helps a bit on the upfront cost. Even more so if you accept the 3X or 4X claims (yikes !!).

If your daily usage stays at 25 AH, a 100AH lithium stack is probably gross overkill. Better to spend a bit more on solar so you are more likely to get a charge. Portable solar is one thing to consider. 50W solar at 80% gives you about 3.2 amps at 12.5V. That barely gets you to 25.6 AH. Any day you miss out on will never get made up. A 100W portable panel isn't all that expensive ....

Another thing to consider (if you don't have one) is a small inverter generator. They are very quiet and pretty small. A 1KW version will charge your hypothetical 100AH / good for 4 days stack in just over an hour. One hour of run every 4 days isn't *that* much hassle.

Bob

[larry9000]

Originally Posted by uncle_bob

Hi

Portable solar is one thing to consider. 50W solar at 80% gives you about 3.2 amps at 12.5V. That barely gets you to 25.6 AH. Any day you miss out on will never get made up. A 100W portable panel isn't all that expensive ....

Another thing to consider (if you don't have one) is a small inverter generator. They are very quiet and pretty small. A 1KW version will charge your hypothetical 100AH / good for 4 days stack in just over an hour. One hour of run every 4 days isn't *that* much hassle.

Bob

Thanks, Bob. Your 25.6AH calculation is almost precisely the best solar charging I've had in a day. So, summer days I'm pretty good. But with winter, with more furnace blower time and fewer hours of daylight, the balance can't be maintained. Yes, I've considered a portable solar unit for exactly that reason- more power and the ability to aim the panels.

I'm very impressed with how much lighter lithium batteries are. I could increase capacity and lessen the weight. I'm not sure where I'd put a Li battery in the Bambi. Outside on the tongue where the AGM is now is an easy solution, but from what I've seen Li batteries don't like being charged at below freezing temperatures, a certainty in Colorado mountains in fall. So, inside where the trailer is heated seems preferred.

[switz]

We installed a 300 amp-hour lithium inside our 2015 23D International Serenity just forward of the street side front tire wheel well. It weighed just 84 pounds which is much less than the two stock lead acid batteries that were in the front battery box. One can safely use 85% to 90% of the capacity of a lithium battery, whereas a lead acid is good for 50% of it's capacity.

We do have five 100 watt solar panels on the roof of our 23D.

[uncle_bob]

Hi

If indeed, your 25AH turns into >50AH as the seasons change, a 100AH stack isn't going to be right for you. Furnace blowers pull a lot of power. Mounting the lithiums in the trailer is an option. It may or may not be what you want to do.

Simply accepting that the whole trailer has issues below 32F is another option. If it's still below 32 at noon, keeping the water systems happy gets to be a big hassle. You are not going to be charging the batteries off of solar at midnight. In the sort of conditions that the rest of the trailer is designed for, the batteries will be above freezing when you have solar to charge them.

Lead acid batteries have charging / capacity issues below freezing. If you want to get a good charge on them, you will need a charger that can monitor the battery temperature. That only gets as much into the battery as it will accept. The 20% or so capacity decrease is just something you put up with.

If you are out as winter sets in, managing things gets iffy. The weather man is not always 100% accurate in the 1 week forecast. Freezing the pipes that are buried in the walls ... not much fun. Knowing when 29 degrees and 13 mph winds from dead on to the hitch is a lot worse than 22 degrees and wind broadside (or vice versa) ..... nobody knows that stuff. Airstreams (like most RV's) are tough to run when it's cold for extended periods.

Lots of fun !!

Bob

Bob

[TinkersToy]

Originally Posted by larry9000

I have a 2006 16' International CCD with a single AGM 80AH battery. I'd love to double the capacity. But my problem is hitch weight. I'm already at the 500# tongue weight limit for my 2016 4runner. So, I'm considering options:

-Just add another battery, 56 pounds. Assume the WD hitch gives me some margin.
-Since the two batteries weight 112 pounds, and the two propane tanks weight 74 pounds together, move batteries to rear and propane tanks forward on the A-frame tongue to get the most leverage for the heavier items. 10' from axle to hitch means that every foot backwards is a 10% tongue weight savings.
-Move AGMs to the inside? There's not much space under the drivers side dinette cushions, but it would be possible to put AGMs under passenger cushions, replacing the pull out storage drawer. I don't like giving up storage on a Bambi, though.
-Lithium Cells? I think you get more capacity/weight, but I'm reluctant to pay the big bucks needed for a Lithium upgrade.
-Other options????

I've measured our usage, and we use 25AH/day, about the same that we can charge back with our 50W solar cell on sunny days. I'm worried about shorter and cloudy days. We're limited to 2 days max if we can't recharge.

Any suggestions?

I replaced my lead acid with an 100AH LiION battery that weighs 28 pounds. Our sales-rep was Will Olney at Battle Born Batteries, 4818 Longley Ln Reno NV 89502. They also make a 50AH.

Price include FedEx shipping are reasonable and they ship very quickly.

I like the fact that they are manufactured in the USA. So far it has worked quite well for us during our Boon Docking.

It has the battery management system built so our existing multi stage charge unit works with no modifications. I also use a 100W solar panel during boon docking with no power issues.

[GammaDog]

I had a similar issue with our 25' FB (which has two group 24 batteries) and the Tundra. I wanted more battery capacity (especially for cold nights w furnace running while boondocking) but I didn't want the expense of Li ion, the lost space of moving to AGMs and locating them in the trailer or the weight of two 6 volts. My solution was to add a 12 volt quick disconnect fitting to the existing battery bank, buy a third group 24 and a battery box (total cost under $150). When Im going to need the additional battery power I connect the additional battery a day before to top off its charge. It rides wherever I want it (usually inside the trailer near the rear where it actually reduces tongue weight). It connects or disconnects in 10 seconds. It has two 12 volt connectors... the second allows me to hook in my solar suitcase even when all three batteries are in use. Cheap... easy... effective... works for me.

[DaveP]

Larry,

Do not rule out the AGM batteries. Lifeline AGMs do not need to be vented to the outside and they can be mounted on their sides inside the trailer. You get a lot of capacity per battery and a 7 to 10 year life if you take care of them. They weigh more to get capacity (all lead acid batteries do) and they are more expensive than standard deep cycle batteries, but they are a lot less expensive than lithium (at least upfront cost). Take a look at the Lifeline web site at http://lifelinebatteries.com/products/rv-batteries/. You could put in a 12v system or 6v system. Two GPL 4CT would give you a 110 AHr capacity at 50% discharge at a cost of less than $600 delivered to your house. There are a lot of other alternatives.

Good shopping!

[uncle_bob]

Hi

Any lead acid battery, AGM or flooded *can* produce hydrogen gas when over charged. The only question is how much of an overcharge it takes to get there. The "do not require ventilation" statements on AGM's are always followed by a note buried somewhere about "normal operation". Best practice is still to vent them. That way in the case of a problem, you don't create an even bigger problem. RV fires are a really bad thing ....

One of many references on AGM's in enclosed spaces:

http://www.boats.com/how-to/sealed-b.../#.WV1FccaZPMU

Google canl come up with a lot of others.

Bob

[DaveP]

Hi Bob,

Per Lifeline, you do not want to mount their batteries in a “sealed” container, but they only require minimal venting so hydrogen gas does not build up.

Per your article (link), “The good news here is that hydrogen mixes with air very readily and so not too much ventilation is required.”

Lifeline – “Both AGM and Gel batteries utilize oxygen recombination and pressure relief valves to minimize water loss and allow maintenance-free operation. That is where the similarities end. AGM batteries have the advantage of being mountable in any orientation without capacity loss, have lower internal impedance to support high load currents, and have better capacity at lower temperatures.”

Lifeline - “Do not install Lifeline® AGM batteries in a sealed container or enclosure. During storage, charging, or discharging hydrogen gas can be released and must be ventilated to prevent the possibility of ignition and/or explosion.”

Lifeline – “This notice is to clarify to shippers and transporters that the batteries listed are packaged and marked in accordance to 49 CFR 173.159(d) and are determined to be in compliance with DOT HMR49 Non-Hazardous Materials, the International Civil Aeronautics Organization (ICAO) and the International Air Transportation Association (IATA), Special Provisions S.P.A67 & A48. Therefore, these batteries are not restricted for shipment by air or any other means of transportation and are exempted from the hazardous material category.”

The point is, you can safely install AGMs in a trailer, just do not put them in a sealed area/container. Provide adequate ventilation so the small amount of hydrogen gas does not build up.

Not trying to start an argument, but stating the other point of view. Let each decide for himself/herself.

[larry9000]

Originally Posted by GammaDog

My solution was to add a 12 volt quick disconnect fitting to the existing battery bank, buy a third group 24 and a battery box (total cost under $150). When Im going to need the additional battery power I connect the additional battery a day before to top off its charge. It rides wherever I want it (usually inside the trailer near the rear where it actually reduces tongue weight). It connects or disconnects in 10 seconds. It has two 12 volt connectors... the second allows me to hook in my solar suitcase even when all three batteries are in use. Cheap... easy... effective... works for me.

Gammadog- I asked for other ideas, and you came up with a logistically clever one! I like it. I assume you hook the extra battery up with a set of standard battery clamps. I also like having it ride just in back of the rear axle. I even have room in my rear storage compartment. Once at camp, pull it out and attach. Clever.

Is there any issue during traveling that the hitch battery is being charged by solar, while the interior one is dormant? Or any consequence that the usage between the two batteries won't be completely symmetrical?

[larry9000]

Originally Posted by DaveP

Larry,

Do not rule out the AGM batteries. Lifeline AGMs do not need to be vented to the outside and they can be mounted on their sides inside the trailer. You get a lot of capacity per battery and a 7 to 10 year life if you take care of them.

Thanks, Dave. AGM is the still default for me. After all, that's what I have now, and AGMs have nice properties. I just need to figure out how to address the hitch weight issues.

[uncle_bob]

Originally Posted by DaveP

Hi Bob,

Per Lifeline, you do not want to mount their batteries in a “sealed” container, but they only require minimal venting so hydrogen gas does not build up.

Per your article (link), “The good news here is that hydrogen mixes with air very readily and so not too much ventilation is required.”

Lifeline – “Both AGM and Gel batteries utilize oxygen recombination and pressure relief valves to minimize water loss and allow maintenance-free operation. That is where the similarities end. AGM batteries have the advantage of being mountable in any orientation without capacity loss, have lower internal impedance to support high load currents, and have better capacity at lower temperatures.”

Lifeline - “Do not install Lifeline® AGM batteries in a sealed container or enclosure. During storage, charging, or discharging hydrogen gas can be released and must be ventilated to prevent the possibility of ignition and/or explosion.”

Lifeline – “This notice is to clarify to shippers and transporters that the batteries listed are packaged and marked in accordance to 49 CFR 173.159(d) and are determined to be in compliance with DOT HMR49 Non-Hazardous Materials, the International Civil Aeronautics Organization (ICAO) and the International Air Transportation Association (IATA), Special Provisions S.P.A67 & A48. Therefore, these batteries are not restricted for shipment by air or any other means of transportation and are exempted from the hazardous material category.”

The point is, you can safely install AGMs in a trailer, just do not put them in a sealed area/container. Provide adequate ventilation so the small amount of hydrogen gas does not build up.

Not trying to start an argument, but stating the other point of view. Let each decide for himself/herself.

Hi

Trailer in storage with the batteries on charge inside the trailer .... bad idea, even with AGM's.

Bob

[dznf0g]

...or you could get a small 1000 watt generator and top off whenever needed.

[slowmover]

Electrical use. Needed, and desired.

Needed: Furnace fan, and water pump.

Desired: Anything else. (Unnecessary).

As with tow vehicles, desires get ahead of need.

To recreate a house, buy a diesel bus with a 12.5Kw genset.

To go camping, exercise some restraint.

Gensets and solar add marginal value at high cost, complexity (non-durable), and with genuine safety risks.

Sure, we all love our comforts. Physical and psychological.

The convenience of a car is in avoiding public transportation. One doesn't need a four ton farm vehicle to accomplish this.

The "convenience" of a camping trailer is to hopefully avoid the public altogether. One also does not need that four ton farm vehicle.

Choose the camping locale to avoid modification of air temperature.

Choose to avoid "the sanitized public" of media, and telephone.

One doesn't need electricity to store or prepare food. Nor to clean or bathe.

Start from basics.

Step One is separating need and want.

THEN are modifications made reasonable.

If one just has to spend money on the trailer, then (again) reason portends that safety trumps convenience. Anti-lock disc brakes outweigh any solar electric or lithium battery installations.

Get stuff in order.

.

[GammaDog]

Originally Posted by larry9000

Gammadog- I asked for other ideas, and you came up with a logistically clever one! I like it. I assume you hook the extra battery up with a set of standard battery clamps. I also like having it ride just in back of the rear axle. I even have room in my rear storage compartment. Once at camp, pull it out and attach. Clever.

Is there any issue during traveling that the hitch battery is being charged by solar, while the interior one is dormant? Or any consequence that the usage between the two batteries won't be completely symmetrical?

I'm not a battery expert, but those on the Forums who are say that there can be issues with a battery bank containing a mismatched mix of batteries. They point out that mixing batteries of varied age, size, type, state-of-charge, etc. can all lead to shortened battery life. I believe them. However, I'm a pragmatist, philosopher and (dare I say?) traveling adventurer. When it was 23 degrees in Utah last year and we were traveling with our 18 year old dog (who didn't make 19... rest her furry soul) I was delighted to have enough battery capacity online to keep the heat at 65 degrees and not discharge the bank below 50% state-of-charge (the point at which those same experts say permanent damage is done to a flooded lead/acid battery like the Interstates I have). For the few times a year I need the capacity, I'm comfortable with this solution. If I have to replace the batteries in three years instead of four but I don't have to tell my wife "Honey, the dog froze overnight, but the trailer batteries still have years of good camping in them", I'm good with that. Especially since I keep my truck within tongue weight specs and didn't spend a year's worth of gas and campground budget to get the battery capacity I needed.

I would not mix types (e.g.: some flooded, with some AGM and I certainly wouldn't mix Lithium with anything else), and my three batteries are all Interstate Group 24 of the same age

As for clips versus other connectors, I would strongly prefer not to use clips. In my opinion, they simply do not make reliable contact and could even be jarred loose when unattended. An alternative to adding quick disconnects (I think I have pics of the Anderson Power connectors I use in my gallery on the Forums... private message me if you don't see it and I'll post a better view) is to see if your battery has a threaded steel post connector versus the type cars usually have with the lead lugs and big clamps. When I added my third battery, I didn't have time to add the Andersons..l they came later. What I did was to get two battery cables with eyes on each end. I'm thinking they were 24" zero gauge... something like that. I hooked them to the third battery and coiled them in the battery case so they wouldn't contact one another. When I needed the battery, I'd open the battery box on the trailer, unscrew the nut from a negative post on my batteries, hook the negative cable from the third battery and replace the nut. Repeat for the positive side. Voila! That was a very solid connection!

(From the "more than you asked for" department: I have a similar view on the fridge and leveling... sure, being even a bit out of level can shorten fridge life according to the "fridge experts". I believe them, too. However I'm not in a contest to see if my fridge can make it to the Smithsonian Museum. My goal is to see America up close... stay in places where people with airplane tickets, rental cars and hotel rooms can't go (look at Firehole Canyon, WY in the Ashley National Forest for a modest example)... and return home without having contracted ptomaine poisoning. We go places where the very best possible site might be a degree or two out of level. The fridge still works. If it dies one day, but we're still well fed and healthy I'll get a new one and keep the memories of where we ate from the old one. For us, a shortened life of the things that can be replaced is acceptable if it lets us get out and see America and do so safely.)

I hope that helps!

[larry9000]

Thanks Gammadog,

Got it. I looked at your photo as well. Since I will be planning ahead before our next trip, I'm likely to add 50A Anderson connectors and make adding the 2nd battery easy. As long as the cables between the batteries are heavy gauge, the solar charger (I have 50W factory install on the roof) should charge the two pretty evenly. The AGM I currently have was new this year, so if I get one another in the near future they should be of approximately the same age. I guess if I really worry about the two batteries having different experiences, I can swap the role of the two batteries occasionally (the "permanent" mounted battery becomes the second battery for a bit, etc.)

You have a nice setup with the Renogy panels. I'm leaning that way as well, adding 100-200W of portable solar. Since I don't have a truck bed to store them in, I'm also playing with the idea of getting flexible panels that will slide under the bed. Of course, I have the whole "building the frame" challenge if I do that.

I liked your idea of using magnets to attach the controller to the A frame. I need to think about how much weather protection I need. In theory, I won't be charging in the rain, but Colorado mountains often produce short afternoon rain showers.

Back to the topic at hand: I need to decide on the front battery box design. I could have two battery boxes, and plug in between them. Or one large battery box, with the permanent one mounted securely inside. I'm leaning to the idea of two boxes. The mobile battery would be carried by a strap and set inside while moving. Then returned to its own box while camping. Just one more task on the arrival and departure checklists.

[larry9000]

Thinking about this some more, I may go with the eyelet method of attaching the second battery. I can mount the cables to the permanent battery, and thread them into the empty battery box, with some sort of method to keep them apart. When I bring in the second battery from the trailer, I'd just use some heavy duty brass wing nuts to attach the two cables to the second battery. Very heavy duty cables with no connectors in the path, but easy to attach.

[uncle_bob]

Hi

The biggest practical risk on a lead acid battery with deep discharge is that a cell shorts when you charge it back up. That's essentially a "game over" situation for the battery. The likelihood of it happening is very much a "that depends" sort of thing. There is plenty of evidence in posts here on the forum that shorted cells are a very real thing.

If you are out at 23F with a normal battery bank (outside the trailer) (and no temperature probe on the charger) be very careful about battery management. The batteries will only have about 80% of the capacity you expect if you fully charge them. The gotcha is that 12V is no longer the 50% charge point. The "magic voltages" all move higher at cold temperatures. Your thresholds on the charger/converter are no longer high enough to fully recharge the battery at cold temperatures.

Tossing a warm "just out of the basement" in with a batch of 23F batteries produces "interesting" results. The batteries are not / can not be sitting at the same voltages. The cold batteries go dead while the warm one is loafing along. If you pair up batteries, let them get to the same temperature before you start doing stuff with them. That can take a while.

None of this says you *can't* do it. It's simply a caution about what to watch out for when you *do* do it. It's also a strong hint that a temperature probe on the charger is a real good idea if you do this kind of thing regularly. The probe usually is cheap. Running the wires is usually a pain.

Bob

[larry9000]

Originally Posted by uncle_bob

Hi

If you are out at 23F with a normal battery bank (outside the trailer) (and no temperature probe on the charger) be very careful about battery management. The batteries will only have about 80% of the capacity you expect if you fully charge them.

... If you pair up batteries, let them get to the same temperature before you start doing stuff with them. That can take a while.

Bob

All good points. I was imagining connecting the 2nd battery once we arrived at a campsite, not waiting until the first battery was low. So I wouldn't be pulling out a warmed battery per se, but there still could be a bit of temperature difference. Yes, a temperature probe seems like a good idea, 2nd battery or not. One advantage of the two battery strategy above is that it would be easier to find a battery with a bad cell, as you could measure the two voltages before combining them.

After considering this idea for a while it occurred to me that in place of carrying a 56 pound battery back and forth, I could be carrying a 50 pound propane generator instead. Hmmm...