144 HR 2fer: two people, two bikes, two kayaks

[VanGoSki]

That's looking awesome.

Couple of questions on your electrical setup.

1) It doesn't sound like you're using a B2B for charging, correct? Isolation relay maybe?

2) You mentioned several times it's (almost) never a good idea to charge from the starter battery. I'm curious why you say this. As long as you keep the charging current to 40 or 50A, you should be well within MB's guidelines for current draw. Right? I'm asking because I'm planning on this as well.

3) This is a generic question. I'm trying to figure out how long it would take to charge your battery. If your charge rate is 50A, does that mean you can charge your 300AH to 50% in 3 hours?

Thanks!

 

[sanomechanic]

That's looking awesome.

Couple of questions on your electrical setup.

1) It doesn't sound like you're using a B2B for charging, correct? Isolation relay maybe?

2) You mentioned several times it's (almost) never a good idea to charge from the starter battery. I'm curious why you say this. As long as you keep the charging current to 40 or 50A, you should be well within MB's guidelines for current draw. Right? I'm asking because I'm planning on this as well.

3) This is a generic question. I'm trying to figure out how long it would take to charge your battery. If your charge rate is 50A, does that mean you can charge your 300AH to 50% in 3 hours?

Thanks!

Battery quality goes a long way. I used 2 Full River 6 volt 250s. Called full river and talked to tech support about charging off Alt. They said absolutely. The Sprinter Alt is a smart alt. Puts out what is needed and backs off to reduce load on engine when batteries are happy.

 

[Gski]

That's looking awesome.

Couple of questions on your electrical setup.

1) It doesn't sound like you're using a B2B for charging, correct? Isolation relay maybe?

2) You mentioned several times it's (almost) never a good idea to charge from the starter battery. I'm curious why you say this. As long as you keep the charging current to 40 or 50A, you should be well within MB's guidelines for current draw. Right? I'm asking because I'm planning on this as well.

3) This is a generic question. I'm trying to figure out how long it would take to charge your battery. If your charge rate is 50A, does that mean you can charge your 300AH to 50% in 3 hours?

Thanks!

No B2B at this time. The van came with an isolation relay and fuse block, which I just connected to.

The problem with just connecting direct is managing voltage and currents. The van uses an AGM for the engine battery, which has pretty specific charging needs, mostly trickle charging while the engine is running as it isn’t used for much other than starting the diesel. The house battery has different charging needs, mostly refilling after use.

If the house battery is pulling big current, the alternator will stay at high voltage which could cook the engine battery if it is full. A LiFePO4 battery likes to charge at about 13.5V. The engine battery needs 14.2V to charge fast, and floats (trickle charges) at 13.2V. The alternator can’t make both happy at once. This is the B2B’s job, to let each battery have its happy voltage, while also limiting current.

Question 3 is best answered by a book. I like Nigel Calder, but there are lots of good ones. Here is the short, short answer.

The maximum safe charge rate of LiFePO4 is 0.5C, where C is the capacity in Amp-Hours. The charging rate is linear to 95% full. The fastest charge for any battery size is 2 hours from empty or 1 hour from 50%. A lithium smart charger can be pretty stupid, as it just needs to disconnect when the battery is 90% full.

For AGM, the maximum safe charge rate is 0.2C and then less as the battery gets closer to full. It takes 5.5 hours to charge from 50%. This is why smart chargers are needed for all lead acid variants, to get the fastest safe charge. Taking an AGM below 50% charge doesn’t have a huge effect on lifetime, unless you don’t immediately charge back to 100%. Those amazing AGM test results for deep cycling beyond 50% are based on recharging immediately so the battery doesn’t sit at low charge. For a weekender, that means you need a battery rated at twice your needs.

Because the rates are relative to capacity, the fastest charge time is the same for any size battery. To get the fastest time, you do need to provide the charge current.

For a 100AH bank, the lithium takes 50A the whole charge period. An identically sized AGM takes 20A at first, tapering to near zero when the bank is at 90%.

Comparing equally rated battery banks misses the point, as the AGM bank is always bigger.

To get the same usable 50AH capacity as 100AH AGM, you need a 60AH LiFePO4. The max current is 20A for the AGM and 30A for the lithium.

Not clear yet? There are some good books and a lot of good threads on this forum. One of the reasons people get religion on batteries and charging is because it is not simple. Luckily, all we need is good enough.

 

[Gski]

One more bit of wiring. I use distribution blocks to connect and easily disconnect wiring. The one in the photo currently powers the fridge and the charging station and will have lights connected sometime in the future. It needs to be accessible to remove the fridge, plus the lighting will probably change a few times before the van is done.

All the wiring is hidden on the back of the access door. I am using leftover marine connectors, which heat shrink with hot melt glue to make the connection immune to salt water immersion. I didn’t bother applying heat as this is overkill in a van.

With the door closed for normal life.
Every bit of wood in this photo is temporary, with the possible exception of the access door. There will be a cabinet for dry food storage later this summer. The cabinet will still have a hidden chimney for the fridge to vent hot air, but the door may not be part of the final chimney.

 

[Gski]

With a little extra free time this month, I have started on the plumbing.
The plan is to have 20 us gallons of fresh water and 4 us gallons of hot water. The grey water tank is 15 us gallons. We will have a sink and a shower. Given that we exercise an average of two hours a day, a shower is essential along with lots of drinking water. This tank setup should give us about four days between fills.
A 20 us gallon tank weighs 200lbs when full. I wanted this to be as low and centered as possible to improve the handling of the van.

The fresh tank is at the back and the smaller grey tank is in front of it. The tanks are held in place by an aluminum frame which also supports the bed. The regular 10 series 8020 is strong enough, but I ran out and substituted some leftover 1030 (1”x3”) for the aft side braces. The side braces are not at the final height in this photo, they will be tweaked later to support the side walls for the storage space above the tanks. The tanks are held snugly by the straps. The alu cross braces just stabilize things for bumping around on dirt roads.

Looking back from the garage wall, before the tanks went in.
The tanks are raised above the floor to prevent freezing in winter mode. The grey tank sits higher to leave hose space underneath. There are 1/2” plywood bases to support the tanks evenly.
The 2” high aluminum block supports the grey tank, and also keeps the fresh tank from sliding forward.

If there is a crash, the small wooden block should rip open the fresh water tank, reducing the risk of it reaching the passenger space.
The straps go under these bars.

People wonder if it safe to drink from plastic tanks. It probably is, which is why these tanks can be marketed for drinking water use. If this is not safe, I am probably already damaged by decades of drinking from similar tanks.

Some of the plumbing connections will be assembled from here. The space above the tanks will be filled with plastic storage boxes. Just because it is easier and cheaper than drawers.

 

[Gski]

Okay, the tanks are plumbed to the point that we have cold running water, which is pretty useful these days.

The red pipe is the fresh water tank fill, with a garden hose fitting. The storage tray and walls are designed to store plastic boxes, which makes them simpler, but also makes it easier to disassemble when repairs are needed. Not the most attractive garage storage perhaps, but very practical.

The side panels for the forward lower storage aren’t in yet, but that gives a better view of the plumbing and wiring. The exposed floor on the right will eventually have a sliding tray for the kayaks.

I wanted to be able see all the plumbing connections. Because the space will only hold boxes, the ‘wall’ that protects the plumbing can be a wooden spacer. The side walls for this area will have cutouts to inspect the plumbing.

Test fitting storage boxes.

The sink went in earlier, but I forgot to post that part of the build. The netting ‘cabinet face’ will get replaced eventually, but it actually works fairly well.

This has been a lot of work so far, and there is a lot left to do. Each week is a step closer. With campsites opening in two weeks, the pressure is on....

 

[Gski]

The fresh water pump is tucked on the front of the wheel arch. Access for repair does require sliding yourself in on the bike tray, but hopefully that isn’t needed often.

(The forum is flipping images when I insert them today. Just do a headstand in front of your computer ?)
The blue hose that dead ends by the wall will go to the water heater when it arrives. The red hose running up to the base of the bed is the pressure tank to keep the pump from cycling too often. Most people use a much larger tank, but 30” of 1/2” pipe appears to be a big enough air bubble.
Everything, including wiring, has quick disconnects for easier repair/replacement in the future.

The jabsco 1.9 gallon per minute pump works well, but is very noisy the way I mounted it. The flow rate at the sink is 7 seconds per litre, or about 1.8 gpm. This is a much higher flow rate than my garden hose at home. Very convenient for emptying the fresh water tank, but not helpful for conserving water while travelling.

 

[Gski]

The door table is finally in. This idea is very popular, I first saw it from Traipsing About but have used other people’s ideas too.

I used non-mortise door hinges to keep the table closer to the cabinet when closed.
The big trick here is the string that holds the table in position. It is Marlow Excel Pro Racing line in the 3mm size. This spectra rope is low stretch, similar to steel wire, with about 400lb breaking strength. If you sat on the table, the 1/2” baltic birch plywood would flex more than the rope stretches.

A simple loop of string keeps the table in place when closed.

Spectra rope is magic: you can use it like rattle-free wire in most places. Here it is used as a cabinet ‘door’ for the box storage spaces. The plastic knob hides a hex bolt that tightens to lock the end in place.
This is not a pretty solution, but my wood working skills are just not up to making doors that fit.

 

[RVBarry]

When that fails (500lbs per side), the four sewn slings (red) will gently catch the now twisted frame while stretching about 4”.

Hi, very clever...
What are you using to make the slings?
Thanks!

 

[Gski]

Hi, very clever...
What are you using to make the slings?
Thanks!

I just buy nylon sewn slings from the climbing store as they come with rated strength and stretch ranges.

I use red for nylon slings only: any other colour is a low stretch sling (spectra, dyneema, etc). This makes it easier to grab the right sling for the job.

Any climber (or ex-climber like me) will have a handful of sewn slings around.

This one (the forum is randomly rotating images for me right now, the sling hangs downwards in real life) is a handy grab point for climbing into bed.