Requesting comments on planned solar/alternator/shore power system

[will5023]

Hi, everyone,

First post; been lurking for a few weeks. I recently bought a 1985 VW Westfalia automatic with 212,000 miles on the chassis and about 50,000 miles on a Subaru EJ25D engine. I’m excited about doing some mods and upgrades and the first thing I want to do is install a solar system and auxiliary battery. I’ve been reading all the helpful threads about solar, ACRs, Inverter/Chargers, etc. Thanks to all!

I think I’ve figured out my electrical system but I wanted to run it by you guys before I buy anything. I want to have an auxiliary battery that can be charged by solar, shore power, or alternator power. I’ll be camping on weekends mostly without shore power, I will not be using the camper as my daily driver, and when it is stored it will be in full sun. Note that I cannot provide shore power when it is stored.

Using a web based usage estimator, I calculated my usage at roughly 150Ah per day with the biggest draws being a Propex HS2000 furnace and an Engel MT80 fridge/freezer along with lights, fans, electronics charging, etc. I’ve read however that these estimators can be off significantly.

I’m still trying to figure out which batteries I want to use. I’m set on AGM and I’d like to have about 300 Ah. I want to put the battery or batteries under the bench seat in the rear of the camper so space is limited. I was thinking about a VMAX 350 Ah but then I read a bad review. Now I’m thinking about 2 Universal UB121000 batteries wired in parallel which would only give me 200 Ah but are more well regarded. I’m looking for suggestions on the batteries.

I’m tying Engine Battery (Eng+/-) and House Battery (Hse+/-) together with a Blue Sea ACR 7610. I read instructions somewhere on attaching the ACR to the starter instead of the Engine Battery to reduce cable length so I will try this although I don’t know how this will apply to the Subaru’s electrical system. I’m fuzzy on where Subaru ends and VW begins in regards to the electrical.

I’m planning on using a Xantrex Freedom XC Inverter Charger with Control Panel not only to supply 120v when on battery power but also to charge batteries when on shore power. I’m also planning on using a Victron 100/20 managing 2 @ 175W Newpowa solar panels connected to House Battery.

I can't get my crappy ascii drawing to display properly so I'm attaching it to this message.

Please let me know if I’m missing anything or anything seems amiss.
Thanks!
Will

 

[luthj]

You are really pushing the limits with 300AH or more of lead in a westy. They are already near GVWR with 4 passengers and some light gear. Plus the brakes, low power, and limitations of the 3 speed auto....

Personally the most I would go is about 225AH. Your best bet is 2x GC2 (6v). Mount them under the bench seat. Good units will cost about 220$ for the pair, and they will far outlast any AGM battery in this application, for the fraction of the price. The nonsense about explosions and hydrogen is bunk. I have done the math, and to get anywhere near a dangerous level is not possible in a van with just 200AH of batteries.

What voltage is your alternator? Measure it after a drive so its hot. That will tell us if your alternator will be an effective charge source.

The solar panels will add weight and drag. I agree they may be necessary, but consider other options first.

My suggestion. Get a 100AH or maybe 2x drop in lithium batteries. Trojan released is trillium line, and battleborne has some good reviews over the last year. Both will run around 1000$ for 100AH. You may find that single 100AH lithium battery will meet your needs well.

These will weight about a quarter of the lead, at half the size. Connect them to your alternator (assuming its at least 13.8V), and you can get whatever rates that alternator can support, up to 50A per 100AH. This allows for rapid recharging in just an hours drive. Combined with a modest 100-200W solar array, and you can meet your needs much easier.

There are temperature charging concerns with the lithium. They need to be above a certain tempt to charge at a decent rate. A bit of insulation and a heating pad (50-100W) can easily take care of this in conjunction with a thermostat.

 

[luthj]

Its definitely possible to get a hydrogen explosion in a very small sealed space (think non vented sealed battery box). I just hear the alarmist mantra that "inside must be AGM$$$!" constantly. The reality is much different. It is actually quite hard to contain hydrogen in a vehicle to the required concentration.

Batteries can experience thermal runaway, regardless of AGM/flooded. That can be caused by damage, improper charging, or really high (think 130F+) temps.


I am not saying to ignore this issue, just that a small mount of design consideration can negate the hydrogen issue completely.

 

[dwh]

Using a web based usage estimator, I calculated my usage at roughly 150Ah per day with the biggest draws being a Propex HS2000 furnace and an Engel MT80 fridge/freezer along with lights, fans, electronics charging, etc. I’ve read however that these estimators can be off significantly.

Duty cycle is key. If it's hot the fridge will spend more time running, and the fans, but the Propex won't be used. Vice-versa when it's cold.

I’m tying Engine Battery (Eng+/-) and House Battery (Hse+/-) together with a Blue Sea ACR 7610. I read instructions somewhere on attaching the ACR to the starter instead of the Engine Battery to reduce cable length so I will try this although I don’t know how this will apply to the Subaru’s electrical system. I’m fuzzy on where Subaru ends and VW begins in regards to the electrical.

Where is the engine battery? A couple feet one way or the other won't much matter.

As to connecting to the starter instead of the battery...what size wire runs from the alternator to the battery (that's probably your bottleneck), and what size from the battery to the starter? If I was messing around with aux battery wiring in the engine compartment anyway...I'd probably just run straight out of the alternator to the ACR and leave the existing ALT->BAT->STARTER wiring as is.

I’m also planning on using a Victron 100/20 managing 2 @ 175W Newpowa solar panels connected to House Battery.

100|20 is marginally too small for 350w. I use a 100|30 for my 300w. Also note the Victron "Smartsolar" line has built-in bluetooth, whereas the "Bluesolar" line requires an added dongle for bluetooth.

 

[will5023]

Hi, everyone,

Thanks for the replies. Since I last posted, I've changed a few things. I've decided to go with a Victron Cyrix-ct 12/24v-120 instead of an ACR to join the house and engine battery. I've also decided to use a Victron Multiplus Inverter/Charger 12/2000/80 instead of the Xantrex.

I have to plan wire guage, monitoring, and where to provide overcurrent protection. That will be next once I have my gear selections solidified.

Can I mount 27" x 52" panels directly to the Thule roof racks or do I need a more solid support structure like strut channel? Are the panels in danger of flexing? My rack bars are 37" apart.

You are really pushing the limits with 300AH or more of lead in a westy. They are already near GVWR with 4 passengers and some light gear. Plus the brakes, low power, and limitations of the 3 speed auto....

My thinking was that it wouldn't be that much more weight than a passenger. My trips will be split pretty evenly between only me or me and someone else. I am, however, thinking of going to two 100Ah batteries instead of one huge battery. I am still looking at the Vmax after doing more research.

What voltage is your alternator?

14.25v at idle
14.33 when I gave it some gas

Where is the engine battery? A couple feet one way or the other won't much matter.

The engine battery is located under the passenger seat. It would mean a savings of eight feet probably.

100|20 is marginally too small for 350w. I use a 100|30 for my 300w.

Just wondering why you went with the 100|30. I used the Victron sizing calculator and was told to use the 100|20. In order for the calculator to determine the 100|30 is necessary, I had to up the wattage to 185w per panel. I'm not trying to debate you, just trying to learn.

Thanks again!

Here's the specs for my panels:

Here's what the Victron displays:

 

[rayra]

150Ah / day. That's what, 6 batteries to hit your 50% consumption / 300Ah total capacity mark". Do you have the room and the weight margin for that? You might want to plan to max out your solar panel coverage / array and re-figure your consumption and what you'll be using when. And buy a couple good sleeping bags.
IMAO it seems you are trying to cram in the full comfort of home into a vehicle camping rig that's scarcely adequate for such a comfort level.

 

[dwh]

My panel is rated 305w @ STC. It has a Vmp of 36v.

Mine:
305w ÷ 36v = 8.47a
305w ÷ 12v = 25.4a

Yours:
340w ÷ 19v = 17.89a
340w ÷ 12v = 28.33a


Granted a flat-mount running hot won't be at max efficiency...but still.

 

[dwh]

Sorry, forgot to notate that the first number is solar side, the second is battery side.

(Assuming a battery at 12v. Replace 12v with whatever the actual battery voltage is at any given moment and recalc.)

 

[dwh]

Also assuming yours in parallel. If series double the voltage in the first number and recalc.

 

[dwh]

Why are the series/parallel numbers different in the sshots of the Victron calc? You'll have two panels either way no?

I dunno why it's telling you to use a 100|20 w/340w of panels...but it's wrong.

 

[will5023]

150Ah / day. That's what, 6 batteries to hit your 50% consumption / 300Ah total capacity mark". Do you have the room and the weight margin for that? You might want to plan to max out your solar panel coverage / array and re-figure your consumption and what you'll be using when. And buy a couple good sleeping bags.
IMAO it seems you are trying to cram in the full comfort of home into a vehicle camping rig that's scarcely adequate for such a comfort level.

Yeah I think I over estimated when I was looking at the online calculator. Its too easy for me to say, "Well, I might want to listen to the radio for an hour every day; might as well include it," and then repeat for microwave, hair dryer, etc, etc. Looking at it again, only running the furnace, laptop, and coffee maker, I get 55-60Ah/day.

My panel is rated 305w @ STC. It has a Vmp of 36v.

Mine:
305w ÷ 36v = 8.47a
305w ÷ 12v = 25.4a

Yours:
340w ÷ 19v = 17.89a
340w ÷ 12v = 28.33a

Granted a flat-mount running hot won't be at max efficiency...but still.

This makes sense.

Why are the series/parallel numbers different in the sshots of the Victron calc? You'll have two panels either way no?

I dunno why it's telling you to use a 100|20 w/340w of panels...but it's wrong.

The second victron shot is just illustrating the point that, in order for the victron calc to return a recommendation of a 100|30, you have to input a wattage of 185w per panel. Sorry I wasn't clearer.

I've ordered to the 100|30 based on your recommendation. Thanks again for the replies.