HELLO NERDS! Complex Battery and Solar Panel Question?


Original Post
Gaar · · Springdale / Zion UT / Moab · Joined Feb 2007 · Points: 765

Hey Everybody,

So I'm rebuilding my truck The Tortoise for another season, and I'm thinking of running solar this year. I've done a lot of research but can't seem to find any info on my specific needs. I've been living in the rig mostly for 7 months now and have many more to go. 

Here goes, I'm running  2 NEW parallel group 27 (non-marine) starting batteries for the diesel. Off of these I run, a 1000w LED Bar hardwired with inline fuse. 250w head unit 4 kicker 6x9 speakers, with 1100w mono channel amp to a 12' 300w kicker subwoofer (wired correctly to head remote terminal and then 8ga Battery to amp & 8ga amp to chassis .) Next have a 450w inverter in the bed with 10ga solid copper leads direct to battery (with inline fuse). I use the inverter and usb ports to run LED lights,  computer, charge things and an electric blanket in the winter months.  I'm considering putting an electric cooler or small fridge, for the rest of summer depending on draw and amps.

I installed everything myself, correctly & professional with good materials. Want it to last 

Normally I usually only go about 3-5 days without starting the truck. Most because I'm not sure about What i've got left or need to start the truck. Would be nice to go a solid week or two? My usage varies. In the winter (sub freezing) I ran the electric blanket, stereo and lights almost 2-3 hours every night and sometimes it struggled to start (on old batteries). During summer I thump the main stereo  most days and run lights a lot, with the truck off.

Everything I can find refers to RV/Camper Battery banks with deep cycle or Marine. Nothing I can find talks about normal Group 27 starting batteries, stilled wired to the truck.

Should I?, Can I? or I Shouldn't 

A) Wire in a 100w panel with controller directly into my copper leads from the inverter (mainly because the wire can handle it and its already run through the frame of the truck?

B) Wire in a 100w panel with controller on separate lines direct to batteries?

C) Wire in an Isolator and run everything from one battery when parked and rely on only one starting battery. (remember diesels require deferent starting amps!) 

D) Do nothing but by a volt meter, or monitor and just watch and start the truck when needed

E) Say fuck it and leave it, It'll be fine!

Will this fuck with my truck because it wired in and will be left that way?

With this fuck my starting batteries because they're not Deep?

Will this fuck my charging rates and life span of batteries?

I really don't have room to drop another smaller 6v battery and dedicate it to the bed, plus I want to always be able start my truck. Thats why I'm trying to go to the starting batteries and not a separate rv battery bank.

Thanks any input would be great

Gaar

Alex Rogers · · Sydney, Australia · Joined Sep 2010 · Points: 40

Gaar, I have a solar setup for my camping trailer - mostly to power a 12v fridge (60 litre) as well as a few LED lights, charger etc. The battery (120 amp hour deep cycle) is charged when I'm motoring from the car (diesel Pajero) via an isolator & heavy gauge wire. But I'm often bush for 5-7 days, and when sunny for a few hours a day, my 160W panels keep the battery charged indefinitely. I bought 12v panels, and cut off the cheap and nasty solar charger, and wired in a decent STECA MPPT charger, which makes a real difference. The battery, solar charger, control panel (12v outlets, ammeter, USB outlets etc), 240 mains charger etc all fit in a wooden crate, and I have 10m of cable to the solar panels, so I can move them around to follow the sun, and park in the shade. It works very well. 

My thoughts - don't wire the panels directly, they need to go to a solar charger, which then connects to your battery. Get a decent MPPT charger. No need to hard wire it - I use Anderson plugs for all the connections, and just leave a short harness (cable to the battery terminals, Anderson plug on the other end) permanently on the battery. If you want the battery permanently in the truck, and you have space for 2 batteries, that is fine - just ditch one of the starter batteries, and install the biggest deep cycle battery you can fit in the space. Starter batteries are useless for this, you will kill them quickly, as they are not designed for deep discharge, rather bursts of hi-amp output. Deep cycle can be discharged to at least 50% regularly with no harm. They can also be used to assist your starter battery if that is low - but make sure you isolate it so that even if you run the deep cycle flat, you don't flatten the starter battery. Get more panel than 100W, my 160W is fine in sunny Australia, but you have a big proposed load there, you might need more battery and panel than you are proposing. There are some good online calculators that will help you work out your requirements given your loads, weather, time off grid etc. 

Cheers

20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,352

A few notes:

- Do not deep cycle your starting batteries. Standard auto batteries are only designed for starting the vehicle and that's it. They have thin plates in them and the plates will quickly deteriorate if you deep cycle them. They are intended to remain at 85% state of charge or higher for their entire life. You can run your OEM stereo for a tad with the car off, but running tons of electronics for hours without the truck running is not a good idea.

- It's fairly universally accepted that using your main starting battery to run electronics with the vehicle off for long periods is very bad practice. In addition to the issue posted above, if you run the battery down too much you're not going to be able to start your truck which could become a serious issue if you're somewhere remote.

My suggestion would be to skip the solar and get a deep cycle battery to run the electronics off. Charge it with the alternator using a smart battery relay or isolator which disconnects the battery from the OEM system when the vehicle is off. That's the cheapest option and it will work fine as long as you start the vehicle on occasion for at least 15 minutes at a time, such as to dive to the crag, ect. Solar works, but you wont be able to charge the batteries if it's cloudy for a long period or you use more electricity than you expected. Further, mounting a solar panel on your roof will reduce your interstate fuel economy enough that it will cost less in fuel charging the battery with the alternator during standard tips than using the solar panel. If you cant find room under the hood for the extra battery, try mounting it under the vehicle (in a way that the terminals can NEVER short on the chassis of your vehicle). Do not mount lead acid batteries anywhere inside the vehicle as they produce hydrogen which is explosive.

Last resort, you could try getting one really good, high-CCA battery to start the truck and use a standard deep cycle in the other slot with a relay isolator if you absolutely dont want to mount under the truck. It may be possible that you can mount a larger battery in the OEM spot with a bit of modifications. If you do go on one starting battery, use a relay instead of an isolator as isolators produce about a 0.9v drop to the batteries (due to the diodes inside the isolator). Relays do not produce much, if any, voltage drop.

Gaar · · Springdale / Zion UT / Moab · Joined Feb 2007 · Points: 765

Hey guys, thanks for getting back to me. I'm always somewhere remote...Thats why I looking for advice.

Alex- I've had full intent to put a charger/controller in-between the solar and battery if I go that route. 

I have no room anywhere bed or engine bay for additional batteries. I'm already running 2 group 27 which are the same size as full deep cycle, just with thinner plates. Both run 810cca  each. One is enough to fire the truck on a warm day. It may struggle  with only one around sub freezing temps. Remember its a 5.9l inline 6cyl turbo cummins. Big engine.

20kn- You're suggesting I modify my option C from the OG?

                Because my batteries are wired parallel for starting purpose, can I mix and match types? Say I keep one of the group 27 for starting, the closesr to the starter, and go to a group 27marine or 31 for my accessories. With an Isolator or Reley In-between. If I'm constenly draining one to 50%ish and charging with my alternator will this expedite the death of my alternator? Will it affect a diesel starting with 2 batteries with 2 different cca and different amounts of power in the bank?

Thanks again.

20 kN · · Unknown Hometown · Joined Feb 2009 · Points: 1,352
Gaar wrote:

Hey guys, thanks for getting back to me. I'm always somewhere remote...Thats why I looking for advice.

Alex- I've had full intent to put a charger/controller in-between the solar and battery if I go that route. 

I have no room anywhere bed or engine bay for additional batteries. I'm already running 2 group 27 which are the same size as full deep cycle, just with thinner plates. Both run 810cca  each. One is enough to fire the truck on a warm day. It may struggle  with only one around sub freezing temps. Remember its a 5.9l inline 6cyl turbo cummins. Big engine.

20kn- You're suggesting I modify my option C from the OG?

                Because my batteries are wired parallel for starting purpose, can I mix and match types? Say I keep one of the group 27 for starting, the closesr to the starter, and go to a group 27marine or 31 for my accessories. With an Isolator or Reley In-between. If I'm constenly draining one to 50%ish and charging with my alternator will this expedite the death of my alternator? Will it affect a diesel starting with 2 batteries with 2 different cca and different amounts of power in the bank?

Thanks again.

I'm suggesting you mount another battery under the truck so you dont mess with the starting batteries at all. If you use a smart relay, the batteries will not be in parellel for starting. The relay will not close until around 13.2v (specific to the brand), which means the engine needs to be running before it closes. You can mix the two batteries while the vehicile is running as long as they are seperated when the vehicle is not running. Mixing batteries with no active charge will cause paracitic discharge and they will depleate each other. But the relay solves that problem. Using the alternator to charge a battery is a bit hard on it. However, your diesel truck should have a fairly large alternator that should be able to put up with it. As long as you're not running the battery all the way down to dead flat all the time, you should be okay. The battery might use 100A or so to charge when you first start the truck, but that should taper off to below 50A within a 120s or so.

You can use a standard relay that is connected to the ignition so the two batteries are in parallel while starting the vehicle. However, depending on how far you discharge the battery, that might make things worse than running just one to start. If the voltage drop caused by the starter on the starting battery does not fall below the resting voltage of the second deep cycle battery running the deep cycle battery in parallel will cause a drain on the system. In other words, if batt 1 is 12.8v, batt 2 is 12.0 v, and cranking over the engine causes the voltage to drop to 12.1v on batt 1, then running batt 2 in parallel is going to draw current from batt 1, not supply it. If on the other hand, batt 2 was only discharged to 12.4v, then in that scenario it would supply current and help start the engine. So as you see it depends on how far you discharge the batteries as to whether it would be good to have the deep cycle battery connected to the starter or not along with the starting battery.

A battery with 875CCA means it can supply 875A for 30 seconds at 0 degrees F before dropping to 7.2v (which means you have about 20s to stay above 10v). That should be enough current to turn over just about any engine in any vehicle that does not require a commercial drivers license. However, once the battery gets old it's hard to say.

Guideline #1: Don't be a jerk.

Post a Reply

Log In to Reply