Solar panels to starter batteries

[Kwest364]

How to keep starter batteries topped off from existing solar panels and battery systems?

My bus: 1986 Bluebird/Chevy/GMC B6000/B60

My systems:

1x 12V DC appliance running system. This is wired completely separate from my AC/house batteries set up. Powers water pump, water heater, heater. Consists of 1x100W panel + 1x100ah gel deep cycle battery.

1 x 24V AC appliance running system. These run all the normal interior AC loads from inverter into outlets. Consists of 6x185W panels + 4x100ah lead acid deep cycle

Starter batteries: 2x big starter batteries (in parallel)

Bus use: full time living. Up in sunny SoCal mtns. Bus gets moved every 3-5 days. Moved to other spots nearby. Drive time is 10-20min tops.

Problem: not long enough driving time to charge batteries back up to 100%. So, how can I use current solar system or make separate system to charge and keep starter batteries topped off?

Buy separate panel (maybe those tiny rv solar panels for just this reason), separate charge controller and wire to starter batteries?

How to use current system to do it?

How long at idle to charge batteries back to 100%? 15 min? 1 hour? It depends, yes, but give me an idea.

Regardless, solar topping off = best option

[rossvtaylor]

Normally, the challenge is the reverse of that...using the starter battery and alternator system to charge the house batteries while driving. For that, you'd use a DC>DC charger which would provide 3-stage charging to the house batteries. I've had good experiences with these: https://www.solar-electric.com/victr...c-charger.html

To do what you want, you'd use the same (or a similar) charger connected so that it charges the starter battery from your house battery and PV system. Just turn off the Victron's "engine run" sense function.

[Rucker]

Hadn't thought of using a DCDC charger in reverse.

My Renogy mppt charge controller has a separate set of 'load' terminals that can be configured to generate power only when the solar is producing good power. If I needed to top off starter batteries I'd probably use that side of the charge controller.

Your solar charge controller may or may not have a similar feature.

[rossvtaylor]

Originally Posted by Rucker

My Renogy mppt charge controller has a separate set of 'load' terminals that can be configured to generate power only when the solar is producing good power.

That should work..the only downside being that it won't offer any staged charging (bulk, float, absorb, EQ and all that...). But that may not be important.

One thing I didn't ask the OP, which your post made me think of, Mr. Rucker.

Are your house batteries lithium or lead-acid? From your post, it looks like a gel...which is a lead-acid. IF that's the case, you might be able to just use a solenoid to connect the two systems. You can't do this with lithium and lead-acid, but with two lead-acid banks you could. The one risk is that gel batteries are easily damaged if overcharged (they're more sensitive than FLA or AGM)...so you need to ensure that you don't leave that connection solenoid "on" while you're driving.

[flattracker]

I addressed the issue in the "new Crown". I have five 200 watt panels mounted to the roof of the bus. All of the panels are wired to a terminal block inside of the bus. I constructed the terminal block so that two of the panels are connected to one terminal, while the other three are connected in parallel. Three panels feed power to the main charge controller and the other two are connected through a SPDT switch to either a second charge controller or in parallel with the other three. In one configuration all five panels supply current to the main charge controller that charges the house batteries and in the other configuration two panels provide current to the second charge controller that charges the bus batteries.
The number of panels that can be switched between charge controllers is up to the builder. I chose two. This way I can leave the bus unused for a period of time and keep all batteries charged. When I am actively using the bus I would switch the two panels to be in parallel with the other three, as when I am driving around with the bus, the bus batteries would be maintained from the alternator. Also, when I am driving the bus, a second alternator also charges the house batteries. When I am stopped for the day (or night) having all solar power sent to the house batteries is best as I would use them to run lighting, heating, pumps, etc.
The bus starting batteries are isolated from the house batteries at all times (unless emergency need arises).

The lesson I have learned about solar power systems is use charge controller that can handle a higher voltage than the panels can produce by a good margin. Current ratings are also important.
My panels are specified to produce up to 26 volts DC open circuit, but I have measured 29 volts DC. This was enough to fry three charge controllers. The best I can tell now is my latest controllers handle the panels well.
Also use a switch that handles the current available from the panels.
Connect the charge controller so that is is always connected to the batteries and the switch disconnect the panels from one controller and connects them to the other controller.
I hope this helps.

[bubb, the real one]

What I have done, I ran a wire from my bus bar to alligator clips in the start batteries, I put a switch in the wires so I decide when to charge, I used 8ga so I can use the house battery’s help in winter starting,

[Rucker]

Originally Posted by flattracker

I addressed the issue in the "new Crown". I have five 200 watt panels mounted to the roof of the bus. All of the panels are wired to a terminal block inside of the bus. I constructed the terminal block so that two of the panels are connected to one terminal, while the other three are connected in parallel. Three panels feed power to the main charge controller and the other two are connected through a SPDT switch to either a second charge controller or in parallel with the other three. In one configuration all five panels supply current to the main charge controller that charges the house batteries and in the other configuration two panels provide current to the second charge controller that charges the bus batteries.
The number of panels that can be switched between charge controllers is up to the builder. I chose two. This way I can leave the bus unused for a period of time and keep all batteries charged. When I am actively using the bus I would switch the two panels to be in parallel with the other three, as when I am driving around with the bus, the bus batteries would be maintained from the alternator. Also, when I am driving the bus, a second alternator also charges the house batteries. When I am stopped for the day (or night) having all solar power sent to the house batteries is best as I would use them to run lighting, heating, pumps, etc.
The bus starting batteries are isolated from the house batteries at all times (unless emergency need arises).

The lesson I have learned about solar power systems is use charge controller that can handle a higher voltage than the panels can produce by a good margin. Current ratings are also important.
My panels are specified to produce up to 26 volts DC open circuit, but I have measured 29 volts DC. This was enough to fry three charge controllers. The best I can tell now is my latest controllers handle the panels well.
Also use a switch that handles the current available from the panels.
Connect the charge controller so that is is always connected to the batteries and the switch disconnect the panels from one controller and connects them to the other controller.
I hope this helps.

Your system is another good way to electromechanically control what is being charged. The only downside is manual control versus electronic control with a DCDC controller).

It occurs to me there's another dirt simple way: get a cheap battery tender and plug it into the House 120 circuit. Yeah, there's some conversion loss, but I'd imagine it to be negligible.

[Rucker]

Originally Posted by bubb, the real one

What I have done, I ran a wire from my bus bar to alligator clips in the start batteries, I put a switch in the wires so I decide when to charge, I used 8ga so I can use the house battery’s help in winter starting,

Good point. As long as all the batteries are lead acid, that would work as well.

Not an option for those of us with LiFePo house batteries.

To ensure cranking amps I have two extra lead-acid chassis batteries on an isolator behind the two chassis batteries that normally come with the bus. Press a button, and there's four batteries in parallel for the starter.

I run the bus for about ten minutes every week when not using it. That seems to keep all the chassis batteries topped up.

[Dbacks2k4]

I just use a standard battery maintainer mounted in my battery box with a 110 plug on it. Once my bus' "house" system is installed I'll drop an outlet down there that's on a switch up in the cabin. Not the most efficient, but that does allow me to unplug that maintainer and plug-in to a drop cord to shore power whenever I need without monkeying with extra DC-DC converters. That plug down there would also give me access to use a full blown battery charger or jumperbox off the house power as well.

I suppose you could argue if I was using a shore power drop cord I may as well plug in the house system and charge that way, but KISS (keep it simple & stupid).

That and the maintainer is already installed so I can keep the starter batteries healthy during the build. I'm nowhere near ready for "house" power yet

[Booyah45828]

Honestly, I'm not reading where anything on the "house" side of the power equation is consuming power from your starter batteries. If your starter and 2 house systems are unconnected, there should be no reason your starter batteries would be dead after a few days, unless you're leaving keys or some other device turned on. If you're not leaving something turned on, you need to find what in the system is draining the starter batteries, as they should stay charged for weeks at a time in the scenario that you describe. Run a parasitic draw test, and if there is minimal, load test your batteries for correct capacity, and then load test the alternator for correct capacity, because something here isn't adding up.

Yes, if you have excess solar you can use it to maintain your starting batteries. But if you're running it for 15-20 minutes every 3-5 days, there's no reason the starter batteries should be dead, so solar charging would only be masking a problem.

As far as making the excess solar charging the starting batteries idea to work, you have measure and see if either system has a decent amount of excess solar power. If they don't, then you'll have to install additional panel(s).

If the 12vdc system does, use a relay controlled by the panel to latch the starter and 12vdc system together when the panel has enough wattage to do so.

If the 24vdc system has excess solar, use a simple battery maintainer plugged into the 120vac side. You're going to have conversion losses this way, but you'll likely have conversion losses with a dc-dc converter too, and those 120vac battery maintainers are cheap and available nearly everywhere.

[Rucker]

Great point about ensuring there's no battery drain problem Booyah

[Dbacks2k4]

Originally Posted by Rucker

Great point about ensuring there's no battery drain problem Booyah

A lot of newer buses have a ton of parasitic draw for electronic (or electronically actuated air) doors, locks, those Zonar monitoring systems, etc.

OP stated an 86 GMC/Bluebird. I had an 84 GMC/Bluebird for a while so there shouldn't be anything that pulls on that by design, they're about as simple as simple gets. Definitely could be something installed after the fact, my 84 GMC had an after-market tow hitch and wiring harness in there with a brake controller that was disconnected when I got it, probably for that reason

It could also be the battery age is getting up there and it's not charging to a very high state to begin with? If the batt is old might be worth checking out.

[Booyah45828]

Correct, new buses have a plethora of control modules and draw compared to old stuff, but after half an hour or so, they should fall in line with only a couple hundred milliamps or so. The only things I've seen that were supposed to continue to draw after half an hour are some aftermarket security systems.

Regardless, his 86 should have none of that, save a radio if equipped. It definitely shouldn't be dead after a few days. Possibly a bad alternator, bad voltage regulator, or a dead cell in one of the batteries, which would consume the power in the other battery. Or maybe the batteries are 10 years old and just worn out? They don't last forever.

And I'm not say he shouldn't figure out a way to solar charge his starting batteries. Having the batteries on a maintainer isn't a bad idea. My riding mower battery has been flawless for 3 years now, whereas I used to replace it yearly. So they do have value. But his scenario isn't normal and shows that there is likely something wrong, and that a maintainer might only mask the issue, or it might not even be mask it at all.

[flattracker]

One prime consideration as to why I set up the solar power the way I did on my Crown was the fact that it is kept in a storage yard with no external power available. If I was connected to shore power I could easily use a battery maintainer to keep the starting batteries fully charged and use the RV charger installed in the bus to assure full charge on the house batteries.


Today was good sun and the house batteries were at 14 volts and the bus batteries were at 13 volts.

[Iceni John]

I use a pair of LSL Products' Ultra Trik-L-Start battery maintainers to keep my two Group 31 start batteries always fully charged from the house batteries that are in turn always fully charged by my solar system. I tried running a pair of small cheapo charge controllers for my start batteries directly from my PV array, but they were overloaded and constantly shut themselves off; the Ultra Trik-L-Start maintainers are just DC-DC battery chargers. So far, so good.

John

[Veloc]

Going to suggest going with the dedicated solar charger as well. House and vehicle battery systems IMO should be 100 percent isolated from each other. You don't want a problem with one system being able to kill the other. At most you should have a way to use the house batteries to jump the vehicle battery, but even that should be a manual connection (jumper cables) for emergency use only. It only takes a small solar panel the size of the battery top to keep a battery maintained, so putting a small 100W panel on the roof next to the main panels shouldn't be a problem.

[Rock-N-Ruth]

Originally Posted by Kwest364

How to keep starter batteries topped off from existing solar panels and battery systems?

My bus: 1986 Bluebird/Chevy/GMC B6000/B60

My systems:

1x 12V DC appliance running system. This is wired completely separate from my AC/house batteries set up. Powers water pump, water heater, heater. Consists of 1x100W panel + 1x100ah gel deep cycle battery.

1 x 24V AC appliance running system. These run all the normal interior AC loads from inverter into outlets. Consists of 6x185W panels + 4x100ah lead acid deep cycle

Starter batteries: 2x big starter batteries (in parallel)

Bus use: full time living. Up in sunny SoCal mtns. Bus gets moved every 3-5 days. Moved to other spots nearby. Drive time is 10-20min tops.

Problem: not long enough driving time to charge batteries back up to 100%. So, how can I use current solar system or make separate system to charge and keep starter batteries topped off?

Buy separate panel (maybe those tiny rv solar panels for just this reason), separate charge controller and wire to starter batteries?

How to use current system to do it?

How long at idle to charge batteries back to 100%? 15 min? 1 hour? It depends, yes, but give me an idea.

Regardless, solar topping off = best option

Our alternator failed on our daily driver, full time live in bus in 2019. We are self contained with 3900W of solar and a 6K LF inverter. We just put a 20A marine charger in our battery box. We ran without an alternator for more than a year and 13000 miles before we got it fixed.

[Shorty22]

Very informative video on a system with 3 options of battery charging done in a mostly 12V cheap and efficient design.


1- rooftop solar connected to MPPT charger to keep batteries healthy and topped off properly


2- alternator charging to charge/top off house batteries from starter batteries


3- simple extension cord inlet to top off/charge house batteries with a DC- DC charger



"A Bus Life Story" on YouTube- "Skoolie Conversion Electrical System"

https://youtu.be/PUPIFlAGqhA


I'm personally following this plan on my short skoolie in the Pacific Northwest. Still looking for help with getting this video design into a line drawing.

[rossvtaylor]

Originally Posted by Shorty22

Very informative video on a system with 3 options of battery charging done in a mostly 12V cheap and efficient design.


1- rooftop solar connected to MPPT charger to keep batteries healthy and topped off properly


2- alternator charging to charge/top off house batteries from starter batteries


3- simple extension cord inlet to top off/charge house batteries with a DC- DC charger



"A Bus Life Story" on YouTube- "Skoolie Conversion Electrical System"

https://youtu.be/PUPIFlAGqhA


I'm personally following this plan on my short skoolie in the Pacific Northwest. Still looking for help with getting this video design into a line drawing.

Please, don't follow that plan. I just started watching and gave up at the 5 minute mark when he bragged about using 8 gauge wire out of the charge controller. He said the incoming wires from the solar array are 10 gauge so he could use 10 gauge on the output, but he wanted to be safe (and didn't have enough #10) so he used 8 AWG. He clearly doesn't realize that the voltage on the input is anywhere from 35-120 volts but it's 12V on the output. #10 would not have worked, so I'm glad he didn't have any more. #8 would be fine, with a 3% voltage drop, for a 6-foot run...but he'd need larger cable for anything longer.

I started to doubt him when I saw that he laid the flooring first and screwed things down to it. He, or the buyer, is going to be mighty sad when that buckles or gaps...

Okay, I had to watch more.

When he describes using #4 wire to run back from the DC>DC charger, I'm guessing that's about 20 feet and he'd need a #2 for that with a 3% loss.

And...I watched the rest...

Perhaps I was a bit harsh at first, but seeing folks demonstrate wiring when they don't show a clear understanding of the design considerations bugs me.

I do like (and am a promoter of) the simple "charger as shore power" design. And he makes good points, with which I agree, about using 12VDC as much as possible and turning off the inverter when not needed.

But he does or says lots of things I disagree with. First, the execution of his system...I see no disconnects. And, true, a fridge only runs for a fraction of the day...but certainly not 2 minutes a day. And why are the USB charger plugs in the AC power strips, which require keeping the inverter on just to charge a phone? Put those on the 12VDC circuit.

And, finally. It sure looks like he describes connecting the inverter to the load terminals on the charge controller. I believe that is what he advocated and it looks like that's what he did. This is not recommended. Here's one manufacturer's comments on the charge controller load terminals:

Some loads should not be connected to the controller’s load terminals and instead connected directly to the battery. Highly inductive loads with high inrush currents may damage the controller’s load terminals. DC motors and inverters are examples.

And here's another:

...you might consider connecting an inverter to the charge controller’s terminals. But is that right? This is it, you should never connect an inverter directly to a charge controller.

It might be acceptable with a small inverter draw, compared to the charge controller capacity...I see 50% bandied about...but, personally, I don't do that.

EDIT to add: I just re-read my post. Man, I'm getting cranky in my old age. But I'm seeing so much bad electrical advice and work that it just irks me.

[rossvtaylor]

It's too late to add an edit, with addition information in my previous post. But I looked up that Grape Solar charge controller, as I'm not familiar with it. The load/output terminals are rated for 20A. It appears that he used that to power a 2000W inverter. 2000W/12V=166.6666666666666666666666666666666 amperes. Despite my extreme depth of precision here, I'm not that good with math. But I think that's bigger than 20A.