Solar panel connections with split charge - a couple of questions

[nickburt]

I already have a split charge system the uses a voltage sensing solenoid to auto connect when the starting battery voltage passes above a threshold, the controller for the solenoid also gives me the ability to manually connect the starting and houshold batteries if needed. (I have a Tmax split charge system).

I'm going to add solar charging soon, and have a couple of questions:

Is it better to hook the solar charge up to the starting battery, or houshold batteries (I have two 110Ah aux batteries)? Given that my solenoid auto links above a certain voltage, or can be linked manually.
If the solar is connected to the starting battery, then this would ensure they are all kept topped up automatically, or would would it be better to connect solar to the houshold batteries and link if needed to the starting battery.

I'm thinking it doesn't really matter and probably comes down to personal preference.

Also, presumably, the solar kit can be left connected (controller and panel(s)), when the engine is running and the alternator is doing the work without risking damage to the solar panels or their controller. I'm assuming here the controllers are protective.

 

[228B]

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...would would it be better to connect solar to the houshold batteries and link if needed to the starting battery.

I cannot say for sure if it would be "better", but this is how I am doing it with my small trailer's "house" battery. I'm leaving the tow vehicle's battery and alternator's work load strictly to the vehicle. One may simply use jumper cables to assist the tow vehicle's starting battery if it was ever necessary...
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Yes, you can have several different types of battery charger connected to the battery at the same time. They only push against one another but as my friend Bob S. says, "nothing blows up". Best to keep it simple, however, and be sure everything is fused properly.
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With a good house battery and some effort into a miniature "off-grid" solar setup, your house battery can give many years' useful service and never need a generator. For example, a few years ago I started with an Engel MT-45 and a good-quality 100 amp-hour AGM battery, thinking when in the field to recharge the battery every other day using a recommended charger powered by a quiet Honda portable genset.
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Today, I have that same Engel, a fresh example of the same battery (I killed the first one through inexperience and several very-deep discharges that went on for days at a time), an excellent small solar setup consisting of a 100-watt panel, a good charge controller, good copper conductors and may never need a generator again. I'm adding an inverter for some over-the-top shenanigans like a vintage electric toaster (600W single-slice), perhaps a blender, etc... in addition to a few "warm white" LED for the trailer's sleeping compartment and it's outdoor galley. I could easily get carried further away with this... hahaha.

 

[dwh]

Personal preference.

If you don't have anything that drains the engine battery, then you don't need to keep the engine battery topped off. I'd hook the solar to the aux battery to get the most watts into it as I can while I have sun, and also to not keep the engine and aux batteries tied any more than is neccessary.

The solar charge controller can protect itself from a battery that is capable of outputting a hell of a lot more amps than the alternator - the alternator won't hurt it.

 

[Talcabin]

Good Thread that brings up a question I've had for awhile, I know its a rare occoasion that it could happen with my setup, but it makes me wonder. I have solar panel, plug in charger, and engine alternator charging options for my aux 2nd battery on my new to me van, and I'm always boondocking.

I have a low voltage disconnect on my engine starting battery from Blue Sea Systems. It completely disconnects the starting battery at a setpoint so you always have engine start capacity. The engine battery is mainly only used for the radio when in my van bondocking, but I suspect there are more parasitic loads on the engine battery that I haven't found yet. I haven't reached a situation where it has disconnected the starting battery yet because I haven't used my van that the LVD is in much as I use my old SUV more often. But I was wondering with these semi-modern vehicles (a 2004 Chevy Express van), is there any detriments to completely disconnecting the engine battery for a few days? I like to stay put in the forest for a couple of weeks sometimes. I mean I know the radio stations and simple stuff like that would go upon a disconnect, which I don't care about, but what about engine computer and controls? I had a mechanic tell me not to let a long term disconnect happen to the engine computer and controls, but that seems like a really bad thing for a vehicle manufacturer to allow. I assume important settings would be kept in NVRAM.

Thanks,
TC

 

[calicamper]

As mentioned only makes sense to have your solar system charging your house batteries also keep in mind if your at some point going to have a fridge the solar system if heavy enough can handle the fridge load and bank some power back into the batteries during the primary solar hours of the day etc. Solar on the starter battery with no load when the car is parked doesn't make much sense.

 

[228B]

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But I was wondering with these semi-modern vehicles (a 2004 Chevy Express van), is there any detriments to completely disconnecting the engine battery for a few days?

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I have a 2003 Ford (well maintained and still running and driving like a new car) that when the battery voltage is disconnected from it's adaptive "powertrain control module" pretty much erases anything it has learned. Granted, there are defaults in it's firmware that are used for initial operation when brought back online but the Owners Guide describes a basic routine to put the vehicle through so that it will easier re-learn and fine-tune things like fuel delivery, automatic transmission shiftpoints, etc... even the raised idle to compensate for the A/C compressor load...
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Solar on the starter battery with no load when the car is parked doesn't make much sense.

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But he has said he doesn't know for sure about any parasitic draw and until he's certain, I'd look for a very small-output solar panel designed to be a battery "maintainter" or, float charger, and hook that up to your starting battery when your vehicle's "powertrain" is dormant for any length of time. Keeping the correct float charge on a battery is a good thing since all batteries self-discharge to some degree.

 

[TotalOverland]

Most controllers should be fine to leave connected. Just remember that controllers will end to consider the charging voltage of an alternator as being a full battery and so the charging via solar panel.

Basically when charging from alternator most controllers won't supply anything from the solar panels. Once stopped and the voltage from alternator drops, the controller will then decide if it can cut back in.

Hope that makes sense!

Richard

 

[AndrewP]

With a split charge system, I'd leave it all connected and take advantage of the solar system topping both batteries once the house battery is holding 13 volts or so. That will cause the voltage sensing relay to close and also charge your engine battery. The "brain" of the voltage sensing relay should open the relay once the system falls below 12.8 volts or so which will protect your engine battery from further discharge. I don't see a problem here.

And one other thing-measure your parasitic drain if you have one. If it;s 15mA, forget about it. If it's 400mA, you have a potential problem. One thing that has given me great peace of mind is to have dual voltmeters installed-one for each battery. I can flip the switch, read both battery voltages and know at a glance if there's a problem.

 

[rayra]

Good Thread that brings up a question I've had for awhile, I know its a rare occoasion that it could happen with my setup, but it makes me wonder. I have solar panel, plug in charger, and engine alternator charging options for my aux 2nd battery on my new to me van, and I'm always boondocking.

I have a low voltage disconnect on my engine starting battery from Blue Sea Systems. It completely disconnects the starting battery at a setpoint so you always have engine start capacity. The engine battery is mainly only used for the radio when in my van bondocking, but I suspect there are more parasitic loads on the engine battery that I haven't found yet. I haven't reached a situation where it has disconnected the starting battery yet because I haven't used my van that the LVD is in much as I use my old SUV more often. But I was wondering with these semi-modern vehicles (a 2004 Chevy Express van), is there any detriments to completely disconnecting the engine battery for a few days? I like to stay put in the forest for a couple of weeks sometimes. I mean I know the radio stations and simple stuff like that would go upon a disconnect, which I don't care about, but what about engine computer and controls? I had a mechanic tell me not to let a long term disconnect happen to the engine computer and controls, but that seems like a really bad thing for a vehicle manufacturer to allow. I assume important settings would be kept in NVRAM.

Thanks,
TC

Lot of temporary memory / engine settings will get lost during a protracted disconnect, and will have to be 're-learned' when the vehicle is re-started. If you re-start with poor fuel, high altitude or any other 'non-normal' factors, your engine settings will then be incorrect / sub-optimum when you retrun to 'normal' conditions, impacting fuel economy, performance and might even foul things up altogether.

Normal 'parasitic' loads should not be an issue. Stick a small cig-lighter panel on your dashboard and forget the problem, instead of using faulty decision-making to create new problems. Besides, that's what the whole 'house battery' concept is about, putting all your camping load on a secondary / isolated battery, so as to not impact your primary / starting battery. The other simple solution is re-wire the hot supply of your stereo to your secondary battery. Lastly, how hard is it to idle your vehicle for a short period every few days? Don't unnecessarily complicate things.

 

[Talcabin]

Thanks guys! really helpful info here - I appreciate it!
I guess the mechanic was right about not letting your engine battery disconnect completely!
Rayra - are you saying to put a voltmeter in the cig lighter to monitor the engine starting battery? I need to upgrade the battery intel in the van.

So, I just checked on things - the van was in the driveway for 3 or 4 weeks while I was away. I think my buddy was in there running the radio for a few hours while helping me finish my VHF install while I was away but it wouldn't start - battery was down to 8.6Volts. I don't plan on being off grid that long and not starting the engine for that long but something seems wrong. Once I'm on the road full time this shouldn't be an issue, but I would like to be able to leave the vehicle for a few days for multi-day hikes/bikes/kayaking/etc and be able to start when I get back.

I'm thinking I'll get a controller that AndrewP describes, put a switch on the radio, and get a better dual battery voltage monitor/meter. I just can't think of what else would be on the starting battery to drain it besides the dashboard radio! I mean no lights were left on, I have zero indicators LEDs or anything that stays on constantly

JC

 

[228B]

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Rayra - are you saying to put a voltmeter in the cig lighter to monitor the engine starting battery?

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I think rayra meant a very small-sized, small-output solar panel plugged into the cig lighter to overcome any "ghost" loads on your battery and to keep it topped off. Remember, all batteries will self-discharge to some degree even without some micro-short-circuit and/or parasitic load drawing a miniscule amount. That cig lighter/power port is a two-way street, like most everything else unless the path of least resistance is gated with a particular kind of diode. You can also put a voltmeter anywhere on any non-switched 12V source.
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And that 8.6V reading at your battery doesn't look good. Might mean that it's pretty much done for any real amp draw in the future. I've done it too.

 

[1Louder]

I have a dual battery setup in my FJ with a National Luna intelligent solenoid and controller. All of my accessories are on my 2nd battery as is my trailer power. I don't have an isolator yet for the trailer 7 pin connector. It is always hot whether my engine is on or off. Current solution disconnect the 7pin from my FJ if I don’t want to charge my trailer battery from my 2nd battery

The goal: Charge the 2nd battery and trailer battery as required. Either via an automatic method sounds like I would need something similar to the National Luna or the non-smart $60 setup well documented on these forums. Manual maybe with some type of switch which choose battery 1 (2nd battery) battery 2 (trailer battery) or both. I have doubts as to whether my 60 watt panel could charge the 2nd battery and trailer battery at the same time/keep up with the load being placed on it.

I am looking for recommendations on a controller. I think it should be waterproof if it is under my hood. Hoping I can make any required purchase ASAP so I can build and test this weekend.
Possibly this one,
SunSaver 10 Charge Controller 12V 10A
by Morning Star
Link: http://amzn.com/B002MQW3H8

Thanks,
Chris

http://www.expeditionportal.com/for...ke-a-cheap-isolated-dual-battery-setup-for-50


Details:
2 Deep Cycle Batteries in FJ
National Luna Controller

Connected to 2nd battery (ARB 37qt Fridge, 2 Ham Radios, CB radio, 1 Dual USB charging port, 2nd 12 volt socket for 2nd fridge when needed)

Trailer battery runs the H2O heater, water pump, lighting, and gas solenoid.

Single Deep Cycle on my trailer
Powerfilm 60 Watt Rollable Solar Panel
Solar Controller in trailer (Allows me to use panel with trailer if it is disconnected from my vehicle)
Trailer has a solar controller so I can hook up

Other Questions:
Does an intelligent solenoid prevent draining the main battery if the 2nd battery becomes low? In other words will it isolate the main battery? It seems like when I have my fridge running both batteries are draining in my vehicle. Nothing is hard wired to my starter/primary battery. All accessories are on a fuse biock on the 2nd battery. I have no parasitic drain on the starter battery. We have checked.

 

[AndrewP]

Other Questions:
Does an intelligent solenoid prevent draining the main battery if the 2nd battery becomes low? In other words will it isolate the main battery? It seems like when I have my fridge running both batteries are draining in my vehicle. Nothing is hard wired to my starter/primary battery. All accessories are on a fuse biock on the 2nd battery. I have no parasitic drain on the starter battery. We have checked.

Yep-that's the whole point of a Voltage Sensing Relay. If either battery drops below 12.8, the relay will open and thus isolate the the two batteries from each other, so there is no way for the main to drain into the house.

Also, there is no reason you can't have more than 1 VSR, So you could have one between your main and your house and between your house and your trailer. Then all the loads get separated from each other when the engine is off. The Blue Sea units are often set up like this in boats. If you are not set on the NL unit, you might look at the Blue Sea Automatic Charging Relays, which is their lingo for voltage sensing relay.

BTW-I've had good luck with the Morningstar SunSaver 10 to control a 100 watt panel.

 

[1Louder]

BTW-I've had good luck with the Morningstar SunSaver 10 to control a 100 watt panel.

Thanks for the info. I am going to have to do some testing while everything is sitting in my driveway. Hopefully all of the solar stuff will be all hooked up this weekend. I went with a Sunforce controller simply because that is what is in my trailer. If I have any issues I will look at the one you recommended. It looks good. One nice thing on the Sunforce is it does show current voltage.

 

[1Louder]

DIY Solar Controller Box

I wanted to have the ability to more my panel from my trailer to my vehicle and be able to share it with others if needed. So I build a small dry box setup that has the controller inside and SAE ports for the panel and battery. It will also keep the dirt out of the panel. The box is just large enough that I can store the required cables in it as well. I use SAE on all of my stuff and have another cable with alligator clips so I can hook my panel up to any battery.

Showing battery voltage

Battery is being charged by my PowerFilm rollout panel

Temporary placement for testing purposes.

I will be testing this setup this weekend with the vehicle by itself and the trailer hooked up to see what kind of output I can get.