Solar Geeks Needed

Electrical issues, both 12 volt and 120 volt
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Wanderwasi
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Solar Geeks Needed

Post by Wanderwasi » Thu Jul 12, 2018 12:47 am

We're installing solar on our rig and had a few questions. We've done a solar install on our travel trailer but with the house battery & generator it's a little different and don't want to miss something on the van.

3 - 100 watt panels for the roof.
2 12V 100 amp hour each AGM batteries
30AMP MPPT solar controller
Inverter - we have an crazy overpowered 3000W (totally unnecessary) for our trailer and are looking for suggestions on 900-1000w inverters that go into standby mode so they aren't constantly drawing when there is no load. I've been looking at Xantrex and Samlex.

The questions come in when we hope to keep the current lead acid battery under the hood as well as the new AGM's, one because we just bought it and two because we have 100W portable panels we figure we can put to use and three, extra amps are always good! I know we can't hook it up with the AGM's because it's different...we just want to simply keep it powering what it's already powering...basically the lights, pump and probably keep the furnace on it too and one 12v outlet. We still want the generator, when on, to power up the outlets. But can we hook things up so if we do run the generator it will charge the old house battery AND top off the AGM's? Is that even possible to wire? Should get go ahead and get a new charger/converter while we're at it? When on shore power, is it possible to have it charge the AGM and the old house battery?

I don't care about charging the AGM's while driving.

Should we just ditch the old house battery for simplicity? I think we have a pretty good grasp on wiring if we don't include it so it's really throwing us off. (You can all point and laugh if it's super easy!)

Thanks!!

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skater
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Re: Solar Geeks Needed

Post by skater » Thu Jul 12, 2018 7:09 am

I think you need a two-bank charger like this.

That said, I'm not sure what you plan to run on the AGM batteries. Also, the furnace draws a LOT of current; you'd probably run down a single battery overnight with it. Splitting the circuits like you describe is possible, but would require rewiring the fuse panel, or a second fuse panel, or something. It seems like it would add a lot of complexity to the wiring, which would be a headache if a problem ever cropped up, especially if you're not the one working on it.

Instead of rewiring the fuse panel, I would add a switch that lets you pick between the two banks of batteries; when one gets low, just flip to the other one.

I'm not sure the complexity and cost is worth it, though - I'd be tempted to replace that different battery, maybe sell it to someone who needs a good condition deep cycle battery, and just add the third battery to the single bank.
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tdashmike
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Re: Solar Geeks Needed

Post by tdashmike » Thu Jul 12, 2018 9:08 am

If you really want to keep it I would use a switch like Skater mentioned but I would not mix the batteries and charge them at the same time unless I carefully monitored them for a couple of charging cycles. It sounds like you only need the AGMs to power the inverter and the MPPT is only hooked up to the AGMs also , if that is the case then it's quite simple.

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190-b-651
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Re: Solar Geeks Needed

Post by 190-b-651 » Thu Jul 12, 2018 9:33 am

If your planning on putting the agm batteries on your original converter dont! It only charges ar one voltage and will kill your new batteries quickly. You need to replace it with a new smart replacement that charges in three stages. Same with your solar controller agm batteries have different charging needs than lead acid. 14.2 is about max for a agm where a lead acid 14.8 is about the max. I replaced my original with this converter. "Pictured "
My solar it totally isolated from the two lead acid under the hood. Two 110ah group 31 agm batteries one 240w solar mornigstar controller panel and all the monitoring systems. I can run lights and heat for two days on one battery I recently added the second one and the monitoring system and rewired all of it with #4 super flexible wielding lead. The system charges on shore, solar, or generator power. ImageImageImageImageImageImageImageImageImage

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Kentuckian
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Re: Solar Geeks Needed

Post by Kentuckian » Thu Jul 12, 2018 10:18 am

Great questions.

Q1) But can we hook things up so if we do run the generator it will charge the old house battery AND top off the AGM's?
A1) Yes

Q2) Is that even possible to wire?
A2) Yes, it can be wired to accomplish that. However, you would be choosing to use dissimilar batteries so it goes beyond wiring as you will need to add additional electronic hardware into the system. Two dissimilar 12 volt batteries can be used in the same circuit. However, one of them is going to have its life expectancy reduced. Therefore, it is best to charge and use the dissimilar batteries independent of one another. Skater gave some examples of how to do this.

Q3) Should we go ahead and get a new charger/converter while we're at it?
A3) At some point you will want to have a multi stage smart charger versus the single stage converter that was originally installed in the earlier B190s. Single stage chargers are fine for charging the first 90%+ of your battery. However, the problem is that they don’t step the voltage down after the battery is charged and will accelerate water boiling out of the battery leading to the lead plates sulfating and shortening battery life. If you have a single stage charger now, you can still take advantage of its higher current output to charge the battery up to 90-95% of capacity and then manually turn it off, letting your solar finish the charge and maintain the battery while sitting. (This assumes that you selected a capable solar charging system.)

Q4) When on shore power, is it possible to have it charge the AGM and the old house battery?
A3) Same answer as above number 2. Just remember that your system plan includes four charging methods.... Alternator, solar, converter, and generator. You would need to wire each one of those so that each of those charging systems is charging each dissimilar type of battery independently. Skater's suggestion of a switch to select between each of the battery banks would be the least expensive way to do this.

When I evaluated doing the above for my own system, I decided to eliminate the battery under the hood and use three identical deep cycle batteries as my battery bank.

I'd suggest reading some of the content on the following website. The author is very opinionated (just enjoy that for its entertainment value!) but he has some very sound information on RV solar / battery system design considerations.

https://handybobsolar.wordpress.com/
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Wanderwasi
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Re: Solar Geeks Needed

Post by Wanderwasi » Thu Jul 12, 2018 10:37 am

Maybe we'll just add a third AGM...probably makes more sense and we really don't need wiring and switch headaches. We are trying out the Renogy 100amp batteries which seem to be the most affordable. We have LifeLines in our trailer which have served us very well but for the price difference, we're willing to give the Renogy a try! Plus, if I sell the portable solar panels, it will pay for most of another battery and those things are a pain to haul around anyways!

Adding a new converter/charger! Thanks for the tip. Didn't have that issue with our newer trailer so we had overlooked it.

The solar controller we are getting is good for lead acid, AGM or Lithium so we're set there as well.

Thanks for the tips and the push towards the easiest direction!

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190-b-651
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Re: Solar Geeks Needed

Post by 190-b-651 » Thu Jul 12, 2018 10:40 am

Kentuckian's Explanation is definitely better than mine lol
But another point is if you plan on monitoring all of you system current in and out with a shunt. Now your going to complicate things even more all grounds run thrue it even your alternator everything in or out! Here you see the shunt below the ground bus all grounds hook in here and one lead to the battery from this point back. Thats exactly why I cut the batteries under the hood out of the system the group 50 isnt worth messing with for the headaches involved. ImageImage

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Kentuckian
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Re: Solar Geeks Needed

Post by Kentuckian » Thu Jul 12, 2018 2:57 pm

If you have not already purchased the MPPT controller, I would take a look at Bogart Engineering's Trimetric power meter and their new solar charge controller. Like 190-b-651, I also use the Trimetric meter. Liked it so much, I am on my third install with Bogart's hardware.

Among the good points of that meter is that it calculates percent of capacity based on measuring actual amps in and out of the batteries. Many battery meters only estimate battery capacity based on present voltage. Present voltage will not accurately reflect battery capacity when the system is under a heavy current load.

Bogart's new solar charge controller will work as a stand alone charge controller but is designed to integrate with the Trimetric meter for optimum control and configuration. I installed Bogart's latest Trimetric meter and charge controller on our B190 about 6 months ago and it works flawlessly and at a reasonable price.
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Wanderwasi
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Re: Solar Geeks Needed

Post by Wanderwasi » Wed Aug 01, 2018 4:21 pm

Thanks for everyones help.

We decided to go with the Victron 100/30 solar charge controller with bluetooth. No need for a battery monitor because it will all be available on our phones which actually saves a bit of $$. We're going with a smaller inverter since thinking about it, we don't have much to power. Having trouble finding a 300W pure sine so will probably have to go with 600W. We're just going to take the house battery out and use the two AGM's we bought so avoid any mix/match issues. We did get a new charge converter, 45 amp so thanks for that suggestion! Ready to install the solar this weekend as my husband leaves for Burning Man in a couple weeks and we're taking a slow trip back with the van from there.

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Kentuckian
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Re: Solar Geeks Needed

Post by Kentuckian » Wed Aug 01, 2018 7:41 pm

If I was going to buy a 300 watt inverter today, this is the one I would buy.

It is pricey, but has many advantages over less expensive inverters. It is pure sine wave so there is no risk of it not being able to power sensitive electronic devices as might be the case with a less expensive modified sine wave inverters. For example, I have an induction hot plate with solid state controls that won't run on three of my modified sine wave inverters. It runs fine on pure sine wave.

The Suresine's effective design results in very low current draw when it is sitting idle (easy on your house batteries) and does not require an internal cooling fan. No fan also means it is quite. Morningstar makes top knotch products.

https://www.morningstarcorp.com/products/suresine/
1993 Airstream B190 w/1991 Chevrolet Tracker tow car

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