Good Sam Club Open Roads Forum: Tech Issues: Solar/Inverter Question
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flyfishing48

Green Valley AZ

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Posted: 04/19/21 02:33pm Link  |  Quote  |  Print  |  Notify Moderator

Long time RVer, new solar user.

Just bought a new fifth wheel that came with solar. Equipment is:
One solar panel that I think is around 170 watts, a Zamp Solar Charge 30 amp Controller, a Xantrex X2000 Inverter. I should add we have a pair for 6 volt 235 AH Deep Cycle (Crown) Batteries.
Just did 3 nights dry camping, despite being in AZ, it was light overcast for the 3 days. System seems marginal under these conditions for using some lights, water pump for normal stuff, ran the furnace one morning for a few minutes and ran the coffee pot each morning. I did notice the solar panel is dirty from a desert shower on the previous trip. So that didn't help the cause I am sure.

I am not getting my mind around how to run the inverter. Mostly confused about what mode use, Auto On, standby, power save ?

Keystone mounted the inverter off the floor joist in the basement, so not to accessible for use. I will be getting the remote for it.

But I would love to hear from some experienced user about how to best use this system.


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Lwiddis

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Posted: 04/19/21 04:01pm Link  |  Quote  |  Print  |  Notify Moderator

The minimum is one solar watt per battery amp hour. This is a very common issue leading to “my solar didn’t recharge my batteries...it doesn’t work!” You need at least 65 more watts. I’m 240 amps with 300 solar watts.


Winnebago 2101DS TT & 2020 Chevy Silverado 1500 LTZ Z71, 300 watt solar-Lossigy 200 AMP Lithium battery. TALL flag pole. Prefer boondocking, USFS, COE, BLM, NPS, TVA, state camps. Bicyclist 14 yr. Army -11B40 then 11A - (MOS 1542 & 1560) IOBC & IOAC grad


CA Traveler

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Posted: 04/19/21 04:31pm Link  |  Quote  |  Print  |  Notify Moderator

You're light on the panel for that usage. If you really want to know more then install a decent battery monitor. This will allow you to measure every DC device power usage for your house batteries. ie A much more accurate energy audit.

AC devices run from a inverter use a lot of DC power. A 800W unit draws 6.7A AC or about 74A DC. If on for only 10 minutes thats 12Ah which may not seem like much. But you have 120Ah to the 50% discharge level. So that one device uses 10% of your Ah. Recommend you keep the inverter turned off and use one of the other non electric options.

Also IF your batteries were 100% on day one it's very likely that they were lower on days 2 and 3. Let's assume 80% so now you have 30% left to the 50% or mark or about 70Ah to the 50% mark.

All of the math aside a decent battery monitor would display the battery charge left (SOC) and you would be well on the road to conserving or upgrading.


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Bob


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Posted: 04/19/21 04:35pm Link  |  Quote  |  Print  |  Notify Moderator

BTW My charger/inverted cannot be turned off. When you push off it's actually in standby drawing power. Likewise with the inverer on devices like TVs may be in standby drawing power.

theoldwizard1

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Posted: 04/19/21 04:56pm Link  |  Quote  |  Print  |  Notify Moderator

CA Traveler wrote:

All of the math aside a decent battery monitor would display the battery charge left (SOC) and you would be well on the road to conserving or upgrading.

Victron makes some very nice battery monitors. Even their basic model works well.

flyfishing48

Green Valley AZ

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Posted: 04/19/21 10:21pm Link  |  Quote  |  Print  |  Notify Moderator

Thanks for all of the replies so far. This is great info. I will be adding another panel and looking for a battery monitor.

valhalla360

No paticular place.

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Posted: 04/20/21 05:48am Link  |  Quote  |  Print  |  Notify Moderator

Lwiddis wrote:

The minimum is one solar watt per battery amp hour. This is a very common issue leading to “my solar didn’t recharge my batteries...it doesn’t work!” You need at least 65 more watts. I’m 240 amps with 300 solar watts.


Rules of thumb can often be way off the mark. Also unless you go to extremes, it's just a question of time to recharge not if it recharges.

Do an energy audit.

Figure out what devices you are running and how long they are running. Each device will have a wattage rating listed on it.

Watts * Hours = Watt-Hours

Add them all up to get the total used.

6v * 235 amp-hr * 2 batteries = 2820 watt-hours in the battery bank but you can't use all of those for lead acid batteries, you don't want to drop below 50% or about 1400 w-hr if you start from full.

Solar panels don't put out their max rating except under perfect conditions. A good estimate is 4-5 times the rating in w-hr, so 170w panel will generate around 680 w-hr per day.

So if you are consuming 1200 w-hr per day, after the first day, you will be down to around 800w-hr available in the battery bank, after the 2nd day, you will be down to 200 w-hr.

Of course, you want to factor in some inefficiency as battery banks are not perfect at charging and as you mentioned, dirty panels don't put out as much...so in reality, after 2 days, you would have used all the power you can without risking damage to the batteries.

For a 2-3 day weekend trip with light use, your system should be OK but you really need to watch your usage.

If you are doing longer trips, I would lean toward more solar so you are mostly replacing what you used.
If you are just using more but only for 2-3 day trips, adding a couple more batteries may be simpler and then let them charge off the solar during the week when you aren't drawing any power.


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flyfishing48

Green Valley AZ

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Posted: 04/20/21 08:38am Link  |  Quote  |  Print  |  Notify Moderator

Great info. Thank you.
If I add more batteries would my shore power system handle charging them ok?

CA Traveler

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Posted: 04/20/21 08:42am Link  |  Quote  |  Print  |  Notify Moderator

valhalla360, Intersting post as very few use Wh for RV power usage. It's a more accurate measure of power of course but Ah is commonly used or even just amps.

CA Traveler

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Posted: 04/20/21 08:45am Link  |  Quote  |  Print  |  Notify Moderator

flyfishing48 wrote:

Great info. Thank you.
If I add more batteries would my shore power system handle charging them ok?
Yes, it will take longer but on shore power not a concern. It can be a gen run time concern, however.

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