RV Solar Calculator

[MelH]

Originally Posted by Rzrbrn

Not easily relocated? Not sure I understand this comment. My trailer is a Big Foot 25RQ. We seldom stay in one spot for more than 3 or 4 days at the most. We may change our modus operandi however, we are perhaps getting to the point where we might set down for a week or two.

One interesting thing I have come across, and this is more of a generic comment regarding lithium batteries: they cannot be used to jump start the truck batteries if the need arises and vice versa. I had to do this one time with my wet batteries. I may have to carry one of those portable jump start battery packs.

When I was designing my system the numbers told me these batteries will last the rest of my lifetime ((5000 cycles * 5 days/cycle for me)/365 off-grid days/year) = 68.5 years.
..My 18' Aliner camper is unlikely to last that long so I assumed I'd want to relocate the system at some time and hold on to my investment. System is easily relocated since there are no added cabin displays to move or holes to patch -- all info sent to phone - not tiny displays. Big Foot campers are looking good for future!

I use about 230Wh/day. I generate about 540Wh/day using my 100W Renogy suitcase solar pack. My single 125Ah (1500Wh) lasts us 5-6 days with no sunshine.
..We 'warm' camp comfortably and occasionally use 1kW inverter to recharge laptop or run DW's lathe for pen turning.
..I recently added a disconnect able "trolling motor" battery case that has 2x12v accessary ports (for USB's, lights), and the 60A 12vdc for other uses (inverter to drive refrigerator, etc.). This "Power Pack" will be used for powering trading booths, tailgating, emergency power, etc.
..System is easily expanded with more batteries, more solar panels, inverter, etc.

Pics, and my 'Design Results' are in the FiberglassRV classifieds under parts and can be used to compare system-to-system advantages.

BTW, LFP batteries are chemically (and often electronically) restrained from high currents. They can't start larger vehicles nor can they overheat, catch fire, or explode like other batteries. Battery University has great reference battery type comparisons.
Best Regards, MelH

[ZachO]

Exciting!

Yes, he meant transferring to a different RV. It's one of those things some people choose to consider and some people don't, and either approach is valid. If you're going to put nearly $6,000 into an RV, which in most cases come and go as our needs and wants change, it's nice to have it easily transfer from one trailer to another.

But in most cases, mounting a solar array is just one of those things that stay with the trailer, like spending $600 on a furnace or $900 on a fridge.

[Rzrbrn]

Transferring to another trailer makes sense, I did not understand what was being said.

Also the project has changed. 6 Renogy solar panels, but now 4 Battleborn batteries and possibly a Victron charger Inverter. I will post here as this progresses.

Turns out Renogy makes great solar panels, but their batteries are inferior as is their charger/inverter, so the installer and I decided to go with other brands.

[Raspy]

Originally Posted by Rzrbrn

One interesting thing I have come across, and this is more of a generic comment regarding lithium batteries: they cannot be used to jump start the truck batteries if the need arises and vice versa. I had to do this one time with my wet batteries. I may have to carry one of those portable jump start battery packs.

Henry,

I don't understand this comment. Why can't lithiums be used to jump start the truck? Thanks.

[Rzrbrn]

Raspy, I have no real understanding of why Lithium batteries cannot be used to jump start. If I recall correctly, I got that from he Renogy website, but I may be wrong about where I came across this piece of info. It has something to do with the LI not being able to discharge a lot of electricity in a short period of time. My RV service guy agreed with it though...come to think of it, the next time I talk to him I will ask why.

I will go back and retrace my information sources, if I come up with the reason I will post it here.

Tpdate: I could not find the reference on the Renogy website regarding this issue, but since I have bought 4 Battleborn GC2 batteries, I emailed the company and asked: 1. Can a LiFePO4 be used to jump start a car battery, and 2. Can a car battery be used to jump start a LiFePO4 battery. I will post here if they respond.

[Raspy]

Henry,

Thanks.

I would hate to have to "jumpstart" the truck from the trailer. In my case, it would require removing a battery from the dinette seat battery compartment and carrying it out to the front of the truck. Instead, my 50 amp Anderson plug and dedicated #6 wiring could "charge" the truck battery in reverse. And if the trailer batteries ever became completely discharged (ouch!) I don't see why the truck could not bring them back up through the same Anderson charging circuit.

You may be right that lithiums are not designed for starter loads of very high amps. But running a microwave in a trailer is a common use, and that could pull over 100 amps from the battery. So maybe an important thing would be to have multiple batteries to limit the amp draw on each one. I don't know what that limit is.

Update:

I just found this on Battle Born's site:

"Our BMS is rated to 3 different levels.

1. 100 amps continuous (1200 watts at 12 volts) – this means you can pull 100 amps out of the battery when you need it until the capacity is all used up. This would be a 1C discharge rate.

2. 200 amps for 30 seconds (2400 watts at 12 volts) – if your device has a surge an individual battery can deliver 2400 watts for 30 seconds.

3. ½ second surge up to the max capacity of the battery. If you have a high momentary over 200 amps the battery will handle this for ½ second.

*Keep in mind that when you have to 2 batteries in parallel you will double these surge numbers, with 4 batteries in parallel you will quadruple these figures."

[ThomasC]

If I want to start something with a dead battery I put a battery charger on it for a half hour or so and then start it up. Thanks to this conversation I'll carry a battery charger with my tools for this.

My Honda generator also has leads for battery charging.

[Raspy]

Originally Posted by ThomasC

If I want to start something with a dead battery I put a battery charger on it for a half hour or so and then start it up. Thanks to this conversation I'll carry a battery charger with my tools for this.

My Honda generator also has leads for battery charging.

That's fine, but battery chargers have to be plugged in. And a generator's dedicated 12v battery charging output is very low. So it's best to plug the charger into the generator.

Jumping a truck to start it, with jumper cables, means an immediate response as opposed to waiting until the battery is re-charged.

If you want to charge your trailer from a generator, it's best to plug the shore tie into the generator and let the onboard trailer charger do the task. Can't do that with the truck, so you'd need a separate battery charger for the truck. And that battery charger cannot be a "smart charger" because they require battery voltage to turn them on. They must sense about 10 volts in order to recognize the battery they are going to charge. So, if you want a charger to charge a dead truck battery while boondocking, use a ferro-resonant charger plugged into the generator. Or, as mentioned, plug the truck into the trailer with an Anderson plug and dedicated wires to the battery. Using jumper cables from the trailer battery is a good idea, but not if the truck is dead, because how do you move the truck to the trailer to hook up?

[Rzrbrn]

I was boondocking last season in my BF and I ran the TT lead acid battery so low it would not state the on board generator. I drove the truck up to it, jumped just long enough to start the generator then let the on board generator charge the TT battery.

I usually try to park my truck fairly close to the from of my BF, but you are quite right, can't move a dead truck to get a charge from a TT battery!

But you never know what odd situation you may find when boondocking.

I still can't find the reference to not using a Lifepo4 battery to jump with...maybe I just misunderstood...I will keep looking.

[Rzrbrn]

2 or 3 seasons ago I had a Casita and the OEM Parallax 7300 converter cooked my battery. I did not know that you can't leave this converter connected to shore power for any length of time. At any rate, my fault for not knowing. But I have to buy a battery charger while on the road to keep the battery charged long enough to both buy a new battery and have the Parallax replaced with a multi state Progressive dynamics convert charger.

So I carried that very large auto zone battery charger around up tp this year. I just bought a NOCO GENIUS10, 10-Amp Fully-Automatic Smart Charger, 6V And 12V Battery Charger, Battery Maintainer, And Battery Desulfator With Temperature Compensation

I use this NOCO as a battery maintainer for my diesel truck, which has 2 batteries.

I am thinking this will replace the much larger Duralast DL-50D.

[Raspy]

Henry,

It seems from what I found on Battle Born's site (see post 108) their batteries are fine for jumping, within reason. A 5 HP diesel starting motor could draw over 300 amps, and for much longer than 1/2 second, so not advisable. That is unless two or three were wired up in parallel. Sheesh, can you imagine the hassle of that while stuck out boondocking!

[Rzrbrn]

Thanks Raspy, Battleborn has not responded to my email as of this moment.

Changing the subject but I also came across a piece of info that I cannot document the origination:

Don't start your Ram truck ( if it has a Uconnect ) while the truck is plugged into a battery maintainer or charger. High probability it will mess up the Uconnect programing.

I have been all over the internet trying to understand how to set up the OEM trailer brake, and vaguely remember someplace stating the above. I finally figured out how to do increase or decrease the gain in my 2019 Ram 2500.

[Raspy]

Henry,

Isn't your brake controller built right into the dash? Mine is on my 2014 Ram 3500. All you do it touch the + or - buttons on it and it will show the value on the EVIC. Am I missing something?

[ThomasC]

This is all more or less stupid math. If you charge at 10 amps for 10 minutes in a perfect world you could get 100 amps for 1 minute or 1000 amps for 6 seconds. Since nothing is perfect you could probably get the 300 amps you need for a few seconds.

I have said before that I am a retired mechanic and have not really had a set of jumpers. Good ones that is. Good jumpers are very expensive. I have always used the charger trick. If I am out and about and someone asks me if I have jumpers, I will say no. It's better not have them than to lie.

If the ten minute charger trick doesn't work you need a new battery anyway.

[Raspy]

Originally Posted by ThomasC

Since nothing is perfect you could probably get the 300 amps you need for a few seconds.

I have said before that I am a retired mechanic and have not really had a set of jumpers. Good ones that is. Good jumpers are very expensive. I have always used the charger trick. If I am out and about and someone asks me if I have jumpers, I will say no. It's better not have them than to lie.

If the ten minute charger trick doesn't work you need a new battery anyway.

Except that Battle Born says loads over 200 amps should not be applied for more than 1/2 second on a single battery.

What "10 minute charger trick" do you mean?

[Rzrbrn]

I wuz wrong...hopefully my wife will NEVER read this thread...

Just got this back from Battleborn:

Hello Henry,

Thank you for the support.

Yes you can use the Battle Born in a pinch to jump start your car battery and can also jump the Battle Born using the car battery. We usually recommend that if the Battle Born has gone into a low voltage disconnect mode.


Thank You,
Roni Ventura

[Raspy]

Thanks for the update Henry,

I guess they mean as long as the load is no more than 200 amps for 1/2 second with a single battery.

(now delete your post so your wife never sees it)

[ThomasC]

Originally Posted by Raspy

Except that Battle Born says loads over 200 amps should not be applied for more than 1/2 second on a single battery.

What "10 minute charger trick" do you mean?

I thought I laid it all out with my back of the envelope math. This is all assuming you have a decently sized inverter, a battery charger, and some life left in your LiFePo battery bank. Ten minutes should give you a few seconds of cranking but if twenty minutes doesn't there are other problems.

Your tow vehicle should be in tip top shape anyway.

[Raspy]

Unfortunately what should be, and what is, don't always match up.

I accidentally ran the battery too low to start my truck one night up in the Sierra. Nine degrees and about 7,000' elevation. No generator, no solar. But I had jumper cables, I ALWAYS have jumper cables. Always.

A park worker came by and I flagged her down for a jump. "We are forbidden to give jump starts, but I can call AAA for you if you'd like" This, as her truck sat next to mine idling. She finally decided that a quick jump would be OK, but as I recall insisted that I hook my cables to her truck, but she would not hook hers to mine.

I would never leave my cables at home just so I had a clear conscience about telling someone in need that I did not have them. For a couple of years, jumper cables was the method I used to charge my Oliver batteries when camping.

[John in Santa Cruz]

Originally Posted by Raspy

Unfortunately what should be, and what is, don't always match up.

I accidentally ran the battery too low to start my truck one night up in the Sierra. Nine degrees and about 7,000' elevation. No generator, no solar. But I had jumper cables, I ALWAYS have jumper cables. Always.

A park worker came by and I flagged her down for a jump. "We are forbidden to give jump starts, but I can call AAA for you if you'd like" This, as her truck sat next to mine idling. She finally decided that a quick jump would be OK, but as I recall insisted that I hook my cables to her truck, but she would not hook hers to mine.

I tried to give someone a jump once and their car melted my jumper cables, they were so hot i nearly got burned disconnecting them and that was before they even tried to start. I don't remember which car I was driving, probably my Volvo 740 turbo wagon, and their car was an older honda. the Volvo had a decent sized battery, in fact the same one in our W124's. ruined a good set of heavy gauge pure copper jumper cables

anyways, I understand the reason for the parks policy. it could kill the ranger's truck and leave them stranded.