Beginner Designing questions: converting Truck Camper to Solar/LiFePO4

[Cdkipp]

Once you make the decision on a 12 volt inverter you really are locked into 12 volt. Zwy's system makes sense. You are asking questions but don't want to listen jungry. Sorry to be harsh about it but you have made two bad impulse purchases in a row on the Renogy equipment. Also, your wfco is not going to charge a DIY pack with the flexibility you will want. Zwy now has a system leagues ahead of you and has spent less money, less complicated, less space and less weight. You have ignored everyone's advise here.

 

[Whinny]

One of the inputs to the transfer is pass through-no power is required to operate the relay, you want that for the inverter power path. When you plug in the relay will operate and provide that path. The relay does consume power to hold. It depends on the way the ATS connections are marked.
Usually the "generator" side is the one that operates the ATS, so you would want to use that side for the shore power connection.....

OK? I think I just confused myself......

 

[jungry]

Some say impulsive, i say decisive. That and I've never wired anything up before and have a finite amount of time to do so. Can you explain why the convertor won't work right with my system? Also the 600 volts at 50 amps from the DC-DC charger ought to make up for something eh?

Also- before you judge me again and explain the WFCO not working, can you answer if I can simply ground the DC-DC/MPPT to something in my panel or do I have to run another 4 gauge wire all the way back to my starter battery? Or can I simply wire the left over welding cable to the vehicle frame?

Whinny, so one of the inputs is naturally a closed circuit on the ATS, usually the shore power side? Then it switches to the other path which takes some load to maintain a closed circuit? Is that correct?

 

[Whinny]

Yup on the ATS
I would wire both pos and neg back to the battery for the dc-dc
I wouldn't consider 24v all in 1 for a camper
your WFCO will charge your batteries-just won't do it that quickly
I don't think I would buy a Renogy inverter-their support seems not that good but if it was a good deal.....is it LF or HF tech?

 

[Zwy]

Yup on the ATS
I would wire both pos and neg back to the battery for the dc-dc
I wouldn't consider 24v all in 1 for a camper

Why not? If you want run an inverter over 2000w, it starts to make sense to go 24v.

Just gets way too inefficient to me on 12v.

your WFCO will charge your batteries-just won't do it that quickly
I don't think I would buy a Renogy inverter-their support seems not that good but if it was a good deal.....is it LF or HF tech?

Post #17 he has LF.

 

[jungry]

I checked per your recommendation before I bought it, it's a low frequency, iron core transformer. They're having an earth day sale, it weird, its not listed on sale but I got $55 off for earth day + the 10% for using the "WIllProwse" coupon.

 

[jungry]

I needed something to charge my lead acid battery now, and i need a 12 volt inverter for my Prius because it doesn't use 24 volts, it uses 12. Troll me about it some more, please, you'll feel so smart...

 

[Whinny]

I don't think 24v is any more efficient than 12v as far as inverters go, wire and fuse size-yes...
Sorry-missed the LF in #17...

 

[Zwy]

I don't think 24v is any more efficient than 12v as far as inverters go, wire and fuse size-yes...
Sorry-missed the LF in #17...

Yes, a 24V inverter is more efficient for same wattage than a 12V. Part of the reason is just VD to the inverter thru the cable.

From this page: https://earthshipbiotecture.com/what-is-the-advantage-of-a-24v-system-over-a-12v-system/

You can get much bigger inverters on 24V or 48V than 12V. There are a number advantages in opting for a higher DC supply voltage.

– For any given load, half the DC current and losses are down by ¼. Reduced fire risk.
– Better input regulation. 0.5v line drop at 12v = 4.6% supply drop whereas 0.25 v line drop at 24v = 1.04% drop.
– Better inverter efficiency and regulation. i.e. Less losses converting to 240 VAC. An inverter doesn’t have to work as hard to keep its AC output constant.
– Larger usable operating voltage window (for acceptable DOD) available from batteries.

Up to 3kW max demand a quaility 24 volt inverter would still be ok.. the rule of thumb is max current demand from inverter should not be over 120-140amps. If over 3KW indeed go for 48 volt system. 150 amps is the limit for cost effective cabling, switching, breakers & fusing.

Note the input regulation concerning VD alone.

 

[Whinny]

A 24v inverter may be 3% more efficient but for the intermittent use in an RV I don't think its worth considering. A 24-12 step down would run more hours during the day and their efficiency isn't that great either.
I wouldn't consider voltage drop or risk of fire? an issue either. Using large enough cabling and short runs has worked fine for any install I have done and I measure the voltage drops after install and usually every year to check for corrosion or bad crimps.
just my thoughts......

 

[Cdkipp]

Yup on the ATS
I would wire both pos and neg back to the battery for the dc-dc
I wouldn't consider 24v all in 1 for a camper
your WFCO will charge your batteries-just won't do it that quickly
I don't think I would buy a Renogy inverter-their support seems not that good but if it was a good deal.....is it LF or HF tech?

You really have absolutely no idea whether the WFCO can appropriately charge lithium or not. You know neither the model number or the amp rating. Why wouldn't you consider a 24 volt all in one? The 24 v growatt all-in-one ZWY discussed above has far more flexibility and is much higher-powered than what jungry has purchased. I have run my RV (I full-time) off a 12 volt inverter for years and now use 24 volt. I would never go back. You are pushing half the amps. Much less heat generated and yes heat does equal a drop inefficiency I use expensive components but there is every reason to believe that Growatt is at least as good as quality as Renogy. He has already spent more than a growatt would cost. Using heavey high end compenents vs an all in one like Growatt is a serious debate. Using a growatt vs Renogy is not.

 

[Cdkipp]

Some say impulsive, i say decisive. That and I've never wired anything up before and have a finite amount of time to do so. Can you explain why the convertor won't work right with my system? Also the 600 volts at 50 amps from the DC-DC charger ought to make up for something eh?

Also- before you judge me again and explain the WFCO not working, can you answer if I can simply ground the DC-DC/MPPT to something in my panel or do I have to run another 4 gauge wire all the way back to my starter battery? Or can I simply wire the left over welding cable to the vehicle frame?

Whinny, so one of the inputs is naturally a closed circuit on the ATS, usually the shore power side? Then it switches to the other path which takes some load to maintain a closed circuit? Is that correct?

"Also- before you judge me again and explain the WFCO not working" Here is my concern. There are various WFCO units under the Mighty Mini or whatever they call themselves. Progressive has always, and remains, severely behind in the lithium battery charger game. A big part of the problem is that they want to make a plug and play solution but ideally, for a LifePo4 pack, especially a DIY lifepo4 pack, you want the flexibility of establishing your own settings. So right now I think you should address two big issues:

(1) Do you really have a Mighty Mini 45 amp charger that has a lithium switch? There are many units that don't have it that are also called 45 amp mighty mini's.
(2) If it does have a lithium switch is that really the solution you want? The lead-acid WFCO will take you to 13.6 volts and then goes through the lead acid absorption float etc that are not intended for lithium. But if you used the lead acid mode and charged to 13.6 volts that would translate to 3.4 volts for each lithium cell. Once you get into looking at doing your DIY pack you will see that the range of a lithium cell is 2.5 volts to 3.65 volts. However, the cells really have most of their power in the range of 3.0- 3.4 which would translate to 12 to 13.6 volts. So the lead acid setting gets you 13.6 which isn't horrible but is not fully charging the lithium and we don't know exactly what is happening in the lead acid smart charger set up. Lithiums like to be charged and let go while lead acids love to be brought to voltage and held so we can assume that the Progressive Dynamic lead-acid profile is not a good match for a LifePo4 pack because it only goes to 13.6 and applies a lead-acid charge profile to a lithium battery. Will it work in a pinch. Yes. It is not ideal but it will not harm the lithium in the short-term usage and actually is preferable to their lithium setting. Why? The lithium setting takes the battery to 14.6. 14.6 translates to 3.65 per cell. This sounds good at first but it is not. I don't think anyone in the Lithium part of these boards would recommend charging your cells up to 3.65 each cycle. Typically that is done a few times in the life of the cells when you are balancing the cells. Most folks will charge up to about 14 volts or 3.5 volts a cell and stop. There is nothing to be gained and only risk by going higher. You are inviting trouble. Once you get your LifePo4 cells and observe them on your BMS you will see exactly what I am talking about. So how did progressive come up with their "lithium" profile? Well it really is a charge that works with drop-in batteries, specifically Battelborn. Battleborn doesn't care. They can make that charge level work because they are relying on there internal BMS to do the shutdown---but that certainly does not translate to an ideal solution for DIY packs where the flexibility and control is one of the big assets in addition to the lower price. This gets us back to why I am pushing you toward high-end components or an All-in- One. Once you get down the road with a DIY lithium pack you will be kicking yourself. A question you should focus on now is how will you control the charge and discharge of your lithium pack. You have talked about Overkill Solar BMS which are great but the majority of us do not use them to control our pack but rather as a failsafe when something goes wrong. You want a charger that you can set to charge to this specific voltage and absorp for this time period. The progressive cannot do that. You want an inverter that you can say take the voltage down to this specific voltage and then stop. Your Renogy inverter cannot do that. You are getting yourself in a bind. Use a gas inverter/generator on your trip and stop this rush so you can do this right.

 

[jungry]

I'm installing the DC-DC/MPPT for the trip not the inverter, the inverter will be used on the prius now, not the camper. The lead acid battery currently inside the camper will be charged by the DCC50S, while I'm driving every 2-3 days. The prius can charge the house or the camper batteries.

When I get the lithium cells I may install the inverter in the camper or keep it in the prius. I appreciate the information about the WFCO and may install another charger in the future.

 

[12VoltInstalls]

Do not ‘ground’ to the frame of a vehicle UNLESS there is a battery to frame cable of AT LEAST the max amp rating of the expected load. Even many new vehicles do not have high-capacity grounds from the battery-body-frame for much more than lighting purposes. People install winches and stuff on trucks (and get away with it sometimes) but you have to know the capacity to return the load is there. If the distribution panel is cabled to the frame then I’d still- if it were me- terminate the ground at the panel. That’s for low voltage. Safety and performance are the reasons

For 120VAC you really need to be aware of what the green or bare copper needs to ‘see’ for safety.

 

[jungry]

Good to know, I used 4 gauge wire, 150 amps (?), it should cover me, the air conditioner is 17 amps.

 

[jungry]

Update to this old post:

I ended up grounding to the frame and installing a 4000watt Giandel inverter; the Renogy DCDC 50 was able to keep my 560 amp hours of LiFePO cells charged over a 30 day road trip, with 4-6 days between driving stents, 2 years later system is still working great. I went with the Giandel because the Renogy inverter I ordered never ever came. I got the run around with their customer service while I tried to find out when the unit would arrive, and then it never arrived. The "Go Power" TS-30 switch works great, however the way I wired it, have to remember to turn off the battery switch when I use the inverter so that the TS-30 doesn't send power to the shore power charger (my batteries would end up trying to charge themselves.)

During the road trip I ran the AC only once when we ate dinner in the camper in 96 degree Boise. The system ran the AC for about 60 minutes (without solar panels) and then we hit the road and charged up the cells. My AC only draws 17 amps.

I am currently prepping for a trip to Mexico and have finally got around to installing the 500 watt solar array, it's winter now so I don't plan on needing AC, but who knows. I might head down there again in summer, given how well the system has been running over the last 2 years I think the solar panels will enable a 2-4 hours of AC per day, likely more.