Camper upgrade

[Stircrazy]

so I am upgrading the battery in my camper from a 280AH to a 304AH (moved the 280 into the 5th wheel with the other two) and for the last three years I have not plugged it in at home and just let the solar cycle it at a partial charge when not in use. now the wife wants some more creature comforts when camping like 120V appliances and plugs so I am looking at a 2000 watt inverter and wiring a couple more plugs. so I started looking at inverter/chargers and found that renogy makes one for a decent price that in Li mode it will charge to a specific voltage then it will shut off the charge until the batteries hit the bottom voltage. at this point it will turn the charge back on. so there is no charging in between the two voltages. also in custom LI settings you can set the two voltage setpoints to what ever you desire so you could set the upper to 13.6ish V so you can do a top Ballance when it charges up, and the bottom to 12V.

so what I am getting at is if I say, use those two values then set my max voltage in my solar controller to say 13.3V so when actually camping the solar will keep it charged up to 90% max, is this a good idea? or is there some potential issues I am missing?

 

[chrisski]

If I understand what you are asking, you are looking at a Renogy inverter charger That can charge off the grid with a setting to charge to (different than top balance) and then another setting to where it will start charging again.

With this you want to add a charge controller and charge to less than what the other is at.

It should work provided that if the charger turned on when the solar was on that the system was wired and fused, and the battery could take that much charge.

Also, the charge could not be below freezing.

Also, if when I store my lithium batteries which have no real data on how to store them, I first discharge to 50% and remove all loads.

Is there anything in the manual that talks about adding solar?

 

[Browneye]

Not utilizing whatever solar power is available does not make sense to me.
Top balancing is what you do when you build from cells. Balance charging can generally be implemented in bms above 3.4Vpc or thereabouts. And while 13.6 is technically a full charge for lfp, charging to above 14V is generally required to actually get there - there has to be a voltage difference between charging volts and batteries for current to flow. Batteries settle back to a lower voltage once charging is terminated. And they drop even more under load.

Friends don’t let friends by renogy stuff. It’s like a giant crap-shoot as to whether it will actually work or not. [shrug]

Understand that a 2kW inverter could pull 200 amps from your battery. That takes some really big cabling and fusing to accommodate. I would have a serious sit-down with DW. Maybe she’s gonna run shop tools or something. Most kitchen appliances can be sourced with lower consumption.

It might be time to consider upgrading to a 24 or 48V system. Getting 200Ah back for a deep discharge takes a LOT of solar.

 

[Stircrazy]

If I understand what you are asking, you are looking at a Renogy inverter charger That can charge off the grid with a setting to charge to (different than top balance) and then another setting to where it will start charging again.

With this you want to add a charge controller and charge to less than what the other is at.

It should work provided that if the charger turned on when the solar was on that the system was wired and fused, and the battery could take that much charge.

Also, the charge could not be below freezing.

Also, if when I store my lithium batteries which have no real data on how to store them, I first discharge to 50% and remove all loads.

Is there anything in the manual that talks about adding solar?

not exactly, the inverter is for using power off grid but the charger part is for on grid. I leave my rv's plugged in when not in use and was looking for a way to prevent constant charging on the LFP battery which this seams to do. when I am off grid the solar charge will charge it up to about 90% state of charge so when I am cycling it when camping it is going from say 20% (if it ever gets down that low) to 90%.

right now when I get home I have to turn my battery switch off to prevent constant charging and I turn the solar off also, but with the settings on the charger inverter I could leave it plugged in as it will charge to full and then shut off any charge to the battery until it hits a low of what I set, and I can just kill the breakers to my solar controller and turn it off. this would allow me to still use 120v power if I need to work on the camper but not subject the battery to a float charge.

 

[Stircrazy]

Friends don’t let friends by renogy stuff. It’s like a giant crap-shoot as to whether it will actually work or not. [shrug]

Understand that a 2kW inverter could pull 200 amps from your battery. That takes some really big cabling and fusing to accommodate. I would have a serious sit-down with DW. Maybe she’s gonna run shop tools or something. Most kitchen appliances can be sourced with lower consumption.

It might be time to consider upgrading to a 24 or 48V system. Getting 200Ah back for a deep discharge takes a LOT of solar.

if a 2K inverter draws 200 amps something is wrong, or it old and verry inefficient. but ya 200amps would be the fuse and cabling size. I am putting 2000 in because that is what I have in my 5th wheel and runs everything just fine.

so if I put a microwave in I know I'll have enough overhead to run it, I wouldn't go to 24v or 48v in a RV as it is inefficient and just doesn't make since unless you power usage is so high that you cant fit enough 12V batteries.

and as for friends don't let friends buy renogy, I always say real friends don't let friends buy overpriced Victron

I have been using renogy solar controllers for 4 years now in both my rv's , longer in my 5th wheel I am very happy with them. charging wise, my 5th wheel uses about 90ah a day and the Solare has it filled up by a little after noon, my camper well right now it uses about 36ah when camping in the winter and running the furnace 24/7 so with the addition of 120V to charge phones, laptops, maybe run a microwave a bit.. I'm talking 10 min max a day I can see my power usage going up to about 60 to 70ah a day which is still with in the capability of my solar easily.

but yes if I hit a string of bad weather in the lait fall and do discharge deep it will take a few days to totally recover, that's why I built in the extra storage capacity. If I leave the inverter off then I have a 9 or 10 day reserve, that will drop to 4 to 6 days depending on my final usage, but I am also adding a dc to dc charger to the setup to allow me to use the truck as an emergency generator when it is needed.

 

[chrisski]

If you had a MPPT or charger capable of a rebulk voltage, that may do what you are asking.

Set Bulk/absorb to 90% votlage level, and rebulk to the 20% level. Float would need to be off for this, or at or below rebulk.

I don’t have a rebulk option on my Victron, but I do an my Outback MPPT. I am still commissioning my Outback and learning the settings, but Rebulk is one I’m thinking of adjusting because towards sunset, my MPPT is lower SOC than I’d like.

if a 2K inverter draws 200 amps something is wrong, or it old and verry inefficient. but ya 200amps would be the fuse and cabling size. I am putting 2000 in because that is what I have in my 5th wheel and runs everything just fine.

A 2000 watt inverter at low voltage cutoff of 10 volts, pulls 200 amps, plus inverter efficiencies, 85% is typical, so that’s 230 amps.

 

[eXodus]

I turn the solar off also, but with the settings on the charger inverter I could leave it plugged in as it will charge to full and then shut off any charge to the battery until it hits a low of what I set, and I can just kill the breakers to my solar controller and turn it off. this would allow me to still use 120v power if I need to work on the camper but not subject the battery to a float charge.

with LFP there is no real need to turn charging off. (If it's a lithium charger and has the correct settings)

My RV has Growatt All in One Charger / Inverter - and it runs 24/7 all year round.

if a 2K inverter draws 200 amps something is wrong, or it old and verry inefficient. but ya 200amps would be the fuse and cabling size. I am putting 2000 in because that is what I have in my 5th wheel and runs everything just fine.

2000W output at 85% efficiency requires 2352W from the 12V side

2352W /12V = 196A

It is a lot of power and at the edge of upgrading to a 24V or 48V system. But not necessary yet in your case

, I wouldn't go to 24v or 48v in a RV as it is inefficient

Any higher voltage is more efficient in distributing power then 12V. But it may cost more money to setup a second system. (12V+ 48V) so it might be not as cost effective.

 

[Stircrazy]

A 2000 watt inverter at low voltage cutoff of 10 volts, pulls 200 amps, plus inverter efficiencies, 85% is typical, so that’s 230 amps.

who is running a RV lithium to 10V, I stated that I would set the bottom at 12V so it would never pull 166amps and its 90% efficient so that 185amps max.

 

[Stircrazy]

2000W output at 85% efficiency requires 2352W from the 12V side

2352W /12V = 196A

It is a lot of power and at the edge of upgrading to a 24V or 48V system. But not necessary yet in your case

Any higher voltage is more efficient in distributing power then 12V. But it may cost more money to setup a second system. (12V+ 48V) so it might be not as cost effective.

you guys all seam to buy inefficient inverters haha.. the one I am looking at it 90%. my point being that it will be well under 200amps and that I will never run it that high either as I don't know what I have that pulls over 1300 watts.

at distributing yes, but the problem in a RV is 90% of the RV is a 12V system so the process of converting back down to 12V to power everything except your plugs adds another inefficiency and going to 24 or 48V isn't geeing rid of the need for an inverter, so now I am inverting AND converting off 12V, plus the fact that it adds several thousand to the build instead of 500.00

 

[chrisski]

who is running a RV lithium to 10V, I stated that I would set the bottom at 12V so it would never pull 166amps and its 90% efficient so that 185amps max.

How will you set the bottom limit at 12 volts? BMS? Relay programmed to shut off high wattage items?

I call it the guest factor, someone unaccustomed to limits. Someone who comes over who is used to plugging things in the wall, and doesn't understand. The type of person who will think if they just exceed those limits by a few minutes, it'll be OK.

I've had someone plug in an instapot (1000w - 1600w cooking device) after I went to sleep and didn't want to disturb me with the beeping (my battery monitor for a low voltage alarm). I've also had someone exceed current limits for a couple minutes to use a toaster oven.

Most equipment I look at has a low voltage cutoff around 10 or 10.5.

If you deal not with guests, families, or others, than low voltage is no factor, until it is.

 

[Browneye]

Unsub…SMH.

 

[Stircrazy]

How will you set the bottom limit at 12 volts? BMS? Relay programmed to shut off high wattage items?

I call it the guest factor, someone unaccustomed to limits. Someone who comes over who is used to plugging things in the wall, and doesn't understand. The type of person who will think if they just exceed those limits by a few minutes, it'll be OK.

that will be set un the BMS as the bottom limit, but it will also be set in the converter for it to start charging again before that point say at 12.8 or 12.9, but the only way it would ever get this low is if my solar stops working as it will be setup as normal just that it shuts off at 90% SOC. and that may change depending on how the usage goes but that's how I run the solar right now. as for guests , not a factor in a truck camper as its just me and the wife, anyone coming with us has their own camping unit, plus their isn't really any high wattage items being used, yes a microwave, maybe a tea kettle but not all the time just once and a while depending if the grandkids are with us. Basically I run my 5th wheel this way with 480 watts of Solare and four golf cart batteries and I never have to worry about power even if I am running the furnace. so the camper has better solar and uses 1/3rd to 1/2 the power and I just upgraded the two golf cart batteries (104 usable AH) to 300AH of LiFePO4. Now I am looking at adding a inverter/Charger unit so I have proper Li charging profiles and can leave it plugged in when not in use.