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diy solar

Charging 24v lifepo4 batteries with a 2500w champion generator.

upsman123

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Joined
Jun 15, 2024
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18
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pagosa
I would like to charge my 2 litime 12v 230ah batteries with my 2500w duel fuel generator when I don't have much solar input. Right now I have 10 hyperion 400w bifacial solar panels and I bought a victron 100v/30a smart charger. I was only able to series 2 solar panels before it said it was overloaded. As we are headed into winter months and as I don't have a lot of space for solar paneld or money to get a huge mppt. I was trying to figure out the best space.v.money.

I am in a space right now that doesn't get a lot of sun during winter and need a solution for charging the batteries. I am also unsure if I have messed up my solar panels as even with full sun hitting them I only got 400w of input. I should also mention I had tested out 50' 8awg solar extension cables.

I am just learning with my first solar set up and would like alternate solutions and tips to get through the winter. I know my rv runs about 400w to power on normal circumstances and I am running my 2500w generator I would like to make the most by charging the batteries.
 
I would like to charge my 2 litime 12v 230ah batteries with my 2500w duel fuel generator when I don't have much solar input. Right now I have 10 hyperion 400w bifacial solar panels and I bought a victron 100v/30a smart charger. I was only able to series 2 solar panels before it said it was overloaded.

Sounds like you got very lucky. Exceeding 100Voc on the MPPT is the best way to destroy it. If it actually logged a voltage > 100V, the warranty is void.

As we are headed into winter months and as I don't have a lot of space for solar paneld or money to get a huge mppt. I was trying to figure out the best space.v.money.

I am in a space right now that doesn't get a lot of sun during winter and need a solution for charging the batteries. I am also unsure if I have messed up my solar panels as even with full sun hitting them I only got 400w of input. I should also mention I had tested out 50' 8awg solar extension cables.

Ummm... a 100/30 can only output 30A. The MPPT 100/30 clearly indicates a maximum output of 440W on a 12V system, and that will vary with voltage, i.e., you'll only get that at 14.6V. At lower voltages, you'll get less.

You need to confirm that the 2S array can't possibly exceed the 100V in cold conditions. If their Voc is < 40V, you're good down to about -35°C. If you parallel panels, the Isc of the entire array can't exceed 35A. Guessing at their Isc to be around 14A, you'll only want 2P.

So on that controller, a 2S2P (1600W) array can be run, but you'll never more than 30A * battery voltage out of it. If you're desperate for electrons, I'd do it.

I am just learning with my first solar set up and would like alternate solutions and tips to get through the winter. I know my rv runs about 400w to power on normal circumstances and I am running my 2500w generator I would like to make the most by charging the batteries.

You need a charger that converts your generator AC output to DC charging. Most RVs have an AC to DC converter that does this when on generator or shore power.

If your RV uses 400W continuously, that's a lot of juice. Your batteries can run your RV for about 15 hours.

At ~400W peak solar, you'll never catch up.
 
Alright I will try and digest. Like I said I am still very new to the solar world. I think at one point I did exceed the 100v when I hooked up a third solar panel in series but it was not in the peak hours of solar generation and I cut it off quick when I got the warning.

I understand that 400w for maybe 4-5h a day is not enough power to charge my batteries. I am also unsure of why it was only inputting 400w as it had full sun exposure with 2s solar panels. I have had 800w+ 2weeks ago at peak solar times.

Also my rv only gets about 100-200w draw at night when we are ready for bed. The 400 is when our peak hits and we are running appliances. We have internet and heat kicking on and off at night so unobserved wattage is about 100-300w at night.

What I am after is that I am willing to run my 2500w champion generator to cover but I am unsure how to get the excess power it is generating back into my batteries. I have seen people say run multiple chargers. I have also seen to not run 80% of your generators capabilities.

Is there a way to take at least a 1000w of my excess energy from my generators watts to charge my batteries?
 
I am not trying to dig my own hole but I do have land that is accessible by foot and as I said I have 10 400w bifacial hyperion solar panels. The land has about 2-4h more of sunlight down there. Would it be worth getting down there and setting all of the solar panels on a mppt that could handle it then converting it to the 24v I am trying to deal with now?
 
I am not trying to dig my own hole but I do have land that is accessible by foot and as I said I have 10 400w bifacial hyperion solar panels. The land has about 2-4h more of sunlight down there. Would it be worth getting down there and setting all of the solar panels on a mppt that could handle it then converting it to the 24v I am trying to deal with now?
Yes, you could run those panels on two circuits, each using an 80A MPPT.
 
Alright I will try and digest. Like I said I am still very new to the solar world. I think at one point I did exceed the 100v when I hooked up a third solar panel in series but it was not in the peak hours of solar generation and I cut it off quick when I got the warning.

Step 1 for a newbie is to look at the specifications of the equipment. If you don't understand what they mean, ask. the 100V is a hard limit on that controller.

I understand that 400w for maybe 4-5h a day is not enough power to charge my batteries. I am also unsure of why it was only inputting 400w as it had full sun exposure with 2s solar panels. I have had 800w+ 2weeks ago at peak solar times.

ah. I now see it in the subject. I apologize. You indicated 24V there, but you did not in your post. Since you mentioned 12V batteries, I assumed a 12V system. The 100/30 can indeed do 880W at 24V.

Max PV occurs at high noon (or 1pm if DST) with your panels facing South and perfectly perpendicular to the sun without a stitch of shading on any portion of the panel. Shading of any kind, even partial, can be devastating to PV output. Output is less at all other times. Looks like this (obviously specific to "Pittstown" on 10/3/2019, but it's intended for illustration purposes):

1728182373143.png

If your batteries are near full, then the MPPT will only produce what you need to charge batteries and power loads.

If panels are flat on the roof or subject to shading/partial shading, output can be notably less.

Also my rv only gets about 100-200w draw at night when we are ready for bed. The 400 is when our peak hits and we are running appliances. We have internet and heat kicking on and off at night so unobserved wattage is about 100-300w at night.

What I am after is that I am willing to run my 2500w champion generator to cover but I am unsure how to get the excess power it is generating back into my batteries. I have seen people say run multiple chargers. I have also seen to not run 80% of your generators capabilities.

Is there a way to take at least a 1000w of my excess energy from my generators watts to charge my batteries?

Most choose an inverter/charger that conveniently uses the inverter's DC-AC circuitry in reverse to charge the battery when the inverter/charger is provided AC input. In your case, you need a AC to DC charger.

The IOTA linked above will give you about 1100W of peak charge power while running your generator at about 1300W (charging is only about 85% efficient).

I am not trying to dig my own hole but I do have land that is accessible by foot and as I said I have 10 400w bifacial hyperion solar panels. The land has about 2-4h more of sunlight down there. Would it be worth getting down there and setting all of the solar panels on a mppt that could handle it then converting it to the 24v I am trying to deal with now?

Yep. Just like @BatteryBuff said:

Yes, you could run those panels on two circuits, each using an 80A MPPT.

Alternatively, that 100/30 is right-sized for 2 of those panels, and 4 more of them might be cheaper than two more 80A controllers.
 
If you parallel panels, the Isc of the entire array can't exceed 35A. Guessing at their Isc to be around 14A, you'll only want 2P.
Yikes. I learn new stuff on this forum all the time. I was going to ask for a reference, but just pulled up the datasheet, and see that they basically say PV Isc can't be more than 5A over the output current, or "the controller may be damaged".

I was under the impression that significant over-dimensioning was fine, but fuses/OCP would be needed with > 2 parallel strings. Seems like others agree. I knew Voc should never, ever be breached, and had it my mind that max Isc was just a rule of thumb. Wonder how often they're actually damaged, in practice?

I know my rv runs about 400w to power on normal circumstances and I am running my 2500w generator I would like to make the most by charging the batteries.
What I am after is that I am willing to run my 2500w champion generator to cover but I am unsure how to get the excess power it is generating back into my batteries. I have seen people say run multiple chargers. I have also seen to not run 80% of your generators capabilities.

Is there a way to take at least a 1000w of my excess energy from my generators watts to charge my batteries?

Looks like others have covered the solar side. As far as charging from generator goes, I assume your RV already has a converter? You'll want to research the model and figure out what the charging stages are. I had an RV with a WFCO 8955 designed for lead acid, and used with 2x BattleBorn batteries in parallel. I had to "manually" get it to enter bulk mode by applying a large load to the battery, momentarily, and then it charged at its max output, 55A in my case. I only did that a few times, since we were almost exclusively boondocking, and solar on the roof kept the batteries happy.
 
Yikes. I learn new stuff on this forum all the time. I was going to ask for a reference, but just pulled up the datasheet, and see that they basically say PV Isc can't be more than 5A over the output current, or "the controller may be damaged".

I was under the impression that significant over-dimensioning was fine, but fuses/OCP would be needed with > 2 parallel strings. Seems like others agree. I knew Voc should never, ever be breached, and had it my mind that max Isc was just a rule of thumb. Wonder how often they're actually damaged, in practice?

Funny you should ask.

If you hook the array up backwards, the unit will protect itself by shorting the PV terminals. The contactor can handle 35A.

When pressed, the Victron folks will say there's no actual limit if you don't get the array wired backwards, but there is the practical absurdity. Put a 250/100 on a 12V system, and you're only going to get 1450W of charging out of a 9800W array (148Vmp/ 66.5A Imp)... kinda silly.

The exception is the RS450/X00. It's galvanically isolated, and the short circuit current limit is a "never exceed" value.
 
Funny you should ask.

If you hook the array up backwards, the unit will protect itself by shorting the PV terminals. The contactor can handle 35A.

When pressed, the Victron folks will say there's no actual limit if you don't get the array wired backwards, but there is the practical absurdity. Put a 250/100 on a 12V system, and you're only going to get 1450W of charging out of a 9800W array (148Vmp/ 66.5A Imp)... kinda silly.

The exception is the RS450/X00. It's galvanically isolated, and the short circuit current limit is a "never exceed" value.
Maybe an contrived example, but If you already have the panels and space, and only need the 1450 watts, but need it on cloudy and rainy days, too… 🤷‍♂️

Fascinating about the contractor—so to fry one of these guys, you have to not only hook it up backwards, but also exceed Isc while doing so. Takes some determination! 😁
 
So what should I do? Should I get a 6000xp and hook up 10 solar panels and run an extension cord 400' or should I stick with my 100v victron? With 2 panels?
 
And if I were to get a converter/battery charger what should I get?I think I am more heavily reverting to getting a charger for my 24v system that my generator runs. It is hard to get solid answers from this place.
 
To charge with a generator, the Iota dls-27-40 linked above is the simplest.

To charge with solar you should get a charge controller thats capable of 150v input. To use all 10 panels, as mentioned above, a pair of 80A controllers could do that. An outback flexmax 80 would be my choice.

A 6000xp is 48v. If going the AIO route, you will need a 24v, but again watch the mppt input voltage so you can get at least 2 panels in series without bumping into the max limit.

Im surprised your 100/30 still functions...
 
And if I were to get a converter/battery charger what should I get? I think I am more heavily reverting to getting a charger for my 24v system that my generator runs.
I suppose you'd want a lithium capable, 24V capable charger that outputs 45 amps. That's only about 1250W, but your batteries' recommended charge current is 46A. Your generator could probably supply enough power to charge it with up to 70A, but I'd stick to the manufacturer's recommendation.

It is hard to get solid answers from this place.
Well, you might want to bear in mind that nobody is getting paid to respond to your questions here. And that there are many different ways of doing things, and everybody has their own opinion. Trying to give advice without a clear picture of the situation makes it even more difficult.

You never did answer my question, maybe you didn't see it? Do you have a 24V RV, but no converter? The converter that you'd use to charge your RV batteries on shore power is the same unit you'd want to use to charge off a generator. But you might need to learn how to use it properly, in order to charge at an appropriate rate.

To charge with a generator, the Iota dls-27-40 linked above is the simplest.
That appears to be a 3 stage lead acid charger. Those are alright if they're supplementing a properly programmed charge controller that will occasionally take the batteries to a high enough voltage to allow for cell balancing. Which OP will need to keep an eye on...

So what should I do? Should I get a 6000xp and hook up 10 solar panels and run an extension cord 400' or should I stick with my 100v victron? With 2 panels?
If you went this route, you'd be able to charge with both solar and generator. And have AC power available, as a bonus. And you've already got the panels? The more solar you harvest, the less you need to run the genset. Seems like a no-brainer from where I'm sitting.
 
Victron Multiplus and be done with it. Scales down to 9.5A AC charging, up to 50A.

For a small 2500w generator, I wouldn’t push it over 1250w, but then again many don’t care about long life.
 
I routinely use the Iota chargers, mostly the 24 volt / 25 amp version, but also have a 75 amp x 12 volt and some 48 volt x I think 13 amp.
It does not have built in temperature compensation, so if you look at the charge profile in depth, what you will find is that it is close enough to what you need for LiFe.

Run the generator for an hour through the charger, then see if the sun can do the rest / enough for the day. If not, run it for 2 hours and try it that way. That is the the really big benefit of LiFe - in my mind, the major benefit. You can fill your battery "gas tank" partly full instead of completely full.

I use the 75 amp x 12 volt one to run power from my vehicle power system that I built ( has 120 vac out ) to jump start other vehicles, and sometimes mine. 10 - 15 minutes on that thing and it will power up most any 12 volt vehicle starter. The cord on it is a 20 amp plug, so it pulls some power - maybe more than a typical garage outlet has.
 

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