diy solar

diy solar

Not sure what to go with

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Partsjockey

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I have 2 12v agm 290ah batteries in series for 24v. I want to but 2 275ah pre made batteries to replace the agm's will this be enough.
 
What kind of batteries are the new 275Ah batteries?

Only you can possibly know if a 24V 275Ah battery bank is enough for your needs since you haven't told us how much power you use.

But, if your new batteries are LiFePO₄ then they will actually have more usable capacity than your current AGM batteries.
 
The Batteries are Eve 280. The RV is new to me, so that is what is in there at the moment. the rv was owned by older fellow,I'm assuming the batteries have been changed with the same or close to the same capacity as were in before.
 
Compare surge current of your load with spec on the batteries, make sure they can supply it. The cells surely can, but BMS maybe not.
Use a precharge resistor before connecting, so no surge charging capacitors in inverter.
Lithium appears better in many aspects, but BMS can hobble it.
Lithium can't tolerate charging in freezing conditions, so see if its BMS provides protection.
 
But what kind of batteries are the new 275Ah batteries? AGM? Lead acid? LiFePO₄? Something else (what specifically)?

And again, how can we know if they are enough? You haven't told us any information about your power needs.
 
"Eve 280" would seem to be the cells everybody was building DIY with.
"275ah pre made batteries" is the mystery.

If the 290Ah AGM were sufficient for the RV of course these should be even better.
But RV power usage depends on the user, and where it is taken. Hours of A/C would obviously run it down.
The other piece missing is generator or PV. Charger needs to be compatible with lithium, but enough PV could keep it running indefinitely.

Need complete description of system, power audit listing appliance consumption, estimate of operating hour for discretionary loads.
 
Sorry folks. So the way the system is setup, when traveling alternator off of engine that is dedicated for house batteries charges them. When stopped either generator 17 kwh or shore power tells invertor to charge. List of appliances consumption do not know. I know this,it has microwave, electric stovetop that we really don't use, washer w/ventless dryer combo (go figure), electric heated floors, hot water tank. Hope this helps you help me LOL.
 
Microwave is a reasonable load for battery/inverter. Actual power draw is not same as rated cooking power watts, could be 1500W actual draw, so battery and inverter need to support that.

Electric stovetop is probably OK unless run for such a long time that it exceeds stored power.
Electric floor heating, what wattage rating? Space heating will run the battery down because it is a large continuous draw.

Washer dryer should be fine, but only for a limited time. "Ventless" is typically lower power than conventional. Some use refrigeration to condense, some use water (more common in single washer/dryer unit, hope it doesn't waste too much from your fresh water tank!). Some use fan and room air to condense, so wasting heat and heating the room. Dryer will be a significant power consumer.

Water heater also consumes significant power, but could be reasonable peak wattage.

Many RV appliances are reasonable only on shore power.
Multiple heating loads at once could exceed inverter capacity, and maximum battery current draw.

Only your personal usage will determine whether battery capacity is enough.
If you put PV panels on the roof, and enable water heater and dryer when sun is shining, might work out well.
Space heating like heated floor won't be practical from battery, could be OK while excess power from PV.

You need ratings of batteries, inverter, appliances to better analyze how much can be powered.
 
Hedges said:
Microwave is a reasonable load for battery/inverter. Actual power draw is not same as rated cooking power watts, could be 1500W actual draw, so battery and inverter need to support that.

Electric stovetop is probably OK unless run for such a long time that it exceeds stored power.
Electric floor heating, what wattage rating? Space heating will run the battery down because it is a large continuous draw.

Washer dryer should be fine, but only for a limited time. "Ventless" is typically lower power than conventional. Some use refrigeration to condense, some use water (more common in single washer/dryer unit, hope it doesn't waste too much from your fresh water tank!). Some use fan and room air to condense, so wasting heat and heating the room. Dryer will be a significant power consumer.

Water heater also consumes significant power, but could be reasonable peak wattage.

Many RV appliances are reasonable only on shore power.
Multiple heating loads at once could exceed inverter capacity, and maximum battery current draw.

Only your personal usage will determine whether battery capacity is enough.
If you put PV panels on the roof, and enable water heater and dryer when sun is shining, might work out well.
Space heating like heated floor won't be practical from battery, could be OK while excess power from PV.

You need ratings of batteries, inverter, appliances to better analyze how much can be powered.
Click to expand...
Thanks for the answer. I believe when they built this RV that was taken into account. This old girl is 22 yrs old. So I think I should be good for battery size. They are 4 EVE 280 ah batteries with it's own bms in a case etc etc. I guess I was questioning my decision because the batteries were not the same physical size as what I have at the moment. Now just need to get dc to dc charger for the alternator & adjust inverter.
 
But we have no idea what BMS and build of battery. Many companies offer a product built around LiFePO4 cells. Some, people replaced BMS to get a usable battery. Sometimes internal built is robust, sometimes not. Cases, cells, BMS are all available from Ali Baba and the 40 thieves, so anyone can assemble and sell a product. Or DIY. Cell quality is a big deal so DIY people here have settled on middleman vendors they trust.

How about a link to these batteries?
 
This one?

Twin Pack 2x SFK-260 7.2KW Ships from USA in 1-2 Days. Sun Fun Kits SFK-275HP High Power 12v 275AH Lithium Iron Phosphate Battery for RV/Recreation/Back Up Power - Sunfunkits.com

Twin Pack 2x SFK-260 7.2KW Ships from USA in 1-2 Days. Sun Fun Kits SFK-275HP High Power 12v 275AH Lithium Iron Phosphate Battery for RV/Recreation/Back Up Power - Sunfunkits.com
www.sunfunkits.com

I'm headed to work, but people could dig through, see how its specs look.

How about inverter specs?

As I mentioned before, suggest a "precharge resistor" prior to connecting lithium batteries to inverter, due to inrush current charging capacitors.
 
Yes that one, inverter is Trace SW4024, I don't know about the precharge resistor or even how to achieve it.
 
Partsjockey said:
Yes that one, inverter is Trace SW4024, I don't know about the precharge resistor or even how to achieve it.
Click to expand...

Simple. When an immovable object meets an irresistible force, things between them get bent out of shape.

Lithium cells have about 0.00017 ohms internal resistance and 3.4V. Whatever voltage battery you may assemble with cells in series, 3.4V / 0.00017 ohms = 20,000A

Capacitor bank on battery side of inverter is approximately zero ohms impedance. When battery is connected, initially 20,000 amps flow, tapering off in a fraction of a second. But in the mean time, any fuse in the circuit blows, even a $50 400A class-T fuse. Lithium battery BMS shuts off or blows. Contacts weld.

Assuming the inverter doesn't immediately start drawing current, completing the circuit with any resistor or light bulb will reduce current to a trickle and gently charge the capacitors. A pushbutton and light bulb (rated for battery voltage) bypassing a battery switch is one approach. Hold button until light fades out, then close switch. If inverter does turn on automatically after a delay, size resistor to get full voltage before that delay elapses, and close switch before then.

Search the forum for threads on the topic.
Some batteries have a built-in precharge circuit, which is great if it works for you. If not, you're stuck. There are threads on that as well.
 
Hedges said:
Microwave is a reasonable load for battery/inverter. Actual power draw is not same as rated cooking power watts, could be 1500W actual draw, so battery and inverter need to support that.

Electric stovetop is probably OK unless run for such a long time that it exceeds stored power.
Electric floor heating, what wattage rating? Space heating will run the battery down because it is a large continuous draw.

Washer dryer should be fine, but only for a limited time. "Ventless" is typically lower power than conventional. Some use refrigeration to condense, some use water (more common in single washer/dryer unit, hope it doesn't waste too much from your fresh water tank!). Some use fan and room air to condense, so wasting heat and heating the room. Dryer will be a significant power consumer.

Water heater also consumes significant power, but could be reasonable peak wattage.

Many RV appliances are reasonable only on shore power.
Multiple heating loads at once could exceed inverter capacity, and maximum battery current draw.

Only your personal usage will determine whether battery capacity is enough.
If you put PV panels on the roof, and enable water heater and dryer when sun is shining, might work out well.
Space heating like heated floor won't be practical from battery, could be OK while excess power from PV.

You need ratings of batteries, inverter, appliances to better analyze how much can be powered.
Click to expand...
here is a decent chart of typical household item loads...
 

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