Solar Experts-Does this sound right to you?

[Elkman]

With lithium house batteries the optimum installation includes a BIM that will direct power to the starter or chassis batteries after the lithium house batteries are fully charged. With solar the house batteries can be recharged without needing to fire up a generator or run the engine. It depends a great deal on the fridge. Our last RV had a fridge that ran on electricity or propane and we could go a month on 4 lbs of propane which also was used for the cooktop and the furnace.

If the charge controller for the solar is rated at 450 Watts then stick with 400 Watts of solar panels for now. The fridge alone will use all the power from 1-2 panels depending on its draw and how full you keep the fridge. With our propane fridge 200W from the solar was more than enough but with our new RV with its electric only fridge we are going with 400W of solar.

The Onan generators are noisy and with our last RV we did not use one and the space for one was used for additional storage. What I have noticed is that the generator bays are not lined with any sound absorbing material and so only the small amount inside the generator housing is used. This is a $25 fix with the addition of sound dampening panels to the generator compartment.

I am replacing the two 100 AH AGM batteries with two lithium 125 AH batteries. The AGM should not be discharged below 50% SOC and even then they are good for 300-500 recharge cycles. With the lithium batteries they can go for more than 2,000 discharge and recharge cycles and be discharged to 20%. The two lithium batteris provide up to 3200 Watt hours for the RV.

So the AGM batteries provide 100 amp hours of power as compared to 200 amp hours with the lithium batteries. The lithium can be recharged at a much faster rate as well and so in theory should charge faster from the chassis alternator than a set of AGM batteries.

A key drawback to most lithium batteries is that the temperature needs to be above 32 degrees Ffor them to charge. There are battery compartment warmers of the Relion low temperature batteries that can be charged at temperatures as low as -4 degrees F.

[al1florida]

Originally Posted by Elkman

..................A key drawback to most lithium batteries is that the temperature needs to be above 32 degrees Ffor them to charge. There are battery compartment warmers of the Relion low temperature batteries that can be charged at temperatures as low as -4 degrees F.

Just to note that the 32* temp is the internal battery temp and not the outside air temp. If the batteries are in an enclosure (storage compartment) the outside temp can go down quite a ways below freezing before the battery internal temp gets to below 32*. Additionally there is some heat generated when discharging the battery and heat generated when charging so that helps keep the batteries above freezing. I think Battle Born has a cutoff of about 25* so you can be in even colder weather.

I installed my lithium batteries in the living area (the bedroom) and I am not about to live in my RV with the inside temp below freezing.

It is also good to note that with lead acid batteries they loose capacity as they get cold. Quite a bit of capacity when they get down into the teens or lower.

I wonder just how many RV'ers spend extended time in temps below 25* for it to be a big concern about charging at below 32* battery internal temp.

[AJMike]

Originally Posted by al1florida

I wonder just how many RV'ers spend extended time in temps below 25* for it to be a big concern about charging at below 32* battery internal temp.

I knew about this issue before I bought Lithium batteries for our RV, but living in southern Arizona this did not seem like a big issue for us. And since I don't want to have to worry about driving our Winnie Fuse in snow or ice I have no plans to go anywhere near truly freezing temperatures. We have camped where it is in the 30s at night, but would not plan to camp where it is in the 20s at night.