House, batteries

[Joec]

I m kind of new to the class A RV ing. We recently bought a 2021 Thor windsport 34 R and it has a solar panel on it. The RV is in my pole barn It has skylights in it and the top center panel is clear so when it’s light outside, it’s really light in the pole . I’m hoping that’s enough for the solar panel to keep my batteries charged. The guy I bought it off of told me that the batteries or six months old and I just wanna make sure they are OK. What is the battery voltage supposed to be? I also start my RV and let it run about 30 minutes a week to keep my batteries charged. I appreciate.your input on what I should do to keep my batteries in good shape.
Thanks again Joe C

 

[16ACE27]

If you want to really know the status of your batteries and whether solar is keeping up, get a good shunt based battery monitor the will keep track of the actual battery capacity status... I use this one from Renogy currently at $80:

https://www.amazon.com/dp/B07RP5B5P7?th=1

Others may recommend some unknown brands that may work just as good at half the price similar to this Qwork model:

Amazon.com

 

[DavidEM]

Batteries are 100% charged when the voltage is at 12.6V or greater with no charging source or load on.

That panel is probably 100 watts which will probably only produce 15-20 amp hours during full sun this time of year. You are in SC right?

Under a skylight inside you will only make a fraction of that. Plus if you have any significant parasitic load with all users off (and all RVs have some sort of parasitic load) that is likely to be more than the panel can put out underneath the skylight.

Running the chassis engine will only charge the coach batteries if they are at or below 12.5 V assuming you have the Precision Circuits BIM 160.

Running the generator will charge the coach batteries much faster through the converter/charger. But whether you run the chassis engine or the generator be aware of CO poisoning unless the pole barn is wide open on the sides.

David

 

[Chateau_Nomad]

For house batteries I highly recommend eventually switching to LiFePO4 batteries. The price has fallen like a rock, and the energy density is nearly double and weight 1/2 of lead acid. They also don't self-discharge like lead-acid batteries, so in winter if you charge them up to, say 80%, they'll stay at nearly 80% for several months... where a lead-acid battery would be dead.

With your pole barn setup with lithium batteries you'd just need to get the batteries initially charged for storage. It's likely your solar panel would provide enough trickle charge to keep the lithium batteries topped up... likely NOT the case with lead-acid.

The other issue is keeping your chassis battery charged. The solar may not be sufficient for that if covered, so your current method of weekly running the engine would probably need to continue. In Ohio, once a month I exercise my engine for 30 - 40 minutes, and the generator (under load) for at least an hour. Combined with that and the solar, my house lithium batteries and lead-acid chassis battery stay at or near 100%.

The recommendation by ACE for a shunt is a great idea to read battery "state of charge" in percent capacity. I use the cheaper QWORK brand and has worked great. Also note that many newer lithium batteries have Bluetooth so you can read state of charge from a phone app.

 

[Selmahotrod]

Can I replace wet cell batteries with lithium and not have to do any kind of modifications?

 

[PS89]

Can you? Sure!

Should you? That's a different question...

 

[Chateau_Nomad]

Can I replace wet cell batteries with lithium and not have to do any kind of modifications?

It's a simple matter of doing your own research... because everyone's situation is different. Some can... some shouldn't. And some WILL even though they shouldn't!

 

[DavidEM]

A lead acid battery charger will only charge a Lithium battery to about 80% because its voltage cuts off too soon.

But other than loss of capacity, there isn’t any thing wrong with that.

David

 

[dkoldman]

Can I replace wet cell batteries with lithium and not have to do any kind of modifications?

It really depends on your objectives, and your current specifications like normal draw, alternator size etc. But no you don't have too, but generally is one is looking to switch they are tryong to gain something that only Lithium to provide. Otherwise why change.

Also Modifications is too vague. 4 years ago when I was seeking Lithium the so called modifications cost was about $3,800. That did not meet my objectives so I paid $500 for AGM and move on.

About 6 months ago, I was able to double the AGM capacity with a single Lithium battery for $400. I could have put it in and called it day, but the so called modifications I had learned more about as stated by the Chateau above. I learned that I could do all of these modifications myself and I spent under $500 of parts and I bought top line stuff like Victron. I have Victron DC2DC charger, new Progressive Charger that has profile for all possible battery types, a Victron Shunt, and now disabled Trombetta from alternator when engine running. I met my objective which was to get new batteries, maximize capacity & space, the ability to monitor all of my current battery conditions with Victron Connect app and remove any potential for any alternator damage given that yours truly was doing the work.

 

[16ACE27]

Can I replace wet cell batteries with lithium and not have to do any kind of modifications?

Yes, but you may want to at some point to get the most out of the lithium batteries and help the longevity of the alternator.

 

[Mark54]

A lead acid battery charger will only charge a Lithium battery to about 80% because its voltage cuts off too soon.

But other than loss of capacity, there isn’t any thing wrong with that.

David

Interesting idea- best lifespan for LFP batteries is keeping them between 20-80% SOC. Almost doubles their lifespan. (5000 vs 3000 cycles typically) So if you just swap out your wet cells, you'll do better b/c wet-cell batteries typically last 500 cycles, and only can use 50% of the stated amps/watts.
LFPs can cycle up to 8000 cycles, esp if maintained at 20-80% and can use all the watts in between.
Add to all that, they are getting less expensive. If you look at cycles and cost, I'd say LFPs are way ahead. Drawback is that they don't 'like' to charge below freezing, and need to be maintained off season at 50-60% SOC, and cycled every 3 months to 100%, and drop back to 50-60%- which is what I do during storage months in VT.
So in light of that- I'd say find at a good price and rating- and go for it. I use Weize batteries and so far after 2 years, are great.
As long as you do not change your watt usage, you should be able to keep the same wire guage. If you plan to use more watts, check an ampacity chart to see what wire gauge you need.

 

[16ACE27]

A lead acid battery charger will only charge a Lithium battery to about 80% because its voltage cuts off too soon.

But other than loss of capacity, there isn’t any thing wrong with that.

David

For those wondering if their OG converter can charge LiFePO4 batteries, the answer is: yes. Absorption mode will fully charge them and then when it kicks into LA float mode they will slowly discharge (if there is a load on the system) to about 65%. Here's a pic of my converter finishing off my 500 AH bank.View attachment 555622

In my actual experience a Lead-Acid converter will charge LFP batteries to 100 % SOC, BUT; when the converter switches to float mode the LFP batteries will carry the load, draining them to between 60 to 70% SOC and maintain them there. Unfortunately, there is no way to force the converter back to bulk or absorption mode to get the batteries back to 100% SOC when needed so I use an external 50 amp Lithium charger for that.

 

[Chateau_Nomad]

Mark - Something to consider...

By keeping your SOC between 20% & 80% you're essentially forfeiting 40% of the useful capacity. So, other than lifespan, you're mimicking a lead-acid battery usage profile.

I switched to LiFePO4 for two basic reasons... First and foremost is the ability to get the FULL rated capacity without significant degradation. Second was the lifespan over lead-acid.

I did "napkin math" counting average cycles of my LiFePO4 batteries (which is recorded by the battery's BMS). Cycling from 100% to 0% (actually controlled by the BMS cutoff), I should EASILY get OVER 10 years usage. Cycling the batteries once EVERY SINGLE DAY (who DOES that??) would still yield 3,650 cycles - or 10 years.

It's akin to the Social Security quandary - draw less each month over a longer period, or draw more each month over a (likely) shorter period. We'll it's actually the inverse, but the same mental gymnastics.

My batteries stay in the motorhome... no removing for the Ohio Winter. I simply let the battery's BMS do it's job of controlling SOC and balancing cells. The rooftop solar provides ample power... the BMS knows what to do. No muss, no fuss. It just works.

Here's a Will Prowse video which EVERYONE buying LiFePO4 batteries should watch. It debunks a lot of myths.

 

[Mark54]

Mark - Something to consider...

By keeping your SOC between 20% & 80% you're essentially forfeiting 40% of the useful capacity. So, other than lifespan, you're mimicking a lead-acid battery usage profile.

I switched to LiFePO4 for two basic reasons... First and foremost is the ability to get the FULL rated capacity without significant degradation. Second was the lifespan over lead-acid.

I did "napkin math" counting average cycles of my LiFePO4 batteries (which is recorded by the battery's BMS). Cycling from 100% to 0% (actually controlled by the BMS cutoff), I should EASILY get OVER 10 years usage. Cycling the batteries once EVERY SINGLE DAY (who DOES that??) would still yield 3,650 cycles - or 10 years.

It's akin to the Social Security quandary - draw less each month over a longer period, or draw more each month over a (likely) shorter period. We'll it's actually the inverse, but the same mental gymnastics.

My batteries stay in the motorhome... no removing for the Ohio Winter. I simply let the battery's BMS do it's job of controlling SOC and balancing cells. The rooftop solar provides ample power... the BMS knows what to do. No muss, no fuss. It just works.

Here's a Will Prowse video which EVERYONE buying LiFePO4 batteries should watch. It debunks a lot of myths.

Point taken- and especially thanks for that video!! I went with LFP for the same reasons.
Will Prowse is my hero as well- he's why I went with Weize batteries. I have BMS in mine, and works great, esp for temperature.
I do all he says for storage- keep at 50% and cycle up to 100% every few months. it gets too cold here in VT to have them out in the RV- I do not have indoor heated storage and he says to not keep them too hot or too cold. It's too cold here... can be -20 to -30°F at times.
I was glad to hear that these will probably last longer than me!
Now- for the guy who wants to just use them in place of wet-cells, you are correct. I was just trying to say to OP that he can do it, but will be limited as well, but wet-cells hate to go below 50% so not really mimicking that chemistry when using LFP at 20-80%. If you run a wet-cell to 20% more than just a few times, lifespan will be shorter.
My EV is happiest at 20-80, but it's Li-ion instead of LFP.

 

[Chateau_Nomad]

Point taken- and especially thanks for that video!! I went with LFP for the same reasons.
Will Prowse is my hero as well- he's why I went with Weize batteries. I have BMS in mine, and works great, esp for temperature.
I do all he says for storage- keep at 50% and cycle up to 100% every few months. it gets too cold here in VT to have them out in the RV- I do not have indoor heated storage and he says to not keep them too hot or too cold. It's too cold here... can be -20 to -30°F at times.
I was glad to hear that these will probably last longer than me!
Now- for the guy who wants to just use them in place of wet-cells, you are correct. I was just trying to say to OP that he can do it, but will be limited as well, but wet-cells hate to go below 50% so not really mimicking that chemistry when using LFP at 20-80%. If you run a wet-cell to 20% more than just a few times, lifespan will be shorter.
My EV is happiest at 20-80, but it's Li-ion instead of LFP.

In your case with those winter storage temps it's probably better that you do remove the batteries and treat as "long term storage"... maintain 50% SOC. We occasionally get single digits, but usually doesn't last... hovering maybe a little below freezing, then slightly above... typical Ohio. So not worth the hassle to remove, which for me would take at least a couple hours of disassembly.

Off topic, but we do use a modified winter charge routine for the EV (Chevy Bolt) keeping charge between 80% - 85%. In really cold temps it must have a BMS setting preventing 100% charge... annoying sometimes. P.S. I always joke with the wife when gasoline prices go on a rollercoaster. Our "electrons" still cost 15¢ per kilowatt... can you image if electric prices changed like fuel??

 

[Selmahotrod]

Thanks for all the replies!

 

[Mark54]

In your case with those winter storage temps it's probably better that you do remove the batteries and treat as "long term storage"... maintain 50% SOC. We occasionally get single digits, but usually doesn't last... hovering maybe a little below freezing, then slightly above... typical Ohio. So not worth the hassle to remove, which for me would take at least a couple hours of disassembly.

Off topic, but we do use a modified winter charge routine for the EV (Chevy Bolt) keeping charge between 80% - 85%. In really cold temps it must have a BMS setting preventing 100% charge... annoying sometimes. P.S. I always joke with the wife when gasoline prices go on a rollercoaster. Our "electrons" still cost 15¢ per kilowatt... can you image if electric prices changed like fuel??

That's why I moved and upgraded LFP batteries inside the coach- easy to remove and maintain. They are heavy, but imagine trying to remove from bottom of coach!!!
So much easier now.
I had a Bolt EV and now have an ID4. e-Golf was my first. Using 80% top end is also referred to as "Hilltop reserve" so regen braking can be used on the way out.

 

[Beau388]

I had a chance recently to check the low temperature capability batteries of my BMS. The golf cart has 4 120AH 12 volt LFP batteries - (three in series and one parallel). Last week, we had a 28 degree morning. I hopped into the golf cart to go to breakfast. It ran just like normal. When I got back home, the temp was 31, so I thought I would give the charger a try. The coulombmeter was showing a 60% charge reaming.. When I turned the charger on, it went to 41.6 volts at 13.5 amps After two hours, the charger showed that 25 AH had been added to the batteries. That was enough to show as long as it is above -4 F, you are good to go with most LFP batteries. Yes, it is a 36 volt 2004 EZ-GO TXT.