Monitoring while boon docking

[Bearcatrp]

Just tried out my solar system on my RV for the 1st time. Just a overnight At a friends house. I just monitor my battery charge plus how much charging is going on. Is this about the way to do this? Besides watching what you use, any other tips? Did find out a electric coffee pot is not a good idea. Will be looking for an old style that I can use on the stove. I watched the voltage drop while it was making coffee. Did tell the wife to use only one light as needed. Am impressed so far but now to try a weekend like this.

 

[JayArr]

Change all your lights to LED (Amazon) and then you can forget them as a drain, I used to turn off lights my wife left on to keep from draining the battery but with the LEDs she can leave them on all she wants and I don't worry. The LEDs become such an insignificant part of the equation they can be left out.

 

[UTTransplant]

Remember solar is just a method to charge the batteries. It won’t give you more power than the batteries provide. To increase power availability, add more or different types of batteries. When we got our last trailer, the first thing we did was swap out the single 12v for dual 6v golf cart batteries (220 amp hours). Gives more available amp hours in approximately the same space. When we ordered this motorhome, we had two extra 6v batteries added at the factory for a total of six (660 amp hours), but we have a residential refrigerator and needed a lot more power than before. Also remember that you shouldn’t go below 50% of the rated capacity of your batteries if you want long life from them.

 

[JayArr]

Also remember that you shouldn’t go below 50% of the rated capacity of your batteries if you want long life from them.

URBAN MYTH, it ignores the repetitive charging required to operate this way.

Here's an analogy:

Suppose you have a hot water heater that can provide you with 1000 tanks of water but it will wear out at 7 years no matter how much you use it.

If you shower every other day and have short navy showers that only use 50% of the tank you will reach 7 years but you will have only used 639 of the 1000 tankfuls available. It will fail having only used 64% of it's capacity.

If, however, you shower every other day and use the whole tank you will reach 1000 tankfuls at 5.5 years. You will have used the full capacity of the battery and it is discarded fully used.

The question becomes - "Which is the better value"? Would you rather have longer life and throw away capacity? Do you want the hassle of having to charge your batteries every time they get to 50% or would you rather run them down to 20% before recharging?

 

[Mark_K5LXP]

Any basic battery monitor (and many solar charge controllers) will report net battery capacity. Batteries don't create energy, they just store it. So bigger the battery bank, the bigger the charge source needs to be if that energy use is sustained. So even if you had a bank of lithiums large enough to run A/C for hours on end, at some point that energy would need to be replenished. The bigger the energy "bucket", the bigger the energy "pump" needs to be. So there's a sweet spot of capacity, charge source (solar, genset) and loads.

Mark B.
Albuquerque, NM

 

[Bearcatrp]

Most of my lights are LED on my new rig. Will check out the others. With 2 panels on my roof, seems to do a good job generating electricity. Just need a weekend boon docking for a good test of my system. Will bring my Honda 2200 just in case it’s needed. That’s for your replies.

 

[House Husband]

URBAN MYTH, it ignores the repetitive charging required to operate this way.

Here's an analogy:

Suppose you have a hot water heater that can provide you with 1000 tanks of water but it will wear out at 7 years no matter how much you use it.

If you shower every other day and have short navy showers that only use 50% of the tank you will reach 7 years but you will have only used 639 of the 1000 tankfuls available. It will fail having only used 64% of it's capacity.

If, however, you shower every other day and use the whole tank you will reach 1000 tankfuls at 5.5 years. You will have used the full capacity of the battery and it is discarded fully used.

The question becomes - "Which is the better value"? Would you rather have longer life and throw away capacity? Do you want the hassle of having to charge your batteries every time they get to 50% or would you rather run them down to 20% before recharging?

Oh Please! Take your nonsense some place else. There are senior members on here that have spent years off grid and know how to get the best VALUE from their batteries. We use the 50% rule. Battery life has nothing to do with water heater life.....Geeeeeeeesh.......

Richard

 

[Lou Schneider]

How are you monitoring your batteries state of charge? You need something that measures the cumulative amp-hours flowing in and out of the batteries. Watching the voltage or how much power a solar system is putting in without also subtracting the power your loads are using won't suffice.

There are several such battery monitors, ranging from $50 Chinese meters to Bluetooth monitors like the Victron Connect that display the parameters via Bluetooth on a Smartphone app. What they have in common is they use a current measuring shunt that's installed between the battery and all of the charging sources and loads on the batteries so they can track what's actually in the battery, not just what a solar system is pushing in it's direction.

Here are a couple of examples:

https://www.amazon.com/AiLi-Voltmeter-Ammeter-Voltage-Motorhome/dp/B07FGFFHC6

https://www.amazon.com/Victron-SmartShunt-500AMP-Bluetooth-Battery/dp/B0856PHNLX

 

[JayArr]

Oh Please! Take your nonsense some place else. There are senior members on here that have spent years off grid and know how to get the best VALUE from their batteries. We use the 50% rule. Battery life has nothing to do with water heater life.....Geeeeeeeesh.......

Richard

Well Richard

You don't have to like my analogy.

You are also welcome to continue to believe the 50% rule.

Telling me to leave because you don't like my post is a little much.

 

[Krazeehorse33]

I have the inexpensive smart shunt that Lou linked. It was an easy install and so far my limited experience with it has been good.

 

[John From Detroit]

URBAN MYTH, it ignores the repetitive charging required to operate this way.

No. it's no myth you do not understand that half a cycle is half a cycle But the chemistry of the battery... bad things happen if you discharge too far. But go ahead. Run your batteries down to next to nothing... Your wallet.

 

[Ex-Calif]

Well Richard

You don't have to like my analogy.

You are also welcome to continue to believe the 50% rule.

Telling me to leave because you don't like my post is a little much.

No. it's no myth you do not understand that half a cycle is half a cycle But the chemistry of the battery... bad things happen if you discharge too far. But go ahead. Run your batteries down to next to nothing... Your wallet.

I don't think Richard was actually saying leave the forum. More like take the comment from the forum. Still a bit harsh. There are believers in deep discharge damage and non-believers.

I like to think of myself as a hybrid. The best thing to make a battery last long is don't deep cycle it. The science is good on this.

However, if you do need to deep cycle when in the boonies go ahead - that's why you have batteries - they are consumables.

As a young guy in aviation mechanic school we had cut open batteries so we could see the effects of sulphidation and shorted cells. Battery fires are a big deal when you are at 10,000 feet so all the things that could make a battery dangerous were covered as part of the 12VDC curriculum.

Sulfidation is caused by under charging or overcharging. The chemical process to create 12V and extract power happens between the lead plates and the acid. The deeper you discharge the more the acid needs to eat into the plates. It does recover but it definitely does damage.

Note on the plate with desulphator in the 4th photo you can see the mesh structure the lead is built on but the deterioration is even and consistent.

I did off-shore boats for years. Cruising boaters are truly off-grid and the ones who take it seriously can get 8-10 years from a set of 8 Trojans. Others burn them up in 4.

Hey it's the internet - believe your own truths but pretty much there can only be one science to this.

 

[Mark_K5LXP]

...go ahead. Run your batteries down to next to nothing... Your wallet.

Those of us that haven't bought into the myth aren't advocating running batteries dead. The data I present is operating batteries per manufacturer data sheets and they're not in the business of myth. A few decades and many hundreds if not thousands of batteries under my own belt, it turns out they're right. If there's data to the contrary for batteries in RV service, it sure isn't well publicized.

Mark B.
Albuquerque, NM

 

[Gary RV_Wizard]

If you measure "battery life" by calendar time between replacement, there can be little doubt that minimizing depth of discharge yields a longer calendar life in the RV. Counting discharge/charge cycles (full or partial) likely yields a different measure of useful life, but most RV owners don't do that, or even have the capability of doing that.

 

[UTTransplant]

As someone trained as a chemist, I think more like ex-Calif. There is true damage to the plates by multiple deep discharges. And, as Gary says, I also think in terms of years, not discharge. Doesn’t mean Mark and a I can’t both be right; we just emphasize different sides of the battery question.

 

[Ex-Calif]

As someone trained as a chemist, I think more like ex-Calif. There is true damage to the plates by multiple deep discharges. And, as Gary says, I also think in terms of years, not discharge. Doesn’t mean Mark and a I can’t both be right; we just emphasize different sides of the battery question.

I agree and it becomes a monetary discussion. I, like almost everyone, get paid according to calendar days not battery cycles. The cost of batteries is fixed, my income is fixed so the variable is rate of cycle consumption.

Even if no increase in plate deterioration occurs when deep cycled (but it does) it is still advantageous to consume battery cycles more slowly. So 1,000 deep cycles, 2,000 "50%" cycles or 4,000 "25%" cycles. If you have one cycle a day that's a range of 3 years to over 10 years. Of course the numbers are hypothetical but illustrative.

If you can keep the batteries well charged it makes a lot of sense economically to do so.

A T-105 225a/h battery is about $250 including tax. So $1,000 bill for 4 of them.

$1 per cycle or $0.25 per quarter cycle. Easy choice to make when looking at a calendar. Solar power is basically free after the investment and even so amortizes over a much longer period.

 

[Mark_K5LXP]

Not everyone wants to study batteries to go camping and get this fear planted in their minds with the 50% Rule that make one mistake and it's OVER. OMG, I'm at 50% shut everything off! Fire up the genset! Crap, my batteries are dead, it must've been that ONE TIME I left the fan on and I went below 50%. Oh, the humanity! It's a religion to some, the 50% point is the "usable" number of Ah. If you go below 50% you'll *kill* your battery, cause *severe damage*, and the like. This is completely false and has no technical basis. Some True Believers offer that for "optimum" life this is the target but can't describe what "optimum" means in any practical sense or what the tradeoffs are. Where the myth falls apart is operating the battery such that cycle life will extend beyond calendar life, guaranteeing lost service life, increased cost and decreased utility. Does it make sense to (obsessively) operate a battery so it gets 1500 cycles when you only use a hundred a year? By year 5 or 6 that battery is crapping out and you've left 1000 cycles, a good 2/3's of it's life on the table. The "typical" RV use profile is something like 30 days a year. That's nominally 150 cycles of operation over the battery calendar life which makes DOD an *irrelevant* factor of performance or longevity. Whether someone wants to draw an arbitrary DOD line in the sand as a matter of simplicity or operating margin that's fine, whatever works for them. If at the end of the day you get to run your stuff when you want and you're not unhappy with whatever service life you get then mission accomplished. If as much emphasis were placed on proper charging and maintenance as the 50% Rule there would be a whole lot more batteries out there that lived a long and productive life, irrespective of DOD.

Mark B.
Albuquerque, NM

 

[John From Detroit]

Those of us that haven't bought into the myth aren't advocating running batteries dead. The data I present is operating batteries per manufacturer data sheets and they're not in the business of myth. A few decades and many hundreds if not thousands of batteries under my own belt, it turns out they're right. If there's data to the contrary for batteries in RV service, it sure isn't well publicized.

Mark B.
Albuquerque, NM

You may have nailed the issue.
Lead Acid storage battery types form a matrix (Like a checkerboard or tic-tac-toe board)
One column the 3 types are "Starting, MARINE/deep cycle, DEEP CYCLE (Golf car is an example)
And across the top you have things like Flooded wet, Maintenance free, AGM GEL other (We will ignore that spread)

Take a starting battery down to half full.. Time to replace as a general rule (Done it twice)
Oh they may recover for a brief time but you really should replace.

A Golf car battery has no issues with half full.

 

[Bearcatrp]

How are you monitoring your batteries state of charge? You need something that measures the cumulative amp-hours flowing in and out of the batteries. Watching the voltage or how much power a solar system is putting without also subtracting the power your loads are using won't suffice.

There are several such battery monitors, ranging from $50 Chinese meters to Bluetooth monitors like the Victron Connect that display the parameters via Bluetooth on a Smartphone app. What they have in common is they use a current measuring shunt that's installed between the battery and all of the charging sources and loads on the batteries so they can track what's actually in the battery, not just what a solar system is pushing in it's direction.

Here are a couple of examples:

https://www.amazon.com/AiLi-Voltmeter-Ammeter-Voltage-Motorhome/dp/B07FGFFHC6

https://www.amazon.com/Victron-SmartShunt-500AMP-Bluetooth-Battery/dp/B0856PHNLX

My RV came with a vicron 30a unit. I put the app on my iPhone which has good information on current day and past days. Good information posted here so thanks again.

 

[Ex-Calif]

Does it make sense to (obsessively) operate a battery so it gets 1500 cycles when you only use a hundred a year? By year 5 or 6 that battery is crapping out and you've left 1000 cycles, a good 2/3's of it's life on the table. The "typical" RV use profile is something like 30 days a year. That's nominally 150 cycles of operation over the battery calendar life which makes DOD an *irrelevant* factor of performance or longevity. Whether someone wants to draw an arbitrary DOD line in the sand as a matter of simplicity or operating margin that's fine, whatever works for them. If at the end of the day you get to run your stuff when you want and you're not unhappy with whatever service life you get then mission accomplished. If as much emphasis were placed on proper charging and maintenance as the 50% Rule there would be a whole lot more batteries out there that lived a long and productive life, irrespective of DOD.

Mark B.
Albuquerque, NM

Mark - agree with your passion and the warnings that the occasional full discharge is not a show stopper but the bolded sentence above doesn't make sense to me.

The sticker on the battery is irrelevant to battery life. Manufacturers put a sticker on based on predicted usage. You've also done that with the statement that the average RV does 100 cycles a year. That's not true for liveaboards who arguably are in a continuous cycle of consumption and discharge.

You close with a statement about proper charging which is the key to battery life in cycles or in calendar days. I totally agree with that.

So if a battery is stickered for 5 years you can definitely get 8-10 years with proper servicing and care. Batteries are not like tires where you have to throw them away based on a date.

So yes it does matter how many calendar days a battery lasts and it is easy to take care of the battery bank with proper charging systems.

You might be trying to make a differentiation between obsessive and careful. I agree you don't have to be obsessive about it but the alternate extreme of running to 10V every time before charging is definitely not a good plan for the pocket book.