Critique proposed solar battery upgrade

[phemens]

Currently have a Jayco hybrid (Jayfeather 26L) but moving to a Denali 5th wheel in the spring (2012 DE324LBS).
Currently have 4 Trojan T125’s with 600 watts of solar, with a Kisae 2000 watt pure sine inverter, we primarily dry camp.
Plan for ‘new’ trailer is to upgrade batteries and solar. Batteries are 5yrs old, serviceable but nearing end of life. Would like to go with 1000 watts solar, and possibly 6 x Crown 6CRV 220 AH AGM batteries. I’ve heard that AGM handle heavy loads better than FLAs. Typical use of inverter now is coffee maker morning and evening, plus TV and occasional limited use of microwave. My end goal is to have enough capacity to run the inverter pretty much any time (i.e. not switch on/off all and ideally run the fridge on 120 during the day to reduce LP use and leverage excess solar during the day.
Inverter is wired to batteries with 4/0, plan for solar is either a single 60A converter with 24v panels or 2x 30 (already have them, but willing to upgrade that too, one is MPPT, the other isn’t.
Got time to plan, so thoughts?

[MrWizard]

Well i disagree
You install your amp meter and a charge at spec voltage
The charger/converter is also supplying the house loads
So the meter is reading the true acceptance of the battery bank
The battery bank is not being used, except when your house appliance load exceeds the charger capability aka big inverter running MW etc..
So when they reach spec amps acceptance, they are full
Do you do a hydrometer check on the flooded batteries everyday while camping and charging?
You are implying that you do, if you do not, what is the difference
You can't tell if your fla are fully charged unless you do a specific gravity check with the hydrometer

What I don't like at all is not being able to tell when they are truly full after a recharge except at home after a camping session. You need to observe their amps acceptance when they reach spec voltage, but you can't do that while camping because they always have a draw on them from the RV

[brulaz]

BFL13 wrote:
People seem to like their AGMs but I am not a big fan. There are two in the truck camper because Flooded batts cause fumes inside where the batts go. No choice except AGMs there.

They do well for having little voltage sag under high inverter loads. What I don't like at all is not being able to tell when they are truly full after a recharge except at home after a camping session. You need to observe their amps acceptance when they reach spec voltage, but you can't do that while camping because they always have a draw on them from the RV.

With Flooded you can tell by using an hydrometer. This only matters if you spend a long time off grid without getting shore power so you can operate the RV on converter with the batts disconnected. Now you can do the amps observation on the AGMs to make sure they are truly full and won't get sulfated to death so soon.

For long periods on solar only, where you often go long periods on incompletely charged batts, IMO AGMs are worse than Flooded for being able to keep them from sulfating, because with the Floodeds you can tell what state they are getting in.

BTW, I have tested my AGMs for voltage sag against Trojan 1275s (both deep cycle 12v) and found the AGMs did slightly better per AH of capacity, but not enough to matter.

IMO, T-1275s are the way to go for most RV situations, but you can also get by with all sorts of other set-ups, AGM or not.

I gotta agree with BFL here. But AGMs sure are nice if you want something inside and kept warm.

To compensate for the sulfating issue I'd go down to Boston and load up on Outback Nanocarbon AGMs at the AltE store:
https://www.altestore.com/store/deep-cycle-batteries/sealed-agm-batteries/outback-power-energycell-1...

[BFL13]

People seem to like their AGMs but I am not a big fan. There are two in the truck camper because Flooded batts cause fumes inside where the batts go. No choice except AGMs there.

They do well for having little voltage sag under high inverter loads. What I don't like at all is not being able to tell when they are truly full after a recharge except at home after a camping session. You need to observe their amps acceptance when they reach spec voltage, but you can't do that while camping because they always have a draw on them from the RV.

With Flooded you can tell by using an hydrometer. This only matters if you spend a long time off grid without getting shore power so you can operate the RV on converter with the batts disconnected. Now you can do the amps observation on the AGMs to make sure they are truly full and won't get sulfated to death so soon.

For long periods on solar only, where you often go long periods on incompletely charged batts, IMO AGMs are worse than Flooded for being able to keep them from sulfating, because with the Floodeds you can tell what state they are getting in.

BTW, I have tested my AGMs for voltage sag against Trojan 1275s (both deep cycle 12v) and found the AGMs did slightly better per AH of capacity, but not enough to matter.

IMO, T-1275s are the way to go for most RV situations, but you can also get by with all sorts of other set-ups, AGM or not.

[pianotuna]

phemens,

I purchased used telecom AGM's at the interstate store in Saskatoon. 556 amp-hours cost me under $500 (4 12 volt batteries)

If you plan on using a medium to large inverter (1000 watts and up) there is an advantage to using twelve volt jars. They must be wired in a balanced manner.

[phemens]

so I think I will be going with AGM based on feedback here (can't justify Lithium at this point and I do cold weather camping). Would I be better with 12v or 6v batteries based on my usage pattern, and what is the recommended brand. I'm thinking that I will stick with either 6 6v batteries @ ~ 200 A/H each for total usable 300 AH at 50% discharge or the equivalent @ 12v.
Keep in mind I live in Canada, any good (cheaper) places to buy that are recommended? Not adverse to making a trip south to buy if it's worth it.

[KX5002]

phemens wrote:
Thanks for all the replies so far!
Running the fridge during the day would be the cherry on top, but isn't a deciding factor. Not ready to make the leap to residential fridge, as we do at least 2x trips a year where we'll leave the trailer at a nearby campground for a month on an unserviced site and do weekends - that's when LP is really nice, no issues with the fridge in the past few years.
Lithium Ion is a nice idea, but would at this stage completely obliterate any 'business case' justification even I could come up with, and I've made some whoppers over the years to convince the boss that I really need what I really don't need 😉
I guess the bottom line question after all this great input is, is there enough of a reason to switch from FLA to AGM given what I'm doing? Right now, my biggest worry is watching the inverter bottom out at 11.4 when running the coffee maker, and it bugs me... strange, I know, but different strokes for different folks. I have a 2k Yamaha genny, just don't like running it if I can avoid it.

FWIW I had my garage fridge (fullsize residential) running off my solar rig (about 200 watts and 450 Ahrs of storage) for a week and the batteries were fully charged at the end of the week, the smaller residential fridges typical in RV's should do even better.

[brulaz]

OldSmokey wrote:

...
for example a 1000 W inverter at max load will draw approx 1100 to 1200 Watts due to inefficiencies
and at 12 volts this is 1200 / 12 = 100Amps ! if we were to do this to a T105 then the voltage drop
would be the ( internal resistance of the battery ) * 100Amps
a T105RE is 0.001 Ohms per cell so thats 0.001 * 6 ( for 12 volts ) so the Vdrop = 0.006 * 100 = 0.6 Volts
your 12 v battery is now only 11.3 volts ! add to this contact resistance and it just gets worse.
your inverter will soon trip out on a low voltage alarm.

if we had 1000 W inverter on 24 Volts you would get: 1200/24=50Amps and Vdrop is still 0.6V
...

Yes, with the same watts of inverter load, we are getting about the same V drop with our 4 GC2s in series, as we were getting with them in parallel. But as that's only half the percentage V drop, we're better off. The new 24V Kisae inverter is certainly a lot happier than our old 12V inverter.

[Itinerant1]

OldSmokey wrote:

Itinerant1 wrote:

OldSmokey wrote:

1000 watts and 12v is a bad idea, better to be in 24 or 48 territory.

Other than wire size which could accounted for why would 12v be bad after 1000 watts?

basically it's all about power. Watts in this case

eg: you have a 100 bulb at 12 V then your amps is 100/12=8.3A

now for 1000 Watts you get 1000 / 12 = 83.3A
that's a lot of amps to handle and basic economics and common sense come into play here

several issues come to mind.. they are:

1. An MPPT charge controller capable of handling 80 to 100A is expensive
typically in the $900 to $1200 dollar range.
2. You will need high current cabling and terminations.
3. Batteries oh yes, there are limts here...

Batteries have min and max charge rates, the ideal is c/10. ( min )
and c/4 ( max ) that is a good range to avoid heating,overgassing and lifespan

The venerable T105RE is a 225Ah battery for example...
and would be very happy with 22.5A charge (225Ah / 10 = C/10 rate)
that same battery would not be happy at 83 amps ( C/2.7 ) too much amperage.
generally the higher charge you apply over repeated cycles, the faster you
will destroy your battery

so you might go down the wrong path here and decide to parallel enough 12V batteries
to satisfy the c/4 max.. but there is a simpler and cost effective way.

you guessed it... go UP in voltage. now if we double the voltage then we will halve the current
so 1000 watts into a 24V battery is now 1000/24=41.6A and you would select a 40 amp controller..
40amp controllers are in the $200 to $300 range .. 1/3 the cost. also you
can reduce cabling requirements, for 83A you would have required 3awg and now you only need
8awg.

another issue here is the amount of amperage that can be drawn from a battery..
I see no end of posts here on the RV forums of issues of inverters and low voltages.
the main reason of course is too big of a power draw and too low voltage, with 12V any loss
from cables or terminations amounts to a large percentage and thats the problem.

for example a 1000 W inverter at max load will draw approx 1100 to 1200 Watts due to inefficiencies
and at 12 volts this is 1200 / 12 = 100Amps ! if we were to do this to a T105 then the voltage drop
would be the ( internal resistance of the battery ) * 100Amps
a T105RE is 0.001 Ohms per cell so thats 0.001 * 6 ( for 12 volts ) so the Vdrop = 0.006 * 100 = 0.6 Volts
your 12 v battery is now only 11.3 volts ! add to this contact resistance and it just gets worse.
your inverter will soon trip out on a low voltage alarm.

if we had 1000 W inverter on 24 Volts you would get: 1200/24=50Amps and Vdrop is still 0.6V

I could write a whole paper on the negative aspects of 12 Volts in systems like this, but
instead I will post a tutorial soon covering recommended solar and battery practices
that should give you guys a good foundation on which to base your systems on.

Thank you for taking the time to explain.

[pianotuna]

phemens,

I would never go back to flooded jars. AGM's do charge to a higher percentage of full before amperage starts to taper. Cell count become important.

I'm waiting for my propane three way fridge to die so I can go to residential.

I'd jump all the way to 48 volts.

Consider using products from one "family" such as Victron, Outback, or Magnum. That way you may be sure everything "plays well together". Hybrid inverter/chargers are the "way to go".

I'm currently at an RV park with "weak" 30 amp power. So I'm using a sola basic autoformer with the load support feature of the Magnum 3012. Not a single over load of the shore power breaker. Water heater on electric, fridge, cooking and heating 100% electrically.



If you never rv in temperatures below freezing then consider LI jars.

[KX5002]

It's the same reason we're don't have 6 volt systems in cars anymore. The same reason big trucks use 24 volts.
Old Smokey has laid it out very clearly

[OldSmokey]

Itinerant1 wrote:

OldSmokey wrote:

1000 watts and 12v is a bad idea, better to be in 24 or 48 territory.

Other than wire size which could accounted for why would 12v be bad after 1000 watts?

basically it's all about power. Watts in this case

eg: you have a 100 bulb at 12 V then your amps is 100/12=8.3A

now for 1000 Watts you get 1000 / 12 = 83.3A
that's a lot of amps to handle and basic economics and common sense come into play here

several issues come to mind.. they are:

1. An MPPT charge controller capable of handling 80 to 100A is expensive
typically in the $900 to $1200 dollar range.
2. You will need high current cabling and terminations.
3. Batteries oh yes, there are limts here...

Batteries have min and max charge rates, the ideal is c/10. ( min )
and c/4 ( max ) that is a good range to avoid heating,overgassing and lifespan

The venerable T105RE is a 225Ah battery for example...
and would be very happy with 22.5A charge (225Ah / 10 = C/10 rate)
that same battery would not be happy at 83 amps ( C/2.7 ) too much amperage.
generally the higher charge you apply over repeated cycles, the faster you
will destroy your battery

so you might go down the wrong path here and decide to parallel enough 12V batteries
to satisfy the c/4 max.. but there is a simpler and cost effective way.

you guessed it... go UP in voltage. now if we double the voltage then we will halve the current
so 1000 watts into a 24V battery is now 1000/24=41.6A and you would select a 40 amp controller..
40amp controllers are in the $200 to $300 range .. 1/3 the cost. also you
can reduce cabling requirements, for 83A you would have required 3awg and now you only need
8awg.

another issue here is the amount of amperage that can be drawn from a battery..
I see no end of posts here on the RV forums of issues of inverters and low voltages.
the main reason of course is too big of a power draw and too low voltage, with 12V any loss
from cables or terminations amounts to a large percentage and thats the problem.

for example a 1000 W inverter at max load will draw approx 1100 to 1200 Watts due to inefficiencies
and at 12 volts this is 1200 / 12 = 100Amps ! if we were to do this to a T105 then the voltage drop
would be the ( internal resistance of the battery ) * 100Amps
a T105RE is 0.001 Ohms per cell so thats 0.001 * 6 ( for 12 volts ) so the Vdrop = 0.006 * 100 = 0.6 Volts
your 12 v battery is now only 11.3 volts ! add to this contact resistance and it just gets worse.
your inverter will soon trip out on a low voltage alarm.

if we had 1000 W inverter on 24 Volts you would get: 1200/24=50Amps and Vdrop is still 0.6V

I could write a whole paper on the negative aspects of 12 Volts in systems like this, but
instead I will post a tutorial soon covering recommended solar and battery practices
that should give you guys a good foundation on which to base your systems on.

[Itinerant1]

OldSmokey wrote:

1000 watts and 12v is a bad idea, better to be in 24 or 48 territory.

Other than wire size which could accounted for why would 12v be bad after 1000 watts?

[MrWizard]

5 AGM , 135 amp hrs each
675 Amphrs total bank, ,649w of solar
PD 70 amp converter,
1250w Tripplite power verter, residential 120v compressor fridge
That inverter and this bank will power an 1100 cooking Watts, 1600 input Watts MW
Or the 950w drip coffee maker
Even the built in vacuum cleaner, one large device at a time
Fridge only uses 100w running

[brulaz]

phemens wrote:

...
Right now I use a combination of a Rogue MPPT at 30 amps for a single 24v 250 watt panel and a Solar Force 30 amp for a legacy 12v array of 3 panels for a combined 290 watts. Agree that moving to a single higher capacity controller is the way to go.

Nice controller. I have one too.

But as I added more 24V solar panels upto 690W I exceeded what the 30A controller could convert at 12V. So I changed to a 24V battery configuration which doubled the Rogue's solar capacity upto 960W.

I would use your Solar Force controller separately for a portable array of light weight 12V panels. Have been thinking of doing something similar for a while.

[grizzzman]

phemens wrote:
Currently have a Jayco hybrid (Jayfeather 26L) but moving to a Denali 5th wheel in the spring (2012 DE324LBS).
Currently have 4 Trojan T125’s with 600 watts of solar, with a Kisae 2000 watt pure sine inverter, we primarily dry camp.
Plan for ‘new’ trailer is to upgrade batteries and solar. Batteries are 5yrs old, serviceable but nearing end of life. Would like to go with 1000 watts solar, and possibly 6 x Crown 6CRV 220 AH AGM batteries. I’ve heard that AGM handle heavy loads better than FLAs. Typical use of inverter now is coffee maker morning and evening, plus TV and occasional limited use of microwave. My end goal is to have enough capacity to run the inverter pretty much any time (i.e. not switch on/off all and ideally run the fridge on 120 during the day to reduce LP use and leverage excess solar during the day.
Inverter is wired to batteries with 4/0, plan for solar is either a single 60A converter with 24v panels or 2x 30 (already have them, but willing to upgrade that too, one is MPPT, the other isn’t.
Got time to plan, so thoughts?

Click For Full-Size Image.
I don't see why your idea would not work. As an example this is the system I'm working on. Having two systems would provide redundancy. Good luck with your project.