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Old 10-01-2019, 05:15 PM   #1
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Solar 400W with 200A gel?

My son is researching adding solar to his new RV (lifestyle change). He has ordered a 400W kit and is considering going with 2 100A gel batts:
https://www.renogy.com/deep-cycle-pu...12-volt-100ah/

My only experience is with lead-acid, and I would have said that bank is too small. But maybe gel means you can go further with less?
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Old 10-01-2019, 05:21 PM   #2
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Gels have particular charging profiles that some solar controllers and certainly the typical RV converter can't handle.

If you want a 100A 12V non FLA battery, try this AGM for $188 https://www.amazon.com/dp/B07BS1ZB15...v_ov_lig_dp_it

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Old 10-01-2019, 07:42 PM   #3
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Totally agree with David. Unless your son has a real good reason to go with gel batteries I would strongly suggest standard flooded lead acid or AGMs.

As far as total bank size goes, it really depends on his loads. Same goes for size of solar array.

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Old 10-01-2019, 08:10 PM   #4
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His thinking:

I was thinking the bonus of the Pure Gel batteries is that:



The GEL support 1100 cycles compared to 700 on AGM.

You can use up to 80% of the available battery compared to 50% on AGM.

100aH battery weighs 60lbs, which I can lift. 66lbs not sure��
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Old 10-01-2019, 08:24 PM   #5
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Quote:
Originally Posted by Sunset View Post
His thinking:

I was thinking the bonus of the Pure Gel batteries is that:



The GEL support 1100 cycles compared to 700 on AGM.

You can use up to 80% of the available battery compared to 50% on AGM.

100aH battery weighs 60lbs, which I can lift. 66lbs not sure��

Following the link you gave above, the battery manufacturer says not to discharge below 50% and gives lifetime of 1000 cycles. My understanding is that with any lead acid battery, the deeper the discharge the shorter the life. So you can discharge gels to 20% SOC but you will get fewer cycles than if you discharge to 50% SOC.
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Old 10-01-2019, 08:43 PM   #6
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The size of the battery bank depends on his usage. The size of the solar array depends on expected weather and expected recharge rate. Without some idea of these any answer is meaningless. "Without a plan, any action is rational."

With a good solar controller, the batteries will not be damaged by the solar array regardless.
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Old 10-01-2019, 09:55 PM   #7
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I installed a small solar system this summer for a friend building an off-grid cabin in Montana. Large victron MPPT controller sized for eventual cabin. 2x250w renogy panels and 2x6v FLA batteries with a Xantrex 2kw PSW inverter. At first test, pull from older Skil Saw worm drive (16a @ 120vac) tripped inverter but once the solar kicked in, worked fine for weeks on end.

As someone else said, depends on how you plan to use the system. Building during daylight hours does not require much battery capacity. Hanging out at home all evening would require a much greater battery bank. A "marathon" vs a "sprint."
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Old 10-02-2019, 05:50 AM   #8
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WLA are usually best first choice , especially if there is a warranty from a big box store.

Until a SOC meter is installed, weather the batts are being killed is a guessing game.

Some sellers will stop replacing killed batts after 3rd time.
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Old 10-02-2019, 09:05 AM   #9
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keep it simple,
400 watts is ok on an RV depends on needs ( I had 1050)
but he don't need a kit, buy a 400w panel, then buy a MidNite KID controler it will work great

I did a friends with a 500w panel on his RV with a KID


On my new 42 I'm putting two 265W on a new hardtop but that is just tad over the KIDs range

use 4 or 6 6V Trojan golf batteries many solar guys use them $100 each, with solar they can go 7 years plus
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Old 10-02-2019, 09:26 AM   #10
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The solar array size is fine, but with solar bigger is better. The batteries, on the other hand, are pretty minimal unless all he is going to run is lights. As mentioned above, he needs to work out his expected loads (total watt-hours) for 24 hours and size his battery bank accordingly. He also needs to think about how he is going to use the RV. If all he plans to do is stay in sites with electric most of the time and boondock for a night now and then, the 200 amp hours of batteries will be an OK minimum. However, even that depends on what he expects to power. Running coffee maker, microwave, hair dryer, TV and sound system will flat 200 amp hours of any kind of batteries in short order. He also need to be aware of hidden loads like the electrical system on the propane fridge and the propane solenoid valves in the fridge, water heater and space heater. Those things alone can easily use 30-50 amp-hours per day. In contrast, if he wants to boondock for multiple days or even a week at a time, he needs to size his battery bank to handle all loads for 2-3 days at a minimum because it isn'ty always sunny and RVs sometimes get parked in full or partial shade.


As far as the number of cycles to expect from the batteries goes, the deeper the discharge between charges the fewer cycles you will get from a battery. That applies to ALL types of batteries including lithium. So if he under sizes his battery bank he will kill the batteries quickly. In contrast, over sizing the battery bank will give much longer life. Now, as to battery types. Gels would be my last choice because they are the most expensive of the conventional battery types (Flooded, AGM, Gel) and don't give enough extra bang for the buck to make up for the cost difference. As stated above, Gels are also more fussy about charging voltages than other batteries and the converter in the RV (DC power supply/battery charger) is highly unlikely to treat Gels well. The solar charge controller won't be a problem IF he gets one that has a Gel setting or is programmable (Victron). Battery type depends on a number of things including budget, concern for battery off gassing and how long he expects to own the RV. Budget is generally the biggest factor. As far as budget goes the order of preference is 12V Grp 27 or Grp 31 flooded deep cycle, flooded 6V golf carts, 12V AGM, 6V AGM golf carts, lithium iron phosphate. If your son is concerned about battery out gassing then he needs to go AGM or lithium. Finally, if he intendsto own the RV for 10+ years and has the money it is worth considering lithium iron phosphate batteries such as Battleborn batteries.


My suggestion for the short term would be to go with four 100 amp-hr flooded 12V deep cycle lead acid batteries. He can get decent batteries for $100 each. Unless he charges them at very high charge rates off gassing won't be a big problem, but they do need to be in a vented location. I can't say more than that without know what his expected loads will be (i.e., lifestyle and RV size).
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Old 10-03-2019, 01:06 AM   #11
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Fireflies made by Caterpillar are almost like lithiums, expensive but less expensive than lithiums. The batteries were made to be abused. Caterpillar was having a lot of problems with dead batteries in larger equipment that sat around for a while so they designed a new battery. People regularly abuse them and yet they bounce back like lithiums. You don't have to worry about charging only to 50 %. They are 116 amps which gives 236 amps and at 80 % usability, you get 188 amps.

Here is information on them:

https://oceanplanetenergy.com/advanc...asis-group-31/
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Old 10-03-2019, 06:20 AM   #12
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50% DOD ~3600 cycles
50% DOD ~3600 cycles $515 each

AT 5 times as expensive I would use 2x the WLA ($100 or less each) , especially till he understands how he will use the RV. (4 ) 6v golf carts.
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Old 10-03-2019, 09:06 AM   #13
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Quote:
Originally Posted by lipets View Post
keep it simple,
400 watts is ok on an RV depends on needs ( I had 1050)
but he don't need a kit, buy a 400w panel, then buy a MidNite KID controler it will work great

I did a friends with a 500w panel on his RV with a KID


On my new 42 I'm putting two 265W on a new hardtop but that is just tad over the KIDs range

use 4 or 6 6V Trojan golf batteries many solar guys use them $100 each, with solar they can go 7 years plus

Be careful with the KID controller with a boat. They are terribly noisy. I added all sorts of clamping ferrites, conditioners, and re-routing of wiring to try to mitigate the noise in the VHF. I finally resorted to turning the solar array off while underway, the noise in the VHF was untenable. I still have the problem, but it's manageable. I also had to have it replaced in wty, display flaked out, and it had a bad connection on one of the 30A fuses that burned the fuse. I would NOT choose the MidNite KID nor recommend it. I have not heard mention of a single issue of RF noise with the Victron, better features and more control with that.

FWIW...
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Old 10-03-2019, 07:22 PM   #14
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Be careful with the KID controller with a boat. They are terribly noisy. I added all sorts of clamping ferrites, conditioners, and re-routing of wiring to try to mitigate the noise in the VHF. I finally resorted to turning the solar array off while underway, the noise in the VHF was untenable. I still have the problem, but it's manageable. I also had to have it replaced in wty, display flaked out, and it had a bad connection on one of the 30A fuses that burned the fuse. I would NOT choose the MidNite KID nor recommend it. I have not heard mention of a single issue of RF noise with the Victron, better features and more control with that.

FWIW...

Never had an issue with the KID's go on the solar forums for more reviews
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