Vmaxtanks VMAXSLR125 AGM 12V 125Ah

AnOldUR · July 2021

Not sure if I made the right choice, but I have a VMAXSLR125 coming later today and will be leaving for camping at the Great Lakes on Sunday. I'd love to have it installed before then, but want to get it right.

My concern is if the Victron MPPT 75/10 is up to the task of keeping it charged? And if so, what settings should I be using? Will being plugged into shore power fully charge the battery?

I'm worried about frying my new battery or the controller ...

AnOldUR · July 2021

So far, no one has had any thought on this, but for those who looked, I did hear back from Vmax. Bottom line is that it will work fine, but if I expect to get a full charge on solar, I'll need to add more panels. I was already looking into a Renogy 100W to supplement my rooftop solar. This may motivate me to move a little quicker. The important takeaway was on equalization they said, "We do not recommend using the equalize feature, please keep this option OFF."

edit to add:
The new battery came this afternoon. All hooked up and should be charging on shore power. Fingers crossed.

Sharon_is_SAM · July 2021

@AnOldUR - I think you have at least a 100 watt panel and your controller is sized appropriately to the output of the panel. No reason why you can’t fully charge using your current panel. It may take longer depending on the amount of sun, and depending on how much you deplete the battery before recharging. The extra panel will allow you to charge faster.

AnOldUR · July 2021

Sharon_is_SAM said:

No reason why you can’t fully charge using your current panel. It may take longer ...

In my communication with Vmax referring to this battery they wrote:

"When charging via solar, 120W is the lowest recommended wattage, ideally you want 175 Watts or more to ensure the battery can be fully recharge each day when shore power is not available. If you are able to plug into shore power each day then you could use the 100W panel to maintain the battery."

At first I interpreted this to mean that the 100W panel could maintain, but not fully charge this battery. Looking back after reading your post, I see that what they were probably saying is that 100W is not enough to "fully recharge each day". So, as you said, it's more about speed than capacity. Thanks for clarifying that.

It was a tight squeeze, but despite being twice the weight, the larger battery fit into the same space as the original. I did have to move the battery switch over to the right because of the bigger battery box.

Unplugged from shore power with refrigerator on to test it out ....

Image: https://us.v-cdn.net/5021717/uploads/editor/n5/zi80cvhob9zf.jpg

Yes, it's big .....

ChanW · July 2021

I contacted my battery manufacturer to get the charge specs, as you did. They too said another panel is 'required'.

I took it to mean "to fully take advantage of potential charge and discharge capacity".

At this point, our battery capacity is much greater than we've ever needed it, and, as long as the panels have a fair amount of exposure, they've been able to recharge fine.

I think it depends on how much you use, and how much sun you get, which is all variable.

AnOldUR · July 2021

ChanW said:

I contacted my battery manufacturer ....

For comparison, what battery(s) did you install and which controller(s) do you have?

Dutch061 · July 2021

For the settings on the Solar Charge Controller, here are some screenshots that should get you there.

Click on Settings

Select Battery

Select Battery preset

Select Gel Victron deep discharge (1) for a single AGM, then OK

Everything should be set property from there for the Solar Charge Controller. IF you add a BMV-712, there are several things that would need to be set up in the BMV-712 but nothing will change in the Solar Charge Controller.

Brad

AnOldUR · July 2021

Good to see the visuals posted by @Dutch061, but they bring up a couple of questions. On the screen shot above, the Automatic Equalization is set to "Disabled". According to Vmax, Automatic Equalization should not be used with the battery I purchased. That setting looks right for me also, but I don't see how to set it to disabled? The other thing is "State" on the screen shot is at "Float". Right now, mine is at "Bulk". Will that change as the battery goes through the charging process or should this be set by me?

Another slightly unrelated question. My Domenic 12V fridge has a voltage readout. While it's running the value is a full volt or more below what the Victron app reports. I'm thinking that is because of voltage drop between the fridge and the battery, but want to confirm that. When the compressor is off they read pretty close to the same. Is the value on the Victon app the accurate one?

Dutch061 · July 2021

Okay, you are looking in the background at my settings. I have 2 Battleborn Lithium batteries installed so don't worry about that. If by chance you need to change it, turn on the "expert mode" make the changes and turn it back off and they will stick.

Voltage differences are exactly as you mentioned. On the Victron App you are seeing the voltage that is going out and on the refrigerator you are seeing the voltage under load. These will never be the same unless they are in the same state, even in the same state there will be minor differences due to the difference in the location being measured.

Yes, my batteries are fully charged so the proper state is "float" whereas if you are not 100% charged it will always show Bulk.

Hope this helps.

Brad

pthomas745 · July 2021

There is no reason that you need more panels for a 125AH battery. Your 100 watt panel will charge it just fine, it will simply take a slightly bit longer. Why a manufacturer would say you need 200 watts for 125 amp hours makes little sense.

ChanW · July 2021

Heh! Sorry, that might help.

I have the Victron MPPT 75/15 with 200W of panels, and 2 Crown CR-220 6V lead-acid 'golf cart" batteries.

AnOldUR said:

ChanW said:

I contacted my battery manufacturer ....

For comparison, what battery(s) did you install and which controller(s) do you have?

Shadrax · August 2021

A rough but simple explanation, easy to remember, is that you need a 100 watt solar panel to charge a 100AH battery!

DougH · August 2021

I had 3 of those VMAX 125s in my 320. Great batteries.

AnOldUR · August 2021

DougH said:

I had 3 of those VMAX 125s in my 320. Great batteries.

If money were no object, I'd get both, but right now I'm trying to decide between a second VMAX 125 or a generator. I'm not a fan of generators and would only use/bring it in really hot weather for the air conditioner. The single VMAX performed well on our recent trip, but we were never more than two day without shore power. Heading out again on Wednesday for a week long trip through the New England states. Mix of Harvest Host and campgrounds without electric, so this will be a good test. I did just score a deal on a (used/very good) 100W Renogy suitcase that should be here today. I'm leaning toward a second battery to make better use of the solar. The biggest downside to the battery is that it weighs almost twice the weight of the generator.

stepheng · October 2022

Has anyone used the VMAX XTR31-135. It's a 135ah deep cycle.

pthomas745 · October 2022

@stepheng Maybe not that specific battery, but there are many VMAX users here. Some threads/

https://www.google.com/search?q=VMAX+site:tab-rv.vanillacommunity.com&client=firefox-b-1-d&sxsrf=ALiCzsauLqPdHgznTUzuEPnmbVUcoklITw:1666521103621&ei=DxhVY4TMJeuwkPIPtJibiAc&ved=0ahUKEwjEj5Hzkvb6AhVrGEQIHTTMBnEQ4dUDCA8&uact=5&oq=VMAX+site:tab-rv.vanillacommunity.com&gs_lcp=Cgdnd3Mtd2l6EANKBAhBGAFKBAhGGABQrgxY-xxggyZoAXAAeACAAU-IAfAFkgECMTCYAQCgAQHAAQE&sclient=gws-wiz

Vmaxtanks VMAXSLR125 AGM 12V 125Ah

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