Home power backup with solar.

[jongig]

Hello and thanks for the forum, great reading.

I have a 5000VA UPS backup in our house that's hardwired and 25 years old. It's worked flawlessly for so many years but it uses large AGM batteries and they're old.
My system has a plug outside so I can connect my propane generator with longer outages. We only power circuits that are important and the TV.
I'm buying a Victron multiplus 2, 5000VA, 120V and 24volt-battery voltage. I'll also add solar, I actually have extra panels from my boat I never used.

Today's question is battery purchase and here's what's different that you've never heard of. I have an electric cart. it's 6-wheel drive, can move a 15K pound trailer and uses Dakota LifePo4 batteries. It has 4-60AH 12Volt batteries and the cart is 24 volts. I want to plug the cart into the new backup system both for charging and additional battery reserve.
Would I be able to purchase 24V LifePo4 batteries that are a different AH from the cart and still connect the cart to the backup? If the answer is no, I'll replace the batteries in the cart to use the same 24 volt LifePo4 batteries the backup uses.

 

[Q-Dog]

The problem with connecting additional batteries to the main system is you need to make sure they are close to each other in voltage before you connect them together. If they are too far apart the higher charged battery will dump power into the lower charged batteries, possibly at a very high rate.

 

[kc130up]

Like was stated, just make sure the batteries are "very close" in voltage to prevent sparks and/or too much current dump in one direction or the other.

 

[ekrainey]

ive done this a few times adding batteries. i have all jkbms and i go in and adjust the discharge rate first

 

[50ShadesOfDirt]

I would appreciate pictures of the 6-wheel drive "beast"!

I would vote for the option of using all the same LFP batteries ... move the old stuff out (sell 'em if you can), and move the next generation of new stuff in (you get all the new tech that has occurred since).

I think such electric devices used around the homestead are the "next wave" of (excess solar) power utilization ... convert the excess to electric horsepower! I have tool batteries (proprietary, but at least recharged w/ solar), electric-motor carts (48v!), and more ... no more gasoline fuel, or fuel engines. The Stihl chainsaw is last holdout, and it's surrounded by 'lectric chainsaws ...

 

[jongig]

Interesting. I had not considered the issue of current flow from the charged bank to the discharged batteries in the cart.

The cart is not finished, it's replacing this cart

. I built this years ago and it works great, I've put over 500 pounds on it. The new one will have a ball hitch in the middle of the cart like a gooseneck and be able to move our 15,000 pound boat around on the trailer. These carts are nice since you just turn them on and they work.

I will purchase batteries for the cart and the house. Does it matter if the house batteries have comms and the cart doesn't? I was looking at SOK 24 Volt SK24V150PH, they're 150AH with comms. I would put two in the cart laying down. The 9.5 inches lying down is about 2 inches more than I wanted for the cart but for $999 they seem like a good price point. For the house I'll install 4 batteries. That puts me close to the 1,000AH/24V I'd like.