Scrap Yard Batteries

[blissout]

My local scrap yard has a ton of used car and golf cart batteries for $12 each, and I'm wondering if I can use them in my build.

I'm building a box for them under the bus and I'm thinking if I get a good inverter maybe it will smooth out any differences in the batteries. I'll probably end up with different brands also. I know it's not ideal, but can it work.

I'm planning to run a 12V system with 600Ah of batteries to start.

 

[o1marc]

It's important to have batteries that match in brand, size, and condition. I would need to take each battery I wanted from there and put it on a charge and test machine to see their current condition. I killed my group 31 by overcharging it.

 

[blissout]

It's important to have batteries that match in brand, size, and condition. I would need to take each battery I wanted from there and put it on a charge and test machine to see their current condition. I killed my group 31 by overcharging it.

There were several matching batteries so I'll be sure to get those only.

What's a charge and test machine? Can't I tell if it holds a charge with a multimeter?

 

[peteg59]

Test with a battery load tester. Something like this:
https://www.northerntool.com/shop/tools/product_200611634_200611634
A multimeter will show voltage which is helpful but will not tell the actual health of a battery. Some unscrupulous seller could charge up a weak battery to show 12 volts on a portable multimeter, but put it in your vehicle and try to fire it up only to find that the battery can't handle the load.

Unless you can't afford new, I'd stay away from "used" battery(ies).

 

[blissout]

Test with a battery load tester. Something like this:
https://www.northerntool.com/shop/tools/product_200611634_200611634
A multimeter will show voltage which is helpful but will not tell the actual health of a battery. Some unscrupulous seller could charge up a weak battery to show 12 volts on a portable multimeter, but put it in your vehicle and try to fire it up only to find that the battery can't handle the load.

Unless you can't afford new, I'd stay away from "used" battery(ies).

Ah, gotcha. I'll definitely pick up a battery load tester to check the health of the batteries.

But am I correct with my assumption that a good pure sine wave inverter can handle these old batteries and give me clean power?

 

[jofred99]

So long as the batteries will provide power, a good sine wave inverter (matched to your load requirement) will provide the AC for you.

 

[o1marc]

There were several matching batteries so I'll be sure to get those only.

What's a charge and test machine? Can't I tell if it holds a charge with a multimeter?

You won't be able to test it to higher degree than a parts store will. O'Reilly's and most of the part stores will hook it to a machine that puts a load on the battery and determines it's condition and how much life is left in it and then charge it. This service is free.

 

[HazMatt-SKO]

But he'd have to buy them first, to be able to get them bench tested.
Go for it, provided they'll refund any duds.

 

[blissout]

You won't be able to test it to higher degree than a parts store will. O'Reilly's and most of the part stores will hook it to a machine that puts a load on the battery and determines it's condition and how much life is left in it and then charge it. This service is free.

Yeah but I think a battery load tester is a good idea. 20 bucks at Harbor Freight with 20% off isn't bad. Then yeah I can take them to O'Reilly's to get charged if they're good. But I should test them before buying them even though they're only 12 bucks

 

[o1marc]

Ah, gotcha. I'll definitely pick up a battery load tester to check the health of the batteries.

But am I correct with my assumption that a good pure sine wave inverter can handle these old batteries and give me clean power?

Yes they will provide power, how are you recharging the batteries? It isn't a question of whether the batteries will power on or not, it's how long they will last if they are now compatible batteries.

 

[o1marc]

But he'd have to buy them first, to be able to get them bench tested.
Go for it, provided they'll refund any duds.

Which is one reason to stay away from used batteries.

 

[HazMatt-SKO]

Agreed.

Which is one reason to stay away from used batteries.

Too many unaccountable variables to trust in them, especially when a hundred miles from the nearest outpost of civilization...
"Short cuts make for long delays." To which, I'd add:
When corners are cut, things tip over more easily...

 

[o1marc]

Agreed.Too many unaccountable variables to trust in them, especially when a hundred miles from the nearest outpost of civilization...
"Short cuts make for long delays." To which, I'd add:
When corners are cut, things tip over more easily...

I have an example of an exception to the rule. While working at O'Reilly Auto Parts a woman came in to replace her Motorcraft battery. We don't carry Motorcraft brand and she would not except anything else. I had tested the battery and it showed "in it's last 1/4, replace soon". I offered to buy her battery at the core charge price of $18.00, She said she wouldn't have a trade in at the next place. I said I've already given you the core charge here. I put it in my Dodge Dakota and ran it for another 3 years, which exceeded the original warranty on it.

 

[jofred99]

I like reliable. Used batteries are likely to be ones that have given someone else problems.


I have 4 Trojan T-105 batteries running some lights and a freezer at my house that I bought new in 2011 and are just now starting to show a little age. Just me, but I consider those to be a pretty good bargain.

 

[blissout]

Yes they will provide power, how are you recharging the batteries? It isn't a question of whether the batteries will power on or not, it's how long they will last if they are now compatible batteries.

I'm going to be using shore power to recharge, then I'm adding solar panels and an alternator charger and probably a windmill. I'll have a good charge controller because I plan to replace them with new lithium batteries later. Or maybe I'll just get more junkyard batteries since they're so cheap. If these last me 6 months I would consider them worth it because I only spent 100 bucks on this first set. I look at them as disposable. I honestly don't

 

[o1marc]

I like reliable. Used batteries are likely to be ones that have given someone else problems.

.

In this particular case I would not assume they were someone elses problem if they are being pulled at a scrap yard, likely 100's of cars with good batteries.

 

[HazMatt-SKO]

Heckuva score! A rare outlier, to be sure.

I have an example of an exception to the rule. While working at O'Reilly Auto Parts a woman came in to replace her Motorcraft battery. We don't carry Motorcraft brand and she would not except anything else. I had tested the battery and it showed "in it's last 1/4, replace soon". I offered to buy her battery at the core charge price of $18.00, She said she wouldn't have a trade in at the next place. I said I've already given you the core charge here. I put it in my Dodge Dakota and ran it for another 3 years, which exceeded the original warranty on it.

'Course, you just made the OP's point for him with that tale!

 

[blissout]

Heckuva score! A rare outlier, to be sure.'Course, you just made the OP's point for him with that tale!

Look, I'm not under any illusion that a $12 battery is comparable to a $400 battery. I'm not asking if a used car battery is as good as a brand new lithium battery. I'm asking if used car batteries can work, and if a good inverter can mitigate some of the many variables involved with buying cheap used batteries.

If they're going bad, I'm assuming my battery monitor will alert me to that problem beforehand. I know I'll have to monitor these things more, but I'm saving over 90% on them so I consider that a fair trade.

 

[o1marc]

Heckuva score! A rare outlier, to be sure.'Course, you just made the OP's point for him with that tale!

Different application, I would not have bought the battery for an addition to my battery bank.

 

[HazMatt-SKO]

Well no, obviously.

Different application, I would not have bought the battery for an addition to my battery bank.

Three years for $18 ain't too shabby for a battery scoring only 1/4.