Battery too good to be true???

[Buster1903]

Yo,

Just bought a battery off of Amazon. Miady LiFePo4 Battery 12V 6Ah I want to know how to test it to see if it produces the numbers it claims to.

Also interested in how to charge this lithium iron phosphate battery off of my cars alternator.
Charge Voltage: 14.6±0.2V

Charger Current: 1.2A
Max. Charge Current: 3A

Will have more questions about my house battery, charging, solar set up but didn’t want to pass on this battery opportunity.

 

[abnorm]

It's a SIX AH battery...……THAT'S TINY !…………...What are you going to use it for ?


For example MY 12 volt battery bank that runs everything in my van is about 450 AH...………………..

 

[Elbear1]

A powerwheels battery lol

 

[brahmon]

ooof

 

[AuricTech]

To be fair, depending on how much a 12VDC charger costs, add a 12V-to-USB charger to this battery and you have a quite cost-effective USB recharging device. After all, how many commercially-available USB battery packs at anywhere near that price have over 75 Watt-hours capacity?

As part of a house battery system, though, this battery can play no significant role. Its capacity is far too low for anything beyond recharging a few USB-powered items. Fortunately, such items include fans and fairly bright lights, most of which have a fair endurance before needing recharging.

 

[1shemp]

You have to measure the ah capacity of the battery versus the anticipated use of the inverter and the maximum amount of the watt hours input of the system.

 

[Cajunwolf]

Besides this forum, one of the other great places for good LiFePO4 batteries and solar information is Will Prowes's channel and forums. He specializes in LiFePO4's. There is a thread that addresses your charger question. He has several videos on how to build high-quality LiFePO4 batteries from individual cells and save a bundle on high-end batteries. I looked at this battery up on Amazon, and the only thing that bothers me is the 2000 cycles. Most of your better LiFePO4's are good to 3000 to 5000 cycles, but for $30 bucks, it's worth a chance. I helped a friend down in Galveston set up an electric drive sailboat using Battleborn batteries, but he had the money for the best. We set up a 48v system with a 20kw motor as auxiliary propulsion. He has 600 watts of solar with a 500-watt turbine for those windy evenings. He can run for days on those batteries, but he has 400ah.
This guy is a great additional resource and specializes in van and RV DIY systems.
the channel: https://www.youtube.com/user/errolprowse
The Forums: http://www.diysolarforum.com/index.php[/size][/color]

 

[Cajunwolf]

I found that thread, and it's appropriately named "How to charge my RV batteries from my Tow Vehicle Alternator while driving"
http://www.diysolarforum.com/index....hicle-alternator-while-driving.390/#post-3760"

 

[Buster1903]

Thanks Cajunwolf. I will check this out. I know the channel and forums. thanks for finding the useful thread

 

[Cajunwolf]

No problem, and glad I was of help.

 

[Buster1903]

Thank you all for your interest, however pointing out to me that 6ah is a very small battery is not helping me answer the questions. 

I have a 4‘ x 8‘ TTT, all I need the battery to do is run a small  a 1.6 amp exhaust fan and a few LED lights anything more than that is just gravy. Four of these batteries set up in parallel should give me more than enough capacity and output for the job. And at $5/ah for LiFePo4 these little batteries are hard to beat.

My alternative is this Mighty Max Battery ML35-12 - 12V 35AH But at over 20lb. the weight becomes a concern. 4 Miady LiFePo4s should be under 7lb. and since my tow vehicle is an old Honda civic every lb counts. 

I would also rather have a LiFePo4 over a AGM. I just wanted to know how to test it to see if it performs as advertised.

Again thank you Cajunwolf.

 

[Cajunwolf]

Heck yeah, that gives you 300Wh at 12v pushing six amps, not shabby for the price, good call. Also, you would buy ten or more AGM SLA batteries to equal the cycle life. The LiFePO4's are the cheapest way to go long term.

 

[jonyjoe303]

to test lifepo4 to see if it has the proper capacity you need a coulometer. Once the battery is full (14.6 volts), as you use it, it counts down all the amps until the bms shutsoff. 

I use the tk15 (cost 23 dollars on ebay) but you can also use a dc wattmeter (cost 15 dollars) , the tk15 is biderectional it reads amps in/out, dc wattmeter only reads in one direction. They are both accurate.

If I were you, I get the tk15 and keep it connected to the battery 24/7, its what I use. With lifepo4 the resting voltage is always 13.1 volts whether 90 percent or 10 percent, only way to know the status of your battery is to count the amps you use. The cheapest tk15 can handle up to 50 amps in/out, more than enough for your batteries. The smaller the batteries, the more important the ability to track every amp you use.

picture of dc wattmeter and tk15 coulometer

 

[Cajunwolf]

@jonyjoe303

Good post! I have my handy TK15 in my bag at all times. Your right on the bi-directional aspect and this helps find phantom loads. Forgot all about it and how useful it would be for this situation. Kudos!  :thumbsup:

 

[Buster1903]

Thank You jonyjoe303. I'm learning. It looks like this will double as a battery monitor too. Battery Coulometer TK15

 

[Buster1903]

Now how do I safely charge this? 
I have a "Battery Tender" input 110V AC - Output 12V 1.25Amp this should work for testing. 
But how do I charge a set (4 in parallel) of these from my alternator (and solar at some point) 

Just one:
Charge Voltage: 14.6±0.2V
Charger Current: 1.2A
Max. Charge Current: 3A

I assume :s   4 in parallel would handle 14.2V at 4.8Amps. How do I regulate the Volts and Amps from my cars 12 volt system (Alternator)
My Alt. should be putting out 13.8ish Volts but it will be highly variable. And I'm guessing it will just give you all the Amps its got if I put it in direct parallel with the starting battery. I don't want to "FRY" this setup the first time I go to charge it.

 

[Buster1903]

OK, I know I’m answering my own question here but this is a learning process for me.

The answer seems to be some kind of DC to DC charger that is designed to handle lithium batteries. The link Cajunwolf posted also gives A suggestion of a combination MPPT solar charge controller and DC to DC charger. I still have to figure out how not to overload my small alternator.

All of these options seem to be blowing the heck out of my budget. I can afford the upgrade battery to LiFePo4 but I can't afford the charging equipment. After all my house battery is really about comfort and convenience. The money I have needs to go into quality parts for my tow vehicle.

 

[bullfrog]

What I did with TTT was build it with Ryobi 18 volt tools using their vehicle charger and 4 amp hour batteries. Then bought their lights, fans and wet dry vacuum. After I saw how well this worked I added solar which powered the vehicle charger and bought the larger 18 volt batteries that would run my fan 8 hours (over night) on sale. Just before Christmas is when they usually happen. If you get and purchase them with a Home Depot credit card you can get a better warranty which allows you to exchange them in store nationwide. Getting the "One" latest tech batteries really made this an easy build but if you don't buy when the sales are on it gets costly.

 

[Cajunwolf]

@bullfrog
Howdy!
@Buster1903
Have you already bought the battery?

 

[Cajunwolf]

@Buster1903

Check out the post by one of our members, LoupGarou, on a thread I started showcasing a useful dynamic solar selection site. This might help you a lot. The link (he and I both subscribe to the site) he gives has a video on the dangers of using your vehicle's alternator to charge house batteries with solutions.

https://vanlivingforum.com/showthread.php?tid=38414