AGM float voltage

[ndemge]

Working on home brew battery backup box v2.0

I have 2 7ah AGM UPS batteries

Reading online, float voltage of 13.8

Will 13.9 do damage? I found a 1.5 amp power pack that puts out 13.9, nice and small and makes a great charger. If I were to leave it hooked up overnight, is that extra .1 volt going to harm the batteries?

 

[ZmOz]

Re: AGM float voltage

It will be fine. The cycle charge voltage is about 14.5v. I would check the voltage with a meter though, just because it says 13.9v doesn't mean it is at full or partial load. Harbor freight has 1.5 amp float chargers on sale for $5.

 

[Paul Moir]

Re: AGM float voltage

I think you'll be just fine. Really the range for AGMs is around 2.25-2.30VPC (13.9 = 2.316VPC), +-0.01VPC. You should check with your particular battery's Mfr to be certain. So you may or may not even be in the tolerance of the float charge regime.

But, if you're not charging for more than 15 or 20 days at a time, you're cycling rather than floating. The float regime is really for permanent battery maintenance. The cyclic charging regime is at much higher voltage normally - 2.45 to 2.50VPC typically.

EDIT: Wow, all that fact checking took a looonnng time.

 

[ndemge]

Re: AGM float voltage

I apreciate all the checking.

the 13.9 was checked with a meter. The sticker on the side actually says 13.5

After talking to the guy that got me the batteries (works for a UPS company) They are Sealed Lead Acid. But I still apreciate the AGM education!

I won't actually keep it on a float all the time, the reason for it was to plug it in after I use the thing and just come back the next day to turn off the charger.

I used a small camcorder box, mounted an outlet, cig outlet 2 7ah batteries, 400watt inverter, and this small charger inside.

It's really nice because it can power a small 250 watt clamp on hologen, or run the laptop for a day.

The first one I built had a 90ah battery and a 15amp RV converter inside, it weighed almost 100lbs! The converter recently died, so I did vr 2. The cig lighter plug makes for easy hookup to 2nd battery, or to a car with M-M Cig cord or Cig-Alligator clip cord.

 

[ZmOz]

Re: AGM float voltage

I've made many boxes like that. I can work anywhere I get a cell signal so I need lots of portable power for the bag full of electronics I bring everywhere. Earlier this summer I made a box with a 12ah battery, 4 speakers, car amp, inverter, and 10 watt HID light to take camping. It's really heavy though...I think I'm going to build a lithium ion battery pack.

I also just finished building a generator, with a 7hp electric start engine, 200 amp alternator, 2400 watt inverter, and a big battery. I can get up to 20 amps at 115v with the generator off, and then the generator starts automatically when the battery gets to 11v. I also used a remote start kit for a car to start and stop the generator and control the throttle. Only problem is my power never goes out. d

 

[ndemge]

Re: AGM float voltage

ZmOz....

More info on your home brew generator please

Does the remote start you have have an option already built into it for low-voltage self start, or did you have to make something else for that part of it?

 

[ZmOz]

Re: AGM float voltage

The low voltage start is from a circuit I made a long time ago for another project. My remote starter didn't have that option, but many do. I bought the remote a long time ago for my jeep a few days before I wrecked it. I used a power lock solenoid to control the throttle with the lock button on the remote. d The engine is a B&S intek, which I stroked for more low end torque. I can get about 150 amps with the engine just above idle so it's quiet. I still have to rig something up to power the choke on cold starts...right now it won't auto/remote start cold.

These are the things I think about when it's 4AM and I'm not tired...d