I have a UPS with a dead battery. It's one of those little SLA 12v things. It kinda struck me that the guts of that thing would have a regulated power supply for charging and an inverter for 120v.
What's stopping me from attaching it to a larger bank of batteries for more Ah? I can measure the output voltage, but it would likely be helpful to know the amperage of the charger. I can't really imagine it's very high given the little SLA batteries inside. If it is capable of 4A, I think that would handle a couple deep cycle units.
I suppose I could hook it up to a car battery and throw an ammeter inline I guess, but that would only tell me how much the battery is accepting, not necessarily how much it can provide.
TL;DR, anyone know how much charge amperage I can expect from it?
Depends on the model, but you can find the info. I have several I've torn apart also. Many have a limit on how long they will run on battery power. You may need a computer connected, or to reprogram it. once again, depends on how old/dumb it is. It does work, just depends on how long and how much power you want to pull from it.
Also, most are square wave. Just be aware it can damage some electronics (weird since designed for computers...).
The battery I took out of it is dated September of 2003.
Well bro you are asking two different questions. What are you after? Amperage or Amp/hours?
Max output would be printed on the case somewhere, either as amps or watts, or you gotta google the model number. You can get max amps by dividing watts by 120 volts (ASSuming 120VAC output)
Increasing amp-hours is a matter of increasing battery capacity, just get a larger battery and wire it up in place of the existing.
You are gonna run into a few challenges that tell me just bin this unit and buy one from Amazon.
- These little buggers are rarely built for starting loads, they are built for maintaining a started load. So their startup surge tolerance is pitiful. They are also used to run computers, not circular saws.
- They will charge SLOOOOWWWWW. The charge circuit is designed with the long game in mind, speed of recharge was never a design priority. 10x the battery capacity, 10x the time to charge. It wouldnt surprise me if these things take days to charge up a 100AH battery.
- Whatever battery tech they were made with, they need to keep or they will short charge or overcharge the battery. All the tech (flooded, agm, lithium, etc) use different charge rates, float voltages, etc. There isn't a practical way to change this so you are gonna gets what you gets.
- You gotta buy a battery (see note above about matching battery chemistries/styles with OEM)
- Its gonna be heavy, cumbersome, and worse than a purchased solution.
For $500....
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In reply to 93gsxturbo :
The Ah will be determined by the battery I hook it up to. I don't have any high-draw items, so the bulk amperage isn't what I'm after, it's storage (Ah). The factory battery in this UPS was 7Ah, but what I was wondering was if the charger part had enough amperage to charge a larger battery. I was just spitballing that the UPS has an integrated regulated PS and an inverter, meaning it's an all-in-one box that can give me 12v or 120v. My thought was to replace the battery with a larger SLA to get more Ah.
I know what the 120v output is because it's listed on the box, but it doesn't list the charge output for the battery. It only lists 120v ratings for input and output, not the charge circuit.
Unfortunately, if the info I found is correct, it's a 3W charge circuit, which means less than 0.25A. Not enough. It would take a week to charge, if it effectively charged at all.
Can you get a real converter out of a junkyard RV ,
I have bought them for $20-$30 at the swap meet ,
Probably still going to be Square Wave.
I would think 30W is more likely. I can't quite read that model number, but I can see it's a pretty small unit. Best usage is wiring up that battery terminal to some alligator clips and using it on a car battery to power some random laptop charger or something you have that is only 120 and you want in the car. But it may need 120 to even power on the inverter in the first place.
californiamilleghia said:
Can you get a real converter out of a junkyard RV ,
I have bought them for $20-$30 at the swap meet ,
Probably still going to be Square Wave.
Not a bad idea, but it won't have the inverter.
bbbbRASS said:
I would think 30W is more likely. I can't quite read that model number, but I can see it's a pretty small unit. Best usage is wiring up that battery terminal to some alligator clips and using it on a car battery to power some random laptop charger or something you have that is only 120 and you want in the car. But it may need 120 to even power on the inverter in the first place.
I doubt it needs 120v to run the inverter. That would kind of defeat the purpose of a backup power source.
It's an APC be500u. I found this on APCs website.
I also have a much larger UPS that I could research, but unless it's a significant charge amperage upgrade, it won't be enough to charge the Ah I'm hoping for.
I think I'll just scrap the UPS idea. I was hoping for an easy button. I can just do a Noco genius and an inverter, but the bonus of the UPS is that it's a seamless transition from shore power to unplugged. The same outlets switch between the inverter and 120v automatically, whereas I would always be drawing through the Noco/inverter regardless of whether or not I'm plugged in to shore power.
Plug a 120V-12V charger of your choice into the non-battery side of the UPS so it charges the battery when the UPS has 120V-in power?
Redarc Manager 30 is what you need, it will switch seamlessly between 120VAC and 12VDC power sources (alternator, battery, solar), then couple that with the inverter and battery of choice and you have a sweet setup.
Question is what loads are needed to be run on 120? Best case is always to run 12VDC or battery loads.
500w heater when it's cold, and a ~250w squirrel cage exhaust fan when it's hot. There might be a mini fridge in the future. This is for a van conversion, so it's not like a 30' luxury 5th wheel with all the bells and whistles.
100% go Chinese Diesel Heater for the cold, i tried running a 1500 watt electric heater in my fully insulated regular body Econoline an and it barely took the edge off when it was 40 degrees out.
For the warm go with either a rechargable fan (Milwaukee M18 with 2x 12ah batteries will run 10 hrs a night for a week no prob) or a low draw DC van like a maxxair. I like the M18 option since i can use it outdoors too. Full disclosure I have both and they both do great.
Mini fridge get a dedicated DC model, they are much more efficient than using an inverter to turn 12V into 120V.
Ahh yes, that old chesnut. That model will shut down after 45 minutes no matter how big a battery you put in it. A lot of those don't let you hot start it off battery if it's been sitting without power.
I have a couple of much newer bigger IT-UPSes that will work for you. Including some beastly 48V ones (and some good 24V ones). I don't think I'm coming up to PA/Jersey this year, but I can express them to you, or send them to the challenge. I'm in SC.
That would be lovely. Do you happen to know model numbers that I could check specs? Or do you know specs?
I would mostly need to know how much juice they have and if they'll fit in the spot I want to use in the van.
I suppose I could also stop by on my way to the challenge, but I'm not 100% certain I'll make it this year.
The phone bank/server at a place I used to work was on a UPS. When the power would go out, the little batteries had a lifespan measured in minutes. That's fine for running a computer long enough to shut it down, but not good if you need the UPS for your business's phones to work.
We found that the UPS worked just fine when paralleled to the largest 12V batteries we had in stock 
Pete. (l33t FS) said:
The phone bank/server at a place I used to work was on a UPS. When the power would go out, the little batteries had a lifespan measured in minutes. That's fine for running a computer long enough to shut it down, but not good if you need the UPS for your business's phones to work.
We found that the UPS worked just fine when paralleled to the largest 12V batteries we had in stock
That's what I was thinking... just throw a couple deep cycle marine batteries on it, but the UPS I have is only a 3w charger. Poop.
Curtis73 (Forum Supporter) said:
That's what I was thinking... just throw a couple deep cycle marine batteries on it, but the UPS I have is only a 3w charger. Poop.
I expect a larger UPS will have a larger charger -- likely there's some standard charge time they design for and thus scale the charging circuitry in line with the battery capacity.
If it's going in a camper, do you really want to charge it with wall power? Wouldn't some solar panels on the roof be a better choice?
I've got an Eaton 5P1500 (2U rackmount size), it takes 48V battery. Also a 5P750, it uses 24V (1U rackmount). They are both pure sine, and you can decide to let the battery run for as long as you want. I may have a 12V unit kicking around if I can find it. I know I have several old ones i've pulled out of battery recycling, i'll see if any of them have some quality. If they don't have a fan that runs while on the battery, they won't do well trying to stay on more than 30 minutes.
The smarter UPS may have a setting where they only put back into the battery what they measured it discharging. If you want this for the camper setup you will be much better off sticking to DC, and why wouldn't you either charge the batteries at home, or by the alternator while driving? Not being snarky, genuinly wondering as someone who seems to do similar things and also is a cheap bastard who won't throw stuff out.
This is the inside of the 5P750. These are pretty high end units (compared to what you get at Best Buy or Walmart), but even this is just a transformer and a couple of capacitors as the charging setup. Since these units just up the voltage of the batteries, almost none of them will be wanting to provide a charge for a battery more than 10Ah.
Best bet for charging a camper van battery is the camper itself. Solar is a bit of a meme unless you have great daily sun exposure and consistently move less than once a week.
If you end up needing 120VAC for something, run a little inverter as-needed. Running an inverter just for the sake of running it will hit your battery.
High amp alternator, DC-DC charger, and a Lithium Iron Phosphate battery is where you wanna be for a camper van. With a Renogy 50 Amp DC-DC converter you can bring a 100ah battery (enough for 3 days off-grid) back to 100% full in less than 2 hours of run time. Advantage to the lithium batteries as they can charge at a much higher rate than any of the lead-acid options, significantly cutting down on "drive time till full".
In reply to bbbbRASS :
I could charge from the alternator, and it will be connected via a three-way solenoid (force on for jump start, always off to isolate, or on with oil pressure so it charges while running). I would of course charge it up ahead of time, but sometimes my M.O. is to disappear for a while. I do have a 40w solar array, but another one of my M.O.s is deep woods kinda camping. I'm lucky to see 5w on the meter from that set of panels when I'm in that much shade.
I figure if I run out of juice out there, oh well. I can either run the engine for a while or just tough it out. Also, a little backwards and oddly redundant, but I could take my wee generator.
93gsxturbo said:
Best bet for charging a camper van battery is the camper itself. Solar is a bit of a meme unless you have great daily sun exposure and consistently move less than once a week.
If you end up needing 120VAC for something, run a little inverter as-needed. Running an inverter just for the sake of running it will hit your battery.
High amp alternator, DC-DC charger, and a Lithium Iron Phosphate battery is where you wanna be for a camper van. With a Renogy 50 Amp DC-DC converter you can bring a 100ah battery (enough for 3 days off-grid) back to 100% full in less than 2 hours of run time. Advantage to the lithium batteries as they can charge at a much higher rate than any of the lead-acid options, significantly cutting down on "drive time till full".
I like that plan. I do have about 80Ah right now, so upping to 100 or 150 wouldn't be a stretch. One of the problems is that my 80Ah is in the form of a Jackery box that I'm not sure I want to hack, but it's an option.
Pete. (l33t FS) said:
The phone bank/server at a place I used to work was on a UPS. When the power would go out, the little batteries had a lifespan measured in minutes. That's fine for running a computer long enough to shut it down, but not good if you need the UPS for your business's phones to work.
We found that the UPS worked just fine when paralleled to the largest 12V batteries we had in stock
Yep little UPSes work fine with huge banks of marine batteries...as for what amperage you can expect, if you look up the model info the max output power will be listed but I'm not sure about charging power. They also work fine if the batteries are being DC-charged by something like a solar panel or wind turbine...or an alternator.
