I was reviewing my 12V UPS schematic, when it occurred to me, how safe is it to just leave a camper converter/charger plugged in? I don't know much about them I guess. are they float/maintainer chargers? I can get the details off the converter/charger later if needed, but my question was more in general.
If they are safe, would I be better off with a maintenance free battery, than my huge camper battery?
all I know off hand is it is a 40A converter/charger from a 1988 camper.
I have attached a schematic of my UPS project for reference. (Generic 12V UPS_schem.jpg)
If the charger/converter is safe to leave plugged in, I could eliminate the Arduino charge controller and simplify the project quite a bit. (Simple 12V UPS_schem.jpg)
This would free up an Arduino for other projects.
travis_farmer:
If they are safe, would I be better off with a maintenance free battery, than my huge camper battery?
ain't they both lead acid? except that one is sealed and the other is not? and how is that maintenance free battery smaller than your camper battery? unless it is of a smaller capacity?
1000CCA means it's supposed to be capable of supplying "1000 Cold Crank Amps" to a starter motor. It means nothing in respect to Ah which is what you really need to know if you want to estimate its endurance.
a competently designed camper PSU will limit the voltage supplied to less than that which causes gassing - so should be fine to leave permanently on. Just as a modern car alternator never causes gassing unless it's faulty.
the service batteries are of a different design to starter ones - meant to handle slow deep discharge - not short sharp peaks.. and are not interchangeable
How old is the charger?
Most modern chargers for charging lead acid batteries are 3 stage chargers which have a microprocessor in them
to control the charging rate , so that gassing doesnt occur.
You can safely leave the battery connected to the charger all the time if its a smart one.
By "plugged in constantly" do you mean while charging the battery from an AC source? or while idle? or when the battery is being used by appliances?
How old is the battery? if it's older than 6 or 7 years then it's time to replace your battery anyway.
travis_farmer:
last I checked, maint-free batteries are more expensive, so I wouldn't be able to afford as big a battery. the one I have I think is around 1000CCA (don't remember the Ah rating), and is a deep-cycle. In other words, is it worth upgrading the battery, or keep what I have? keep in mind, the battery is not vented to the outside, so this is my other reason for upgrading.
SMF batteries are designed to be used indoors so that they don't leak lead fumes which are harmful to humans + you are saved from the trouble of always checking the water levels. And as a drawback they have fewer charge cycles (life span) than the regular ones and you don't get any money when you scrap it.
I've replaced my car 48Ah battery with a SMF one same capacity and it works pretty well so far, it's been 3 years since.
Deep cycle batteries are especially designed for use with devices like UPS/inverters where they get regularly deeply discharged using most of its capacity. Deep Cycle batteries have specially designed thick plates to withstand frequent charging and discharging.
So basically the battery you have is a good choice. Please note that do not replace it with regular automotive batteries which are not designed to be discharged to more than 25% of their capacity regularly.
For my home inverter I use Tubular batteries since they are efficient and have a very long lifespan. But they are very big and very heavy.
If you have any plans to replace your battery, you should go for true deep cycle batteries. If you have any infants or kids onbooard + poor venting for battery compartment, then only go for SMF.
travis_farmer:
Plugged in while idle, and while being used. I have seen campers being plugged in for months at a time. I am just wondering if this is alright for the battery.
That depends on your inverter. The modern ones have a cut off feature which ensures safe battery protection.
I do not know about yours, I'm not expert enough to find that out from your circuit diagram.
If you have a brand/model number then we can find that out from its datasheet.
travis_farmer:
it is getting close, 4 or 5 years old.
Then I guess your deep cycle battery is quite healthy. You don't have to worry about buying a new one until this dies.
travis_farmer:
no infants or kids, but I am now leaning toward SMF as the battery is indoor.
If you really want to replace it then go for the deep cycle variant of SMF. The regular automotive SMF batteries are not designed to be used with inverter UPS systems and will fail real soon if you regularly discharge it beyond its small rating.
They also come in good but costly AGM and GEL variants.
Also if that battery is the only battery in your camper, then you must buy a dual purpose SMF battery, so it can be used to start the engine as well.
travis_farmer:
it isn't an inverter, it is a converter/charger. it both charges the battery, and provides 40A of DC for the 12V circuits in a camper. I can post the model number later today as I am about to get ready for work.
It doesn't matter since they both have the same charging function. In your case the output is DC, other than that, both are same when it comes to core function.
travis_farmer:
it, and my converter/charger is not in my camper anymore. I scraped out the camper, and I am using the battery and the converter/charger in my workshop to power my circuits, and especially my security alarm project with clean un-interruptible power (yes, I am using 5V regulators).
If your project is small or draws very little current then you don't need a behemoth battery. A regular small computer UPS SMF battery will do. + you can use a small , cheap solar charge controller which is very safe for such batteries.
Good, you can connect a wall wart (15v laptop charger) into the solar charge controller's solar input terminal to safely charge your batteries as well as use them at the same time. The charge controller has multi stage charge system that will protect your battery even when plugged in.
btw did you find out the make/model of your charger/converter?
Lead acid batteries are usually charged using a nominally constant voltage approach, that is, a constant voltage of 2.25 to 2.3 volts per cell (hence 13.5 to 13.8 volts for a 6 cell 12 volt battery). When they are fully charged they "float" at that voltage without the constant voltage charger changing anything.
The only concern I have about your scenario is that your charger has the capacity to supply up to 40 amps, so a small capacity battery that is nearly fully discharged might initially be charged at a very high rate relative to its design limits.
