Charging and plugging in question

medicfernando · 03-08-2015, 10:04 PM

I am wondering what the best thing to do when the SMB sits for a couple of weeks. Is it best to keep it plugged to shoreline power all the time? How about keeping it plugged in with the charger enabled? Or, just plug it in every couple of weeks for a few days to keep the battery charged. Any suggestions would be welcome. Thanks in advance.

photographix · 03-09-2015, 12:30 AM

Plugging in to shore power all the time should keep your batteries tip-top. If you have an inverter/charger (Power-verter is what TrippLite calls them), it should manage the care and feeding of your batteries.

If you can only plug in sometimes, try to do it every few days and leave it hooked up overnight.

If you have a solar setup with a decent controller, you probably never have to plug in.

If you have to let it sit for several days, pull the fuse for the CO and Propane Leak detectors. That will save some draw on the battery.

**daveb** · 03-09-2015, 02:59 PM

I've beat this to death and I'm not saying I'm right or wrong. You'll have to make your own determination.
IMO the inverter/charger should be set up to only supply a limited charge rate for long term charging unless you monitor the charge daily. My inverter supplies a maintenance charge if the charge button is in the off position. Because of the low amp rate, I feel safe plugged in whenever it's on the driveway for long periods in time but I drive my van weekly and watch for any odd changes in operation. If I were to put the van in storage I'd look into battery isolation switches and maintenance chargers. JMO
Most smart chargers (which is a poor name to call them) work well unless something goes wrong. If a battery fails the charger will ramp up to maximum and boil the bad battery. That's not good for the other batteries in the loop but the big problem is the battery starts off gassing, which can lead to an explosion or possibly a fire. I've never had a fire or explosion but when it happened to me the battery spewed its contents and became so hot I couldn't touch it. This was found the next morning after I started the normal smart charge. Left for another day I might have returned to a burned up vehicle. There were red flags that I missed. My separator was opening up at a different rate (quicker than normal once the charge was stopped), the charge rate was much higher on the amp gauge (like the battery was dropping to a lower state than normal), and I was seeing the engine crank over a bit different. This was all due to one of the starting batteries failing. Unfortunately back then SMB configured the house battery to always help start the engine. This helped mask the problem.

So I'd look at the charger setting and see if you can limit the charge rate. Maintenance chargers rarely put out more than a few amps. It's the high amps that can pose a problem if left unattended. That's why solar is so nice.

At the other end of the spectrum, if the charger is set to a low output and you leave something on that pulls more than the chargers output, you'll risk killing the batteries. The separator protects both battery systems from each other but the inverter charger is hooked to the house side in most circumstances. A 2A charge + a 4 amp draw off the house system equals a dead house battery if not caught quickly enough even though the charger is working. So you should still monitor the charge as batteries can be expensive.

Kind of a catch-22.

My advise is to set up a maintenance charge & monitor the charge weekly. If it can't be set to a low amp setting, let the smart charger do its thing but monitor often watching the amp level. It usually will taper down to an amp or so w/i a day. If it continues to show a higher rate, something is wrong and you should find out why it's happening. It's fine to go 2 weeks before applying a 24 hour charge provided all the batteries are in good shape and you don't leave something on. Like mentioned, the CO and propane detectors can pull down the battery reserves and you want to avoid cycling the batteries. It's easy to leave on a light or the radio switch. Even some separators pull amperage. Some builds have a master switch that kills anything on the coach side for this reason. AGM batteries can go for a month w/o requiring a charge provided there is no draw. Again a small solar panel is a great way to go if you have the sun. The only reason I plug in on the driveway is I keep my refrigerator on 24-7 and I don't want to cycle the batteries down on a daily basis at night when the sun isn't producing solar power.
Chances of what happened to me are rare but IMO batteries are cheaper than vans.
Oh, BTW, did I mention you should always monitor the charge?