Leisure battery

sjfoley

Hi , I like to keep a dehumidifier in my van over winter, preferable plugged in all the time but set fairly low, however I imagine this had the possibly of overcharging the leisure battery, I've tried knocking off the switch in the electro block but this doesn’t seem to isolate the battery. Any ideas, apart from disconnecting the battery which is a bit of a pain! or perhaps putting the whole thing on a timer, which isn't ideal for the dehumidifier.

crabbypaddy

sjfoley wrote: »

Hi , I like to keep a dehumidifier in my van over winter, preferable plugged in all the time but set fairly low, however I imagine this had the possibly of overcharging the leisure battery, I've tried knocking off the switch in the electro block but this doesn’t seem to isolate the battery. Any ideas, apart from disconnecting the battery which is a bit of a pain! or perhaps putting the whole thing on a timer, which isn't ideal for the dehumidifier.

Run an extension lead? You definitely do not need a dehumidfier all winter we use ours every couple of months and its sufficient. However if you want to go that route get one with a humidistat. Bear in mind that a compressor dehumidifiers are really inefficient at low temperatures as it will have to defrost constantly.

Does the switch turn the charger off?

I'm highly dubious that an electrobloc can overcharge a battery.
If you measure the current on float and it zeros out with no load after a few days then it's fine.
Or fit a battery isolator.
Or disconnect all chargers and loads.
Or get a charger that's designed for float service.

nailer8

I leave my van plugged in all winter with a dehumidifier left in the van switched on and plugged in.
I then have a 7 day timer on the socket so the van gets power twice a week for c.3h each time.
This keeps the batteries charged without overcharging them and gives the dehumidifier a shot for a few hours per week.
seems to work fine, biggest problem is i forget to empty the dehumidifier and i cant seem to get it to drain through a pipe into the shower.

crabbypaddy

nailer8 wrote: »

biggest problem is i forget to empty the dehumidifier and i cant seem to get it to drain through a pipe into the shower.

Some of them have a black rubber plug inside the hose spigot after you remove the cap my friend and I both missed it. Also probably obvious but the hose spigot must be the highest point in the drain system so if the hose is going upward to enter the shower you may need to raise the dehumidifier.

nailer8

Yea. Mine has a knob which had a rubber plug behind it.
I made a hole in the plug to take a 8mm plastic pipe (truck air line pipe) and fed it straight down to the shower (put the dehumidifier into the shower actually).
The tank still filled up though and it cut out once the tank was full.
Must examine it further.

Overcharging batteries is pushing excess current through them after the specific gravity has reached 1.275 (or after it has ceased to improve on an aged sulphated battery). It's very, very, very difficult to do with a stock charger as they're designed to always be tethered.
It takes me about two weeks solid to get the last 5-10% into my electron pots with PV and a customised charger, about 4 days to do it with mains derived constant current and 15.1V because most my chargers are too conservative.
I can do it in 3 days with 15.6V cycles but there's no need to be that aggressive.

Normal run of the mill charge cycles where the charger tells me it's "finished" after a single charge cycle my batteries are about 90-95% according to the electrolyte density. Now say I had a fairly bog standard dumb charger (and the self-proclaimed intelligent ones that I've tested with their low float settings are worse tbh) that floats at 300mA and 13.6V, that temperature wasn't an issue, I didn't have any parasitic load or these were compensated for, my batteries were 100% efficient and had zero internal resistance. Then the 4W that charger was pushing would take 2 to 3 days to finish charging my 235Ah battery. After that it'd gas a little and I'd come along in about year and stick some more water into it.

Having said that cheapo automotive chargers can be harmful.

The only easy answer I can offer is solar PV and a Morningstar controller. I'm testing a ProStar at the moment on a fatigued AGM. So far looks pretty promising but the glass mat keeps getting stuck in my hydrometer so it's a little hard to judge.
Funnily enough I've noticed when a TriStar controller goes to float the display on it's otherwise accurate ammeter says 0A while an independent meter reads 300mA for days before true 0. I'd put pennies to pounds it's a peace of mind feature.