Should I disconnect the aux battery before charging.

[mjr350]

Hi Guys
I have just been away for a few days and the Engel sucked away at my aux battery a fair bit with minimal charge in between for timber collecting etc and the drive home was only 50 minutes so not enough to bring the aux back to normal.
I want to hook it to a 240v charger over night but I'm not sure if I should disconnect the aux from the Redarc SBI12 or not. My thinking is no because its only sensing on the crank side but I'm just not 100% sure.

[the evil twin]

It is fine to hook up the mains charger to the aux if you are simply recharging.

If your charger has a reconditioning setting or desulphating mode then it is best to disconnect the battery.
It won't hurt anything but sometimes other circuits will fool the charger is all

I run the SBI12 dual sense so that no matter where the charging source is (solar, mains, alternator) it will charge all batteries.
That means if I want to target a specific battery I need to isolate it.

If your Redarc is a SBI12 and not a SBI12D and you connect the Charger to the Aux then you can charge the Aux battery in isolation
If you connect a Charger to the Cranker it will try and charge both as the SBI12 will close and interconnect the two batteries.

[Cuppa]

Good question to have asked. ET’s answer covers it. Might be worth considering some solar for the next trip away.

[mjr350]

Yea thanks guys. Ended up disconnecting to be safe but won't in the future. Silly me dropped the aux down to around 11.5v in the end and now its having issues charging at all. 2 smart chargers wouldn't look at it so I had to use an old school arlec and even though its supposedly fully charged, the sight glass is still saying recharge. Any thoughts as to whats going on.
Apparently dropping a deep cycle down to below a certain level can cause sulphates to form on the plates. Can this happen in one extended session on a 2 month old battery?
I've also had the fridge in the vehicle constantly for the last month but drive at least 40 mins most days and sometimes up to 2 hours for work but im thinking that the battery has slowly died over time due to not driving long enough. What do guys do who keep the fridge on constantly.

[happygu]

If you are running the fridge constantly, I would add a battery gauge, so you see what is happening before it runs the battery right down.

One discharge shouldn't hurt the battery too much, but constant flattening will kill the battery quickly

[mjr350]

If you are running the fridge constantly, I would add a battery gauge, so you see what is happening before it runs the battery right down.

One discharge shouldn't hurt the battery too much, but constant flattening will kill the battery quickly

I've got a gauge on the dash but the last night really dropped it down. Small drives to collect timber really didn't make much difference. I think I'll remove it for now and go back to an icebox for lunch and only use the engel for trips

[Winnie]

Can you charge the battery via mains when you get home? Or were you away from home the whole time?

[Cuppa]

Yea thanks guys. Ended up disconnecting to be safe but won't in the future. Silly me dropped the aux down to around 11.5v in the end and now its having issues charging at all. 2 smart chargers wouldn't look at it so I had to use an old school arlec and even though its supposedly fully charged, the sight glass is still saying recharge. Any thoughts as to whats going on.
Apparently dropping a deep cycle down to below a certain level can cause sulphates to form on the plates. Can this happen in one extended session on a 2 month old battery?
I've also had the fridge in the vehicle constantly for the last month but drive at least 40 mins most days and sometimes up to 2 hours for work but im thinking that the battery has slowly died over time due to not driving long enough. What do guys do who keep the fridge on constantly.

Getting down to 11.5v is not good, but it shouldn’t be disastrous. I’m surprised you had to resort to the ‘dumb’ charger. My smart charger will play ball with 11.5v. I think you are correct about not driving for long enough each day. For the fridge to run constantly you either have to drive long enough each day to fully recharge (unlikely unless you are touring), plug into the mains or add solar. Unless you are using the fridge it’s best to switch it off. If you are using it keeping it full will reduce power usage. With the battery only two months old I’d be taking it back to where you bought it & at least have them test it, if not replace it. It shouldn’t be cactus at such a young age even taking into consideration you treatment of it.

After checking fluid levels (if a wet battery - the plates are all covered - right? if not top up with distilled water & recharge) you could check it’s rested (sit for 30 minutes or longer not connected to anything) voltage after charging on the Arlec. If below 12.7v try sticking it back on a smart charger. If that doesn’t revive it, take it back.

[the evil twin]

What Cuppa said ^^^^

As a point of interest the "sight gauge" is not all that reliable an indicator of the charge level of a battery.

If you have a good smart charger with a "recon" mode then I would give that a try but if the battery is only a couple of months old I agree with Cuppa, take it back for a test and be a tad coy about your useage.

Dropping any battery below 95% or better SOC will allow sulphation to commence, well 100% actually but sulphation levels above 95% are low enough to be negligible.
Deep Cycle batteries are just designed to handle it a little better and for longer but they will kark it after a while as well.
If I have been away for a while I always wack my Aux or van batteries on charge when I get home.
I also put the Cranker on all my vehicles on a smart charger about every 2 months or so.

[mjr350]

Thanks for all the advice. I left the arlec on overnight for 2 nights and it seems that the battery has come back to life and holding charge. I did use the fridge most days for lunch and cold drinks but ill go back to the icebox and keep the fridge for trips away etc.

[Nightjar]

What do guys do who keep the fridge on constantly.

During trips away prospecting during cooler months I have a 64W Solar on roof of my coilcab connected through a regulator.
39L on freeze & 60L dual Engel connected to load which is regulated to cut out at 11.5V.
While driving the alternator also charges.
If the sun shines all day there is no extra charge requirements.
Cloud rolls in I have a 40amp charger to plug into the generator which I run for about 1 hour.
All good.

[mjr350]

Yea I've been looking at a folding 120w panel. The battery was obviously down before I left so I didn't got the most out of it anyway. Im thinking a good charge before I leave will keep me going next time. On the solar side of things, do I need a dual sensing isolator or can I just hook it to the auxiliary when im camped.