battery box advice

[graham.hobart (Graham stevens)]

Greetings, I am looking for advice about housing my deep cycle marine battery so I can keep it outside till I get the obs. Looking to minimise condensation and cold, though realistically I know will get these. At the moment its stored in my car!
Graz

[Marke (Mark)]

I just got a big plastic box with lid from bunnings to store it in .

[MrB (Simon)]

If it ever gets below zero it may not be a good idea to store the battery outside as the electrolyte may freeze, expand and damage the plates.
I doubt even an insulated box would be adequate protection in sub zero temps.

[Astro_Bot]

Actually, it has to get pretty darn cold for a lead acid battery to freeze - it's not water, it's acid. That's why cars can sit outside in sub-zero temps and not burst their batteries.

Can my batteries freeze?

If your battery is partially discharged, the electrolyte in a lead acid battery may freeze. At a 40% state of charge, electrolyte will freeze if the temperature drops to approximately -16 degrees F (-26 deg C). When a battery is fully charged the electrolyte will not freeze until the temperature drops to approximately -92 degrees F (-68 deg C).

I added the Celsius conversions.

http://www.progressivedyn.com/battery_basics.html (That's one source, but there are others that say essentially the same thing).

It's good advice to keep your battery fully charged to avoid premature sulfation, so it shouldn't be sitting around in a discharged state.

[MrB (Simon)]

Originally Posted by Astro_Bot

it has to get pretty darn cold for a lead acid battery to freeze - it's not water, it's acid.

Duh lol. Cheers RG.
Not thinking before posting, I am an idiot sometimes
I need a coffee...

[graham.hobart (Graham stevens)]

the K & D box thing I think will do for now, just bought one for another thing and thought of that-wanted to check whether leaving it out is detrimental.
Is there a place I can by a digital readout meter that will tell me how many amps are left etc?
So I can monitor the battery charge-thinking something I can leave attached and not a multi meter.
Graz

[Astro_Bot]

Originally Posted by MrB

I need a coffee...

I second that .... kettle on!

Graham, you probably already know, but when storing a battery, you should periodically re-charge it - I would suggest at least monthly. Lead acid batteries self-discharge at about 4% per week (although that will vary depending on temperature and construction). When you get your obs set up and battery installed, you can safely leave the battery on trickle charge 24/7, which will maximise battery life. If you don't have power in the obs, re-charge after every use.

Even if only re-charging monthly (while stored), charge shouldn't fall below 80%, so the freezing point shouldn't be higher than about -40 deg C.

Edit: Just saw your last post. Don't know about a digital readout - I've never used one, though my battery box (portable version) has a built-in LED indicator - pretty coarse but maybe useful. A multimeter can still be useful, though. This link has a table of voltage vs charge state for lead acid battery types, but beware that you need to take into account any terminal or instrument resistance, so adjust based on your readings when fully charged:

http://www.energymatters.com.au/rene...-discharge.php

[mikerr (Michael)]

Graham, something like this mounted permanently on your battery box might do.

http://www.jaycar.com.au/productView.asp?ID=QP5586

Michael

[acropolite (Phil)]

Is there a place I can by a digital readout meter that will tell me how many amps are left etc?

Graham, keep the battery charged, forget "how much is left", batteries sulphate the moment any charge is taken, sulphation is the chemical process resulting from discharge, if the battery is left in a sulphated condition for any significant time, the lead sulphate hardens irreversably and the ability of the battery to store charge is diminished or destroyed if left too long.

That's why you should recharge any lead acid based battery immediately after use. Leaving the battery in a partially discharged state is asking for trouble.

If you're wanting to monitor your usage with a simple voltmeter, as a rule of thumb when the battery voltage reaches 12 volts (no load) it's around 50% discharged. Full discharge is around 11.5 Volts. If you want to measure Amp hours in / out there are specialised meters made for that purpose, they either need an external shunt or may come with shunt inbuilt. This unit will read voltage, current draw and AH used. http://www.jaycar.com.au/productView.asp?ID=MS6170

[Marke (Mark)]

The digital volt/A dual display meter I put on the battery in my obs cost $14 off ebay including postage , its a little bulky but has nice red led readout.

[Garbz (Chris)]

Worth mentioning is that if you're going to use a voltage readout to determine when your battery is dead you should lookup the datasheet for that make and model on the internet. Different battery brands and types have different points where the manufacturer deems it "empty" and you shouldn't continue to discharge beyond, normally around 11.8V. Even deep cycle batteries can get damaged by over discharging though the point is typically around 10.5V or so.

I also use a dual volt/A display meter from ebay. http://www.ebay.com.au/itm/20V-20ADC...item1c29453a19