Can I maintain 2 leisure batteries with 1 charger?

[Watchman]

I have been given 2 leisure batteries. I already have a good Numax leisure battery charger. I intend to use these batteries in parallel for greater duration when away from a mains source. Will the charger maintain them both or will an imbalance between their relative levels of charge start to build up?

Secondly, I am aware that normal car batteries die and can never be charged again if you discharge them too "deeply". I also know leisure batteries can be deep cycled but is there a limit? Can you kill them by discharging them too far or leaving them discharged for too long?

Thanks.

[MarshPhantom]

We have a Numax charger and twin leisure batteries, seems to work fine.

Yes, you will kill leisure batts if they get too uncharged.

[clockworks]

If the batteries are in parallel, they will balance each other. I think it's a good idea to have them separately fused, though.

[Watchman]

MarshPhantom said:

Yes, you will kill leisure batts if they get too uncharged.

Do you know how to detect a safe limit? With a car battery, the extended towbar electrics provide for a positive feed from the car even if the engine is off but it cuts the power once the voltage drops to a safe level, leaving enough juice in the battery to still start the car.

I have an "intelligent" relay from one of these circuits but I imagine the safe level will be too safe for leisure batteries - I wouldn't benefit from their deep discharge capabilities. I would see if I could adjust this or make my own if I knew what to set it to.

Or maybe... Mmm... Off to Google for a leisure battery protection circuit.

Thanks to you both.

[MarshPhantom]

Watchman said:

Do you know how to detect a safe limit? With a car battery, the extended towbar electrics provide for a positive feed from the car even if the engine is off but it cuts the power once the voltage drops to a safe level, leaving enough juice in the battery to still start the car.

I have an "intelligent" relay from one of these circuits but I imagine the safe level will be too safe for leisure batteries - I wouldn't benefit from their deep discharge capabilities. I would see if I could adjust this or make my own if I knew what to set it to.

Or maybe... Mmm... Off to Google for a leisure battery protection circuit.

Thanks to you both.

I read somewhere that you shouldn't let them get less than three quarters charged.

[Watchman]

MarshPhantom said:

I read somewhere that you shouldn't let them get less than three quarters charged.

I believe they should be able to discharge further than that. A normal car battery "dies" at 66%. It should be far lower for a leisure battery.

I'll see what Google says.

Thanks again.

[Watchman]

Interesting. From here:

http://www.waudbys.co.uk/howto/2/

They say:

website said:

USE A LEISURE BATTERY CHARGER. A leisure battery is different to a standard car one as they charge and distribute power differently and has to be charged accordingly. Put the battery on a bench charge for 48 hours to ensure full capacity. 12.7 volts indicates a full battery, 12.3 volts is half full and a reading of 11.8 volts means it is fully discharged.

Elsewhere I read that you can fully discharge them but I would like to find more (and more "official") sources of this info.

[Watchman]

Recommendation is NOT to let it fully discharge - max 50%.

Here:

http://www.batteriesuk.uk.com/news/1

[Watchman]

I probably could have found an answer to my second question if I'd tried:

http://www.advancedbatterysupplies.co.uk/press49di...

[robpearson]

It's worth checking the Amp Hour ratings of the batteries and the charger. There's usually a maximum AH rating on the charger for fully charging, and a higher figure for maintenance charging. if you're over about 200AH of batteries your charger might not be sufficient, especially if as pointed out it's for a car charger as car batteries are often below 100AH. I have 300ah of batteries, and have one of these: http://www.ctekchargers.co.uk/ctek-mxs-25.php

[Watchman]

The advice I gleaned from one of those links I gave was that if your charger was smaller than optimal, you run it to longer to achieve a full charge.

I have 220Ah of batteries now with a 10A charger. It ought to do.