Model Boat Mayhem

Technical, Techniques, Hints, and Tips => Batteries & Chargers => Topic started by: justboatonic on March 11, 2010, 02:25:06 PM

Title: Charging SLA's in the boat.
Post by: justboatonic on March 11, 2010, 02:25:06 PM
I've heard that batteries shouldnt be charged in the boat due to a possible build up of gasses that could lead to a minor explosion!? But, with current modern new SLA batteries, is this still an issue?

I need to have 2 SLA batteries in the MSW Envoy tug. Im toying with either having each battery sit almost alongside the motor ie just aft of midships so less ballast towards the stern is needed or, having the batteries side by side on a sliding base, just in front of the motor so I can hopefully get at them easily and remove them from the boat for charging.

Now, the hull is quite cavernous and easily able to take these of the size I intend using, (approx 134 mm long and 60 mm wide) but, when they are wired up in series to give a 24v supply and one battery also providing 12v for the motor, that's a bit of wiring to undo before you start pulling the batteries out of the hull.

Soooo, I was thinking of wiring them up and charging in situ. Is this a goer or, should I forget it altogether?
Title: Re: Charging SLA's in the boat.
Post by: Shipmate60 on March 11, 2010, 02:32:02 PM
The problem with charging SLA batteries is that they CAN vent off hydrogen gas.
This will only happen if there is a problem which allows pressurisation of the case and forces the vent open.
One problem of charging in the model is that you don't always see any problem when it isn't serious, so it gets worse.
You will no doubt hear that "I have charged SLA's in my model for years without a problem" and it will be true.
But 1 problem COULD have drastic consequences.
The choice is yours!!

Title: Re: Charging SLA's in the boat.
Post by: malcolmfrary on March 11, 2010, 02:36:53 PM
There is an element of belt and braces.  There might be some venting, and what is vented will be explosive.  The problem was noted by the submarine lads who tend to use sealed boxes, so any bent products stayed around.  A normal boat with a moderate amount of ventilation will allow any hydrogen to escape due upwards.  Early SLAs tended not to be as well sealed, and could allow acidic fumes to escape, which is why the use of automotive batteries is discouraged.  Acid tends to eat the metal bits, such as wire.
So, charging in situ should be OK as long as its ventilated and a gentle charger is used.
Title: Re: Charging SLA's in the boat.
Post by: justboatonic on March 11, 2010, 02:48:11 PM
Thanks both  :-))