Charging Batteries Onboard

[pogo]

G'day All, Hope you all had a great christmas.

Getting organised to fit a MK bow mount onmy boat and am looking at batteries.

I'm in the fortunate position of being able to score a gel cell (Sonnenschein) to use as the power source for the MK. and pssibly another to use as a starting battery

Have got a batterry Isolator, (Charges second battery when first Battery exceeds 13.7 V

The question is will charging the gel cell, (Max charge Voltage 14.4) from the boat alternator end up destroying the Gell Cell battery. I think it will, based on the research I've done

Is there such a critter around that will limit the charge voltage to the gell cells or do I have to go down the route of tring to get the alternator on the motor (Mariner 125) changed or adjusted to limit its voltage.

Regards Pogo

[Bill S]

Hi Pogo

To answer the question, from what I've learnt. The rotary charger is the 'perfect' method to charge Sonnenschein gel-cell batteries. It will deliver maximum acceptable amps to the gel-cell and then reduce the charge as required. Which is fine if you can run the engine for the required time to recharge the battery.

My boat runs twin Sonnenshein A500's/115Amp to a RT74AP which are charged by a 3 bank Guest 2631-230 onboard charger. After the boat is washed down, the power lead is connected and turned on. Thats it . The charger services the gell-cells and the 'wet' crank/house batteries, charges them fully and keeps them topped up for the next trip.

I also run a Voltage Sensitive Relay between the house and crank batteries with an emergency parrallel switch, just in case.

The V.S.R. must be removed or bypassed from the circuit so it is not 'seen' by the charger as it will reduce the battery voltage sensed by the charger. This will cause the charger to increase its output and cook your battery. This is bad

My research showed we are limited in Aus by the lack of suitable (not ideal for the task) chargers. I imported what I considered the best of the bunch to suit my needs.

According to my research not recharging fully on the 'same day' of discharge is the biggest killer of gell-cells. To be blunt, charging from the outboard as you suggest will fit this description to a "T". The batteries can handle some variation in input voltage and amperage, but to under charge them is certain early death.

Follow the link for some information on Sonnenshein and Deka charging.

Cheers Bill

Edited December 31, 2004 by Bill S

[Mick]

If you charge you gell DC off your alternator you are going to shorten its life considerably. DC batteries, especially gell types hate quick discharge/recharge scenarios like an alternator will provide. Cranking batteries are designed to accept this type of treatment but DC batteries aren't.

The alternator will keep toping the battery up all day, although at the end of the day you may have a full battery, over time you will find the batteries capacity reduced. All DC batteries like a constant discharge and then a constant re-charge.

The guest charger Bill suggested is perfect for the job. If you get the Sonns for nothing I dont suppose it matters, but they are not a cheap battery and if I had them in my boat, they wouldn't be going any where near the alternator.

[pogo]

Thanks guys

That pretty much confirms my research,

The sonnenschiens wont be free, probably wholesale, from a mate in the battery game.

I get across to the states now and then so what I might do is track down a charger over there (West Marine Zantrex looks pretty good or find a Guest) and make this a bit of a long term project.

For the time being I'll head down the route of a AGM deep cycle to get me out on the water.

The problem I have at the moment is that the pogoboat lives streetside at a mates place. so onboard charging isnt really an option unfortunately.

I really want to get my MK fitted and turn the pogoboat into a stealthfighter. so Il make up a battery box that I can easily get the deep cycle in and out and run with that for the time being.

The eventual goal will be to fit Sonnenschien under the centre Console, but that will make access more difficult and require onboard charging.

Once again many thanks for the input

Regards Pogo

[Bill S]

Pogo

A simple solution to your current situation can be found in your local yellow pages.

Just look under solar power .

Cheers Bill