Deep Cycle 12V Batteries

I looked at batteries recently for powering my trailer winch, the thing that struck me was the discrepancies in weight for batteries which were supposed to be of a similar capacity. The supplier eventually admitted to me that most deep cycle batteries where no more than high quality car batteries.

Sorry for the delay in replying to some of the questions but my tardiness is down to having to fit new blinds at the Dragon-in-laws flat.

Peter, yes the batteries are connected in parallel – not ideal but to get the required capacity with the available space I have had to use three group 24 batteries.

The fridge consumes about 3A and the load cycle is about 33%. This equates to about 24Ahr/day. I have a clever meter that monitors Ahrs consumed and voltage. When the loads are not drawing there is no current flow from the batteries. The electrical system has been checked out and found to be satisfactory.

Neil, yes, traction are the preferred type but space prevents – along with the financial justification.

I try never to discharge more than 50Ahrs before recharging (less than 25% of the 240Ahr battery capacity) or let the voltage drop below 12.2V. The engine alternator has a three stage Sterling controller although it is sometimes not possible to charge the batteries back to 100% capacity due to time constraints.

Ian – I have not come across DC-DC chargers – what are these?

I have spoken to Charles Sterling and have read his article on the best types of batteries for service batteries on boats – I agree with his comments. He is also of the view that the benefit of AGM and gel batteries do not justify the additional cost for the type of use that most boat batteries endure.

I suspect the poor results I have experienced with my current batteries are due to the amount of time spent at anchor, repeatedly charging using the engine (albeit with a smart alternator controller) to a less than 100% full charge and the cumulative effects on sulphation of the battery plates.

Which is why I created this thread to ask if anyone had any experience of deep cycle batteries and could make any suggestions (usual caveats apply) regarding a good compromise regarding price and deep cycling performance.

Steve

A dc - dc charger is the same as what sterling list as a battery to battery charger they basically boost the 9 - 12v input up to 14.4 v to power,an internal smart charger , you can use another battery or solar to power them and they are usually hooked up so they also draw their power from the main start battery system so once the motor is running the alternator supplies the power for it .

It appears that your alternator controller does a similar thing but you need to be carefull of how long the cable from the alt controller to your fridge battery is and what cross secton it is as long thin cables = voltage drop , a dc - dc charger is mounted right next to the fridge battery so there is no or minimal voltage loss between the charger and the battery .

Maybe you could hook up a multi meter on your battery and check the charging voltage just to ensure you are actually charging them fully .

Do you check the electrolyte level often ? It doesn't take much of a drop in fluid to weaken a battery .

Ian.

Steve,

Sounds like your doing most things right, presume you mean 24Ahr/day = 24hrs, and dont think there is an issue with sulphation from the voltages shown.

Presume the fridge cannot run on gas otherwise you would have already done this, and is solar an option to help out?

Peter

Ian, The battery usage and voltmeter (which is directly connected to the battery terminals) has been checked with a calibrated voltmeter. Unless I had a big Li rechargeable battery the DC-DC would not benefit a great deal and if I had a big Li battery I would be using it as the service battery.

The old batteries were sealed units so I may have cooked them. I will be replacing them with refillable flooded lead acid.

Peter,the fridge is quite efficient but has a front opening door which is a damned nuisance as all the cold air escapes when taking anything out of the fridge. The fridge cannot run on gas and if I could I would like to replace the gas cooker with a diesel powered one as LPG on a boat is dodgy in my opinion (I used to be registered with Corgi/Gas Safe).

I do have a solar panel but it is a pain to set up and only delivers about 1A in bright sunshine.

I am looking to using two smaller solar panels and would appreciate any advice on them - am looking at about 0.6 x 0.6m units with a max rating of 50W each. I have a PWM solar controller.

Edited By Steve Skelton 1 on 05/07/2017 11:55:19