Batteries?

[Pete-B]

Hi all,

 

On my previous van - Bessie 460 - I had two 90ah leisure batteries and also a 100w solar panel with battery master fitted in order to keep the engine battery charged. Whilst the van was in storage I could go all through the winters, sometimes leaving it a month between run outs and would always find the batteries pretty well fully charged at all times.

 

I'm now waiting for my new van which comes with a single 100ah leisure battery. My question is, I'm going to have another 100w solar panel fitted with battery master, so to save money, would the single battery be enough to see me through the winter months.

 

Thanks for any advice.

[colin]

For using or storing?

How low did your twin battery set up drop to? From that you should know if a single battery will suit your needs.

A single battery and 85w panel meets our needs for 10 months of the year in UK, not sure of the other two months as we've not holidayed in the van then.

[Pete-B]

The reason I ask is for winter storage. The van is in a secure compound during the winter months which is about twenty miles away from home. I try to give it a run out every couple of weeks but that's not always possible so sometimes the gap is longer.

[colin]

Your set up should be fine, a 100w panel is way over specced to keep that topped up without use.

[Guest peter]

I'd read this before you use a battery master and other make of controller if you will have Schaudt electrical distribution box in your new van.

http://www.aandncaravanservices.co.uk/solar-power.php

[aandncaravan]

Thank you for the recommendation to view the web pages, but it doesn't just apply to Schaudt equipped vehicles.

It sounds like there was a single battery output Solar Regulator going directly to the Habitation battery with a device that 'steals' some of the Habitation Battery power to charge the Starter Battery?

A much better (more reliable, efficient and often cheaper) solution is to utilise a twin battery output Solar Regulator that will directly charge both batteries, yet treat them as completely independent battery banks?

 

The problem with the 'theft' method of your other MH is that the Starter battery can 'steal' power from the Habitation Battery regardless of the Habitation charge state. The devices work by 'watching' the Habitation battery voltage and if it rises above, say 13.5v, then it passes power to the Starter battery. Obviously the voltage the device 'sees' is not the actual voltage of the Habitation battery, which could be down at 10v, but the 14v being output by the Solar Regulator.

These power 'theft' devices also waste power by continually 'watching' the battery voltage, although it is low. it is still less efficient than other ways of configuring the Solar system.

A quality twin output Solar Regulator will give priority to the Habitation battery and charge the Starter battery much more efficiently as it can now use the ''excess' to boost the Starter battery, but only if it needs it.

 

As to whether a 100w panel will be enough, depends on where in the UK the MH is stored, the devices drawing power (like Frost protection valve, Alarm, Tracker, etc) the Battery age, efficiency, technology, etc. more than the Battery size.

There is a big difference between the output from a Solar Panel in June down in the South of France and one in Glasgow in December. In Winter in Oban the Solar day is very short, it is only just getting light at 08:30 and pitch Black by 15:30. The Sun won't be high enough to generate power until about 10:00, when you might get 1amp? The Sun will quickly drop and it will be all over by 14:00, giving an average output (in bright Sun) of about 4 hours x 1 amp or 4Ah.

On a Cloudy day you will be lucky to get 2Ah. They are very small gains so absolute efficiency is key.

 

If you look at our Solar Page you will see just how big a difference there is between Cornwall and Scotland, potentially making the advice of another Motorhome owner in one part of the country completely irrelevant to your location/use.

 

The quality and efficiency of the batteries, far more important than the size?.

Obviously a Budget Battery that is one year old will lose power far more quickly than a quality, high Technology battery of the same age.

We don't sell batteries so this is not a sales pitch, but a Varta Silver Dynamic battery does not self discharge. An isolated one will stay above 12.5v even after 4 months (obviously provided there is no power draw whatever). An ordinary low technology Leisure Battery could be down to 10v in the same period.

It does not take a genius to work out that a budget leisure battery will require a lot more Amp Hours to keep topped up than our recommend battery. If the battery is already 3 years old it may need 50% more Solar Power than a young battery.

 

Please consider that unless you have an Alternator, mains charger and Solar Regulator all with AGM specific battery charge programs, an AGM battery will not be optimally charged. As a result the battery may start off with less 'real' Amp hours than you might expect. Typically a 100Ah AGM in a motorhome environment will get no more than 90% charged. As a result the battery life will be shortened. In a worst case, in some Motorhomes, an AGM batteries life can be as short as 6 months.

 

We would recommend that AGM and Gel batteries are avoided, as there are more efficient technologies available that work much better with Solar Power, at half the cost.