How can I find out if we need new leisure batteries?

[Diggerdi]

We have a 2017 Pilote P650GJ. Last week we were off grid for four days, two leisure batteries and solar. The weather was glorious for October, all day sunshine and reasonably warm. However, on the fourth day we realised during the late afternoon that the panel had shut down. I pressed the button and it came on again, no problems. Thought I'd probably pressed it by mistake when altering the heating. Later, on trying to light the hob, there was no spark. Tried the oven, no luck. Then realised we had no lights or water. TV was still on and the heating (I think!). The solar was showing 12.5v, so should have been OK. At this point it was just going dark, so I panicked as I didn't have a clue where to look for the problem. I went to see the steward (we were on a THS) and she came to have a look. She checked all the fuses which seemed to be ok and even tried new ones in, one at a time. Nothing. For some reason, I started scrolling through the panel and suddenly realised that the "aux", "pump" and "lights" were not lit up. I activated them all and everything was fine. I was so embarrassed but she was lovely about it. When it had gone off earlier, it had obviously switched these off. This was just after 5.00pm. I kept an eye on the battery level on the solar display and it seemed ok. We had TV on, heating and lights. At 10.00pm everything went off. We had to go to bed. Apologies if you've lasted this far. What I want to know is how can we find out if we need new batteries? They are the original ones so almost 5 years old. I don't want to shell out if it's just because of the time of year and using more power. In August we did 8 days off grid with no problems at all, but very little use of heating and lights on later. Please don't get too technical as batteries and solar is a mystery to me. Thank you

 

[Wildbill]

Go get them tested the test is the same for cranking battery's.
Another segestion convert all your lights to led surprising how much that will save you battery's
Bill

 

[Speve]

As above but from the sound of it once you discovered the problem the batteries had enough in them to do what you needed so I wouldn’t be to concerned or quick to change them

 

[denisejoe]

Also if you have a multi meter when it dark check the batteries with it as my panel was showing 12.4 but checking with multi meter batteries were at 12.8

 

[TheBig1]

The problem with relying on voltages alone can be deceptive. As lead acid batteries age, they lose capacity and what used to hold 100ah can be as little as 10ah after a few years of use. These batteries are rated by the number of charge cycles that they are capable of if you look closely at the adverts. So a battery that gets used quite often and frequently recharged will last less years of use than a lightly used one. Take it down to 50% charge or less regularly and it shortens the lifetime

So if you frequently camp off grid for days on end, using tv and some water heating, 4 years is about the best you can hope for

Testing is actually complicated, as engine starter batteries are tested by applying a resistance like a heater coil across the terminals for a few seconds, then measuring the drop in voltage. This does not test the capacity of a leisure battery though. Engine batteries have to be capable of starting an engine for a few seconds. The leisure battery needs testing with a smaller, known load of say 10amps, like a light bulb and test how long it takes to discharge

Understanding batteries is not really too complicated. Think of it as a tank of energy, like a water tank. It can be emptied fast or slowly. A 100 amp hour battery has about 50ah of usable capacity. So it can give 50 amps for 1 hour, 1 amp for 50 hours or anything between. If the battery capacity drops (gets sulphated) then you get less and less amps available to use. Your television will take maybe 3 or 4 amps. The heating can draw 8amps when first turned on. So you will rapidly use energy, "running down that tank". Depending on the size of your solar panels, in spring and late autumn you can often only see 3 amps charging that battery. The sun is also only up for a few good hours, so you will struggle to keep up with how much energy you use and the battery may never reach full charge without being plugged into the mains every few days.

This is a very simplified explanation and there is much more involved, but should help you understand a little

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[Guigsy]

At this time of year in the UK, even in the middle of the day, direct sunshine will only generate about half the panel's rated output because it's much lower in the sky. Combine that with far fewer hours of sunshine and you'll only be getting a 10-20 Ah per day. And next to nothing if it's cloudy. It really is hard to go off-grid this far north without a roof full of panels.

 

[Diggerdi]

Wildbill, the lights are all led, the van is only just over 4 1/2 years old. Thanks to everyone else's input also. I realise they won't cope as well during autumn/winter but I also know the batteries possibly only last 4-5 years. We've already decided there will be no off grid until the weather gets better and days get longer.

 

[Lenny HB]

You don't say how much solar you have, at this time of year you are going to need quite a lot to spend more than a few days off grid.
we are in Spain at the moment and with my 300 watts of solar not managed to get my batteries above 85% for a couple of weeks.

If you want to check your batteries you need to do a slow discharge test, if they have been treated well natural loss on capacity is around 2.5% per year.

First charge the battery fully and leave it to settle for an hour then:-

For example if it's a 100a/h battery load it with a 5 amp load and run for 5 hours, this will represent a 25% discharge. (adjust load/time to suit the size of the battery)
Disconnect the load and leave to stand for at least 30 min then measure the voltage.
Repeat the test and you will have discharged the battery to 50%.
You can repeat again then it will be 75% discharged.


Always best to test each battery individually if in any doubt.

 

[Lenny HB]

Go get them tested the test is the same for cranking battery's.
Another segestion convert all your lights to led surprising how much that will save you battery's
Bill

Totally meaningless for a leisure battery, only way to test them is with a slow discharge test.

 

[Diggerdi]

Lenny HB - that sounds very complicated for my little brain. We'll just make sure we only go on sites with hook-up if we go anywhere then see how we go on come spring.

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[Lenny HB]

What type of batteries are they?