Duff battery?

[Wh05apk]

We have a new van which has a 246ah gel battery pack, plenty powerful I would have thought, we are now using for the first time off why, and after 1 night of light use (3-4hrs) tv, the state if charge is showing 85%( about right?) But the voltage is down to 12.0 volts and the inverter will only run my wife's 900w hairdryer for about 10 seconds before cutting out due to low volts, this seems wrong to me , similar use in our last van would give 2-3 days before dropping below 12.3v.
On collection a month ago we stayed on ehu sites for 4 nights, then had it connected at home, since then we have driven about 150 miles a day, on arrival we are showing 100% and 12.7v once engine off and settled down.

 

[two]

Let’s keep the sums simple.
If you have a 250Ah battery bank at 12V, that’s 3kWh of power. But you should only take about half of that if you care about your batteries (= 1.5kWh). At home, that’s just over 20p’s worth of electricity (= not a lot).
What I’m trying to tell you is that, even with a relatively large habitation bank, it’s still a very finite amount of power.

The things that will drain batteries very quickly are those that involve heat, so try to avoid that as much as possible. Hair drying is considered “an emergency” in some motorhomes and may be a special exception, but the batteries won’t know that and will still take a hammering. Your inverter will be trying to protect your batteries, as you say. Your batteries may not be duff but watch their behaviour if you suspect as much. I’d take a look at your inverter connection from the batteries, especially if an aftermarket addition. The wires need to be thick (and preferably short) to avoid voltage drop.

If you watch TV a lot, buy a pack of cards or another TV which consumes as little power as possible. Try to determine what, in your lifestyle, is consuming that precious 1.5kWh and then manage that.

Enjoy your new toy!

 

[DavidG58]

might be worth using a multi meter directly on the batteries to confirm the voltage there, could be a controller mis read

I would expect charged batteries to maintain closer to 13V until used

Or have you maybe got something on all the time you don't know about? inverter? even not in use will drain something

 

[Wh05apk]

Inverter is switched off.

Appreciate even 250ah of batteries are negligible in terms of domestic use, my concern is that after 1 night of moderate use the voltage is down to 12v which is then setting off the low voltage alarm, similar use in our previous van (with less battery pack) would easily last2-3 days without significant drop.
My concern is the van had been standing for 13 months before we purchased, and I am concerned the battery pack was not cared for well.

 

[two]

I understand your concerns.
Can you check to see that there is no drain when everything's 'off'?
A good way to test capacity is to run something continuously and see how the battery performs over time. Most easily done if your control unit tells you what the draw is. I'd try to keep the drain low and check every few hours. That way you can measure (to an extent) the number of Ah supplied by the battery over time and the terminal voltage at each stage.
All the better if you can get a clamp meter around the wires. = To check for unknown consumption and then to measure capacity. I assume that your van does not have a battery monitor/Ah counter.

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[pappajohn]

My concern is the van had been standing for 13 months before we purchased, and I am concerned the battery pack was not cared for well.

Think you answered your own question.

At the moment I have an old starter battery on my new bench smart charger.
Been on slow charge for around 3 weeks and It's showing fully charged at 12.7v (rested, off charge) but the charge percentage is just 60%.

I know the battery is knackered but just playing with the charger trying to figure out the auto desulfation mode.