Batteries

[Eifion]

Hello , very new and green to this , just completed my conversion , and very happy with it but having lots of problems with my batteries , I have just bought and fitted 2 yiasa 95 ah class batteries and my inverter alarm goes off after just a few hours , can someone tell me how much i can expect to get from such batteries , i run a small dometic fridge , some led lights ,a bt hub ,and an Amazon Alexa, I origi ally had 2 vartan 140 ah batteries but they were getting on and I was having the same problem which is why I bought new,any help regarding batteries and what I can run and for how long would be gratefully recieved ,many thanks .

 

[Figaro]

How are you charging them ?
The inverter and compressor fridge is a big drain I expect, but some techies will be along soon to advise

 

[Phill D]

hi and welcome.

 

[Eifion]

Hi Figaro, and thank you ,I'm totally useless where electrics are concerned so I'll keep my fingers crossed .

 

[Figaro]

Hi Figaro, and thank you ,I'm totally useless where electrics are concerned so I'll keep my fingers crossed .

Have you got solar or just electric hook up when home ?
It rather sounds like your battery drain is too much for the batteries.
Most advice on here is to fit as much solar as you can fit with a mppt controller.
You can also go for battery master and 12 volt DC to DC charger.
It probably comes down to how you use the van most, whether wilding or on campsites.
There are lots of knowledgable people on here who will be able to advise better than I can.

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[Spriddler]

You'll have to add together the current draw for each item to have a reasonably accurate answer as to how long the batteries will last when being discharged from fully charged down to say 11.6v absolute minimum.
Not all the items will be drawing current all the time so you'll have to work on a 'worst case' basis.

 

[GeoffnDee]

What type and model of Dometic fridge do you have fitted ?

 

[Eifion]

For the most part they are being charged direct from 240 from the house ,but I also have 2 200 watt solar panels and a split charger ,I just find it hard to believe that 2 brand new batteries would only last a few hours , i understand it depends what I use and how often but I was messing about under the van most of today and just a few hours after plugging into the inverter the alarm goes off ,I'm more than puzzled .

 

[Revolvor]

..........and just a few hours after plugging into the inverter the alarm goes off ,I'm more than puzzled .

What are you running off an Inverter? What output is it?

 

[gus-lopez]

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[mitzimad]

240 appliances use a lot of battery through an invertor also remember you only get to use 50%of your batteries capacity unless they are gel or lithium

 

[Jo662]

 

[pappajohn]

For every appliance using 230w (1 amp) at 230v it will be 20amps battery drain per hour via an inverter....plus up to 10% inverter inefficiency

 

[Eifion]

You mean you've got a donkey and you have attempted to stick your head up it ,very strange behaviour .

 

[Tombola]

You mean you've got a donkey and you have attempted to stick your head up it ,very strange behaviour .

HUh?

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[Eifion]

Looks like I may have replied to the wrong person , please accept my apologies .

 

[Revolvor]

You mean you've got a donkey and you have attempted to stick your head up it ,very strange behaviour .

Rule #1?

 

[autorouter]

From the description of your system so far, there's no particular reason why the batteries should be draining so quickly. Many people have two 100Ah batteries, 200W of solar and an inverter, which works perfectly well. However more info about your system and how you normally use it might shed some light.

What make/model of inverter is it? A high power inverter will probably have a relatively high extra power drain just to keep itself working, even with no load or a small load. Is the compressor fridge working off inverter (240V) or 12V? Is your BT Hub working off the inverter too?

The calculations are easy if you know a few basic facts. It's a bit confusing because energy is measured in two different ways. The proper energy units are watt-hours. For example a device running at 50W for 24 hours would use 50 x 24 = 1200 watt-hours. Or 1.2 kilowatt-hours.

The other way of measuring energy is popular with motorhomers is amp-hours (Ah). This actually measures the charge, not the energy. Remembering that the battery voltages in a motorhome are nearly always 12V, if you know the voltage just multiply the amp-hours by the voltage to get the watt-hours. So for example a 95Ah battery can store 12 x 95 = 1140 watt-hours.

If you want to know how much energy a device will take from the battery, when plugged into the inverter, look at its watts, not the volts or amps. It will take about the same watts out of the battery, plus about 10% for inefficiency. If you want to know the amps, just divide the watts by 12V. Multiply the amps by the hours of use to get the amp-hours.

It's very tempting to get an inverter that's big enough for everything you'll ever be likely to need - 2kW or 3kW for example. However these big inverters are best used for appliances thast use energy is short bursts, like a microwave or a coffee machine, then switched off to avoid the no-load drain.

If you have devices like a fridge or BT Hub that is powered 24/7, I'd consider getting another small inverter, just big enough to do the job. For example a 300W, or even a 150W. The background drain will be much lower, especially if you get a more up-market unit like a Victron or Studer.

 

[GeoffnDee]

Are you trying to run a Dometic 3 x way Absorption fridge on 12v / 240v with your van conversion instead of a Compressor type , if so , the batteries will drain very quickly.

 

[Eifion]

Thank you for this information it's very helpful and very good of you to take the time to explain , I'm new to this and I find electrics very confusing, I will try to take this info and make as much use of it as possible ,the inverter I'm using is clearly to big it's a 4000 watt beast so that will be the first thing to get rid of I rarely use it anyway ,thanks again for your help .