Bit of a conundrum (1 Viewer)

[DerryW]

For some unexplained reason we seen to be spending more nights off grid than on sites of late. That’s not the issue though. When off grid Mrs W still likes to watch her favourite soap, I don’t complain because I like to catch up on the news at least once a day, this leads to the issue. After 2-3 hours we get the “low power” notice pop up on the screen and a few minutes later we loose power to the TV, and the control panel shows 12volts 70%. We don’t loose all the 12volt power as the 3way fridge continues running on gas and still needs some 12volt power.

Over the last 2 days I have checked the battery (4 years old) using a multi meter and the proven lamp test (12v 5w bulb) and all appears fine (see list below).

The TV is an Avtec Pro 22.5 screen which uses 3-4amps.

The strange thing is when we get up in the morning the control panel reads 12+ volts and 100% even on overcast weather. So wouldn’t have thought a single 120w solar panel could put that much charge back in the leisure battery overnight.

I wonder if any of the Funsters with an electrical persuasion could share some light on what might be causing the 12volt power to shut down with just the TV on.

Our previous MH had 2 leisure batteries and we can’t remember having the same issue in the 2.5 years we had the MH.

So maybe it’s a simple case of adding another leisure battery, with the added loss of 30kgs of payload which we can ill afford to loose.

Thanking you in anticipation.
Derry

 

[Phill D]

12 v at rest is more like 45 - 48% charged!

 

[Phill D]

12.7v is around the normal fully charged voltage.
What AH is the leisure battery?

 

[Phill D]

Those voltage readings on your chart must be when you are getting some form of charge from your solar.
What voltage is reading when the TV says it’s low voltage.

 

[Itsmcb]

I think you need a bigger bulb, maybe a 60w headlight bulb, and keep it on for longer to check the capacity. You also need to disconnect all other inputs and outputs from the battery whilst running the ttest

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[poppycamper]

We had the same issues when on a lead battery... voltage would drop and tv ( also an Avtex) did not like it..
Main reason we went fir lithium battery... since then absolutely no issues.. tv still works right down until battery nearly empty....

 

[Itsmcb]

Lenny HB's test instructions Post number #41

I’ve often wondered why Lenny hates AGM batteries?

AGM batteries were, I am sure, around a lot earlier than stop-start vehicles. They have been used as Leisure Batteries longer than stop-start vehicles as well I have no doubt and are perfectly fine for that purpose. I bow to all on here who know far more about batteries than I do and you have...

www.motorhomefun.co.uk

 

[DerryW]

12.7v is around the normal fully charged voltage.
What AH is the leisure battery?

Phil. Thanks. It’s 110AH

 

[Kannon Fodda]

As others at rest (no charge / discharge loads for at least 30 minutes) 12.0V would be just below 50% capacity, 12.6/12.7V is full capacity for a lead-acid type battery. Note the word capacity as whilst appearing fully charged, over time the capacity will drop from the original rating say 100Ah, and might now be only 50Ah, since each charge / discharge cycle takes something away from the system, and deterioration is faster the more heavily the battery has been discharged, with below 50% on a regular basis not good for it.

As you do apply a load on the battery the overall voltage can also drop a little as the chemical reaction takes place that allows it to provide a current. Take away the load and the voltage may recover at rest. When I had a small lead-acid in my van, a few lights and the TV perhaps drawing only 3A current was enough to see an apparent voltage drop of 0.2V.

Now add in resistivity of the wiring in your motorhome. Many vans have thin cables and over a longer length of wire that alone causes a volt drop again perhaps 0.1-0.2V.

So now just the draw off load, plus cable resistance has your battery, which has lost a bit of capacity getting close to the 12.0V that your TV's sensitive electronics doesn't like. Your fridge, lights and stuff may keep going but the TV says No.

 

[DerryW]

Those voltage readings on your chart must be when you are getting some form of charge from your solar.
What voltage is reading when the TV says it’s low voltage.

Phil.

Those voltage readings on your chart must be when you are getting some form of charge from your solar.
What voltage is reading when the TV says it’s low voltage.

Phil. I removed all connections to the battery. It’s sat on the floor completely void of any connections

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[DerryW]

I think you need a bigger bulb, maybe a 60w headlight bulb, and keep it on for longer to check the capacity. You also need to disconnect all other inputs and outputs from the battery whilst running the ttest

Thanks Itsmcb. I will see hats the biggest bulb I have in stock. How long should I leave the bulb switched on ?

 

[DerryW]

Thanks Itsmcb. I will see hats the biggest bulb I have in stock. How long should I leave the bulb switched on ?

 

[DerryW]

On the advice of Itsmcb I have first reconnected the battery to both solar and EHU to make sure it’s fully charged. I have found 2 bulbs in stock a 12volt 21w and an headlight bulb which is 12volt 55w. Which bulb do you suggest I use for the test and for how long should I leave it switched on before taking the reading from the multi meter.
I assume I should disconnect all connections before running the test ?

Thanks once again.
Derry

 

[Itsmcb]

On the advice of Itsmcb I have first reconnected the battery to both solar and EHU to make sure it’s fully charged. I have found 2 bulbs in stock a 12volt 21w and an headlight bulb which is 12volt 55w. Which bulb do you suggest I use for the test and for how long should I leave it switched on before taking the reading from the multi meter.
I assume I should disconnect all connections before running the test ?

Thanks once again.
Derry

Taken from Lenny's instructions:

((To do a discharge test:-

First charge the battery fully and leave it to settle for an hour then:-
Disconnect all charging methods.

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%. ))

So. Assuming my maths is correct your 55watt bulb will draw 55watts divided by 12.7volts equals 4.33 amps per hour. Therefore if you connect the 55 watt bulb to your fully charged 110 amp battery for 6 hours and 30 mins it will draw 27.5 amps or 25% of your battery power and your battery should then be reading 12.4 volts if its fit and well.

 

[Phill D]

Phil.

Phil. I removed all connections to the battery. It’s sat on the floor completely void of any connections

If you are getting close to 13v disconnected and rested and it drops to 12v in a short period just using the tv then it’s likely you battery is shot!

But I am not sure from what I read that the battery is getting fully charged or it’s just not capable of being charged fully.

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[Itsmcb]

If you are getting close to 13v disconnected and rested and it drops to 12v in a short period just using the tv then it’s likely you battery is shot!

But I am not sure from what I read that the battery is getting fully charged or it’s just not capable of being charged fully.

I think the OP's opening post is a little misleading as he says the control panel is showing 12v or 12v plus so its probably not that accurate a meter

 

[DerryW]

I think you need a bigger bulb, maybe a 60w headlight bulb, and keep it on for longer to check the capacity. You also need to disconnect all other inputs and outputs from the battery whilst running the ttest

We had the same issues when on a lead battery... voltage would drop and tv ( also an Avtex) did not like it..
Main reason we went fir lithium battery... since then absolutely no issues.. tv still works right down until battery nearly empty....

Poppycamper just sent you a PM

 

[cyberyacht]

If you want more battery capacity without the weight, go Lithium LPo4. They are about half the weight of a lead acid. Your wallet will be lighter too.

 

[DerryW]

Taken from Lenny's instructions:

((To do a discharge test:-

First charge the battery fully and leave it to settle for an hour then:-
Disconnect all charging methods.

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%. ))

So. Assuming my maths is correct your 55watt bulb will draw 55watts divided by 12.7volts equals 4.33 amps per hour. Therefore if you connect the 55 watt bulb to your fully charged 110 amp battery for 6 hours and 30 mins it will draw 27.5 amps or 25% of your battery power and your battery should then be reading 12.4 volts if its fit and well.

Itsmcb.
Following up on todays task. I done exactly as you kindly set out on your above message.

The result was not good (not for me anyway) the reading from my brand new multimeter was 7.60volts.

So its a new battery. Not sure weather to go for a straight replacement lead acid c£100, a Gel c£175 or Lithium LPo4, Eco Worthy are doing 100AH LiFePO4. the downside is I think I'll need to change my charger and solar MPPT controller.

Thanks once again for all your help.