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Battery Problem Maybe?


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Hi,

I would be interested if a member could give me advise on the following. last night (0100) the invertor alarm went of so I switched it off noting the caravan voltage had dropped to 10. 3v !! the only appliances running were a med machine (240v 90W 1. 5 amp) and a 240v mosy plug in. The wind turbine was running and charging ok (green charging light). I have 2x85 amphr batteries in parrallel and a combination of a folding 80w solar panel and turbine to charge them.

Given the relatively low load requirements at night I am surprised at the low voltage alarm going off !! Anyway today I have disconnected one battery (voltage 12. 7v on disconnect) and left the other. I am attempting to determine if one or both batteries are on the way out?? today the turbine and the solar are charging the other battery and I am using various small loads plus a laptop.

Any suggestions of other things to do ?

many thanks

Howard6040

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You don't say how long your med kit was on or what else you are running of the batteries, but it looks to me that the wind genny is not enough even with an 80w panel.

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Hi, the med kit runs 2200 to 0600 only and this was the second night the invertor alarm has gone off. No other kit is on at night. during the day the solar and turbine combination copes quite adequately.

thanks

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If the med kit is 90W, & allow say 10% for invertor inefficiencies, that equates to 99W. At 12V, this is near enough an 8 amp load. You run the kit for 8 hours per night, so that's about 64 amp hours.

 

If your batteries are any age, or the wind &/or solar levels aren't sufficient to replace at least 64 amp hours per day plus your other loads, then yes, you will struggle.

 

Jim

Lunar Clubman SE Towed by Vauxhall Vivaro containing 6 border collies

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A Wind Turbine won't give anything like a 90W output so the batts will drain pretty quickly with a >90W load.

 

Tony

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What make/output is your wind turbine.

The Rutland 504 will give you about 3watts at 10mph (f3) wind, 30watts at 25mph (f5) and 50watts in 35mph (near gale f7).

The bigger Rutland 914 will produce about 30 watts at 10mph, 140watts at 25mph and 260watts at 35mph so you need quite a lot of wind blowing continuously to get anything worthwhile from one.

Stuck on 6' pole next to the van behind some trees will be virtually useless - you need it up high in an open field and even then you'll find that the wind strength is a lot less than you think. They work quite well on boats out on moorings because they are topping the battery up when it's generally not in use and the boat is out in the open without any building or trees around it

 

 

The only way you are going to check what's happening is by measuring the current flowing from the controller to the battery.

Edited by matelodave

2018 S-Max Titanium 2. 0 Tdci (177. 54bhp,180ps,132kw) Powershift + 2015 Unicorn III Cadz, Ventura Marlin porch awning

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Howard have you experienced problems before you started using the mozzie plug in as they tend to use quite a bit of electric ^_^

Paul B

. .......Mondeo Estate & Elddis Avanté 505 (Tobago)

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Howard have you experienced problems before you started using the mozzie plug in as they tend to use quite a bit of electric ^_^

 

No they don't - ours pulls 3W!

2018 Passat B8 Estate 150GT TDi150 towing a 2018 Bailey Unicorn S4 Seville

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No they don't - ours pulls 3W!

 

 

Mozzie plug in states, this is on top of the power that the inverter uses and the med machine

240V 8w operation (standard UK mains power supply)

 

Paul B

. .......Mondeo Estate & Elddis Avanté 505 (Tobago)

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. ........ med machine (240v 90W 1. 5 amp) . .............

Howard6040

 

This bit doesn't add up . .

 

 

240v 90w = . 38Amps

 

240v @ 1. 5A =360 Watt

Roughing it . . but in comfort . .

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This bit doesn't add up . .

 

 

240v 90w = . 38Amps

 

240v @ 1. 5A =360 Watt

240 x . 38 = 90

240 x 1. 5 = 360

 

Ohms law.

Graham

Unless otherwise stated all posts are my personal opinion 

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90watts at 240v = 0. 375amps however when you use an inverter there is an efficiency loss of about 10% so you'll take about 99 watts but this is being provide from a 12v battery so 99/12 = 8. 25 amps. If the machine has a motor in it then there will be a surge whenever the motor starts up so the peak current may be 2-3 times the running current.

 

Usually the wiring between the battery & inverter isn't up to much either (especially if you plug it into the van 12v socket) so you could easily end up losing a volt or more so even with a fully charged battery at 12. 6v the inverter may only see 11. 6v. As the battery terminal voltage drops the inverter is seeing even less until it either shuts off or the low bolatage alarm triggers. Ideally you should keep the inverter to battery cables a short as possible and they should not be less than 2. 5mm2, 4mm2 is better

 

You should not let the battery voltage drop below 12v.

Edited by matelodave

2018 S-Max Titanium 2. 0 Tdci (177. 54bhp,180ps,132kw) Powershift + 2015 Unicorn III Cadz, Ventura Marlin porch awning

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240 x . 38 = 90

240 x 1. 5 = 360

 

Ohms law.

 

Yes . . that was my point . .

the OP said "a med machine (240v 90W 1. 5 amp)"

 

which didn't make sense . . 90W @ 240v is . 38A not 1. 5 A . . 1. 5A would be 360W

Roughing it . . but in comfort . .

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They work quite well on boats out on moorings because they are topping the battery up when it's generally not in use and the boat is out in the open without any building or trees around it.

And likewise they work very poorly on narrowboats on the cut, exactly as you were saying - trees and other obstructions severely restrict their effectiveness.

 

Tony

 

This bit doesn't add up . .

 

 

240v 90w = . 38Amps

 

240v @ 1. 5A =360 Watt

Yes, you're right, but we can ignore the 230V current figures and just look at the power. 90W being drawn and considerably less than 90W being put back in. 90W @ 12V is 7. 5A. Inefficiencies will mean even more than that. Battery won't last long.

 

Tony

It's interesting to note that OP states he has two batteries. That's all very well if they're being topped back up to 100% each day. If they're not then he could just as easily have two hundred batteries - eventually they'll go flat.

 

Tony

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Hi Guys,

thanks for all your replies and there are some interesting comments I have taken note!! a couple of anomalies from me the med machine (CPAP) is ac in at 90W !.5 amp and the output is 24v 3. 75 amp if that helps to explain things. my turbine is a rutland 901 which can give 7 to 10 amp in a good wind. I am currently on a rally on the coast with a good on/off wind. during the day I have been running the laptop and a dvd up to 2 hours. obviously the battery voltage drops (2 batteries in parrallel) however before bedtime the combined effort of the solar (80W) and turbine have taken the combined battery voltage back to 13. 2 v .

therefore for the med machine to fail after 3 hours at night leads me to suspect the batteries (5 years old) are taking a charge but not holding a depth of charge and I have almost convinced myself to buy new ones??

regards

Howard6040

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The quoted 13. 2 volts only indicates that charging system volts is more than the batteries. It gives no indication if the batteries are anywhere near topped up.

To know that you need to measure the volts after charging and with no discharge; but after the surface charge has been dissipated. A value of between 12. 7 and 12. 9 volts, which value unfortunately depends on the lead alloying employed, indicates full batteries. The surface charge will drop off over 4 hours resting or can be knocked off quicker by a bit of use. Clearly, any use will drop what is left a bit, but fully charged there is a lot there so discretely draining a bit will not cause an issue.

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Hi Guys,

thanks for all your replies and there are some interesting comments I have taken note!! a couple of anomalies from me the med machine (CPAP) is ac in at 90W !.5 amp and the output is 24v 3. 75 amp if that helps to explain things. my turbine is a rutland 901 which can give 7 to 10 amp in a good wind. I am currently on a rally on the coast with a good on/off wind. during the day I have been running the laptop and a dvd up to 2 hours. obviously the battery voltage drops (2 batteries in parrallel) however before bedtime the combined effort of the solar (80W) and turbine have taken the combined battery voltage back to 13. 2 v .

therefore for the med machine to fail after 3 hours at night leads me to suspect the batteries (5 years old) are taking a charge but not holding a depth of charge and I have almost convinced myself to buy new ones??

regards

Howard6040

Where does 24v come from? the batteries are in parallel aren't they?

An eye for an eye only ends up making the whole world blind.

Mahatma Gandhi

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Where does 24v come from? the batteries are in parallel aren't they?

From the CPAP's ac unit as I understood it?

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From the CPAP's ac unit as I understood it?

Ah, ok. Then the cpap uses an ac 230v to 24v transformer, but this is being run from a 12v dc source. So it's going 12vDC to 230vAC and back to 24vDC :o. Better off using a 12v to 24v DC TO DC power source, surely? http://www. ebay. co. uk/itm/Silver-Gray-Dampproof-DC12V-Step-Up-to-24V-240W-10A-Car-Power-Converter-Adaptor-/271497022034?pt=UK_BOI_Electrical_Test_Measurement_Equipment_ET&hash=item3f367bca52

 

Also, if you are deep cycling the batteries (and it sounds like you are) then 5years is a pretty good lifespan IMHO. I would consider that good value for money.

Edited by dreadly

An eye for an eye only ends up making the whole world blind.

Mahatma Gandhi

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It maybe time for new batteries and I would consider getting 110ah ones, but before buying I would check your batteries levels and check with a hydrometer for electrolyte colour and condition

Paul B

. .......Mondeo Estate & Elddis Avanté 505 (Tobago)

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Based on OP's most recent post I'm 99% certain, no. .. make that 100% certain that the batteries are not ever being fully recharged.

 

There is no way to prove this without a Smart Gauge, but if OP was going to spend that kind of money (£120) it might be better to spend it on more solar rather than on something that is just going to demonstrate that more solar is required.

 

Tony

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Hi,

you are right the med machine needs 12v dc via power invertor to mains then via (its own convertor) to 24v dc. warrenty on machine will not allow 24v dc direct.

have tried disconnecting each battery for 12 hours to see if voltage drops off and it didn,t. Still convinced I need to replace batteries and will consider 2x110 amp/hr instead of 85s.

good wind last night which easily brought the batteries back up to strength overnight with green lights showing by 0500 this morning.

regards

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thanks for the replies. yes the med mach is 24v via ac (it has its own convertor) and the warrenty won. t allow me to supply 24v direct. tried disconnecting both batteries individually for 12hr to see if voltage dropped of and it didn't so conclude batteries getting old. will replace with 2x110amp hr I think.

regards

Howard 6040

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Based on OP's most recent post I'm 99% certain, no. .. make that 100% certain that the batteries are not ever being fully recharged.

 

There is no way to prove this without a Smart Gauge, but if OP was going to spend that kind of money (£120) it might be better to spend it on more solar rather than on something that is just going to demonstrate that more solar is required.

 

Tony

:goodpost:

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Hi,

thanks for all the comments and advise. am changing batteries and will see how things go from there.

howard6040

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