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Having a hard time reliably charging devices onboard.


Tasemu

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Hi there, i'll try to explain as fully as possible the issue i'm having. My girlfriend and I are living on a narrowboat that is 53ft long. It has 220ah of new sealed lead acid batteries which are topped up via an alternator attached to our BMC 1.8 engine.

 

Generally we will have the batteries at a voltage of between 12.5 - 12.9 with the alternator off and no load.

 

With this in mind, I am having real issues reliably charging my macbook. I have a small inverter that runs off a cigarette lighter plug which i'm using to plug the charger in. With the engine not running i am able to get minor charge before the inverter beeps and shuts down. I'm assuming this is due to low voltage cut-off which kicks in when i'm putting a load on the batteries. The charger appears to be 87 watts which should pull about 7 amps from the battery.

 

This issue tends not to happen when I turn the engine on and charge the laptop. However I have noticed that sometimes the laptop will charge fairly well and within just over an hour or so, the laptop is reasonably charged. However other times I have noticed that I can charge the laptop for 2+ hours and see charge gains of little more than 10%. This is very confusing to me and there are a few likely factors I will include below but am unsure how may effect the performance.

 

* Battery bank is 12v

* little inverter looks quite old, but appears to work.

* batteries are about 1 month old

* batteries have never been allowed to go below 12.3v

* unsure on the alternator output

* Charging the laptop from the opposite end of the boat to the batteries appears to not work, maybe bad wire size calculations are causing a voltage drop too high? Any idea how I could check this with a multimeter?

* Sometimes even with the engine running and charging the batteries, when i am charging the laptop I see the voltage in the battery bank start to drop as low as 12.8.

 

Sorry if this is verbose and difficult to read, just wanted to include as much potentially relevant information as possible.

 

Thanks for any and all advice anybody can offer me to hopefully solve this issue. :) 

Edited by Tasemu
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14 minutes ago, Tasemu said:

With this in mind, I am having real issues reliably charging my macbook. I have a small inverter that runs off a cigarette lighter plug which i'm using to plug the charger in. With the engine not running i am able to get minor charge before the inverter beeps and shuts down. I'm assuming this is due to low voltage cut-off which kicks in when i'm putting a load on the batteries. The charger appears to be 87 watts which should pull about 7 amps from the battery.

I'm not quite following this :

An inverter plugged into a cigarette lighter socket will be putting a large load onto wiring that was probably not designed for it.

If the socket is a 'long way' from the batteries it could well be that volt drop is causing the inverter to show low voltage.

What size (cross sectional area of copper - NOT overall diameter) is the cable ?

What distance is the lighter socket from the batteries (remember that the electricity has to go 'back' to the battery so the distance is 2x) ?

 

 

4 minutes ago, Tasemu said:

Sorry, yeah they are. should have stated that.

So your 12v batteries are reading 4.5-4.9 volts ?

 

yet you say that the batteries have never been allowed below 12.3v.

 

Maybe you could start again and define the problem a little more clearly.

Edited by Alan de Enfield
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OK so you have almost certainly wrecked your batteries.

 

Read the battery charging primer in the Maintenance forum PDQ. Then run the engine for at least 12 hours at above 1200 rpm and hope you an get some charge i to the batteries. They need to be around 12.7 volts half an hour or so after stopping charging.

 

Next invest in an ammeter and voltmeter so you ca monitor the charge and recharge when needed but actually daily recharging is recommended for optimum battery life.

 

 

See Alan's last paragraph!!!!!!!!

Edited by Tony Brooks
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6 minutes ago, Alan de Enfield said:

I'm not quite following this :

A cigarette lighter socket is 12v.

The Inverter is NOT connected to the cigarette lighter socket as the inverters job is to convert 12v Dc to 230v AC

 

So your 12v batteries are reading 4.5-4.9 volts ?

 

yet you say that the batteries have never been allowed below 12.3v.

 

Maybe you could start again and define the problem a little more clearly.

 

1: The inverter takes the 12v using a cigarette lighter plug, which goes into the wall socket, then supplies 230v AC to the laptop charger.

 

2: JESUS that's a bad type, i meant 12.5 - 12.9 (facepalm)

 

4 minutes ago, Tony Brooks said:

OK so you have almost certainly wrecked your batteries.

 

Read the battery charging primer in the Maintenance forum PDQ. Then run the engine for at least 12 hours at above 1200 rpm and hope you an get some charge i to the batteries. They need to be around 12.7 volts half an hour or so after stopping charging.

 

Next invest in an ammeter and voltmeter so you ca monitor the charge and recharge when needed but actually daily recharging is recommended for optimum battery life.

 

 

See Alan's last paragraph!!!!!!!!

Sorry, was a bad typo. I mean 12.5 - 12.9 no load no charging.

Edited by Tasemu
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2 minutes ago, Tasemu said:

1: The inverter takes the 12v using a cigarette lighter plug, which goes into the wall socket, then supplies 230v AC to the laptop charger.

 

See my edit.

I'd suggest that the wiring is not adequate and you are getting volt drop.

 

 

6 minutes ago, Alan de Enfield said:

An inverter plugged into a cigarette lighter socket will be putting a large load onto wiring that was probably not designed for it.

If the socket is a 'long way' from the batteries it could well be that volt drop is causing the inverter to show low voltage.

What size (cross sectional area of copper - NOT overall diameter) is the cable ?

What distance is the lighter socket from the batteries (remember that the electricity has to go 'back' to the battery so the distance is 2x) ?

 

I had similar problems with a fridge.

 

It would run happily when the engine was running, but with the engine off it was running continuously and not getting cold.

 

With the engine OFF the fridge was only getting about 11 volts, with the engine ON the fridge was actually getting 12.5 volts (even tho' the alternator was putting out 14.4 volts)

 

I was losing almost 2 volts with volt drop down the supply cable.

replaced it with the correct sized cable and problem sorted - fridge worked perfectly with the engine OFF.

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3 minutes ago, Alan de Enfield said:

See my edit.

I'd suggest that the wiring is not adequate and you are getting volt drop.

 

 

 

Sorry, i just read it now.

 

* the diameter appears to be about 10mm2 approx

* the length from the batteries i would imagine is 1-2 meters as it is the first socket from the batteries.

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The charging voltage dropping to 12.8 volts while charging may be a concern. Any decent alternator running at an engine speed of 1200 rpm or more should be able to supply 85 Watts without blinking so I wonder if you have a phase out in the alternator. This would give a low amps output plus a lower voltage. With well charged batteries expect at least 14.2 volts at 1500 rpm.

 

The inverter is probably not a pure sine wave one so it may well not suit the charger. My advice is to get a car type laptop power supply. Regrettably for a Mac it is likely to be expensive.

 

I also go with Alan's undersized  wire suggestion and that will be worse if you arr connecting to a cigarette lighter style socket. There are better solutions for 12V plugs.

 

 

Cable OD is no   help, you need the cross sectional area of the conductor.

Edited by Tony Brooks
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4 minutes ago, Tasemu said:

Sorry, i just read it now.

 

* the diameter appears to be about 10mm2 approx

* the length from the batteries i would imagine is 1-2 meters as it is the first socket from the batteries.

Sorry, but a diameter cannot be 10mm2.

Do you mean it is 10mm diameter, or the copper conductor is marked 10mm2 ?

 

10mm2 cable will have an OD of about 6 - 7mm depending on insulation type.

Edited by Alan de Enfield
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One thing I would suggest if you're using a macbook, I know for the older original magsafe charger you could buy a cigarette lighter style adapter for them... think it was called the apple magsafe airline adapter, not sure if you can get them for the newer style magsafe connector or not though. Would reccomend going down this route if possible as you're not stepping the voltage up to mains, to then drop it back down to whatever voltage the laptop wants. 

 

I never really got on with the smaller cheapo inverters in the past, always had similar issues of them giving low voltage warnings constantly... I have a bigger 5kw unit on my new boat and it's much better as things like the low voltage warning and cut off etc are all user programmable with a display on the top of the unit. Plus it's handy as you can get away with running mains vaucuum cleaners and electric chainsaws to name a few lol.

  • Greenie 1
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Some of the cheaper quasi wave inverters will also really upset some equipment too. My phone had a right strop when I plugged it into someones plug in inverter not long ago and I have had a couple of toothbrush chargers (which seem strangely prone) destroyed too.

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I have one of the small cheaper inverters in my truck/lorry.  I used to use it to charge laptop, photh, PALM Pilot (remember those?) when working and out on the road. This was before USB charging became the norm. One thing I found is mine was far from reliable.  It made short work of the battery if I was not driving.   I suspect a lot of your issue may be the inverter itself. I was never impressed with mine.

 

Plus your taking 12 volts, stepping it up to 220 volts and then plugging in a transformer that is taking that 220 volt down to something around 18 volts I would guess.  Lots of wasted energy in that process.

Edited by Kudzucraft
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23 minutes ago, Mike the Boilerman said:


Yep, agreed, the difference of £400 is astonishing!!!

 

I agree they are 400 quids more but for at least ten years of brilliant service at 76 pence a week its money well spent. Cheap and nasty inverters are simply that, cheap and nasty.

  • Greenie 1
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5 hours ago, lifeintheslowlanes said:

One thing I would suggest if you're using a macbook, I know for the older original magsafe charger you could buy a cigarette lighter style adapter for them... think it was called the apple magsafe airline adapter, not sure if you can get them for the newer style magsafe connector or not though. Would reccomend going down this route if possible as you're not stepping the voltage up to mains, to then drop it back down to whatever voltage the laptop wants. 

 

I never really got on with the smaller cheapo inverters in the past, always had similar issues of them giving low voltage warnings constantly... I have a bigger 5kw unit on my new boat and it's much better as things like the low voltage warning and cut off etc are all user programmable with a display on the top of the unit. Plus it's handy as you can get away with running mains vaucuum cleaners and electric chainsaws to name a few lol.

I also struggled with an inverter (that was rated higher than the Apple charger).  In the end one of these did the job.

 

https://www.coywood.co.uk/apple-macbook-pro-in-car-charger-85w-magsafe2-dc-adapter-14837-p.asp

 

You will need to ensure the feed cables to the socket are up to the job as mentioned by others.

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Hey, i've been looking for a good cigar macbook charger for my 2019 50 inch macbook pro but there aren't a lot of options out there yet it seems, its usb-c and needs 85w, i think its like 20v too.

 

I have a sunshine solar 1500w inverter i'm going to install over the weekend and see if this helps. Will report back. :)

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7 minutes ago, Tasemu said:

I have a sunshine solar 1500w inverter i'm going to install over the weekend and see if this helps. Will report back.

Install it directly to (and very close to) the batteries using VERY FAT (150 amp +) cable & then run the 230v wiring to you MacBook. That way you won't get much in the way of voltdrop.

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3 hours ago, Tasemu said:

Hey, i've been looking for a good cigar macbook charger for my 2019 50 inch macbook pro but there aren't a lot of options out there yet it seems, its usb-c and needs 85w, i think its like 20v too.

If this one isn’t right I guess the retailer would stock one which is. Not a bad price either. 
https://www.laptopartstore.co.uk/apple-c-29_54/85w-car-charger-for-apple-macbook-pro-a1261-usb-port-p-107762.html

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