PDA

View Full Version : Avoiding EHUs



Aethelric
18-12-2013, 12:29
I really wanted to avoid regular trips to sites just to keep the battery topped up, but I did not want to go the solar panel route.
I did an investigation and have written a little article here (http://2045.co.uk/blog/leisure-battery/). It only really applies to my vehicle, but the principles may be of interest to anyone with the same objective.

Beemer
18-12-2013, 12:42
I found your article very interesting, and a good idea if you have the 'know how', and prepared to limit your electricity usuage and maintain 'electrical discipline'.
I, on the other hand prefer my set up of a mix of solar panel and extra leisure batteries, which I can almost 'fit and forget', thus enjoy my trips away without having to chec the clock to see if I have the power to watch tv, or charge the laptop. :)

kangooroo
18-12-2013, 12:51
An interesting article.

I've just returned from a week's wildcamping in Cornwall and didn't use EHU at all. I used the fluorescent lights 4pm-1am daily, tap, electric blanket, other electrics and eberspacher etc as needed and got into the habit of charging my laptop via inverter as I drove. I don't have solar panels but I've found that providing I'm careful re usage then my leisure battery remains close to capacity with plenty of power on reserve if needed.

(I also stretched out my 20L water tank to last the full 7 days too!)

I think good discipline and avoiding wastage is the key.

Sky
18-12-2013, 12:59
I did an investigation and have written a little article here (http://2045.co.uk/blog/leisure-battery/).

Thank you for that; you've saved me a few investigations that have been in my roundtoit box for a while now. As a fellow electronics engineer myself, I fully understand your 'attitude'. ;)

DTDog
18-12-2013, 13:10
An interesting article.
Like you, it does always suprise me that poeple dont seem to bat an eye when paying for EHU when in reality it isnt necessary.

I'm actually in the 'Beemer' side of thinking, prefering to have more battery power than I need (through Solar panel and larger bateries) rather than trying to conserve the power usage. Maybe, like Beemer, I have other family members using the power and no matter how much you personally conserve the power, the rest of the family will have the telly on while sat playing on the phone etc. and it just gets in to an argument!

While away the other week with an old friend (in his caravan), he told me a story of how his daughter would have him fill BOTH water barrels ready for when she wanted to shower and would stand in the shower until both barrels had emptied! WHY? This was the only way he could get to go out in the van as his wife wouldnt leave the daughter behind and she insisted on 'keeping clean'!!

Frances
18-12-2013, 13:20
I enjoyed your article and the meticulous calculations. Its come to late to be of much use to me though as we have already gone down the throw £x00 at it, solar panel route. I've been very pleased with the result. We still only have a single battery though. We have as much power as we need when we need it, although we do use it carefully if we know we wont be moving for a while. On dull days we don't normally sit around in the van doing nothing, we are more likely to drive somewhere. When the sun is providing free power I really felt the need to use it.

K9d
18-12-2013, 14:06
An interesting article, I'm too new to it all to know how much power I will be using, but will use my battery isolator when leaving the van for a while, not sure how much my control panel will use its a 1988 Hymer so fairly basic.
My van came with 2 leisure batteries the idea being to swap the leads over when one got low, but that seemed a clunky solution to me so I invested in a couple of leads and now have them connected in parallel, so they charge and discharge together.
I was thinking of the solar route but your article has made me thing twice so will go down the suck it and see route instead.

Aethelric
18-12-2013, 14:35
I found your article very interesting, and a good idea if you have the 'know how', and prepared to limit your electricity usuage and maintain 'electrical discipline'.
I, on the other hand prefer my set up of a mix of solar panel and extra leisure batteries, which I can almost 'fit and forget', thus enjoy my trips away without having to chec the clock to see if I have the power to watch tv, or charge the laptop. :)

Hi Beemer, the whole point of my exercise was that I don't have to check the clock I don't limit my electricity usage (OK, I don't leave the lights and computer on 24/7 but I don't do that at home either) and I'm not an electricity disciplinarian.
I'm sat in the van as I type this on the lap. I've been on it for two and a half hours. I've had a light and the radio on for most of that time. I've just turned the heating down as its 24C in here (10C outside). We have been living in the van this way for over a week. A trip to the shops and the launderette topped up what I'd used yesterday and the battery still has plenty spare capacity.

But its a big van you have there Beemer, I doubt if my techniques would work for you anyway.:)

Tony Lee
18-12-2013, 14:41
It is always interesting reading how little power, water and gas people can make do with when they really want to, and the occasional tales of magic batteries that never run flat and last for 15 years, and water tanks that never empty and solar panels that fill the huge battery to bursting point by morning tea time add even more drama, but while these ascetic lifestyles might be interesting in the short term as an intellectual exercise or cathartic self-denial, for extended stays and any practical level of convenience and comfort, somewhat greater storage and generating capacity is essential.

Rodeo
18-12-2013, 15:52
I havent read the article yet,but I do recall when we had various self built campervans a few years ago,I never used to bother with a second battery,just the orig vehicle battery. Ran the tv,water pumps,fridge and strip lights whenever we wanted ,and never had a problem . Maybe sometimes we just about got away with that set up ,leaving enough life in the battery to start up,I dont know.

vespalien
18-12-2013, 15:59
It is always interesting reading how little power, water and gas people can make do with when they really want to, and the occasional tales of magic batteries that never run flat and last for 15 years, and water tanks that never empty and solar panels that fill the huge battery to bursting point by morning tea time add even more drama, but while these ascetic lifestyles might be interesting in the short term as an intellectual exercise or cathartic self-denial, for extended stays and any practical level of convenience and comfort, somewhat greater storage and generating capacity is essential.



Given that the OP has shared of lot of useful information, you two at best seem to be offering what my Mum would have called an ungracious response. He clearly stated that is was for his own van & his own circumstances. It's no wonder to me now that only a handful of regulars bother to post on here.

Have you not heard the phrase "Don't look a gift horse in the mouth". So it may not suit your style of motorhoming, but it may well suit others.

vespalien
18-12-2013, 16:14
My point is that you really ought to positively encourage people to post, especially when they are relatively new & potentially useful contributors.

I fully understand that you may not need such posts, but there will be plenty that do. A low cost alternative to just buying ££££'s worth of solar panels has to be a useful suggestion, even if it doesn't suit your profligate style of power useage, plenty of others have found it helpful.

Aethelric
18-12-2013, 16:20
Given that the OP has shared of lot of useful information, you two at best seem to be offering what my Mum would have called an ungracious response. He clearly stated that is was for his own van & his own circumstances. It's no wonder to me now that only a handful of regulars bother to post on here.

Have you not heard the phrase "Don't look a gift horse in the mouth". So it may not suit your style of motorhoming, but it may well suit others.

Thank you Vespalien
For the record I don't meter watch at home or in the van. Following my investigation I have enough hard data to know I don't need to worry about power. It's not about asceticism or an "intellectual exercise". It's just an engineers successful solution to a problem he had.

Siimplyloco
18-12-2013, 16:21
There’s one sure fire way to make relationships hurtful and destructive: judge the motives of other people as harshly and as negatively as possible....

John

Aethelric
18-12-2013, 16:41
I havent read the article yet,but I do recall when we had various self built campervans a few years ago,I never used to bother with a second battery,just the orig vehicle battery. Ran the tv,water pumps,fridge and strip lights whenever we wanted ,and never had a problem . Maybe sometimes we just about got away with that set up ,leaving enough life in the battery to start up,I dont know.

If you drove most days Rodeo that works fine. Provided there was enough left to start the engine, the alternator acts as a very fast charger. I think a lot of motorhomers have big vehicles and they stay parked up for days or weeks on end. Then its either EHUs or solar panels.

AndyC
18-12-2013, 16:50
Always good practice to reduce power consumption to balance the power available, however the first thing I would have done is to optimise the power available by investigating why there was only a pitiful 4A getting to the leisure battery when driving.

AndyC

Siimplyloco
18-12-2013, 17:08
Always good practice to reduce power consumption to balance the power available, however the first thing I would have done is to optimise the power available by investigating why there was only a pitiful 4A getting to the leisure battery when driving.

AndyC

Correct me if you think I'm wrong, but if a battery is charged or nearly so, a standard vehicle alternator will sense the higher voltage and taper off the charging current accordingly. The battery is, in effect, never fully charged, and that's why we fit a 'Smart' alternator regulator such as a Sterling which provides a near perfect charging regime.
John

spigot
18-12-2013, 17:19
I couldn't say I found the article interesting 'cos being totally thick when it comes to electricity, I hardly understood a word of it.

I have two 85a leisure batteries & two 40 watt solar panels in my smallish van & don't have to worry about watching meters or making calculations.

I spend that time enjoying myself.

vespalien
18-12-2013, 17:24
Well. I'm a simple person, so I read the thread.

On the first page there are 6 positive replies & the OP got 4 "likes" including mine, no doubt there are more, but I haven't bothered to count. I'm surprised that slipped you by. If you'd like to count the posts (ignoring the off track stuff of ours) I'm sure you will have to agree that most found it interesting or useful.

Not bad for an early post, I think we have a really useful member here if they are not put off by the cynical old hands.

Siimplyloco
18-12-2013, 17:42
Not bad for an early post, I think we have a really useful member here if they are not put off by the cynical old hands.

As Billy Bunter's Asian friend used to say. "The pompousfulness is terrific!
John
Now where's that 'Ignore' button....

Tbear
18-12-2013, 17:49
Some of us have limited spending power and enjoy living within our means so when a member of the site shares there ideas on how to enjoy life in a Motorhome without spending huge amounts of hard earned dosh, I for one applaud them.

I would love to see the links to the batteries that never run flat and the tanks that never empty or is that as Northerner used to say "me failing to recognise Irony" or just old fashioned sarcasm.

Richard

Beemer
18-12-2013, 18:16
Hi Beemer, the whole point of my exercise was that I don't have to check the clock I don't limit my electricity usage (OK, I don't leave the lights and computer on 24/7 but I don't do that at home either) and I'm not an electricity disciplinarian.
I'm sat in the van as I type this on the lap. I've been on it for two and a half hours. I've had a light and the radio on for most of that time. I've just turned the heating down as its 24C in here (10C outside). We have been living in the van this way for over a week. A trip to the shops and the launderette topped up what I'd used yesterday and the battery still has plenty spare capacity.

But its a big van you have there Beemer, I doubt if my techniques would work for you anyway.:)

I am sure that if I was to study your article, I could use your techniques in my 'shed', hence why I stated that I found your article interesting, but i must have misunderstood it, because I understood that you must 'check the clock' to know, quote "overheads for about an hour", 10 mins at a time to heat up shower" and "watch TV for a few hours". My opinion (and it is only an opinion) is using your system you would need to 'keep an eye' on electric consumption, but if you say you don't, fine, I believe you. :D
DT Dog knows full well what teenagers are like for using electric, and my lad is no different. He was able to flatten the battery I allocated for just the TV in one evening, but because I had another two separate leisure batteries, I was able to maintain all other habitation power.
My solar panel is still charging all three batteries, this December month.
I just wanted to put my angle on your informative post.

chrisinbrighton
18-12-2013, 18:28
GLi-12-100 | Genasun (http://genasun.com/all-products/genasun-lithium-battery-systems/gli-12-100/)

there are no more left just bought the last 10 lol

Tbear
18-12-2013, 18:32
We use LIon a lot at work, they do what it says on the box but it will be a while before I have a van that runs on them. :)

Richard

chrisinbrighton
18-12-2013, 18:34
I have bought one of these works quiet well to keep an eye on consumption Owl Micro Plus + CM180 CM 180 Electricity Energy Monitor Smart Meter Usage | eBay (http://www.ebay.co.uk/itm/400483114151?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT) there are cheaper ones that one can plug it into a invertor http://www.ebay.co.uk/itm/290953792201?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT

rottiontour
18-12-2013, 18:49
Hallo Aethelric,

many thanks for the article, i really enjoyed reading it. By the way, you have a very smooth style in explaining technical matters. Even for me being a little bit stupid, what electricity is concernd, and not very trained in reading technical matters in english, i did understand your message. Really good points to think about and adapt the one or other idea to my own "electrical MH-world".

Thanks again and merry x-mas

Bernd

Teutone
18-12-2013, 18:57
I have a battery to battery charger fitted and found that charging time for the leisure battery was dramtically shortened. One hours drive is usually enough to get a decent charge in the 125Ah Leisure battery I have fitted in place of the 70Ah original. Also added a 100W Solar panel and in hindsight I should have cabled up to fit a second solar panel for cloudy days or winter. Lost opportunity.
All lights are LED and we have no TV. We can stay without EHU for days and days as long as we don't use the Truma fan blower 24/7.

Total cost just under £300 (done all the fitting myself) and I wouldn't want to miss it. I agree that thoughtful use of your ressources is the key, even with Solar etc fitted. But I feel much more relaxed knowing that I can run the fan blower all day if I feel cold.

bru
18-12-2013, 19:38
some interesting information there , thanks

Aethelric
18-12-2013, 20:07
Always good practice to reduce power consumption to balance the power available, however the first thing I would have done is to optimise the power available by investigating why there was only a pitiful 4A getting to the leisure battery when driving.

AndyC

That's explained in the article Andy.

Tezza
18-12-2013, 20:24
Thank you for a really good article .....i have been looking at fuel cells...has anybody on here got one or now anything about these Truma Launches VeGA Fuel Cell for Caravans and Motorhomes (http://www.fuelcelltoday.com/news-events/news-archive/2012/august/truma-launches-vega-fuel-cell-for-caravans-and-motorhomes)

Aethelric
18-12-2013, 20:26
I have a battery to battery charger fitted and found that charging time for the leisure battery was dramtically shortened. One hours drive is usually enough to get a decent charge in the 125Ah Leisure battery I have fitted in place of the 70Ah original. Also added a 100W Solar panel and in hindsight I should have cabled up to fit a second solar panel for cloudy days or winter. Lost opportunity.
All lights are LED and we have no TV. We can stay without EHU for days and days as long as we don't use the Truma fan blower 24/7.

Total cost just under £300 (done all the fitting myself) and I wouldn't want to miss it. I agree that thoughtful use of your ressources is the key, even with Solar etc fitted. But I feel much more relaxed knowing that I can run the fan blower all day if I feel cold.

I did consider some sort of battery booster, but its extra complication and I don't need. Of course depending on the vehicle and the way its used many folk will need all of this technology.

sparrks
18-12-2013, 20:47
That's explained in the article Andy.

Interesting Article. What was the voltage when the charge current was 4A?

Aethelric
18-12-2013, 20:48
The article describes the way I tackled the issue of avoiding EHU for MY situation.
I AM NOT FRUGAL WITH THE POWER IN THE VAN.
Don't assume I am comprising on power usage. I am not.
If I had an array of solar panels and a generator, and a trailer full of batteries I would not use any more power than I do now.
If I had a bigger van or if I needed to run fans to stay warm, or if I parked up without moving for more than three days, I would have come up with a different solution.

Pauljenny
18-12-2013, 20:53
Thanks , Lots to consider there .

In these days of deisel particle filters , is it a bad idea to run your engine on idle to charge your batteries , except in an emergency..... ?

nicholsong
18-12-2013, 20:59
I did consider some sort of battery booster, but its extra complication and I don't need. Of course depending on the vehicle and the way its used many folk will need all of this technology.

Like Teutone I have a battery-2-battery charger which puts the full output of the alternator into the leisure batteries(2X 90ah). No solar.

But with this set-up we can top-up with about 15 mins driving a day when using the Truma. No need for EHU. except at home.

Once it is installed you just forget it - no complications.

Geoff

Aethelric
18-12-2013, 21:00
Interesting Article. What was the voltage when the charge current was 4A?

I can't remember sparrks, but it would have been maybe 0.2-0.4V lower than the vehicle battery.With maybe 0.1ohms in the circuit between the batteries due to cables, relay and the fuse, and my meter that gives 2-4 amps. Revving the engine had no effect. It would be higher without the meter.

sparrks
18-12-2013, 21:12
Whilst the leisure battery would be about 12.5v, with the engine running the alternator should be pushing out 13.8-14.2 volts and if the leisure battery was discharged it would pull more than 4A. I don't disbelieve you, just trying to understand why the charge current was so low. I haven't got a split charge system (using a B2B) so am not familiar with them and their ways.

Tony Lee
18-12-2013, 22:18
Always good practice to reduce power consumption to balance the power available, however the first thing I would have done is to optimise the power available by investigating why there was only a pitiful 4A getting to the leisure battery when driving.

AndyC


Yes, I was going to comment on that later. As an example, my BigRig has a 280Amp 24V alternator and it will pump 160Amps into the battery (obviously a big battery to match) when I first drive off in the morning and that will gradually taper off over a couple of hours to about 50Amps as the battery starts to get some charge in it. Proportionally a smaller system should put in at least 20 amps and get at least 15Ah into the battery during the first hour.
BUT as in all things, it depends. It depends on the state of charge of the battery when you start off. A nearly charged battery in combination with an alternator that drops its output voltage quickly in response to the state of charge of the starting battery, plus running through a diode-isolated split charger, plus a few metres of skinny cable and 4 amps might well be the best you can do. A couple of fairly minor changes and the charging current could increase significantly.

As for the poster actually criticising some of us for offering our well-considered and learned opinions - here is one just for you
http://helian.net/blog/wp-content/uploads/2010/06/pot-kettle-300x202.jpg

B2B chargers - mixed outcome there. For runs of one hour or less, a well-designed direct interconnect system will often put more AH into the leisure battery than a B2B, BUT once the run time gets to 2 hours or more, the B2B system will win.

Touringtheworld
18-12-2013, 22:29
Excellent post.

I enjoy learning new practical things ......

Doris likes shopping

Some people like picking holes in any and every thing

Some people appreciate what others have achieved and that they are happy to share their achievements.


I for one, appreciate your shared knowledge.

Cheers

Aethelric
19-12-2013, 00:44
Whilst the leisure battery would be about 12.5v, with the engine running the alternator should be pushing out 13.8-14.2 volts and if the leisure battery was discharged it would pull more than 4A. I don't disbelieve you, just trying to understand why the charge current was so low. I haven't got a split charge system (using a B2B) so am not familiar with them and their ways.

You are right about the alternator but the 12.5v you mention for the leisure battery is when its discharging. If its charging it will go up to around 13.5-14V with only 4A.

phillybarbour
19-12-2013, 05:49
Very interesting to read thanks for posting

Wooie1958
19-12-2013, 06:28
Some people like picking holes in any and every thing


Cheers



Well said, there`s a good few of them on here ................................... LOL

Aethelric
19-12-2013, 15:59
Thanks , Lots to consider there .

In these days of deisel particle filters , is it a bad idea to run your engine on idle to charge your batteries , except in an emergency..... ?

Yes, its a bad idea. I would only do it in an emergency.

sparrks
19-12-2013, 17:01
Yes, its a bad idea. I would only do it in an emergency.

I thought Diesel Particulate Filters were easy to clean out by getting the exhaust system hot, usually a blast down the Motorway or up a large hill in a low gear.

Goaskalys
19-12-2013, 17:05
Hi chaps, I've had my converted Transit van for 3 years now and have never hooked-up.
A couple of years ago I had a problem with the electrics which meant that the leisure battery drained the main battery, so I decided to wire them completely separately and charge the 110AH battery with an 80 watt solar panel. Now, I'm not electrically trained, but even i found it easy peasy to fit the solar panel and wire it into it's controller and then into the other leisure electrics. I replaced the flourescent bulbs with LEDS and added a few more and wired in a cigar lighter socket and an 300 watt inverter. I replaced the electric sink tap with a manual (Whale) one as the switch was unreliable anyway.
The fridge is gas powered and hot water I heat in the kettle on the gas hob. The electrics power lights, phone chargers, laptop, shaver and fairylights that we string-up when at festivals. So far, I have never got near flattening the battery living in it for 5 weeks last summer driving round Europe. I love my solar panel :)

Siimplyloco
19-12-2013, 17:53
I thought Diesel Particulate Filters were easy to clean out by getting the exhaust system hot, usually a blast down the Motorway or up a large hill in a low gear.

Agreed. Diesel engines need to work hard. We used to call that an 'Italian Tune Up'!
John

henryt
20-12-2013, 08:36
400w of solar, diesel airtop 3500, 3.5kw truma gas, all led lights, a 300w inverter for tv and laptop charging, a 20a rapid charger and 3x 110ah batteries. (I can watch discharge values and charge values on 2x digital power meters).


To be honest, the solar is pretty much useless in winter unless the sun is shining and the one tilting 80w panel gives more power than the other 320w !
In summer its way over specked and the batteries are fully charged very early morning, so I end up running the fridge on solar all day.
(nearly 50kg of weight on the roof)

conclusion- one 80 to120w tilting panel is about the best charge to weight option and most efficient for all year use.


Alternator split charging - start the engine and a burst of amps runs through to the leisure batteries dependant on their state of charge, but this does tail off to 6a very quickly just as it does on the engine battery of every vehicle.

conclusion - you do have to drive for hours to top up the leisures at 6a and it seems pretty pointless idling the engine to do so unless in an emergency with flat leisures.


Airtop diesel heating - Boy does this use power ! - on full chat 3ah dropping to 1ah when up to temperature , but the big problem is the amount of power the glow plug uses to start and stop it ( 6 to 20 amps )

Advantages - convenient being able to buy and use red diesel and instant heat .


Truma blown gas - hot water and heating (1 to 2.5 ah )

Advantage - uses less than half the power of a diesel system and costs half the price to run against normal pump diesel (roughly the same against red diesel )


HERE IS THE CRUNCH.

In summer the 3 x 110ah new batteries will happily give over 150ah of useable power but in winter they will only give 60ah of power due to the cold temperature. yes, just 60ah useable from 330ah

conclusion - At a time I need more power I have less than half the power and solar will not perform and all I can expect from a drive or idling is 6ah.

SOLUTION.

Strip off the solar leaving 80 to 120a tilting and use an 8kg 300w tiny silent generator hooked to the 20a battery charger which takes roughly 3 hours to put back the 60ah !

silverfox13
21-12-2013, 19:13
so I invested in a couple of leads and now have them connected in parallel, so they charge and discharge together.
I was thinking of the solar route but your article has made me thing twice so will go down the suck it and see route instead.

At the risk of being 'grandmothers and eggs' when you connected the two batteries in parallel make sure you drawn power from the pair taking the Negative from one battery and the Positive from the other (if possible) ... it helps even out the wear on them.

sparrks
21-12-2013, 23:46
400w of solar, diesel airtop 3500, 3.5kw truma gas, all led lights, a 300w inverter for tv and laptop charging, a 20a rapid charger and 3x 110ah batteries. (I can watch discharge values and charge values on 2x digital power meters).


To be honest, the solar is pretty much useless in winter unless the sun is shining and the one tilting 80w panel gives more power than the other 320w !
In summer its way over specked and the batteries are fully charged very early morning, so I end up running the fridge on solar all day.
(nearly 50kg of weight on the roof)

conclusion- one 80 to120w tilting panel is about the best charge to weight option and most efficient for all year use.


Alternator split charging - start the engine and a burst of amps runs through to the leisure batteries dependant on their state of charge, but this does tail off to 6a very quickly just as it does on the engine battery of every vehicle.

conclusion - you do have to drive for hours to top up the leisures at 6a and it seems pretty pointless idling the engine to do so unless in an emergency with flat leisures.


Airtop diesel heating - Boy does this use power ! - on full chat 3ah dropping to 1ah when up to temperature , but the big problem is the amount of power the glow plug uses to start and stop it ( 6 to 20 amps )

Advantages - convenient being able to buy and use red diesel and instant heat .


Truma blown gas - hot water and heating (1 to 2.5 ah )

Advantage - uses less than half the power of a diesel system and costs half the price to run against normal pump diesel (roughly the same against red diesel )


HERE IS THE CRUNCH.

In summer the 3 x 110ah new batteries will happily give over 150ah of useable power but in winter they will only give 60ah of power due to the cold temperature. yes, just 60ah useable from 330ah

conclusion - At a time I need more power I have less than half the power and solar will not perform and all I can expect from a drive or idling is 6ah.

SOLUTION.

Strip off the solar leaving 80 to 120a tilting and use an 8kg 300w tiny silent generator hooked to the 20a battery charger which takes roughly 3 hours to put back the 60ah !

Or maybe reduce your consumption - 60ah per day seems rather high. Maybe ditch the inverter and get a more efficient TV.

Aethelric
22-12-2013, 00:17
Or maybe reduce your consumption - 60ah per day seems rather high. Maybe ditch the inverter and get a more efficient TV.

We use a USB TV stick plugged into the laptop. It's ok, but the main problem is my present omni directional aerial (another challenge!). However, we can record all sorts of stuff on the pvr at home (on the timer) and download it to the laptop to watch whenever we want. It will run on its own battery for around three hours and charge up again fully in 90 mins (usually, but not always from the engine while travelling). The 12-19V car adaptor is much more efficient than using the inverter and the mains power supply.

CooP
22-12-2013, 05:37
At the risk of being 'grandmothers and eggs' when you connected the two batteries in parallel make sure you drawn power from the pair taking the Negative from one battery and the Positive from the other (if possible) ... it helps even out the wear on them.

Are you sure about this? I have understood that I should take both connections from the same battery, such as in the drawing provided here
Connecting Batteries in Series or Parallel (http://www.zbattery.com/Connecting-Batteries-in-Series-or-Parallel)

:confused:

IJenk52
22-12-2013, 07:31
Have a look at this: SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank (http://www.smartgauge.co.uk/batt_con.html) at the bottom of the page is the best arrangement and the logic behind it.


CLICK HERE TO REMOVE THESE ADVERTS