# B 2 B Charger-Battery Type?



## korky24 (Oct 19, 2007)

Hi there,

As I mainly camp off EHU, all year round, I am wanting to fit a B 2 B charger-not interested in solar.

My two leisure batteries are 90ah wet lead acid "sealed".

Other posts on the subject and Sterling Power recommend open cell wet lead acid batteries for optimum charging performance.

These type of batteries are obtainable but decreasingly so and are being replaced by the "sealed" low maintainence type. Tayna no longer stock them for instance.

I emailed Sterling who replied that their B 2 B Charger could be configured for all battery chemistries. I realise that there is a selector switch for battery type on the charger but don't want to shell out a lot of money if I am not getting the full benefit from this piece of kit. I also don't want to fit it to find in a few years that suitable batteries are unobtainable.

I have also read posts that state with more modern higher amperage alternators this negates the need for the B 2 B charger somewhat. But I also understand that these particular chargers "trick" the alternator into delivering a higher charge when needed and that without one the alternator will send a much lower charge to the leisure batteries.

If anyone could shed some light on the subject it would be much appreciated.

Many thanks, John.


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## Techno100 (May 8, 2010)

It's only a recommendation and mainly based on battery price bang for buck. Sealed batteries are fine and often as cheap with clever shopping.

I would recommend checking your dimensions when replacing as a worthwhile upgrade is bigger batteries

cheap as chips
http://www.ebay.co.uk/itm/PAIR-OF-8...tEquipment_Accessories_SM&hash=item3f2172a1cc


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## listerdiesel (Aug 3, 2012)

korky24 said:


> But I also understand that these particular chargers "trick" the alternator into delivering a higher charge when needed and that without one the alternator will send a much lower charge to the leisure batteries.


Lots of smoke and mirrors, John!

If you imagine your vehicle battery and alternator as an isolated pair of devices, 90AH battery, 100A alternator.

If the battery is down on volts, the alternator senses this at its output terminals and increases its output up to its maximum of 100A to bring the battery up to fully charged.

If you attach another battery in parallel with the existing vehicle battery by suitably heavy leads, the alternator still looks at its terminal voltage to understand what is going on, it doesn't 'know' that there is a second battery connected, it just sees a voltage and acts on that.

So far, everything is fine, no need to get into any tricky stuff at all, but you may want to put a fuse in between the batteries and maybe something to protect the vehicle vehicle against over-discharge.

If you add fuses and relay contacts between the two batteries, there will be a slight volt drop across them (0.2V to 0.4V) not a huge amount, but quite definitely measurable, and the alternator cannot see this loss, it just looks at its output terminals as before.

For most users, that would be fine. The difference of 0.2V to 0.4V is only significant at high charge rates, and as soon as the charge rate falls, so does the losses in the fuses etc. At low charge currents the losses are really not worth worrying about.

The problem with 'tricking' the alternator into giving a higher voltage is that the vehicle battery is still connected, so the vehicle battery sees a higher voltage than previously. While a wet lead-acid battery will tolerate some overvoltage, sealed batteries are far less tolerant and far more easily damaged.

So in my view, both in theory, and in practice, there is no need for anything better than a decent pair of leads, a fuse and a low-voltage disconnect device to save the vehicle battery from being flattened by the habitation loads.

Motorhomers are 'gadget-conscious' and buy things like this by the hundreds, but in most cases they are not needed if the original cabling etc was done properly.

You would be advised to have a charger for the leisure battery that can be run independently of the vehicle battery for periods when you are not driving around.

Sorry for the long post.

Peter


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## grizzlyj (Oct 14, 2008)

Hi

One day I will hook up a B2B charger to my AGM batteries. I'm sure you've read their manual?

"There is sometimes no choice but to use gel or AGM. The unit has the settings to enable these to be charged within their recommended charging curves."

I'm in no way an expert, but as far as I know a modern alternator will only charge at one voltage, and on or off. To fully charge a battery the input voltage needs to be stepped as it fills. The B2B does this, so fills a battery to a higher level of charge than a normal alternator ever will.

I realise some would say you don't need that last little bit and an alternator does a good enough job for most, but I'd appreciate being corrected if my above thinking is wrong 

Edit; written while Peter was writing sorry


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## Techno100 (May 8, 2010)

I inherited this set up of twin Elecsols (very expensive) with Sterling 50amp BtoB This was provided by Vanbitz and the elecsols have 7 year warranties. Would Eddie fit that kit if it wasn't OK :roll:

Personally I'd have just used Alphaline sealed at less than half the price.


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## grizzlyj (Oct 14, 2008)

listerdiesel said:


> korky24 said:
> 
> 
> > But I also understand that these particular chargers "trick" the alternator into delivering a higher charge when needed and that without one the alternator will send a much lower charge to the leisure batteries.
> ...


Hiya

I'm not sure I entirely understand you, but the only(?) drawback is if the vehicle battery isn't an open type then its over voltage may be a problem for it?


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## Techno100 (May 8, 2010)

The secret of long battery life is to never over discharge them then they won't need loads of amps fired in :wink:


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## GrayB (Sep 6, 2011)

*B2B charger*

Well Peter you have put a spanner in the works.I had just convinced myself that I need a B2B charger.Ive done all the research c-tech and sterling and thought I new what I was up to.
I was going to fit a second leisure battery but I have the problem of space and the second one would probably be 3 meters away from the one already fitted.
That lead me to B2B charger,we do a lot of wilding and only stop for one or two nights at the most,usually moving on but not far enough to replenish the single leisure battery.
I have 80w solar panel which does help,but the sun doesn't always shine!

Oh Dear what do I do ?

Cheers for now Gray.


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## javea (Jun 8, 2007)

Well here's my two pennorth for what it's worth from a non techie.

I travel to and from Spain often when it is cold. At night television, Sky box, lights and heating on, then overnight heating on to keep us warm. Result was that the two 110AH Elecsols were getting very low and despite being recharged whilst driving we were having problems with losing power.

Changed the bulbs for led's and fitted a Ctek B2B charger, went for that as it provides a maximum of 20 amps whereas the Sterling was at 50 amps which I thought might be excessive.

Been running this setup for a couple of years without any problems and no power loss issues.

Mike


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## teemyob (Nov 22, 2005)

*b2b*

I decided in Favour of the Ctek D250s

Here


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## korky24 (Oct 19, 2007)

Thanks everyone, as usual an informative selection of posts.

It's answered my question about suitable battery type but I'm not sure now if I need a B 2 B charger after the comprehensive post from Peter.

Off for a swift pint in Wirksworth now over which I shall cogitate on all of the above. 

Many thanks, John.


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## listerdiesel (Aug 3, 2012)

It's all a matter of personal preference and how much money you want to throw at the (small) problem.

Many with B2B units could possible live without them, some are a bit confused by the issues of which battery types you can and cannot use, many question why you need them in the first place.

I can only look at the issue on the basis of basic battery charging and how alternators work, and Ohm's Law. We manufacture battery chargers but do not get involved in consumer equipment. We have a life requirement of 15-20 years of continuous use.

Very rarely will you find B2B's in use industrially, as for the most part they are purely a consumer device.

We've got solar panels, and that is to my mind the way to go, but many cannot fit them so need an extra means to charge the leisure battery.

I have never used such things and probably never find the need to, but for some they provide a means to an end and if they are happy with them then that's fine with me.

Peter


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## listerdiesel (Aug 3, 2012)

grizzlyj said:


> Edit; written while Peter was writing sorry


No need to be, the more information we get out, the better the choices available for folks to look at and base their decision on.

Peter


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## listerdiesel (Aug 3, 2012)

Just a point to make:

The batteries MUST have decent cables to their loads and from their charging services.

If that basic provision is taken care of, then a lot of issues would be solved.

A long run of cabling for a second battery is not a big issue if the cable sizing is correct.

On our DMU chargers for the railways, we use 50mm welding cable for the 200A chargers and 35mm for the 100A. We allow 0.6V for cable drop as the chargers haven't got remote sensing, and they are fine.

Most people wouldn't know what 50mm welding cable looked like if they fell over it, but it is commercially available and terminals can be crimped or soldered on.

Sort the cabling anf fusing out properly, and a lot of the other issues will go away.

Peter


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## pieterv (Feb 3, 2009)

Sterling very clearly says that for maximum benefit you need non-sealed batteries. The reason being that at the high charging voltages the battery will gas, and will need water refilling. On a sealed battery you can therefore not utilise this higher voltage.

As to needing multi stage charging, yes that is better, but wouldn't the Sterling start the charging regime from scratch after you have taken a coffee break (during which obviously the engine was switched off)? So that only really works when you take a very long drive without breaks.

Pieter


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## WildThingsKev (Dec 29, 2009)

javea said:


> Well here's my two pennorth for what it's worth from a non techie.
> 
> I travel to and from Spain often when it is cold. At night television, Sky box, lights and heating on, then overnight heating on to keep us warm. Result was that the two 110AH Elecsols were getting very low and despite being recharged whilst driving we were having problems with losing power.
> 
> ...


Do you have the "dual" version and a solar panel and if so do you know if the ctek output when on solar is also 14.4v?

Kev


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## grizzlyj (Oct 14, 2008)

pieterv said:


> As to needing multi stage charging, yes that is better, but wouldn't the Sterling start the charging regime from scratch after you have taken a coffee break (during which obviously the engine was switched off)? So that only really works when you take a very long drive without breaks.
> 
> Pieter


My small multi stage charger for my bike steps through each unrequired stage in maybe a minute when I plug it in. How long does a B2B take I wonder?


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## eddievanbitz (May 1, 2005)

listerdiesel said:


> Just a point to make:
> 
> The batteries MUST have decent cables to their loads and from their charging services.
> 
> ...


People often ask us about B2B on American RVs and the advice is simple, you wont need it. With the square section on the cable used and a 300 amp seloniod controlling the charge all fitted from scratch it solves a lot of problems

Eddie


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## listerdiesel (Aug 3, 2012)

eddievanbitz said:


> People often ask us about B2B on American RVs and the advice is simple, you wont need it. With the square section on the cable used and a 300 amp solenoid controlling the charge all fitted from scratch it solves a lot of problems
> 
> Eddie


Absolutely!

I feel that we tend to skimp on wiring over here, and use thin cable for long runs to save a few pennies.

The annoying thing is that there are plenty of volt drop and current-carrying tables around, but few seem to use them on motorhome construction.

Here's one such table from a CAV alternator document on our website:

http://www.stationary-engine.co.uk/CAV-Electrical/CAV116.htm

The whole document can be viewed here:

http://www.stationary-engine.co.uk/CAV-Electrical/AltBatt.htm

It's a bit technical, but goes through alternator basics.

Peter


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## nicholsong (May 26, 2009)

What i am not sure about in all the posts is which ones have addressed the OP's need for wilding.

Peter (listerdiesel) suggested a set-up without B2B, using extra heavy cabling and certain protections for the vehicle battery etc., but he also said an independent charger would be needed for when the engine is not running. Why? - if his system had already charged the leisure batteries for, say a 2 day stay?

I am wondering which answers are applicable to a MH usage which may include periods of short journeys (e.g 30 mins.) and 2-3 day stops. 

Maybe Peter would like to comment on whether his solution is appropriate for this usage - maybe his chargers run for longer periods?

I do not know the age of my(vented lead-acid) batteries but they are more than 4 years old and could be 6 years old. 

I have fitted (rightly or wrongly) a B2B for this usage and I find it whacks in a good charge quickly. 

Although the batteries are old and probably not more than 85% efficient, after a 30 min. run and following a 'rest' period of 1-2 hours plus they are still showing 13.8V

I am surprised the batteries have lasted so long, but I suspect it maybe because they are kept topped-up by the B2B.

If my last statement is correct there maybe some savings on the initial outlay by longer battery life. I am not saying that if the other charging solutions keep the batteries charged the longevity would not be the same.

As an aside I think when I do replace the batteries I will (dimensions allowing) fit 2X 6V 'Traction' 240A batteries in series.

Geoff


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## WildThingsKev (Dec 29, 2009)

WildThingsKev said:


> Do you have the "dual" version and a solar panel and if so do you know if the ctek output when on solar is also 14.4v?
> 
> Kev


I've had a reply from CTEK now and it is indeed 14.4v output when on solar.


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## Jean-Luc (Jul 21, 2005)

I took deliver of my mh in June 2005, fitted with two Varta Semi-traction batteries. Because I do a lot of off ehu camping I shortly afterwords fitted a Stirling B2B.

One of the benefits I consider I have is that after a stop of a few days a few hours driving will return the batteries to full.

The batteries are now going on for eight years in use and showing no signs of giving up.

They have however required monitoring of their electrolyte levels and occasional topping up.

Going on the assumption that they should have died after four or five years I recon the B2B has paid for itself.


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## listerdiesel (Aug 3, 2012)

nicholsong said:


> What i am not sure about in all the posts is which ones have addressed the OP's need for wilding.
> 
> Peter (listerdiesel) suggested a set-up without B2B, using extra heavy cabling and certain protections for the vehicle battery etc., but he also said an independent charger would be needed for when the engine is not running. Why? - if his system had already charged the leisure batteries for, say a 2 day stay?
> 
> ...


Hi Geoff:

I said:

"You would be advised to have a charger for the leisure battery that can be run independently of the vehicle battery for periods when you are not driving around."

Obviously, if you are not running the engine to charge the batteries, they will go flat, so it would be a good plan to add a charger so that you could hook up to a genny or EHU. That was what my comment was trying to address.

You have to have 'something' to charge the batteries if there is no vehicle activity. Ours is solar, plus we have a 26A charger, but vehicle and hab electrical systems are totally separate.

Peter


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## pieterv (Feb 3, 2009)

grizzlyj said:


> My small multi stage charger for my bike steps through each unrequired stage in maybe a minute when I plug it in. How long does a B2B take I wonder?


My understanding is that the stages refer to e.g. max current until a certain voltage is reached, then constant voltage for a certain number of hours, then maintenance charge.


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## nicholsong (May 26, 2009)

korky24 said:


> Hi there,
> 
> As I mainly camp off EHU, all year round, I am wanting to fit a B 2 B charger-not interested in solar.
> 
> ...


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## listerdiesel (Aug 3, 2012)

I said that it would be useful to have a genny or EHU input. if there's no vehicle movement and the batteries are flat, you'll need a good run to charge the batteries whether you have B2B or not.

There's no magic, if the battery is 220AH and you have a 100A alternator, it's going to take 3-4 hours of driving to bring the battery back up to near full charge, where a 20A or 30A charger can do the same thing if you can plug it in somewhere, and while I understand that EHU's don't grow on trees, most of us have to empty loos and get water etc, so one night in three or four at a site would do the job, and cheaper than driving for 3-4 hours.

The need for battery charging is no different if you are wild camping than ordinary motorhoming on sites, you just don't have so many options for power.

If you're moving every day, the vehicle alternator should be able to cover the daily use, but I'd prefer to be able to spens more than a couple of days if I found a decent spot.

I know solar panels are not everyone's cup of tea, but they are a better solution in my view, and the power is almost free.

Peter


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## korky24 (Oct 19, 2007)

Hi Peter,

Thanks for the info. I already have an onboard 230v charger, but I would only visit a site once in 3 or 4 weeks to get the laundry done.
I don't like sites.

No lack of power in the summer, only in deepest darkest winter, when solar wouldn't be worth it in my opinion.

Still can't get passed the original conundrum that Sterling clearly state only use open cell wet lead acid batteries with their B 2 B chargers, then tend to partly contradict this statement. Other posters have also said battery type doesn't matter.

Still not convinced either way on battery type.

Thanks for everyone's four pennorth.

John.


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## Techno100 (May 8, 2010)

Well if my elecsols dont last 7 yrs I'll be calling Vanbitz


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## Jean-Luc (Jul 21, 2005)

Open cell batteries are generally the cheapest type and a premium quality example will cost less than sealed AGM or Gel.
Because open cell batteries can be topped up it is permissible to charge them faster and use higher voltages, hence the claim that a B2B whacking in up to 50 amps with a four stage charging regime puts more power in.

As Stirling say, sealed batteries can be used and the B2B has setting for this, however batteries will not be charged to the same level as open cell which can be topped up to replace the water loss due to the aggressive charging.

Perhaps 'aggressive' is the wrong word as such charging is actually good for maximising the life of the battery.

BTW I can never understand the fixation some people have with sealed and or gel batteries and pay extra for them. After all, an open battery is unlikely to spill its contents unless the motorhome is put on its side or roof, a situation not uncommon in yachts but in a motorhome 8O

Draw your own conclusions from the attached article.


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## grizzlyj (Oct 14, 2008)

So, broadly speaking-

A B2B will charge any battery, some better than others.

It will charge AGMs, but a little more slowly than open cells because of the lower voltage setting required. Both will be full though.

A B2B will charge more quickly than just the alternator on any given journey. Any suggestions on how much more quickly? Twice as?


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## korky24 (Oct 19, 2007)

Hi Jean- Luc,

Read my original post again.

I want to buy open cell batteries but they are getting harder to find. I have no obsession with other types of battery, but they(sealed) are becoming the norm.

John.


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## Techno100 (May 8, 2010)

Interestingly cheap open wet batteries only tend to have 2 year warranties while my alphaline sealed have 4 years and £85 for 125ah is cheap. The 7 yr warranty elecsols came with the van I would never spend that much on a battery.


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## listerdiesel (Aug 3, 2012)

grizzlyj said:


> So, broadly speaking-
> 
> A B2B will charge any battery, some better than others.
> 
> ...


Would that it was just that simple! 

The trouble is that generalisations don't work in this industry.

Many B2B systems are quite specific about what you can and cannot charge. Sterling at least tell you not to go sealed, many don't.

At the end of the day, all they do is offer a slightly elevated charge voltage, and a 2 or 3 stage charging regime. The actual power to charge comes from the same alternator on the vehicle engine, so they cannot charge any faster than allowed by the engine speed, alternator output, and the state of charge of the vehicle battery.

Peter


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## WildThingsKev (Dec 29, 2009)

korky24 said:


> Hi Jean- Luc,
> 
> Read my original post again.
> 
> ...


Look at Banner Energy Bull batteries, I bought mine from a local motor factors but I think they are available from Roadpro. They outperformed the opposition in a magazine test a few years ago which included cutting them open to see what was inside. 3 year warranty.


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## GrayB (Sep 6, 2011)

Hi lads, 
Many thanks to all who have contributed to this post,I have learnt a great deal it is all as clear as mud, (only joking)
I think I will forget the B2B charger for the time being and go for fitting a second leisure battery even if it is some distance from the one already fitted.
One question can anyone point me in the right direction as to what type of fuse / fuse holder I need to fit either end of the cable that will connect the two batteries together ?

Thanx in advance

Gray.


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## listerdiesel (Aug 3, 2012)

You'd need something like a tagged HRC fuse on standoffs, or a BS88 Red Spot fuseholder which would take a standard fuse.

I'm not in favour of exposed terminals, so a Red Spot holder would be good.

Ratings go: 20A 32A 63A 100A 200A, the last two are very big, I'd suggest a 63A surface mount holder using a motor-rated 63M100 fuse.

63M100 is a 'motor rated' fuse that will withstand power surges, but still blow at 70A or so continous current. If you think you'll need a larger fuse, the the 100A it would have to be.

If you're not in a huge hurry, I may have a used holder in the workshop and possibly a fuse as well. We will also have M6, M8 and M10 insulated standoffs if you prefer to go that way.

Wiring between the batteries needs to be 16sq mm or 25sq mm, larger if you want to go to 100A fusing.

Peter


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## Jean-Luc (Jul 21, 2005)

korky24 said:


> Hi Jean- Luc,
> 
> Read my original post again.
> 
> ...


Hi John,

Please don't take offense by my remark. What I was getting at is some people seem to dismiss the option of open cell batteries as the sealed for life 'maintenance free' type get so much hype.
However, because they are so constructed they require gentler charging which ultimately means when 'fully charged' they have less power in reserve than an equivalent open cell which because they can be allowed to gas and are top upable.


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## listerdiesel (Aug 3, 2012)

We do have a white 63A holder and a 63M100 HRC fuse available, both are new.










Here for comparison is a TC100 tagged HRC fuse on M8 standoffs:










Length of the holder is 110mm, length of the standoff/fuses is 140mm.

Peter


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## Jean-Luc (Jul 21, 2005)

Techno100 said:


> Interestingly cheap open wet batteries only tend to have 2 year warranties while my alphaline sealed have 4 years and £85 for 125ah is cheap. The 7 yr warranty elecsols came with the van I would never spend that much on a battery.


Genuine semi-traction open wet batteries aren't cheap. Banner Energy Bull


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## listerdiesel (Aug 3, 2012)

Do you really need to buy a traction or semi-traction battery?

They tend to have slightly different plate chemistry to 'standard' batteries, although they are also built to take rather more abuse.

I've not looked at the market for some time as we buy our kit commercially, but I'd have thought there were still products available if you know where to look.

Many trucks use 2 large 12V batteries in series, but they are the same batteries as we use.

Peter


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## nicholsong (May 26, 2009)

Jean-Luc said:


> Techno100 said:
> 
> 
> > Interestingly cheap open wet batteries only tend to have 2 year warranties while my alphaline sealed have 4 years and £85 for 125ah is cheap. The 7 yr warranty elecsols came with the van I would never spend that much on a battery.
> ...


But sometimes one has to buy the right tool for the job

Geoff


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## Techno100 (May 8, 2010)

Jean-Luc said:


> Techno100 said:
> 
> 
> > Interestingly cheap open wet batteries only tend to have 2 year warranties while my alphaline sealed have 4 years and £85 for 125ah is cheap. The 7 yr warranty elecsols came with the van I would never spend that much on a battery.
> ...


But Sterling advises CHEAP


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## nicholsong (May 26, 2009)

Techno100 said:


> Jean-Luc said:
> 
> 
> > Techno100 said:
> ...


Are you sure? I have not read that, only that they advise open wet batteries, which is what Jean-Luc was referring to in traction batteries'

Geoff


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## Techno100 (May 8, 2010)

Yes they compare them as being a third of the cost of sealed AGM etc


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## Techno100 (May 8, 2010)

> The key question
> 
> Another way to approach this subject is the simple Irish way (being Irish myself). I went onto the web and obtained 3 different battery type prices, these were the first prices I came to and have no reflection on any company. I was looking for about a 100 amp hour battery.
> 
> ...





> Conclusion
> 
> The best battery to use for fast charging using advanced charging systems
> 
> ...


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