# Battery to battery chargers and a bit more please



## lgbzone (Oct 8, 2008)

Hi

I'm after a bit of advice, i've seen a lot of talk on the forum recently about the battery master type devices and it's caught my attention.

I'm in the following situation; 1 engine battery and two leisure batteries, when driving all batteries are charged by the alternator, likewise all batteries are charged when on EHU (ebl99).

i have an 80w solar panel through a charge controller directly to the leisure batteries and a separate, around 30w, amorphous panel (brilliant by the way) on the dash through a controller to the engine battery.

I've never had a problem with either batteries going flat but would like to remove the panel from the dash for another use, and have the 80w (planning on extending this later) on the roof cover the leisure and engine batteries.

The question is; is the battery master/cak tanks device appropriate, does it complicate things that when on EHU both batteries are charged anyway? could i create a race situation, whereby different charge systems are competing so neither charges?

Question 2 sort of related; a friend has a van, not a camper so there isn't a leisure battery or habitation system, but would like to be able to charge other batteries whilst driving. along the lines of plumbing something in that provides some sort of socket/terminals in the back, that he plugs a lead into that clips onto a battery to charge it. would a battery master type device also be suitable for that or are there other methods? I could be interested in doing something similar in the garage of the motorhome, a sort of place to charge batteries we use for other things.

Sorry for the long post but i wanted to give the bigger picture, any thoughts/advice is appreciated.

Lee


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## ched999uk (Jan 31, 2011)

Easy solution to charge additional batteries is a caravan split charge relay. Should only be a £10 or so. The relay simply charges the extra battery when engine is running.


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## lgbzone (Oct 8, 2008)

Hi ched999uk

Thanks for the reply, is this the type of thing you mean?
< link here >

If so; roughly how does it connect? would this simply have two leads that attach to the engine battery and two for the battery to be charged, or does it connect to the alternator, or something else all together?

cheers


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## DABurleigh (May 9, 2005)

Lee,

"The question is; is the battery master/cak tanks device appropriate,"

Yes.

"does it complicate things that when on EHU both batteries are charged anyway?"

No.

"could i create a race situation, whereby different charge systems are competing so neither charges?"

No.

"Question 2 sort of related; a friend has a van, not a camper so there isn't a leisure battery or habitation system, but would like to be able to charge other batteries whilst driving. along the lines of plumbing something in that provides some sort of socket/terminals in the back, that he plugs a lead into that clips onto a battery to charge it. would a battery master type device also be suitable for that or are there other methods? I could be interested in doing something similar in the garage of the motorhome, a sort of place to charge batteries we use for other things. "

Use conventional split charge but thicker cables the longer the run. You don't want resistance otherwise the charge rate will be low into the leisure batteries.
http://www.motts.org/SPLIT CHARGING SYSTEM.htm

Dave


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## lgbzone (Oct 8, 2008)

Hi Dave

Thanks for the info on question 1, much appreciated.

Thanks also for the link to Clives page, that's not something i'd be comfortable with, but i'll pass it onto my friend.

To elaborate on question 2 a bit; every couple of weeks we go racing radio controlled off road cars, therefore take lead acid batteries to power things such as field chargers for the receiver batteries etc, and engine pre heaters. when we get home we have to unload the batteries and charge them up for next time. what he wants to do is leave the battery in the van so it gets charged by everyday driving, they don't require a lot of charging and trickle charge would be fine as there is plenty of time.

for me i think something like a trickle charger that could be plugged into a cigarette lighter socket (but i can't find one) may be more appropriate  not sure if there's a socket in the garage of the motorhome though :roll:

Thanks again

< edit >
When we race the nito cars the batteries we take are 28ah and usually have about 50% charge left, if i take the brushless/electric; i take a 115 ah battery which comes back about 60% charged.
< /edit >


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## ched999uk (Jan 31, 2011)

I have only fitted one when I installed a tow bar and twin electrics for caravan. If I remember correctly it needs an ignition controlled live and a high current (15amps +) connection to vehicle battery, and a negative. Then basically when ignition is on extra battery is charged. 
Dave's link to Motts.org is a good example but you only need a single relay as you only want to charge a battery not power a fridge as well.

The one you linked to seems OK if a bit complicated. Same things can be had on ebay for £10.


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## lgbzone (Oct 8, 2008)

ched999uk said:


> I have only fitted one when I installed a tow bar and twin electrics for caravan. If I remember correctly it needs an ignition controlled live and a high current (15amps +) connection to vehicle battery, and a negative. Then basically when ignition is on extra battery is charged.
> Dave's link to Motts.org is a good example but you only need a single relay as you only want to charge a battery not power a fridge as well.
> 
> The one you linked to seems OK if a bit complicated. Same things can be had on ebay for £10.


Thanks, i'll have a nosy around and see what i can find

Lee


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## DABurleigh (May 9, 2005)

If you can't see how to remove the fridge relay, here's some others:
http://www.marcleleisure.co.uk/Sund001/SplitCharge01.htm
http://img.photobucket.com/albums/v129/Chrisradioman/Chug Chug part 3/SplitCharge1.jpg

Dave


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## lgbzone (Oct 8, 2008)

Hi again.

Regarding Q1; removing my panel connected to the engine battery and charging that off the leisure battery, I've found a device which seems to do the trick; connects to earth, + on leisure battery, + on engine battery, kicks in at 13.6v, stops if it drops to 12.5v and charges at up to 4amps. thanks to those that replied, i'm going to order 1.

Regarding Q2; as an alternative to a split charge relay that connects to the alternator etc, is there a reason why a device like described above couldn't be connected to the engine battery (in my friends case) or the leisure battery (in my case), and wired with the output to some sort of socket, then when a battery needs topping up a lead can be plugged into this socket, that has clips on it to connect to the battery to charge.

it will only charge when the supplying battery has plenty of life and a battery is connected at the other end, to me (a layman with electrics) this appears easier to install, less of a permanent solution, and limits the amps that could be supplied to charge, which i see as a good thing as there will be times when there isn't a battery to charge connected, and the leads/socket need to be stowed safely.

Any thoughts appreciated.


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## JockandRita (Jun 1, 2005)

lgbzone said:


> clipped.......... I've found a device which seems to do the trick; connects to earth, + on leisure battery, + on engine battery, kicks in at 13.6v, stops if it drops to 12.5v and charges at up to 4amps. thanks to those that replied, i'm going to order 1.


Any chance of a pointer to it please Lee? It wouldn't happen to be the BCM12 listed on Page 81, in the following link would it? CAK Tanks - Electrical

Cheers,

Jock.


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## lgbzone (Oct 8, 2008)

Hi Jock

No it's one that techno linked to in another thread, link below, i think i've just bought the last one, but last time they were relisted in a few days
< link >

I did look at the cak tanks one but i wanted one of these as well so got them from the same supplier.
< another link >

It's actually a good little ebay shop, might be getting a few other things from there if i can get confirmation that what i'm trying to do would work and be safe.

Cheers
Lee


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## Techno100 (May 8, 2010)

Exactly the same as sold by CAK tanks but cheaper

CBE CSB2

CAK tank catalogue BCM12 same CBE unit just using their own stock code


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## lgbzone (Oct 8, 2008)

Techno

You know your electrical stuff; could i use one of these and wire it from the leisure battery to a 120w 12v socket, then occasionally plug a lead into the socket that connects to a battery i want to charge? personally i can't see anything wrong so long as i fuse it etc, but when it comes to electrics; i'm not the brightest 'spark' :lol: 

Lee


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## JockandRita (Jun 1, 2005)

lgbzone said:


> Hi Jock
> 
> No it's one that techno linked to in another thread, link below, i think i've just bought the last one, but last time they were relisted in a few days
> < link >
> ...


Hi Lee,

It's exactly the same item that DABs (and my link) was advising you about, albeit a modern version, however, you appear to have purchased it at a substantially reduced price. Well done. 
It's a piece of cake to install, and it is very efficient at what it does. :thumbright:

I have to admit, I have never considered the need for a lockable case for the Euro Plug connections. :wink:

Cheers for now,

Jock.


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## Techno100 (May 8, 2010)

In theory it should work fine


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## lgbzone (Oct 8, 2008)

JockandRita said:


> lgbzone said:
> 
> 
> > Hi Jock
> ...


Hi Jock

Yes, sorry about that, i actually missed the link when i first read your post.

Thanks for the feedback on installation.

It's not the locking bit i'm interested in, it's the waterproofing, to hook up at home i have join two leads.

Cheers mate.
Lee


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## lgbzone (Oct 8, 2008)

Techno100 said:


> In theory it should work fine


Thanks Techno, it's appreciated.

What about in reality :wink:

Cheers
Lee


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## DABurleigh (May 9, 2005)

It will work in reality too. 

That said, it has three disadvantages compared to a conventional split-charge relay:
1) Much more expensive

2) You have lost the functionality that you will only be taking juice from your main vehicle battery when the alternator is charging it

3) You have severely limited the charge current to your battery. My point about thick cables for long runs is significant. It takes a long while to fully charge a depleted battery and you want as much current as you can get.

Dave


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## leseduts (Jun 3, 2008)

Could anyone one tell me how I would know if when on EHU my vehicle battery is being charged as well as my leisure batteries. 
I have a 2005 Geist on a Mercedes and the hand book is not very helpful.


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## DABurleigh (May 9, 2005)

Buy a £5 multimeter from Maplin and measure the voltage across the battery.

About the best motorhoming investment you can make.

Dave


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## Techno100 (May 8, 2010)

http://www.ebay.co.uk/itm/2-WAY-SOL...UK_Gadgets&hash=item19cdcc2575#ht_2524wt_1392


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## lgbzone (Oct 8, 2008)

DABurleigh said:


> It will work in reality too.
> 
> That said, it has three disadvantages compared to a conventional split-charge relay:
> 1) Much more expensive
> ...


Hi Dave

Thanks again for your input.

I think the expense is okay, the unit will cost me 19.99 and the conventional relays i saw at the time, i didn't look too hard, were around £12.00, but seem more complicated to install for me as i have very little experience with auto electrics.

In my case the source battery would be the leisure battery, i may have this wrong but i assumed the new socket (charge point), would only really have power when either the alternator is running, or the van is on hook up, due to the relay only working when the source battery is at 13.6 volts. i do however intend to put a small illuminated switch next to the charge socket so i can see when it has power, and have an element of control over it.

It does limit the charge current to 4 amps and i would prefer it a little higher, maybe 6 or 8, but i hoping 4 will be enough as the battery to charge will be small, about 28ah, and it normally only needs topping up and would have 2 weeks to charge before being used again.

<edit>
If i was installing it to charge a battery that was permanently in the van, like a leisure battery, i would definitely be looking at getting a conventional split relay system installed, i think i'm in a slightly quirky situation.
</edit>

i've made a note to look into what wire will be required once i know the length i'll need, i'll definitely research it and probably post again for advice or confirmation once i think i've got an idea.

Dave; thanks for raising the points as it makes me think about what i'm trying to acheive, if you see any holes in my theory please let me know.

Cheers
Lee


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## lgbzone (Oct 8, 2008)

Techno100 said:


> http://www.ebay.co.uk/itm/2-WAY-SOLAR-SPLIT-CHARGE-RELAY-6-24V-20Amp-VOLTAGE-SENSING-RELAY-/110826890613?pt=UK_Gadgets&hash=item19cdcc2575#ht_2524wt_1392


Thanks techno, it's an interesting device, the only drawback seems to be that it doesn't monitor the source for low voltage, the company that make it, Kemo, do however make a device for that called a 'battery guard'.

cheers
Lee


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## lgbzone (Oct 8, 2008)

Well the CSB2 arrived today, along with the waterproof hookup cable joining thingy, have to say i'm really pleased with how quick i got it, they stated 5 to 7 working days and it was far quicker.

The CSB2 is going to be used in the conventional manner to supply the engine battery from the leisure battery when the solar is working, unfortunately i won't get to install it for a while due to other commitments, however; i did have a peak at the van and it's raised a question.

There doesn't look to be anywhere under the bonnet to fix it and i couldn't recognise the existing split charge relay, (i believe this is a good place to do it), so i'm thinking about inside the van.

Can the negative on the CSB2 connect straight to the negative on one of the batteries?

Can the leisure battery positive on the CSB2 connect to the terminal on the solar charger that goes to the positive on the leisure battery, or is that wrong? like that would the CSB2 see the voltage from the solar not the voltage from the battery, or will those voltages always be the same as they are already connected by a piece of wire. am i making any sense :? 

Many thanks
Lee


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## Techno100 (May 8, 2010)

Yes that is fine and the output voltage at the regulator will always read the same as the battery


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## lgbzone (Oct 8, 2008)

Thanks Techno


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## lgbzone (Oct 8, 2008)

Thanks to everyone for their input, i got a spare couple of hours the other day and had a go at implementing a charger in the garage using a CSB2, seems to work no problems.

< link >


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