# Battery to Battery Charging



## Bigpeetee (Jan 20, 2011)

Hi,

Anyone got experience with battery to battery chargers, Sterling and others make them.

I've got 2x110 AH leisure batteries, I use a 2000w inverter off these to run microwave or even a 1000w hairdryer ( the boss insisted on this particular facility)

As the leisure batts are under the passenger seat/behind the cable to charge is too small to give a decent charge.

There was a higher resistance in the earth, so a heavy strap stopped that, but still getting voltage drop on +ve lead.

Reading around it seems that a battery to battery charger is the answer as it acts like an inverter to boost the charge voltage to the leisure batts therefore giving a better charge.

Anyone got experience of these, any thoughts welcome.

Pete


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## Justin and Jane (Jan 20, 2011)

Hi Pete.

Ive set up a split charge relay in my van' quite easy to set up just run a + & - from ya van batt into the relay then again out to 1 of ya leisure battery! 
it charges at about 30amp when ya lesiure starts to run low! quite handy bit of kit! 
got mine off ebay .


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## Bigpeetee (Jan 20, 2011)

Hi,

I've got a split system on my Kontiki, the problem is if the leisure batt is down a bit there is a voltage drop on the cable and fuse, the starter batt charges up from the alternator and when it's charged enough, the regulator in the alternator backs off the voltage, so the leisure batt doesn't get full supply.

If the leisure batts are trying to draw 10amps and the resistance of the cable and inline fuse is say 0.1 ohms, the voltage drop over the cable is 1 volt, the flatter the leisure batts, the greater the voltage drop, the slower the charge.

these B2B chargers increase the voltage at the far end by the leisure batts and ensure that the batts get the correct voltage to give the best charge then once charged, just give a top up charge.

Of course PV cells on the roof will help the batt not loose their capacity too much, but you are relying on the sun.

We use the van regularly to take our daughter & friend to sing at gigs around the north west, midlands and Wales, hence the need for hair dryers etc.

see Sweet Gossip


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## David & Ann (Jan 20, 2011)

I have mentioned on one of my very earlier posts, that you need 2½ to 3 times Inverter power for any electrical goods. Example: A 1000w hair dryer, you need between 2½Kw to 3Kw for it to function properly without it tripping or blowing a fuse or switch.


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## AndyC (Jan 20, 2011)

B2B chargers are not really meant to compensate for undersized cables!

If I were you I would beef up the charging cables before even thinking about buying a B2B charger.

AndyC


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## NicknClair (Jan 20, 2011)

AndyC said:


> B2B chargers are not really meant to compensate for undersized cables!
> 
> If I were you I would beef up the charging cables before even thinking about buying a B2B charger.
> 
> AndyC


 
Couldn't agree more!!
Have 80W panel, with Sterling pro-combi 1600w Inverter and B2B Charger all connected to a single 270Ah Elecsol Battery. All of this equipment (other than the Solar Panel wiring) is connected together by 50mm Flex cable, to make sure the transfer of power is safe and will do the job intended. 
The b2b and inverter has been transfered from the last 3 vans, as I would never be without it. It has been an ideal piece of kit.


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## Bigpeetee (Jan 20, 2011)

I totally agree with your comments, if you use a 50mm cable, what are you using as a split charger as the current will exceed most of the little relays capability?

Obviously a bigger cable will reduce the volt drop, but even the inclusion of a fuse will mean that the voltage at the leisure batt will be lower than the starter batt, presume that's why you use a B2B as well. 

What current is yours?

I saw an article last summer in one of the mags comparing the various B2B chargers, it's now been recycled!!!

Any views or experience of others.

As far as the hairdryer is concerned, most of the load is resistive so doesn't cause problems with the inverter, still get 220vac output, even with a 1500 dryer, but the batteries get caned too much, instructions, only switch on when actually drying hair!! Or hold head out of window while motoring- didn't go down well!!

Pete


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## Canalsman (Jan 20, 2011)

Bigpeetee said:


> I saw an article last summer in one of the mags comparing the various B2B chargers, it's now been recycled!!!


 
The article appeared in MMM April 2010 issue - I cut it out to keep and to assist in choosing a more capable charger.

I am awaiting the arrival of a CTEK XS 7000 which was recommended.


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## NicknClair (Jan 20, 2011)

Canalsman said:


> The article appeared in MMM April 2010 issue - I cut it out to keep and to assist in choosing a more capable charger.
> 
> I am awaiting the arrival of a CTEK XS 7000 which was recommended.


 
Lol, don't hold your breath on that one. There is still no noises on when it will be available!!
Sterling have been doing the B2B charger for a very long time, with constant R & D to improve the system. They are due to launch some new B2B's called "Pro-Wild", which have built in solar panel regulators, which seem a good idea.

I will use Xmas hols as an example of performance;
-12 deg, heating killed the leisure battery right down to 12.1V. Started Van (Swift Kontiki Fiat 2.8JTD Standard Alternator @ 80A), after 2 mins of initiation time @ idle speed, input voltage @ 14.5V, 34-35A input. After 10 mins - 14.5V, 29.9 to 32.7A. After 30Mins - 14.7V, 42.7 to 44.9A. After 50Mins - 13.7V, 29 to 31A. The drop in Volts was to do with the change of the charging curve as it is a 4 stage charger and not just a regular Split Charge System. After a total run of 1 hour and 5 mins, My Sterling PMP monitor had confirmed a AH return of 38AH. During this time as well as charging, it was that cold that I had to get the heating going again so the B2B was also compensating the consumption of that (and @ -12deg, you can understand that the Heater was running "flat out").
Now the reason I feel this figure is achieved is due to correct cable use and a charger that doesn't simply link parallel to a smaller AH engine battery. Everything is temperature monitored to avoid overcharging/overheating and the sterling can be programmed in for the correct Battery Construction, ensuring the correct charging voltage for your Battery Bank in the "Bulk Charge" mode.
As for the inverter, I still used 50mm cable from the Battery and kept it within 1m. My wife's Travel Hair Dryer will draw 73/75A (@12V) when used with the inverter, the Microwave uses approx 102A (@12V). By having the B2B, it means I can replace the power used very quickly and without a fuss if needed/running short.
I also maintain the use of a good battery computer that gives an AH capacity figure, that way you can judge if you have enough power in the batteries available and when you need to start the motorhome to recharge if required. This also is a good way of seeing how much the Solar panel has put in the batteries rather than how much it is producing!! I am more interested in what I have available at the batteries to be honest. Sterling's PMP, Victron and Alden's Ordijauge are 3 products I would recommend. Not cheap, but the do the job in hand. We formerly did the NASA range, but the Battery percentage counter doesn't reset unless a load is applied, meaning if the Solar Panel had been working all day, you wouldn't know how much it has put back until your draw of power exceeds what the panel is putting in at that given time.
Sorry if all the above has confused in any way, PM if you have any questions.
Rgs


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## Canalsman (Jan 20, 2011)

There's no shortage of CTEK kit - bought mine on Ebay yesterday and it's in the post ...


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## NicknClair (Jan 22, 2011)

Right I getting a tad confused. I thought the post was about B2B charging/ charging without Mains electric, yet a Ctek XS7000 is a mains charger. You are right in that they're are plenty of Ctek "Mains" chargers on fleebay, but the Tread was reference to improving charging from when the engine's running/wild camping?? Or is it just me getting my wires crossed 
Have a read of the spill from Sterling themselves ref B2B charging; 
Sterling Power Products: Battery-to-Battery Charger Information


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## Canalsman (Jan 22, 2011)

nickjvanbitz said:


> Right I getting a tad confused. I thought the post was about B2B charging/ charging without Mains electric, yet a Ctek XS7000 is a mains charger. You are right in that they're are plenty of Ctek "Mains" chargers on fleebay, but the Tread was reference to improving charging from when the engine's running/wild camping?? Or is it just me getting my wires crossed
> Have a read of the spill from Sterling themselves ref B2B charging;
> Sterling Power Products: Battery-to-Battery Charger Information


 
Didn't mean to confuse - the article in MMM discussed mains chargers and B2B ...

I required a charger - the XS 7000 - for use at home, though it could go in the 'van.

The Best Buy B2B device went to the Sterling BBC121250 ...


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## NicknClair (Jan 25, 2011)

The Best Buy B2B device went to the Sterling BBC121250 ...[/QUOTE said:
			
		

> This model has now changed to the BB1245. Still the same product, but the true output max figure of 45A constant. Same piece of kit fitted in the Swift and wouldn't go back to normal split charge relays, not now! Looking forward to a "non hook up" weekend coming, so might be calling on it as usual ;-)


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