Is a B2B charger necessary?

dougbobbill

Full Member

Messages
9
I guess this question has been asked before, but I couldn't find any reference to it, so I'd appreciate some guidance. My van has an 80 ah starter battery and 100ah leisure, with no solar. It is a basic 1992 Merc, with no alarms, engine management gizmos etc, no EHU and we do not have onboard fridge or hot water: the leisure battery simply provides lighting and radio but mostly charging our phones, tablets and vapes. The van is fitted with a split charge system with 140a VSR.
We have not had the van long enough to know if this is all we need to keep the batteries charged on any extended trips we may do: last year all was fine but was only short trips no more than 10 days, in the summer, but this year (hopefully) and next we will use it much more, for longer periods. I regularly hear reference to B2B chargers, and my question is should I have one, and why?
Whilst the van is parked up unused at home I use a portable condition charger with crocodile clips to each battery in turn
 

Trotter

Full Member

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1,922
Others will on here soon enough.
My set up uses the Ctek D250. Expensive maybe, but it’s not difficult to fit. There’s a second part you could fit, the . Smartpass, probably not needed.
The D250 will charge batteries at 20a, while the engine is running, driving?
The Smartpass increases that to 120a. Batteries charged in no time. Necessary? Probably not.
 

wildebus

Full Member

Messages
2,532
Others will on here soon enough.
My set up uses the Ctek D250. Expensive maybe, but it’s not difficult to fit. There’s a second part you could fit, the . Smartpass, probably not needed.
The D250 will charge batteries at 20a, while the engine is running, driving?
The Smartpass increases that to 120a. Batteries charged in no time. Necessary? Probably not.
For a 100Ah battery, the Smartpass would not be worth it as the charge current would not want to be very much more than the standalone D250 would provide on its own.

B2B vs VSR - if you are relying on the alternator to charge the battery, then a B2B will do a much better job than a VSR. If you have Solar and are a summer camper, then a VSR will be good enough generally.
For the cost of a B2B, you could setup yourself up with a decent solar setup of an MPPT controller and maybe 150W of Solar Panels. If the choice was one or the other for your budget, I would think about putting the money into solar if a summer camper. If an all-seasons camper and you like to tour around on your time away, then a B2B will give you a better return.
 

dougbobbill

Full Member

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9
Thanks for the input. We will be not quite all seasons (end Feb to end Oct in S Europe) and we do move about so from what you say B2B is preferable to both a VSR and solar. Easy enough to remove the VSR but is the B2B instalation straightforward? I imagine it should be way easier than a solar instalation. What sort of cost is it?
 

mistericeman

Full Member

Messages
205
In our transit we have 2 x 100w solar panels and a Durite 140 vsr charging 3 x 100ah leisure batteries.

We had close on 5 years all year round 98% wild camping and were never short of power even in winter when the solar was doing cock all...
AND all our cooking being electric (microwave /toaster/kettle/slow cooker etc) as well as running a compressor fridge and eberspacher D2....
We do tend to move around each day rather than linger in one spot.

I'd say you'll be fine with a VSR If you move around and aren't heavy on useage.
.... Though on the motorhome I've just fitted a ring b2b/solar controller as I wanted to use a larger 400w panel AND mppt controller rather than the cheapey £20 pwm one I used last time.
 

shortcircuit

Full Member

Messages
56
No expert, but with your energy needs I would only make efficient use of what I had, led lights etc.
 

wildebus

Full Member

Messages
2,532
Thanks for the input. We will be not quite all seasons (end Feb to end Oct in S Europe) and we do move about so from what you say B2B is preferable to both a VSR and solar. Easy enough to remove the VSR but is the B2B instalation straightforward? I imagine it should be way easier than a solar instalation. What sort of cost is it?
A VSR will have the following:
Thick cable from Starter Battery +Ve
Thick cable to Leisure Battery +Ve
Think cable to earth

A B2B will need:
Thickish cable from Starter Battery +Ve
Thickish cable to Leisure Battery +Ve
Thickish Cable to earth (or Battery -Ve. same difference)

So to swap, you just need the B2B itself and another Earth/-Ve cable. Very often the cables will have the same connections between the two devices (6mm ring terminals) so swapping between the two is likely to be fairly easy.

I have used "thick" and "thickish" to describe the cables as installs vary, but a VSR will be using a heavier cable than a B2B, so the chances are a cable used in a VSR install will be ok for a B2B install. you can take a photo and post it up here if you want to check if that is the case in your van :)

Cost wise, there are of course different options. The ones I like and install/supply are the Ablemail 30A units and are around £230 supplied including the extra Earth/-Ve cable you would need. Other models and suppliers are obviously available.
 

trevskoda

Full Member

Messages
1,567
Wild bus is correct but in truth i would leave the relay sys alone and go for some solar and a good mppt regulator in spring to aut,if no tv and just led lamps then a 100w panel and one batt will be ok, all down to cost and use.
 

wildebus

Full Member

Messages
2,532
Wild bus is correct but in truth i would leave the relay sys alone and go for some solar and a good mppt regulator in spring to aut,if no tv and just led lamps then a 100w panel and one batt will be ok, all down to cost and use.
For my own use of my camper and with say £250 available to spend, an investment in a decent Solar setup would trump an upgrade from VSR to B2B :)
 

Trotter

Full Member

Messages
1,922
I guess this question has been asked before, but I couldn't find any reference to it, so I'd appreciate some guidance. My van has an 80 ah starter battery and 100ah leisure, with no solar. It is a basic 1992 Merc, with no alarms, engine management gizmos etc, no EHU and we do not have onboard fridge or hot water: the leisure battery simply provides lighting and radio but mostly charging our phones, tablets and vapes. The van is fitted with a split charge system with 140a VSR.
We have not had the van long enough to know if this is all we need to keep the batteries charged on any extended trips we may do: last year all was fine but was only short trips no more than 10 days, in the summer, but this year (hopefully) and next we will use it much more, for longer periods. I regularly hear reference to B2B chargers, and my question is should I have one, and why?
Whilst the van is parked up unused at home I use a portable condition charger with crocodile clips to each battery in turn
Told you brighter people than me would be along. If Wildebus ( Dave), says solar , then solar it is. Some on here may know as much as him. I doubt if many know more.
 

Trotter

Full Member

Messages
1,922
Is solar out of the question you could get 100w and change from £100
For the cost of a B2B, you could setup yourself up with a decent solar setup of an MPPT controller and maybe 150W of Solar Panels. If the choice was one or the other for your budget, I would think about putting the money into solar if a summer camper. If an all-seasons camper and you like to tour around on your time away, then a B2B will give you a better return.
I think that's what Wildebus is saying here.
To be a little mischevious here. The Ctek D250 is also a cracking MPPT controller.
 

wildebus

Full Member

Messages
2,532
I think that's what Wildebus is saying here.
To be a little mischevious here. The Ctek D250 is also a cracking MPPT controller.
the CTEK is indeed a good unit and does give you Solar as well.
I am going to throw in a caveat though ... almost all the Combo units have a significant limitation on solar, be it the CTEK, the Ablemail Combo, the Redarc and various others and care must be taken when these when choosing a solar panel to use with them.
 

mistericeman

Full Member

Messages
205
the CTEK is indeed a good unit and does give you Solar as well.
I am going to throw in a caveat though ... almost all the Combo units have a significant limitation on solar, be it the CTEK, the Ablemail Combo, the Redarc and various others and care must be taken when these when choosing a solar panel to use with them.
As I recently found out.....

Thankfully you saved me 'letting the smoke out of the wires'

Happy with the Ring rscdc30 so far... Though I've yet to run cables for the engine charging side yet (not much of a problem though while we're on lock down)
 

Trotter

Full Member

Messages
1,922
the CTEK is indeed a good unit and does give you Solar as well.
I am going to throw in a caveat though ... almost all the Combo units have a significant limitation on solar, be it the CTEK, the Ablemail Combo, the Redarc and various others and care must be taken when these when choosing a solar panel to use with them.
By this,do you mean the 300w maximum panel limit of the Ctek.
 

wildebus

Full Member

Messages
2,532
By this,do you mean the 300w maximum panel limit of the Ctek.
It is more the voltage levels than the panel wattage limit. If you were to fit a 24V panel (which is one typically over 160W, but that is not always the case), then that would almost certainly damage the CTEK (and most of these other Combos) permanently. Same if you were to fit a pair of 12V panels and run them in Series.
The thing is when it comes to solar, there are some common themes that spring up repeatedly .... "Bimble Solar have some good value panels, try them" (the ones recommended tend to be 24V panels); "for best results, wire in series"; and "get a controller that is 20A (for example) for that much solar" (so current spec is checked but voltage is not).
None of the above is bad or incorrect advice, but taken in isolation, it could have expensive consequences.

Of all the combo units I am aware of and checked the specs, not a single one are close to taking the voltage put out by a 24V panel (or 2 X 12V in series). A couple are very close to the 12V limit even. The highest voltage I know of for the combo B2B/MPPT is the Ablemail AMS, which is rated at 35V and has a shutoff over 37V (most will not shut off though, they will blow up, and because of shared electrics, blow up the MPPT, you blow up the B2B as well).
 

Trotter

Full Member

Messages
1,922
It is more the voltage levels than the panel wattage limit. If you were to fit a 24V panel (which is one typically over 160W, but that is not always the case), then that would almost certainly damage the CTEK (and most of these other Combos) permanently. Same if you were to fit a pair of 12V panels and run them in Series.
The thing is when it comes to solar, there are some common themes that spring up repeatedly .... "Bimble Solar have some good value panels, try them" (the ones recommended tend to be 24V panels); "for best results, wire in series"; and "get a controller that is 20A (for example) for that much solar" (so current spec is checked but voltage is not).
None of the above is bad or incorrect advice, but taken in isolation, it could have expensive consequences.

Of all the combo units I am aware of and checked the specs, not a single one are close to taking the voltage put out by a 24V panel (or 2 X 12V in series). A couple are very close to the 12V limit even. The highest voltage I know of for the combo B2B/MPPT is the Ablemail AMS, which is rated at 35V and has a shutoff over 37V (most will not shut off though, they will blow up, and because of shared electrics, blow up the MPPT, you blow up the B2B as well).
My panels will be in parallel. 2 x 100w = 1 x 200w. Ctek quote 300w max. Think I’ve got this right 🤓
 

wildebus

Full Member

Messages
2,532
My panels will be in parallel. 2 x 100w = 1 x 200w. Ctek quote 300w max. Think I’ve got this right 🤓
Sounds good :). This is one reason why I like kit like the Victron... The model name tells you the limits! I have the 100/30, which is 100V and 30A. This means I can wire the 4 X 100W panels any way I like and never damage the controller. I've had them in series putting in 90V to the controller, in series/parallel putting in 45V and doubling the current, or could even put all parallel and come closeish to 30A without problems . Kind of foolproof :)
 

Full Member

Full Member

Messages
3,552
It is more the voltage levels than the panel wattage limit. If you were to fit a 24V panel (which is one typically over 160W, but that is not always the case), then that would almost certainly damage the CTEK (and most of these other Combos) permanently. Same if you were to fit a pair of 12V panels and run them in Series.
The thing is when it comes to solar, there are some common themes that spring up repeatedly .... "Bimble Solar have some good value panels, try them" (the ones recommended tend to be 24V panels); "for best results, wire in series"; and "get a controller that is 20A (for example) for that much solar" (so current spec is checked but voltage is not).
None of the above is bad or incorrect advice, but taken in isolation, it could have expensive consequences.

Of all the combo units I am aware of and checked the specs, not a single one are close to taking the voltage put out by a 24V panel (or 2 X 12V in series). A couple are very close to the 12V limit even. The highest voltage I know of for the combo B2B/MPPT is the Ablemail AMS, which is rated at 35V and has a shutoff over 37V (most will not shut off though, they will blow up, and because of shared electrics, blow up the MPPT, you blow up the B2B as well).
This is very sound advice from wildebus - as always!
I have a single 300W Panasonic solar panel which supplies electrical energy at just over 60V (so a current of about 5A if it should ever reach maximum output). This is matched to a Victron 100/20 solar controller (100V max input, 20A max output). When planning your system, as wildebus advises, do plan the system as a whole and make sure all the components (including the cabling) are operating well within specification.

Colin 🙂🙂🙂
 

in h

Full Member

Messages
296
An overall bit of advice: the information you get here from the likes of wildebus is far more reliable and dependable than what the sales staff in the "specialist" suppliers say.
They have a product range to shift, so will favour what they want to sell.
Generally, their knowledge of the products is based on what's written on the box. Few understand the physics.
OK, wildebus sells stuff too, but the difference is that he chooses it on the basis of what's good, not what's profitable.
 
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