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Multi output chargers


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Hi Folks,


I am looking at buying a 30 AMP Victron Blue Smart IP22 Charger but see that they come in either a single output or 3 individual outputs. At the moment we only have a single house battery so a single output would suffice but I am thinking of putting in a second house battery some time in the future so wondered if better to pay extra for the multi output unit. From what I can gather the voltages on the 3 output unit would all be the same so am I correct in assuming all the batteries would receive the same charge voltage? if this is the case would externally splitting the output of the single output unit achieve the same result as the 3 output unit?

The single output is on special for AU$257 at the moment so i'm wondering if worth an extra $70 for the 3 output.




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Hi if by house battery you mean the leisure battery side of your camper, you should link the house batteries together. Otherwise you will end up with batteries at different levels of charge. I have. The same single output charger it's really good. I have a Votronic solar controller with a second output, this keeps the engine battery topped up when van is parked up.
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Wortho - 2018-12-26 3:26 AM


...From what I can gather the voltages on the 3 output unit would all be the same so am I correct in assuming all the batteries would receive the same charge voltage?...


This video-clip relates to the 3-output version of the Victron charger



The review involves three quite different batteries being charged simultaneously and (as far as I can make out) each receives the voltage most suitable to its type and state of charge.


A potential snag with following welted’s suggestion that you link together your present single house-battery with a 2nd house battery purchased in the future is that it is generally advised that best practice is for a multiple-battery ‘bank’ to comprise batteries that are the same type, make, Ah rating and (if possible) are also the same age.


In principle, then, if you are planning to go for a parallel-connected 2-battery system, you should ditch your current house-battery (that, presumably, is not near-new) and install a pair of identical new batteries and - if you did this - the 1-output Victron chager should be OK. However, if you opted for a 2-battery ‘bank’ comprising old and new batteries that possibly also might have a different maker and/or a different Ah rating, it would appear that you’d be better to choose the more expensive 3-output Victron charger now in order to provide future-proofing.


You might try asking about this on the “Victron Community” forum as I notice that there have been a few enquiries about the Blue Smart charger



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Derek Uzzell - 2018-12-26 7:24 PM

The review involves three quite different batteries being charged simultaneously and (as far as I can make out) each receives the voltage most suitable to its type and state of charge.







Thank you both for the responses.

Derek I did come across that video but its confusing that the phone app only shows 1 voltage and 1 output current for all 3 outputs which suggest they are common. I was wondering if it is just the state of charge of each battery that varied the voltages present at each battery rather than the actual voltage(s) differing on each of the charger outputs. I will check out the Victron forum.


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It might also be worthwhile contacting “Battery Works”




as they produced the video.


I notice that 8 months ago there was this comment to the video


"Is each one of the three outputs managed separately? Are these three outputs just to make wiring easier, or is there an advantage? Is there a wiring diagram showing how this would be wired with three batteries? showing loads as well??”


but no reply was forthcoming.

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Just as an aside .......


On a European Motorhome Forum there have been discussions regarding leisure batteries. A concensus seems to have found that one very large Leisure battery lasts a lot longer than 2 matched, smaller ones of roughly equal size in Ah. I neither agree nor disagree with that statement but would be interested in the views of others.

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747, I would tend to believe one large battery of the same Ah rating surviving longer than 2 smaller ones if the battery is heavily used for high discharges, but I have never seen any evidence that states why.


My own theory is that a large battery 'case' allows better flow of the Acid by Convection around the battery plates, keeping the plates in a a big battery cooler. Temperature is a battery killer.


But I also think that smaller solutions rarely have a balanced battery pair.

It has been reported before on this forum, that battery retailers are not always careful to send out batteries from the same batch.

Often the cabling leaves something to be desired as well


Only Alpha Batteries seem to be aware of just how critical the issue is and guarantee to send out matched batteries when ordered in pairs.

Two 90Ah batteies of about 53bs/24 kg are heavy. One large 180Ah battery is really heavy and awkward to manhandle into and out of location.



Wortho, As for multi output chargers, they primarily come from the Marine market, supplying different voltages and currents to independent battery banks.

On a big boat there will often be multiple Alternators supplying independent battery banks for Habitation Area and Starting.

Likewise the mains charging will be required to supply independent charging.

Typically the Starter battery Alternator will be quite small but the Habitation area battery Alternator be several hundred amps.


Usually, the Starter batteries won't discharge much while 'at Sea', but the habitation batteries will need higher voltages and currents.


If you intend to connect the second battery to the engine Alternator on your van using a common Split Charge relay then the batteries will need to be joined resulting in a multi output mains charger being compromised and superfluous.


All depends on what motorhome you have, and the Charger/control electronics installed as to which setup will be the most efficient.







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Alan, I agree with you about cabling issues. When I bought my present Motorhome I asked for a second Leisure battery to be fitted before collection (along with a couple of other jobs). The Dealer had fitted the second battery with what looked like inadequate wiring. When I queried this, they said they used the standard Autotrail wiring harness supplied by Autotrail. I deemed it inadequate and asked for something more substantial and that they remove the 30 amp fuse and replace it with a 20 amp one.


After 4.5 years of ownership I am just about to replace both Leisure batteries with the Yuasa EFB that seem to be a good choice.


ps, I watched a repeat of a Wheeler Dealers programme yesterday in which they did up an old Citroen van they bought in France. Some bloke in Conwy helped them out. :D

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747, That 'bloke in Conwy' didn't just help them out we did the entire van!!!!


We even fitted out the panelling in the rear, marking every thing up like a giant jigsaw so they could dismantle it and 'fit it on the show'. Notice how when he is 'fitting the engine' the rear is screened off?


We did the Paint, rebuilt the gearbox, driveshafts, brakes, suspension, seats, 6 volt to 12 v conversion, modern Halogen bulbs, etc.

We rebuilt the wiper motor and fitted a 'modern' 50 amp Alternator, no space to fit a bigger one and the fan belt drive isn't up to it anyway.


The van left us with the engine already fitted and driving, so Ed could remove it, seeing how it went together, so he could 'install it on the show'.


They promised lots of advertising but we got none. We did it at a big discount on that basis, and it cost us dear. Our cash flow issues went from poor to very bad and we ended up losing the House, the company, the lot.

Very sad.


We have a photo of the van sitting in between two others in the workshop having been stripped to nothing after painting. I will try and find it and post it below along with the finished van driving onto the Wheeler Dealers trailer.




The Hymer and Burstner factories fit a second battery to perfection, even fitting a second charger to cope with the greater load.

However, if you specify a second battery with the Dealer, the Dealers tend to not 'tick the second battery' box on the order form and instead fit their own version of a second battery without a charger and pocket the £200 difference.

They then tell the buyer that it has a 'factory' fitted second battery when it doesn't.


The factory fitted batteries are a world apart from the normally poorer Dealer fitted versions.




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