# 3 stage battery charger



## orian (Mar 26, 2009)

My motorhome was supplied with the Bonus CTSAN/18A leisure battery charger. It can be used in either float mode or 3 stage. I think (difficult to see without removing it) it has been set to float mode. My understanding is that it would recharge my battery quicker on 3 stage mode.
However, I believe the wiring is different for each mode and I am concerned that if I switch to 3 stage mode I might do some damage. Any electrical expert out there?


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## orian (Mar 28, 2009)

Well this has certainly puzzled more than a few.
I think the answer might be that the 3 stage charger can be used if the wires between the charger and the battery can carry the 18 amps produced by the charger. Anyone got a different view?


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## oldiebutgoodie (Mar 28, 2009)

Having just googled your bonus charger and got no results it's not surprising you have had no response - no one knows what it is!
It would be very odd if it is a professional factory installation that they didn't use the requisite size of cable for both modes. What makes you think that the wiring would be/is different for each mode?


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## orian (Mar 29, 2009)

oldiebutgoodie said:


> Having just googled your bonus charger and got no results it's not surprising you have had no response - no one knows what it is!
> It would be very odd if it is a professional factory installation that they didn't use the requisite size of cable for both modes. What makes you think that the wiring would be/is different for each mode?



Thanks for replying.
Here is a link to the charger:https://sslrelay.com/s113419701.one...92d978dd/shopdata/product_overview.shopscript then search for CTSAN/18A
I have subsequently been told by a motorhome supplier that 3 stage requires better wiring normally found in more recent motorhomes. It seems 3 stage pushes higher amperage to the battery unlike float mode which is like a glorified trickle charger.
I checked the thickness of the wires leaving the charger and they look like the sort that could carry 25 amps so I have taken the plunge and changed the setting to 3 stage. No fire or smouldering cables some 5 hours later.
I think manufacturers should give better guidance on this matter. I telephoned Autosleepers and they thought it was an interesting question but did not know the answer. They refereed me to Bonus (charger manufacturer) who could not answer as they do not have a technical department in the UK.
I will be away in the motorhome for a few days and will update if there are any problems.


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## oldiebutgoodie (Mar 29, 2009)

Found a thread with some info as someone was querying the operation of their charger here motorhomefacts
If the wiring is substantial it seems as though it has been installed correctly. It would be very unusual for someone to wire up a charger for a trickle charge of <1 A as opposed to the full 18A that the charger is capable of. If there is any warmth in them I would uprate them to something bigger (just a quick unscientific test that gives an indication). It seems strange that it is always set up to float as opposed to 3 stage as the 3 stage finishes as float when it has finished! Maybe it is designed more for caravans that are left on hookup for weeks on end?


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## orian (Mar 29, 2009)

oldiebutgoodie said:


> Found a thread with some info as someone was querying the operation of their charger here motorhomefacts
> If the wiring is substantial it seems as though it has been installed correctly. It would be very unusual for someone to wire up a charger for a trickle charge of <1 A as opposed to the full 18A that the charger is capable of. If there is any warmth in them I would uprate them to something bigger (just a quick unscientific test that gives an indication). It seems strange that it is always set up to float as opposed to 3 stage as the 3 stage finishes as float when it has finished! Maybe it is designed more for caravans that are left on hookup for weeks on end?



Thank you for your reply. I am about to leave home for a couple of days but I will certainly read the link you provided.


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## Tony Lee (Mar 29, 2009)

There are some who are concerned that while using your unit as a fixed 13.7V power supply (which is basically what it is in float mode) is pretty much guaranteed NOT to cause problems with 12V TVs and similar equipment, or shorten the life of filament globes, running it as a three-stage charger ( where the voltage should get to 14.4V and remain there for an hour or two, or worse, run an equalise cycle where the voltage can get to close to 15V) MAY damage some equipment not really designed to operate in real-world-RV.
The main things people are worried about are small TVs that have a 240 to 12V plug pack to supply them. In this case, sloppy designers or penny-pinching manufacturers may not make them robust enough to handle any more than 12V plus 10% - say 13.5V. Then again, most people don't know there might be a problem and just do it anyway. Those who claim a problem might be just unlucky and it would have blown up at home running from the plugpak.

The other side of the coin is that running the unit permanently on float mode may not be the best for the battery, whereas running it as a three-stage will ensure that the battery IS kept in good condition.


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## orian (Apr 13, 2009)

I decided to take the plunge and switch to three stage mode because I want the best charge for my battery. So far it seems to have worked without problems.
My battery is fairly new and we have just fitted a 65w solar panel which adds to the charging power of the alternator. Apart from charging at home we only use EHU in winter so it could be a long time before the system is fully tested. Thanks for your help.


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## nichodia (Apr 16, 2009)

Hi there,
I find this thread very interesting as I have just bought this charger from magnum motorhomes. In the box there are two different wiring diagrams, one for use as a float charger and one for use as a three stage charger. Now if I can copy the diagrams and figure out how to put them on here I will, perhaps then somebody could suggest which would be the best mode to install it in.
Di


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## Deleted member 5816 (Apr 16, 2009)

*3 stage charger*

Orian 

How did you get on ? my Symbol has the same charger and I have thought about changing the setting on it

Regards Alf


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## orian (Apr 16, 2009)

Alf 1 said:


> Orian
> 
> How did you get on ? my Symbol has the same charger and I have thought about changing the setting on it
> 
> Regards Alf


No problems thus far but the system has not been really tested because the solar panel has kept the battery fully charged. I hope to go away in the near future but I don't know whether we will be on EHU. Sorry I can't be more helpful at this stage.


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## The Meerkat (Jun 17, 2009)

orian said:


> I decided to take the plunge and switch to three stage mode because I want the best charge for my battery. So far it seems to have worked without problems.
> My battery is fairly new and we have just fitted a 65w solar panel which adds to the charging power of the alternator. Apart from charging at home we only use EHU in winter so it could be a long time before the system is fully tested. Thanks for your help.



Likewise Orian

I also had the Bonus Plug in Systems charger fitted as well and last week decided for an upgrade for the new season, I opted for 3 Stage 18 Amp Amperor Battery charger, I purchased it via the E-Bay channel and saved £10 at the same time using the best offer function

Amperor Battery 18 Amp Charger

MK


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