Single charger charging 2 batterys ??

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Can a bog standard charger supply charge to 2 batterys in parrellel ?

Also is there any way to rig an automatic switch to flip from one battery to another on regular mode or say by voltage trip ?
 
I don't see why not. I've been doing this, but not leaving it unattended. It's what your alternator does when the 1-2-both switch is set to "both".

One of the various split-charge relays would do the second job - directing charge to one battery, then connecting the second one as the voltage rises.

Can you find a cheap source for split-charge relays?

Tony S
 
Been searching and come up with these ....

http://www.maplin.co.uk/Module.aspx?ModuleNo=37767&TabID=1&WorldID=&doy=6m1

http://www.maplin.co.uk/Module.aspx?Modu...ID=&doy=6m1

with one above from its main site :

http://www.kemo-electronic.com/en/module/m102/index.htm

Now none of them can take full blown alternator - but based on average Halfords Charger from mains ..... may just be the answer .... Looking through all the blurb - no mention of voltage drop across the splitter - so must be relay not diode ???

I think a trip to Maplins is on cards nect time back to UK !!
 
The only problem is the time it takes to charge will increase, since the (limited) current output will be splt between the 2 batteries. If this current is small, say a 10A charger doing two 110Ah batteries, it could even be insufficient to get a proper charge going on flattish batteries.
 
agreed and understood ...

but isn't it that with such a set-up as long as you are regularly topping up alongside - then this shouldn't happen except in rare occasions ....... especially if you use engine for in / out of harbour etc.
Of course if you go extended periods without engine / charging facility - then you run the risk.

My idea is whether the average boat set-up can do it ......... many posts we see on the forums are after ways to keep batterys up and usefully charged. The post here is as to whether a standard charger can supply two batterys. Plus the later addition post of the splitter ....

Now a question - if a charger CAN supply two batterys at same time - why have a splitter as this - why would one be designed ? Seems unnecessary. So I conclude that yes it is posible to charge 2 batterys with one charger - but is preferred to pass through a splitter if possible.

Well I shall be experimenting and at 7.99 for the splitter - nothing really wasted if it fails !!
 
Re: agreed and understood ...

Yes, regular topping up will sort them out. AFAIK, the going rate is to use a charger who's output is a tenth of the Ah capacity, so for a 110Ah battery you should use a 10A charger or more. Eventually that battery will only demand 3 or 4 amps anyway on charge, which will leave an adequate overhead for the other battery to draw the same.

Two batteries in parallel are much the same as one big one. The splitting issue is just to ensure that you protect one of them for engine starting, there is no other reason you need to split. I'm sure you know this already and there are much wiser than me lurking around here!

Pops
 
Re: agreed and understood ...

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Now none of them can take full blown alternator
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Have to disagree.
Just bought some Voltage Sensitive Relays (Dual Sensing - both ways) from Merlin.
They are rated for up to 100amp and cost around £40 plus vat.
 
I am surprised no one has jumped out and said don't use a cheap car-type battery charger. It certainly won't prolong battery life or capacity due to the rate of charging. And as most people say you shouldn't really leave it on unless its a "smart" charger (sterling, adverc etc)
 
Re: agreed and understood ...

[ QUOTE ]


Now a question - if a charger CAN supply two batterys at same time - why have a splitter as this - why would one be designed ? Seems unnecessary. So I conclude that yes it is posible to charge 2 batterys with one charger - but is preferred to pass through a splitter if possible.

Well I shall be experimenting and at 7.99 for the splitter - nothing really wasted if it fails !!

[/ QUOTE ]

In a situation where one battery was pretty well charged up but one was fairly flat, putting them in parallel to charge would cause the charged one to discharge to some degree into the flat one. Personally I cant quite see why that matters since - some heat losses apart, the total amp hours in the 2 batteries will stay the same and the charging time wont alter. Anyway, the charge splitter simply avoids that discharge problem.

In my last boat the 3 batteries were parallelled without a splitter when the engine was running and there were no problems.
 
Hi Dave99 I fear you have been the victim of advertisi9ng hype or electronics snobbery. providing you know what you are doing the cheapest and crudest charger can do very nicely.
The expensive charger will recharge to the max amount in the minimum time in an automatic manner. A crude tiny charger will charge to the max and provided the current is low enough can be left on permanently. So horses for courses.
I would suggest to the poster use of a VSR or 2 additional diodes one in each positive lead (branching from the original +ve lead) (a diode splitter)if he wants isolation of the systems while charging. The voltage from the charger will be reduced by .7 volt but this does not matter as the output voltage of the crude chargers is usually high enough to not matter.
to explain the voltage would be about 18 volts (average while rising higher and lower with the AC cycle) which pulls down with current flow to that of the battery 14volts. As the voltage of the battery rises the charge current will fall but not by much so it still gets charged to absolute full. However because iit will continue to charge when full the current must be so loow that it will not damage the batteries. ie in the area typicallly of 1 amp. olewill
 
amp capability ...

I was referring to the Maplin splitter / regulators which are well below the alternator rating ...
 
Diodes and Car charger ....

I am not so convinced about the need for "Smart" chargers - apart from their ability to charge a battery to nearer 100% than the 85 - 90% that most others do. As I and many are "berth-hopping" boats and never really extended periods away from charge facility - is it really necessary to go the "smart" route ?

Diodes .... I have a diode splitter already on the boat and disconnected it as I do not have battery sensed or smart charging. The voltage drop was too great - and it didn't work at all with the mains powered charger .... I was toying with the idea of cheating the alternator with the diode on the back of alternator to up the voltage .... but not being so hot on alternator construction haven't bothered.
The Maplin splitter seems a much simpler way to go !!
 
Re: Diodes and Car charger ....

I use a cheap charger like this one on my classic cars (MG, Lotus Triumph, etc) to maintain the batteries. One of my car batteries is about 10 years old and still strong.

It says "smart" but its NOT the 3/4 stage as sterling or the like, it just turns off when it gets up to about 13.8 / 14 volts and when the voltage drops due to self discharge it turns on.

I have one keeping my 6 off 105Ah deep cycle batteries charged and its been OK for the last year during my yacht rebuild.

The Maplin one you are looking at it think has a simular action when attached between the halfords charger and the battery.

Charging mult batteries is OK as long as they are of the same type and a slmular age/condition no diodes needed.

In fact a conbining charge relays do infact connect all the batteries together when charging and only seperates when the charging current is turned off
 
relay ...

I got a feeling that this does keep them separate .... but untill I try it - no idea !!
 
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