Battery charging - idiot's guide needed

[Tim O]

OK.....i will try and explain the facts about my battery system as I understand it and hopefully someone will be able to explain in terms I understand what i need to do to set up charging it.

I have three batteries....I believe 2 are domestic and 1 is engine starter. There are three isolation switches - one labelled Engine, one Crossover, and one Domestic.

There is also a 1-2-both switch.

I am connected to shorepower.

I was told when I bought the boat that you just had to connect a mains charger to the terminals of any one of the batteries as they were "all linked together"

So far, I have had a small (Aldi) "smart charger" connected to one battery which I run overnight every night when I am onboard (I am a liveaboard).

I have always left the 1-2-both switch on Off and the isolation switches as follows Engin Off, Crossover Off and Domestic On.

This seems to have kept the batteries reasonably charged though if i leave lots of lights on or use the water pump a lot then power will have dropped by the next evening when I switch the charger on again.

I have now just purchased a Ctek M300 from another forumite. My questions are...

Do I just connect the charger to one battery...if so, does it matter which?
What configuration should the isolation switches be in, to charge all the batteries?
Should the 1-2-both switch be just left off....that is just for when the engine is charging the batteries via the alternator right???

To me batteries and electrics are a total mystery so please keep advice or questions in idiots language

Many thanks

 

[Tranona]

There seems to be redundancy there. Can't see the need for a 1,2 both switch if you have 2 distinct banks.

The normal set up here would be to have a split charge device such as a VSR or a diode to manage the charge from the alternator, usually charging start first and then the house bank. You do not need to do anything other than switch on the bank you are using - that is the house bank to use the house circuits or the engine battery if you want to run the engine.

For your shorepower it is normal to connect the charger just to the house bank - there is little need for shorepower for the engine battery. However, it is better to have a multiple outlet multi stage charger of decent capacity rather than what you have at the moment. you can then connect to two or even 3 banks so that when you are plugged into shorepower your charger automatically tops up all your batteries without any action from you. For a typical liveaboard battery bank for your size boat an M300 would be suitable, although it would seem to have only one output so wire it to your house bank.

You do not need to have your banks in use when charging, although it is normal to leave the house bank on when on board. You could keep the other charger wired to the start battery through a switch so that you could use it to top that up if you don't use the engine for some time, but really it is redundant. You always have the choice of using the parallel switch to use the house bank to start the engine in an emergency.

 

[VicS]

OK.....i will try and explain the facts about my battery system as I understand it and hopefully someone will be able to explain in terms I understand what i need to do to set up charging it.

I have three batteries....I believe 2 are domestic and 1 is engine starter. There are three isolation switches - one labelled Engine, one Crossover, and one Domestic.

There is also a 1-2-both switch.

I am connected to shorepower.

I was told when I bought the boat that you just had to connect a mains charger to the terminals of any one of the batteries as they were "all linked together"

So far, I have had a small (Aldi) "smart charger" connected to one battery which I run overnight every night when I am onboard (I am a liveaboard).

I have always left the 1-2-both switch on Off and the isolation switches as follows Engin Off, Crossover Off and Domestic On.

This seems to have kept the batteries reasonably charged though if i leave lots of lights on or use the water pump a lot then power will have dropped by the next evening when I switch the charger on again.

I have now just purchased a Ctek M300 from another forumite. My questions are...

Do I just connect the charger to one battery...if so, does it matter which?
What configuration should the isolation switches be in, to charge all the batteries?
Should the 1-2-both switch be just left off....that is just for when the engine is charging the batteries via the alternator right???

To me batteries and electrics are a total mystery so please keep advice or questions in idiots language

Many thanks

Dont know what the 12B switch is doing . Normally one would expect to see either the 12B or the other three.
I could make one or two guesses about how its all wired but they would only be guesses?

Take some time to figure out the wiring of the batteries and the switches and post a wiring diagram for comment, criticism, or condemnation ........................ a diagram, scanned or photographed, but not photos of the wiring !

Only then will anyone be able to advise you how to operate it or what alterations might be sensible. If all the batteries are really connected together they the whole lot does need a serious "sort out"

DO NOT switch anything OFF while the engine is running because if you inadvertently disconnect the alternator while it is charging you will blow its diodes


Meanwhile,

The little Aldi charger is not really man enough to charge several batteries all at once. ( I suspect that the combine switch will allow you to do it though) The M300 should be Ok though

With all the switches at "off" clip it onto the batteries one at a time and charge them separately. You may find that two of them are connected together and will have to be charged like that unless you disconnect them from each other.

 

[Tim O]

As far as wiring diagram goes there is one which came with the boat which i suspect is original...whether it conforms to the reality i don't know but that might be a good place to start......by checking it against what actually exists. Or i will try and draw a simplified version

 

[William_H]

You need to explore the system and a digital volt meter will help you. Check each battery when system is on charge. Both engine alternator and shore power. If all batteries are being charged you will see a rise in voltage on each battery. Then try pos 1 and pos 2 for the 1,2,both switch. This should answer your question with a bit of patience. You can get really cheap volt meters from China such that you could fit one with a rotary switch to each battery or have one for each battery. (but you need to be able to switch them off as they draw current. https://www.ebay.com/itm/Digital-Re...hash=item284f961eed:m:m-sNy1yZJZujdoFEoy7MBJQ olewill

 

[LadyInBed]

Take some pictures of the wiring​ diagram and post them, then we will know a bit more.

 

[PaulRainbow]

Forget the wiring diagram, it's highly unlikely the boat was built with the current switch configuration so the diagram cannot be relied upon. You need to make your own. Is the 1-2-B switch actually connected to anything ?

 

[ghostlymoron]

The first thing I did when I had a boat with proper electrics was to do a wiring diagram. I started with the charging system. You need to do the same. Draw out the batteries, alternator, ignition and distribution switches. Then trace the connections between them. This will enable you to deduce how it works. Maybe display on here for advice.

 

[Tim O]

The first thing I did when I had a boat with proper electrics was to do a wiring diagram. I started with the charging system. You need to do the same. Draw out the batteries, alternator, ignition and distribution switches. Then trace the connections between them. This will enable you to deduce how it works. Maybe display on here for advice.

I'll do that, when I get a chance this weekend.

One thing I have deduced from looking is that one of the two larger house batteries is connected to the other - big fat red cable from positive to positive terminal and big fat black one neg to neg. The only other wire connected to this one seems to be a smaller guage black one coming off the neg terminal and going somehere I havent traced yet...seems to disappear through bulkhead towards engine compartment.

I wired the M300 up to this battery and turned on...BOTH house batteries jumped from showing 12V on my voltmeter to just under 14V.

The engine battery was reading 12V...until I switched the engine isolator and crossover switch to on at which point it also went up to just under 14V

 

[VicS]

I'll do that, when I get a chance this weekend.

One thing I have deduced from looking is that one of the two larger house batteries is connected to the other - big fat red cable from positive to positive terminal and big fat black one neg to neg. The only other wire connected to this one seems to be a smaller guage black one coming off the neg terminal and going somehere I havent traced yet...seems to disappear through bulkhead towards engine compartment.

I wired the M300 up to this battery and turned on...BOTH house batteries jumped from showing 12V on my voltmeter to just under 14V.

The engine battery was reading 12V...until I switched the engine isolator and crossover switch to on at which point it also went up to just under 14V

So your two house batteries are connected in parallel to form one bank. That is what one would hope to see.

You normally have the "house" isolation switch set to ON to feed all your domestic circuits. Hopefully if you switch it OFF you have no power to the domestic circuits. If so then again what you would expect.

When you also set the "engine" isolation switch and the "crossover" switch to ON your house and engine batteries become connected together ( I take it you found that both of them and the "house" battery switch had to be ON in order for this to happen ) Again what you would expect. Maybe only the "crossover" switch has to be on to allow both banks to charge. that would be OK, and common, but not without a drawback.

If you can start the engine with only the "engine" switch ON just about all is as expected. The questions that remain to be answered are how is the charging from the alternator distributed to the two battery banks and just what does the 1-2-both switch do, if anything?

Perhaps the charging is distributed by a diode splitter or by a VSR or by some other device such as a Sterling "Alternator to Battery Charger". It could be controlled manually by the 1-2-both switch but this would be by far the least satisfactory option.

 

[PaulRainbow]

So your two house batteries are connected in parallel to form one bank. That is what one would hope to see.

You normally have the "house" isolation switch set to ON to feed all your domestic circuits. Hopefully if you switch it OFF you have no power to the domestic circuits. If so then again what you would expect.

When you also set the "engine" isolation switch and the "crossover" switch to ON your house and engine batteries become connected together ( I take it you found that both of them and the "house" battery switch had to be ON in order for this to happen ) Again what you would expect. Maybe only the "crossover" switch has to be on to allow both banks to charge. that would be OK, and common, but not without a drawback.

If you can start the engine with only the "engine" switch ON just about all is as expected. The questions that remain to be answered are how is the charging from the alternator distributed to the two battery banks and just what does the 1-2-both switch do, if anything?

+1 to all of that :encouragement:

Perhaps the charging is distributed by a diode splitter or by a VSR or by some other device such as a Sterling "Alternator to Battery Charger". It could be controlled manually by the 1-2-both switch but this would be by far the least satisfactory option.

Tim could narrow this down a little by running the engine and checking those battery voltages again. Hopefully something other than the 1-2-B switch is handling things, if not i'd want to be changing that.

One thing to add for Tim, i wouldn't use the crossover switch to charge the engine battery via shore power, keep that switch for emergencies only.

 

[VicS]

+1 to all of that :encouragement:



Tim could narrow this down a little by running the engine and checking those battery voltages again. Hopefully something other than the 1-2-B switch is handling things, if not i'd want to be changing that.

One thing to add for Tim, i wouldn't use the crossover switch to charge the engine battery via shore power, keep that switch for emergencies only.

I did not suggest that because to fully check what is happening he will need to make the voltage readings with different switch combinations and if he starts switching while the engine is running there is chance of completely disconnecting the alternator from the batteries with dire consequences for the alternator diodes.

I thought the best way forwards would be to concentrate on doing a diagram of the batteries, switches and charging arrangements and then we can suggest some further investigation based on what we learn from the diagram.

 

[Richard10002]

This might be helpful to some, (inc. the OP?):

https://www.canalworld.net/forums/index.php?/topic/95003-battery-charging-primer/