Help needed with Battery Charging Please

[Matt341]

Hi All, I want to upgrade the charging system on the boat but I have some questions which I am unsure of.

Firstly, I have 2x110ah batteries, the positive on one has a lead on it and the negative on the other. The are connected with a wire from the positive to the negative. This is how the boats was wired when we had it and I have always kept it like this but just to confirm this is ok ?

Next, I have a solar panel fitted on the coachroof which is connected to a regulator and the wires then go back to the batteries and into the terminals, one on the negative and one on the positive of the other battery.

The boat has a battery charger but it is quite old so I don't want to use it. The wires that pass the charge to the batteries are then also connected up to the terminals one negative other positive on other battery. I was told by someone in the business that the charger will cause the alternator diodes to burn as there is nothing stopping the current from flowing back to the alternator ?

Your thoughts and help would be greatly appreciated!

 

[nimbusgb]

Thoughts

1 - You have a 24 volt electrical system.
2 - Bulls**t. The diodes do EXACTLY that, they stop current flowing in a reverse direction. ( you may need some additional blocking diodes to protect the regulator however, but I strongly doubt it )
3 - Just because a charger is old doesn't mean its no good!

 

[Matt341]

Thank you for your reply, i'm glad you have re assured me about the diodes because I thought it was a load of cr*p as well.

My only concern now is that you mention the 24volt system, is this caused by the batteries being shared ? Do I need to worry about this? I have seen chargers on sale in Lidl for £12 which seem to be excellent value for money, would this be able to charge both batteries ? Could I just wire these into the circuit also, positive into positive on one battery and negative into other battery?

My next question is, all the controls for the battery and regulator is in the quarter berth, a couple of metres away from the battery, if I put the charger here as well so I could view the settings etc. could I then extend the cables to reach the battery or do they have to be close to each other ?

I hope this is clear

Many Thanks

 

[Salty John]

It is unusual to have a 24 volt system on a relatively small boat. If the batteries are wired in series, as you describe, then this is what you have - 24v, 110amps. If the two negs and the two pos's are wired together you have the batteries wired in parallel and this would give you 12v, 220 amps - a much more typical installation.
If the two negs are connected together and then the pos's are kept separate, going to each side of a battery switch, then you have two 12v x 110v banks. This is also a common set up. One battery would be designated for battery starting and the other to 'house' duties. The battery switch would have a 'both' position that would enable you to put both batteries together to assist starting the engine if you have depleted the batteries too far for one to do the job.
I wouldn't use a cheap automative charger and certainly not wired into the system.

 

[earlybird]

[ QUOTE ]
It is unusual to have a 24 volt system on a relatively small boat.

[/ QUOTE ]
Just a thought, The OP didn't actually say they were 12v batteries, might just be 6v. each.

 

[Matt341]

Hi John, Thank you for your reply. I am now unsure of the setup. We have owned the boat for 12 years and I still can't remember what the battery set up is lol now you have given all the options though I am pretty sure it is parallel.

Can I also ask about wiring the charger into the system, what is the reason for not doing this ?

Any suggestions on a suitable charger would be great. I forgot to mention that it will also be used when staying on board for lights, water etc.

Thanks

 

[Matt341]

Hi Earlybird, Sorry I missed your reply as i was typing a reply for John.

The batteries are definitely 12volt each. I am pretty sure they are wire in a parallel.

Thanks

 

[Tranona]

You still do not say if you have any split system, that is with a 1-2 -off system so that one serves as an engine start and the other for the house with the possibility of using the house to start the engine if the engine start is down. If you do not, then this is the first thing to look at and there are various ways of doing it - popular now is using a VSR and dedicated switches, for example from Blue Sea available from Merlin. There are others, but these will give you an idea.

Re charger. Something from Lidl for £12 is an absolute waste. A proper staged marine charger of 25 amps is nearer £200 if you are going to wire it in. It is possible to use a cheap car battery charger on one battery but their output is low and they are not intended for permanent use. Suggest you visit the websites of supliers such as Merlin and Barden among others to find out more about the possibilities.

 

[Salty John]

I'm not familiar with the battery chargers available in the UK but I'm sure others will be along to make suggestions.
A marine battery charger is used in a more dangerous environment that a car battery charger so they are built to minimise the risks in marine use.
The most important factor is the isolation of the incoming 240v AC side and the DC output side inside the charger. This prevents stray currents which can be both a shock hazard and a corrosion hazard.
Also, a marine battery charger should stop charging when the battery is full and not continue to trickle charge as some automative type chargers do. There is a danger of damage to the batteries if they are continuously overcharged for long periods, even if only at trickle-charge levels.
A good marine charger and a 'smart' regulator for your alternator should be high on your wish list if you want a good charging system.

 

[Matt341]

Thank you both for your replies!

No we don't have a split battery system, the engine starts off both and also the interior supply comes from both batteries. Not ideal as we can often flatten both by leaving the fridge on and then have to rely on the solar panel to provide enough charge to start the battery. It would be great to be able to keep one battery for starting the engine.

How would the solar panel wire into this system though ? Woule it still be able to charge both batteries?

As for the charger - safety is the most important thing on a boat so I want it to be done as best as possible - obviously a charger for marine use would be the best option - something like this https://sslrelay.com/s74222713.oneandone...ndex.shopscript

Thanks

 

[morgandlm]

I have followed this thread with increasing confusion. You really need to decide what you want to do and get your thoughts organised. You describe a set-up that appears to involve batteries connected in series (ie 24 volt) but then say that you think the batteries are in parallel (I suspect they are in parallel). Then you say you rely on a solar panel to charge the batteries when you have flattened them - then you ask how to connect up a solar panel. You appear to be confused about a boat you have owned for 12 years and you've managed to confuse me.

First of all, establish what your set-up is at the moment and then decide what you want it to do and how best to achieve that.

Separating the two batteries either electronically or by a 1-both-2-off switch into an engine start battery and a domestic supply battery would seem to be an important step. If you have a large domestic use then you probably need some additional battery charging and this can be via a plug-in separate mains powered charger or by one permanently installed into the system to use shore power for battery charging and perhaps for domestic use when berthed.

You have found the Sterling web-site and there you will find a lot of information about options for setting-up a boat installation.
Morgan

 

[Matt341]

Hi Morgan, Im really sorry about the confusion. Firstly I thought the batteries were connected up in a series therefore 24volt, I then realised my mistake as they are connected in parallel circuit. Next the solar panel, we have had it on the boat for 3 years, and it has always charged both batteries equally. But then I wondered how I would wire it up if I had a selection switch - would it charge both or would it only charge the domestic battery.

Thanks

 

[Conrad]

I would get someone in to do it for you, money well spent if you're not sure what you're doing.

 

[Tranona]

Suggest you get a quote from Merlin for a Blue Sea sytem. They will spec it up for your boat and supply all the bits. If you have room you could fit a dedicated start battery such as an Odyssey which is small and can be mounted in any orientation. Then you will have 2*110 as service batteries. As to charger a 20 amp 3 or 4 stage with isolated outputs would do for permanent installation if you are on shorepower.

 

[00Si00]

I use a plug-in, £20 8amp car charger for my setup- not a fancy 3 stage marine charger at all, and this works very well indeed.
I would consider saving your money and buy a book about basic boat electrics instead, and learn how to do the work yourself. Its actually not that complicated.

12 volt bible

Simon

 

[Matt341]

I spoke to a yacht electrician today to confirm my plans. I also went down the boat to clear up my head as to the battery circuit. It is definitely a parallel circuit. Currently with the solar panel connected into the terminals.

My only decision now is to find a battery charger that will maintain the batteries and also have enough power for the domestic items such as lighting etc.

I have had some experience with electrics as my father is an electrician so all work will be checked by him.

Another question which will probably sound stupid to some of you is, what does the amp of the charger refer to, I pressume the higher the better? The amp is the output of the charger?

Many Thanks

 

[Matt341]

Simon, that sounds ok and isn't as expensive as the others. Would that 8amps be capable of charging 2x110ah batteries?

Also, where did you get it from ? And what make is it ?

Thanks

 

[00Si00]

Bought it from here
web page Screwfix
I find charging each battery individually the best way to go and I wouldn't leave the boat with the charger plugged in.
For more information on a similar post not long ago, click here
/forums/images/graemlins/smile.gif
Simon

 

[halcyon]

You need a 20 amp charger for that size bank. A proper 20 amp, not what the cheap chargers quote, which is a peak RMS, a 8 amp one would be around 4 / 5 amp if rated correctly.

If you fit a bi-directional split charge relay, with a simple charger and solar panel on the service bank.

Tha engine will charge the service battery.

The mains charger / solar panel will charge the service battery, then the engine battery.

A correctly rated relay unit will also allow you to use it to link the engine to service battery for emergancy starting.

Brian

 

[Matt341]

So an 8 amp wouldnt be up to the job of charging both at the same time ?

My main object is 1) to be able to charge up if staying on board and using high drain. 2) To be able to give the batteries a boost over the winter when the engine isn't being used.

Would this charger be underrated for such a task?

Thanks