12V Boat Wiring Diagram

[Mavis]

In your previous thread you said you had tested your batteries by going onto shore power until they were fully charged.
If you haven't got a proper charger - how?
What did you use and for how long?

I keep having to borrow my mates 3 stage intelligent charger from his caravan - Hence the need to get a proper installed one! - Back in August I had it on for 48 Hours and then sailed from Mylar, up and around Falmouth and on to moor overnight in Helford. By the time I got there (4 hrs Max of doodling around) the batteries where down to half charge and I had to fire the engine up so we could have lights for the night.

 

[VicS]

I keep having to borrow my mates 3 stage intelligent charger from his caravan - Hence the need to get a proper installed one! - Back in August I had it on for 48 Hours and then sailed from Mylar, up and around Falmouth and on to moor overnight in Helford. By the time I got there (4 hrs Max of doodling around) the batteries where down to half charge and I had to fire the engine up so we could have lights for the night.

Yo say you have 2 80 Ah leisure batteries (and a starter battery) if your leisure batteries were down to 50% in 4 hours thats an awful lot of current drain. A good few amps even if not quite as much as the 20 amps simple arithmetic might suggest.

It wont be difficult to find something approaching 20 amps! In fact that current could produce enough heat for the fault to find you!

BUT how are you measuring or estimating this 50% drop in state of charge?

 

[Mavis]

Yo say you have 2 80 Ah leisure batteries (and a starter battery) if your leisure batteries were down to 50% in 4 hours thats an awful lot of current drain. A good few amps even if not quite as much as the 20 amps simple arithmetic might suggest.

It wont be difficult to find something approaching 20 amps! In fact that current could produce enough heat for the fault to find you!

BUT how are you measuring or estimating this 50% drop in state of charge?

Hi Vic, I know it all sounds a bit daft but that is what I have been experiencing. I only have a laymans knowledge of electrics and I can only report what I am seeing. From memory the volts on the batterys are over 12.5 after charging and then after a few hours drop down to around the 12v mark. Smartguage reads 60% sometimes 70% after a good charge and then after a few hours gradualy drop down and when it gets to 50% I start up the engine - I can assure you that nothing is getting hot. For interest I will report back after this weekend..

 

[VicS]

Hi Vic, I know it all sounds a bit daft but that is what I have been experiencing. I only have a laymans knowledge of electrics and I can only report what I am seeing. From memory the volts on the batterys are over 12.5 after charging and then after a few hours drop down to around the 12v mark. Smartguage reads 60% sometimes 70% after a good charge and then after a few hours gradualy drop down and when it gets to 50% I start up the engine - I can assure you that nothing is getting hot. For interest I will report back after this weekend..

With a good multi-stage charger you should be able to charge the batteries until they give a volts reading of 12.7ish or more after standing idle for 24 hours. If you cannot get them above 12.6 then either the batteries are "over the hill" or the charger isn't doing the business.
Chargers seem to vary a bit but mine goes into "float" mode once it has charged at a constant current ( selected manually to match the battery capacity) and then at a constant 14.4 volts until the current drops to a value that only it seems to know.

Have you been carefully though the installation instructions for the Smartgauge. Esp noting that it must be directly connected to the batteries and that the wiring for the Smartgauge must not be used for any other purposes.

Have you been through the setting up procedures for the Smartgauge.

I am wondering if your Smartgauge is leading you up the garden path.

Have you been able to check the batteries with a hydrometer, or are they sealed


I am thinking along the lines that your batteries may not be fully charged when you think they are. Maybe because they are duff or simply that you are not getting them fully charged. 12.5 immediately after coming off charge does not indicate fully charged... very far from it.
Falling quickly to 12 volts with no load would similarly indicate that they are considerably less than fully charged. ( or duff)

Compare what you are seeing with the fact that my leisure battery, which is standing on the workshop bench and has not been on charge for several weeks, reads 12.65 volts.
A car battery which I had on charge yesterday pm until the charger went into float mode is now reading 12.82 volts.

 

[Plevier]

i am getting more convinced that your batteries are not being charged fully as i said in the original thread.
When you first connect this charger what voltage do you get at the battery terminals and what voltage ith it still connected 24hrs later?

Quote "Smartguage reads 60% sometimes 70% after a good charge". You mean straight off charge before taking load?

 

[Mavis]

As a general follow up to this post. I had a marine sparky on board today and he has gone through everything and not found any faults with the wiring. He is convinced that one of the leisure batterys is duff, either sulphanated up or just duff and then dragging the other battery down with it so that I have no capacity in the bank. To save messing around it looks like I ought to get two new batteries. He suggested I split this bank with a one or both switch but I feel that I should just keep it simple for now and see if the new batteries solve the problem. Now which batteries should I buy ...........................
Thanks for all your help.

 

[VicS]

I believe you said they were 80Ah leisure batteries.

So presumably replace with two 80Ah leisure batteries unless you feel you need larger or could manage with smaller or just one.

At the end of the day exactly what is your choice .. you'll get almost as many different recommendations as replies.

I think Id do a bit more testing to confirm the diagnosis before splashing the cash though.