Charging leisure batteries effectively

[tommyleyland]

Ok so I'm looking at getting a 30amp charger for my generator. This might be a stupid question but can I plug the inverter in to the hook up socket and plug the charger in to the inverter, just so I can use 240 on the boat and charge the batteries at the same time or is that an extremely inefficient way of charging the batteries?

[Theo]

Ok so I'm looking at getting a 30amp charger for my generator. This might be a stupid question but can I plug the inverter in to the hook up socket and plug the charger in to the inverter, just so I can use 240 on the boat and charge the batteries at the same time or is that an extremely inefficient way of charging the batteries?

 

That's the best way as long as the generator can stand the load of the charger added to any other loads that you switch on on the boat. By doing it that way you won't need to have the inverter switched on.

 

If you have big loads then plug only the charger into the generator and run the inverter. This means that the batteries will act as a buffer but charging will be slower until you reach the stage when the current is falling off.

 

N

[ditchcrawler]

 

That's the best way as long as the generator can stand the load of the charger added to any other loads that you switch on on the boat. By doing it that way you won't need to have the inverter switched on.

 

If you have big loads then plug only the charger into the generator and run the inverter. This means that the batteries will act as a buffer but charging will be slower until you reach the stage when the current is falling off.

 

N

Why would he want to plug an inverter into the mains and then a charger into the inverter?

[tommyleyland]

I don't have a charger wired in to the hook up socket, I was hoping to be able to plug the inverter to the main hookup socket and charge the batteries at the same time.

Alternatively, can I plug the charger straight in to the generator to charge the batteries? It's a Honda EX1000 generator with a 30amp charger.

If I don't have the inverter on, there won't be 240v going to any sockets to plug the battery charger in to right?

[ditchcrawler]

I don't know how your boat is wired up but the normal way to do it would be a lead from your generator to your 240 inlet point on the boat, normally a blue 16 amp round pin plug. This in turn would be connected to your 240 volt outlets through out the boat. You would connect the battery charger to the batteries and then plug it into one of your 240 volt sockets. You shouldnt need to use the inverter at all.

[tommyleyland]

Ah ok I'll check. For some reason it looks like the sockets run off the inverter but that might just because I can't follow the wiring to everything. I'll check this in the morning

Hmmm one thing I've read is I need to switch the "transfer switch". I'm not positive if I have one. There's one black switch by the batteries which I'll try as it must run from the hook up point otherwise I don't know why they'd fit it.

[ditchcrawler]

Ah ok I'll check. For some reason it looks like the sockets run off the inverter but that might just because I can't follow the wiring to everything. I'll check this in the morning

Hmmm one thing I've read is I need to switch the "transfer switch". I'm not positive if I have one. There's one black switch by the batteries which I'll try as it must run from the hook up point otherwise I don't know why they'd fit it.

There may not be one. Some setups they plug the boat 240 volt circuit into the inverter or into the shore supply connection. Have you got a 240 volt circuit breaker and a RCD trip ?

I am off to bed now and may not be back until tomorrow night, depending on weather so hopefully some one else will be along to help. Two things you dont want is the generator and the inverter trying to feed the 240 volt ciurits at the same time or a battery charger plugged into an inverter trying to charge the battery that is powering the inverter.

[Richard10002]

If the charger has an ordinary 3 pin 240V plug, without being able to see the system on the boat, you could just plug it into a 240V socket on the generator, and it should be fine.

 

The worry with plugging the charger into a 240V socket powered by the inverter is that you would be charging the batteries from the batteries - which wouldnt seem right to me.

[bottle]

Hi Tommy

 

There at least two ways your boat may be wired.

 

The below does not include some of the bits in-between those items mentioned it is just to give you some idea and what to look for.

 

1.

There is a plug fitted to the outside of the boat where the shoreline/ generator connects, this goes to a changeover switch that connects either the shoreline/ generator or the inverter to the 240v system of the boat.

 

2.

There is a plug fitted to the outside of the boat where the shoreline/generator connects, this goes to the inverter that automatically changes from the inverter to the shoreline/generator to supply the boat.

To know if your inverter does this you will need to check the specification and listen for a switch/relay operating when the shoreline/generator are switched ON.

 

Do not at any-time use a charger if there is not a shoreline or generator connected and running.

[tommyleyland]

Ok brilliant. So grateful for all the great advice, I'm nearly there. I've got the smart meter installed and the generator is ready to go, under nicknormans advice I got a 45amp charger from the website he suggested and it's on the way.

 

Then it's just a case of plugging her in and charging up the batteries until full

[ditchcrawler]

Ok brilliant. So grateful for all the great advice, I'm nearly there. I've got the smart meter installed and the generator is ready to go, under nicknormans advice I got a 45amp charger from the website he suggested and it's on the way.

 

Then it's just a case of plugging her in and charging up the batteries until full

And no inverters running

[tommyleyland]

And no inverter running

[tommyleyland]

Oh and am I ok plugging the charger straight in to the generator? As a moment of being a moron I plugged in an extension lead, obviously a shitty house one and it fried it. I'm aware it's my fault, Just want to cover everything before plugging in an expensive charger

[nicknorman]

Oh and am I ok plugging the charger straight in to the generator? As a moment of being a moron I plugged in an extension lead, obviously a shitty house one and it fried it. I'm aware it's my fault, Just want to cover everything before plugging in an expensive charger

Yes should be OK. Please be careful not to have the genny on the boat or where carbon monoxide from the exhaust can get into the cabin. People die from this every year. If you do use an extension lead on a drum, always fully unroll it otherwise it overheats.

[Graham.m]

You can't tell the state of charge of batteries by looking at the voltage whilst on charge, or the voltage shortly after charging is stopped. If you want to know when you batteries are charged (ie when to stop charging) the only ways are:

 

Fit a battery monitor (eg Smartgauge) Or BMV 702

 

Measure the current going into the batteries whilst charging (batteries are full when the current is down to an amp or two.

 

Measure the specific gravity of the cells (messy and inconvenient) But the most accurate and does not need waiting for surface charge to die

 

In the short term you could get a DC clamp meter such as a Uni-t UT203 (Maplins, or cheaper on eBay) which you can put over the charging lead to measure the current. It's a bit inconvenient to do this each day but it will give you a good idea of what's going on, and they only cost about £30

[tommyleyland]

Yeah I've read up on safety. I'm always going to run it on the towpath but safely out of the way.

Is running it on the back deck bad practice too? There's an engine room between that and our living space.

[Graham.m]

Gents remember the battery temperatures. My guess is they will be down in the 2-5C range and I suggest that will reduce the charge they will take and the voltage they will handle

[nicknorman]

Gents remember the battery temperatures. My guess is they will be down in the 2-5C range and I suggest that will reduce the charge they will take and the voltage they will handle

??? no, the optimum charge voltage increases at lower temperatures.

Yeah I've read up on safety. I'm always going to run it on the towpath but safely out of the way.

Is running it on the back deck bad practice too? There's an engine room between that and our living space.

If it's a petrol genny, there are issues with petrol vapour collecting in the bilges so avoid refuelling it etc on the back deck. I think the advice is to not run it on a deck but I suppose if you keep the doors closed and take into account the wind direction it might be OK.

[Loafer]

Yeah I've read up on safety. I'm always going to run it on the towpath but safely out of the way.

Is running it on the back deck bad practice too? There's an engine room between that and our living space.

 

Running on the back deck is not recommended by BSS, 'cos CO can get into your 'rear vents' (Whooooo)

 

I do though, but only during normal hours. Not while asleep!

[nicknorman]

Fit a battery monitor (eg Smartgauge) Or BMV 702

 

Not really, the trouble with a BMV is that it doesn't give the actual SoC, only a theoretical one based on a notional battery capacity. Thus the indications can be very misleading. Some friends had such a meter fitted. Some time later they phoned me up to say that, whilst the SoC was showing 80%, the lights were dim and pumps not working, with a voltage of 10v. Of course the batteries had gradually lost capacity but the BMV happily showed them what the SoC would have been had the batteries still been new. Not much use really! Edited November 21, 2015 by nicknorman

[by'eck]

 

Running on the back deck is not recommended by BSS, 'cos CO can get into your 'rear vents' (Whooooo)

 

I do though, but only during normal hours. Not while asleep!

 

 

Can confirm that when operating suitcase generator outside on well deck with saloon doors closed, there was enough CO ingress to trigger alarm in central bedroom of 60 foot boat.

[Paul C]

Not really, the trouble with a BMV is that it doesn't give the actual SoC, only a theoretical one based on a notional battery capacity. Thus the indications can be very misleading. Some friends had such a meter fitted. Some time later they phoned me up to say that, whilst the SoC was showing 80%, the lights were dim and pumps not working, with a voltage of 10v. Of course the batteries had gradually lost capacity but the BMV happily showed them what the SoC would have been had the batteries still been new. Not much use really!

 

If you invest a little time into learning how electricity works, the BMV702 can me a useful tool - and given it has an ammeter, I'd say its slightly more useful than a Smartgauge. Not realising that the capacity of batteries falls with age/cycles is a fairly basic error. Had they read the other readings in addition to the SoC, more frequently, they'd have seen a low voltage much sooner than the 10V observed, correlated it with (say) 85% SoC, and realised that something wasn't right.

 

Also don't forget that the Smartgauge doesn't give "actual" SoC - it gives its estimate of SoC - which admittedly if you don't set the battery capacity on the BMV702 correctly, will be closer to the actual SoC. There are scenarios where the Smartgauge representation of SoC is inaccurate.

[by'eck]

Not really, the trouble with a BMV is that it doesn't give the actual SoC, only a theoretical one based on a notional battery capacity. Thus the indications can be very misleading. Some friends had such a meter fitted. Some time later they phoned me up to say that, whilst the SoC was showing 80%, the lights were dim and pumps not working, with a voltage of 10v. Of course the batteries had gradually lost capacity but the BMV happily showed them what the SoC would have been had the batteries still been new. Not much use really!

 

Doesn't your shunt based Mastervolt monitor automatically adjust for capacity or is that just CEF?

[nicknorman]

If you invest a little time into learning how electricity works, the BMV702 can me a useful tool - and given it has an ammeter, I'd say its slightly more useful than a Smartgauge. Not realising that the capacity of batteries falls with age/cycles is a fairly basic error. Had they read the other readings in addition to the SoC, more frequently, they'd have seen a low voltage much sooner than the 10V observed, correlated it with (say) 85% SoC, and realised that something wasn't right.

 

Also don't forget that the Smartgauge doesn't give "actual" SoC - it gives its estimate of SoC - which admittedly if you don't set the battery capacity on the BMV702 correctly, will be closer to the actual SoC. There are scenarios where the Smartgauge representation of SoC is inaccurate.

You are crediting them with an understanding of, and interest in, batteries! A lot of folk just want a fuel gauge that doesn't require any thought, interpretation or analysis, but just tells them how much juice they have left ad when to recharge. For those people, the Smartgauge is THE gauge.

Doesn't your shunt based Mastervolt monitor automatically adjust for capacity or is that just CEF?

No it doesn't know the capacity. It just calculates the CEF.

[Loafer]

I simply do not understand how the Smartgauge can be accurate with SOC, given that there is only a direct battery connection and a load of algorithms. Can it handle random solar input?

 

A BMV, with a wise operator, can easily be tailored to match the decline in capacity with age* and remain accurate.

 

*Age of the batteries, not the operator!