Charging battery in situ

[Seashoreman]

Usually leave batteries connected on boat in yard over winter, both fairly new, starter and leisure, dry and 'boxed'. I want to keep them topped up with a trickle charger and have power nearbye. Simple question: should I disconnect them before connecting charger? Should they be left disconnected to maintain charge? Hope not too stupid for the experts.

 

[PhillM]

Usually leave batteries connected on boat in yard over winter, both fairly new, starter and leisure, dry and 'boxed'. I want to keep them topped up with a trickle charger and have power nearbye. Simple question: should I disconnect them before connecting charger? Should they be left disconnected to maintain charge? Hope not too stupid for the experts.

I leave mine connected and have a smart charger permanently connected too. I run the charger about once a month for 24 hours and that is more than enough to keep two 110 batteries fully charged.

 

[VicS]

Usually leave batteries connected on boat in yard over winter, both fairly new, starter and leisure, dry and 'boxed'. I want to keep them topped up with a trickle charger and have power nearbye. Simple question: should I disconnect them before connecting charger? Should they be left disconnected to maintain charge? Hope not too stupid for the experts.

Ideally open the battery isolators, ( effectively disconnecting the batteries from the boat systems), and connect the charger directly to the batteries but unless you have a dual output charger you will only be able to charge one at a time.

Adequate , as PhilM suggests, to charge for a few hours now and then if they hold their charge OK. Alternate between the batteries.

 

[Seashoreman]

Thank you for replies. However PhilM says leave connected and VicS suggests disconnecting. Am I to assume it maybe makes no difference to charging and cannot cause any harm to leave connected?

 

[VicS]

Thank you for replies. However PhilM says leave connected and VicS suggests disconnecting. Am I to assume it maybe makes no difference to charging and cannot cause any harm to leave connected?

Not physically disconnecting, as in removing the wiring from the battery terminals, but switching off with the isolator switches. You don't normally go away and leave the boat with the battery switches on , do you? Perhaps you do. Most people would not.

You are right, however, that from the point f view of charging it makes no difference provided there are no loads on the system that you have overlooked and which might mop up the output from a small charger

 

[RichardS]

I'm sure that most auto manuals say that one terminal of the battery should be disconnected before charging the battery in-situ with a battery charger. However, I have never disconnected the battery and, after 50 years without any problems, I won't be doing that anytime soon! :encouragement:

Richard

 

[Seashoreman]

Not physically disconnecting, as in removing the wiring from the battery terminals, but switching off with the isolator switches. You don't normally go away and leave the boat with the battery switches on , do you? Perhaps you do. Most people would not.

You are right, however, that from the point f view of charging it makes no difference provided there are no loads on the system that you have overlooked and which might mop up the output from a small charger

Right, got it. Never really sure, so thanks for that. I never leave boat without turning off battery switches. Flat battery on the water is one of my haunting fears.

 

[PhillM]

Hmm maybe I'm doing it wrong. I. Set the 1,2 all switch to all, turn on the charger and go back 24 hours or so later and they are both charged.

I should say the switches in the switch box are all always off.

 

[prv]

Hmm maybe I'm doing it wrong. I. Set the 1,2 all switch to all, turn on the charger and go back 24 hours or so later and they are both charged.

Where is the output of the charger connected?

Pete

 

[PhillM]

Where is the output of the charger connected?

Pete

Direct to the engine battery which is (1) on the switch.

 

[prv]

Direct to the engine battery which is (1) on the switch.

Ah, that explains the need to switch to "all"

Pete

 

[TonyBuckley]

I hooked up an intelligent charger (one that Halfords used to sell and wasn't particularly cheap and nasty) and directly connected to the batteries and it was great.

But then I left the boat and did not have the charger switched on to the shore power. When I returned (unusually it was after a few weeks away), the batteries were very very low.

I measured the resistance of the charger unpowered and I can't recall the ohms but it was enough to draw a reasonable current so I suspect that was why my batts were very low.

So maybe something to consider if the charger isn't powered, yet connected. Prob not a problem with a decent charger.

 

[VicS]

I hooked up an intelligent charger (one that Halfords used to sell and wasn't particularly cheap and nasty) and directly connected to the batteries and it was great.

But then I left the boat and did not have the charger switched on to the shore power. When I returned (unusually it was after a few weeks away), the batteries were very very low.

I measured the resistance of the charger unpowered and I can't recall the ohms but it was enough to draw a reasonable current so I suspect that was why my batts were very low.

So maybe something to consider if the charger isn't powered, yet connected. Prob not a problem with a decent charger.

This is something to be aware of if using a domestic/ car/ portable charger. In fact a current measurement would be more informative than a resistance measurement.

Mine draws approx 80mA , far greater than one would expect from a resistance measurement of 140 k ohms

 

[TonyBuckley]

This is something to be aware of if using a domestic/ car/ portable charger. In fact a current measurement would be more informative than a resistance measurement.

Mine draws approx 80mA , far greater than one would expect from a resistance measurement of 140 k ohms

Thanks for confirming.

I must admit to being VERY surprised at this so glad to share; I had assumed (poorly) a zero current draw. I'm going to boat tomorrow to remove the batts and attempt a recondition and charge from home, but I am not hopeful. Two 85AH batts. Though I did have success with the starter batt which came out of a very dead campervan and seems to be going strong and starts the engine in a second after reconditioning/charging with this charger. Leisure batts may be a different fish kettle.

I have looked up the charger and it is a Halford Smartcharge something or other. I know it charges at 12A max. The instructions were appalling and Halfords no longer sell.

Live and learn.

 

[VicS]

Thanks for confirming.

I must admit to being VERY surprised at this so glad to share; I had assumed (poorly) a zero current draw. I'm going to boat tomorrow to remove the batts and attempt a recondition and charge from home, but I am not hopeful. Two 85AH batts. Though I did have success with the starter batt which came out of a very dead campervan and seems to be going strong and starts the engine in a second after reconditioning/charging with this charger. Leisure batts may be a different fish kettle.

I have looked up the charger and it is a Halford Smartcharge something or other. I know it charges at 12A max. The instructions were appalling and Halfords no longer sell.

Live and learn.

Mine is an 8A Ring Smartcharge .... old model not the current one. Bought on the spur of the moment from Halfords. I think they subsequently offered something that looked very similar with their own name on it .

Only bought for home use so no complaints .... it does more or less what's claimed for it and is big enough for my needs.

Also have a 3.8 amp Lidl compact charger. No drain when not powered up but does not automatically restart when powered up. Needs the "mode" to be selected before it starts .


You need to know all these facts when choosing a charger but sometimes you only discover them when its too late.

 

[PhillM]

Mine is a ctek. Left permanently connected. Must say I've never had a battery discharge on me.

In the summer I get about an hour a fortnight on the engine with the alternator charging. In the winter I charge monthly.

Never seem to have less than 70% charge. Even living aboard for a week, though we do like the oil lamps, meths stove and meths heater, so not a big power user.

 

[VicS]

Mine is a ctek. Left permanently connected. Must say I've never had a battery discharge on me.

In the summer I get about an hour a fortnight on the engine with the alternator charging. In the winter I charge monthly.

Never seem to have less than 70% charge. Even living aboard for a week, though we do like the oil lamps, meths stove and meths heater, so not a big power user.

Ctek are I believe suitable for permanent connection.

My only concern ( possibly unfounded) is that some models may need the charging mode to be reselected after a power outage

 

[Danny]

Ctek are I believe suitable for permanent connection.

My only concern ( possibly unfounded) is that some models may need the charging mode to be reselected after a power outage

I have a ctek M45 which is permanently attached to my bowthruster/windlass battery. if the mains goes off it remembers its charging mode, so long as it remains connected to the battery the whole time.

 

[VicS]

I have a ctek M45 which is permanently attached to my bowthruster/windlass battery. if the mains goes off it remembers its charging mode, so long as it remains connected to the battery the whole time.

Thanks for clarifying.

 

[ghostlymoron]

I think it's the cheap chargers from Aldi that need to be re set after a power off situation. Pity because they are otherwise very good although only 3.8 amps.