Keeping battery bank topped up through winter

[Mike Tee]

I have a very simple electric system on our 'holiday' boat - 3 x 110 batteries supplying 12 volts for leisure use. No starter battery, we either use the leisure batteries or the starting handle. I also have a caravan type lead with a 16a plug on one end, inline galvanic isolator and extension type sockets protected by inbuilt RCD on the other end.

I also have a ctek mxs5 charger I have had for years. Would it work leaving the ctek charger permanently plugged in to keep the batteries topped up?

[MtB]

What does the ctek manual say?

 

 

[magnetman]

I use a CTEK charger on a shore power supply and it seems fine. Its a 15a version. They are good chargers I don't think it will cause any harm to the batteries. 

 

 

Just now, MtB said:

What does the ctek manual say?

 

 

RTFM?

[ditchcrawler]

4 minutes ago, MtB said:

What does the ctek manual say?

 

 

[Mike Tee]

Just now, MtB said:

What does the ctek manual say?

 

 

It thinks people only have one battery. It says it is fine for charging 'a 110ah battery'. I basically have a very large 110ah battery (3 wired together) and wondered what if any, problems might occur.

[MtB]

1 minute ago, Mike Tee said:

It thinks people only have one battery. It says it is fine for charging 'a 110ah battery'. I basically have a very large 110ah battery (3 wired together) and wondered what if any, problems might occur.

 

That makes a 330AH battery then! 

 

 

[ditchcrawler]

5 minutes ago, Mike Tee said:

It thinks people only have one battery. It says it is fine for charging 'a 110ah battery'. I basically have a very large 110ah battery (3 wired together) and wondered what if any, problems might occur.

It may cause a problem if you wanted to charge them, ie, pump 200Ah into them but mine maintains my batteries for a week when I am in drydock

[blackrose]

A 15 amp 3 stage charger will be fine left on float over winter. However that cheap brand probably won't automatically cycle a full charge if it senses no battery activity over time. For that reason perhaps once a month try to get to the boat to switch the charger off and back on so that it goes through a full charge cycle.

 

Also I'm not sure what type of batteries you've got but the charger is likely to put out 14.4v maximum which is fine for sealed batteries but not really enough for open flooded lead/acid batteries and if that's what you have they will get sulphated.

Edited October 3, 2023 by blackrose

[Mike Tee]

11 minutes ago, MtB said:

 

That makes a 330AH battery then! 

 

 

Thats what I couldn't work out - in my head if they were wired up to produce 12v then it was still a 110ah battery, but a big one! So it would just melt?

[magnetman]

CTEK isn't a cheap brand they are actually quite expensive. 

As shown in the link above £90 for a 5a charger is not real bargain basement.

 

My 15a version was a bit more than that and has several settings including maintenance mode. I think it even boats something like a 7 stage charging profile or something equally silly. 

 

Good quality gear. 

"It comes with automatic temperature compensation built in which ensures the best charging performance, even in the most extreme conditions. The MXS 5.0 also includes battery diagnosis to establish whether your battery can receive and retain a charge, patented automatic desulphation program, an AGM option which maximises the performance life of most Stop/Start batteries and a special Recond mode for reconditioning deeply discharged batteries. The MXS 5.0 uses CTEK’s patented float/pulse system, which is the most efficient maintenance mode when a battery is connected for long periods."

 

I believe this. 

 

 

Output14.4/14.7/15.8 V, 5.0 A

No problem with sulphation. I suppose the larger than recommended battery bank size could be an issue but if all it is dealing with is self discharge it seems a little improbable there would be any trouble. 

[PCSB]

23 minutes ago, Mike Tee said:

Thats what I couldn't work out - in my head if they were wired up to produce 12v then it was still a 110ah battery, but a big one! So it would just melt?

It is most unlike;y to melt

[Mike Tee]

Thanks for all the comments - think I'll give it a go, the batteries were well charged up after cruising, and I only want to keep them topped up. I believe that the charger is 'smart' enough to shut down if there is a problem.

[David Mack]

A reasonable amount of solar will keep batteries topped up through the winter if you are not actually using any power.

[blackrose]

6 hours ago, magnetman said:

CTEK isn't a cheap brand they are actually quite expensive. 

As shown in the link above £90 for a 5a charger is not real bargain basement.

 

My 15a version was a bit more than that and has several settings including maintenance mode. I think it even boats something like a 7 stage charging profile or something equally silly. 

 

Good quality gear. 

"It comes with automatic temperature compensation built in which ensures the best charging performance, even in the most extreme conditions. The MXS 5.0 also includes battery diagnosis to establish whether your battery can receive and retain a charge, patented automatic desulphation program, an AGM option which maximises the performance life of most Stop/Start batteries and a special Recond mode for reconditioning deeply discharged batteries. The MXS 5.0 uses CTEK’s patented float/pulse system, which is the most efficient maintenance mode when a battery is connected for long periods."

 

I believe this. 

 

 

Output14.4/14.7/15.8 V, 5.0 A

No problem with sulphation. I suppose the larger than recommended battery bank size could be an issue but if all it is dealing with is self discharge it seems a little improbable there would be any trouble. 

 

Ok, should be fine then.

[Sea Dog]

When my Mastervolt Combi (2500kva inverter and 100 amp charger) packed up, I used a Ctek Mxs5 as a stopgap as I tried in vain to get support from Mastervolt and eventually fitted a Victron Inverter and separate Victron charger. As the batteries start fully charged (eg by the engine) it had no issues keeping them topped up whilst coping with my usual 12v load - lights, toilet, fridge, fresh water pump. On its own it may not have managed those loads, but the batteries fully charged batteries can and the Ctek happily topped them back up.

 

 

[Mike Tee]

9 minutes ago, Sea Dog said:

When my Mastervolt Combi (2500kva inverter and 100 amp charger) packed up, I used a Ctek Mxs5 as a stopgap as I tried in vain to get support from Mastervolt and eventually fitted a Victron Inverter and separate Victron charger. As the batteries start fully charged (eg by the engine) it had no issues keeping them topped up whilst coping with my usual 12v load - lights, toilet, fridge, fresh water pump. On its own it may not have managed those loads, but the batteries fully charged batteries can and the Ctek happily topped them back up.

 

 

Thanks, that’s what I was hoping to hear! Just out of interest, how big is your battery bank?

[magnetman]

29 minutes ago, Sea Dog said:

When my Mastervolt Combi (2500kva inverter and 100 amp charger) 

Cor that is one big inverter !

[Sea Dog]

11 hours ago, magnetman said:

Cor that is one big inverter !

Ha! Tis indeed! Ok, let's go for 2500va or 2.5kva. 

11 hours ago, Mike Tee said:

Thanks, that’s what I was hoping to hear! Just out of interest, how big is your battery bank?

Fair question - 440Ah. 

[Bod]

Before fitting solar, we charged from a shore line, with a 7 day timer, set to charge for 48 hrs a week, with a Sterling 40 amp charger.

 

Bod

[MtB]

22 hours ago, Mike Tee said:

Thanks for all the comments - think I'll give it a go, the batteries were well charged up after cruising, and I only want to keep them topped up. I believe that the charger is 'smart' enough to shut down if there is a problem.

 

I agree. Almost any properly 'smart' charger (i.e. one capable of dropping back to a float charge of perhaps 12.9 Volts - others may correct me!) should be able to keep a 330AH battery bank fully charged when out of use. It only has to replace the 'self-discharge' that lead acid batteries do to themselves. The self-discharge effect is tiny but cumulative over long period if not countered with a float-charging device.

 

 

[Mike Tee]

Just to update - batteries stayed topped up, after 3 months (end of december) I waited in trepidation for the first bill. Kept asking at every visit, finally got told the other day that they don’t send out bills for under £1 ! So although there is a fairly small solar setup, together with the mains charger it is doing well - I can cope with 70p every 3 months. Cheap peace of mind.

[LadyG]

On 04/10/2023 at 08:37, Mike Tee said:

Thanks, that’s what I was hoping to hear! Just out of interest, how big is your battery bank?

I probably have  500 nominal battery bank, in three banks, and a small CTEk charger suitable for a heavy duty starter battery, this charger seemed to charge up all my batteries over a long period (24hours), so I considered it was trickle charging, and the results were satisfactory, though using crocodile clips is not a permanent solution.