Winterizing bow thruster battery

[Rich834]

Hi, 

We don't stay on our narrowboat over the winter so I'm looking at how best to ensure my bow thruster battery survives the winter. 

We live overseas so taking the battery home and leaving on trickle charger isn't an option. 

 

The bow thruster battery normally gets charged via a battery-to-battery charger fed from the starter battery. So this only charges when the engine is running and the alternator is charging it.

 

Our boat does have solar panels connected to the leisure batteries via a Victron MPPT.

I'm thinking to temporarily hardwire the bow thruster battery inline with the leisure batteries so the solar keeps it topped up.

 

Thoughts?

 

Please don't respond suggesting to remove the bow thruster or similar. 

 

Thanks

[nicknorman]

1 minute ago, Rich834 said:

Hi, 

We don't stay on our narrowboat over the winter so I'm looking at how best to ensure my bow thruster battery survives the winter. 

We live overseas so taking the battery home and leaving on trickle charger isn't an option. 

 

The bow thruster battery normally gets charged via a battery-to-battery charger fed from the starter battery. So this only charges when the engine is running and the alternator is charging it.

 

Our boat does have solar panels connected to the leisure batteries via a Victron MPPT.

I'm thinking to temporarily hardwire the bow thruster battery inline with the leisure batteries so the solar keeps it topped up.

 

Thoughts?

 

Please don't respond suggesting to remove the bow thruster or similar. 

 

Thanks

A lead acid battery that is fully charged should survive a winter if left disconnected, so the short answer is “do nothing” except avoid using the bow thruster for several hours engine running before leaving the boat for the winter. Presumably there is a battery isolator for this battery, just open it to isolate the battery.

 

If you particularly want to, you could temporarily connect the BT battery to the leisure batteries, but I don’t think it is necessary.

[Tony Brooks]

I think that I would use a VSR to connect the domestic bank to the bow thruster battery so when solar is available both banks will be charged. That way, if there is a prolonged cloudy spell in winter, you won't discharge the domestic bank into the   thruster battery. It also protects against one battery developing cell shorts and damaging the rest.

 

I also think that the alternator should be charging the domestic bank, with the B to B charging the engine battery, hat way you get maximum charge to the domestics and the minimum current flowing from/through the B to B Misunderstood original post, please ignore this bit. The VSR could connect to the B to B output cable.

 

 

Edited July 10, 2024 by Tony Brooks

[blackrose]

33 minutes ago, Tony Brooks said:

I think that I would use a VSR to connect the domestic bank to the bow thruster battery so when solar is available both banks will be charged. 

 

That's what I've done. My BT batteries were already connected to the start battery via a VSR, so I added another VSR between the domestics and the start batteries so that all 3 banks are charged by the panels.

 

One word of caution though. If you're connecting battery banks you should first make sure that they're all the same chemistry type and will like the same charging regime otherwise you could be overcharging or undercharging one of the banks. My domestic and start batteries are all open lead acid which take 14.8v maximum absorption charge, while my BT batteries are sealed LAs. Most sealed LA batteries should only be charged up to 14.4v but Hancoook (or whatever they're called) told me these batteries could take up to 14.6v and the voltage drop to the bow ensures that's the most they see, so that worked out well. It's just work checking these things before you do it.

Edited July 10, 2024 by blackrose

[jonathanA]

I think I would just buy a cheap solar panels, one of those designed to keep car or caravan batteries maintained and stick that across the BT battery. Won't charge as such but will keep it topped up  they aren't expensive 10 or 15 quid tops. Downside is they're usually equipped with Croc clips and some one might nick it off the roof. Keep it simple!

[Jen-in-Wellies]

44 minutes ago, nicknorman said:

A lead acid battery that is fully charged should survive a winter if left disconnected, so the short answer is “do nothing”

This is pretty common practice in the classic car scene. They used to run the engines for an hour or so every few weeks to recharge the battery, but decided it did more damage to the engine than a proper run out. Nowadays, many will just shut everything down, so no drain on the battery and leave the car in the garage till winter is over and the salt has been washed from the roads. Seems to work OK for them.

Others will have a trickle charger on the battery, but it doesn't seem to be necessary.

[Tony Brooks]

As quoted rates of lead acid self discharge are between 8% and 20% per month, depending upon temperature, chemistry and so on, I would think it worthwhile trying to do something to combat that for batteries left standing for perhaps 6 months.

[blackrose]

3 hours ago, jonathanA said:

I think I would just buy a cheap solar panels, one of those designed to keep car or caravan batteries maintained and stick that across the BT battery. Won't charge as such but will keep it topped up  they aren't expensive 10 or 15 quid tops. Downside is they're usually equipped with Croc clips and some one might nick it off the roof. Keep it simple!

 

How is that solution any simpler than fitting a small VSR?

2 hours ago, Tony Brooks said:

As quoted rates of lead acid self discharge are between 8% and 20% per month, depending upon temperature, chemistry and so on, I would think it worthwhile trying to do something to combat that for batteries left standing for perhaps 6 months.

 

Agreed. Perhaps the classic car Herberts aren't aware of self- discharge of their batteries.

[jonathanA]

 

3 minutes ago, blackrose said:

 

How is that solution any simpler than fitting a small VSR?

Much...

 

No wiring, no need to make sure the VSR is correctly fitted, no testing and probably cheaper....

 

Although to be clear I think Tony's suggestion would be a 'proper job' and would make use of the existing solar.

 

[ditchcrawler]

6 hours ago, nicknorman said:

A lead acid battery that is fully charged should survive a winter if left disconnected, so the short answer is “do nothing” except avoid using the bow thruster for several hours engine running before leaving the boat for the winter. Presumably there is a battery isolator for this battery, just open it to isolate the battery.

 

If you particularly want to, you could temporarily connect the BT battery to the leisure batteries, but I don’t think it is necessary.

Nick, would the DC DC charger between the starter and the BT battery cause a drain, I have never had any thing to do with them.

5 hours ago, Tony Brooks said:

As quoted rates of lead acid self discharge are between 8% and 20% per month, depending upon temperature, chemistry and so on, I would think it worthwhile trying to do something to combat that for batteries left standing for perhaps 6 months.

Mine happily sat through Covid and started the engine on the button

[Tony Brooks]

5 minutes ago, ditchcrawler said:

Nick, would the DC DC charger between the starter and the BT battery cause a drain, I have never had any thing to do with them.

Mine happily sat through Covid and started the engine on the button

 

1. It seems at least some Sterling ones have an ignition feed, I presume to wake them up. They also stop when the donor battery is at 13.3 volts. What I don't know is if they have a small permanent drain so they can monitor the battery voltages.

 

2. Yes, starting normally only takes a few Ah, but we are talking bow thruster battery that could be in use for several minutes. Also, gradually flattening themselves must create sulphation, so the capacity is reduced. I suggest that as starting only takes a few Ah the starter battery will remain serviceable with far more sulphation than a bow thruster battery.

[Rich834]

Hi all,

Thanks for the suggestions. 

I've read a bit about VSR's and to be honest they look like a waste of time as they link the battery backs together bidirectionally whenever there is anything generating change. I e. Sun shining on a winter's day. (Unlike this summer).

The cheap portable solar panel is tempting but I have concerns around the quality of the control that should ensure it doesn't over charge. Don't want a fire while I'm away for months. 

 

So it seems my safest option is replacing my Victron MPPT with a dual output controller such as the Victron BlueSolar PVM and connect the starter battery on the 2nd output which should then charge the BT battery too using the existing battery-to-battery setup on those glorious sunny winter days.

 

Thanks again 

[ditchcrawler]

6 minutes ago, Rich834 said:

Victron BlueSolar PVM and connect the starter battery on the 2nd output which should then charge the BT battery too using the existing battery-to-battery setup on those glorious sunny winter days.

 

Thanks again 

If the DC Dc works without the ignition on, see Tony's reply to me

[Tony Brooks]

1 minute ago, Rich834 said:

Hi all,

Thanks for the suggestions. 

I've read a bit about VSR's and to be honest they look like a waste of time as they link the battery backs together bidirectionally whenever there is anything generating change. I e. Sun shining on a winter's day. (Unlike this summer).

The cheap portable solar panel is tempting but I have concerns around the quality of the control that should ensure it doesn't over charge. Don't want a fire while I'm away for months. 

 

So it seems my safest option is replacing my Victron MPPT with a dual output controller such as the Victron BlueSolar PVM and connect the starter battery on the 2nd output which should then charge the BT battery too using the existing battery-to-battery setup on those glorious sunny winter days.

 

Thanks again 

 

And exactly what is wrong with linking the two banks with a VSR when you were proposing hard-wiring them. VSR and a shorted cell won't discharge the other bank, length of wire, and it will. Don't you want all banks to be kept as fully charges as possible, or are you a live-aboard who wants maximum winter charge into the domestic bank. If that is the case, then I suppose you need to move the boat fairly regularly to get water etc. and that should keep the bow thruster battery charged enough, providing you don't use it much.  If you are on a mooring with water piped to the boat then you may also have mains electricity so battery charging is far better done with a suitable mains charger.

 

Remember that with lead acid batteries it is the BATTERIES that control the charge, so a fully charged bow thruster battery coupled to the domestic bank with a VSR will take virtually nothing from the available charge.

[blackrose]

3 hours ago, jonathanA said:

 

Much...

 

No wiring, no need to make sure the VSR is correctly fitted, no testing and probably cheaper....

 

Although to be clear I think Tony's suggestion would be a 'proper job' and would make use of the existing solar.

 

 

A VSR starts at about 12 quid, they're simple to connect and they don't need testing. 

 

My suggestion to fit a VSR was echoing Tony's. Yes it's a proper job, not a loose solar panel with trailing wires connected by croc clips which is liable to get nicked and isn't actually any simpler at all.

 

 

52 minutes ago, Rich834 said:

I've read a bit about VSR's and to be honest they look like a waste of time as they link the battery backs together bidirectionally whenever there is anything generating change. I e. Sun shining on a winter's day. (Unlike this summer).

 

 

No they don't link bi-directionally, they send charge to the auxillary bank when the voltage is high enough and when it isn't they break the link so that the banks remain independent. They're made to do exactly what you want to do, i.e. charge all banks from your single solar charging source without allowing them to drain each other when there is power being drawn. I don't understand why you think that's a waste of time when it's the obvious solution and one which most (sensible) people who know about these things use. But by all means, ignore the advice and do what you want, it's your boat.

Edited July 10, 2024 by blackrose

[Tony Brooks]

By the way, nothing to stop you putting a switch in the VSR's negative lead so you can turn it off when using the boat.

[nicknorman]

1 hour ago, ditchcrawler said:

Nick, would the DC DC charger between the starter and the BT battery cause a drain, I have never had any thing to do with them.

 

No I can’t imagine the output of the DCDC would drain any current, unless it is really badly designed. The input side might drain a bit though even when “Off”, but we would be talking a few mA at most,

[robtheplod]

8 hours ago, Rich834 said:

Our boat does have solar panels connected to the leisure batteries via a Victron MPPT.

I'm thinking to temporarily hardwire the bow thruster battery inline with the leisure batteries so the solar keeps it topped up.

 

This is exactly what I do. Its not the best solution as others have pointed out but it works (until it doesn't!) for me.. nice and simple we have a fused cable that connects between the banks - one end is bolted on and the other has a large insulated crocodile clip.

Edited July 10, 2024 by robtheplod

[ditchcrawler]

34 minutes ago, nicknorman said:

No I can’t imagine the output of the DCDC would drain any current, unless it is really badly designed. The input side might drain a bit though even when “Off”, but we would be talking a few mA at most,

Ta

[Rich834]

Ok, didn't mean to offend anyone but as stated in my original text I'm only looking for a solution when I'm not on the boat for several months of winter. I won't be using any electrical appliances for the duration.

 

A VSR adds no value compared to hardwiring when I'm not going to pull any load, just something else to break. 

 

Thanks Rob for the reassurance 😀

[ditchcrawler]

Just now, Rich834 said:

Ok, didn't mean to offend anyone but as stated in my original text I'm only looking for a solution when I'm not on the boat for several months of winter. I won't be using any electrical appliances for the duration.

 

A VSR adds no value compared to hardwiring when I'm not going to pull any load, just something else to break. 

 

Thanks Rob for the reassurance 😀

Unless one of your many batteries has one of its many cells fail while you are not there

[Rich834]

Some interesting reading on VSR's

 

https://www.12voltplanet.co.uk/news/why-vsrs-solar-systems-may-be-causing-damage-to-your-leisure-battery.html

[PeterF]

2 hours ago, Rich834 said:

 

So it seems my safest option is replacing my Victron MPPT with a dual output controller such as the Victron BlueSolar PVM and connect the starter battery on the 2nd output which should then charge the BT battery too using the existing battery-to-battery setup on those glorious sunny winter days.

You do know that the PWM solar chargers are a lot less efficient than MPPT solar chargers, so doing this will reduce your summertime solar charging.

The RV & camper van crowd have some trickle chargers to keep their engine batteries topped up over winter because the engine batteries run the alarms etc and modern vehicles are somewhat temperamental if you disconnect them. These systems tend to have diodes in to prevent reverse current flow. Some of the Victron Multiplus inverter/chargers have something like this built in, I have mine connected to engine battery and engine to bow thruster connected via VSR, keeps everything topped up over winter.The

 

https://www.sunshinesolar.co.uk/Item/BATTMA01

 

https://www.roadpro.co.uk/product/02e02-battery-maintainers/ablemail-amt12-2-trickle-charger-c8450/C8450

 

https://www.12voltplanet.co.uk/sterling-battery-battery-maintainer-12v-12v-3a.html

 

https://www.12voltplanet.co.uk/votronic-12v-standby-charger-trickle-charger.html

[Tony Brooks]

Seeing the volt drop caused by starter operation is probably going to be enough on a diesel to let the relay drop out I think the link is from a seller of B 2 Bs that obviously cost more than a VSR and are probably more complex to wire. Also, we have had solar on boats for years using VSRs without the problem described showing up. Then we often, but not always use dual purpose domestic batteries that are really starting batteries with handles, so will happily supply the starting current. Also, unlike many vehicle applications, we use several domestic batteries so any starter draw (if it really happens) will be shared between all the batteries in the bank, so probably less damaging than say a 3kW inverter at full power.

 

The worst thing is when the charge sources run to the engine battery rather than the domestics. That way the VSR has to carry the full charging current plus a further contribution for the all but fully charged engine battery, making relay burn out more likely - the same goes for ordinary split charge relays that we have had for 30 years or more. The way many split charge relays are wired will also allow the starter to draw current from the domestic bank, EXCEPT the domestic bank is usually well discharged with the engine battery fully charged, when the engine is started so little, if any, current will flow from the domestic bank.

 

I suggest this particular link is taken with a pinch of salt as far as properly wired systems on boats are concerned. It looks like marketing for more expensive equipment to me.

 

Edited July 10, 2024 by Tony Brooks