What % charge for Torqeedo in long storage?

[fredrussell]

I don’t have a Torqeedo, but I’m curious as to what state of charge the manufacturer recommends for long periods of no usage.
I generally use my tender and outboard maybe twice a year, often less and I think I’m right in saying lithium batteries do not ‘like’ being left fully charged for long periods of time. Obviously leaving battery at, say, 50% charged is not ideal when you come to use it. So is there a way round this, or is the chemistry of Torqeedo batteries such that they can be lengthily left fully charged?

 

[Poey50]

I don’t have a Torqeedo, but I’m curious as to what state of charge the manufacturer recommends for long periods of no usage.
I generally use my tender and outboard maybe twice a year, often less and I think I’m right in saying lithium batteries do not ‘like’ being left fully charged for long periods of time. Obviously leaving battery at, say, 50% charged is not ideal when you come to use it. So is there a way round this, or is the chemistry of Torqeedo batteries such that they can be lengthily left fully charged?

I've not seen a quoted figure but no lithium ion battery benefits from hanging around at full charge. Assume 3% self-discharge per month at room temperature, lower if colder, higher if hotter. If you leave at 70% SOC you should be fine for many months and won't damage capacity. I bring ours home so then it is no problem to up the charge at the start of a trip if needs be.

 

[mattonthesea]

Mine says charge it fully every six months if left unused. But I do wonder!

 

[dunedin]

Surely if just using twice a year a conventional outboard would be much more cost effective - and if buy second hand more environmentally friendly?

 

[Pete7]

Surely if just using twice a year a conventional outboard would be much more cost effective - and if buy second hand more environmentally friendly?

Perhaps, but you won't see the electric outboard owner stripping down his carb for the 3rd time that season with gummed up jets. We only use about 5 litres of petrol a year and the little Honda is in good shape, but when it comes time to change, certainly be looking closely at electric outboards. At least they don't have to live on the pushpit but can be stored below out of harms way.

 

[cpedw]

I don't know if Torqeedo is similar but my new epropulsion spirit asks to be left at 60% for long storage. It also likes that so much that it will run itself down after a period left unused and uncharged. I forget the period but it is several weeks.
Th new battery (manufactured 5/21, purchased 11/21) was at about 60%.
There's also an anomalous feature that I don't yet understand. After a period (same one?) inactive, it switches the output off. It must be recharged briefly to revive it. How to do that without mains or a 12V charger? 12V chargers exist on the website but are unavailable for some unknown reason!
All information here is based on a quick read of the manual so may not be accurate. I haven't got it wet yet.

 

[Poey50]

Mine says charge it fully every six months if left unused. But I do wonder!

Hmmm ... I think that may be code for "we'd better not make it look too complicated by suggesting charging periodically to 60 or 70% for the least damaging storage, so better to keep it simple and risk a bit of degradation from charging and leaving it at 100%. Otherwise the fools may let them run completely flat and write their battery off" .... or something like that!

 

[Travelling Westerly]

Perhaps, but you won't see the electric outboard owner stripping down his carb for the 3rd time that season with gummed up jets. We only use about 5 litres of petrol a year and the little Honda is in good shape, but when it comes time to change, certainly be looking closely at electric outboards. At least they don't have to live on the pushpit but can be stored below out of harms way.

Exactly why I brought an Epropulsion. NEVER looked back. Really really recommend them.

 

[Travelling Westerly]

I don't know if Torqeedo is similar but my new epropulsion spirit asks to be left at 60% for long storage. It also likes that so much that it will run itself down after a period left unused and uncharged. I forget the period but it is several weeks.
Th new battery (manufactured 5/21, purchased 11/21) was at about 60%.
There's also an anomalous feature that I don't yet understand. After a period (same one?) inactive, it switches the output off. It must be recharged briefly to revive it. How to do that without mains or a 12V charger? 12V chargers exist on the website but are unavailable for some unknown reason!
All information here is based on a quick read of the manual so may not be accurate. I haven't got it wet yet.

It's some sort of hibernation feature to protect the battery during long term storage. We'll that's how Nestaway boats explianed it to me.

 

[mattonthesea]

Hmmm ... I think that may be code for "we'd better not make it look too complicated by suggesting charging periodically to 60 or 70% for the least damaging storage, so better to keep it simple and risk a bit of degradation from charging and leaving it at 100%. Otherwise the fools may let them run completely flat and write their battery off" .... or something like that!

Also, the charge level indicator is on the tiller, on boat, while the battery may not! Guesswork for less than full?

 

[Poey50]

Also, the charge level indicator is on the tiller, on boat, while the battery may not! Guesswork for less than full?

If you can remember the % charge when you last used it then just deduct 3% per month if the battery is stored in the house.

 

[jdjp]

There are two ways to damage a Li-ion battery. The most serious is to try to take current out of it when it's empty - and all batteries will have internal cut-off circuits to prevent that. Even so, if you leave a battery completely flat with the cut-out active the internal leakage will continue to do damage. This would be the reason for the 'hibernation' feature mentioned above, and the advice to top the battery up every 6 months or so. I reckon that 6 months is really conservative though - unless you're storing the battery somewhere very hot it should hold charge for much leonger than that.

The other much less serious degradation happens during the topping-off constant-voltage stage of the charging cycle, when the voltage across the cells are held a bit higher than their natural fully charged voltage. If you leave a battery plugged in to a charger taking no current it'll cycle through the CV stage every few days (?) as the natural leakage of the battery is replenished, and damage will very slowly accumulate, but if you just leave a battery disconnected, whatever the state of charge, the amount of degradation is tiny. There may be a small difference between 90% charge and 70% charge, but it's negligible... So I would read the requirement not to leave a battery fully charged just as an instruction not to leave it permanently plugged into the charger unless you're planning on using the battery in the next few days.

I think I'm right here... although when I was designing integrated chargers in consumer electronics a few years ago, the aim was always to maximize operating time and see just how much charge could be squeezed into a tiny battery without setting it on fire, so the idea of leaving a battery anything other than 100% charge was anathema to our customers.

 

[KompetentKrew]

Obviously leaving battery at, say, 50% charged is not ideal when you come to use it. So is there a way round this, or is the chemistry of Torqeedo batteries such that they can be lengthily left fully charged?

Why is storing it at 50% charge a problem though? You can take the battery home and charge it the day before you plan to use it.

 

[Poey50]

... if you just leave a battery disconnected, whatever the state of charge, the amount of degradation is tiny. There may be a small difference between 90% charge and 70% charge, but it's negligible... So I would read the requirement not to leave a battery fully charged just as an instruction not to leave it permanently plugged into the charger unless you're planning on using the battery in the next few days.

Table 2 in this paper shows quite a large difference in permanent capacity loss between storing lithium ion at 100% SOC rather than 40% SOC at around room temperature. Best to keep away from the top end of the charge curve for storage and keep them cool.

BU-808: How to Prolong Lithium-based Batteries

 

[fredrussell]

Why is storing it at 50% charge a problem though? You can take the battery home and charge it the day before you plan to use it.

I suppose because I seldom know in advance when I’m going to use the flubber. I mostly just anchor in this local creek or that, put the kettle on and get a book out. Every now and then I’ll be tempted to go for a pootle around the local area in flubber, or go ashore for a walk, but it is rare. 2nd hand Torqeedos are starting to come down a bit in price now - I’ve seen a couple for sale for sub-£500 in the past month or two, though obviously battery health has to be considered here. I’ve currently got the ubiquitous Honda 2.3, of which I am a great fan, but I’d rather not have petrol on board if at all possible and I feel that internal combustion engines behave better when they’re used regularly, which my little Honda is not.

 

[Poey50]

I suppose because I seldom know in advance when I’m going to use the flubber. I mostly just anchor in this local creek or that, put the kettle on and get a book out. Every now and then I’ll be tempted to go for a pootle around the local area in flubber, or go ashore for a walk, but it is rare. 2nd hand Torqeedos are starting to come down a bit in price now - I’ve seen a couple for sale for sub-£500 in the past month or two, though obviously battery health has to be considered here. I’ve currently got the ubiquitous Honda 2.3, of which I am a great fan, but I’d rather not have petrol on board if at all possible and I feel that internal combustion engines behave better when they’re used regularly, which my little Honda is not.

As far as I'm aware there is no reason to bring the battery to full charge. In your shoes, just using it for short trips, I'd just keep it around 50-60% state of charge. That will give you a good long battery life.

 

[KompetentKrew]

I suppose because I seldom know in advance when I’m going to use the flubber. I mostly just anchor in this local creek or that, put the kettle on and get a book out. Every now and then I’ll be tempted to go for a pootle around the local area in flubber, or go ashore for a walk, but it is rare.

All good points which I hadn't considered - I use my tender differently.

2nd hand Torqeedos are starting to come down a bit in price now - I’ve seen a couple for sale for sub-£500 in the past month or two, though obviously battery health has to be considered here.

On their site Nestaway say: "in our opinion the new models [603 & 1103] are well worth the extra money (if you are considering buying a 503 or 1003 from someone who still has one it should be cheap!)" I suppose £500 meets that description.

 

[jdjp]

Table 2 in this paper shows.....

Poey50 knows much more what he's talking about than me - what I said above might have been accepted wisdom over a decade ago, but it was probably based on wishful thinking from the battery manufacturers and has since had to be replaced by actual measurements.... I should have spent more time reading batteryuniversity.com (still one of the best independent sources of information on the subject!!)

 

[FirstAway]

Extract from Torqeedo manual:

9.2 Caring for the battery
You extend the lifespan of your battery if you do not expose it to hot environments for longer than necessary. A cool ambient temperature is especially important if you store the battery for longer periods of time.
Comply with the following rules if you are storing your battery for a longer period of time. Storage for around six months: Charging level when stored 50 %. Storage for a whole year: Charging level when stored 100 %. If the battery is to be stored for several years the charging level should be checked once a year in order to prevent the battery from deep discharging.

 

[Poey50]

Extract from Torqeedo manual:

9.2 Caring for the battery
You extend the lifespan of your battery if you do not expose it to hot environments for longer than necessary. A cool ambient temperature is especially important if you store the battery for longer periods of time.
Comply with the following rules if you are storing your battery for a longer period of time. Storage for around six months: Charging level when stored 50 %. Storage for a whole year: Charging level when stored 100 %. If the battery is to be stored for several years the charging level should be checked once a year in order to prevent the battery from deep discharging.

Logically, if storing for a year it would be better to follow the six month routine twice.