Which replacement batteries?

[lw395]

Only because I happened to be looking at this recently:
https://www.victronenergy.com/upload/documents/Datasheet-GEL-and-AGM-Batteries-EN.pdf

Which again, only mentions shorter life under float service.
Table 2: Design service life of Victron batteries under float service
Absolutely no mention of getting less cycles in a cyclic service life where the cycle rate is enough to kill the battery long before the 'float service life'.

Clearly, some boats are going to struggle to exercise a battery through say 500 cycles before the temperature-affected service life if the average temperature is as high as 40degC.
It can become an argument for having less batteries and working them harder.
Or sailing somewhere with a temperate climate....

 

[dom]

Which again, only mentions shorter life under float service.
Table 2: Design service life of Victron batteries under float service
Absolutely no mention of getting less cycles in a cyclic service life where the cycle rate is enough to kill the battery long before the 'float service life'.

Clearly, some boats are going to struggle to exercise a battery through say 500 cycles before the temperature-affected service life if the average temperature is as high as 40degC.
It can become an argument for having less batteries and working them harder.
Or sailing somewhere with a temperate climate....

Oh I see where you're going; that's a good point. If high temp cycle-life is not massively dissimilar to lower temp cycle-life, then the question does indeed turn to the number of prospective cycles before float death.

Certainly if my Trojans were to only last 3 or 4 years as a consequence of high ambient temp, then I'd never have specced them them.

Might be worth dropping a line to one of the big OEMs?

 

[Graham376]

What is counted as a cycle? At the moment, my boat is left on the mooring with just the anchor light coming on at night, possibly 100ma draw. During the day, solar comes back on and should be float charging. When the boat's in use, batteries will drop to around 12.3 volts occasionally, more usually around 12.45v but never drop to 50% capacity. So, how does one calculate the number of cycles?

 

[dom]

What is counted as a cycle? At the moment, my boat is left on the mooring with just the anchor light coming on at night, possibly 100ma draw. During the day, solar comes back on and should be float charging. When the boat's in use, batteries will drop to around 12.3 volts occasionally, more usually around 12.45v but never drop to 50% capacity. So, how does one calculate the number of cycles?

Charts like these?
https://www.trojanbattery.com/markets/renewable-energy-re/

 

[GHA]

Oh I see where you're going; that's a good point. If high temp cycle-life is not massively dissimilar to lower temp cycle-life, then the question does indeed turn to the number of prospective cycles before float death.

From - http://www.windandsun.co.uk/media/172100/Trojan-T105-datasheet.pdf

My bold. No mention of float or charging, just a blanket ' increased rate of chemical reactions'

eXpected life vs. temperatureChemical reactions internal to the battery are driven by voltage and temperature. The higher the battery temperature, the faster chemical reactions willoccur. While higher temperatures can provide improved discharge performance the increased rate of chemical reactions will result in a corresponding loss ofbattery life. As a rule of thumb, for every 10°C increase in temperature the reaction rate doubles. Thus, a month of operation at 35°C is equivalent in batterylife to two months at 25°C. Heat is an enemy of all lead acid batteries, FLA, AGM and gel alike and even small increases in temperature will have a majorinfluence on battery life

 

[dom]

My bold. No mention of float or charging, just a blanket ' increased rate of chemical reactions'

As you say quite generic; a quick line to an OEM may well be worthwhile.

Although, you often seem to keep decent data on things and your caption reads "hopefully somewhere warm"! Any insights or thoughts into this?

 

[GHA]

Although, you often seem to keep decent data on things and your caption reads "hopefully somewhere warm"! Any insights or thoughts into this?

If I was wealthy enough to have 2 identical boats for a few decades , one topics & 1 high latitudes maybe
Bit warmer really does keep the voltage higher though, under load or not.

 

[macd]

What is counted as a cycle?...how does one calculate the number of cycles?

Essentially, undefined. The best you can probably do is guesstimate an average (or keep a log and calculate a running average, if you believe your battery monitor is accurate enough.)

It's more to do with the gross amount of chemical reactions one way and the other that a battery experiences. A shallow cycle is clearly less damaging than a deep one, although true deep cycle batteries are by design more tolerant than automotive batteries.

This Trojan document includes a depth of cycles graph for one version of the T105 (near the foot of page 2): http://www.windandsun.co.uk/media/172100/Trojan-T105-datasheet.pdf
You'll see that regular cycling to -40% gives a lifetime of 1500 cycles, to -80% only around 750 cycles. Far from showing that shallow cycling is "better", that equates to the same lifetime energy stored and released. (I've seen other Trojan graphs which suggest some gross lifetime benefit from shallow cycling, but it's not huge. In real-world use on a boat, rather than a controlled stationary installation, I daresay the figures for deep discharging might be somewhat optimistic.

The temp/percent capacity graph on the same data sheet also shows another significant factor: increased temperature may reduce lifetime but it also makes the battery "bigger".

Our installation, with 450Ah of T105s and a 340W of solar, rarely sees discharge below 60% of full, and usually less. That, for all that manufacturers' graphs might suggest otherwise, is how we like it. (Not least because consecutive sunless days are probable during the sailing season, even in the Med.)

 

[pcatterall]

All very interesting and, I guess, that it is best to start planning batteries with a good understanding of your probable useage.
Doing this has led me to revise our own requirements.
We are on board 120 days on float then 42 days where maximum use is 40% then 20 days where we would like ( but currently dont) go down to 20%
On this basis our cheapo batteries will expire through old age rather than excessive use ( rather like me!) even though we are in the med.
Only if we want more 'home comforts' switched on which would completly flatten the batteries, do we need to consider increasing capacity.

 

[macd]

then 20 days where we would like ( but currently dont) go down to 20%...On this basis our cheapo batteries will expire through old age rather than excessive use.

You're wise not to go down 20% (i.e. using 80% of capacity) on cheap automotive batteries. They're really not built for that sort of use. I doubt they'd tolerate many such cycles.

 

[Graham376]

Essentially, undefined. The best you can probably do is guesstimate an average (or keep a log and calculate a running average, if you believe your battery monitor is accurate enough.)..........Our installation, with 450Ah of T105s and a 340W of solar, rarely sees discharge below 60% of full, and usually less. That, for all that manufacturers' graphs might suggest otherwise, is how we like it. (Not least because consecutive sunless days are probable during the sailing season, even in the Med.)

Our installation is similar to yours, 4 x T105 and 320w solar. Liveaboard 6-7 months, on mooring for the rest.

 

[dgadee]

What about these new technology batteries? I bought new lead acid last year and wondered if that would be my last before lithium based ones came into my price range.

 

[ghostlymoron]

If you're on a mooring, you don't need to display an anchor light.

What is counted as a cycle? At the moment, my boat is left on the mooring with just the anchor light coming on at night, possibly 100ma draw. During the day, solar comes back on and should be float charging. When the boat's in use, batteries will drop to around 12.3 volts occasionally, more usually around 12.45v but never drop to 50% capacity. So, how does one calculate the number of cycles?

 

[GHA]

If you're on a mooring, you don't need to display an anchor light.

If there are fishing boats & water taxis flying by every hour of the day/night it's a *really* good idea.

 

[Graham376]

If you're on a mooring, you don't need to display an anchor light.

We and others have been hit in broad daylight! Lots of night time traffic through the moorings, often at high speed, sometimes drunk. Bad idea not to have low level anchor light.

 

[ghostlymoron]

I don't think an anchor light would help in broad daylight.

We and others have been hit in broad daylight! Lots of night time traffic through the moorings, often at high speed, sometimes drunk. Bad idea not to have low level anchor light.

 

[Graham376]

I don't think an anchor light would help in broad daylight.

That's why it isn't lit in daylight.