Thermoelectic Plates

[ip485]

There was a discussion about batteries getting too hot under charge in warmer climates.

Would thermoelectric plates be of any benefit between the batteries?

 

[lw395]

I doubt it.

I don't think there is much data to suggest yacht batteries in e.g. the W Indies have a shorter life anyway.

 

[GHA]

There was a discussion about batteries getting too hot under charge in warmer climates.

Would thermoelectric plates be of any benefit between the batteries?

Certainly no doubt that increased temperature has a serious effect on battery lifespan, 8/10 deg c halving the life span seems to be a common ballpark.

As a guideline, every 8°C (15°F) rise in temperature cuts the battery life in half

https://batteryuniversity.com/learn/archive/can_the_lead_acid_battery_compete_in_modern_times

I know nothing of thermoelectric plates but it does look worth a look, if a cruising boat isn't trashing it's batteries by not getting fully charged most days then there will likely be spare solar power at least later in the day. Peltier plates seem pretty cheap on ebay, control wouldn't be *that* difficult with a raspberry pi running openplotter /signqlk.

 

[pcatterall]

So does this significantly change the debate on cost benefits of fancy versus cheaply batteries?
Are lithium batteries affected to the same degree?

 

[Lon nan Gruagach]

There was a discussion about batteries getting too hot under charge in warmer climates.

Would thermoelectric plates be of any benefit between the batteries?

There are more efficient ways of cooling things. Thermoelectric plates, or Peltier coolers benefits are noise, space and temperature range related. If you have none of those requirements then they arent that good. Also they dont move the heat away, you would still need to remove the heat from the "hot" side of the plate.

 

[pvb]

There was a discussion about batteries getting too hot under charge in warmer climates.

Would thermoelectric plates be of any benefit between the batteries?

No benefit at all; Peltier plates move heat from one side to the other, so you'd cool one battery and heat up its neighbour!

 

[geem]

I doubt it.

I don't think there is much data to suggest yacht batteries in e.g. the W Indies have a shorter life anyway.

They certainly do have a shorter life. Lots of evidence from manufacturers data on heat impact on life span. Just look at Victron, Rolls, Trojan websites for data. Its all there in black and white.

 

[geem]

So does this significantly change the debate on cost benefits of fancy versus cheaply batteries?
Are lithium batteries affected to the same degree?

I think if you are cruising in temperatures that are routinely in the high 20s/30s year round then there is an argument to reduce battery bank size (assuming you are using true deep cycle batteries such as those fitted to Golf carts) so that you cycle them daily to 50% DOD. The savings in cost could be considerable and the heat would probably kill them before the number of cycles. I read an interesting article that suggested you should do this anyway as it was the cheapest way of owning batteries.

 

[lw395]

They certainly do have a shorter life. Lots of evidence from manufacturers data on heat impact on life span. Just look at Victron, Rolls, Trojan websites for data. Its all there in black and white.

The actual data I'm seeing is mixed.
Yes it reduces the time for a battery to simply die of old age, but if you are wearing out the battery be cycling it, it's not so clear that the lifespan in number of cycles will be reduced significantly.
The increased aging rate might offset by the increased capacity at a warmer temperature.
If you are taking say 30Ah out of a nominally 100Ah daily, you might be close to temperature neutral.
If it's backup and sat on float 51 weeks of the year, then cooler is going to be better.
If you're taking nominally 50% out, that only 47% at 35 degC, which buys you another 200 cycles.

I'd be very cautious of half baked schemes to cool a lead acid battery, as the worst possible thing is probably to have a temperature gradient across the battery, where half a cell is cooler than the other half and has a different voltage characteristic. Likewise all batteries in a parellel bank need to be at the same temp for optimum life.

Fundamental rules are:
Ah are expensive
The warranty is only as long as the warranty.

 

[lw395]

I think if you are cruising in temperatures that are routinely in the high 20s/30s year round then there is an argument to reduce battery bank size (assuming you are using true deep cycle batteries such as those fitted to Golf carts) so that you cycle them daily to 50% DOD. The savings in cost could be considerable and the heat would probably kill them before the number of cycles. I read an interesting article that suggested you should do this anyway as it was the cheapest way of owning batteries.

Some truth in that.
The other thin to consider is the value of having a reserve, in case you need to run for more than one day between recharging.
When you look at real life and not every day is the same cycle, it becomes a mess of unknowns.

 

[ip485]

No benefit at all; Peltier plates move heat from one side to the other, so you'd cool one battery and heat up its neighbour!

Surely if the plate was under each battery it would move the heat to the hull (assuming most batteries sit on the hull) which would be cooled in turn by the external water?

 

[pvb]

Surely if the plate was under each battery it would move the heat to the hull (assuming most batteries sit on the hull) which would be cooled in turn by the external water?

Your question was "Would thermoelectric plates be of any benefit between the batteries?"

 

[William_H]

The best answer is to provide good ventilation for the batteries. If the air is drawn from area under the floor then this should be cool ie at sea temperature so good. Discharge the air outside to get rid of hydrogen produced when charging.
A large bank of batteries should give less current per battery so less heating per battery. (assuming a limited current source like solar but not necessarily so for a large engine driven alternator. ) ol'will

 

[GHA]

If the air is drawn from area under the floor then this should be cool ie at sea temperature so good.

That's the whole discussion - in the tropics it's not cool at all.

 

[duncan99210]

Surface water temperature in the Med in summer is typically 30 degrees C. Air temperature usually runs from 29 at night to 35-39 mid afternoon. So there’s no where to dump heat to, nor is there much value in using fans to move air round, there’s little or no cooling benefit. We spend enough energy moving heat to keep the beer cools: it’d be ludicrous to spend similar or greater amounts of energy to try and squeeze a slightly longer life out of the batteries!
I use reasonably cheap sealed batteries at about €110 for 100 amp hours: they last about 4 years before failing. The usual failure symptom is they become hot: very hot. For this reason, I’m going to start monitoring the battery bay temperatures so I can hopefully spot the early symptoms of failure.

 

[GHA]

Surface water temperature in the Med in summer is typically 30 degrees C. Air temperature usually runs from 29 at night to 35-39 mid afternoon. So there’s no where to dump heat to, nor is there much value in using fans to move air round, there’s little or no cooling benefit. We spend enough energy moving heat to keep the beer cools: it’d be ludicrous to spend similar or greater amounts of energy to try and squeeze a slightly longer life out of the batteries!
I use reasonably cheap sealed batteries at about €110 for 100 amp hours: they last about 4 years before failing. The usual failure symptom is they become hot: very hot. For this reason, I’m going to start monitoring the battery bay temperatures so I can hopefully spot the early symptoms of failure.

Though they do heat up both charging and and discharging so fan with air from the bilge might help. Without logging and plotting the data it's probably impossible to guess. Also a decent solar setup will have spare power later on as the batteries acceptance rate tails right off so certainly worth having a look at, but from a bit of time on google the peltier plates around struggle to cool a hard working cpu so might well be a red herring.
If you can spare a couple hundred mA a raspberry pi can store and graph temperatures (and much more), waterproof ds18b20 thermometers cost a cheap beer each, fit as many as you want