Can you really discharge deep cycle batteries to c. 10%

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Looking at replacing my existing batteries and seem to have a choice, I can easily fit in 2 x 150 ah Trojan Deep Cycle batteries that claim discharge down to 10% thereby giving a useable 270ah. However they make no claims for starting and don't quote CCA.

Or can fit in 2x Varta 230AH which ae physically bigger but claim to be suitable for both deep cycle and starting. Positives are that they claim to be spill proof to 90 degrees but I'm thinking they are not true deep cycle so I'm probably limited to 50% discharge limit so a useable 230 ah.

Anyone with any experience??
 
Check tech. specs. as expected life varies greatly with depth of discharge. See example DOD graph in this thread.

http://www.ybw.com/forums/showthrea...dy-used-them&p=4352882&highlight=#post4352882

Probably a good idea to get DOD graph from Trojan. They emailed one to me and that indicated that T105s were a much better option than 12V models I was offered.

Note:
1) Big difference between various models sold (factor of 2 in graph shown)
2) Best case with 6V T105, 50% discharge might give 1200 cycles and 90% only achieves 700 cycles
3) Examples will be under perfect condition (immediate 100% charge after discharge, optimised charging)

So DOD will affect expected life, especially if you regularly use deep discharge and you won't achieve manufacturers performance anyway.
 
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macd said:
I don't know which particular Trojans you're referring to, but if you check out their Q&A section, they state that at least some of their traction batteries are OK for starting use.
Click to expand...

Looking at Trojan t1275. The Q&A does say suitable (would be in emergency if engine starter battery died.)

That just leaves the question of how deep can you discharge. I get that you can discharge any battery to 0% - I guess the question is really how much damage do you do to the batteries by discharging beyond 50%.
 
I thought you might be looking at T1275. I didn't see this model when I was buying new batts. a few years ago. Do contact Trojan tech. support and ask for DOD graph. They answered my query very quickly and the graph made me feel comfortable with my choice vs. expected usage.

Might not be the full story but at least Trojan were happy to publish the data.
 
Battery life is very much determined by depth of discharge. What deep cycling (traction) batteries bring to the party is ability to be discharged and recharged over and over again. The deeper the discharge the lower the number of lifetime cycles. A typical 12 volt 110ah deep cycling battery may provide over 500 cycles at 50% depth of discharge, dropping to maybe half that for 100% DoD. A typical car or "leisure" battery would be ruined long before that. Trying to use traction batteries for engine starting is inefficient - larger traction batteries may well start an engine but that is not what they are good at so why not just use a small cranking battery and team it up with the Trojans or proper Varta AGM deep cycling batteries?
Robin
Pleiades of Birdham
MXWQ5
 
This will be for a domestic bank so looking for deep cycle. We have a dedicated engine start battery - my concern re the T1275 was that if something happens to the dedicated battery I would need to start from the domestic bank.

The Varta mention they are suitable. The T1275 didn't have a tick in that box and had no CCA figure quoted hence the question.
 
Interesting. Does this mean that all the Northern Dairies milk floats in Hull that ran out of power and were towed back to the depot were knackering their batteries?
I'd have thought the fleet manager would have had a better handle on his long-term costings than to allow that.

Mind you, we are talking about nearly 40years ago.
 
That was then, Lakesailor. Now, think golf buggies.
It's inescapable that ALL lead-acid batteries are in the process of being knackered. The issue is, how quickly? The shorter life of emptied milk floats was no doubt factored into their costs. (Be interesting to see their data, though, if any was kept and if it survives.)

As an aside, the learning curve of milk-float drivers may not have contributed to battery (or milk) longevity. As a kid I lived near a wide, quiet T-junction which the local float used for U-turns -- sometimes briskly. It was a fairly regular event to be woken by him losing his entire load. Until they sacked him.
 
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jac said:
Looking at Trojan t1275. The Q&A does say suitable (would be in emergency if engine starter battery died.)

That just leaves the question of how deep can you discharge. I get that you can discharge any battery to 0% - I guess the question is really how much damage do you do to the batteries by discharging beyond 50%.
Click to expand...

It's related to sulphation, deep discharge normally results in a low recharge level due to insufficient charge time, which in turn is the main reason for sulphation.

Back in 1982 we fitted a LED display on the VSR system, this showed above 50%, below 50%, below 25%, below 10%, at which point the power lock-out would drop out the fridge to stop it flattening the battery. The operating notes told people to charge the batteries when the yellow ( below 50% ) light came as soon as convenient, red immediately. This was based by limiting drain, recharging was more likely to be up to a satisfactory level, while draining to below 25% constantly resulted limited recharge, sulphation and surface charge. A second reason for the level was the battery on load voltage, below 50% it started to fall at a slightly greater rate, below 25% it increased, and 10% free fall, so limiting discharge maintained a better supply voltage.

Probably just as relevant to-day.

If I have a minute I'll see if I can find any design notes.

Brian
 
nigelmercier said:
You can discharge a battery to 0% and it will probably be OK, same with 10%. If you want to maintain a long life, 50% is a sensible ball-park.
Click to expand...

I believe that Trojan, in the US and for their 6v batteries, recommend that the batteries be totally discharged about every 18 months and, immediately be fully recharged (including an absorption phase).

Some figures, I saw in setsail.com, showed a significant increase in overall capacities before and after carrying out the exercise.

I have never had the blind faith to try...
 
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macd said:
That was then, Lakesailor. Now, think golf buggies.
It's inescapable that ALL lead-acid batteries are in the process of being knackered. The issue is, how quickly? The shorter life of emptied milk floats was no doubt factored into their costs. (Be interesting to see their data, though, if any was kept and if it survives.)

As an aside, the learning curve of milk-float drivers may not have contributed to battery (or milk) longevity. As a kid I lived near a wide, quiet T-junction which the local float used for U-turns -- sometimes briskly. It was a fairly regular event to be woken by him losing his entire load. Until they sacked him.
Click to expand...

At the risk of thread-drift - Son 2 had my 405 estate totally written off by a milk-float - the milk-float survived with minor scratches.
 
>However they make no claims for starting and don't quote CCA.

Some have used Trojans for starting but they are deep cycle golf cart batteries thus not designed for starting, high Amp output, hence no CCA information. If you want a service bank of batteries buy Trojans but if you want an engine starting battery buy a CCA battery. We never let CCA batteries or our Trojans go down to 10% you risk affecting the charge they will take and shorten their life, as mentioned. Bear in mind that the deep cycle Trojans are 6v with two wired in series for 12v, however the ah doesn't double it stays at 150 Amp hours, or whatever one battery is, ours were 120 ah.
 
charles_reed said:
I believe that Trojan, in the US and for their 6v batteries, recommend that the batteries be totally discharged about every 18 months and, immediately be fully recharged (including an absorption phase).

Some figures, I saw in setsail.com, showed a significant increase in overall capacities before and after carrying out the exercise.

I have never had the blind faith to try...
Click to expand...

Yes I read that as well and just like you I am not prepared to try it out.

Peter
 
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