Trojan T105 Charging Efficiency

[Maine Sail]

Originally Posted by sailorboy1

Thanks, but that was just a discussion on the topic and that wasn't the question.

So Maine Sail, what do YOU have (had) your CEF set to?

Other folks CEF's would only matter if they had the same batteries at the same age and Ah capacity under the same identical use. They would also need the same charge rate as you too.

When you have both low rate solar and high rate charge sources such as an alternator a single fixed number charge efficiency factor is far less than ideal. A low charge rate can be quite efficient, but high charge rates are less efficient. How do you apply one number for both? You can't so you do the best you can.

What everyone else has is really irrelevant to your system and will only have you chasing ghosts. You have to do your best determine CEF or let the batteries cycle to 100% regularly to "auto-set the efficiency".

CEF on these monitors is not accurate with PSOC use so best get back to 100% SOC as often as possible or the counting errors will simply add up.

As I mention in the article do the best you can because CEF will introduce counting errors during PSOC use..

Trojan generally recommends that the T-105 has a charge efficiency of about 85% at .1C to .13C or 10-13% of Ah capacity in charge current. Best to start there.

If your charge rate is higher or lower than .1C to .13C then this number will be slightly different. If your batteries are partially sulfated, this number again, will be slightly different.

[sailorboy1]

In the end you have to pick ..................... a number

All the reasons why the number is probably wrong changes nothing. Which is why all I asked is what number people picked. Why does it have to be so hard????

[Maine Sail]

Originally Posted by sailorboy1

In the end you have to pick ..................... a number

All the reasons why the number is probably wrong changes nothing. Which is why all I asked is what number people picked. Why does it have to be so hard????

We don't know what brand monitor you have? Why is it so hard to give more details...? On some Ah counters you don't have to set it manually and on some others you do. Without knowing what monitor you are using it is impossible to say.

If you have an Ah counter that can auto-calculate CEF, at 100% SOC, then use that. If not start at Trojan's recommendation and adjust until you're happy..

[sailorboy1]

just forget it

[conachair]

Originally Posted by sailorboy1

What are others using for T105 charging efficacy?

Much more interested in getting them back to 100% on more days than not, after that if the SOC shown on a battery monitor is out by a good few percent it doesn't matter.

[john61ct]

Sailorboy, I think you're right what you're asking has no simple straightforward answer, just keep testing until you find a number that best meets your needs for now.

Originally Posted by Maine Sail

If you have an Ah counter that can auto-calculate CEF, at 100% SOC, then use that.

And then there are cheap units that don't even try to take CEF into account, Nor Peukert.

I realize Bruce's testing on SoC meters is in progress, but in the meantime is there a coulomb-counting one you think is better than Victron's 70x-BMV?

[a64pilot]

Originally Posted by Maine Sail

If you have an Ah counter that can auto-calculate CEF, at 100% SOC, then use that. If not start at Trojan's recommendation and adjust until you're happy..

That is as clear and concise an answer as possible, direct to the point.
You remind me of someone years ago that asked me why their car wouldn’t start so I started asking a few questions. She got annoyed and stated she didn’t want to answer any questions, she just wanted to know why her car wouldn’t start.

[kmacdonald]

Originally Posted by sailorboy1

just forget it

I depends! If you ask one more time I think you will get your answer.

[sailorboy1]

One

I just asked for a number that YOU were using. I don't understand why people want to post with solution to a problem I didn't ask, but still don't put their number.

Acturally I do know the reason , there's no "expert" points in "fixing" a problem that doesn't exist and wasn't asked about.

[StuM]

Originally Posted by kmacdonald

I would have thought the opposite. It really takes a long time to get from 80% SOC to 100% SOC. The acceptance drops way off. Maybe Maine Sail will let us know for sure. He's the guru on that sort of stuff--------and just about anything else boat related. His web site: https://marinehowto.com/

Charge efficiency and acceptance rate are independent facts. Low acceptance rate doesn't imply low charge efficiency.

Charge efficiency = amp hours stored per amp hour input
Acceptance rate = max amps in at a specific charge voltage.

[kenbo]

For hose that like to read about this stuff.

[kmacdonald]

Originally Posted by StuM

Charge efficiency and acceptance rate are independent facts. Low acceptance rate doesn't imply low charge efficiency.

Charge efficiency = amp hours stored per amp hour input
Acceptance rate = max amps in at a specific charge voltage.

Actually you need to read the article linked by kenbo above.

[Maine Sail]

Originally Posted by kenbo

For hose that like to read about this stuff.

That is one of the Sandia papers I referenced in the article on getting the most accuracy out of your battery monitor. I like that study because it used standard Trojan flooded batteries similar to what we use on boats, not some esoteric tubular batteries used in stationary applications.

For Sailorboy1 I did give an answer, start at Trojans recommendation of 85% and adjust as necessary. The Sandia study confirms what Trojan suggests, "overall efficiency" is around 85% but "overall efficiency" does not tell the whole story when we PSOC cycle with a battery monitor that has a fixed single CEF number.

Sandia National Laboritories: "Notice also that the overall efficiency shows high values, with full charge represented by approximately 85% efficiency, a commonly used value for battery charge efficiency. More importantly, notice the dramatically lower efficiencies for the increments above about 80% state of charge, where most values are below 60% efficiency, and full charge is represented by less than 50% efficiency."

What this is saying is that if you start from 0% SOC and charge to 100% SOC the "overall efficiency" is about 85%. However if you start at 80% and cycle to full the efficiency can be as bad as 50%. For every Ah delivered at high states of charge only about half of that Ah is being stored in the cells..

As I mentioned above, and in the article, setting a single number charge efficiency won't remain accurate under PSOC use, "is what it is". You just do the best you can and aim for 100% SOC, to get a clean re-set, as often as you can..

As the Sandia paper clearly points out battery charge efficiency is not linear across the SOC curve but most Ah counters treat it as such. This is but one of a number of reasons they can get "out of sync" with the battery if not set up carefully.

[sailorboy1]

90% seems to be working well with the combination of half bulk charging via generator/battery charger and half slower solar bulk/absorption charging. My gut feeling is that with full solar slower charging only you could probably use a higher efficiency.

[Pizzazz]

Just read the article above. So, charging efficiency is 90% at half full and, say 60% at nearly full. If you are keeping your batteries nearly full on the average, you are throwing out 1/3 of your installed solar capacity for nothing (well heating the battery compartment is one use). One more reason to operate your batteries at 50% average state of charge and try to hit 100% as often as practical but don't worry too much.

FYI, I replaced my house battery bank yesterday. The old Energizer golf cart batteries lasted 5 years 8 months and for the last three years have been abused in every possible way, partial SOC, large current discharge, etc. They just refused to die.