How to keep your batteries healthy and long lived

[john61ct]

Originally Posted by sailorboy1

Personally I feel you people running around being all proud of getting 8+ years out your batteries are living in a false economy world! You are spending more on making them last that long than it is to replace them. Plus all the worry and stress of taking care of the damn things. I bet if you kept better records you would find that the cost of the batteries are minor compared to things that you think about as “ cheap”

In other words, you are not interested in the topic.

Of course you're free to do what you like with your batts.

Problem is most people murder their bank out of ignorance, and the whole point of the thread is to increase knowledge for those who care to learn

[john61ct]

Originally Posted by sailinglegend

On the other hand, there is not much benefit to discharging at much less than the 20hr rate.

Low rates are never an issue, Peukert aside.

[john61ct]

Originally Posted by Pizzazz

Discharging to lower than 50% of capacity shortens the battery life. In a thread a few months ago I think we agreed that discharging FLAs to 20% of capacity halves the life.

The curve completely depends on the model, should be a spec easily found for any batt worth buying.

Originally Posted by Pizzazz

Not charging above 80-85% is not good for the battery but it is unclear if the damage is additive to the damage from point 2. There is no data, just anecdotal evidence that suggests it is not additive.

Not just "not good" but murderously abusive, and damage definitely additive. As SL so well explains, the resulting permanent sulfation damage is a completely separate issue from excessive DoD lost cycles.

Maine Sail has recently stated that getting to 100% Full "most cycles" or "at least a couple times per week" is sufficient to reduce the damage, but obviously every cycle would be ideal.

LFP makes this issue go away completely, but the only Lead (thus much cheaper) exception is Firefly Oasis.

I do believe that more than monthly equalization may be somewhat helpful, but an ounce of prevention. . .

Originally Posted by Pizzazz

Charging above 85% is very slow and one loses this capacity very quickly. That is, you can spend the whole day in the sun putting the additional 15% in, then just lose it with a little bit of fridge or microwave/TV time. Still, if one has the patience to hit 100% charged once every couple of days, it is good for the battery.

Aha, yes! Just that that "very slow" can be 3-4 hours, and that last 15%, getting to 100% (not 98-99%, again using endAmps) is not just "good for" the bank, but critical to longevity. The actual energy AH added is beside the point.

[kmacdonald]

Originally Posted by sailorboy1

Personally I feel you people running around being all proud of getting 8+ years out your batteries are living in a false economy world! You are spending more on making them last that long than it is to replace them. Plus all the worry and stress of taking care of the damn things. I bet if you kept better records you would find that the cost of the batteries are minor compared to things that you think about as “ cheap”

I agree. A huge battery bank requires running the main engine with large alternators or a generator AND a large solar system to get the battery up to 100%. Charging from 75% to 100% SOC takes a long time since the charging takes place under constant voltage. The acceptance rate drops off as the SOC increases. With a huge battery capacity, that's where most of the charging will take place. Besides lighter weight and less cost of a properly sized battery bank, thousands will be saved in charging equipment. I use a 20AH lifepo4 on my boat charged with a 30 Watt solar panel. I used to have a 60 Watt panel but found I didn't need near that big. I only run anchor light, cabin lights, VHF radio, Depth sounder, cell phones, and tablet PC. Now if I had a refrigerator and autopilot I would need more battery and charging capacity-----like 100AH and 150 Watt solar.
I also think the cheap Sams Club 6V GC batteries are the best bang for the buck. For about $200 you can have a 200+ AH house bank that will work great for most cruising boats. Now if you have to bring the toaster, all bets are off.

[Pizzazz]

I am trying to respond to multiple posters, forgive me for not quoting:

1. There are many factors that come into sizing the battery bank. My point was that at discharge rates higher than C/20, the Peukert’s law becomes significant (i.e. capacity is reduced by 9% going from C/20 to C/10, while going from C/20 to C/40 increases capacity by 4-5%). C/20 is just a happy mid-point and many battery capacities are quoted at that rate. If some people want to double the weight in order to get 4-5% increase in capacity (normalized per battery), it is their choice.

It is true that at C/100, you get 255 Ahr capacity but this means 2.5A current draw. In order to meet a typical 10A load (electronics, fridge, autopilot), you need 1000 Ahr. Not helpful to the average boater.

2 & 3. I am trying to stay away from statement such as "dramatically shortens" because it means different things to different people. The explanation that deep discharging and never reaching 100% SOC cause different types of damage actually supports my point - it is not additive in terms of shortening the battery life (I worded this wrongly before). One causes sulfation, the other I have no idea but I have seen charts where the battery life is half for FLA and 1/3 for AGM (1,200 cycles vs. 600 cycles vs. 400 cycles if discharged to 20% SOC).

4. It is a fact that golf cart batteries accept bulk charge at C/3 (mine is a Link 2000, temp compensated setup). It does go down gradually but it is still significant at 65-70%. The point is that you can charge much faster in bulk mode than in absorption mode. What is incorrect here? AGM batteries accept and deliver higher current relative to capacity, I never said the opposite. My problem with AGMs is that they have 1/3 the cycle life when deeply discharged.

Let's just think about how many things need to be right to get 8-10 years of battery life: temperature compensation, low charging current, low discharge current, 30% useable capacity (or 50%), slow charging, extra solar panels, frequent equalization, regular watering, replacing as a set, no mistakes, etc.... it is a freaking battery that costs $100!

Happy sailings.

SV Pizzazz

[john61ct]

Many many owners have $2-3 grand invested in their bank, so of course getting over a decade is the goal.

Obviously to be handled differently from a $180 pair of Deka 200AH GCs.

Which I consider the cheapest possible bank if you actually need deep cycling.

Those won't last much past 8 years even when coddled.

Again, do what you think is right for your setup.

Just don't murder the bank out of ignorance.

And realize it doesn't have to cost a lot to do it right, just a bit of learning and then paying attention.

[john61ct]

Originally Posted by kmacdonald

I use a 20AH lifepo4 on my boat

Link please

Yes LFP changes everything.

As does such tiny AH/day needs.

If you burn dino juice regularly for any other reason, LFP means no solar at all is required.

[john61ct]

Originally Posted by Pizzazz

The explanation that deep discharging and never reaching 100% SOC cause different types of damage actually supports my point - it is not additive in terms of shortening the battery life (I worded this wrongly before). One causes sulfation, the other I have no idea but I have seen charts where the battery life is half for FLA and 1/3 for AGM (1,200 cycles vs. 600 cycles vs. 400 cycles if discharged to 20% SOC).

Actually it **is** additive, say a given Rolls-Surette bank well-treated would last 12 years. The PSOC abuse may cut off four of those years, while taking DoD too low takes off three, so altogether mistreatment (whether intentional or not) caused a 5-year lifespan.

With a cheaper GC set, it might be 8 -(3+2) or even 8 -(3+3)

Originally Posted by Pizzazz

It is a fact that golf cart batteries accept bulk charge at C/3 (mine is a Link 2000, temp compensated setup). It does go down gradually but it is still significant at 65-70%.

No that is 100% false, which you can easily see with an ammeter and .5C charger on any FLA batt.

Maybe a Rolls Surrette can accept .2-.25C at 50% DoD, but ordinary GCs might get above .15C for say 30 minutes before the rate sharply declines.

In any case no 50% depleted lead bank gets to fully charged (defined via endAmps) in under 4-5 hours even with a 200AH charge source.

What you say about AGMs is basically correct, just over-generalized.

[kmacdonald]

Originally Posted by john61ct

Link please

Yes LFP changes everything.

As does such tiny AH/day needs.

If you burn dino juice regularly for any other reason, LFP means no solar at all is required.

This is the battery I use: GBS 12V (4-Cell) 20Ah LiFeMnPO4

My outboard doesn't have an alternator so I can only charge it with solar.

[john61ct]

Excellent, good price too, remember shipping cost?

Does it have a protective BMS (LVD/OVD) built in?

Rather than hijacking the thread would you mind starting a new thread outling your setup?

I'm sure the discussion would be useful to many.

[kmacdonald]

The AGM batteries in computer UPS (uninterrupted power supplies) last about 5 or 6 years on float and no discharge cycles.

[kmacdonald]

Originally Posted by john61ct

Excellent, good price too, remember shipping cost?

Does it have a protective BMS (LVD/OVD) built in?

Rather than hijacking the thread would you mind starting a new thread outling your setup?

I'm sure the discussion would be useful to many.

I have no BMS. It's all done manually. I have a Victon BMV700 (Victron BMV 700 Battery Monitor. An Amp Hour Meter for one battery bank) to monitor the voltage and current. I use a manual switch to turn off the solar. The solar charge controller is a Genasun. (https://genasun.com/all-products/sol...ge-controller/) I don't like the algorithm it uses so I manually turn the solar on and off. It's worked great for three seasons.
I could not do a better job than Main Sail with a how to do lithium so here is a link to his write up: https://marinehowto.com/lifepo4-batteries-on-boats/
All his articles are great.

[john61ct]

Originally Posted by kmacdonald

The AGM batteries in computer UPS (uninterrupted power supplies) last about 5 or 6 years on float and no discharge cycles.

And?

Deep cycle usage requires very good quality, hence expensive AGMs, **if** that's really what you need.

No one is using those for standby, completely different market and usage pattern.

And not what's being discussed here right, maybe start a new thread?

[john61ct]

Originally Posted by kmacdonald

I could not do a better job than Main Sail with a how to do lithium so here is a link to his write up: https://marinehowto.com/lifepo4-batteries-on-boats/
All his articles are great.

Yes I refer people to his pages dozens of times per week, and donate at least monthly.

I see your source is out of stock on low-voltage storage packs now anyway.

Thanks for the info!

[sailorboy1]

Originally Posted by john61ct

In other words, you are not interested in the topic.

Of course you're free to do what you like with your batts.

Problem is most people murder their bank out of ignorance, and the whole point of the thread is to increase knowledge for those who care to learn

That's not true at all. I have a lot of knowledge and that knowledge tells me that those of you that use yours to see how long you can make batteries last by spending a lot of money to monitor and always getting them fully charged are living false economies! In meeting real cruisers very few are "murdering their banks and even the ones with little knowledge who barely even pay attention to theirs are getting good service life.

The thing about these threads is they are more about serving your batteries needs than making your batteries serve you. If you really need something thing this in your cruising life, you should just go back to work.