All About Boat Batteries

[Russ]

Yep I know the theory I but I've not experienced that and the guy I spoke to seem to have lots of experience with this. Different experiences can sometimes be the result of different environmental factors.... For example, it gets dam hot here .. and not that cold here too

Good point. Temps and conditions might make a difference.

A standard battery is designed to provide a very large amount of current for a short period of time.
A deep cycle battery is designed to provide a steady amount of current over a long period of time.
A deep cycle battery is also designed to be deeply discharged over and over again (something that would ruin a car battery very quickly). To accomplish this, a deep cycle battery uses thicker plates.

Again, I would also consider how you use your boat. If your 12v needs are small and only operate the boat with the motor running, a standard battery might work best as you only use the battery to start the motor and don't dishcharge it.
For me, I run a 12v cooler, chartploter, vhf and other devices that pull down the deep cycle battery. Doing this to a standard battery would shorten its life.
Nigel Calder's book has an excellent explanation of the chemistry of lead-acid batteries and how charging and discharging take place.

Trade them?? ... Please tell me more?
Someone gave me $20 once for an old battery. But I've never seen a trade up scheme where I live .... that's not just a scam

Trade is not an accurate term. I should have said replace them.
However, here in the states, you are charged for a "core" deposit of $20 if you don't return the old batteries. When you bring the old one back they refund you the $20.

[NiceAft]

A standard battery is designed to provide a very large amount of current for a short period of time.
A deep cycle battery is designed to provide a steady amount of current over a long period of time.
A deep cycle battery is also designed to be deeply discharged over and over again (something that would ruin a car battery very quickly). To accomplish this, a deep cycle battery uses thicker plates.

Russ,

Where do AGM's fit into this

Here is what I found: https://lifelinebatteries.com/2019/11/p ... batteries/

And this.

https://sciencing.com/marine-vs-deep-cy ... 06295.html

[Inquisitor]

AGM are at the upper end of price of lead-acid batteries. I've never had them, but they do deteriorate... brother-in-law is a pro bass fisherman and he expects to go through a set of AGM's per year using them in a 36V set for his trolling motor. He doesn't get even 300 cycles out of them.

"In theory... on paper... on Internet" doing full dis-charge of a set of LiFePO4 batteries will go 3000 cycles. If they are used less harshly they'll go more than 5000 cycles. It used to be that you had to pay for your second set of AGM's before you broke even. Now, its almost the same price for a lithium 12V battery as a top quality AGM. If you're willing to DIY, its FAR cheaper.

Other advantages...

• The built-in electronics of these batteries keep it from over-charging, over-discharging, over-current... over-heat... etc. So... they are basically trouble free and you don't have to baby them to get more than a 1000 cycles like you do with lead-acid.
• The rated capacity of full discharge is what the electronics allow. There is still a significant charge in the battery that the electronics won't let you dip into and destroy the battery. The battery I'm building will permit 270 Ah
• They are far lighter. My 270Ah battery should way around 55 lbs.
• They can take far higher charge and discharge rates. The cells I will be using can tolerate 270 amp charge rate and 540 amp discharge rate. The electronic BMS (battery management system) will permit only 120 Amp charge and discharge.
• My first tests will include a battery discharge at this 120 amps. My inverter is expected to be 1500 W.
• For comparison, I checked on-line for the type 31 Optima blue top battery. I give the lithium battery I'm putting together, then the Optima.
  1. Capacity: 270 Ah, 75 Ah - Need nearly 4 batteries to have same capacity.
  2. Usable capacity to get 3000 cycles: 220 Ah, 35 Ah - You need over 6x batteries (over time) to have same life!
  3. Cranking Amps: 540A, 1125A - This is short duration like starting a motor. Lithium, I would have to bypass the BMS which is why I will only be using it as a house battery, but could use it in an emergency to start the motor.
  4. Amps to get rated capacity: 27 Amps, 3.75 Amps - To handle the same load for the rated duration, you need over 7x AGMs.
  5. Weight: 55 lbs, 61 lbs
  6. Price: $600, $359 - Still more expensive, but not if you weigh in how much capacity, current rate and certainly not over time.
  It finally got to the price I'm willing to pay and play guinea pig.

[NiceAft]

Two days ago I posted:

Now I’m going to unplug the power cord for two days and see what the gauge shows.

Hopefully I will report back Thursday morning (East Coast U.S. time).

After two days of no power to the batteries, the % of charge was 42%. The voltage was 12.3 in the house battery, and 12.35 in the engine battery.


OK Neo, I await your report. Please remember, if your opinion is “stuffed”, use another term. Here, stuffed refers to a turkey

[Inquisitor]

If I remember correctly (from a particularly attractive foreign-exchange student from Australia) our equivalent to their "stuffed" is "preggers" (aka pregnant).

[NiceAft]

If I remember correctly (from a particularly attractive foreign-exchange student from Australia) our equivalent to their "stuffed" is "preggers" (aka pregnant).

Awaiting Neo's translation. Inquiring minds want to know.

[Neo]

I live in England for the first 30 of my life and language is more structured in the UK. But I'm now in Australia and just about "Anything Goes" when it comes to language
So in answer to your question "Both" is accepted by the average Aussie Bloke...
"It's stuffed" ... Not working
"It's been stuffed" ... e.g. a turkey!
"She stuffed" .... She is very tired or she's pregnant!
And Australians don't seem to care that they may not be understood either.

Now I'm curious how your Smartgauge is detecting/calculating the charge level ... But I can't find any technical information on exactly how it's making those measurements.

[NiceAft]

Hopefully this may satisfy you?

[Jimmyt]

Not much info in that, other than its within 5%, and gets better over time. Oh, and it's much better than all other battery monitors... And somehow it does all of that with only two wires.

They want to keep all of their proprietary logic to themselves apparently.

If that is your resting voltage after being on the charger up until 2 days ago, stuffed may be the word you're looking for. Voltage should probably be over 13 in your climate for good AGMs. Is your charger designed for AGMs? Also, did you get a chart with the AGMs that showed state of charge vs voltage?

The following is a generic SOC vs Voltage for AGM. Only good for gross info. But, if you've been on the charger up until two days ago, and had no load or charge for the last 2 days, 12.3 volts isn't good news.

[Jimmyt]

If I remember correctly (from a particularly attractive foreign-exchange student from Australia) our equivalent to their "stuffed" is "preggers" (aka pregnant).

Maybe the attractive exchange student could tell us whether it's the batteries or the charger that's stuffed.

[NiceAft]

When it comes to batteries, I have no embarrassment stating that I am not knowledgeable, but I also am not convinced that the batteries are in bad shape.

When I bring the Mac to my marine mechanic to winterize the motor, and change the oil. It might sit in the lot for days before a mechanic can get to it. When needed, the motor starts right up. I may not be able to pick it up for a few more days. I could be wrong, but I have not seen any convincing negative evidence.

Looking at the chart, we assume that the % of charge indicated on my gauge is correct, so the voltage should be in the yellow area. If we assume the the voltage indicated on the gauge is correct, the chart shows 70% in the green area. Either way, the chart does not corroborate what the gauge shows. There is an inexplicable inconstancy between the two.

[Jimmyt]

Actually, we don't know that the gauge is wrong. The percent of charge available may take into account that you don't want to get into the yellow zone. So, your meter may be telling you that you have 42% left before you hit the yellow zone. Did you have a setting on the gauge to tell it you have AGMs? The voltage range is different from lead acid (generally speaking). Also, have you put a good test meter on the battery to verify your gauge voltage?

As Neo was alluding to, without knowing what the gauge is thinking, it's hard to know how to interpret the readings.

Your batteries may be fine. My concern is, something isn't right. Fully charged and rested, an AGM battery should be showing around 13 volts. 12.3 volts is below lead acid fully charged and rested voltage. So, either your gauge voltage is incorrect, your charger is bad, or your battery is getting weak. Fortunately, this isn't difficult to chase down.

[Neo]

Hopefully this may satisfy you?

I wish it did. But when someone states "proprietary methods" .... It just makes me more curious.

[Russ]

]

That's an interesting device. I had to look it up

https://balmar.net/products/smartgauge-battery-monitor/

A bit pricey, but VEEERY interesting. Might have to put it on the list for santa.
Agree on the proprietary aspect. I'd love to know how it works because it seems to simply connect directly to the battery. No shunt.

[Jimmyt]

Actually, we don't know that the gauge is wrong. The percent of charge available may take into account that you don't want to get into the yellow zone. So, your meter may be telling you that you have 42% left before you hit the yellow zone. Did you have a setting on the gauge to tell it you have AGMs? The voltage range is different from lead acid (generally speaking). Also, have you put a good test meter on the battery to verify your gauge voltage?

As Neo was alluding to, without knowing what the gauge is thinking, it's hard to know how to interpret the readings.

Your batteries may be fine. My concern is, something isn't right. Fully charged and rested, an AGM battery should be showing around 13 volts. 12.3 volts is below lead acid fully charged and rested voltage. So, either your gauge voltage is incorrect, your charger is bad, or your battery is getting weak. Fortunately, this isn't difficult to chase down.

Since Russ put the link on to the gauge info, I gave the manual a quick skim.

The gauge has to be told the battery type during setup. If you change batteries (power loss), the gauge will resume operation using the same battery type as initially configured.

The gauge has to be directly wired (fused) to the battery banks at all times. It cannot be connected through your battery selector, or otherwise disconnected from the banks.

The manual is specific about wire gauge and warns about length of sensor wire runs without giving a specific limit.

While the state of charge would be incorrect if the wrong battery type was connected, there was no indication that the voltage reading should be off.

Ray - did you have the cabin lights on when you took the pic (or any other systems on)? Voltage will droop under load and rebound after resting. My lead acid batteries do, anyway.