17MKE Battery & Charging question

[tptNbone]

You are correct to not drain your battery to zero, just to set the battery monitor.

You only need to know your "usable" amp hours and not what the battery is theoretically capable of delivering. Consequently, you only need to drain your battery to 12 volts [50% SOC] (after 1 hour rest) and then fully charge your battery for 24 hours without any other loads on the battery. This will be your "usable" amp hours of energy storage.

Your monitor may show 64 amp hours of battery capacity, or it might show slightly more capacity (most likely scenario) because the battery performance will decrease over time to the manufacturer's stated 64ah level. Lead Acid batteries loose capacity over time, so, the manufacturers stated capacity is lower than what the battery is capable when new. This way, the battery will still perform above specifications when the warranty eventually expires. If they specified the "real" new battery performance, then they would get a lot of warranty claims to replace perfectly good batteries.

One additional piece of advice: If you are monitoring your batteries too closely, you are not having fun camping. If you are constantly draining your batteries to 50% SOC you do not have enough batteries.

I suspect that you will quickly find that 64ah of usable battery is not enough energy storage for your camper, especially if you have a 12v or residential refrigerator, or if you need to run your furnace without Shore Power.

You probably need to start thinking about upgrading to Lithium batteries, they make camping so much easier, you won't know how you survived the Lead Acid era.

Here is a post that will help you understand the advantages of Solar and Lithium batteries:

Affordable-Solar-How-To-Design-and-Install-an-Affordable-Solar-System

Note: be sure to follow all the links in the above thread for more detailed information.

Thanks for the update, SolarPoweredRV. We recently bought a cover for our RV and put it on to make sure it fits. So right now I don't have good access to most things. But at my next opportunity I will try to do a setup on our TWO marine batteries. I know that Lithium's are the Cat's Meow, but for now with TWO Interstate batteries we plan to just get to know everything. We have a lot to learn.
Craig

[RV Sailor]

The 50% idea is a complete myth. Not even a shred of truth to it.

Ah fake news has arrived

When you exceed 50% deletion of charge you begin to decrease the number of available cycles left in lead acid batteries. I suggest you read about sulfation and how it affects battery life and overall charges. Posting inaccurate information is not a good educator for the novice.

[RV Sailor]

The battery is what limits the amount accepted after 85% charged ( bulk) and 93% charged ( absorb) . Increasing the charge to an unregulated one like a car charger defeats the 3 step process of charging and can overcharge or ruin the battery and lead to gassing

[JPS350]

I don't think your battery monitor was ever programmed right. Not sure exactly what the factory is putting in the new units, but if it's like the one I just bought for mine (see the Amazon link below), there are 2 ways you can set it up. Either you discharge the battery to 0% (ie, 10.5v) and set the counter to 0 so it can count up from there, or you fully charge the battery to 100% and reset the counter to 100% and let it count down from there. I found it easiest to just reset mine at full charge when I set mine up. Just select the % button and then hold it down for 3 seconds or so and it will reset to 100%. You also need to set the total battery capacity for the total of the 2 batteries you have installed and it should count properly from there.

https://www.amazon.com/dp/B088RG27LS...roduct_details

[TimtheToolMan]

Ah fake news has arrived

When you exceed 50% deletion of charge you begin to decrease the number of available cycles left in lead acid batteries. I suggest you read about sulfation and how it affects battery life and overall charges. Posting inaccurate information is not a good educator for the novice.

As you likely know, the lead acid battery type plays a major role in how low a battery can be discharged. On one end are starter (automotive batteries) and at the other end are the true deep cycle AGM. The OP does not have a true deep cycle battery so is much more limited in depth of charge without shortening battery life. The manufacture may have a data sheet which shows what the expected tested performance is, but quite possibly no readily available graphs for non deep cycle.

Attached is the data for an Intestate 6V deep cycle battery. Taking this battery down to 90 or 100% depth of charge when testing battery capacity and has a very minor affect on battery life. Testing true battery capacity gives me a good idea what the battery is capable of providing and I use this number to set parameters for the Victron BMV-712. I would not take anything but a true deep cycle battery this low.

As can be seen from the cycle life graph the number of available cycles @ 50% DOD is a little more that double the cycles when battery is discharged 100%, so the amount of total energy that the battery produces when discharged to 50% vs 100% is a little more but not a lot.

The three lines in graph are 50%, 80% and 100% DOD.

[TimtheToolMan]

Just above I wrote depth of charge and should have written depth of discharge (DOD).

Also I wrote but should have added text in paratheses "so the amount of total energy (Ahr per cycle times number of cycles) that the battery produces (over life of battery) when discharged to 50% vs 100% (DOD) is a little more but not a lot."

[jkwilson]

Ah fake news has arrived

When you exceed 50% deletion of charge you begin to decrease the number of available cycles left in lead acid batteries. I suggest you read about sulfation and how it affects battery life and overall charges. Posting inaccurate information is not a good educator for the novice.

As an engineer heavily involved in testing batteries during my working career, I can assure you my information is 100% correct. Battery cycle life decreases linearly with average depth of discharge below about 20%.

When you discharge a battery at all, you decrease the number of cycles it has left. This effect is particularly severe down to about 20% DOD.

The idea that discharging below 50% has some special effect on a battery is an absolute myth. If there were even a shred of truth to it, the cycle life vs. average depth of discharge graph would show a non-linearity at the 50% point.

This is misinformation promoted by non-technical people who don’t understand the designer rule of thumb that when sizing a battery, charger and charging schedule it is most economic to design it such that average depth of discharge is above 50%.

Promoting the 50% myth is the definition of misinformation.

[tptNbone]

Hi all,
OK, an update to my knowledge base on my experience with batteries. Again, I'm the fellow who was supplied with TWO Marine Lead Acid (not AGM) batteries, each having a 64 Ah rating. It appears that the dealer just set up my batteries as having 100 Ah max. I'm not convinced they really knew what to do. If I had a single 64 Ah battery, this would have been an OK start, because then you could see just how many Ah the battery could charge up to. But in my case, I had TWO 64 Ah lead acid batteries. Also, remember that I have the THREE state charger in my system, which I think is a good advantage. HOWEVER, with a three stage charger, that system needs to know what the current state is for the battery so it can properly control the charging process. What I witnessed while using and monitoring the system is that with shore power (my house 120 VAC), my batteries would really start slowing down the charge when the Ah got to around 75 or 80 Ah, so I could almost never get to a very high storage level. And I think this was because the charging system was changing from a Bulk charge to an Absorb charge way too early. And I think that was because the Battery Control setup was set to a 100 Ah max. So I got some info on the TR16 Battery Monitor, which I believe is the monitor used by Furrion in my trailer. Using the TR16 instructions, I reset my Ah max to be 128 Ah. My intention was to get the charging system to run the Bulk stage up higher in order to get the battery up to a higher Ah level. After doing this, I saw much better results, that is, I now bulk charge up to around 88%, which is around 113 Ah. It is still climbing, albeit at the much slower Absorption rate. BUT, my battery controller now indicates a higher Ah total. I will be very interested in seeing how this all plays out during our next camping outing. Many thanks for all of the responses.

[tptNbone]

Yes, I agree, and I have checked my MPPT 25A Solar (3 stage) charger, and it is set to support my flooded lead acid batteries. It also can support Lithium batteries as well. But I now have used the instructions for the TR16 battery monitor and have set my "top end" to be 128 Ah. So now with that setting, I have been able to charge up my pair of 12V parallel 64 Ah Interstate marine batteries to about 113 Ah (so far) , a much more realistic result. No more trickle charging at 75 Ah.

[RV Sailor]

Why would you do something so dangerous and why would you potentially destroy perfectly good batteries.

Yes you can introduce a thermal runaway situation, and yes it accepts more charge as it heats up but why would you increase the potential for explosion Especially with acid present.

3 stage chargers are there to prevent this as well as save the life pod your battery. You tiny 75 amp batteries even though 150 amps for two is only 75 usable. A very small tiny pinprick in operating your trailer. If you want to speed up achieving a certain amp Fi hire the SAFEST way is to increase your ah of your batteries or type also. AGM accepts its charge more quickly and lithium in more.

You might as well use an unregulated car battery charger. There is danger in allowing your battery to overaccept its charge. The danger is heat, bulging batteries etc.

I suggest you read up on batteries and charges before you head down this foolish path any furthet