Gasoline generator vs electric generator

[Bud]

'Solar' Generator

[W9TR]

Originally Posted by booster

I think you may be over estimating the alternator charging capability by quite a bit and probably not getting the batteries totally full, which on lead acid batteries, both wet and AGM, takes a lot more time than 2-3 hours no matter how many charging amps you have available. From a true 20% state of charge 2-3 hours will probably get you to about 80-85% full depending on the acceptance of your particular brand, model, and age of batteries. The last 15% charging to true 100% based on the manufacturers criteria (amps of charging to the batteries at absorption voltage in most cases for AGM not voltage) will normally take 4-6 hours and there is no way to speed that up appreciably.



The long term "topping off" of the batteries is where solar does a great job as the charge current is down far enough that it is within the output of the solar to provide in good sun. Many of us on this forum use that method and it works really well. We have a 440ah AGM bank with lots of engine charging available up to 180 amps continuous and more for short times plus 300 watts of solar. We usually shout off the engine charging after an hour or two, maybe longer if we are down more the usual, and turn it over to solar to finish off. Works wonderful and does the very best of battery care by getting all the way 100%.


How are you determining the state of charge of your batteries?

All your points are true. I was keeping it very simple since the OP is new to the wonderful world of batteries. Perhaps too simple, as I didn’t talk about the absorption phase of charging. We have 200W of solar and that’s what gets us to 100%. Works great.

I determine SOC by measuring the battery voltage at night when there is no solar, and very small load.

Happy trails,
Tom

[booster]

Originally Posted by W9TR

All your points are true. I was keeping it very simple since the OP is new to the wonderful world of batteries. Perhaps too simple, as I didn’t talk about the absorption phase of charging. We have 200W of solar and that’s what gets us to 100%. Works great.

I determine SOC by measuring the battery voltage at night when there is no solar, and very small load.

Happy trails,
Tom

You may want to read a few of the discussions on this forum about how AGM batteries take charge. You might find it very interesting.


Bottom line is that battery voltage, even fully rested with no load, is not a good indicator of full batteries. It is a more more reasonably accurate check to see if you are in the top approximately 10% state of charge. Most batteries will meet the manufacturer's "full" voltage requirement because they set it low enough to cover even batteries that are loosing capacity and older. Lifeline says 12.8v, IIRC, but ours will be at 13.1/13.2v when at true full and will still be at 12.8 until about 15% discharged. Lifeline also states that the only way to know they are full charged is to look at the current to the batteries, while charging in absorption. They want .5%C or .5 amps per 100ah of battery capacity. It takes a long time to get there, which we know because we always try to charge to that spec.


Here is a link to the Lifeline technical manual which is an interesting read, IMO.
https://lifelinebatteries.com/wp-con...al-5-06-19.pdf


All this said, a vast majority of people, and equipment, can't charge to that point and control it properly, plus it takes long periods of charging. This also means that most people rarely get there unless they had a very, very shallow discharge with current equipment that is commonly in our RVs. You can get a shore charger and solar controller that will do it automatically, but they are quite spendy. You can also do it manually with a PD charger and a correctly set battery monitor which can be a PITA. Some of the newer chargers in the mass category get closer but don't have settable amp shutoffs and don't eliminate loads from the amps so less accurate.


Bottom line, that we have seen on here is that most people won't invest in the expensive equipment or want to run the system manually, so they live with inaccurate charging, almost all the time to undercharge side. This certainly will shorten battery life but especially in smaller battery banks the costs of replacing more often are OK compared to the costs of upgrading. The major thing most don't do, but should IMO, is to shift their expectations of how "big" their battery bank really is because in reality it is never getting charged enough to get to the rated capacity. I think dropping the top 15% off of rated is probably the best overall choice unless you test the actual capacity by using a battery monitor on your individual system. In real world use, with charging as you describe it, I would expect that you are probably close to 130ah usable capacity, with 20% off the bottom and 15% off the top.


For just alternator charging, you can get a "fairly" easy, moderate cost, somewhat easy to install, method to charge better. If you put an ammeter, best is shunt based, that measures only amps in and out of the batteries and mount the meter on the dash, you can get a pretty good idea of how close full you are. It isn't perfect because the alternator voltage will be constantly changing based on it's internal regulator so not at steady absorption voltage. We have that setup on our van because there isn't a particularly easy way to automate it and take into consideration things like solar contribution while driving. Ours is quite accurate because the alternators run on a remote regulator that I have can lock into absorption voltage by a switch on the dash. I use it every time we drive and it is very easy.

[hdevera]

Eco flow type batteries are very expensive and will not meet most needs for Boondocking. A gas powered generator would be much cheaper and allow for more significant power needs like using a microwave, ac, etc. In order to get an eco flow type to meet boondocking needs (even for short periods) would cost a very pretty penny. Second alternators for Boondocking is a more expensive choice than buying a gas generator but could meet your needs. If you have a Diesel engine, it is not recommended to run the engine at idle for long periods in order to just charge your batteries.

[Davydd]

Second under hood alternators are more efficient in charging batteries in up to about 280 amps per hour, they are more passive, and they mostly re-charge your batteries while driving but have an idle option. They don’t weigh as much nor take up precious space inside your van or under your van when you can have more tank space, maybe a spare tire, or put your batteries. In a campground idling is less obnoxious than running a generator. You don’t have to maintain or carry fuel for a second internal combustion engine.

[hdevera]

Originally Posted by hdevera

Eco flow type batteries are very expensive and will not meet most needs for Boondocking. A gas powered generator would be much cheaper and allow for more significant power needs like using a microwave, ac, etc. In order to get an eco flow type to meet boondocking needs (even for short periods) would cost a very pretty penny. Second alternators for Boondocking is a more expensive choice than buying a gas generator but could meet your needs. If you have a Diesel engine, it is not recommended to run the engine at idle for long periods in order to just charge your batteries.

Don't misunderstand me. I think 2nd alternators are great. I was primarily comparing gas generators to EcoFlow type power systems. However if adding a 2nd alternator is in your mindset, than my comments on that would apply.

[themexicandoctor]

Originally Posted by booster

You may want to read a few of the discussions on this forum about how AGM batteries take charge. You might find it very interesting.


Bottom line is that battery voltage, even fully rested with no load, is not a good indicator of full batteries. It is a more more reasonably accurate check to see if you are in the top approximately 10% state of charge. Most batteries will meet the manufacturer's "full" voltage requirement because they set it low enough to cover even batteries that are loosing capacity and older. Lifeline says 12.8v, IIRC, but ours will be at 13.1/13.2v when at true full and will still be at 12.8 until about 15% discharged. Lifeline also states that the only way to know they are full charged is to look at the current to the batteries, while charging in absorption. They want .5%C or .5 amps per 100ah of battery capacity. It takes a long time to get there, which we know because we always try to charge to that spec.


Here is a link to the Lifeline technical manual which is an interesting read, IMO.
https://lifelinebatteries.com/wp-con...al-5-06-19.pdf


All this said, a vast majority of people, and equipment, can't charge to that point and control it properly, plus it takes long periods of charging. This also means that most people rarely get there unless they had a very, very shallow discharge with current equipment that is commonly in our RVs. You can get a shore charger and solar controller that will do it automatically, but they are quite spendy. You can also do it manually with a PD charger and a correctly set battery monitor which can be a PITA. Some of the newer chargers in the mass category get closer but don't have settable amp shutoffs and don't eliminate loads from the amps so less accurate.


Bottom line, that we have seen on here is that most people won't invest in the expensive equipment or want to run the system manually, so they live with inaccurate charging, almost all the time to undercharge side. This certainly will shorten battery life but especially in smaller battery banks the costs of replacing more often are OK compared to the costs of upgrading. The major thing most don't do, but should IMO, is to shift their expectations of how "big" their battery bank really is because in reality it is never getting charged enough to get to the rated capacity. I think dropping the top 15% off of rated is probably the best overall choice unless you test the actual capacity by using a battery monitor on your individual system. In real world use, with charging as you describe it, I would expect that you are probably close to 130ah usable capacity, with 20% off the bottom and 15% off the top.


For just alternator charging, you can get a "fairly" easy, moderate cost, somewhat easy to install, method to charge better. If you put an ammeter, best is shunt based, that measures only amps in and out of the batteries and mount the meter on the dash, you can get a pretty good idea of how close full you are. It isn't perfect because the alternator voltage will be constantly changing based on it's internal regulator so not at steady absorption voltage. We have that setup on our van because there isn't a particularly easy way to automate it and take into consideration things like solar contribution while driving. Ours is quite accurate because the alternators run on a remote regulator that I have can lock into absorption voltage by a switch on the dash. I use it every time we drive and it is very easy.

Excellent Information - I have suspicion that my system is doing that.

Reading your posts over the years & talking to Harry N* recently, its all about "gaming the system, sometimes manually, or living within the compromise settings the manufacturers build in (not at the AGM Lifeline battery), but the input of Charge Controllers, Inverter Chargers, etc.

*if you haven't already talked, both of you amongst others are the Giants of Battery Knowledge here.