Long Question on how Converters Sense Battery Voltage.

[horton333]

Hi:

My normal 2 weeks per year of dry camping will be more like 2 months this year I expect so I am investing in a better 'off grid' setup and the single output voltage converter has to go. For reference 220 AHs of AGM will be the battery. Hence two, one rather detailed, questions.

Questions 1:
Researching converters there seem to be several good multi-stage models on the market, but there is one thing that is bugging the EE in me. There seem to be two major classes. One class have an internal transfer relay, and when on AC the battery is charged by a separate circuit board thru an isolated circuit. The issue is these all seem to be far low amperage for my setup as I really want no more than say 2 hours per day charging (75 AHs is what I guess I need per average day).
The models that have the 75-100 Amps I want all seem to have a single 12 volt output and this is shown in the manuals as going to both battery and the 12 volt accessories, so this leads to question 1. With some of the load being the battery and some being lights or whatever (and variable) how does the charger know when to scale back the voltage when fully charged? If it just guesses on current draw I can see it never coming off 14.4 volts. Is there something I missed that allows them to accurately know where the battery charge level is at to lower the voltage when charged or _______? If the AGMs can handle sustained 14.4 volts, my motorcycle which puts out 16 volts leads me to believe they may be able to but the manufacturers seem to say no, then maybe I would get almost the same result (its only 55 amps, a waste with all that battery capacity and a 2.2 kw generator)by just cranking the voltage on the existing converter?

Question 2)
I have not seen any units that have remote voltage sensing, only temperature. Do you know of any out there that sense the voltage at the battery?
John

[landyacht318]

Not Blue, It's a little silver rectangular pill that takes over when the automatic preprogrammed bigger silver rectangle directed blood flow to less enjoyable parts.

But for some, this is 'just fine'

Better to keep 'batteries', happy, with all tools available, and the knowledge how to use them properly when the situation calls for them.

And there are times just to turn off the hearing aid and Nod.

[jrnymn7]

So, a new term has been coined... FLC's = frontal lobe chargers, nice!

Isn't there a little blue pill available for 'premature efloatulation', or is that for when your converter just can't seem to get it up? 🙂

[jrnymn7]

I've read some agm's can handle 4XC. (not to be confused with C/4).

And are not agm's susceptible to changes in temperature, just like fla's? (not to be confused with floridians).

[landyacht318]

What brand of AGM?

Generally, converters do not excel at feeding any given battery all it can accept during limited generator run times.

AGMs tend to be lumped together as to their charging requirements but they actually vary widely as to what the AGM manufacturers want and recommend for best life and performance during the lifespan of their batteries.

For example some lesser $$ AGM's say to limit Amps to NO MORE than 30 for a hundred amp hour battery, while Odyssey says when their battery is deeply cycled, Feed their Hundred amp hour battery No LESS than 40 amps initially until 14.7v is reached and then 14.7 is to be held for 4 hours or until amps required to hold 14.7v fall below 0.5amps.

Lifeline AGM basically says to Feed them as much amps as you can muster but do not exceed 14.4v and terminate charge when that 100 AH battery needs no more than 0.5a to hold 14.4v

So trying to find the converter which best fits your AGM's is not just a Powermax vs PD vs Iota.

In come the frontal lobe chargers, or adjustable voltage power supplies which have gained favor with many of us. We choose an end voltage and the power supply feeds the battery all it can provide and as much as the battery can accept at that voltage, until battery voltage nears that end( Absorption) voltage.

COnverters suffer from 'premature efloatulation', dropping voltages to 13.6 or 13.2 well before the battery is done accepting what it wants at 14.X as as such, recharging slows to a crawl, while you waste gas and annoy everything around who can hear or smell your generator.

And here you will get those who love to proclaim how quiet their generators are, or that nobody is around anyway, and bla bla bla chest thump, and their system works 'just fine' and their batteries last years and years in their quest for approval of their methods, without realization or care that everyones needs, uses, and desires differ.

Beware of "just fine!". Often it is synonymous with "has not failed yet". Often it means " I have no real Idea, nor do I care, and you should do the same".

This 'Premature efloatulation' is fine when one has a power pedestal to take as long as needed to shoehorn the last amphour back into the battery, but on a generator it is a whole different game.

There are a lot of ways to skin a cat, and no one right way for everybody, or every cat.

I choose to have a 41 amp adjustable voltage power supply( MeanWell RSP-500-15) for when I have ~120 vAC available, 198 watts of solar does the majority of my recharging, and I make sure my alternator is not limited by thin cabling between it and the thirsty battery and I do not fear letting it feed either battery 75+ amps upto the 14.9v my vehicle's voltage regulator allows.

I have one of those hungry AGM'S that loves huge recharging currents, and I only Deep cycle it when I have enough miles to drive or AC available to feed it 40+ amps, and I mostly cycle a single flooded battery to 35 to 50% or deeper the rest of the time. 11.25 out of 12 months a year and likely more than 27 out of every 30 days, continuously.

And it works, "just fine :)"

[jrnymn7]

MEXICOWANDERER wrote:
I like the model that has the "Frontal Lobes" option...

x2

[horton333]

Thanks for all the info, - got stuck in bad weather last night and behind an accident that closed the highway for hours with no way off, got home and the morning paper was already there 😞 so I'm off to a slow start.

I will send a message to Randy @ best converter, but it sounds like smkettner's details on how they 'guess' gives me what I was looking for. Of course it's going to be much better than what I have now and I guess the manufactures are saying the extra cost for dual circuits and remote sensing (hey even better car alternators have that) is not justified. Fair enough.
If I learn anything significant more I'll pass it back.

[brulaz]

smkettner wrote:

...

For best voltage sense install the new converter close to the battery with #4 wire.

For true flexibility you need a good solar controller. They have all features you need.

I ended up installing a separate Progressive Dynamics converter/charger close to the battery and leaving the old WFCO converter in place.

When on 110V I switch the batteries off the WFCO (leaving the WFCO to run the 12V appliances) and let the PD charger do its thing to the batteries when there's not enough sun. When there's enough sun the MPPT controller gets involved with the batteries too.

[MEXICOWANDERER]

Present a given voltage to the battery and Ohm's Law takes care of the rest.

REMOTE SENSING IS USED ON CIRCUITS THAT HAVE UNNATURAL VOLTAGE DROP.

If you need to compensate for drop you've already lost the game.

[Old-Biscuit]

smkettner wrote:
They all sense voltage at their own output terminals.

Progressive Dynamics uses a timer to reduce voltage.

IOTA drops voltage 15 minutes after hitting 14.6 then uses a variable timer to go to float.

PowerMax drops as soon as it hits 14.6 volts.

For best voltage sense install the new converter close to the battery with #4 wire.

For true flexibility you need a good solar controller. They have all features you need.

Simple straight forward answer.........I like it!

[NinerBikes]

horton333 wrote:
Hi:

My normal 2 weeks per year of dry camping will be more like 2 months this year I expect so I am investing in a better 'off grid' setup and the single output voltage converter has to go. For reference 220 AHs of AGM will be the battery. Hence two, one rather detailed, questions.

Questions 1:
Researching converters there seem to be several good multi-stage models on the market, but there is one thing that is bugging the EE in me. There seem to be two major classes. One class have an internal transfer relay, and when on AC the battery is charged by a separate circuit board thru an isolated circuit. The issue is these all seem to be far low amperage for my setup as I really want no more than say 2 hours per day charging (75 AHs is what I guess I need per average day).
The models that have the 75-100 Amps I want all seem to have a single 12 volt output and this is shown in the manuals as going to both battery and the 12 volt accessories, so this leads to question 1. With some of the load being the battery and some being lights or whatever (and variable) how does the charger know when to scale back the voltage when fully charged? If it just guesses on current draw I can see it never coming off 14.4 volts. Is there something I missed that allows them to accurately know where the battery charge level is at to lower the voltage when charged or _______? If the AGMs can handle sustained 14.4 volts, my motorcycle which puts out 16 volts leads me to believe they may be able to but the manufacturers seem to say no, then maybe I would get almost the same result (its only 55 amps, a waste with all that battery capacity and a 2.2 kw generator)by just cranking the voltage on the existing converter?

Question 2)
I have not seen any units that have remote voltage sensing, only temperature. Do you know of any out there that sense the voltage at the battery?
John

Battery chemistry limits amperage and charge rate. The closer to topped off charged you are, the less chemicals in the form of sulfur on the plates there are to go back into the AGM solution, there is just less ions of sulfur to react and take from the plates and get back into the Glass Mats. This creates more internal resistance to charging... which is what the charge controller senses and measures.

If you stick with AGM batteries, something like a Progressive Dynamics 9245 or 9255 with charge wizard pendants, that limits bulk voltage to 14.4V is ideal. If you were running typical Lead Acid with vent cap batteries like deep cycle golf cart batteries, then something that you can set up like an Iota that generates 14.8V is more desireable for NON AGM batteries.

If you have AGMS, look at the spec sheet of the manufacturer of the batteries and see what Vabs is rated at. If it's 14.4V like most AGMS, you know which model charge controller to get.

[BFL13]

MEXICOWANDERER wrote:
I like the model that has the "Frontal Lobes" option...

Don't buy anything unless it has "thunder protection" and a re-settable breaker for that.

[MEXICOWANDERER]

I like the model that has the "Frontal Lobes" option...

[time2roll]

They all sense voltage at their own output terminals.

Progressive Dynamics uses a timer to reduce voltage.

IOTA drops voltage 15 minutes after hitting 14.6 then uses a variable timer to go to float.

PowerMax drops as soon as it hits 14.6 volts.

For best voltage sense install the new converter close to the battery with #4 wire.

For true flexibility you need a good solar controller. They have all features you need.

[BFL13]

The battery only "accepts" the amps it can handle, so the charger's voltage can remain the same while the battery is actually self-controlling what it uses.

When the 12v system has various loads running off the converter, they get first call on the output and the battery gets whatever is left over. (proper explanation is wrt the voltage differences between the loads and the converter being more than the difference between and the battery and the converter---or something like that!)

Modern converters do not have that transfer switch thing or relay like the old Magnetek 6300s. Your choice is between a single stage or a multi-stage modern one and how many amps size. Note that the amps size limit is how many watts (VA actually) your generator can do

If you get a power factor corrected charger you can do more amps size on the same generator. In the 75-100amp size range, the PowerMax converters do have PF correction. Other brands like PD and Iota may have features you want instead if generator is not the limit.

Mex here, has noted that you do get more amps even with the single stage converter because AGMs accept more at the same voltage than Wets do, which is interesting if you are choosing to upgrade from a single to a multi just to get more amps and you now have Wets. of course you can do both--get AGMs and the multi.