Community Forums

757driver · 12-02-2016, 10:10 AM

Quote:

Originally Posted by photraveller

AGM's usually have lower resistance, so it's easier to push current to them faster. The real question is that a good thing for the battery?

Temperature sensors and compensation by the charger is questionable on AGM. Due to their design, AGM's don't dissipate heat nearly as well as flooded.It is easy to over heat the inner cells of an AGM battery, if the charger doesn't switch to different compensation curve for AGM's vs. flooded.

Steve

Steve,

Makes sense. If there is no liquid touching the case walls then the heat generated by charging will not transmit through as easily. This is also a good reason to be at or under the manufacturers recommended charge rate and not crank the Magnum inverters to 100% rate of charge thinking more is better.

photraveller · 12-02-2016, 12:10 PM

Correct, Unless you don't have the time to recharge before getting back on the road, I see no reason to push max rated current.

In flooded you have a lot of free water to stir up and cycle around each cell. AGM's all the electrolyte is captured in glass mat (think fiberglass batting). Definitely a poor conductor of heat.

On AGM's, I've seen temperature differentials of up to 10F on std automotive cranking batteries from the center of the plate to the edges.

I can only guess at the differential on the L16's, but I am sure it is much higher.

Has anyone watched battery box temperatures on the 2017's?

I know we have a little ventilation, but with them being buried and fully enclosed it is on my list to monitor. With my Aspire I only have 2 batteries down there, I would expect it to be worse with 4 L16's.

Steve

MRUSA14 · 12-02-2016, 01:22 PM

Quote:

Originally Posted by photraveller

On AGM's, I've seen temperature differentials of up to 10F on std automotive cranking batteries from the center of the plate to the edges.

Is 10F from center to edge enough of a differential to cause an overheat problem? It doesn't seem like a very significant number to me.

photraveller · 12-02-2016, 03:16 PM

Quote:

Originally Posted by MRUSA14

Is 10F from center to edge enough of a differential to cause an overheat problem? It doesn't seem like a very significant number to me.

Yes it is, especially if you push the temperature every time you recharge, which is what temperature compensated charging can do.

That 10 degrees was showing up as failure modes, in the smaller automotive batteries.

With golf cart sized batteries I would expect the temperature difference to be same to slightly larger. With the L16's I fear the difference could be 50-100% more than 10F.

You are doing a slow cook on something like a wet/damp sponge. Think the opposite of the Samsung microwaves, it doesn't take much difference to dry out / burn one section of a cookie, while the other remains overly moist.

Now, all that said, the manufacturer should have chose max temperatures with all this in mind. However, in reality, max temperature is supposed to be a moving target based on ambient temp. Plus the manufacturer can't take into account how our batteries are enclosed in battery boxes.

So lowering max charge current (1st choice) or max temperature allowed (2nd choice) is a good thing to do.

Again, all IMHO,

Steve

brobox · 12-02-2016, 04:29 PM

Steve and Don, I really appreciate you both sharing your knowledge on batteries. Many of us take batteries for granted, until you loose a $2,500. set of batteries prematurely. When that happens a lot of whys start coming forward. From reading your posts I am getting a lot of those answered and it is greatly appreciated, thank you.

photraveller · 12-02-2016, 06:56 PM

Thanks Chuck !

I'm just trying to follow the lead of you and others on this forum that have been so helpful to me.

Steve

757driver · 12-02-2016, 07:02 PM

Thanks Chuck, with what is coming out of Entegra/PJ, this site needs some practical, sound advice.

brobox · 12-02-2016, 07:35 PM

Quote:

Originally Posted by 757driver

Thanks Chuck, with what is coming out of Entegra/PJ, this site needs some practical, sound advice.

The sad part is the forum is small percentage of Entegra owners and PJ graduates. More than 1/2 that were in the class I was in, went out and equalized that night. Thanks to you and your emails I did not and told a few others to check Discover Battery's web site before they equalized. .

Mwoodofd · 12-03-2016, 05:48 AM

Quote:

Originally Posted by brobox

Steve and Don, I really appreciate you both sharing your knowledge on batteries. Many of us take batteries for granted, until you loose a $2,500. set of batteries prematurely. When that happens a lot of whys start coming forward. From reading your posts I am getting a lot of those answered and it is greatly appreciated, thank you.

X2 - I have been following all the battery and power threads here learning all about our batteries and the systems we have onboard to manage them. Many thanks for your insight.

brobox · 12-03-2016, 06:09 AM

Quote:

Originally Posted by photraveller

Thanks Chuck !

I'm just trying to follow the lead of you and others on this forum that have been so helpful to me.

Steve

Thanks Steve. We all have knowledge from previous lives to share. Yours a vast amount battery knowledge, mine a jet mechanic, Don's the knowledge of how all the systems work, Gene a previous big rigs owner, Pat an industrial arts teacher with GREAT mod ideas, and many others that bring knowledge to the table The more we share, the more we all learn.

I remember my Dad telling me after they went fulltime, that RV'ers were the most helpful people he had ever met.