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 > Floating Batteries in Very Hot Weather

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mena661

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Posted: 01/25/13 09:51pm Link  |  Print  |  Notify Moderator

Some days in the summer the temperature of my batteries, as measured by an IR thermometer, can get as hot as 110F/43C. I have a rare temp compensated converter and the float voltage is 13.2 in those conditions. Is that too high? Should I even float at if it gets that hot?


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HiTech

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Posted: 01/25/13 09:53pm Link  |  Print  |  Notify Moderator

mena661 wrote:

Some days in the summer the temperature of my batteries, as measured by an IR thermometer, can get as hot as 110F/43C. I have a rare temp compensated converter and the float voltage is 13.2 in those conditions. Is that too high? Should I even float at if it gets that hot?


What specs for the batteries? What I can find says to subtract .056 vpc from a nominal 13.2 float that temperature, and that 113 degrees is the maximum operating temp, but that may be ambient and not the battery temp. But regardless, 13.2v sounds high since it is nominal at 77 degrees.

Or you could tropicalize them!

Jim

* This post was edited 01/25/13 10:01pm by HiTech *

mena661

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Posted: 01/25/13 10:15pm Link  |  Print  |  Notify Moderator

HiTech wrote:


What specs for the batteries? What I can find says to subtract .056 vpc from a nominal 13.2 float that temperature, and that 113 degrees is the maximum operating temp, but that may be ambient and not the battery temp. But regardless, 13.2v sounds high since it is nominal at 77 degrees.

Or you could tropicalize them!

Jim
HERE says subtract .028 VPC for every 10F above 80F. And the float charge is 13.5V. So that would be 12.8ish. Yeah, still too high. Is that .4V that critical though?

HiTech

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Posted: 01/25/13 10:21pm Link  |  Print  |  Notify Moderator

Not sure. The spec I saw said 13.2 v at 25 c and .028 vpc for every 10 degrees C. I found the same kind of conflicting specs for my battery as well. I think a factor is how long at that temp? Does it cool down significantly overnight? How many hot days in a row? Does it float all day or only briefly?

Jim

mena661

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Posted: 01/25/13 10:33pm Link  |  Print  |  Notify Moderator

It'll be 100+ in July and August. It does cool into the 70's and 80's overnight though. Temps kinda ramp up around here. It won't do 102, 101 then 110. It'll ramp up to there. Mid to high 100's is pretty typical for summer here. We'll have some 108 or higher temps. Really hot for us is 110-112, more than that is record territory. And it's 100+ for most of the day too. Temps rise really fast in the morning and flatten out over the day. Seriously, it can be 70 at 6am and 95+ by 9 am.


EDIT: Oh yeah, I leave them on float 24/7.

BFL13

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Posted: 01/26/13 07:29am Link  |  Print  |  Notify Moderator

People maintain batts with solar, where no charging takes place overnight. That's their "float." So if you had your shore power on a timer to just charge overnight and be off during the hot part of the day, your "float" should also maintain the batts just as well as solar does?


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pianotuna

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Posted: 01/26/13 07:38am Link  |  Print  |  Notify Moderator

Hi mena,

Yes, you should reduce the float voltage. I think the Rogue 3024 has details on the voltage vs temperature.

Email the battery maker and ask their recommendation for temperature compensation?


Regards, Don
Full Time in a Kustom Koach Class C 28'5", 256 watts Unisolar, 875 amp hours in two battery banks 12 volt batteries, 2500 MSW watt inverter.

BFL13

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Posted: 01/26/13 09:11am Link  |  Print  |  Notify Moderator

Here is a note on that. Not sure of application to this case.

http://www.engineersedge.com/battery/high_temperature_battery.htm

MEXICOWANDERER

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Posted: 01/26/13 01:16pm Link  |  Print  |  Notify Moderator

BFL13, That is an EXCELLENT link and whomever wrote that article knew what they were talking about.

50C, 122F is what I determine is the "limit" where safe charging will occur.

But by using common sense a pair of L-16 batteries can be charged even when electrolyte temps are at 113F. The key is to LIMIT CHARGING CURRENT.

I would not be afraid to charge the L-16's at a 25 ampere rate. But! I would play an IR thermometer (thermocouple) on the lead terminals occasionally and when the temperature starts increasing and proceeds to rise to 115F, I would back the charge rate down to 10 amperes.

With a 5% antimony L-16 at 113F I would float it at 12.9 IMHO

This is where a temperature corrected hydrometer will save your butt.

mena661

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Posted: 01/26/13 02:10pm Link  |  Print  |  Notify Moderator

Then I'm going to have to figure out how to get 12.9V out of a float charger during those times of the year. I do have a couple of those HF floaters. I've noticed they'll creep up to near 14V over the course of a few weeks. Any ideas on how I can modify those for summer use?

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