10 replies to this topic

[Desert Scruff]

I have a question regarding charging my two Deka AGM batteries (replacements for the OME pair that failed in less than two years).

 

Deka says you must compensate for the temperature when charging, and I assume that is true for all AGM batteries, and maybe all lead acid batteries. Lower charging voltage when hot and higher when cold.

 

I have a 2016 Fleet with Iota charger/converter, solar panels and a Victron controller, Victron monitor, and a Victron unit in the battery box that relays to the controller the battery temperature so the compensation can be made.

 

But for several months in the winter the camper is covered, the solar system obviously not in play, and when plugged in to shore power the Iota charger will maintain the batteries but there is no temperature compensation—or is there? The temperature in the battery box is often below freezing.

 

Is the Iota charger wired through the controller? That would be the only way I see to have temperature compenation when the Iota is charging. I’ve called Four Wheel Camper but haven’t yet received a return call.

 

If the Iota charger isn’t wired through the controller, as I’m assuming it’s not, is the lack of temperature compensation shortening the life of the AGM batteries?

 

I understand I can disconnect the two AGM batteries from the camper electrical system and allow them to rest for the winter. The voltage now is 12.6 which is about 75% of full charge. 

 

 

[Vic Harder]

According to Deka's www page, the temp comp for their AGM batteries is ‐0.018 V/°C.  Meaning that at -10*C (14F) the charging voltage should be 35*1.018 = -0.63 volts different than the nominal charging voltage.

 

I just looked at the IOTA tech specs, and they don't mention temp comp anywhere.  Nor do they appear to sell a temperature sensor, so I am guessing that they do NOT offer temp compensation.

 

I also don't think that they run the IOTA through the solar controller.

Edited by Vic Harder, 07 January 2020 - 03:43 AM.

[longhorn1]

We have Deka's and live in Indiana where we can get temps from 0 - 32. Never had an issue. Camper is stored outside and covered, so roof top solar isn't in play. Every 5-6 weeks I plug in the portable panel for the day. Never gets below 12.7. I charge 2-3 times from later October to early March.

[Desert Scruff]

FWC says its charging system is not set up to have temperature compensation. FWC says my 2016 camper has the IQ4 on the Iota charger (news to me). Deka is the AGM battery FWC now installs and Deka knows how FWC's charging system works, so how important is it when Deka says temperature compensation is required? FWC also says with my charger just plug in to shore power and let the charger maintain the AGMs through the winter. 

[Vic Harder]

FWC says its charging system is not set up to have temperature compensation. FWC says my 2016 camper has the IQ4 on the Iota charger (news to me). Deka is the AGM battery FWC now installs and Deka knows how FWC's charging system works, so how important is it when Deka says temperature compensation is required? FWC also says with my charger just plug in to shore power and let the charger maintain the AGMs through the winter. 

Note that I tend to overload people with data when asked questions like this... so, feel free to skip some parts!

 

According to IOTA's document on the IQ4 - https://www.iotaengi...lib/iq4spec.pdf

the voltages it uses are:

 

Bulk - 14.8v

Absorption - 14.2v

Float - 13.6v

 

According to DEKA, at 60-70*F their AGM batteries want:

Bulk - 14.45v - 14.75v 

Float - 13.55v - 13.85v

 

This means that at 70*F, the IOTA IQ4 is very slightly overvoltage, which isn't really a big deal.  And at the same temp the float voltage is in range of what DEKA wants.  Yeah!

 

Now, let's look at what happens at 14*F.  As I calculated in my first post, they want .63v more at that temperature.  That yields:

Bulk = 15.08 - 15.38v

Float = 14.18 - 14.48v

 

Meaning that the IOTA IQ4 will not do a great job of either bulk/absorb or float charging your batteries when they are cold.

 

More disturbing is that DEKA clearly states on page 2 of the document reference below that their warranty is void if you don't use a temperature compensating charger.   

 

"Important Charging Instructions

The warranty is void if improperly charged. Use a good constant potential, temperature-compensated, voltage-regulated charger"

http://www.eastpenn-...s/base/0139.pdf

 

I use a Noco Genius G26000 battery charger when I need to top up via shore power.  It has temp comp. 

https://no.co/media/...et-g26000_1.pdf

[Desert Scruff]

Not too much data, Vic, and thanks for your research. It's interesting that Deka sells its batteries for use in a setup that doesn't provide temperature compensation. AGM batteries are becoming common in cars nowadays, so I'm told, because of no maintenance required. I doubt there is any temperature compensation in those vehicles, but maybe I'm wrong about that. 

 

The charger you are using puts out about 25 amps. Is that so you can get your batteries to 100% in just a couple of hours?

 

I have an older Noco Genius charger but unfortunately it does not offer temperature compensation.

 

Do you have a thought on the ill effect on a battery not maintained to the required voltage? 

[Vic Harder]

Not too much data, Vic, and thanks for your research. It's interesting that Deka sells its batteries for use in a setup that doesn't provide temperature compensation. AGM batteries are becoming common in cars nowadays, so I'm told, because of no maintenance required. I doubt there is any temperature compensation in those vehicles, but maybe I'm wrong about that. 

 

The charger you are using puts out about 25 amps. Is that so you can get your batteries to 100% in just a couple of hours?

 

I have an older Noco Genius charger but unfortunately it does not offer temperature compensation.

 

Do you have a thought on the ill effect on a battery not maintained to the required voltage? 

Both AGM or good old fashioned flooded lead acid (FLA) batteries need temperature compensation to last as long as possible.  Don't blame DEKA here, they just make the batteries.

 

I chose the 26A version to match the capacity of the IOTA (30A) used by the factory.  Also, battery makers also specify an "ideal" charge current of around 10-20% of the total capacity of the battery bank.  I have 200AH (LiFePo4) in the new camper, and had 275AH (AGM) in the last camper.

 

I have a fondness for gauges and for knowing what's going on in the rig.  I have monitored up to 90A going into the camper batteries from my alternator, and my 320W solar panel can pump out 25A+ on a good day.

 

Big thing for long term winter storage is to not let the battery get drained, or it will freeze.  

 

Assuming that the IQ4 will think your battery is in float stage at 14*F it will be giving it 13.6V.  IF it had temp comp and IF you could adjust it to what the DEKA wants, it should be feeding it 14.2V.  It isn't.  OK, so what?

 

Acccording to the table on page 13 of the DEKA document I linked to earlier, 12.6v is 100% SOC at 68*F.  Adjust that for 14*F and we get 13.23v.  

 

Your charger is giving it a tiny bit more than that, so I suspect you are just fine leaving the camper parked with the IOTA IQ4.  Is it ideal, not at all.  And if you were using it in the winter, I suspect the batteries wouldn't last as long as designed.

[Desert Scruff]

Again, thanks Vic.

 

Since you are not able to charge a lithium battery at 32°F or below, and you live in Calgary, how do you deal with that? Keep the batteries warm some how?

[Vic Harder]

Again, thanks Vic.

 

Since you are not able to charge a lithium battery at 32°F or below, and you live in Calgary, how do you deal with that? Keep the batteries warm some how?

Good question. 

 

The batteries are in my living space. It rarely gets that cold in there!  

[Oilbrnr]

Have you investigated Victron's IP65? I think it might tick all your winter storage needs including ongoing temp compensation and weekly storage cycle algorithm. And when out of storage, you'll have a competent portable charger for a variety of uses...

 

I'm actually thinking about ordering a second one.