Battery / Solar Question

luthj

Engineer In Residence
Absorbing 15AH and storing it is different . Many of the charge cycles are quite high voltages, so a significant amount of energy is being converted to heat
 

Alloy

Active member
Yea...not really. Lead-acid batteries are chemistry experiments in a plastic box - not precise electronic components. Pretty much what works on one will work on another.

There are a few outliers, such as the Odyssey TPPL Starved Electrolyte design. Since I happen to have the Odyssey Tech Manual open at the moment, let's see what it says...

"The message to be taken from this graph is clear – in deep cycling applications it is important to have the charge voltage set at 14.4 – 15.0V. A nominal setting of 14.7V is a good choice, as shown by
.

Currenty I run a 400Ah AGM bank and a 950FLA bank. Manufacures bulk rate specs are 15.0V AGM and 14.2V FLA. I asked about running less into the AGM but the plates are thicker so the manufacure wants to make sure the plates are utilized.
At 14.2 the FLA need water every 3 months. At 14.7V there would be more gassing and I'd spend more time adding water for what gain?

Both banks have temp compensating chargers. The AGM are 0.13V differential from 70F to 32F. To me that is precise.
 

dwh

Tail-End Charlie
Currenty I run a 400Ah AGM bank and a 950FLA bank. Manufacures bulk rate specs are 15.0V AGM and 14.2V FLA.
Those are both very unusual. Most AGMs specify 14.6v-14.8v and most FLA spec 14.4v-14.6v. What brand/model are those batteries?


I asked about running less into the AGM but the plates are thicker so the manufacure wants to make sure the plates are utilized.
Uh...make sure the plates are utilized...that's a new one on me. Again, what batteries are they?


At 14.2 the FLA need water every 3 months. At 14.7V there would be more gassing and I'd spend more time adding water for what gain?
Less sulphation, shorter charge times. And probably more complete absorption.


Both banks have temp compensating chargers. The AGM are 0.13V differential from 70F to 32F. To me that is precise.
Yea, that's pretty normal. Trojan AGMs spec +.028v for every 10F below 77F, so across a 38F spread that would be a little over a tenth of a volt.

A TENTH OF A VOLT...which is very precisely "not much".

They also spec bulk/absorb of 14.1v-14.7v. So again, not much precision required.

And those same settings would work just fine on just about every other lead-acid battery on the market. (Except gels, which generally spec a max of 14.2v so as not to break down the gelling agent.)
 

burleyman

New member
I was doing some reading on desulfating. To do it in a reasonable time frame (days instead of months) you need current pulses over 2C. These pulses can be really short, but the high current is much more effective than thousands of small low current pulses. This obviously can't be done with any equipment hooked up, as the voltage spikes would nuke sensitive electronics.

The reason you can't just desulfate in an couple hours is that this type of charge current would cause rapid gassing, heating, and battery explosions if not pulsed.
Found out about too-high pulses before frying anything. While using a cheap PWM charge controller with a constant 15v manually programmed charge rate with me in charge of the timed equalization, an 80 watt DC-AC inverter stopped working. Replaced blown fuse. Blew again. I finally realized it was the spikes from the solar charge controller.

I've read about, but never bought into the desulphators that simply use the battery it's connected to for the process. I do now have some faith in a solar panel and PWM controller as good battery maintainers that cause me less electrolyte loss worries.
 

john61ct

Adventurer
Having to regularly replace **water** is a normal with healthy charging. You do not "lose electrolyte" bubbling at the end of the charge cycle.

Reducing water consumed should not be a goal unless your charge sources are harmfully overcharging, out of control.

I too am very curious what batteries have those mfg voltage specs. AGM are the ones require more precision since you can't replace water lost from venting.
 

DaveInDenver

Expedition Leader
I've read about, but never bought into the desulphators that simply use the battery it's connected to for the process. I do now have some faith in a solar panel and PWM controller as good battery maintainers that cause me less electrolyte loss worries.
My thought is that the pulse circuits that run constantly may be trying to reduce sulfation rather than reversing it.

I have one of those Pulse Tech piggyback pulsing boxes and didn't see any evidence it does anything. Used to have a 92 A-hr group 27 West Marine (East Penn) AGM that sat floating for a few years on an Iota DLS-15/IQ4 as a ham station UPS. Being IQ4 it got weekly "equalization", which are really just bumping voltage but may at least overcome self discharge and may be a mild desulfation.

When I tested it using a power resistor it had lost some capacity but was still reasonably healthy. I decided to try the pulsing box to recover lost capacity and about a year later it hadn't gain anything and had lost quite a bit more capacity. Actually it become pretty much useless. So it neither improved nor stopped anything and may have hastened the demise of a mostly healthy AGM.

This obviously was an unscientific sample size of one, so I can't say for sure it helped, harmed or was inconsequential. So while I think pulsed charging may be useful (there's research that supports this and the PWM solar controller observation as well), as a preventive during rest or discharge I'm not sure there's benefit and it may be harmful. I think I'm safe in saying it shouldn't be viewed as a substitute for good charging or shield to abuse a battery.
 

luthj

Engineer In Residence
I have cut apart a few batteries used for backup float service. Pretty minimal sulfation really. Especially compared to deep cycled units like golf carts, floor scrubbers, etc. What usually kills the float service batteries is grid corrosion. This is accelerated by higher float voltages, and higher temps. This is why batteries that are not cycled, but used for backup (24/7 float charge) have a slightly lower float voltage. Batteries in these applications don't die from sulfation, instead the plate grid material corrodes and expands, reducing active material contact, increasing resistance, and eventually electrically isolating whole sections of a cells plate.
 

DaveInDenver

Expedition Leader
Indeed, the little bit of research on the subject indicates pulsing a battery while floating or discharging may result in unnecessary risk of grid contamination and increasing self discharge and heating from momentarily shorting the plates with each pulse, which is what I've assumed was behind my experience. I didn't cut the battery open to inspect it or anything, so it's an unproven theory. The IQ/4 float voltage is 13.6 V, which is right at what East Penn recommended. Elevating the voltage and actually forcing current is reversing the reaction actively. It's important to know where you are in electrochemical process, different outcomes happen with changed conditions. So a long duration constant low current at charging voltage may give most of the desulfation benefits, too, without the pulsing.
 
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