Adjustible Solar PV Controllers

[john61ct]

Originally Posted by conachair

Disagree. Trojan told me "The finishing rate for a fully charged battery is 1-3% of the total capacity of the battery bank (2.25A - 6.75A)" - on my batteries at the temperature today there's still power going in at 2.25v, lots still going in at 6.75v.

I believe you are saying Trojan specs .01-.03C as endAmps

That is not true, that may mean hours away from 100% Full.

Trojan specs an additional finishing charge **after** Absorb reaching .01C (.03C at the low end)

Using constant current at .03C (.01C) until voltage hits 16.2V (14.7).

The "contact us if charge time is limited" will get you advice to push a higher voltage than what is in the docs.

Maine Sail recommends 14.8-15V for Trojan absorb, and remember that is at 77°, before temp compensation.

Sticking to a lower gentler profile will reduce longevity.

[john61ct]

Originally Posted by conachair

Again it's not the current - it's the change in current

That is how Deka specs it.
> Current change over 1 hour period of less than 0.1A

Useful when FLA batts age means they just never get to the spec'd endAmps.

[noelex 77]

Originally Posted by conachair

Yes, of course it does - obvious from the data plots posted, point is the current acceptance is still lowering until it gets below the 1% you are considering as full - my point is I don't think 1% is full, maybe very nearly but not quite. In these trojans anyway.

I don’t think we fundamentally disagree.

I believe it is accurate to suggest that leaving the battery at absorption voltage past 1-3% is squeezing a little more SOC into the battery. The cut off for a truely full battery probably occurs at a lower percentage (or after sometime on float), but we both agree that a battery accepting charge does not mean the SOC is necessarily rising.

The other consideration is that even if we accept keeping the battery at absorption voltage beyond the 1-3% is slightly increasing the SOC, does this mean that it helping battery life?

All (or at least almost all) the battery manufacturers recommend for the best battery life terminating the absorption charge when the end amps have reached 1-3%. I am inclined to agree with them, although down to 0.75% or even 0.5% is perhaps not unreasonable with new flooded lead acid batteries in a cyclic capacity if the end amps are being carefully monitored and the water levels kept up.

[john61ct]

The point of pushing higher / longer **is** longevity, rigorously avoiding PSOC abuse,

not trying to squeeze in a few more AH of storage capacity.

As I pointed out above, .01C at Absorb is not endAmps for Trojan, just the point where the higher-voltage "finishing charge" should **start**.

I've never heard of any maker recommending stopping earlier than .02C

The "default", pending detailed specs from the maker, should IMO be .005C.

With the proviso for more sensitive chemistries and aging banks.

[noelex 77]

Originally Posted by john61ct

Maine Sail recommends 14.8-15V for Trojan absorb, and remember that is at 77°, before temp compensation.

Sticking to a lower gentler profile will reduce longevity.

I agree. Aggressive voltage set points are, I believe, a better solution than excessively long absorption times.

Many solar controllers err on the side of slightly over reading the voltage (because this is safer). Few controllers take into account the voltage drop in the wiring between the controller and the battery, and the temperature compensation is sometimes at the controller rather than the battery. This is exacerbated because the battery manufacturers often recommend voltage set points between cyclic and standby values.

All the above factors have an effect in the same direction rather than cancelling each other out. Ideally, each of these factors can be accurately compensated for, but setting the battery voltage set points at least on the high side of the manufacturer’s recommendations, and even slightly above, is not a bad starting point for those without electrical knowledge.

[john61ct]

Well, I'm not saying the higher voltage is **instead of** adequate absorb time.

It does makes getting to 100% a bit faster and more certain.

The key to me, is making getting there at least a few times per week the **top** priority in tweaking the charge profile.

The cost of getting there is going "too long" - sometimes, and not by much - but that is better than getting to Full only once a week.

"Excessive" hold time is by definition harmful.

With a high-amp charge and high-CAR bank, 4-5 hours AHT may be "just enough".

Getting to Absorb in the first 30 minutes, where a total of 6+ hours charge time is required, is very common.

[noelex 77]

Originally Posted by john61ct

Getting to Absorb in the first 30 minutes, where a total of 6+ hours charge time is required, is very common.

The charge time is not important it is the absorption time that is relevant. Five and half hours at absorption voltage is a very long time.

[john61ct]

It takes as long as it takes, how long we **think** it "should" take is not relevant.

My main point was that we have no direct control over when the CC/CV transition takes place. That is up to a mix of objective factors, including bank chemistry's CAR, SoC, resistance, voltage and amps.

In getting a large bank from say 50% to true 100%, increasing the amp rate has relatively little impact on the total time it takes.

It will only be less than 4-5 hours if it is a small bank and very shallowly discharged.

Same to a large degree going from FLA to AGM, maybe save 30-40 minutes.

If Bulk/CC is finished in under an hour, then the remaining hours by definition are spent in Absorb/CV.

Absorb will be much shorter if getting to the transition takes hours, as is the case with low charge rates, say 80A for a 600AH bank.

I apologize if I've already linked within this thread, to this excellent and detailed report by Maine Sail showing multiple examples at different charge current rates.

https://marinehowto.com/how-fast-can...ry-be-charged/

Well worth reading in detail, not just for noobs.

[rgleason]

Originally Posted by mitiempo

What is the voltage of your solar panels? The Genasun boost for 12 volt nominal banks appears to have a maximum panel voltage of 13.

I don't understand how that can work. The Genasun boost controllers are really designed to charge 36 or 48 volt systems.

One thing to keep in mind though is that with a smaller solar installations the batteries will not get to absorption until they are over 90% charged, often as high as 95% charged. Absorption time is really not an issue in this situation.

Battery banks will typically be about 80 to 85% charged with a larger charger.

Yes Alternator will charge to 80-85%
Solar will charge batteries to 98% over 1.5 days.
225ah battery bank.

Solar PV will probably be Soliban SR https://www.bruceschwab.com/solar-po...ian-flex-high/

For SR-62watt
Cells no. 14
Voc 8.9 V
Vmp 7.2 V
Isc 9 A
Ipm 8.6 A
For SR-50watt it is likely to be a little less.

[rgleason]

Conachair wrote:

it's the change in current - why not look to when the current acceptance stabilizes? It's not that the battery is accepting charge, it's that the charge it is accepting is continuing to lower, it's not done yet. T

Your values for Trojans are exactly as stated by the manuf.


I agree with your statement. If we have good measuring tools with history, we should be looking at "delta C" change in current and when it goes to near stable or "0" (including temperature compensation) then the batteries are charged.

[rgleason]

So for me the question is really quite basic, by using the Genasun GVB Boost controllers with these panels, would charging end properly such that the 225ah bank is full at 100%SOC?

I don't believe they can be adjusted but I might be wrong.


Just noticed that Max recommended panel Vmp 13v
Bulk 14.4v
Absorp 14.2v
Float 13.8v
with battery temp compensation.

[newhaul]

Originally Posted by rgleason

Yes Alternator will charge to 80-85%
Solar will charge batteries to 98% over 1.5 days.
225ah battery bank.

Solar PV will probably be Soliban SR https://www.bruceschwab.com/solar-po...ian-flex-high/

For SR-62watt
Cells no. 14
Voc 8.9 V
Vmp 7.2 V
Isc 9 A
Ipm 8.6 A
For SR-50watt it is likely to be a little less.

is there actually a legitimate reason for not using panels made for 12 v systems?
The Hqst panels I linked to are very good little panels that will easily maintain your batteries with a standard charge controller without the need for the expense for the boost charge controller.

[john61ct]

Forget boost.

Get panels with VoC over 21V, higher is better up to 40V or so, ~65V max. If you really need to, wire in series to get there, one string per same side of the boat.

If under 240W per side, a Victron SmartSolar 75/15 per side, maybe $120

[daletournier]

Originally Posted by john61ct

It takes as long as it takes, how long we **think** it "should" take is not relevant.

My main point was that we have no direct control over when the CC/CV transition takes place. That is up to a mix of objective factors, including bank chemistry's CAR, SoC, resistance, voltage and amps.

In getting a large bank from say 50% to true 100%, increasing the amp rate has relatively little impact on the total time it takes.

It will only be less than 4-5 hours if it is a small bank and very shallowly discharged.

Same to a large degree going from FLA to AGM, maybe save 30-40 minutes.

If Bulk/CC is finished in under an hour, then the remaining hours by definition are spent in Absorb/CV.

Absorb will be much shorter if getting to the transition takes hours, as is the case with low charge rates, say 80A for a 600AH bank.

I apologize if I've already linked within this thread, to this excellent and detailed report by Maine Sail showing multiple examples at different charge current rates.

https://marinehowto.com/how-fast-can...ry-be-charged/

Well worth reading in detail, not just for noobs.

OK, this is what I was trying to say earlier but wasn't able to communicate it like you just have John, you pen your understanding much better than I do or can.

[noelex 77]

Originally Posted by john61ct

If Bulk/CC is finished in under an hour, then the remaining hours by definition are spent in Absorb/CV.
.

This is not the correct definition of absorption time. The absorption time should only be counted when the batteries are at the absorption voltage.

The absorption stage is a constant voltage stage.

In solar installations when the bulk phase is finished and the battery has reached the absorption voltage, there will be times of decreased solar output from shadows and times of increased load where the absorption voltage is not maintained.

With solar charging if the absorption voltage is first reached after one hour it is unlikely that all the rest of the charging time will be at the absorption voltage. Solar charging is not that constant. Certainly it is incorrect to think this will always be the case.

The absorption phase is not just the time after the absorption voltage is first reached, but the time when the absorption voltage is maintained.

This is not just an academic point but the whole principle of how most solar charging algorithms work. The correct definition for absorption time has a reasonable correlation with the SOC. The total time after the absorption voltage is first reached has a very poor correlation with the SOC.