Solar Trickle Charger for House AGM Battery

[posplayr]

Originally Posted by BCam

Amazon has quite a few, here's one example:

https://www.amazon.com/Sunway-Solar-...NsaWNrPXRydWU=

However, I think you'll be much happier with 20W - 50W, hard-wired. Here's a link to a reasonably priced ($49.99) 20W kit that includes a controller for not much more money:

https://www.amazon.com/TP-solar-Mono...0301636&sr=8-4

And a 50W kit for $89.99:

https://www.amazon.com/SOLPERK-Monoc...0302108&sr=8-3

I agree with what you are saying. I think the OP just has to come to grips with a full 1 amp continuous load needing over 50 watts of solar power to maintain the battery.

I'm not sure what is drawing that power, but I would look at reducing it. A typical quiescent load in the 25-50 mA level is much more normal.

[boywonder]

Originally Posted by posplayr

However, the question seems to be focused on "Solar trickle Charging" . Now it takes in the best case 1*13.0*1.15*24/10= 36 watts with 10 sun hours.

Aha! I missed the "Solar" part......

[boywonder]

Originally Posted by posplayr

Figure the minimum charge rate is C/10 where C is the amp hour rating of your battery setup.

Originally Posted by posplayr

Well you can assume what you want but that is not where C/10 comes from. It is a generally accepted charging rate that can be used for extended periods or safely charge almost any battery type overnight.

..Either I'm confused or the word "minimum" perhaps should be "maximum" above.....

[Scalf77]

I would recommend that the OP put a disconnect switch on the battery to eliminate any discharge via Propane and CO sensors while stowed for any length of time. I would not just put a switch on the sensor power, as this would bring the possibility of forgetting to turn on the switch, thus rendering the sensors useless. It would be good to purchase a battery monitor also.

Not sure what the OP has for a charging procedure. The fact that you don't have solar, means alternator or shore charger. I would recommend plugging in shore and using a shore power charger for this activity. It would be imperative to fully charge the battery, then disconnect for storage. The self discharge rate for a Lifeline AGM is 1% to 3% per month.



-greg

[posplayr]

Originally Posted by boywonder

..Either I'm confused or the word "minimum" perhaps should be "maximum" above.....

You are taking two different statements out of context.

The first is to try and establish a minimum charging rate for a dead battery. C/10 is a very safe charging rate. You can go faster but you will need a more sophisticated multi-phase charger to push the battery SOC at a faster rate.

So in the context of recharging dead batteries, I figured C/10 was the minimum you would want.

In the case of the second quote, I'm simply stating that C/10 is a safe charging rate and can be left on for extended periods. This is just a restatement of the same.

Here is a little discussion of battery chargers:

http://www.chargingchargers.com/tutorials/charging.html

Most battery manufacturers recommend sizing the charger at about 25% of the battery capacity (ah = amp hour capacity). Thus, a 100 ah battery would take about a 25 amp charger (or less). Larger chargers may be used to decrease charge time, but may decrease battery life. Smaller chargers are fine for long term floating, e.g. a 1 or 2 amp "smart charger" can be used for battery maintenance between higher amp cycle use. Some batteries specify 10% of capacity (.1 X C) as the charge rate, and while this doesn't hurt anything, a good microprocessor charger of the appropriate charge profile should be fine up to the 25% rate. You talk to different engineers, even at the same company, you get different answers.

Here you see 0.25C being recommended when you have a microprocessor charger, and a slower more conservative 0.1C (C/10) being discussed. Here C/10 is the lower and the minimum I would suggest. 1-2 amps trickle is only for maintenance not increasing SOC.

So when I say minimum I mean it in the sense that if you want your battery to recover from being discharged. C/10 is the minimum I would be looking for.

With C/10 you have a slow Bulk mode and then automatically transition to a C/10 absorption mode and never go into Float. It is not necessary because at C/10 and 14.5V you are essentially 95% of SOC. This is essentially what will happen with the vehicles charging system.

When the SOC is low then the voltage may be down 13.25-13.75V and as SOC comes up so does the battery voltage. You reach a steady state at the 14.5V level C/10

[posplayr]

Originally Posted by Scalf77

I would recommend that the OP put a disconnect switch on the battery to eliminate any discharge via Propane and CO sensors while stowed for any length of time. I would not just put a switch on the sensor power, as this would bring the possibility of forgetting to turn on the switch, thus rendering the sensors useless. It would be good to purchase a battery monitor also.

Not sure what the OP has for a charging procedure. The fact that you don't have solar, means alternator or shore charger. I would recommend plugging in shore and using a shore power charger for this activity. It would be imperative to fully charge the battery, then disconnect for storage. The self discharge rate for a Lifeline AGM is 1% to 3% per month.



-greg

Agree on all points

[boywonder]

Originally Posted by posplayr

The first is to try and establish a minimum charging rate for a dead battery. C/10 is a very safe charging rate. You can go faster but you will need a more sophisticated multi-phase charger to push the battery SOC at a faster rate.

So in the context of recharging dead batteries, I figured C/10 was the minimum you would want.

In the case of the second quote, I'm simply stating that C/10 is a safe charging rate and can be left on for extended periods. This is just a restatement of the same.

I hope for the sake of future readers of this thread that we can both agree that charging at a rate of less than C/10 is also safe.....just takes longer...

[SCMatthew]

Thank you to all for the great points. I appreciate the time to put this together for me.
I usually park on the street-- so it is tough to keep shore power plugged in.
I think I need to bite the bullet and just install solar!
Thanks again.
Matt

[posplayr]

Originally Posted by boywonder

I hope for the sake of future readers of this thread that we can both agree that charging at a rate of less than C/10 is also safe.....just takes longer...

As Scalf77 and I both suggested, you want to get the battery charged and let it rest as opposed to slow cooking it constantly.

Charging rates less than C/10 are moving toward that slippery slope. In this context, a "safe" rate is one that does not overcharge.

With solar it goes off daily (at night).

As a side example, there are many motorcycle LA, SLA and AGM batteries that are worse for the wear of being on trickle charges all winter.

A mechanical timer to cycle completely off/on a typical charger is "safer" in the sense it is less likely to ruin your battery. None of these 120VAC trickle chargers seem to have this feature (they go into float) so guys I know use some type of a dinural timer.

I bought a cute little battery charger for my 6Amp-Hr DRZ AGM (1 Amp rating). I don't have it on a data logger, but it seems to gain voltage to about 13.3-13.6V and then drop back to 12.9 when fully charged (i.e. float). The AGM battery seems to drain fairly quickly and In about 3-5 days it will be around 12.5V with the charger off and I connect the charger again. I have not investigated what the drain is. i would hope it is less than 25 mA but TWT when i get a chance to investigate.

https://www.amazon.com/-/es/gp/produ...?ie=UTF8&psc=1

https://www.amazon.com/-/es/gp/produ...?ie=UTF8&psc=1

[Scalf77]

Originally Posted by SCMatthew

Thank you to all for the great points. I appreciate the time to put this together for me.
I usually park on the street-- so it is tough to keep shore power plugged in.
I think I need to bite the bullet and just install solar!
Thanks again.
Matt

Matt, As long as you have access to the shore power to plug in and complete a charger cycle (bulk, absorption, float), you could then throw the disconnect switch and leave it parked on the street, no issues. The important thing for putting it into storage is to make sure that it is fully charged before hand. In fact it is important that you always bring it back to full charge as soon as possible.

Obviously if you could keep it plugged in, it would remain on float, or go through some storage algorithm. If you can't do that then the disconnect would be my next preferred method.

Third, would be to rely on solar, which should do the job just fine, until you have those moments when it doesn't.

-greg