How to Trickle Charge?

[grizzfan]

I recently replaced my two old Interstate Lead-Acid batteries with two Duracell AGMs. I have read that the AGMs can deteriorate rapidly by sitting around all Winter. And believe me in Montana we have Winter big time.

I think the solution is to remove them and store at home with a trickle charger. BUT, being electricity-challenged I can't figure how to hook two batteries up with one trickle charger.

Could anybody out there bring me into the 19th century?! I also need to buy a trickle charger, so recommendations would be swell.

Thanks,

Tom

[rwest]

I think you would be better off with two trickle chargers as each battery will have its own state of charge and by combining them, the charger would likely see an average of the two and not charge optimally.

Just a thought, no knowledge of this particular situation.

To charge two at a time put them in parallel to keep the voltage the same you connect positive to positive and negative to negative. In series you would double the voltage.

[dannobee]

And if you're buying a new charger anyway, you should get one that has an AGM charging option.

[Evans, Marv]

^^^^^^ rwest. This. I sort of speak from experience. I have an F350 diesel with dual batteries. I always keep it on a charger since I don't use it a lot. I used to keep the charger on the same battery and found out most of the charge seems to go to the battery it's connected to. I had to replace batteries when one went dead. I replaced both because I didn't want to mix old and new, but for the old batteries, the one I kept the charger on was always charged. I found out after I started having starting problems the other battery was almost dead and wouldn't hold a charge. I think I solved the problem by switching the charge back & forth weekly or more.

[rwest]

Originally Posted by Evans, Marv

^^^^^^ rwest. This. I sort of speak from experience. I have an F350 diesel with dual batteries. I always keep it on a charger since I don't use it a lot. I used to keep the charger on the same battery and found out most of the charge seems to go to the battery it's connected to. I had to replace batteries when one went dead. I replaced both because I didn't want to mix old and new, but for the old batteries, the one I kept the charger on was always charged. I found out after I started having starting problems the other battery was almost dead and wouldn't hold a charge. I think I solved the problem by switching the charge back & forth weekly or more.

Appears like they make multi battery chargers- quick google search found this site- I have no experience with them.

https://www.impactbattery.com/battery-chargers/multi-bank/2-bank-battery-chargers/

[Cajundaddy]

Get a smart "battery maintainer" that is rated for AGM for each battery and leave them on all winter. Using the right maintainer will nearly double the life of your AGM batteries vs a generic "dumb" trickle charger that does not sense charging state or refresh the cells.

This is a good one:
https://www.amazon.com/NOCO-G1100-Advanced-Battery-Maintainer/dp/B004LX3AXQ/ref=asc_df_B004LX3AXQ/?tag=hyprod-20&linkCode=df0&hvadid=312094794461&hvpos=1o6&hvnetw=g&hvrand=12412645267145761732&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031217&hvtargid=pla-383396610363&psc=1&tag=&ref=&adgrpid=62497261819&hvpone=&hvptwo=&hvadid=312094794461&hvpos=1o6&hvnetw=g&hvrand=12412645267145761732&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031217&hvtargid=pla-383396610363

Or this:
https://www.amazon.com/Battery-Tender-021-0123-Junior-Charger/dp/B000CITK8S/ref=sr_1_33_sspa?keywords=battery+maintainer&qid=1569174252&s=automotive&sr=1-33-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUExVFk3Q0pUMVQ4U0NRJ mVuY3J5cHRlZElkPUEwODA3NDYwMzhPVkowVEpLVTcyMiZlbmN yeXB0ZWRBZElkPUEwODI0MzUzMUU1OFZVV0hKOElVUCZ3aWRnZ XROYW1lPXNwX2J0ZiZhY3Rpb249Y2xpY2tSZWRpcmVjdCZkb05 vdExvZ0NsaWNrPXRydWU=

[grizzfan]

Thanks folks. I presume I should get a one-amp tender or less, correct?

Tom

[wareaglescott]

Can someone explain to me why you would have 2 batteries please?

[Cajundaddy]

Originally Posted by grizzfan

Thanks folks. I presume I should get a one-amp tender or less, correct?

Tom

Not necessarily. Any amperage smart battery maintainer is fine as long as they "float" when the battery is 100% to avoid overcharging. Higher amperage will charge a low battery faster but they also cost more. Get what you need.

[sugarwood]

Originally Posted by Cajundaddy

Get a smart "battery maintainer" that is rated for AGM for each battery and leave them on all winter. Using the right maintainer will nearly double the life of your AGM batteries vs a generic "dumb" trickle charger that does not sense charging state or refresh the cells.

This is a good one:
https://www.amazon.com/NOCO-G1100-Advanced-Battery-Maintainer/dp/B004LX3AXQ/ref=asc_df_B004LX3AXQ/?tag=hyprod-20&linkCode=df0&hvadid=312094794461&hvpos=1o6&hvnetw=g&hvrand=12412645267145761732&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031217&hvtargid=pla-383396610363&psc=1&tag=&ref=&adgrpid=62497261819&hvpone=&hvptwo=&hvadid=312094794461&hvpos=1o6&hvnetw=g&hvrand=12412645267145761732&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9031217&hvtargid=pla-383396610363

Thanks for the link.
I drive year round, but sometimes need to wait a few weeks for rain to wash the roads in winter.
I need to get one of these.
I like the NOCO since it's got a quick disconnect eyelet connectors and AGM option.

[Brian Cameron]

I got this one a few years back, it has a desulfation feature to recover batteries damaged by repeated excessive deep discharges. Restored two Bluetop deep discharge AGM trailer batteries which my other so-called intelligent charger had given up for dead. Several other regular car batteries salvaged as well, got 2-3 years more life out of them after a few recharge/recovery cycles. If this charger won’t bring your battery back, it’s time to replace it. Also works great as a maintainer for my 993 and wife’s SC during the 6 month canadian winter.

https://www.amazon.com/OptiMATE-Ampmatic-TM-181-Battery-charger-tester-maintainer/dp/B003UANXCE/ref=sr_1_2?keywords=Optimate&qid=1569198988&s=gateway&sr=8-2

[Ctopher]

I would suggest looking toward CTEK. They have various models, of which I use the MUS 4.3 to maintain all my cars. Get yourself some comfort connects for the batteries for quick and easy connect/disconnect. I would just consider one charger and rotate every month or so if you didn’t want to spend the $$. But make sure to leave it for at least 10days for it to do maintenance and keep it fully charged. Additionally they have features for various types of batteries including AGM, you don’t have to worry about overcharging and something to consider, all the major manufacturers that sell high-end/exotic cars offer these chargers as accessories which is more reason to consider one.

https://smartercharger.com


CTopher

[grizzfan]

Originally Posted by wareaglescott

Can someone explain to me why you would have 2 batteries please?

The older Porsches came with two battery boxes, one on each side as you probably know. Porsche did that on purpose for balance reasons I've read. Mine is a 1973 so qualifies as 'older'.

The PO used only one battery on the driver's side with the hot cable on the passenger side wrapped in a plastic bag. Something about that looked a little "Joe Magee" to me so I bought two Interstates designed for the 911. They've served well for 5+ years but one was dead, the other sick. So got some AGMs. Just trying to stay somewhat "original".

Hope that helps.

Tom

[Evans, Marv]

Originally Posted by rwest

Appears like they make multi battery chargers- quick google search found this site- I have no experience with them.

https://www.impactbattery.com/battery-chargers/multi-bank/2-bank-battery-chargers/

I'm not an electronic expert, but I'm not certain about charging two batteries independently at the same time on the same circuit.

[47silver]

i use the harbor freight floats but they are no to be used on an agm battery.

[T77911S]

i maintain a 480v 40 battery UPS at work.
40 batteries on one charger.

I think you want a float charger, not trickle.

[Trackrash]

Perhaps a little off topic, but.

OK, so what is the advantage, if there is one, of an AGM battery?

Are they compatible with the ancient charging circuits on our air cooled cars?

[Bob Kontak]

Originally Posted by Trackrash

OK, so what is the advantage, if there is one, of an AGM battery?

Are they compatible with the ancient charging circuits on our air cooled cars?

What are the advantages of the AGM battery? AGM batteries have a very low internal resistance, are capable to deliver high currents on demand and offer relative long service life, even when deep-cycled. AGM is maintenance free, provides good electrical reliability and is lighter than the flooded lead-acid type. It stands up well to low temperatures and has a low self-discharge. The leading advantages are a charge that is up to five times faster than the flooded version, and the ability to deep cycle. AGM offers a depth-of-discharge of 80 percent; the flooded, on the other hand, is specified at 50 percent DoD to attain the same cycle life.

https://www.intercel.eu/questions-and-answers/advantages-agm-batteries/

I don't understand the deep cycle thing. My mental picture is deep cycle is for golf carts and house batteries in an RV. Is that ok for an old 911? Did not answer your question but worthy of discussion. Someone will know.

[spuggy]

Originally Posted by Trackrash

Perhaps a little off topic, but.

OK, so what is the advantage, if there is one, of an AGM battery?

Are they compatible with the ancient charging circuits on our air cooled cars?

An AGM battery is just a lead-acid battery and should require pretty much zero special treatment over the more conventional type. No mods for the charging circuit, no fancy chargers etc.

Difference is that there's zero free acid in the form of liquid; AGM == "Absorbed Glass Mat"; the acid is in the form of a jelly. It is absorbed into a glass mat.

They're sealed - no vent. Think UPS battery. Mount them upside down or on their side if you like.

A completely different topic is lithium-based batteries; these are also compatible with the charging circuit on your car too (wouldn't be much use otherwise), but these do require a specialized charger - preferably, one with a proprietary interface that allows the charger to monitor and/or condition each cell individually. This will maximize the life of the battery.

The advantages of these include incredible weight savings (to both the car and your wallet), tiny - and the charged battery also has an very long shelf life without recharging necessary - if there's no parasitic draw on the car.

[ryans65]

This is misinformation, an AGM battery indeed needs a special charger as they prefer a lower float voltage over a flooded battery among other things.

If anyone wants good info regarding flooded vs. AGM batteries and not just people basing their knowledge off of one battery pamphlet they read at Sears Auto Center 20 years ago just read some articles from any RV or Marine watercraft publication. Your average RV'er or marine enthusiast is generally a battery expert by necessity where battery banks and necessary equipment can be measured in the thousands of dollars vs. the sub $200~ we are discussing here.

Originally Posted by spuggy

An AGM battery is just a lead-acid battery and should require pretty much zero special treatment over the more conventional type. No mods for the charging circuit, no fancy chargers etc.

Difference is that there's zero free acid in the form of liquid; AGM == "Absorbed Glass Mat"; the acid is in the form of a jelly. It is absorbed into a glass mat.

They're sealed - no vent. Think UPS battery. Mount them upside down or on their side if you like.

A completely different topic is lithium-based batteries; these are also compatible with the charging circuit on your car too (wouldn't be much use otherwise), but these do require a specialized charger - preferably, one with a proprietary interface that allows the charger to monitor and/or condition each cell individually. This will maximize the life of the battery.

The advantages of these include incredible weight savings (to both the car and your wallet), tiny - and the charged battery also has an very long shelf life without recharging necessary - if there's no parasitic draw on the car.