Here are some money saving ideas on those Walmart batteries.

1) I currently have one of those $5 harbor freight trickle chargers on my blue 300D. Mostly because that one sits a lot in my garage waiting. I let that battery discharge a couple of times over the pandemic and I think I diminished its starting output. Yep I’m an idiot. ETA - there have been several revisions of this charger over the last ten years. The early ones were awful - they’d burn out or over voltage the battery. I have a two year old one (recent design) now and it pulses the current once a second with a safe voltage and duty cycle. It works well.

In my old garage I had those cheap 12V 1A wall adapters wired from the ceiling using ikea lamp timers ($1.99 ea) to turn on two hours a day. I used those socket adapters on the lamps to T off the power from the bulb sockets. They were 12v wall adapters left over from obsolete internet routers that I discarded. I used quick connect recharging plugs from toy cars (also cheap) and made them all the same so every space in my garage had a charger to plug into when I parked a car or motorcycle. Batteries lasted forever because I never let them discharge.

2) I got a pile of 12”x12” solar panels from a friend who took some junk apart. These are the kind of panels you see on a lamppost powering a remote computer or camera with a wireless station. They usually cost $20 on Amazon. 12V 1A. I have one of these in my old pickup bed wired to my battery where I cannot get a wire out to a normal charger. I put a diode in-line to keep the battery from discharging in the night and a fuse to keep me out of trouble. It keeps the battery topped up. It may have a little too much current even though it only runs in daylight and I park in the shade of a hedge. I need to fill water in my battery every 18 months. If you park outside these are great.


3) which reminds me most of these cheap batteries have caps. Even though they don’t look like they can be opened there is usually a way to pry off the caps and add some distilled water. They do boil off over time. This helps keep an old battery young.

4). I have not experimented with desulfators. There are a bunch of diy circuits online that are made with household junk that look promising. The welder idea mentioned here is also interesting.

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79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

You hear so much on batteries at times. Many swear by trickle charging. The explanation is a fully charged battery does not sulfate. Yet as mentioned it does not work for everyone and it could easily be the wrong form of trickle charging.

Not a friend of mine. He loses batteries frequently using trickle charging. Having about ten cars in his collection it really bothers him. As mentioned he probably has some kind of issue with his trickle chargers. The majority using them tend to like them and that is important.

My trust in them is not that great. I would put an in line fuse in the primary circuit of each one. They draw very little current. They could smoke easily and not take out the house breaker. Think it would have to be a glass fuse to get an amperage rating low enough. Possibly the best solution for the average guy.

I am not sure but no sulphation is indicated at full charge. Less than that may be why some are having poor results. Do not know. So perhaps should read 12.75 on the battery. Remember that a diode in line drops the voltage by .7 volts. anothe thing to remember as the battery nears the full charge on the battery. A 12 volt adapter will be at a substantial higher output voltage. As they are only regulated by load. So you kind of have to do your homework. You can pick up expensive power supplies that you set the regulated voltage and current out manually. At yard sales once in awhile.

One of them can handle at least five batteries with no issues. Most at yard sales will just be 12 volts and I do not think that is enough. My long winded approch is really check your setup and read what you can access.

You can buy a regulated 12 volt supply from China for about 4,00 delivered on ebay. There is a trimmer in them for manufacturing tollerence. They should be adjustable enough in range up to the best output voltage. Plus they have a lot of built in safety features. No diode should be required for them. A quick check will verify that. I guess batteries have just gotten expensive enough to be worth the effort.

I bid and purchased a brand new Chinese plasma cutter. That uses cheap consumables yesterday. For 90.00 American shipping included. For far less than the cost of a new battery these days. Will handle 3/8 thick decently and less. What you save on battery replacements can buy some toys still.

Lots of good info and thinking here .

__________________
-Nate
1982 240D 408,XXX miles
Ignorance is the mother of suspicion and fear is the father

I did then what I knew how to do ~ now that I know better I do better

Only problem with batteries sold by chains is they buy on price rather than quality. Built to sell basically at highest margins over other considerations. May drive suppliers to build as cheap as possible. Far too many things are built to sell now rather than having much in quality considerations.

Yet that is the way the consumer driven economy works. If too many people did things a lot like I do. I do not know what would happen to the economy.

I call myself cheap but we do give money to charity each year. So it may be a little more complex in reality. I do own a very expensive plasma cutter but the cost of consumables for that brand is now rediculous. At times I almost wish I did not still have a long term memory.

So true. I glossed over a lot details. I do take a bunch of measurements with my multimeter to check charging under load. Not all 12v wall adapters are appropriate. I pick and choose the ones I want with appropriate voltages and current sourcing. Then I fine tune using cheap lamp timers to cycle the power 1-2hours a day.

But yes Barry, these things need to be validated before hooking anything up.

The Harbor Freight float chargers have had a colorful history. They have had several different circuits inside. Some were top off and float. The most recent one I bought just turns on and off every other second. It seems to keep my 300D from discharging.

But really I need to look into why it slowly discharges. Maybe my clock has a bad capacitor or my dome lights have leaky capacitors. A new project for when I have time.

__________________
79 300TD “Old Smokey” AKA “The Mistake” (SOLD)
82 240D stick shift 335k miles (SOLD)
82 300SD 300k miles
85 300D Turbodiesel 170k miles

There are lots of types of “trickle” chargers. Some are very simple dumb units with just a transformer and some sort of simple conversion circuit. Others have much more smarts. So you can’t lump all chargers together.

The dumb ones can boil off electrolyte and damage a battery of left on too long. While fine to bring a depleted battery back, they aren’t good for long term or maintenance charging. Others are smart and will revert to a temperature compensated float charge and/or shut off and monitor the voltage, topping off when needed because the battery dropped below the 100% threshold.

Generally a battery is charged in a constant current/constant voltage charge. This means that the charger will put out its max rated current until the voltage gets to some value, then keeps the voltage at that amount and lets the current exponentially decay. End of charge is when the current at that voltage drops to some minute fraction of the initial. Some chargers have more steps, some reduce current as they approach the maximum voltage.

I’ve kept cars on float chargers for years when using smart ones that are thermally compensated. Not harbor freight types. Ctek, NOCO, battery minder, battery tender, and a few others are good. The rest are unknown. Some cheap Chinese ones coming on the market are decent knockoffs and work with a decent rudimentary charge approach.

In sum, smart, temperature compensated float chargers work well and can extend battery life significantly.

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)

Out of personal curiosity. Anyone have any knowledge of the holding or storage voltage on a battery on a good trickle charger? Someone must have measured it.

I also remember it was a big issue at one time to clean the tops of batteries as that could present a leakage path. For the charge in the battery. Think it was a paste of baking soda and water. used. It also neutralised any battery acid residue..

The Canadian penny long discontinued was made of copper. Put a couple of them on top of a battery and they develop corrosion on them. Since they eventually had no spending value and only added weight to your pocket. I started dumping them into a large glass bottle. So I still have a good supply of them.

Float voltage is dependent upon temperature and battery type (AGM vs flooded).

Some smart chargers actually keep the batteries on a float voltage level, some turn off and only push more current in when the battery drops to a threshold level (say, 99.9% charged). After the charge the capacitance surface charge keeps it high for a good long time (dependent upon parasitics and battery health).

I have an ongoing battery charger test on BITOG:

https://bobistheoilguy.com/forums/threads/battery-charger-testing-results.336207/

Not all batteries are well made, some have had gas seepage issues that resulted in corrosion. Some splash around and leak sulfuric acid, etc. The penny trick was/is a good one to deal with that. Key is to not overtighten the battery lead connectors, which often damages the seals around the terminals.

Cleaning the battery with pledge also helps.

__________________
Current Diesels:
1981 240D (73K)
1982 300CD (169k)
1985 190D (169k)
1991 350SD (113k)
1991 350SD (206k)
1991 300D (228k)
1993 300SD (291k)
1993 300D 2.5T (338k)
1996 Dodge Ram CTD (442k)
1996 Dodge Ram CTD (265k)

Past Diesels:
1983 300D (228K)
1985 300D (233K)