[twistedge]

I picked up a Nautilus 12V 70Ah Deep Cycle Marine battery.

Should I also be looking for a Deep Cycle battery charger or is it fine to use an RC charger that supports PB batteries?

I have the Hyperion Duo 3 and the Hitec X4.

The Hyperion allows PB charging with a setting for the maximum Charge Volts before it moves into Float Voltage where it maintains those Charge Volts indefinitely (depending on timer settings)

The Hitec uses Capacity Cutoff and shuts off the charger when the limit is reached. This seems like a more complicated process than just setting the final voltage.

I think I'll use the Hyperion and set the cutoff at 14.4V. Then, I think the Deep Cycle battery should read 12.6V after it comes off the charger and sits for a while... but I'm not entirely sure.

Thoughts?

[kip51035]

Lead acid 12V batteries should read Between 13.8V to 14.6V when they reach full charge while still on charge. When you take it off charge they quickly drop to 12.5V. Pick up from The Source a 12v Power supply that puts out 1/3rd to 1/2 an amp. You will find that the maximum no load voltage is a little over 16V. You know those little black cubes that plug in the wall. I used one for years until the diodes went on it.

[twistedge]

Thanks Cliff... A slow charge would certainly be safe, but I'm not sure that it would ever completely charge at 0.5A.

The Smart deep cycle chargers all seem to deliver high initial charge rates, so I've decided to test the following PB Settings while monitoring the battery:

Charge Rate: 7A
Charge Volts: 14.4
Floating Voltage: 13.4
Charge Method: CC\CV

The CC\CV method is non-linear, but I don't know what the curves are. It's probably not critical since it will start high (7A) and finish low (<1A) as the battery approaches the preset 14.4V. This should nicely mirror a standard Bulk/Absorption charging process.

I'll also assume the Charger will use low current (<1A) to maintain the preset floating voltage of 13.4V. I'll just need to watch and verify.

When it's all done I can let the battery sit and check the at-rest voltage. If it's around 12.6V I'll know it's good. If it's high or low I guess I can adjust the two charging voltages accordingly.

Assuming 90% efficiency, I'm looking at 8-9 hours to charge this battery (when 75% depleted)... which sounds about right.

We'll see what happens.

[thanasi]

Charge your battery like any other lead acid battery. Deep cycle has thicker plates that can handle the abuse.
So yes your charger will be fine but probably best bet to get a on board charger so you can plug in and just walk away
I guess it depend what your set up will be like
Good luck Ed

[FD av8r]

my favorite charger is a Deltran Battery tender. Its only 1.25A, but it keeps my RV and vehicle batts up to charge safely and long term. Google them, lots of retailers in Canada.

Daryll

[kip51035]

70 AH lead acid battery is a pretty small battery and over charging it could permanently damage the battery.

[twistedge]

Hey Cliff,

I'm not sure how the size of the battery relates to the charging process, but there could be something I'm missing. In the end, I may actually need a specialized charger, but I figure it won't hurt me to understand why.

The most important thing I've read recently is that charging a flooded cell battery too slowly will do more harm than good. A very slow charge rate does not generate gas bubbles which leads to an imbalance in the electrolyte (a poor mix of acid and water, where acid is heavier). A small bit of gassing is actually critical to creating small bubbles to keep the electrolyte mixed.

I finally dug up some specs from the manufacturer (PDF Link).

It bases the charge rate for a wet Deep Cycle battery on its C20 Rating.

C20 = 70Ah
70 over 20 = 3.5A (i.e. what it can deliver for 20 hours)
10 x 3.5 = 35A (The maximum charge rate)

Starting at 7A is probably on the low side
Stopping at 14.4V is also cautious (recommended is 14.7-14.9V)

There's a lot of conflicting information out there.. but this what I've decided to go with... Again, I guess we'll see.

[kip51035]

The battery in my lawnmower is 200 AH battery, I charge it at 4 amps. If I charged it at 35 amps the square battery would turn round within a few minutes and explode within half an hour. I SEEN IT HAPPEN!!! Inside that battery is sulphuric acid and it will dissolve just about anything. The battery in my car is 800 AH. Good luck and stand back.

[twistedge]

What brand battery do you have in your lawnmower? It looks like a healthy 200Ah flooded deep cycle battery should be able to handle an initial charge rate of 35A. Even the most conservative manufacturers require a minimum of 3-5% of the C20 rating to begin charging a depleted battery (which would be at least 6-10 amps for 200Ah)

Granted.. the charger must scale down the current as the battery approaches capacity or it will cause damage (i.e. no linear charging)

In general, I'm reading a lot of threads that recommend super low charging rates, but I'm also seeing a lot of manufacturers recommending 3 stage chargers with high start rates. It's tricky to sort through, but I'm still leaning towards what manufacturer says.

I am beginning to wonder if excessive charging at well below the minimums might actually be creating the very issues we're trying to avoid. It seems like a slow charge is fine if there are also some fast/normal charge cycles to clean the plates and equalize. (And avoid the heavy sulfation effects of a large electrolyte imbalance).

A car battery is an interesting example. Alternators are capable of over 100 amps and are used as smart chargers (providing as much current as needed to charge and maintain the battery). Headlights alone can be a steady draw of 15-20A and they're powered entirely from the battery. I wonder what the recharge rate is to ensure the battery stays fully charged.

[stegl]

True deep cycle batteries should be charged at a lower rate than starting batteries as the plates have a finer plate design to handle low discharge rates over a longer period. Starting batteries are designed with a much courser plate design to produce large amounts of current in a short time plus handle a quicker charge rate. Most hobby multi use Chargers will work well charging lead acid batteries as the current auto reduces as the charged voltage increases but I would not readjust the cutoff voltage , just go with the default settings or the manual. Lots of good charging information from manufacturers out there so just google it .