Adding Water to Lead Acid Batteries

[Kevin H]

I put together a battery bank of six Sam's golf cart batteries.  I installed a single point watering system.  When is the optimum time to add water:  at the end of bulk charge and beginning of absorb or at the end of absorb and the beginning of float?   Want to do it as perfectly as possible.

Thanks!

[oldjohnt]

Kevin, I prefer to add distilled water when the battery is at rest and stabilized (like sat for 30 or so minutes with no charger running) and not under load or ESPECIALLY being charged. I also have one of those battery watering systems where you stick the tube down into a bottle of distilled water and pump the bulb a few times. I check mine about once a month or so subject to how hard I'm using them.

I'm sure others may have different opinions, we will see, but that's the way I like to do it UNDER REST AND STABILIZED..........

  John T

[Kevin H]

Thanks John.  I've read that the charging process causes heat and thus the electrolyte to expand.  If one tops off when the temps are cool, the heating causes expansion and possibly over-flow.

So your suggestion is to:   charge the batteries, when they are topped off (float) remove any loads (I have a disconnect switch) and let them rest for 30 or more minutes and THEN add the water via the bulb.   Is that correct?

Thanks again for your reply.

[Sehc]

If the batteries are filled to the proper level, there will be enough head space and no overflow. I always fill before charging so the electrolyte can mix with the water. But my battery bank is rarely below 20% of full charge. And never more than 1/2 inch low on water, usually 1/4 inch.

[Kevin H]

Good info, Sehc.  These have not gotten below 80%.   The single point watering system will keep them topped off but I do not know how low they will get.  I plan to check/add water once per month.  We are not heavy power users.  This is in a Sprinter van.  All lights are LED.  The system is completely independent from the chassis.  Every circuit is hard wired pos and neg back to the fuse box.  Cables connecting the batteries in series/parallel are 0000.  Other than my CPAP, there really is not much draw.  The inverter/charger uses some power but negligible.  Wife uses an Instant Pot for cooking (very low power draw for short period) and coffee pot.

Thanks for  your feedback.

[oldjohnt]

9 hours ago, Kevin H said:

Thanks John.  So your suggestion is to:   charge the batteries, when they are topped off (float) remove any loads (I have a disconnect switch) and let them rest for 30 or more minutes and THEN add the water via the bulb.   Is that correct?

Thanks again for your reply.

Kevin, being under a light load isn't so bad BUT when under a heavy charge there's some bubbling and outgassing and expansion happening so I just prefer NOT to check or add water at that time. Its easy to be off the charger and wait some time and then add water which is my own personal preference BUT SURE ADDING WATER AT ANY TIME WILL STILL "WORK".

I just attended Escapees Club 58th Escapade where I learned about one particular brand of water fill systems. They claimed their product had float type fill valves that shut down (no more water could be added) when there was something like (no warranty I may not have remembered their numbers) 1/8 inch between water and battery top vent area. They showed diagrams of proper water levels above the plates but still allowing enough free top air space to allow for expansion and bubbling and outgassing so as NOT to overflow out the top... IE they claimed (and I sure agree) too much water is a bad thing.......... 

As I said others may have different preferences and sure adding water isn't rocket science and can be done at most any time, but its just my preference and practice to be off charge,,, let the gas and levels and state of charge settle down and stabilize with no gassing and bubbling,,,, and the water/acid mixture be well blended   AND THEN TOP OFF WATER IF NEEDED.  If an RV owner believes its actually better to check and/or add water while under a charge that's their own choice, fine by me.

John T

[Sehc]

Yes. If I wasn't clear. As I have easy access to my six GC2's, I can check water level. After a bit, we learn the average use. I started every week, then monthly. Now I check monthly and add water maybe each second time I check. My batteries are not charging while I add water. In fact I disconnect them and do the other maintenance while there. If I had an auto fill system, I would activate it when the batteries were not charging, maybe even with the charger switched off. 

 

[oldjohnt]

8 minutes ago, Sehc said:

 My batteries are not charging while I add water. In fact I disconnect them and do the other maintenance while there. If I had an auto fill system, I would activate it when the batteries were not charging, maybe even with the charger switched off. 

 

  FWIW Looks like were on the "same page"

 John T

[Kirk W]

9 hours ago, Sehc said:

I always fill before charging so the electrolyte can mix with the water.

That is exactly what I was taught many years ago when caring for the batteries used for emergency propulsion on submarines. In the 40 years since I have seen no evidence to show that wrong.

24 minutes ago, Sehc said:

Now I check monthly and add water maybe each second time I check.

I also agree with this. Once you establish a pattern of need you can be pretty confident that they are fine. I have never bothered to isolate the batteries and we didn't on submarines either but they should be in a minimal use condition. Isolating by lifting the negative sure don't hurt. 

[oldjohnt]

45 minutes ago, Kirk Wood said:

That is exactly what I was taught many years ago when caring for the batteries used for emergency propulsion on submarines. In the 40 years since I have seen no evidence to show that wrong

AMEN to that. In 47 consecutive years of RV ownership FWIW I definitely agree that flooded lead acid batteries used in them (I cant speak to submarine batteries, NO experience) be at rest, NOT under charge, THEN ADD WATER THEN TURN THE CHARGER ON. Works for me .....................Nor have I seen any evidence to the contrary...............If any exists I hope others will enlighten us all, I'm never too old to learn

Fun and informative chat, thanks to all

John T

[Optimistic Paranoid]

Well, here's what Trojan has to say on the subject:

"Flooded batteries need water.

More importantly, watering must be done at the right time and in the

right amount or the battery’s performance and longevity suffers.

Water should always be added after fully charging the battery. Prior to

charging, there should be enough water to cover the plates. If the

battery has been discharged (partially or fully), the water level should

also be above the plates. Keeping the water at the correct level after a

full charge will prevent having to worry about the water level at a

different state of charge."

That's from this web page:

https://www.trojanbattery.com/tech-support/battery-maintenance/

[oldjohnt]

2 hours ago, Optimistic Paranoid said:

Well, here's what Trojan has to say on the subject

 

Water should always be added after fully charging the battery.

Thanks for the great info Optimistic. I have Trojan FLA Batteries and my Smart 3/4 Stage Charger eventually full charges them and maintains them in the "Float" mode, so I turn it off,,,,,,,,,,, let the battery rest and stabilize so there's no bubbling, excess outgassing or further expansion,,,,,,,,,,,THEN ADD WATER TO PROPER LEVEL,,,,,,,,,,,then turn the charger back on   SOUNDS LIKE A PLAN..............I'm sure adding water still "works" if everything isn't done EXACTLY this way, but I see no problem doing it as Trojan recommends...

Thanks again for the info

John T

[Kirk W]

Interesting what Trojan has to say and I suspect that I may know the reason why. If you overfill a cell at all, prior to charging the charging will cause the water to heat up and expand, thus running the excess over the top of the cell. On the other hand, if you do not check levels before a heavy charge, then you could charge with some plates not fully covered and damage the battery. In an ideal world, you check the temperature of each cell, measure the electrolyte level and take a specific gravity reading, all before you add water or charge the battery(as we did in subs). In the real world, most of us don't go nearly to that extent. 

In the submarine battery situation, we actually knew the battery state of charge as we monitored it very accurately, 24/7 and we didn't float charge but knew exactly when a battery charge commenced and ended. In most RV batteries the charge/discharge is not nearly so defined for start or finish. I have no idea when my RV battery begins a charge or discharge specifically. Obviously, when we dry camp it is discharging but that is pretty seldom and it then charges when traveling.  If you dry camp a great deal and use solar for recharging you probably have a better feel and if you dry camp a lot and use a generator to recharge, then you could know the battery state at the time of checking levels but for our style of RVing it is unusual to actually know. I check mine monthly, even when sitting still connected to full hookups for several months at a time. At such times the battery is in a floating state nearly all of the time with the only draining periods being a loss of shore power. 

[oldjohnt]

Id guess Trojan has it right, they know a bit about batteries lol. Once a FLA battery is full charged setting there at rest stabilized with no bubbling or outgassing and thermal expansion has subsided, sounds to me like a darn good time to check water levels and at the proper level its above the plates, yet there's still sufficient room (around 1/8 inch if I recall correctly) for expansion WITHOUT any risk of overflow SURE WORKS FOR ME  Trojan Rocks as far as I'm concerned..................That also agrees with what was taught at last weeks Escapees Escapade Seminars MUST BE RIGHT YA THINK ??????????? hope so

GREAT fun and informative chat, a bunch of fine gents here

John T

[Yarome]

Both arguments have pros and cons and really "depends". In an ideal world you would check water levels both before and after charging. That's where a watering system really pays off. A couple pumps now... a couple pumps later.

I understand the "covering your rear" view point with Trojan's recommendation, and there is certainly nothing wrong with that. With imporoper charging you can slightly "cook" you batteries and have a low water level situation after a hard charge. The plates will likely still be wet after charging from bubbling, but a persistent low level water situation while using it under load is going to have an impact on capacity. Running a charge cycle on low water... devastating... so filling after a charge ensures you're good to go on the next charge cycle. Let's face it though... you're running multiple charge cycles over the course of a month so filling after every charge cycle isn't really practical. In the long haul... impact is minimal unless you really "are" going to refill after every charge cycle.

Being the #1 battery killer cause... "after after" will be the biggest "saving grace" in that regard and makes sense that would be Trojan's recommendation... and following their lead... Escapees instructional course to follow suit.

If charge levels are set appropriately, it's really not an issue.

On the flip side... electrolyte is heavier than water. In a sitting battery, you have a higher concentration of electolyte at the bottom of the plates than the tops. Adding water prior to charging "could" futher dilute the electrolyte at the top end further... but during the course of the charge the fluids will be intermixed again. Less impact on capacity life but may impact charge rate and charge saturation (not using the full capacity available). Really only on that particular charge cycle though.

A big HOWEVER, running a charge cycle on low water... again... devastating to capacity.

To note: In a submarine there is a constant low level resonance that keeps batteries "stirred" that isn't always present in an RV that's been parked for a week. 😉 Adding water prior to charging makes more sense.

Kirk's quite right that the avid dry camper and boondocker have much more control over their charge cycles since we know exactly "when" charging is occuring.

Best advice is to know your batteries and charging system. Check water levels more frequently with a new rig, new charger or battery bank and adjust your water level maintanence intervals accordingly.

My opinion? Don't especially matter none. Put it on your monthly maintenance list no matter if that falls before or after a charge cycle... as long as it's not "during"... and you'll be just fine.

[oldjohnt]

Great info Yarome.  WOW This is getting deep and technical GOTTA LOVE IT (for us nerds and sparkies at least lol). Here's yet one more dose of advise and opinion regarding adding water I found at Arcon Batteries and Chargers Website. It appears to agree somewhat with Trojan, but that's mainly for the purpose of avoiding overfill NOT the end of or the whole story Yarome so well discussed IE each has pros and cons !!!! But I'm too lazy to check when not charged (mine don't get there often) as well as when charged LOL. However, it would be possible for me to check and add in a low charge state when dry camping which is early morning BEFORE my solar kicks in and AFTER my CPAP and vent fans or furnace and 120 VAC Inverter powered fridge ran all night IE I still have the option even if I might not exercise it....  

 

http://www.arconequipment.com/article_0599.html

 

Why does my battery overflow occasionally?

It shouldn’t, but it will if it is overfilled.

Keep in mind that the electrolyte level rises as the battery is charged.

It is at its lowest level in the cell when the battery is discharged.

It is common to add water to a battery before it is charged, but care must be taken to ensure that the fill level is appropriate considering this rise in electrolyte height. Batteries differ in the extent of this change in level, so it is difficult to make a blanket recommendation here. If the battery regularly overflows despite reasonable attention to proper level, a two-step process may be followed at those times a battery requires water:

1. Before charging the battery, add just enough water so that a low liquid level is visible.
2. After charging is complete, add enough water to bring the level up to the bottom of the vent opening barrel (usually about ¾ inch below the top of the cell).

The above steps will prevent overflow. Step one ensures that the electrolyte level has not gone too low and exposed the plates to air for the charge cycle. Step two brings the level up to full height at a time (battery fully charged, electrolyte at highest point) when accidental overfilling would not be a problem.

Back to me: Since my batteries are typically maintained at or near 100% SOC by early to mid morning at least  (Solar or smart charger) and its not my practice to let them discharge very much, I'm stickin with my normal maintenance to add water if/as needed when they are pretty much full charged at rest stabilized and not under charge. If the article above is accurate (highest level when charged) that should result in levels that aren't so high overflow will happen, yet hopefully never drop bellow the plates...........BOTH of which are, as Yarome described, BAD !!!

I enjoy the heck out of this techy stuff and I'm never too old to learn THANKS ALL

John T

 

[Kevin H]

Lots of good info here, folks.  So here's what I did:

Charged batteries all the way to float.  Floated for about 12 hours.

Turned off charger/inverter  --  system sat about 4 hours until I got home from work.

Disconnected via disconnect switch

Waited and hour and added water.   Used very little.

Turned disconnect switch back on.

Heading out tomorrow for my weekend!!f

Thanks again, everyone.  As usual, Escapees provides the expertise I am looking for.

--  Kevin

[Kirk W]

Enjoy your trip! 

[oldjohnt]

You did good Kevin, CONGRATULATIONS, we appreciate the feedback...............

Batteries FULL charged then floated 12 hours,,,,,,,,,,,,Four hours to rest and stabilize,,,,,,,,,,,,,,,,,,Then disconnected,,,,,,,,,,,,,,,,,Then wait yet another hour for more rest and stabilization,,,,,,,,,,,,,,,,Then add water,,,,,,,,,,,,,Then back on 

If the Battery web sites or contributions above mean anything at all, that "should" allow for sufficient level to keep electrolyte above the plates yet not overfill .................

John T

[mptjelgin]

10 hours ago, Kevin H said:

Lots of good info here, folks.  So here's what I did:

Charged batteries all the way to float.  Floated for about 12 hours.

Turned off charger/inverter  --  system sat about 4 hours until I got home from work.

Disconnected via disconnect switch

Waited and hour and added water.   Used very little.

Turned disconnect switch back on.

Heading out tomorrow for my weekend!!f

Thanks again, everyone.  As usual, Escapees provides the expertise I am looking for.

--  Kevin

With all due respect:

While this has been an interesting discussion regarding how to make adding water to batteries a time-consuming process, you would have accomplished exactly the same thing by doing what is bolded above. Once the battery is at float there should be no expansion, out-gassing, etc. You can add water right then. The resting, disconnecting, and waiting some more is simply not adding any value to the process. 

The important thing is to check your batteries regularly, add distilled water as needed, and never let the plates become exposed. Everything else is just complicating an otherwise simple process.